That is very exceptional. I've written fuel estimation software for airliners (cargo, fortunately), and the number of rules regarding go-arounds, alternates and holding time resulted in there usually being quite a bit of fuel in the tanks on landing, by design. I've never heard of '6 minutes left' in practice where it wasn't a massive issue and the investigation into how this could have happened will make for interesting reading. A couple of notes: the wind and the time spent on the three go-arounds + what was necessary to get to the alternate may not be the whole story here, that's actually factored in before you even take off.
I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
The context you're missing is that Ryanair have routinely declared fuel emergencies in the past, and it seems an operational tactic - they want to carry less fuel to burn less fuel, and then have to regularly mayday to jump the stack on inbound, saving cash. That's not covered in the article, but you can sure as hell expect the CAA are going to take another look at them and their operations planning.
On this one, they did 3 attempted landings at Prestwick. [Edit: I now see that the third attempt was at EDI] What happened between the first and the second landing that made them think on their second go-around that a third attempt was more likely to succeed than the previous two? Was the wind dying down, or was the captain just feeling a bit braver or stupider? [Edit: I'm still curious as to what information they gathered that landing conditions were significantly different at EDI to make that diversion, given its relatively close and so likely to have similar weather].
Why was their final reserve Manchester when there were literally dozens of closer suitable airports, at least some of which are likely to have had better wind conditions by virtue of lower gusts, or more aligned to runway direction so not dealing with a strong crosswind?
There are many reasons I won't fly Ryanair, but not least because they have been shown over and over again to make reckless planning and operational decisions, and they are fortunate to have not had hull losses as a result. Time is ticking down, variance will catch them one day, and a sad & tragic catastrophe is only a matter of time. People will go to prison as a result, because this pattern of behaviour shows that this isn't "bad luck", it's calculated risk taking with passenger and crew lives to save money.
I hadn't heard about this. They can't be having fun if that's the case, caught in between the treatment of their employer and the customers they pay it forward to (for money).
I fly with them all the time and never have any kind of issue at all. They offer a good deal, ok there’s a couple of obvious dark patterns in their app and way of doing business but they’re hardly unique in that respect. Feels like getting a fast bus between European cities nowadays.
Well that revolver didn't go off the last 5 times I pointed it at my head and pulled the trigger. Surely on the 6th pull we can guarantee the same outcome!
I once had a board member who was also on the board of Ryan Air, and he casually told me a story about when their CEO gave a presentation on adding a credit card -powered interlock on the cabin lavatories. He told them, “They’re my planes and if you have the nerve to shit in them you should have to pay for the cleanup”.
My colleague thought he was portraying the CEO as a cool guy and decisive manager, but I thought the guy sounds like a sociopath.
i heard from an airport employee once that they wanted to keep the airplane started in between flights. This was specifically so they can skip the preflight checks. Thankfully they were not allowed to
Naively as an outsider, this situation seems like everything worked as intended?
On a nominally 2h45m flight, they spent an extra 2 hours in the air, presumably doing doing fuel intensive altitude changing maneuvers, and were eventually able to land safely with their reserves almost exhausted.
I’m a little confused by what there is to investigate at all.
In safety-critical systems, we distinguish between accidents (actual loss, e.g. lives, equipment, etc.) and hazardous states. The equation is
hazardous state + environmental conditions = accident
Since we can only control the system, and not its environment, we focus on preventing hazardous states, rather than accidents. If we can keep the system out of all hazardous states, we also avoid accidents. (Trying to prevent accidents while not paying attention to hazardous states amounts to relying on the environment always being on our side, and is bound to fail eventually.)
One such hazardous state we have defined in aviation is "less than N minutes of fuel remaining when landing". If an aircraft lands with less than N minutes of fuel on board, it would only have taken bad environmental conditions to make it crash, rather than land. Thus we design commercial aviation so that planes always have N minutes of fuel remaining when landing. If they don't, that's a big deal: they've entered a hazardous state, and we never want to see that. (I don't remember if N is 30 or 45 or 60 but somewhere in that region.)
For another example, one of my children loves playing around cliffs and rocks. Initially he was very keen on promising me that he wouldn't fall down. I explained the difference between accidents and hazardous states to him in childrens' terms, and he realised slowly that he cannot control whether or not he has an accident, so it's a bad idea to promise me that he won't have an accident. What he can control is whether or not bad environmental conditions lead to an accident, and he does that by keeping out of hazardous states. In this case, the hazardous state would be standing less than a child-height within a ledge when there is nobody below ready to catch. He can promise me to avoid that, and that satisfies me a lot more than a promise to not fall.
If you haven't done so: please write a book. Aim it towards software professionals in non-regulated industries. I promise to buy 50 to give to all of my software developing colleagues.
As for 'N', for turboprops it is 45, for jets it is 30.
I want to write more about this, but it has been a really difficult subject to structure. I gave up halfway through this article, for example, and never published it – I didn't even get around to editing it, so it's mostly bad stream of consciousness stuff: https://entropicthoughts.com/root-cause-analysis-youre-doing...
I intend to come back to it some day, but I do not think that day is today.
Just started reading the linked text after reading your comment and I agree, this is high quality education, and enjoyable. It's an art, really. Thank you for sharing your work and please keep it up.
Just a thought I had while reading your introduction: this is applicable even to running a successful business model. I'm honestly having trouble even putting it into words, but you have my analytical mind going now at a very late hour... Thanks!
Ok. I am impressed with your ability to take such complex subjects and make them plain, you are delivering very high quality here. The subject is absolutely underserved in the industry as far as I'm aware of it, and I would love to have a book that I can hand out to people working on software in critical infrastructure and life sciences that gets them up to speed. The annoying thing is that software skills are values much higher than the ability to accurate model the risks because that is only seen as a function of small choices standing by themselves. A larger, overall approach is what is very often called for and it would help to have a tool in hand to both make that case and to give the counterparty the vocabulary and the required understanding of the subject in order to have a meaningful conversation.
Edit: please post your link from above as a separate submission.
Your writing is good, please keep at it. I think it would help a lot if you made it clearer when you're talking between root-cause-analysis for software, aviation, other things, or generically.
Also, your train-of-thought is pretty deep; bulleting runs out of steam and gets visually confusing, especially with the article table-of-contents on RHS, you're only using <50% of screen width. Suggest you need numbered/lettered lists and section headings and use the full screen width.
See also: various points in the Evil Overlord list[0]. Selected examples:
#12: One of my advisors will be an average five-year-old child. Any flaws in my plan that he is able to spot will be corrected before implementation.
#60: My five-year-old child advisor will also be asked to decipher any code I am thinking of using. If he breaks the code in under 30 seconds, it will not be used. Note: this also applies to passwords.
#74: When I create a multimedia presentation of my plan designed so that my five-year-old advisor can easily understand the details, I will not label the disk "Project Overlord" and leave it lying on top of my desk.
That being said: I have - for some years now - started to read air accident board reports (depending on your locale, they may be named slightly different). They make for a fascinating read, and they have made me approach debugging and postmortems in a more structured, more holistic way. They should be freely available on your transportation safety board websites (NTSB in America, BFU in Germany, ...)
Google’s SRE STPA starts with a similar model. I haven’t read the external document, but my team went through this process internally and we considered the hazardous states and environmental triggers.
> Trying to prevent accidents while not paying attention to hazardous states amounts to relying on the environment always being on our side, and is bound to fail eventually.
The reason they had less than 30 minutes of fuel was because the environment wasn't on their side. They started out with a normal amount of reserve and then things went quite badly and the reserve was sufficient but only just.
The question then is, how much of an outlier was this? Was this a perfect storm that only happens once in a century and the thing worse than this that would actually have exhausted the reserve only happens once in ten centuries? Or are planes doing this every Tuesday which would imply that something is very wrong?
This is why staying out of hazardous conditions is a dynamic control problem, rather than a simple equation or plan you can set up ahead of time.
There are multiple controllers interacting with the system (the FADEC computer in the engines, the flight management computer in the plane, pilots, ground crew, dispatchers, air traffic controllers, the people at EASA drafting regulations, etc.), trying to keep it outside of hazardous conditions. They do so by observing the state the system and the environment is in ("feedback"), running simulations of how it will evolve in the future ("mental models"), and making adjustments to the system ("control inputs") to keep it outside of hazardous conditions.
Whenever the system enters a hazardous condition, there was something that made these controllers insufficient. Either someone had inadequate feedback, or inadequate mental models, or the control inputs were inoperational or insufficient. Or sometimes an entire controller that ought to have been there was missing!
In this case it seems like the hazard could have been avoided any number of ways: ground the plane, add more fuel, divert sooner, be more conservative about weather on alternates, etc. Which control input is appropriate and how to ensure it is enacted in the future is up to the real investigators with access to all data necessary.
-----
You are correct that we will not ever be able to set up a system where all controllers are able to always keep it out of hazardous states perfectly. If that was a thing we would never have any accident ever – we would only have intentional losses that are calculated to be worth their revenue in additional efficiency.
But by adopting the right framework for thinking about this ("how do active controllers dynamically keep the system out of hazards?") we can do a pretty good job of preventing most such problems. The good news is that predicting hazardous states is much easier than predicting accidents, so we can actually do a lot of this design up-front without first having an accident happen and then learning from it.
> This is why staying out of hazardous conditions is a dynamic control problem
I don't think this philosophy can work.
If you can't control whether the environment will push you from a hazardous state into a failure state, you also can't control whether the environment will push you from a nonhazardous state into a hazardous state.
If staying out of hazardous conditions is a dynamic control problem requiring on-the-fly adjustment from local actors, exactly the same thing is true of staying out of failure states.
The point of defining hazardous states is that they are a buffer between you and failure. Sometimes you actually need the buffer. If you didn't, the hazardous state wouldn't be hazardous.
But the only possible outcome of treating entering a hazardous state as equivalent to entering a failure state is that you start panicking whenever an airplane touches down with less than a hundred thousand gallons of fuel.
My understanding is that the SOP for low fuel is that you need to declare a fuel emergency (i.e., "Mayday Mayday Mayday Fuel") one you reach the point where you will land with only reserve fuel left. The point OP was making is that the entire system of fuel planning is designed so that you should never reach the Mayday stage as a result of something you can expect to happen eventually (such as really bad weather). If you land with reserve fuel, it is normally investigated like any other emergency.
Flight plans require you to look at the weather reports of your destination before you take off and pick at least one or two alternates that will let you divert if the weather is marginal. The fuel you load includes several redundancies to deal with different unexpected conditions[1] as well as the need to divert if you cannot land.
There have been a few historical cases of planes running out of fuel (and quite a few cases of planes landing with only reserve fuel), and usually the root cause was a pilot not making the decision to go to an alternate airport soon enough or not declaring an emergency immediately -- even with very dynamic weather conditions you should have enough fuel for a go-around, holding, and going to an alternate.
We'll find out in the investigation, but "get-there-itis" is a very common condition amongst pilots and can lead to them delaying making decisions (such as going to alternates) so it's possible that this happened without explicit (or implicit) pressure from management.
That being said, the fact that (AFAICS) they first tried to divert to a closer airport where the weather was similar rather than an alternate with clear weather was probably one of the causes of this event.
That's very enlightening. I'm casually interested in traffic safety and road/junction designs from the perspective of a UK cyclist and there's a lot to be learnt from the safety culture/practices of the aviation industry. I typically think in terms of "safety margins" whilst cycling (e.g. if a driver pulls out of a side road in front of me, how quickly can I avoid them via swerving or brake to avoid a collision). I can imagine that hazardous states can be applied to a lot of the traffic behaviour at junctions.
As others have said, final fuel reserves are typically at least half an hour, and you shouldn't really be cutting into them. What if their first approach into MAN had led to another go around?
With a major storm heading north-easterly across the UK, the planning should have reasonably foreseen that an airport 56 miles east may also be unavailable, and should've further diverted prior to that point.
They likely used the majority of their final fuel reserve on the secondary diversion from EDI to MAN, presumably having planned to land at their alternate (EDI) around the time they reached the final fuel reserve.
Any CAA report into this, if there is one produced, is going to be interesting, because there's multiple people having made multiple decisions that led to this.
Suspect they were IFR. All your points stand. First time flying things with a jet engine, I was shocked how much more fuel gets burned at low altitude. It almost always works out better to max climb to altitude and descend than to fly low and level. On a small jet, things can get spicy fast when ATC route you around at 5000' for 15 minutes or so. Three aborted landings would gobble gas like crazy.
§ 91.167 Fuel requirements for flight in IFR conditions.
(a) No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to—
(1) Complete the flight to the first airport of intended landing;
(2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and
(3) Fly after that for 45 minutes at normal cruising speed
They were most definitely IFR. Not because of the weather but because IFR is required above certain altitude 18,000 ft in the U.S. and typically lower in Europe (depends on a country). Jets including small private jets are almost always on IFR. Airliners with passengers - always.
Not just that. Jet engines are efficient at higher speeds because the exhaust of the jet engine is fast.
If the plane is going fast as well, that exhaust is more or less stationary relative to the ground. The engine works to exchange the position of the plane with the position of the air in front of it.
If the plane is going slow, it's accelerating the air backwards. That's where the work is going, making the engine less efficient.
Think about it this way: if the jet airplane is tied to the ground, its engines are running at 0% efficiency, working hard to blow the air backwards. You wouldn't want to stand behind a jet engine when the plane is about to take off, when that's effectively the case.
The same applies to propeller-driven planes, of course. But those can vary the prop speed as well as propeller pitch, having more control on how fast the air is being pushed backwards. This allows the engine to be efficient at a wider ranger of speeds, particularly, at the slower range.
But the propeller has a limit of how fast it can push the air back. When the prop blades start reaching the speed of sound, weird shit starts happening [1]. So propeller-driven aircraft have a limit on speeds at which they can go efficiently.
Jet engines (turbofans when it comes to airliners) trade off low efficiency at low speed / low altitude (where the airplane is spending a small percentage of flight time) for higher efficiency at high speed / high altitude.
Variable pitch turbine fans[2] aim to address this tradeoff, but the tech has yet to catch on.
Jet needs to suck air from front. If air is stopped, sucking is hard. If air is already being thrown at you, you don't even need to suck, just let it come in.
You are right that accelerating the air backwards more reduces efficiency but I think it should be mentioned that the jet engine has to accelerate the air backwards to do any work pushing the plane forward. Picking it up and setting it back down affects the air with a net force of zero and therefore the force pushing the plane forward is also zero.
So perhaps the differential air speed between the intake and exhaust is a big factor in the efficiency equation? The bigger the difference the more work is needed..
Just reaching altitude again to make it to the first and later second alternate are mostly likely the biggest factors in the extra fuel consumption. That's very expensive.
The 30 min reserve is on top of the fuel needed to reach the alternate and do a landing there, so only the flight to the second alternate, plus the 2nd and 3rd landings at the initial destination would have cut into the reserve.
With 100mph winds I could easily see the 30 min reserve being eaten up by the flight from Edinburgh to Manchester. It's 178 miles! It takes a good 15-20 minutes to cross that distance when flying normally, add ascent & descent time and the landing pattern and you're easily at 24 minutes.
Edit: in other comments here, it seems like Edinburgh to Manchester is a 45 minute flight. So yeah, they could easily have been outside of reserves when they did the go-around at Edinburgh and still had only 6 minutes left at Manchester.
Yeah, although it depends what the alternate was in the flight plan. It may have been Manchester. Although I think its more likely it was Edinburgh, which in the circumstances was too optimistic. Too much concern about the minimal costs of fuel tankering to add a bit more gas? Or saving time by not refuelling?
As far as I’ve heard, Ryanair will cut into literally everything (including comfort and decency) for the sake of efficiency – other than safety. Even if they wanted to, they're subject to the same commercial aviation regulations as everybody else.
Do you have anything other than this single incident to back up your insinuation that they’re less safe than a full service airline?
I don't know how true this is but I have heard Ryanair will use the absolute legal minimum amount of fuel whenever possible whereas other airlines might fly with a bit more.
In theory though that shouldn't matter because as you say, the legal minimum should really be enough.
That seems like a cost/convenience tradeoff: The implication of only carrying minimum fuel is that the pilots can't hold for long to see if conditions improve and instead have to immediately go for the alternate destination airport.
The consequence of that is everybody ending up in the wrong place, but not in an unsafe way.
The flight plans I've seen accounted for two alternates, not one, a significant time in a holding pattern and up to three go-arounds. This was for cargo 747s and a while ago so chances are the regulations have changed by now, also, it may have been due to the kind of cargo.
From what I can tell, that only seems to apply to EASA since 2022. As it took off from an EU airport and landed in the UK, I don't know if that rule would apply.
Yes, you get "some" back, and its not negligible amount. Typical modern airliner can descend on 15-20:1, giving you over 150-200km (90-120mi) range from typical cruising altitude of 33 000 feet even with engines off. Most everyday descents are actually done by maintaining altitude as long as possible, and then iddling the engines fully for as long as clearance allows. (Ofc you then use engines as you geat nearer, because its safer to be a little low when stabilizing on approach, than a little high)
Thanks to turbofans(edited from turboprops) better efficiency + less drag at higher altitude its actually more fuel economical to command full thrust and gain altitude quickly, than slower climb, or maintaining altitude (which goes against our intuition from cars, where if you wanna get far, you never give full throttle).
But theres still some drag, so you dont get everything back, so you generally want to avoid murking in low altitudes as long as possible. Full thrust repeatedly at lowest altitudes (from failed go arounds) is the least economical part of flight, so you want to avoid those if possible. But its true that the altitude you gain is equivalent to "banking" the energy, just not all of it.
Edit: changed turbofan into turbprop, which is what I meant.
(2) fuel burned stays burned, you don't 'get it back'
(3) the altitude gained may have been adjusted to account for the low fuel situation
(4) the winds are a major factor here, far larger than the fact that 'what goes up must come down', something that is already taken into account when computing the fuel reserve in the first place.
> fuel burned stays burned, you don't 'get it back'
The it that they get back is not fuel, it's energy. Maintaining flight is energy management. They are getting the gravitational potential energy back, which is converted to velocity on descent, or bled off in drag by slowly losing altitude while maintaining airspeed.
So it seems. But because you want to land you then want to shed all that velocity. So you 'get it back' only to have to waste the bigger fraction of it. A go around is much like a mini take-off, you just miss the runway portion of it.
Nah. You want to land, but you are really not shedding most of your velocity until after touchdown. What you gain by burning fuel is energy, and you can either bank it into altitude, or velocity. You must shed both to land, but not so for go-around. There you shed almost all of your altitude, but you keep most of your velocity -> you still have a lot of energy left. That's why on go-around you spool your engines and start climbing basically right away, unlike typical takeoff, where after spooling up the engines you are still earth-bound until you build enough velocity.
So you only ever really lost your "altitude" component of energy, not "velocity" one. You run your engines at TOGA (Take Off / Go Around = maximum thrust), thrust to gain mainly altitude, only increasing speed a little bit. Then on another approach attempt you use both the altitude and excess velocity bank again.
In flight, ~all your energy losses go to drag. Doesn't matter if you bank it into speed or altitude, both is exchanged to be at minimums (0 altitude above ground, lowest safe landing speed) at touchdown. If you produce extra energy in your engines, it has to go to either speed or altitude, which you then pull out again, usually by maintaining speed while lowering altitude while having engines at idle.
(1) The turbofan category of jet engine seems to inspire a lot of very pretty animated technical diagrams—here’s one set from a German manufacturer [0]. Now if only we could convince Bartozs Ciechanowski to take on such a subject… [1]
(2) I know glider pilots who fly without any fuel at all, once aloft… sounds not unlike the 150-200km glide range that @MaxikCZ mentions at idle from cruising altitude.
Aircraft that are designed as gliders are much lighter and thus have much longer glide range than aircraft that aren't. They're so lightweight that they can climb on thermals. A 737 is not going to be able to do that, but a regular glider can't fly at 400 knots.
Im gonna be a little pedantic, but the weight has surprisingly small effect on glide range, actually none of the weight affect the range directly, its all from secondary effects.
The glide is given mainly by drag and lift (so body and wing geometry), correlated to certain speed. The weight isnt in the equation at all. What weight does, is increases the speed in which the aircraft achieves this maximum glide ratio, and in higher speed you have higher drag, which finally reduces the range.
Thats why many modern gliders have water tanks in wings, to increase the weight of the glider, moving planes speed of best glide ratio higher, allowing for more efficiency at higher speeds. Its worth it if the atmospheric condition provide strong lifts. Pilot can then dump the water in flight to reduce the wing load, allowing them to land with less speed, or just keep in the air longer as thermals get weaker in the afternoon/evening
It should also be noted that gliders have crazy aspect ratios. Airliner wings are designed for completely different flight envelopes than gliders, it’s all a game of what you optimize for and what trade offs you are willing and/or required to make.
But of course that doesn’t mean that airliners can’t glide well, the Gimly Glider and Air Transat flight come to mind. But gliders can definitely beat an airliner in terms of performance.
Re: (2): There's a difference between sailplanes and gliders. Sailplanes are gliders that can “soar”, i.e. gain altitude just from the air that is moving up for some reason. Your friends have licence that says „Sailplane Pilot Licence”, not „Glider”.
The distinction is less pronounced nowadays, because there is no mondern aircraft designed as gliders-but-not-sailplanes, but historically there were planes that fit this niche, mostly military transport of WW1 and WW2 vintage.
Passenger jets (with engines turned off) are relatively decent gliders, but incapable of soaring. So no, you can't get more that about 20:1 glide ratio no matter how good is the weather (for sailplanes).
Regarding the turbofan and [0], above...if you're communicating to a non-engineer (me), how does the design get to the point of such complexity? I would love to learn the design story behind such an incredibly complex piece of machinery.
For the same thrust it's more efficient to accelerate a large mass of air a small amount than t accelerate a small mass of air a large amount. The fan is what gives you that.
I rough guessed the cost of fuel over a 737's life as $150 million. Where the engines cost something around $30 million. That pushes the engineering economics towards maximizing the engines efficiency.
I'm suspicious that bypass ratio's for turbofans are close to maxed out. The diameter of the fan gets unwieldy. That was the design issue that the 737 Max was trying to get around. With bad results. Possible the future is hybrid designs with two engines and 4 or more electrically driven fans.
1 - a turbofan is a subset of jet engine, and there are no 738s running anything other than a turbofan.
Actually, nothing in civil aviation that has a "jet engine" has used anything but a turbofan (or turboprop) since the early 70s with the exception of Concorde and some older business jets.
(Turboprops are jet engines, too, to be precise, with the jet of exhaust gases powering the propeller.)
They are certainly turbine engines, but I thought "jet" was reserved for those engines that propel the vehicle solely by their exhaust stream and bypass air. I am willing to be told I'm wrong, though.
No, you don’t magically get the fuel back. But you do get a lot of the _kinetic energy_ back, and that energy keeps you flying without having to burn yet more fuel. You burn a lot of fuel while climbing, but then hardly any at all while descending. And that descent might cover 100 miles across the ground.
2) It stays burned, but the energy is banked in potential energy of the aircraft, namely in a form of altitude. If you run out of fuel 5 feet above ground, you dont get to fly far. When you run out of fuel 35000 feet above ground, you can still choose where to land from multiple options.
3) huh? I dont get what you trying to say, but: Its always more economical to climb, and the faster the better. Ofc you cant climb too high when you intend to attempt to land in 5-10 mins, but nontheless, every feet gained is "banked", and the aircraft is more economical to run the higher you are.
4) I am not saying the winds arent a factor, and in no way I was arguing about how fuel reserves are calculated. My only claim is that: yes, by spending more fuel to gain altitude, you can then "glide" down almost for free later. Its not 1:1, because of constant losses like drag, but its being compensated by higher engine efficiency and less drag at altitude, that its always worth it to climb if you can.
There was a flight that was low on fuel diverting to alternate between 2 islands. The pilot panicked and chose slower climb to intuitively save fuel. They had to ditch the plane in water because of it - if they initiated full climb, they would have made the jump.
Yes, you get a lot of the energy back, BUT there is a huge problem!
Large airliners incur a LOT of additional drag to slow down while landing. Some of that is entirely intentional, some is less intentional.
It is highly preferred to deploy the landing gear before touching down. Failure to do so may lead to a hard landing and additional paperwork, so airlines do not allow the captain to exercise their own discretion.
Extending the flaps maintains lift at lower speed, and higher flap settings allow even lower speed. The highest flap setting generally also deploys leading edge slats.
If the wheels of the airliner touch down and detect the weight of the plane then spoilers kill the lift of the wings, air brakes fully deploy, as well as thrust reversers.
All of these things add drag, which uses up all that energy you've been converting.
The upshot is that each landing attempt uses a LOT of energy, and you have to use fuel to replenish that energy after every attempt.
In other words, yes you get it back, but only for one landing attempt.
That is perplexing. Of course you get the potential energy back. It turns into kinetic energy as you descend. That is why you need not pedal downhill, and often even need to brake to prevent the bike from speeding up too dangerously.
> often even need to brake to prevent the bike from speeding up too dangerously.
Indeed, which is what the airplane would have done on its way down to land. So it's more like riding the brakes on your way down the hill, and now at the bottom when you realize you need to abort the landing, you are at low speed and it's quite an exercise to get back uphill to try again
100%. You are correct on that. You can’t use your kinetic energy to go around after a landing attempt.
But not because “you don’t get the energy back”. (As recursive suggested about a downhill bike ride which is the part i am disagreeing with.) You do get it back, but because you want to land you bleed it away to drag. And once it is bled away you don’t have it anymore.
So we don’t disagree about the practical implications for flying. I’m disagreeing with recursive’s particular statement about downhill cycling and what it implies about the physics of the problem.
The glider guys would always suggest a forward slip. It's a lot of fun to do. It's not taught often enough during primary training for powered airplanes.
Aren't low-speed slips something that makes planes flip upside-down when not used very carefully? (Inadvertent rudder changes corrected with opposite aileron resulting in a snap roll.)
A cross controlled stall can result in a spin (which is probably what you mean by flip upside down). The rudder changes aren't inadvertent, they're intentionally opposite the aileron input - the goal is essentially to fly somewhat sideways, so the fuselage induces drag.
In general forward slips are safe, but yes you have to make sure you keep the nose down/speed up. There's little in aviation that isn't dangerous if you aren't careful.
Yes, being that one is cross-controlled they must be used very carefully. It's really obvious that one is cross-controlling. It's the only time outside of really powerful crosswinds that you see what's below and ahead of you out of the side window. That view is what makes it fun.
You're probably thinking of a skid, which is when you put too much rudder in the same direction as the ailerons. Then the lower (and slower because it's on the inside) wing stalls first (and goes lower still) and away you go. Often when turning to land, so there's not enough altitude to recover.
Well it's not all lost otherwise it'd be a stall spin accident caused by performing the maneuver with too little airspeed. And that's hard to do. It's a noisy maneuver, the air slamming against the fuselage makes itself heard. Once performed it's not easily forgotten.
More dangerous than inadvertently spinning with too little airspeed is the possibility of shock cooling when relying on a forward slip for too much altitude loss. It really does need to be well-controlled.
I thought this topic was about energy gained and lost during a go-around. If velocity was V and altitude was H before the go-around, and velocity and altitude are again the same V and H after the go-around, then it follows that all the potential energy that was accumulated during the go-around (from converting fuel into altitude) has been dissipated (lost). Otherwise V would be higher the second time.
Imagine a hill with 500 feet of elevation descent, followed immediately by 500 feet of ascent. No curves.
If you coast all the way down the first part, you'll get about 20 feet up the other hill before you need to start pedaling. This is a direct analogy to "getting your energy back" by losing elevation.
That is exactly what a rollercoaster does and it doesn’t start “pedaling” after 20 feet. Of course real systems have losses and you can’t practically use all the energy.
It is a glider so it can’t “pedal”. You can see it steeply descending from 5:13 to 5:30 while it is speeding up and then the pilot picks up the nose and trades some of his speed for elevation again. And then he does it again around the 7 minutes mark.
You have two buckets of “water”. One bucket is kinetic energy and the other is potential energy. You can trade one for the other. You can also “lose” from the total volume of “water” due to drag (or friction in the case of the bike or roller coaster). Or you can add more “water” to your system by pedaling or thrusting with your engines. This is just simple physics 101. Also simple lived experience if you ever have the opportunity to fly an airplane.
This is because bikes cost you about 50% more energy going uphill than walking[1]. You get back everything you don't lose from having to pedal too slowly, hunch over the front wheel, and maintain constant torque on the pedals.
Just as with bikes, it will depend on how slow it is descending. On "right" trajectory engines could technically be basically idle, and you save fuel flying high so it might not be all that huge loss.
How? On descent you can trade some of your altitude (potential energy) for kinetic energy, but then you can’t land the plane. For descent on an approach you’re going from low energy to even lower energy. In emergencies and with enough runway you can futz around with this some, but wiggle room on an airliner is not great, negligible to what will be expended on a go around.
Some of it. The air density is an important part of efficiency at higher altitudes, so every moment spent under like FL320 is wasted fuel.
So the entire climb "up", you are also wasting energy fighting the thick air. On the way back "down", that air again fights you, even though you are basically at idle thrust.
Your fuel reserves are calculated for cruise flight, so time spent doing low altitude flying is already at a disadvantage. "Two hours of reserves" is significantly less than that spent holding at a few thousand feet. Fuel efficiency while climbing is yet again dramatically worse
Not really. While you have a large potential energy buildup at a higher altitude, you cannot "bank it" / "save it" on descent. There is no way to store it in batteries or convert it back into fuel.
One of the challenges of aeronautics is the efficient disposition of the potential energy without converting it all into kinetic energy (ie speed) so that the landing happens at an optimally low speed - thus giving you a chance to brake and slow down at the end.
> "While you have a large potential energy buildup at a higher altitude, you cannot "bank it" / "save it" on descent. There is no way to store it in batteries or convert it back into fuel."
An electric fan aircraft absolutely can recharge it's batteries on descent. The fans simply act as turbines, creating drag to slow the aircraft and electricity to charge the batteries. Large commercial airliners already have a small turbine that works this way, the Ram Air Turbine (RAT) which is used to generate electrical power in emergencies.
You can use a turbine to generate electricity, so yes, you are converting potential energy into electrical potential. However, no real mass produced passenger plane today can use that electricity for flight (thrust).
RAT is only used when sh*t hits the fan. Even then, it can help you power some hydraulics / electrical, not “store” energy for further flight.
The OP asked - in a low fuel situation, can the energy spent on a climb get effectively recovered - and the answer is not really. We convert as much as we can into unpowered (low-powered) descent. But once you are at a spot where you make a final decision to land or not, you are by design low and slow - and all that energy you had 15m ago is gone.
If you need to keep flying, those engines need to spool back up. And that takes fuel.
> "no real mass produced passenger plane today can use that electricity for flight (thrust)"
Such aircraft do exist. For example, the Pipistrel Velis Electro trainer. And more recently, the Rhyxeon RX4E became the first electric aircraft to be type-certified for commercial passenger operations.
It's likely that we'll see many more electric fan aircraft in the coming years/decades, whether powered by batteries and/or hydrogen fuel cells, or hybrids with both conventional turbofan and electric propulsion in order to improve efficiency and environmental performance.
> As others have said, final fuel reserves are typically at least half an hour, and you shouldn't really be cutting into them.
This is one of the multiple layers of defense that airlines employ. In theory, no one single failure should cause a major incident because of redundancies and planning. Airlines rely on the "Swiss-cheese" model of safety. Each layer has its own risks and "holes" but by layering enough layers together there should be no clear path between all of the layers. In theory this prevents major incidents and given the commercial airline's safety records I'd say it works pretty fucking well. Landing with minutes of fuel left should be exceptional. But it also shouldn't be fatal or a major risk due to the other layers of the system. ATC will move heaven and earth to land a plane low on fuel or with engine trouble safely. And everyone else in the system having 30+ minutes of extra fuel gives the space for this sort of emergency sorting.
I think this also reflects on the "efficiency" that MBA types bring to companies that they ruin. If an MBA sees a dozen landings with an extra hour of fuel, their mind starts churning at saving money. Surely an hour of extra fuel is too much and just wasted. Wasted because every extra gallon of fuel you take off with is extra weight you have to carry throughout the flight. Surely things would be more efficient if we could make sure planes only carry enough fuel to make their trip with very minimal overhead. And when everything goes perfectly according to plan, these decisions work out fine. Money is saved. Bonuses are paid. But the inevitable always happens. That's why it's called inevitable. Lives are lost. Wrists are slapped. Some people at the bottom lose their jobs. The world moves on.
I thought a lot of airlines had rules to limit the number of attempts you could make at a single airfield in an attempt to prevent this exact kind of situation.
It sounds to me like they tried harder at their intended destination than maybe they should have, followed by going to an alternate airport that probably wasn’t a good choice in the first place, and then having to divert to the final airport where luckily they could land in time.
Interesting. To me it does not really make sense to think in terms of fuel left because, no matter the reserves, there can always be a situation so unlikely, so outside the ordinary, that it will drain all fuel reserves before you make it to the planned destination.
I'm not an aviation expert, but generally in safety engineering, safety buffers are not simply calculated as [normal situation] * [safety factor], but [worst case scenario] * [safety factor]
If you ever cut into your safety allowance, you've already fucked up. Your expected design criteria should account for all use cases, nominal or worst-case. The safety factor is there for safety, it is never intended to be used.
This is really helpful and I think I understand now.
The approach is basically “accounting for everything that might go wrong to the best of our experience, including problems arising from the complex interactions between the airplane and supporting ground systems and processes, this is how much fuel you need in the worst case scenario. And now lets add more to give us a cushion, and we will treat consumption of this last reserve as tantamount to a crash.”
This is exactly how it is in this case. Any consumption of the fuel reserve would result in an investigation, this is a very extreme case and it may even result in a change in the rules depending on the root cause.
Yes, exactly. The day it's normal to eat into the allowance is the day we start seeing planes falling out of sky for lack of fuel again. The only way to prevent that is to treat 30 min of fuel as seriously as you would 0 minutes.
Yes. Similarly, safety needs to be there even after the aging of materials over product lifetime. So basically when aging is the only variable to be considered end of life date is the worst case scenario.
I think the argument is that this is precisely the tail end of exceptional conditions overfueling is designed for. If it's typical to fill fuel for 4 hours on a 2 hour flight, and the flight took 4 hours. It seems like this is exactly why they overfuel to 4 hours. If this happens once every 100k flights, then it doesn't even beg the question of "why aren't we overfuelling to 4.5 hours".
This is just clarifying the question from the perspective of an outsider.
That said, an investigation would be pretty reasonable, even if only to confirm that the abornamlity were forces majeures
Why not? It's a factual report stating that the AAIB has opened an investigation into a potentially dangerous incident. There's not any editorial bias evident. See other extensive comments as to why this is not just a case of "it landed, so what's the problem?".
Or did it work as intended? The plane had multiple failed landing attempts, was re-routed, and had enough fuel to land safely. While no one wants to cut it this close, this was not a normal flight.
I’m not an expert in this field, but it would seem that the weight of extra fuel would increase operating costs, so it’s is effectively insurance. How much extra fuel should be carried to account for unplanned events like this, while not carrying so much that it becomes cost prohibitive.
That example is so well known due to how exceptional it was, especially how the pilots handled it. Robert Pearson, the captain, was a very experienced glider pilot. That's something that not many commercial pilots have.
There were also two factors in the landing, that allowed for this to happen. You're going to be coming in really fast for a landing, when gliding in a commercial jet, and you don't have access to your thrust reversers to slow it down. There was a repurposed runway, that they used to land, that just happened to have been used as a drag racing track and had a guard rail. They were able to slow down by scraping across that. It also just so happened the nose gear didn't deploy fully so scraping the nose of the plane against the ground also helped slow it down.
Needless to say it was a bunch of very fortunate events that allowed it to not end in disaster. In any case I would consider it very risky.
The "scraping helped slow it down" theory makes no sense to me. What do you think has a higher coefficient of friction - tire rubber on asphalt, metal on asphalt, or metal on metal?
I would hesitate to chalk it up to just theory, given it was in the NTSB report and they don't really mess around with throwing baseless stuff around. I'd be interested to take another look at it. They likely go into the material science and physics behind this very thing. They're usually filled with gems.
You also have to keep in mind, it wasn't just rubber against asphalt, it was rubber on a wheel that spins. I'm not sure if the front nose gear on a 767 has any brakes but even if it did, I can't imagine it would be sufficient at the speeds they were going.
I mistyped, as this was Canada it wouldn't be the NTSB but the Canadian equivalent at the time: Canadian Aviation Safety Board. The report is a good read.
Rubber likely grips much better than metal, however three wheels have massively lower surface area than the body of the plane, or even a small section of it like the head.
Of course we don't land tireless for other reasons (metal transfers heat exceptionally well unlike rubber, paint doesn't survive high speed impact, and it tends to deform upon impact with anything, making any future flights unsafe), but the fastest way to slow down if you don't care about safety or comfort would probably be to land tireless, if you could introduce some rotational spin, that might be faster (more force directed in multiple directions).
Also, on the note of "coefficient of friction", remember that this number is not just some innate property of a molecule - as the metal scratches the pavement and deforms, its coefficient of friction goes up as micro-deformities accrue.
Fuel depletion is stupendously risky, it is one of the most risky things that can happen to a jet. The only things more dangerous are fire and control systems failure.
The Gimli Glider was a case of many items of luck lining up.
You could've read at least the Wikipedia page on how miraculous Gimli Glider was.
From "all engine failure is never expected and not covered in training" to "Pearson was an experienced glider pilot familiar with techniques rarely needed in commercial flights" to the amount of maneuvers they had to execute on a barely responding aircraft
I know you're trolling, but for anyone that hasn't heard of Gimli Glider, look it up or watch a documentary on youtube. The stars definitely aligned to make that happen.
Fuel depletion is _not that risky_ is an interesting take. But hey, it won Chapecoense its first and only Copa Sudamericana, so maybe it isn't that bad after all?
Depends if our goal is to have zero aircraft crashes. If the goal is zero, then for any given parameter, you have to define a margin of safety well before crash territory and treat breaching that margin as seriously as if there had been a crash.
Similarly planes are kept 5 nautical miles apart horizontally, and if they get closer than that, you guessed it - investigation. Ofc planes could come within inches and everyone could live, but if we normalize flying within inches, the we are also normalizing zero safety margin, turning small minor inevitable human failings into catastrophe death & destruction. As an example, planes communicate with ATC over the radio and are given explicit instructions - turn left 20 degrees, fly heading 140 etc. From time to time these instructions are misunderstood and have to be corrected. At 5nm separation everyone involved has plenty of time to notice that something was missed/garbled/misinterpreted etc and correct. At 1 inch separation, there's no such time. Any mistake is fatal, even though in theory you are safe when separated by 1 inch.
TBC an investigation doesn't mean investigating the pilots in order to assign blame, it means investigating the entire aviation system that led up to the breach. The pilot's actions / inaction will certainly be part of that, but the goal is to ask, "How could this have been avoided, and ask how every part of the system that we have some control or influence over might have contributed to the outcome"
We shouldn't aim for 0 crashes due to low fuel though. How many deaths does carrying around 3x fuel than what you reasonably need contribute to via extra pollution?
We should aim for 1 every 10-100 years or something reasonable like that.
We should account for deaths from pollution, but if we are going to do that, we should be willing to do that for 99% of aviation fuel that has nothing to do with reserves & safety margins, in addition to fuel used to drive cars.
Any regulation short of "carry infinite fuel" will be a trade-off, and entail some risk and anyone involved in setting these knows that. Zero may not be our actual target or even possible, but it is a useful aspiration to ensure that everyone is pulling in the right direction.
Well imagine they had to do a go-around on that landing. Go-arounds are extremely normal and might be done for a million reasons; your speed is wrong, your descent rate is wrong, your positioning is wrong, there's bad wind, there's an issue on the ground, etc etc etc. Six minutes of fuel is really not enough to be sure that you can do a go-around. So now, if ANY of those very normal everyday issues occurs, the pilot has to choose between two very bad options: doing a go-around with almost no fuel, or attempting a landing despite the issue. That's just way too close for comfort.
Aviation operates on a Swiss cheese model; the idea is that you want many many layers of safety (slices of cheese). Inevitably, every layer will have some holes, but with enough layers, you should still be safe; there won't be a hole that goes all the way through. In this case, they basically got down to their very last slice of cheese; it was just luck that the last layer held.
>I’m a little confused by what there is to investigate at all.
One of the most important aspects of taking safety seriously is that you do not just investigate things which had an impact, but that you proactively investigate near misses (as was the case here) and even potential incidents.
A plane with 6 minutes of fuel left is always a risk to every person on board and potentially others if an emergency landing becomes the only option.
Indeed that is the definition of a "aviation incident" where there was a risk of injury or damage. If there is actual injury or damage it becomes an "accident".
The investigations into incidents aren't usually particularly long or noteworthy and often the corrective action will be to brief X on dangers of Y, or some manner of bulletin distributed to operators.
If they have to touch and go, how long would it take until they get the plane around for another approach? In fact, you might not get as far as that touch and go and have to go around. You need some margin for all of these eventualities. The likelihood is low that these happen, but they have to be accounted for.
Sure, but the flight was a lot longer than planed. How much extra do we need. They declared an emergency, and thus put themselves at the front of the line. They had 6 more minutes to do that touch and go around if that happened, and since they were already in a low fuel emergency they get priority and so there is enough time to do that if they needed. (edit - as others have noted, 6 minutes with high error bars, so they could have only had 30 seconds left which is not enough)
They landed safely, that is what is important. There is great cost to have extra fuel on board, you need enough, but it doesn't look to me like more was needed. Unless an investigation determines that this emergency would happen often on that route - even then it seems like they should have been told to land in France or someplace long before they got to their intended destination to discover landing was impossible.
Correct, article says they landed with 220kg which is around 6 minutes of average fuel burn over an entire flight - bit less at cruise, a hell of a lot more at takeoff/climb.
So I don't think 220kg is enough to do a go-around in a 737 (well, a go-around would've been initiated with a bit more than 220kg in the tank - they burned some taxing to the gate - but you get my point.) I've read around 2,300kg for takeoff and climb on a normal flight in a 737-8. A go-around is going to use close to that, it's a full power takeoff but a much shorter climb phase up to whatever procedure is set for the airport and then what ATC tells you.
I just flew 172s but even with those little things we were told, your reserve is never to be used.
These people came very, very close to a disaster. Fortunately they had as much luck left as they did fuel.
Isn’t a 737-8 the max 8 variant? It uses newer dual CFM LEAP-1B engines. How does it compare? I can’t really find the data. The spec you’re referring to is for the older 737-800.
It suggests an overall savings of ~14% over the 737-800 but doesn’t look at specific takeoff/climb comparison.
I wasn’t posting the LLM output as a source of truth. I was just using it to question the uncited value. And I still really don’t know the answer. If you’ve got another data source I’d love to get it.
Why do people keep insisting on pasting LLM output to HN when every time it happens, it gets downvoted to oblivion? The community clearly doesn't want it. If we wanted to know a computer program's opinion about something, we could ask it ourselves.
I was using it to question that exact stated fuel consumption number without a citation. For hard data (like fuel consumption) getting a value from an LLM isn’t absurd.
If not absurd, it's very poor form. You should never use LLM as input for a discussion, nobody wants to hear that. Use it to search for authoritative sources.
It’s fine if you post an actual citation that you might have found through the LLM. Just posting AI slop is worse than useless, though, and also unpleasantly dystopian.
That’s the point? I wasn’t suggesting it was correct. Just that the value is wildly different from their own non-cited number. The next stage was to get a citation from an actual datasheet. Their reasoning was nothing beyond “I’ve read”
That could be. We just don't know right now, but your intuition may well be correct, even if there is a single root cause there could very well be multiple contributory causes.
They are not a failure of the original plan, they are a mandatory component of the original plan that if everything is nominal never gets executed. Every pilot on approach is ready for one or even more go-arounds and they happen quite frequently for a variety of reasons.
They happen a few hundred times per day at ~100 k flights.
How much extra do you need? Enough that a pilot/crew doing their job properly will never run out of fuel and crash.
So yes they will do an "investigation". It's not a criminal investigation. It's to understand the circumstances, the choices, the procedures, and the execution that ended with a plane dangerously close to running out of fuel.
This will determine if there were mistakes made, or the reserve formula needs to be adjusted, or both.
Don't tell me about cost, just stop. Let MAGA-Air accept some plane deaths to have cheap fares.
Could have, but pilots practice no fuel landings all the time (in simulators). If they can get to ground that is "level enough" nobody dies. It is not something you ever want to see in the real world (and in the real world people often do die when it happens), but it isn't automating people die.
I don't think that's all that true for airliners. Pilots definitely practice for engine-out scenarios during all levels of training up to the airlines, but the ability of a plane the size of a 737 to safely land on anything but a runway is...limited. And if you're low, slow, and trying to go around, that's not a lot of time to glide to ground that is "level enough".
Pilots are ultimately responsible for the aircraft, that's pretty much set in stone but if ATC would tell them to divert they would unless there already was an emergency.
Well clearly that number should depend on distance to next airport and how much fuel is onboard. It isn't sensible to have a set number when other parameters change.
This reminds of discussions following the Fukushima disaster where one commenter claimed that it wasn't a design flaw, because it was an extraordinary circumstance. I found this appalling, because I do not at all think that was the risk profile that was sold to the public; I think people believed that it was supposed to be designed to safely survive 1000-year earthquakes and the tsunamis that they create.
Likewise, I think that the flying public is lead to believe fuel exhaustion is so rare that when airlines are compliant with regulations, no such disasters across all flights across all carriers will occur during your lifetime.
It's also a communication problem, because labels like "100-year/1000-year event" are easily misunderstood.
* they're derived from an estimated probability of the event (independently) happening each year. It doesn't mean that it won't happen for n years. The probability is the same every year.
* the probabilities are estimates, trying to predict extreme outliers. Usually from less than 100s of years of data, using sparse records that may have never recorded a single outlier.
* years = 1/annual_probability ends up giving large time spans for small probabilities. It means that uncertainty between 0.00001% and 0.00002% looks "off by 500 years".
I find a useful exercise is to have a cheat sheet of historic flood heights in some area, tell someone the first record high, ask them how high they would make the levee and how long they think it would last. Peoples' sense for extremal events is bad.
That's a great exercise. Where I live a lot of people died because in the past we were not able to make that guess correctly. A lot was learned, at great expense.
6 min, is empty, 6 min is purely theoretical, 6 min would not clear for ground handling or a test start, or a fuel system check,6 min would not do a go around.
will interesting to see if they release info about what the real amount of fuel left is, and an authorative discussion on how much useable flight time was there.
did they actualy make the taxi to the terminal?, or run out on the apron?
Yes. There is another comment above making light of the 6 minutes as if another go-around was still an option, that is a ridiculous take. They were going to bring that plane in and land it no matter what on this last run, otherwise they'd crash for sure. 6 minutes may not even be within the margin of readout.
By your logic you need an infinite amount of fuel.
If you define X the amount of fuel you need after you land.
And you say that X needs to be enough to make an emergency landing.
And we define that the amount of fuel required for an emergency landing should cover the amount required for the landing operation while still having X in the tank when landed.
X > X + landing_cost
The plane already had made 3 failed attempt before and was redirected to two different airports.
Naively as an outsider, this situation seems like everything worked as intended?
I don't remember all of the rules off the top of my head, but if you are ever landing with less than 30 minutes of fuel, something has gone seriously wrong. You are required to take off with sufficient fuel to fly to your destination, hold for a period of time, attempt a landing, fly to your alternate, and land all with 30 minutes remaining. If you are ever in a situation where you may not meet these conditions, you are required to divert immediately. In choosing your alternate, you consider weather conditions along with many other factors. This was, without question, a serious emergency.
From the very brief description in the article, I would say they should have diverted to Manchester at least 25 minutes sooner than they did. I will include the GP's caution, however:
I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
If you are ever in a situation where you estimate you will land with less than 30 minutes of fuel, you are legally obliged to declare a MAYDAY. One of the few situations where a mayday is legally required.
My understanding is that they shouldn't have spent that much time in the air (not intended as a guess for the cause). The margin is there for situations where you can't land earlier, not the margin for scheduling the landing. There is margin for expected potential delays, they were in the other margin that should never be used except in true emergencies.
Oh I think I see; so is the question not “why did they land with so little fuel”, but more like “why did it take so long to decide to redirect to a known-safe airport”?
Possibly. Or 'why did your fuel readings deviate from what was actually in the tanks' or 'why did we leave with less fuel than we thought we did' and so on. There are so many variables here speculation is completely pointless. All we know is that something went wrong, that it almost led to a crash and that it involves an airline with a very good record when it comes to things like this.
I don't know. As the parent said, I'd be careful with guessing the root cause right now. They should not have been this low even if diverted due to weather.
If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call.
Mayday is a term enshrined in law. It is only to be used when people will die if you do not receive help. In the US, calling it inappropriately can be punished with up to 10 years in jail and a $250k fine. It's protected in this way because as soon as you call mayday, in many situations there are actions that must be taken by law or regulation. Other appropriate uses include things like "our plane is on fire" or "our wing just fell off and we can't steer the plane".
As soon as you think you can't land with the fuel reserves you are _required_ to call mayday, other pilots are _required_ to clear the radio for you, and ATC is _required_ to provide any and all supported possible until you're on the ground.
The investigation is not to figure out who to send to jail or something. The investigation is because a flight just came this >< close to having hundreds of people die. That fuel is there as a safety margin, yes. That's how everyone ended up walking off this plane instead of dying as the plane was ripped apart by some trees somewhere. That is good.
But air travel did not become as safe as it with an attitude of "this hasn't killed anyone yet, all good". The fact there was an incursion into the safety margin should not be looked at as "eh, working as intended" but "holy hell we just came this close to disaster, what went wrong that almost killed all these people? how do we stop that happening again?". That is what an investigation will be looking to figure out.
To put it in vaguely IT terms, this is something like... your application has started corrupting its database, but you have _a_ backup copy. On one hand, you can think "eh, we have a backup, that's what it's there for, who cares". On the other you can go "holy shit, any time we need to restore from the backup we narrowly averted disaster... how do we make sure we're not in that situation again?". The former is probably going to lead to irrecoverable data loss eventually. The second will have you addressing problems _before_ they ruin you.
What is fascinating about this whole discussion is that the general world of software development is so far away from actual engineering that all of these basics require painstaking explanation.
> If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call.
From the article, they did issue a mayday call, when the closest airport was presumably Edinburgh. Then they flew to Manchester and landed.
>One pilot who reviewed the log said: “Just imagine that whenever you land with less than 2T (2,000kg) of fuel left you start paying close attention to the situation. Less than 1.5T you are sweating. But this is as close to a fatal accident as possible.”
Only issue I see is that should there have been stricter rules to diverting way earlier. If winds were such as to make landing harder. Would just directly going somewhere else been the correct choice to force.
Well, if you know you're pretty low on fuel, you are likely to pick an airport where the weather is good, rather than risking three more missed approaches at a closer one where the weather is probably also bad.
Of course, Manchester is also a Ryanair base. There are two Ryanair bases closer to Prestwick (Edinburgh and Newcastle), but maybe the weather was bad there too? If the fuel situation was so dire, questions might be asked during the investigation why they didn't pick a closer airport with good weather that wasn't a Ryanair base (if one existed), but ultimately it's the pilots' decision to fly a bit further to an airport they are familiar with, and second guessing them with the benefit of hindsight is probably not a good idea...
They made two attempts to land at Prestwick, then diverted to Edinburgh (which also had bad weather). After one attempt at Edinburgh, they then diverted to Manchester.
> I’m a little confused by what there is to investigate at all.
So because the safety margin still worked while down to near vapors we should conclude there's nothing to learn for the future to reduce the risk of similar incidents?
Flight from Edinburgh to Manchester is just a bit more than 1 hour, so after trying 2 landings, diverting to Edinburgh (15-20 minutes flight), 1 more landing attempt, well, you get very close to 2 hours.
Whether it can be prevented in the future. Should planes fly with even more reserve fuel? It's possible. Or maybe different ways of selecting alternate landing sites?
It may even be the answer is "no, everything went as well as it possibly could have, and adding more reserve fuel to every flight would be unacceptably wasteful, so oh well", but at a minimum they'll probably recommend even more fuel on certain flights into risky weather.
Similarly naive outsider, but I've read things here and there. My understanding is that they should have declared mayday (emergency) and landed (potentially at another airport, potentially in the middle of nowhere) _way_ before so that when they have landed they still had 30 minutes or more of fuel in the tanks.
Imagine you're standing on a balcony and discover that the supports are cracked almost all the way through.
Do you shrug and say, that's why they have a safety factor, everything worked as intended? Or do you say, holy crap, I nearly died, how did this happen?
The purpose of the safety factor is to save you if things go badly wrong. The fact that it did its job doesn't mean things didn't go badly wrong. If you don't address what happened then you no longer have a safety factor.
I think a more insightful answer is how often is it acceptable for the reserves to actually be cut into. If this was happening often, then there’s a likelihood of a future disaster. As it is there is 1 isolated case that still ended with a positive outcome. I think it almost adds support for the current reserve levels to be pretty dialed-in.
Officially: never. Unofficially, a minute or two would be cause for concern and the regulators would most likely be showing an interest. The airline may have a higher margin than the official one. This is exceptional, they were within the margin of error on readout and the pilots must have known that. It's one thing to know you have half an hour of fuel give-or-take in the tank it is another to know that give-or-take you are running on fumes.
The answer is 'never' as the reserves are only added for worse-than-worst case scenario, i.e. in this case something went literally unimaginably (as of then) wrong.
Our definition of 'bad weather' is definitely changing as we gather more data.
Besides regular weather (which airliners aim to avoid except during take off and landing) there are many other factors at play here. There are several almanacs that are used for fuel calculations & navigation, they are updated annually.
The fastest jet stream (the aviation equivalent of the trade winds) recorded is north of 400 Kph, having that with you, against you or perpendicular to your flight path will have a substantial influence on fuel consumption and flight duration.
I agree with you that it may well end up with a regulatory change but that's one of many possible outcomes here. I will definitely keep an eye out for the report on this flight's investigation. It is going to make for very educational reading.
Anything less than 60 minutes would be looked at by the airline, anything less than the legally required amount (30 minutes for a jet of this type iirc) will result in a very serious investigation. Note that for slower aircraft (for instance a turbo-prop) the time requirement goes up not down because they may have to spend more time in the air to reach an alternate (or secondary alternate, if things are really bad, like what happened here).
One of those YouTube channels where a professional pilot evaluates flying incidents had a similar incident when the pilot started yelling at the tower when they tried to make him go around again. He essentially said he would declare an emergency if he didn’t hear different instructions. I think he had 10-15 minutes when he touched down.
One of the things the reserve is for is if the plane immediately in front of you fucks up the runway, you now have to divert to the next airport. You need at least enough fuel to get there and for the tower to shove everyone else out of the way so you can make an emergency landing.
There are other reasons someone could abort a landing and have to go around again, besides debris in the runway. And sometimes two of them can happen consecutively.
In the case I’m referencing, it was pointed out that p the pilot made things worse by going faster than he was told to fly, using up fuel and also making him too close to a previous plane which forced him to go around the previous time, so it wasn’t all the tower.
I have known former air traffic controllers that won't fly certain airlines because of a notorious habit some have for queue jumping by claiming they're low on fuel. If they are low on fuel is something else, but in any case when the ATCs have noticed a pattern then something is up.
This situation sounds a lot less nefarious, but it does also sound like they should have rerouted earlier.
Since there's a lot of confusion in the comments below I'm going to hijack one of the top comments to make a couple points clear from the article and FlightRadar24 data: [1]
They did reroute earlier. It was 2 failed attempts on Prestwick (Glasgow), 45 minutes in the landing pattern, then they diverted to Edinburgh (15 minute flight), a failed attempt at Edinburgh (~5-10 minutes), and then they diverted to Manchester (45 minute flight) and landed successfully there. Likely they hit their reserve just as the Edinburgh landing failed and decided to fly to Manchester, with clearer skies, rather than risk another failure in their reserve.
IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately. But this is somewhat understandable: first of all, dropping the passengers off at Edinburgh (an hour drive from Glasgow) is significantly less costly and less inconvenient than dropping them at Manchester (an overnight bus ride). Second, if the Edinburgh landing had been successful they would not have eaten into their reserve and no investigation would've been needed. Third, the Monday-morning quarterbacking could've easily gone the other direction if they had diverted to Manchester ("Why did you choose an airport 178 miles away and risk eating into your fuel reserve when Edinburgh was right there?")
> IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately. But this is somewhat understandable: first of all, dropping the passengers off at Edinburgh (an hour drive from Glasgow) is significantly less costly and less inconvenient than dropping them at Manchester (an overnight bus ride).
Yeah, as someone who knows next to nothing about airlines, but has seen these type of decisions in businesses, this was the thing that stood out to me. This is all pure speculation of course, but I'd be curious how clear it was that Edinburgh would also have a high risk of being unsuccessful and whether the pilots felt any pressure to try that anyway. E.g. are there consequences for pilots who cause delays for passengers?
Quick note that Preswick is not really Glasgow (35 miles away) and Glasgow has its own airport which presumably was also affected by the same weather so they couldn't divert to that. Between the Scottish lowlands (where they had already tried all the commercial airports) and anywhere else, Manchester is about the closest option.
As someone totally ignorant of British airports, a Google maps search for "airports northern england" shows Teesside, Carlisle, and Newcastle all significantly closer to Edinburgh than Manchester. Are these not places where a 737 under emergency could land? Or was the weather also bad there?
Carlisle is small (and not currently licensed for public use) - not an ideal place to drop a 737 if there's a choice. It's also not that far from Prestwick so may have had similar weather. Newcastle and Teesside are both on the East coast and likely to be affected by similar weather to Edinburgh given the storm coming in from the North East. The next closest will be Manchester or Leeds/Bradford, with Manchester being larger, closer to where passengers want to go (Glasgow) and further away from the storm.
There's precedent for this kind of situation to generate quite extensive investigations. An incident in 2017 where a flight from the Isle of Man to Belfast was unable to land in a storm, diverted back to the IOM, then landed in unsafe weather conditions because of insufficient fuel to divert again got a 48 page report[0], safety recommendations, and the airline being banned from the UK.
That's likely, these places are not very far apart, and weather systems that cause 100mph winds don't tend to be small. And presumably if you have at most one landing attempt remaining you don't want to be taking any more chances.
> IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately.
The decision will have been made based on the forecast weather at Edinburgh prior to the flight (that is used to select a suitable alternate), and the actual reported weather at the time. Both the forecast and actual weather are precisely reported in an aviation weather language ("TAF" and "METAR") and assessed objectively. The investigation will certainly consider if the pilots erred there. Mostly likely the outcome will be that the decision was the correct one given the weather information they had available to them - this is what has been found in similar previous incidents.
At the point they left it, they still had about an hour and 20 minutes of fuel remaining, with an alternate airport 20 minutes away. They had not declared an emergency, so they were in with any other traffic waiting for takeoff and landing. (Which does make me wonder, did any other planes try to land at Prestwick at the time and how did they fair?)
Claiming you're low when you are not is going to cause a major headache for the PIC, they're going to have to write that up and they may well be investigated. If it turns out they were lying they would likely find out that that is a career limiting move and if it happens too often then that too should result in consequences. The main reason is that your fake emergency may cause someone else to have a real one.
When you declare a fuel emergency or even urgency, there's often follow up to figure out why (mechanical issue? problem with dispatch? problem with flying technique? exceptional weather condition that could be forecast better? etc). And there is plenty of data in aviation to know what happened.
Dispatch knows how much fuel they say they put in.
Your flight time, speeds, and profile are known.
ACARS may be reporting fuel use throughout the flight.
Random spot checks. Every day at every airport some of these will get verified. Also, the next pilot would have to be willing to cover for you because they are going to have to falsify their records to make your trick invisible. You record the amount of fuel in the tank when you take command of the aircraft, the amount of fuel that was loaded and from that it is trivial to compute how much was left the last time it landed.
When someone accepts the writeup, there's a random chance it's selected for followup. If/when they discover there was enough fuel, it will affect the career(s) of person(s) involved.
First, generally, people don't like having to do paperwork, and especially don't like doing paperwork to help you land a little quicker.
While one time may not be a fireable offense, you will find you career affected in the number of ways people can find to be uncooperative with you, or not support you when you attempt to advance your career within the company.
Developing a habit would lead your interlocutors to escalate the situation, which would lead to discipline up to and including the company firing person(s) involved.
Edit: I was recalling articles claiming the company purposely fueling less than other airlines in order to increase their rate of claims for priority landing to have a better "on time" statistics.
Having attended meetings at ICAO I can also tell you many details of various aviation incidents, including their existence, are covered by some secret classification. This fact being disclosed caused most of the attendees to lose all hope in the rest of the proceedings. To their credit the FAA reps on that occasion were by far the most reasonable gov representatives in the room, and the FAA are one of the major voices pushing for greater transparency on it.
It’s generous of the classifying authority to send to the ICAO meeting somebody both appropriately credentialed to know about the information in question, and willing to talk coyly about it. Did these additional incidents inform the policy discussions at the meetings you attended?
It's funny you say that, because the way it happened was it was blurted out by a diplomat from a certain country, at which point most of the regulators facepalmed and all of those of us from outside were having the same reaction as many here.
The whole subject of discussion prior to this was efforts to improve data sharing wrt incidents.
Second guessing a pilot saying they have a problem is a really bad idea. ATC second guessing an emergency is a really bad idea. Making a pilot explain why they're actually low on fuel, despite whatever some computer is saying, instead of focusing on flying the plane is a really, really bad idea.
Also, that sort of telemetry does exist for most major airlines, however it goes via satellite to the airline not the ATC.
I am not saying you are wrong, but both Type I and Type II errors are problematic. What if the pilot is wrong?
Korean Air Flight 801 could have used someone 2nd guessing a pilot. They didn't until they were almost dead and then it was too late. Not 2nd guessing the pilot was a really really bad idea.
If the pilot is wrong you hope the copilot or someone else on the crew picks up on the error and corrects it. If they’re both wrong, or if they don’t feel empowered to challenge the pilot like in Korean Air 801, everyone is usually fucked.
ATC doesn’t have the kind of situational awareness or manpower to fix these kinds of problems the vast majority of the time. It only seems like they could have done something after the fact when the disaster has already happened and hindsight activates.
Like the GP said, ATC second guessing pilots is a really, really bad idea. A few incidents doesn’t change that.
> Korean Air Flight 801 could have used someone 2nd guessing a pilot.
...yeah, the second pilot. And in this case, also flight engineer.
IIRC The problem was pretty much aside from errors the cultural issues with pilots, the "lower ranks" wouldn't dare to be assertive to seniority and just voiced the issues they saw without doing anything.
I expect that they take the pilot's word in case of a rare situation [1] and then make the fill a ton of paparwork to try to solve the main cause and also discourage lies.
[1] In one case someone mixed imperial and metric unix, and instead of $something-kilograms, they put only $something-pounds of fuel.
This incident is known as the Gimli Glider and was actually due to multiple failures before the pound-kilogram issue (and the backdrop of Canada's then-recent metrication) even became relevant: https://en.wikipedia.org/wiki/Gimli_Glider
Minimum fuel requirements are calculated as "Time of fuel for cruise to certain points", which is usually good enough, but if an Airport is stupid busy, or has bad wind patterns, just a couple go-arounds will chew through your fuel way faster than the regulation expects.
Turbofan engines are also dramatically less efficient at low altitude than high altitude cruise. So holding at low altitudes because a congested airport is dealing with traffic will chew through your reserves much faster than you expect.
Ryanair flies short hops to congested airports. They will have relatively low reserves, and you should expect them to run into "Hey we are low on fuel" more often than international flights for example.
I mean, obviously, it's better to trust the pilots, but if they are jumping the line because "fuel low" when it's not low, well, they're not being very professional, are they?
It wouldn’t change anything. The line between a “mayday - fuel emergency” and any other flight waiting for a landing slot is crystal clear. Of course, in low-but-not-emergency fuel scenarios the pilots can request priority, but the ATC don’t have to oblige them.
It is almost fascinating how humans will stoop to dishonesty even in banal situations - and not just any humans, but pilots, who should be subject to at least some vetting.
Maybe planes should be retrofitted as to transmit their actual fuel state including a qualified assessment in minutes to the ATC. Not just because of the cheaters, but also to warn the ATC in the rare case that some plane crew isn't very assertive about their dwindling fuel, or hasn't noticed the problem.
It would make prioritizing the queue a bit more neutral.
If I designed such a system from scratch, "remaining fuel" would be part of my telemetry.
This is provable, though (there are regulations that say how much fuel you must have at takeoff - enough to divert comfortably to a suitable airport + some reserve for circling), and could be heavily punished. Up to the withdrawal of necessary licences.
And the reason why those fuel reserves exist is to be a guard band allowing situations like this to happen without flames, wreckage, and death.
Having worked with many US airline pilots over the years, this is also why they are so proud to be unionized. Sure, senior pilots make as much as some FAANG developers, but the union is also there so that management doesn't get bright ideas about things like cutting fuel reserves to cut costs without the union telling them to stuff it.
Management can't cut fuel reserves, not because the pilots are unionized but because there are some very strict rules about these fuel estimations prior to take off and margins be damned. And those rules are exactly there because otherwise this kind of incident would happen far more frequently. But it's regulation that is the backstop here, not the pilots.
The point is that the unions are there to allow the pilots to advocate for all kinds of safety-of-flight related things like fuel reserves, crew rest, and so forth that management would be happy to cut to save money. And to do so without fear of retaliation.
And if you don't think the airlines would love to lobby Congress about the regulatory backstop, well . . .
As I wrote elsewhere in this thread I actually wrote software to estimate the amount of fuel a jet should load to comply with the rules. This was commissioned by the airline and they were scared shitless that they would ever be found to be in breach of the regulations on this aspect. It is one of those red lines that you really do not wish to cross. There are other aspects of flight where you are right but this particular one is different.
The main reason why airlines would like to take the least amount of fuel is because it immediately increases payload capacity and thus flight efficiency. This being a cut-throat market there is a serious incentive to cut it as fine as possible. So the regulations around this particular issue are incredibly strict: you have to have a certain amount of fuel left upon landing, you have to write up truthfully how much you still had left and you will be investigated without fail if you cut into the reserve. The good thing about unions here is that they help to make sure that pilots know they are safe reporting truthfully because the airlines can not retaliate if they would pressure the pilot to not report an incident (which all pilots would normally definitely do). So they're a factor, but it is the regulator that writes the rules here and they are super strict about this.
And that's immediately why the calculation of the estimate becomes so important: you now have 30 minutes (or 45, depending) of deadweight + the deadweight for two alternates and an x amount of time in a holding pattern, plus up to three go-arounds. That really adds up, so you have to do your best to get the calculation as close as possible to what it will be in practice without ever cutting into that reserve.
It took me the better part of a year and massive amount of learning to write a small amount of code + associated tests to pass certification. It also taught me more about software engineering (as opposed to development) than anything I did up to that point in time and it made me very wary about our normal software development practices.
As an aviation fan just reading this thread is quite eye-opening in terms of how much risk tolerance the average commenter has vs what is standard in the aviation community and on aviation forums. It's almost like peeking into two different worlds. I wonder if there would be any value in teaching an "engineering when lives are on the line" or "war stories from accident investigations" classes to new engineers. I feel like there's value in appreciating just how much more work goes into building a system where people's lives are at stake.
Yeah it bothers me to no end with the "engineering"-inflation of various jobs.
Like, I'm definitively not an engineer, nor does my day job really involve engineering, yet my title contains Engineer! I'm a proud CRUD monkey and designer.
I have done engineering work previously when developing hardware, and it's really a different mindset (even in an agile & fast-moving engineering org). Safety, cost, reliability, multidisciplinary integration, etc. just don't really come up in a lot in web and app development (which is a wonderful thing, really—I love it!)
It is an endless source of frustration to see poorly engineered software solutions powering critical systems.
> I wonder if there would be any value in teaching an "engineering when lives are on the line" or "war stories from accident investigations" classes to new engineers.
There would be immense value in that. But who is going to pay for it? It's a course that will essentially cause your crew to start producing software at 1/10th the rate they would otherwise do.
The average commenter here is a software guy. I imagine for the average software guy a Master Caution would be like a minor compile-time warning, i.e. feel free to just disregard it. :)
I think the literal fear of death _might_ be motivation enough for pilots to advocate for safety? And if they want to fire you, would you want to work for them anyways?
> I think the literal fear of death _might_ be motivation enough for pilots to advocate for safety?
You'd think, but individual humans are very very bad at estimating risk, and in toxic group and work situations, humans will often take on increased personal risk rather than risk conflict. I.e., they will value group conformity over their own safety ... especially if their paycheck is involved. Fear of death is not nearly as powerful as robust regulation and unions.
The union is a nice backstop for issues around the edges that come up with corporate, but the real backstop is the pilots’ licensing. By making them directly responsible for the plane as PIC, it gives them leverage over their employer that few other professions have. AIR-21 gives them significant protection from retaliation and the ASRS is confidential. ALPA helps them navigate that mess if it comes to it, but that’s the real legal backing that pilots have.
Same thing happens with Professional Engineers regardless of whether they are employed or work as independent consultants/firms. They’re legally responsible for the bridges and other infrastructure they sign off on with laws protecting them from employers and clients.
(I fully support the ALPA and other unions, I just don’t think it plays as significant a role in following regulations as you claim)
...that regulation is text in a database. It can be changed capriciously at any moment, like they often are.
It takes people with ideas and a willingness to put pressure in the right places to be sure that sane policies prevail.
I think it's pretty obvious that as time moves forward, we need to rely on "regulations" less. The root and history of the word in the political context is to make things regular. But state actions increasingly bring irregularity to the world.
It seems absolutely fair to say that, in this situation, the people - the pilots in particular, but also cabin crews, ATCs, engineers, and their unions, are the backstop worth observing and celebrating.
If you land with less fuel than the legal minimum you are going to have a lot of explaining to do, there will be an investigation and you, the pilot and the airline will get enough headache from it that you will make bloody sure it does not happen again. The pilot(s) may not be able to fly until that investigation has run its course, the airline may get fined or warned if this is the first time it happened. In an extreme case the pilots may lose their license.
> It seems absolutely fair to say that, in this situation, the people - the pilots in particular, but also cabin crews, ATCs, engineers, and their unions, are the backstop worth observing and celebrating.
I will hold off on that conclusion until the report is in. There are so many possible root causes here that speculation is completely useless, and celebrations would be premature.
My apologies - I didn't mean to speculate about this incident in particular, but about the general role of so-called "regulation"; I thought it was unfair to minimize the role of the people and unions compared to the (in my view, comparatively flimsy) legislation.
I think the thing that's being pointed out as overlooked when praising the employees and the unions, is the regulators, who are the people who play a very large part in making sure that the regulations are enforced. The regulations are just text in a database, but it's the regulators who actually make it happen. A pilot who wants to push back against a beancounter cutting corners has a union and a regulatory agency to back them up.
Yes. I think the average bus and train driver is completely underappreciated as well and they have a massive responsibility too. I know I could not do their jobs, it would weigh on me too much.
> I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
Just watch Juan Browne, he usually turns out pretty good in analyzing the mishaps. He didn’t upload anything for Manchester yet but will probably soon: https://youtube.com/@blancolirio
I'm also a Blancolirio subscriber. Juan also doesn't try to get ahead of the investigation, really. It's part of what makes him a valuable voice in the space.
I remember this stuff being a bigger story for a short moment x years ago, where low cost carriers (it might have been Ryanair then, too) routinely flew with unreasonably small amounts of "backup" fuel and had to declare emergencies in order to get on the ground safely.
I guess they're trying it again now that the whole thing had blown over.
3 go arounds + 2 hours in a holding pattern should result in at least 45 to 60 minutes left in the tanks after landing. Depending on the kind of aircraft that can be a pretty impressive amount of fuel.
> Does the estimation change depending on weather forecast, season of the year etc?
Yes. There are many factors that go into this including trade winds (which vary quite a bit seasonally and which can make a huge difference), time of day, altitude of the various legs, route flown, weather, distance to alternates, altitude of the place of departure and altitude of the place where you are landing, weight of the aircraft, engine type, engine hours since last overhaul, weight of passengers, luggage and cargo, angle-of-attack and so on. The software I wrote was a couple of thousand lines just to output a single number and 10x as much code for tests, and it was just one module in a much larger pre-flight application.
The test suite was much larger than the code. It took ages to get it certified, the calculations had to be correct to the last significant digit on reference problems to prove that the algorithms had been implemented correctly. This caused a bit of a headache because the floating point library that I used turned out to be slightly different than the one from the benchmark.
There are three different kinds of jet fuel and all are produced to strict standards, and then there are allowances for ppm water contamination (very low, to ensure the fuel system will never freeze at altitude or in freezing weather on the ground or at lower altitude).
This honestly makes me think that we're missing a trick if an option for this sort of circumstance can't be "send a military fuel tanker up to refuel them in air" as a last ditch emergency measure (which IMO you would've triggered in this exact scenario).
The argument in favor is simply that we need in air refueling for the military, but justifying all that expenditure is a lot easier if it's dual use technology.
Isn't midair refueling notoriously difficult to get right? The headlines would become "airliner crashes after crew couldn't thread the needle for 45 min"
Yes. Even not forecasted storms in the form of a probability of wind at low altitude when the engines are at their least efficient. And tradewinds at altitude, which are quite variable as well.
Under FAA rules this was a screwup. [edit: see my own reply] (However, the rules are subtle, so they can be partially forgiven.) However, I'm not only a dispatcher but also a philosophy BA, so I've found a good way to explain it.
Your reserve fuel (the "extra" fuel over what the actual flight burn) can of course be used (hello, that's what it's there for) but—and here's the rub—you can never plan on using it.
That is to say, in this case, when they missed their first or second approach, they CANNOT say, "We'll use our reserve fuel and make another go at it" because that would be intentionally planning to burn your reserve.
You may only dip into your reserve when you have no other choice. In this case, when the only fuel they had left was reserve, they are obligated by law to proceed to the alternate airport, which clearly they did not do [correction: they did do the proper thing; see my 2nd reply below]. No bueno.
[this is a slight simplification (minor details omitted for brevity) but the kernel of the issue is properly described]
Update: OK, if *Edinburgh* was their alternate and they missed there and were then forced to bugout for Manchester, that's then an example of when reserve is OK to be burned. (The 'slight simplification' I omitted was unpacking how the alternate fuel plays into the process, but here, that was a key part of the series of events.) That's what I get for not reading TFA first :-/
Not really, you should have enough fuel to make it to multiple alternatives or make emergency landing somewhere else. You should never burn that last 45 mins unless you want to make the news and file a lot of paperwork.
The regs are quite specific on if and when we need an alternate, which is weather dependent, and what your fuel requirements are. And we don't really have the idea of "multiple alternatives", but I guess it's implied by the additional reserve - what us Americans call a reserve or the Europeans call "final reserve". In case you're curious, we use the TAF (termimal area forecast) to determine if we need an alternate, and use a 1,2,3 rule which is 1 hour before and 1 hour after arrival time we need ceilings of at least 2000 ft and 3 statute miles of horizontal visibility.
I'm curious why you did that? It's not a very complicated sequence. The whole point of engaging in a discussion here is to think about the issues raised and offer a point of view while incorporating other perspectives into yours. You've spent your money to bypass the whole intent of this site; akin to you being hungry then sending someone else to a restaurant for you so you can later read their review of the food.
EDIT and you of most of the commenters here, with your industry background, are better placed to offer an opinion!
Why? I saw no upside to reading a layman's media source and teasing out the sequence, which is all I wanted to know. I read NTSB reports for pleasure and my favorite YT creator is Blancolirio. There's an infintesimal chance that the story had any juicy details I cared about. Also, it was work hours and I really didn't have any more time to devote to topic. I was in a rush to get my take out there, since I am a legitimate SME.
Presenting information in different ways is useful (and the method of display can offer informational insights itself). And for different users it might help parse larger connections. And by using the LLM to summarize just that one facet of the problem (itinerary and sequence) and sharing it here, they’ve contributed in a meaningful way. It may not have warranted a response. But it added to overall understanding of the problem space to help facilitate discussion. And they did well enough by citing that the info came from an LLM. They didn’t bypass the intent of the site. They added to it and fell right in line with that intent.
I had no issue with the contribution itself, the route summary is helpful.
> And they did well enough by citing that the info came from an LLM.
In terms of acknowledging AI contribution, you're damned if you do, damned if you don't. Here it's sidetracked a discussion; but transparency is better than otherwise I suppose. Perhaps it just boils down to taste - and I don't like it.
You also made me think. I think the problem lies in the nature of “threaded” discussions. The information was useful, but it wasn’t necessarily a “reply” to any particular comment. But, the design here leaves no other choice when adding it. It maybe doesn’t make sense as a top-level comment either. It’s almost like we need to have…side comments? Asides? Like a place to just drop in relevant tidbits and informational helpers rather than a true “comment”. Maybe it’s as simple as having a means to turn off replies to signify that a contribution was an “relevant aside”.
But yes, in a perfectly meta way, I think we’ve both thought more about the nature and design of web comments and information and the implications of LLM-assisted chat ‘augmentation’. (All those AI summaries forced upon us in every site is probably the worse implementation of this!)
Even though I’ve read the entire article, I found it very difficult to mentally visualize and ended up not noticing that there were three destination airports involved.
Not necessarily. And I get that you've caveated yourself with an edit and a reply etc, but lets assume that you're not hedging for the moment.
They carried required reserves on departure. Multiple approaches thwarted by extreme unforseen weather. They declared Mayday Fuel, which is mandatory under EASA regulations, when reserve fuel use became unnavoidable. They diverted to the nearest suitable airport.
Landing with 220kg is close, but within bounds of a declared fuel emergency.
Crew decision to declare Mayday and divert was proper airmanship, not negligence.
Yes, reserve fuel may not be planned for. But it may be used. It's there for a reason. Your accusation doesn't account for dynamic evolving weather and realtime decision making.
I'm an instrument rated pilot and an advanced ground instructor under FAA and I fly IMC in bad weather as single pilot IFR around the pacific northwest and colorado.
Was this good/bad? Idk Room for improvement? Maybe? Clearer direction with the benefit of hindsight? Maybe. but the majority of the sentiment in the responses is coming from people not type rated in a 737.
> That is to say, in this case, when they missed their first or second approach, they CANNOT say, "We'll use our reserve fuel and make another go at it" because that would be intentionally planning to burn your reserve.
Is that what happened? That's not in the article, what's the source?
And other comments here are saying the third attempt was in Edinburgh, so they were already trying to land anywhere possible by the third attempt.
At what point are you saying they chose to plan on using reserves when they still had any option for landing without reserves?
Similar philosophies but with differences. e.g. FAA reserve requirements is destination + alternate + 45 mins reserve. EASA is destination + alternate + final reserve which is 30 mins holding for jets and 45 mins for pistons IIRC. But in both cases it's that idea of a destination, an alternatite, and additional. And then there's the requirements around whether you need an alternate, etc.
Looks like they tried two attempts to land in Prestwick over two hours, then flew to Edinburgh and made one aborted landing, then finally went to Manchester.
What a nerve wracking experience for those pilots. I wonder if on the final attempt they knew they had to force it down no matter what.
Per the FlightRadar24 logs, it looks like only about 45min was wasted over Prestwick, not 2hrs. First approach was around 18:06, and they're breaking off to head for Edinburgh by about 18:51.
If there's considered to be a mistake here though, I'm guessing it's going to be spending too long before committing to the initial diversion.
Without knowing the weather they were seeing at the time, seems hard to say if they should have gone for a closer 2nd alternate than Manchester.
I don't think we know yet when min fuel was declared. At that point, they will be resequenced. Then we need to know when mayday fuel was declared. It sounds pretty odd, like perhaps there were multiple simultaneous situations and the crew did not have adequate information.
About 5 years ago before ATC recordings became mainstay on YouTube, there was an American pilot that declared an emergency at JFK and very firmly said "we are turning back and landing NOW. Get the aircraft OFF all runways".
He was low in fuel and also frustrated with Kennedy ATC because he declared "minimum fuel" earlier and was still getting vectored around. (I know "minimum fuel" is not an emergency and has a very precise meaning).
They must have been very close to running out. But it was a valuable lesson learned in speaking up before you get to that point.
I’m guessing that pilot had also been taught the lesson of Avianca 052, which crashed at JFK because the FO / captain did not explicitly declare a fuel emergency.
JFK ATC in particular has an enormous workload with many international flights, combined with direct, even conflictual at times, NY communication style. It puts the onus on the pilot for conveying the message to ATC, rather than ATC for extracting the message from the pilot.
> But it was a valuable lesson learned in speaking up before you get to that point.
I'm not sure it was a lesson learned per-se because the captain was merely doing his job as fundamentally defined.
A captain has ultimate responsibility for the aircraft.
However there is a side question in relation to your post...
When you say "declared an emergency" in your post, the more interesting question would be whether it was actually formally declared by the captain (i.e. "MAYDAY") or whether the captain was merely "working with" ATC at a lower level, maybe "PAN" or maybe just informal "prioritised".
If the captain DID declare "MAYDAY" earlier in the timeframe then yes, Kennedy would have a lot to answer for if they were spending excessive time vectoring around.
But if the captain did not formally declare and then came back later and started bossing Kennedy around, that would be a different set of questions, focused on the captain.
> The word Mayday is not required to declare an emergency.
That may be so in the US.
But it is a bad habit to pick up.
Especially if you are an airline pilot and you frequently fly to destinations where English is not the first language.
Or indeed in US airspace where you frequently get international carriers flying in and out.
There is a reason why there is internationally agreed standard phraseology for radio communications.
Everyone learns MAYDAY/PAN and the associated expectations around it (e.g. radio silence etc. etc.)
Not everybody will be able to adequately follow along if you have a long drawn-out waffle discussion over the radio ... "we have a little problem" ... "do you want to declare?" ... "oh wait, standby ...." ...."oh, we're ok for now" ... "oh actually maybe this or that"... yada yada yada.
If its truly an emergency then cut the crap and use the standard phraseology and keep the communications terse.
In the US, we don't typically call Mayday/PanPan (despite it being both allowable and more correct). Pilots literally say "N777DS declaring an emergency. Engine out/Low fuel/Birdstrike". The effect is that all emergencies are Mayday.
someone further down found the incident [1] I was referring to. It was 14 years ago, not 5 as I had initially thought. Curious to hear your take on it. Pilot said "if you don't give me this runway, I'm going to declare an emergency..." which I don't think is the most helpful thing to say. But there were definitely many swiss-cheese holes lining up that day.
It is a requirement [1] to land with 45 minutes of fuel remaining, if the pilots go under that, it is considered an incident. As soon as estimated landing fuel goes under the limit, the flight needs to declare an emergency (as was done in this case).
They got within a hair of crashing, there is nothing impressive about this. 30 minutes, ok, you still get written up but this is cutting it way too fine.
Either this is true, or this is why there’s a 45 minute reserve requirement. There were three failed landing attempts in two airports prior to the successful landing, and they spent almost as much time attempting to land as the scheduled flight took.
Seems like this was exactly the scenario it was designed for?
No, this is what should never happen. I wrote fuel estimation software for cargo 747's and the one thing I would have never ever wanted to read is that an airliner of the company I worked for had landed with too little fuel.
This one. The reserve is there in the same way that a crash barrier is there on the highway. You really don't ever want to use it, but when you do use it and it ends well you treat it just as seriously as though you would treat a crash.
I would imagine 6 min fuel left was designed for something extreme. Maybe involving damage to aircraft limiting where it can land etc. Or extreme weather event such had high winds affecting all airports within 500 miles.
But I'm truly surprised (in a bad way) people on the ground couldn't solve the situation earlier. The plane was in an emergency situation for hours, wtf.
Also, the airport density in the UK is high, they should have been diverted since before the first attempt, as it has happened to me and thousands of flights every single day around the world.
The incident investigation will surely focus on exactly those things. But: just like shipping aviation is at the mercy of the weather and even though the rules (which are written in plenty of blood) try to anticipate all of the ways in which things go wrong there is a line beyond which you are at risk. I've had one triple go-around in my life and it soured me on flying for a long time afterwards because I have written software to compute the amount of fuel required for a flight and I know how thin the margins are once you fail that third time. I am not going to get ahead of the investigation and speculate but I can think of at least five ways in which this could have happened, and I'm mostly curious about whether the root cause is one of those five or something completely different. Note that until there is weight on the wheels you don't actually know how much fuel remains in the tanks, there always is some uncertainty, to the pilots it may well have looked as if the tanks were already empty while they were still flying the plane. Those people must have been extremely stressed out on that final attempt to land.
There are but this is not as precise as you might think due to a lot of confounding factors. Even the best flow meters are only about 0.2% accurate, and I find that seriously impressive.
That's one conclusion. But don't rule out a lot of other things that may have been a factor, for instance, they may have had a batch of bad fuel, they may have had less fuel to start with than they thought they had (this happens, it shouldn't but it does happen), the fuel indicators may have been off (you only know for sure after touch down), there may have been a leak, an engine may have been burning more than it should have. There are probably many others that I can't think of of the top off my head but there are a lot of reasons why the margins are as large as they are.
I read and agree with all those options being possible. Except the "they may have had a batch of bad fuel". How would that work in your thinking? I can imagine a bad batch of fuel leading to engine damage or flameout and many other things, but it is hard for me to imagine how a bad batch would lead to not enough fuel remaining in the tank.
If you have more water in the fuel than you think you do (there always is some due to condensation in the tanks) then you might be able to reach your destination but you'll be burning more 'fuel' than your original estimate would have you believe because there is less power per unit weight of (contaminated) fuel.
This is fairly common in GA and there are cases where it has happened in scheduled flights as well. That's why fuel sampling is common practice.
It's supposed to be an extremely low amount and the fuel pick-ups are placed such that it should never be a problem but there have been cases where water in the fuel caused problems, including at least one notorious crash where the cause was identified to be fuel contamination.
I saw this plane out my window when it was landing at Prestwick. It was dark and windy about 60mph and I said to my wife "what's that in the sky".
The airport is about 5 miles away, for some reason this one caught my eye - in the hundreds/thousands of planes that go by I've never said that before, don't know if it was pointed an odd direction but it appeared stationary. We thought it was like a star, but too bright. We looked it up on flight radar to see if it was a plane and it was the one that later came out.
I know this will not be relevant to anything but I thought it was a strange coincidence then I saw it on my hn feed.
> One pilot who reviewed the log said: “Just imagine that whenever you land with less than 2T (2,000kg) of fuel left you start paying close attention to the situation. Less than 1.5T you are sweating. But (220kg) is as close to a fatal accident as possible.”
> The Boeing 737-800 had just 220kg of fuel left in its tanks when it finally landed, according to a picture of what appears to be a handwritten technical log. Pilots who examined the picture said this would be enough for just five or six minutes of flying.
For reference, passenger airlines immediately declare emergency if their planned flight path would put them under 30 minutes of fuel (at least in the US). Landing with 5 minutes remaining of fuel is very atypical
Certainly banned enough that you can't listen to ATC playback anywhere online. I think in practice you can use an air band radio at home (not sure how anyone would know if you were anyway).
Incident: Malta Air B738 at Prestwick, Edinburgh and Manchester on Oct 3rd 2025, landed below minimum fuel
By Simon Hradecky, created Sunday, Oct 5th 2025 14:39Z, last updated Friday, Oct 10th 2025 15:02Z
A Malta Air Boeing 737-800 on behalf of Ryanair, registration 9H-QBD performing flight FR-3418 from Pisa (Italy) to Prestwick,SC (UK), was on final approach to Prestwick's runway 20 when the crew went around due to weather. The aircraft entered a hold, then attempted a second approach to runway 20 about 30 minutes after the go around, but again needed to go around. The aircraft again entered a hold, about 10 minutes after entering the hold the crew decided to divert to Edinburgh,SC (UK) where the aircraft joined the final approach to runway 24 about one hour after the first go around but again went around. The aircraft subsequently diverted to Manchester,EN (UK) where the aircraft landed on runway 23R about 110 minutes after the first go around.
On Oct 5th 2025 The Aviation Herald received information that the aircraft landed below minimum fuel with just 220kg fuel (total, 100kg in left and 120 kg in right tank) remaining.
The aircraft returned to service about 13 hours after landing.
On Oct 10th 2025 the AAIB reported the occurrence was rated a serious incident and is being investigated.
A passenger reported after the first go around at Prestwick the crew announced, they would do another attempt to land at Prestwick, then divert to Manchester. Following the second go around the crew however announced they were now diverting to Edinburgh, only after the failed approach to Edinburgh the crew diverted to Manchester.
In commercial aviation (passenger/cargo), typically about half the take-off weight is fuel. That's not half the payload weight (pax + cargo + fuel), it's half the takeoff weight.
For a medium-range flight (say ~2000 mi / 3200 km) each passenger incurs somewhat more than their own weight in fuel.
I don't think that's correct. The MTOW (Maximum Take-Off Weight) of an A320ceo is 78,000 kg, while the max fuel capacity is approximately 24,210 litres. Using Jet A-1's density of roughly 0.804 kg/L, that's about 19,460 kg of fuel, which represents only 25% of the take-off weight. The OEW (Operating Empty Weight) for that aircraft is approximately 42,600 kg, which means you'd need the fuel to weigh around 35,400 kg for your "half the take-off weight is fuel" claim to be true—nearly double the actual fuel capacity.
Even for a long-range aircraft like the A350-900, with an MTOW of 280,000 kg and a fuel capacity of approximately 138,000 litres (roughly 111,000 kg at 0.804 kg/L), fuel represents about 40% of the take-off weight. The OEW is approximately 155,000 kg, meaning even a completely empty plane (except for crew) loaded with maximum fuel still wouldn't reach your claimed 50% fuel fraction.
Because the market responds to your behavior by slightly lowering the cost of flying to fill those seats, demand increases to match from slightly lower income people. Because they then organize their lives slightly more around cheap flights, it gets even harder to lower the impact of flying.
Paradoxically, rich people like us (you're a tech worker too...) flying more, because we're less sensitive to price, leave more room for pricing in carbon reduction strategies in the tickets/taxes. If you have more seats from the lower end of the market... you don't have as much flexibility in solutions.
That might be true within a certain band, but if enough people stop flying, there's only so much elasticity there. Eventually they stop flying as many planes.
(Of course, subsidies probably throw a wrench in all of this.)
You don't need your own rooftop solar. You can time your charges for when power is cheap (i.e. renewables are highly represented in the grid mix). In many locations you can get an electricity tariff that changes by time of day, either fixed times of day or nearly real-time to track the current wholesale price.
Here in Scotland, we have an EV electricity tariff that give us low rates between 00:30 - 05:30 while the wind turbines spin and demand is low, and our plug-in hybrid is programmed to charge during those hours. (We also run the dishwasher, washing machine, and tumble dryer on time delay during those hours as much as possible)
With nearly all of our car trips being local, the ~25 mile electric range the plug-in hybrid is rarely exceeded. We fill the petrol tank maybe once every 3 or 4 months, or when we're on a road trip.
Pure EVs are harder to justify in the UK currently unless you do basically all of your charging at home, because with 20% VAT added to the price of electricity from public chargers, and too-low fuel taxes, the per-mile cost is similar to—or sometimes more expensive than—driving on petrol. It's shockingly bad public policy.
Octopus Energy in the UK. Sometimes you can get paid to take power off the grid. Unfortunately batteries are too expensive to make really good use of it.
The EV is by far the least polluting option. In a year or two of normal driving, even on a dirty grid, you generate less pollution than if you were burning fuel in the car.
Grids are getting lower carbon intensity every year, so it just gets better after that.
It's also not clear that rooftop solar is better than anything else, the carbon involved in getting it to you, installing it, the business that does the installation… It's not very efficient.
It doesn't though. The vast majority of flights are short-haul or long-haul flights and not domestic. This data uses the UK flight data so let's look that up.
So you can see that over 90% of all passengers do not fly domestically within the UK. So only the domestic flights emit more CO2 than combustion engine cars, but they are the minority. If you were to look at the US, flights that short probably play even less of a role due to longer distances between cities in the US (in comparison to the UK).
In conclusion the data you provided very much proves my point so thank you for providing the source for my statement yourself.
Especially crazy considering the 737 is not a particularly large commercial aircraft.
40kg/minute is around 12 gallons (47 liters) of fuel per minute. Meanwhile a 777 burns around 42 gallons (160 liters) per minute. A 747 burns 63 gallons (240 liters) per minute - more than a gallon per second!
40kg of fuel per minute is a lot but airplanes carry a lot of people.
Web searches suggest a 737-800 gets about 0.5mpg at cruise. With 189 passengers in a one-class layout that’s 95mpg per passenger. With 162 in a two-class layout that’s 81mpg per passenger.
This is better than a single person in a car but four people in a Prius gets 50mpg * 4 = 200 mpg.
This is what vexes me about the lack of emphasis on highway self-driving. Everyone's obsessed with robo taxis.
An overnight trip that's automated could go at 40 mph and get seriously good gas mileage. I mean man with four people would probably get almost 100 miles per gallon.
And this would eliminate a lot of short-range flights
It should be a lot easier to implement than having to worry about a whole class of problems that robo taxis in cities have
The robo taxi links the last few miles to transit.
I recently travelled from my house in Seattle to my office in SF without ever getting in a car. I walked more in the airport than I did anywhere else.
Home -> Walk 11 min -> Metro Bus -> light rail -> SEA -> SF -> BART -> Walk 2 min to Hotel.
Next time I go down I’m going to take Amtrak. I couldn’t this time because it was full. In 2024 360,000 people rode that route on 730 trips for an average of about 500 people per trip. Looks like Amtrak gets between 0.6 and 2mpg. That’s 300mpg to 1000mpg per person which is better than a Prius’ 200mpg at 40mph.
Seattle to SF is 1019 miles. At 40mph that’s 25 hours, which is an hour slower than the Amtrak schedule.
Look at it (2.5 t/h) by volume (0.82 kg/L): 3 kL/h (790 gal/h) == 50 L/m (13 gal/m) == 830 mL/s (0.9 qt/s), and then divide the total flow rate by 2 for rate per engine.
Or divide the total by the number of passengers (~189) flying to consider effective fuel economy (per passenger) or 13 kg/pax/h or 3.6 g/pax/s.
They must plan to never land with less than 30 minutes of fuel, or about 1.25 t, and I'd say they should never, ever land with less than 15 minutes in their career during a pan/mayday bingo fuel emergency.
The latest Captains Speaking podcast has an discussion about one of the hosts being in a similar situation: https://youtu.be/5ovlZ221tDQ
Fortunately, the flight left with extra fuel, because it was cheaper to carry excess from the origin airport than to buy it at the destination airport, so reserve fuel wasn't needed, but it was close. Also, there was lots of lightning.
I absolutely love insights like this into areas of the world I have no knowledge. Makes absolute sense in the modern world but also something I'd not think about
Trucking companies started adding this to their logistics about a decade ago as well. Once they had accurate fuel price information for most of the country they started telling their drivers precisely how much fuel to onboard at each stop.
It reminds me of a Transavia flight from Girona to Rotterdam that had to be diverted to Amsterdam back in 2015 (1 attempt at Rotterdam, decided to divert to Amsterdam, then 2 attempts in Amsterdam).
It was a particularly stormy weekend and it turns out from the article that they had 992kg of fuel left:
As a naive person, I have a simple question - why would they even fly to an airport where there's 100mph winds? Wouldn't ATC know this and tell the flight way in advance to fly to a different destination?
Because the weather is very changeable. You may get a lull in the wind for a couple of mins, enough to land.
I've been on a couple of flights like that. Once where we did two attempts and landed on the 2nd, the other where we did 3 but the had to divert. Other planes were just managing to land in the winds before and after our attempts.
The other problem is (as I found out on that flight) that mass diversions are not good. The airport I diverted to in the UK had dozens of unexpected arrivals, late at night. There wasn't the ground staff to manage this so it took forever to get people off. It then was too full to accept any more landings, so further flights had to get diverted further and further away.
So, if you did a blanket must divert you'd end up with all the diversion airports full (even to flights that could have landed at their original airport) and a much more dangerous situation as your diversions are now in different countries.
This very recent Mentour documentary is extremely relevant, came to mind immediately. Multiple redirects due to bad weather, extreme "Get-there-itis" and eventually running out of fuel.
Great edutainment if you're feeling in the mood for that. If you're inpatient you can skip to 14 minutes, before that it's just backstory.
I wonder if the pilots considered Newcastle (or Teeside)? The METARs showed favourable weather conditions at Newcastle and many planes landed there that day without issue I believe. Also far closer to Edinburgh than Manchester. I wonder if they thought that Manchester being further south, had a better chance of better weather?
Most of the trains north between Preston and Glasgow were being cancelled that day due to the weather. Perhaps knowing they only had one more attempt at landing safely left, Manchester further south seemed like the better bet.
You'll probably have to wait a while. Petter is pretty insistent on waiting for the full incident report so that he can be completely thorough and avoid speculating.
The headline is about the landing, but the issue here happened at takeoff. There were 100 mph winds at the destination and this was their 4th fallback attempt and their third airport. This flight should never have taken off, the risk of multiple diversions was easily predictable, but the flight took off headed toward an airport in dangerous conditions, got diverted to a second airport that was just as dangerous, then finally to a third where conditions were so bad other flights were being cancelled (https://uk.news.yahoo.com/storm-amy-brings-flight-chaos-2019...) and where it finally landed because it was either land at that airport or land somewhere that is not at all an airport. Once this flight was in the air, disaster was more or less inevitable and we lucked into a narrow eviting window.
This seems to be a case where the error was that the 2nd diversion was to another commercial/passenger airport. The situation after it was determined Edinburgh was a no-go was dire and making it to an airport like Manchester was a luxury they did not have safe fuel for.
> The pilots had been taking passengers from Pisa in Italy to Prestwick in Scotland on Friday evening, but wind speeds of up to 100mph meant they were unable to land.
> After three failed attempts to touch down, the pilots of Ryanair flight FR3418 issued a mayday emergency call and raced to Manchester, where the weather was calmer.
#1 - if Prestwick had wind speeds up to 100mph, then why the h*ll was the airport not closed down?
#2 - if the pilots had experienced conditions that dire during their first two landing attempts at Prestwick, then why the h*ll did they stick around for a third attempt?
EDIT: The article's a big vague, but it seems to have been 2 attempts at Prestwick, then 1 at Edinburgh, then the last-minute "oops, do I really want to die today?" decision to run to Manchester.
This one is pretty straightforward so it doesn't need an AAIB report. Failure of pilots to brief destination weather conditions and anticipate proper bingo fuel accordingly. Storms in the area == brief max go arounds, brief alternates, and carry extra fuel. They screwed up by taking unnecessary risks of too many go arounds and barely making an alternate because they didn't play it safe by carrying additional fuel. Take these bold pilots to the chief pilot's office for an uncomfortable conversation without tasty snacks.
United Airlines Flight 173 ran out of fuel while circling Portland International Airport trying to troubleshoot a landing gear. Six more minutes of fuel could have helped the airliner to land in the Columbia river by the airport or belly land on the runway. The captain chose to keep troubleshooting and crashed just 6 miles away from the airport.
We definitely involve the dispatcher in the diversion decision. Especially if it's an unplanned diversion, where the big-picture view the dispatcher has is very useful for us in our metal tube.
Sure, company dispatchers are usually part of the conversation, and in non-emergency diversions (i.e. the vast majority), they may suggest specific airports that would be more convenient for company logistics. But the final decision is always the pilots' - and once they've declared an emergency, more or less every single airfield, including military, becomes available to them.
Unless they are in an emergency and are busy with aviating, they will coordinate with their dispatcher on diverting, even if only to verify that the weather at the intended alternate is still favorable. Per the FAA regulations, the PIC and the dispatcher have joint operational control over the flight. Of course, at the end of the day, only the pilots have their hands on the controls, so they can make the plane do what they want—but from a legal standpoint, the dispatcher and pilot-in-command have equal & shared responsibility for the safe operation of the flight.
I realize this is a UK carrier and was operating in the EU/UK, but for the most part, the rest of the world uses the US legal framework for aviation as a boilerplate for their own civil code. Yes, there are some differences, but these are usually minor and more of "differences in quantity" rather than "differences in kind". [Since the airplane was invented here the US had a head start on regulating civil aviation.]
Are there any good online databases with fuel level details for individual commercial flights? I've been on a few flights that had to circle for a long time / had a number of go-round attempts, and I've never been able to find details after the fact about how close to the margins we were.
This happened in my country with I think a Vistara flight, where they had 5 minutes of fuel left.
I myself went from Bangalore to Delhi a couple of weeks back, and the poor pilots told the air hostesses at least twice or thrice to prepare for landing but the plane did not land until much much later.
Had a 1 maybe 1.5h holding pattern in Oslo once in Ryanair where they hoped they could land in extreme snow. Then diverted in the end (surprise!). Happened in 2009 though. Joked they were very desperate to land at Oslo because they cant afford to divert.
And that is how fuel reservoir requirements rise for all. Im sure, the whole airline industry is looking at the whole markets share prices going down- writing happy songs and packing gift baskets for Ryanair.
On the positive side, if they had made a crash landing with so little fuel, there would not likely have been a fiery explosion, and many more passengers would have survived than normal?
Air + fuel explodes just fine. You really don't want to crash an airliner. At landing speed the number of people dead will still be > 0 and the remainder has a good chance of being injured seriously.
This happened at landing speed (the airport is only a few hundred meters from the crash site) and the plane was at the end of its flight from Turkey, it did not catch fire. Still, 9 people perished and the remainder were all but one injured 11 of them seriously.
Dunno about "only" ... 99.99998% of flights kill 0% of their passengers. Even if "just" one passenger dies in an incident, your flight is already in the 0.00002th percentile for safety, very bad!
Yes, even though that is a harsh conclusion to make and for the families involved of course it doesn't matter at all. But as these come this was bad but still not nearly as bad as it could have been. They were about to cross one of the busiest highways in NL, another 100 meters and it would have been an entirely different story. The field they landed in is in the Haarlemmermeerpolder, so clay and it had just been plowed.
> and many more passengers would have survived than normal?
This[1] kind of crash landing is very rare (in that case there was no fire despite being immediately after take off, perhaps because of the cold). Normally an outcome like this is only reasonable to expect if you actually reach a runway despite being out of fuel. Like Gimli[2].
Yup. They also popularised excessive baggage under the seat, and I routinely used to see obvious hazards that would impede an evacuation. Staff would turn a blind eye. Probably still do
Further, with the baggage being there in easy reach under the seat, I reckon people would be more tempted to take it with them when evacuating.
That they're are a safe airline seems to be incredible luck - they have all the components for it not to be.
Yes and no. I had this happen recently and looked into it.
My wife has been using my car, which is a Diesel Golf with a fuel capacity of 14.5 gallons. We set off driving one Saturday to visit my parents, and I noticed the fuel gauge was below empty already. By the time I got to the gas station, I put 14.3 gallons of fuel into it. I calculated that that works out to be about a cup and a half of fuel.
So once you hit empty on my car, you definitely have a ways you can drive still. I feel comfortable driving about 30+ miles, and it's never died on me. That puts it at no more than 1 gallon of fuel left in the car based on my experience (not scientific I know, but I've owned 2 of these cars, with about 190k total driven miles). It's a lot less than 10 liters from E to Dead on the roadside.
You shouldn't tempt fate with a diesel, or any direction injection car for that matter. The high pressure pump will shred itself very quickly as the diesel is used for lubrication.
* enough reserve to waste some in traffic. On top of that
* enough reserve to find gas station. On top of that
* enough reserve to drive to neighbouring city for gas station. On top of that
* enough to cruise 30 minutes around that neighbouring city looking for other gas station in case the previous ones were closed. On top of that
* enough station to run around parking lot looking for space to park
One of the problems with modern internet discourse is there is an implicit assumption that the problem of one country is automatically the problem of another country.
I've never heard of any of these problems with RyanAir. They treat you as less than cattle and generally their service is shit, but I'm not aware of RyanAir being unsafe.
Actually, in a quick check it seems the total fatality count for RyanAir is zero, with only two (on-fatal) major incidents (2008, 2021). That's seems a pretty good track record considering the amount of flights they do.
> Between overworked, understaffed ATC and undertrained pilots, I'm expecting some major disasters in the coming years.
Maybe in the US, but this story is based in Europe, each country maintains a regulated standard and there are no EU wide disruptions that have ever happened to the best of my knowledge. Also Ryanair don't travel transatlantic flights.
Three weeks ago in Nice, France it was a fraction of a second away from two A320s crashing [0] and possibly hundreds of deaths, similar to Tenerife disaster [1].
Investigation is ongoing and many factors are at play (bad weather, extra work for ATC due to that, confusing lighting of runways etc) but also, from French media reports, there used to be 15 people per shift 5y ago in Nice ATC, now there are just 12, and traffic is higher.
Many people left the profession during Covid and haven't been replaced.
Mistakes and disasters happen, unfortunately the safety we have while flying today has been written in blood, but there is no major understaffed ATC and undertrained pilots in general as mentioned.
15 down to 12 in 5 years with more traffic is not out of the question with advancements in technology but of course, if there is a report that shows understaffing then absolutely it should be addressed straight away and it will be, by the French government.
I mean, the US also hasn't had any widespread waves of disruptions that led to incidents or flight problems. Same as the EU. American flights and airspace are usually safer too, statistically speaking.
Why? Is ATC a problem in other countries than the US? Are they also under training pilots? If anything RyanAir with its flamboyant history of cost cutting (CEO always threatening to charge for use of the onboard lavatory) seems a more likely source than the flying infrastructure itself.
Ryanair has a very good safety history, among the highest in the world.
They make outrageous claims for publicity, and their customer experience is all about hidden extras and "gotcha" pricing, but I don't think they fuck around when it comes to safety.
They know that with their reputation they would be sunk if they did have a major incident.
> In 2012 and 2013 “Brandpunt Reporter” broadcasted a two episode TV investigation in which Ryanair pilots, speaking anonymously, raised concerns about the airline’s fuel policies and company culture. The pilots revealed that the company may be exerting pressure on them to minimize the amount of fuel they take on board – a practice which limits significantly the fuel costs for the company but could jeopardise safety in certain circumstances. The direct reasons for this broadcast were 3 emergency landings of Ryanair aircraft in Valencia Spain on the 26 July 2012, within a short timeframe due to low fuel levels.
What indication is there that our pilots are undertrained?
I am just a PPL, and that was not an easy thing to accomplish (most pilots complete 50% more hours than required before they are able to pass that test), but my impression is that western training standards for commercial pilots are incredibly high, and the safety record seems to back that up.
In the US, I think that's probably true especially using hours as a proxy for training.
The EU has shown us that you can safely have far fewer hours.
As a pilot I do think that nothing replaces butt in seat, but I also think that 1500 hours of instructing/aerial surveying/hour building is well into the diminished marginal returns area.
In this case, they likely had adequate fuel for, the usual eventualities but the weather in Scotland was particularly bad that night across the whole country (source: I live near Prestwick airport).
Either Edinburgh (on the east coast) or Prestwick (on the west coast) are ok (one or the other or both) but in this case neither was suitable so the nearest was Manchester - definitely an edge-case.
I don't know how much fuel they had, or if they could've fitted any more on the plane but it was unusual circumstances.
There was a military plane right behind it with the same issue that night too.
Waiting on full flight in Europe, good airport, for take off.
Pilot says over speaker : " We are delayed becuase FUEL guy got UPSET on tarmac and has QUIT. We know need someone ELSE to fill the plane with FUEL. " Said in a COMPLETELY nonchalant voice.
Immediately I get concerned, try not to think what cause a FUEL TECH to QUIT regarding THIS PLANE and fuel issue. Just close my eyes, relax.
2 minutes later pilot comes on intercom again "For some WEIRD reason, someone wants to get off the plane. Now we have to wait for ground crew to find his suitcasebecause of rules. How annoying.."
Plane waits for an hour on tarmac for BOTH passenger to get off and for FUEL to be finally "resolved".
Arrive eventually at destination.
Most of the trouble would have been avoided if the pilot had not sounded nonchalant about a "NON ISSUE about FUEL that a technician just QUIT OVER". I swear i even rememebr saying the statement with a hint of humour, like what on earth is the problem.
This is a true story, and the fact this incompetence happened to me, well I wouldnt have believed it otherwise.
I imagine everyone involved know that they are doing dangerous things, not taking a drop more fuel than is legally required for profit, knowing that none of that is going to change unless there is a major accident... They keep[1] landing these planes with X minutes of fuel left, but it doesn't do anything, until some plane falls from the sky with 0 minutes of fuel left then everyone knew all along and the rules are changed and nobody is held accountable.
You missed the point of the story, the issue was not lack of fuel, it was a crew member quitting because of a fuel issue, most likely a misunderstanding.
Fuel misunderstandings have resulted in numerous serious incidents, try googling it bro
That is very exceptional. I've written fuel estimation software for airliners (cargo, fortunately), and the number of rules regarding go-arounds, alternates and holding time resulted in there usually being quite a bit of fuel in the tanks on landing, by design. I've never heard of '6 minutes left' in practice where it wasn't a massive issue and the investigation into how this could have happened will make for interesting reading. A couple of notes: the wind and the time spent on the three go-arounds + what was necessary to get to the alternate may not be the whole story here, that's actually factored in before you even take off.
I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
The context you're missing is that Ryanair have routinely declared fuel emergencies in the past, and it seems an operational tactic - they want to carry less fuel to burn less fuel, and then have to regularly mayday to jump the stack on inbound, saving cash. That's not covered in the article, but you can sure as hell expect the CAA are going to take another look at them and their operations planning.
On this one, they did 3 attempted landings at Prestwick. [Edit: I now see that the third attempt was at EDI] What happened between the first and the second landing that made them think on their second go-around that a third attempt was more likely to succeed than the previous two? Was the wind dying down, or was the captain just feeling a bit braver or stupider? [Edit: I'm still curious as to what information they gathered that landing conditions were significantly different at EDI to make that diversion, given its relatively close and so likely to have similar weather].
Why was their final reserve Manchester when there were literally dozens of closer suitable airports, at least some of which are likely to have had better wind conditions by virtue of lower gusts, or more aligned to runway direction so not dealing with a strong crosswind?
There are many reasons I won't fly Ryanair, but not least because they have been shown over and over again to make reckless planning and operational decisions, and they are fortunate to have not had hull losses as a result. Time is ticking down, variance will catch them one day, and a sad & tragic catastrophe is only a matter of time. People will go to prison as a result, because this pattern of behaviour shows that this isn't "bad luck", it's calculated risk taking with passenger and crew lives to save money.
> There are many reasons I won't fly Ryanair
I swore off them a decade ago when I realised how adversarial their relationship with their passengers is.
Until an accident does happen, I have no doubt they'll trouser a lot of cash.
Not just adversarial to passengers but to their employees also.
I hadn't heard about this. They can't be having fun if that's the case, caught in between the treatment of their employer and the customers they pay it forward to (for money).
I fly with them all the time and never have any kind of issue at all. They offer a good deal, ok there’s a couple of obvious dark patterns in their app and way of doing business but they’re hardly unique in that respect. Feels like getting a fast bus between European cities nowadays.
Well that revolver didn't go off the last 5 times I pointed it at my head and pulled the trigger. Surely on the 6th pull we can guarantee the same outcome!
But these bus companies have also been involved in fatal accidents more than a few times over the past years.
Multiple as a result of driver error or no outside involvement from a third party.
Do please give examples of Ryanair fatalities during that time.
Ryanair the bus company?
I once had a board member who was also on the board of Ryan Air, and he casually told me a story about when their CEO gave a presentation on adding a credit card -powered interlock on the cabin lavatories. He told them, “They’re my planes and if you have the nerve to shit in them you should have to pay for the cleanup”.
My colleague thought he was portraying the CEO as a cool guy and decisive manager, but I thought the guy sounds like a sociopath.
i heard from an airport employee once that they wanted to keep the airplane started in between flights. This was specifically so they can skip the preflight checks. Thankfully they were not allowed to
Naively as an outsider, this situation seems like everything worked as intended?
On a nominally 2h45m flight, they spent an extra 2 hours in the air, presumably doing doing fuel intensive altitude changing maneuvers, and were eventually able to land safely with their reserves almost exhausted.
I’m a little confused by what there is to investigate at all.
How much fuel should they have landed with?
In safety-critical systems, we distinguish between accidents (actual loss, e.g. lives, equipment, etc.) and hazardous states. The equation is
hazardous state + environmental conditions = accident
Since we can only control the system, and not its environment, we focus on preventing hazardous states, rather than accidents. If we can keep the system out of all hazardous states, we also avoid accidents. (Trying to prevent accidents while not paying attention to hazardous states amounts to relying on the environment always being on our side, and is bound to fail eventually.)
One such hazardous state we have defined in aviation is "less than N minutes of fuel remaining when landing". If an aircraft lands with less than N minutes of fuel on board, it would only have taken bad environmental conditions to make it crash, rather than land. Thus we design commercial aviation so that planes always have N minutes of fuel remaining when landing. If they don't, that's a big deal: they've entered a hazardous state, and we never want to see that. (I don't remember if N is 30 or 45 or 60 but somewhere in that region.)
For another example, one of my children loves playing around cliffs and rocks. Initially he was very keen on promising me that he wouldn't fall down. I explained the difference between accidents and hazardous states to him in childrens' terms, and he realised slowly that he cannot control whether or not he has an accident, so it's a bad idea to promise me that he won't have an accident. What he can control is whether or not bad environmental conditions lead to an accident, and he does that by keeping out of hazardous states. In this case, the hazardous state would be standing less than a child-height within a ledge when there is nobody below ready to catch. He can promise me to avoid that, and that satisfies me a lot more than a promise to not fall.
If you haven't done so: please write a book. Aim it towards software professionals in non-regulated industries. I promise to buy 50 to give to all of my software developing colleagues.
As for 'N', for turboprops it is 45, for jets it is 30.
I want to write more about this, but it has been a really difficult subject to structure. I gave up halfway through this article, for example, and never published it – I didn't even get around to editing it, so it's mostly bad stream of consciousness stuff: https://entropicthoughts.com/root-cause-analysis-youre-doing...
I intend to come back to it some day, but I do not think that day is today.
Just started reading the linked text after reading your comment and I agree, this is high quality education, and enjoyable. It's an art, really. Thank you for sharing your work and please keep it up.
Just a thought I had while reading your introduction: this is applicable even to running a successful business model. I'm honestly having trouble even putting it into words, but you have my analytical mind going now at a very late hour... Thanks!
Ok. I am impressed with your ability to take such complex subjects and make them plain, you are delivering very high quality here. The subject is absolutely underserved in the industry as far as I'm aware of it, and I would love to have a book that I can hand out to people working on software in critical infrastructure and life sciences that gets them up to speed. The annoying thing is that software skills are values much higher than the ability to accurate model the risks because that is only seen as a function of small choices standing by themselves. A larger, overall approach is what is very often called for and it would help to have a tool in hand to both make that case and to give the counterparty the vocabulary and the required understanding of the subject in order to have a meaningful conversation.
Edit: please post your link from above as a separate submission.
Write it as a children's book. A literal ELI5.
(Knowing, of course, that it will still be read mainly by engineers. But that's the charm.)
I have a rather over-confident five year old, so would LOVE that book right now.
Your writing is good, please keep at it. I think it would help a lot if you made it clearer when you're talking between root-cause-analysis for software, aviation, other things, or generically.
Also, your train-of-thought is pretty deep; bulleting runs out of steam and gets visually confusing, especially with the article table-of-contents on RHS, you're only using <50% of screen width. Suggest you need numbered/lettered lists and section headings and use the full screen width.
Thanks, I would buy your book. But I understand the effort necessary all too well.
If he aims it toward five year olds as he had explained it, bet it would be even more applicable to our profession.
Having spent some time with my five year old nieces and nephews, sometimes I wonder if five year olds could run companies better.
(note: obviously sarcastic but kids really do have some amazing insights that we forget when trying to chase KPIs or revenue)
See also: various points in the Evil Overlord list[0]. Selected examples:
[0] https://tvtropes.org/pmwiki/pmwiki.php/Main/EvilOverlordListI'd never seen that list before but it's hilarious!
Seconded.
That being said: I have - for some years now - started to read air accident board reports (depending on your locale, they may be named slightly different). They make for a fascinating read, and they have made me approach debugging and postmortems in a more structured, more holistic way. They should be freely available on your transportation safety board websites (NTSB in America, BFU in Germany, ...)
Google’s SRE STPA starts with a similar model. I haven’t read the external document, but my team went through this process internally and we considered the hazardous states and environmental triggers.
https://sre.google/stpa/teaching
Disclaimer: currently employed by Google, this message is not sponsored.
Seconded! This was an extremely well written and well thought out explanation of this idea. Would love to read more along these lines.
(Will now be checking out your blog.)
Also check out risks digest:
https://catless.ncl.ac.uk/Risks/
[dead]
> Trying to prevent accidents while not paying attention to hazardous states amounts to relying on the environment always being on our side, and is bound to fail eventually.
The reason they had less than 30 minutes of fuel was because the environment wasn't on their side. They started out with a normal amount of reserve and then things went quite badly and the reserve was sufficient but only just.
The question then is, how much of an outlier was this? Was this a perfect storm that only happens once in a century and the thing worse than this that would actually have exhausted the reserve only happens once in ten centuries? Or are planes doing this every Tuesday which would imply that something is very wrong?
This is why staying out of hazardous conditions is a dynamic control problem, rather than a simple equation or plan you can set up ahead of time.
There are multiple controllers interacting with the system (the FADEC computer in the engines, the flight management computer in the plane, pilots, ground crew, dispatchers, air traffic controllers, the people at EASA drafting regulations, etc.), trying to keep it outside of hazardous conditions. They do so by observing the state the system and the environment is in ("feedback"), running simulations of how it will evolve in the future ("mental models"), and making adjustments to the system ("control inputs") to keep it outside of hazardous conditions.
Whenever the system enters a hazardous condition, there was something that made these controllers insufficient. Either someone had inadequate feedback, or inadequate mental models, or the control inputs were inoperational or insufficient. Or sometimes an entire controller that ought to have been there was missing!
In this case it seems like the hazard could have been avoided any number of ways: ground the plane, add more fuel, divert sooner, be more conservative about weather on alternates, etc. Which control input is appropriate and how to ensure it is enacted in the future is up to the real investigators with access to all data necessary.
-----
You are correct that we will not ever be able to set up a system where all controllers are able to always keep it out of hazardous states perfectly. If that was a thing we would never have any accident ever – we would only have intentional losses that are calculated to be worth their revenue in additional efficiency.
But by adopting the right framework for thinking about this ("how do active controllers dynamically keep the system out of hazards?") we can do a pretty good job of preventing most such problems. The good news is that predicting hazardous states is much easier than predicting accidents, so we can actually do a lot of this design up-front without first having an accident happen and then learning from it.
> This is why staying out of hazardous conditions is a dynamic control problem
I don't think this philosophy can work.
If you can't control whether the environment will push you from a hazardous state into a failure state, you also can't control whether the environment will push you from a nonhazardous state into a hazardous state.
If staying out of hazardous conditions is a dynamic control problem requiring on-the-fly adjustment from local actors, exactly the same thing is true of staying out of failure states.
The point of defining hazardous states is that they are a buffer between you and failure. Sometimes you actually need the buffer. If you didn't, the hazardous state wouldn't be hazardous.
But the only possible outcome of treating entering a hazardous state as equivalent to entering a failure state is that you start panicking whenever an airplane touches down with less than a hundred thousand gallons of fuel.
My understanding is that the SOP for low fuel is that you need to declare a fuel emergency (i.e., "Mayday Mayday Mayday Fuel") one you reach the point where you will land with only reserve fuel left. The point OP was making is that the entire system of fuel planning is designed so that you should never reach the Mayday stage as a result of something you can expect to happen eventually (such as really bad weather). If you land with reserve fuel, it is normally investigated like any other emergency.
Flight plans require you to look at the weather reports of your destination before you take off and pick at least one or two alternates that will let you divert if the weather is marginal. The fuel you load includes several redundancies to deal with different unexpected conditions[1] as well as the need to divert if you cannot land.
There have been a few historical cases of planes running out of fuel (and quite a few cases of planes landing with only reserve fuel), and usually the root cause was a pilot not making the decision to go to an alternate airport soon enough or not declaring an emergency immediately -- even with very dynamic weather conditions you should have enough fuel for a go-around, holding, and going to an alternate.
[1]: https://www.casa.gov.au/guidelines-aircraft-fuel-requirement...
Landing at an alternate location is significantly more expensive, so I assume Ryanair put pressure on its pilots to avoid that…?
We'll find out in the investigation, but "get-there-itis" is a very common condition amongst pilots and can lead to them delaying making decisions (such as going to alternates) so it's possible that this happened without explicit (or implicit) pressure from management.
That being said, the fact that (AFAICS) they first tried to divert to a closer airport where the weather was similar rather than an alternate with clear weather was probably one of the causes of this event.
That's very enlightening. I'm casually interested in traffic safety and road/junction designs from the perspective of a UK cyclist and there's a lot to be learnt from the safety culture/practices of the aviation industry. I typically think in terms of "safety margins" whilst cycling (e.g. if a driver pulls out of a side road in front of me, how quickly can I avoid them via swerving or brake to avoid a collision). I can imagine that hazardous states can be applied to a lot of the traffic behaviour at junctions.
Well said, will think about asking this attitude towards my child, seems very helpful
As others have said, final fuel reserves are typically at least half an hour, and you shouldn't really be cutting into them. What if their first approach into MAN had led to another go around?
With a major storm heading north-easterly across the UK, the planning should have reasonably foreseen that an airport 56 miles east may also be unavailable, and should've further diverted prior to that point.
They likely used the majority of their final fuel reserve on the secondary diversion from EDI to MAN, presumably having planned to land at their alternate (EDI) around the time they reached the final fuel reserve.
Any CAA report into this, if there is one produced, is going to be interesting, because there's multiple people having made multiple decisions that led to this.
Suspect they were IFR. All your points stand. First time flying things with a jet engine, I was shocked how much more fuel gets burned at low altitude. It almost always works out better to max climb to altitude and descend than to fly low and level. On a small jet, things can get spicy fast when ATC route you around at 5000' for 15 minutes or so. Three aborted landings would gobble gas like crazy.
§ 91.167 Fuel requirements for flight in IFR conditions.
(a) No person may operate a civil aircraft in IFR conditions unless it carries enough fuel (considering weather reports and forecasts and weather conditions) to—
(1) Complete the flight to the first airport of intended landing;
(2) Except as provided in paragraph (b) of this section, fly from that airport to the alternate airport; and
(3) Fly after that for 45 minutes at normal cruising speed
They were most definitely IFR. Not because of the weather but because IFR is required above certain altitude 18,000 ft in the U.S. and typically lower in Europe (depends on a country). Jets including small private jets are almost always on IFR. Airliners with passengers - always.
Why does it burn fuel so fast?
My guess is higher air density means more wind resistance, which acts as negative forward acceleration.
Not just that. Jet engines are efficient at higher speeds because the exhaust of the jet engine is fast.
If the plane is going fast as well, that exhaust is more or less stationary relative to the ground. The engine works to exchange the position of the plane with the position of the air in front of it.
If the plane is going slow, it's accelerating the air backwards. That's where the work is going, making the engine less efficient.
Think about it this way: if the jet airplane is tied to the ground, its engines are running at 0% efficiency, working hard to blow the air backwards. You wouldn't want to stand behind a jet engine when the plane is about to take off, when that's effectively the case.
The same applies to propeller-driven planes, of course. But those can vary the prop speed as well as propeller pitch, having more control on how fast the air is being pushed backwards. This allows the engine to be efficient at a wider ranger of speeds, particularly, at the slower range.
But the propeller has a limit of how fast it can push the air back. When the prop blades start reaching the speed of sound, weird shit starts happening [1]. So propeller-driven aircraft have a limit on speeds at which they can go efficiently.
Jet engines (turbofans when it comes to airliners) trade off low efficiency at low speed / low altitude (where the airplane is spending a small percentage of flight time) for higher efficiency at high speed / high altitude.
Variable pitch turbine fans[2] aim to address this tradeoff, but the tech has yet to catch on.
[1] https://en.wikipedia.org/wiki/Republic_XF-84H_Thunderscreech
[2] https://en.wikipedia.org/wiki/Variable_pitch_fan
That sounds like Oberth effect in rocketry, where the faster you go the more efficient your rocket be: https://en.wikipedia.org/wiki/Oberth_effect
they have nothing to do with each other.
I think about it like this:
Jet needs to suck air from front. If air is stopped, sucking is hard. If air is already being thrown at you, you don't even need to suck, just let it come in.
You are right that accelerating the air backwards more reduces efficiency but I think it should be mentioned that the jet engine has to accelerate the air backwards to do any work pushing the plane forward. Picking it up and setting it back down affects the air with a net force of zero and therefore the force pushing the plane forward is also zero.
So perhaps the differential air speed between the intake and exhaust is a big factor in the efficiency equation? The bigger the difference the more work is needed..
Variable pitch turbine fans sound very interesting! Perhaps in the future as tech improves and fuel efficiency incentives continue to increase.
So, newton's first law?
Just reaching altitude again to make it to the first and later second alternate are mostly likely the biggest factors in the extra fuel consumption. That's very expensive.
The 30 min reserve is on top of the fuel needed to reach the alternate and do a landing there, so only the flight to the second alternate, plus the 2nd and 3rd landings at the initial destination would have cut into the reserve.
With 100mph winds I could easily see the 30 min reserve being eaten up by the flight from Edinburgh to Manchester. It's 178 miles! It takes a good 15-20 minutes to cross that distance when flying normally, add ascent & descent time and the landing pattern and you're easily at 24 minutes.
Edit: in other comments here, it seems like Edinburgh to Manchester is a 45 minute flight. So yeah, they could easily have been outside of reserves when they did the go-around at Edinburgh and still had only 6 minutes left at Manchester.
Yeah, although it depends what the alternate was in the flight plan. It may have been Manchester. Although I think its more likely it was Edinburgh, which in the circumstances was too optimistic. Too much concern about the minimal costs of fuel tankering to add a bit more gas? Or saving time by not refuelling?
Ive never flown on Ryanair and dont intend to.
As far as I’ve heard, Ryanair will cut into literally everything (including comfort and decency) for the sake of efficiency – other than safety. Even if they wanted to, they're subject to the same commercial aviation regulations as everybody else.
Do you have anything other than this single incident to back up your insinuation that they’re less safe than a full service airline?
I don't know how true this is but I have heard Ryanair will use the absolute legal minimum amount of fuel whenever possible whereas other airlines might fly with a bit more.
In theory though that shouldn't matter because as you say, the legal minimum should really be enough.
That seems like a cost/convenience tradeoff: The implication of only carrying minimum fuel is that the pilots can't hold for long to see if conditions improve and instead have to immediately go for the alternate destination airport.
The consequence of that is everybody ending up in the wrong place, but not in an unsafe way.
The flight plans I've seen accounted for two alternates, not one, a significant time in a holding pattern and up to three go-arounds. This was for cargo 747s and a while ago so chances are the regulations have changed by now, also, it may have been due to the kind of cargo.
From what I can tell, that only seems to apply to EASA since 2022. As it took off from an EU airport and landed in the UK, I don't know if that rule would apply.
You get that energy back on descent, no?
4 replies and 3 are dismissing even the idea..
Yes, you get "some" back, and its not negligible amount. Typical modern airliner can descend on 15-20:1, giving you over 150-200km (90-120mi) range from typical cruising altitude of 33 000 feet even with engines off. Most everyday descents are actually done by maintaining altitude as long as possible, and then iddling the engines fully for as long as clearance allows. (Ofc you then use engines as you geat nearer, because its safer to be a little low when stabilizing on approach, than a little high)
Thanks to turbofans(edited from turboprops) better efficiency + less drag at higher altitude its actually more fuel economical to command full thrust and gain altitude quickly, than slower climb, or maintaining altitude (which goes against our intuition from cars, where if you wanna get far, you never give full throttle).
But theres still some drag, so you dont get everything back, so you generally want to avoid murking in low altitudes as long as possible. Full thrust repeatedly at lowest altitudes (from failed go arounds) is the least economical part of flight, so you want to avoid those if possible. But its true that the altitude you gain is equivalent to "banking" the energy, just not all of it.
(1) this was a jet, not a turboprop
Edit: changed turbofan into turbprop, which is what I meant.
(2) fuel burned stays burned, you don't 'get it back'
(3) the altitude gained may have been adjusted to account for the low fuel situation
(4) the winds are a major factor here, far larger than the fact that 'what goes up must come down', something that is already taken into account when computing the fuel reserve in the first place.
So it seems. But because you want to land you then want to shed all that velocity. So you 'get it back' only to have to waste the bigger fraction of it. A go around is much like a mini take-off, you just miss the runway portion of it.
Nah. You want to land, but you are really not shedding most of your velocity until after touchdown. What you gain by burning fuel is energy, and you can either bank it into altitude, or velocity. You must shed both to land, but not so for go-around. There you shed almost all of your altitude, but you keep most of your velocity -> you still have a lot of energy left. That's why on go-around you spool your engines and start climbing basically right away, unlike typical takeoff, where after spooling up the engines you are still earth-bound until you build enough velocity.
So you only ever really lost your "altitude" component of energy, not "velocity" one. You run your engines at TOGA (Take Off / Go Around = maximum thrust), thrust to gain mainly altitude, only increasing speed a little bit. Then on another approach attempt you use both the altitude and excess velocity bank again.
In flight, ~all your energy losses go to drag. Doesn't matter if you bank it into speed or altitude, both is exchanged to be at minimums (0 altitude above ground, lowest safe landing speed) at touchdown. If you produce extra energy in your engines, it has to go to either speed or altitude, which you then pull out again, usually by maintaining speed while lowering altitude while having engines at idle.
(1) The turbofan category of jet engine seems to inspire a lot of very pretty animated technical diagrams—here’s one set from a German manufacturer [0]. Now if only we could convince Bartozs Ciechanowski to take on such a subject… [1]
(2) I know glider pilots who fly without any fuel at all, once aloft… sounds not unlike the 150-200km glide range that @MaxikCZ mentions at idle from cruising altitude.
[0] https://aeroreport.de/en/good-to-know/how-does-a-turbofan-en...
[1] e.g. https://ciechanow.ski/airfoil/
Aircraft that are designed as gliders are much lighter and thus have much longer glide range than aircraft that aren't. They're so lightweight that they can climb on thermals. A 737 is not going to be able to do that, but a regular glider can't fly at 400 knots.
> thus have much longer glide range
Im gonna be a little pedantic, but the weight has surprisingly small effect on glide range, actually none of the weight affect the range directly, its all from secondary effects.
The glide is given mainly by drag and lift (so body and wing geometry), correlated to certain speed. The weight isnt in the equation at all. What weight does, is increases the speed in which the aircraft achieves this maximum glide ratio, and in higher speed you have higher drag, which finally reduces the range.
Thats why many modern gliders have water tanks in wings, to increase the weight of the glider, moving planes speed of best glide ratio higher, allowing for more efficiency at higher speeds. Its worth it if the atmospheric condition provide strong lifts. Pilot can then dump the water in flight to reduce the wing load, allowing them to land with less speed, or just keep in the air longer as thermals get weaker in the afternoon/evening
(source, I used to be a glider pilot)
It should also be noted that gliders have crazy aspect ratios. Airliner wings are designed for completely different flight envelopes than gliders, it’s all a game of what you optimize for and what trade offs you are willing and/or required to make.
But of course that doesn’t mean that airliners can’t glide well, the Gimly Glider and Air Transat flight come to mind. But gliders can definitely beat an airliner in terms of performance.
You are, of course, correct, and thanks for clarifying.
Re: (2): There's a difference between sailplanes and gliders. Sailplanes are gliders that can “soar”, i.e. gain altitude just from the air that is moving up for some reason. Your friends have licence that says „Sailplane Pilot Licence”, not „Glider”.
The distinction is less pronounced nowadays, because there is no mondern aircraft designed as gliders-but-not-sailplanes, but historically there were planes that fit this niche, mostly military transport of WW1 and WW2 vintage.
Passenger jets (with engines turned off) are relatively decent gliders, but incapable of soaring. So no, you can't get more that about 20:1 glide ratio no matter how good is the weather (for sailplanes).
Regarding the turbofan and [0], above...if you're communicating to a non-engineer (me), how does the design get to the point of such complexity? I would love to learn the design story behind such an incredibly complex piece of machinery.
I am being serious, if you cannot tell.
For the same thrust it's more efficient to accelerate a large mass of air a small amount than t accelerate a small mass of air a large amount. The fan is what gives you that.
I rough guessed the cost of fuel over a 737's life as $150 million. Where the engines cost something around $30 million. That pushes the engineering economics towards maximizing the engines efficiency.
I'm suspicious that bypass ratio's for turbofans are close to maxed out. The diameter of the fan gets unwieldy. That was the design issue that the 737 Max was trying to get around. With bad results. Possible the future is hybrid designs with two engines and 4 or more electrically driven fans.
Yes, sorry, meant to write turboprop.
1 - a turbofan is a subset of jet engine, and there are no 738s running anything other than a turbofan.
Actually, nothing in civil aviation that has a "jet engine" has used anything but a turbofan (or turboprop) since the early 70s with the exception of Concorde and some older business jets.
(Turboprops are jet engines, too, to be precise, with the jet of exhaust gases powering the propeller.)
> Turboprops are jet engines
They are certainly turbine engines, but I thought "jet" was reserved for those engines that propel the vehicle solely by their exhaust stream and bypass air. I am willing to be told I'm wrong, though.
Turbofans are by your own definition jet engines. It's just that the bypass air is much larger.
I think you meant turboprop there, but the distinction I notice is that one has all propulsive airflow inside the nacelle, and one does not.
Agh. No, I meant turbofan, but I misread your post and actually completely agree with you - turboprobs are not jet engines.
Ha! It happens. Enjoy your weekend.
No, you don’t magically get the fuel back. But you do get a lot of the _kinetic energy_ back, and that energy keeps you flying without having to burn yet more fuel. You burn a lot of fuel while climbing, but then hardly any at all while descending. And that descent might cover 100 miles across the ground.
The 737-800 uses CFM56-7 turbofan engines.
[1] https://en.wikipedia.org/wiki/CFM_International_CFM56#CFM56-...
1) Yea, sorry, turbofan, not turboprop nor a jet.
2) It stays burned, but the energy is banked in potential energy of the aircraft, namely in a form of altitude. If you run out of fuel 5 feet above ground, you dont get to fly far. When you run out of fuel 35000 feet above ground, you can still choose where to land from multiple options.
3) huh? I dont get what you trying to say, but: Its always more economical to climb, and the faster the better. Ofc you cant climb too high when you intend to attempt to land in 5-10 mins, but nontheless, every feet gained is "banked", and the aircraft is more economical to run the higher you are.
4) I am not saying the winds arent a factor, and in no way I was arguing about how fuel reserves are calculated. My only claim is that: yes, by spending more fuel to gain altitude, you can then "glide" down almost for free later. Its not 1:1, because of constant losses like drag, but its being compensated by higher engine efficiency and less drag at altitude, that its always worth it to climb if you can.
There was a flight that was low on fuel diverting to alternate between 2 islands. The pilot panicked and chose slower climb to intuitively save fuel. They had to ditch the plane in water because of it - if they initiated full climb, they would have made the jump.
Wow this has a lot of replies!
Yes, you get a lot of the energy back, BUT there is a huge problem!
Large airliners incur a LOT of additional drag to slow down while landing. Some of that is entirely intentional, some is less intentional.
It is highly preferred to deploy the landing gear before touching down. Failure to do so may lead to a hard landing and additional paperwork, so airlines do not allow the captain to exercise their own discretion.
Extending the flaps maintains lift at lower speed, and higher flap settings allow even lower speed. The highest flap setting generally also deploys leading edge slats.
If the wheels of the airliner touch down and detect the weight of the plane then spoilers kill the lift of the wings, air brakes fully deploy, as well as thrust reversers.
All of these things add drag, which uses up all that energy you've been converting.
The upshot is that each landing attempt uses a LOT of energy, and you have to use fuel to replenish that energy after every attempt.
In other words, yes you get it back, but only for one landing attempt.
As someone who has ridden a bike up a big hill, and then down it, I don't think you get it back.
That is perplexing. Of course you get the potential energy back. It turns into kinetic energy as you descend. That is why you need not pedal downhill, and often even need to brake to prevent the bike from speeding up too dangerously.
> often even need to brake to prevent the bike from speeding up too dangerously.
Indeed, which is what the airplane would have done on its way down to land. So it's more like riding the brakes on your way down the hill, and now at the bottom when you realize you need to abort the landing, you are at low speed and it's quite an exercise to get back uphill to try again
100%. You are correct on that. You can’t use your kinetic energy to go around after a landing attempt.
But not because “you don’t get the energy back”. (As recursive suggested about a downhill bike ride which is the part i am disagreeing with.) You do get it back, but because you want to land you bleed it away to drag. And once it is bled away you don’t have it anymore.
So we don’t disagree about the practical implications for flying. I’m disagreeing with recursive’s particular statement about downhill cycling and what it implies about the physics of the problem.
The glider guys would always suggest a forward slip. It's a lot of fun to do. It's not taught often enough during primary training for powered airplanes.
Aren't low-speed slips something that makes planes flip upside-down when not used very carefully? (Inadvertent rudder changes corrected with opposite aileron resulting in a snap roll.)
A cross controlled stall can result in a spin (which is probably what you mean by flip upside down). The rudder changes aren't inadvertent, they're intentionally opposite the aileron input - the goal is essentially to fly somewhat sideways, so the fuselage induces drag.
In general forward slips are safe, but yes you have to make sure you keep the nose down/speed up. There's little in aviation that isn't dangerous if you aren't careful.
Yes, being that one is cross-controlled they must be used very carefully. It's really obvious that one is cross-controlling. It's the only time outside of really powerful crosswinds that you see what's below and ahead of you out of the side window. That view is what makes it fun.
You're probably thinking of a skid, which is when you put too much rudder in the same direction as the ailerons. Then the lower (and slower because it's on the inside) wing stalls first (and goes lower still) and away you go. Often when turning to land, so there's not enough altitude to recover.
Yes, but that also doesn't get any energy back on descent, quite the opposite, that is "riding the brakes on your way down"
Well it's not all lost otherwise it'd be a stall spin accident caused by performing the maneuver with too little airspeed. And that's hard to do. It's a noisy maneuver, the air slamming against the fuselage makes itself heard. Once performed it's not easily forgotten.
More dangerous than inadvertently spinning with too little airspeed is the possibility of shock cooling when relying on a forward slip for too much altitude loss. It really does need to be well-controlled.
I thought this topic was about energy gained and lost during a go-around. If velocity was V and altitude was H before the go-around, and velocity and altitude are again the same V and H after the go-around, then it follows that all the potential energy that was accumulated during the go-around (from converting fuel into altitude) has been dissipated (lost). Otherwise V would be higher the second time.
The subtopic changed from energy gained during descents to descents in general
Imagine a hill with 500 feet of elevation descent, followed immediately by 500 feet of ascent. No curves.
If you coast all the way down the first part, you'll get about 20 feet up the other hill before you need to start pedaling. This is a direct analogy to "getting your energy back" by losing elevation.
That is exactly what a rollercoaster does and it doesn’t start “pedaling” after 20 feet. Of course real systems have losses and you can’t practically use all the energy.
But you don’t have to believe me. Look at the video of this glider doing an unlicensed airshow: https://youtu.be/QwK9wu8Cxeo?si=L-0Mfmu8wk1ZlQU7
It is a glider so it can’t “pedal”. You can see it steeply descending from 5:13 to 5:30 while it is speeding up and then the pilot picks up the nose and trades some of his speed for elevation again. And then he does it again around the 7 minutes mark.
You have two buckets of “water”. One bucket is kinetic energy and the other is potential energy. You can trade one for the other. You can also “lose” from the total volume of “water” due to drag (or friction in the case of the bike or roller coaster). Or you can add more “water” to your system by pedaling or thrusting with your engines. This is just simple physics 101. Also simple lived experience if you ever have the opportunity to fly an airplane.
The more water you put in your system the leakier your buckets get. Drag is not linear with speed. That was my point.
This is because bikes cost you about 50% more energy going uphill than walking[1]. You get back everything you don't lose from having to pedal too slowly, hunch over the front wheel, and maintain constant torque on the pedals.
1: https://pedalchile.com/blog/uphill
Just as with bikes, it will depend on how slow it is descending. On "right" trajectory engines could technically be basically idle, and you save fuel flying high so it might not be all that huge loss.
No, and you don't want it. You want to be on the ground and stopped. In the lowest energy state.
It's not currently feasible to harvest it into fuel. It's (very very nearly) all lost to drag, on purpose.
How? On descent you can trade some of your altitude (potential energy) for kinetic energy, but then you can’t land the plane. For descent on an approach you’re going from low energy to even lower energy. In emergencies and with enough runway you can futz around with this some, but wiggle room on an airliner is not great, negligible to what will be expended on a go around.
Some of it. The air density is an important part of efficiency at higher altitudes, so every moment spent under like FL320 is wasted fuel.
So the entire climb "up", you are also wasting energy fighting the thick air. On the way back "down", that air again fights you, even though you are basically at idle thrust.
Your fuel reserves are calculated for cruise flight, so time spent doing low altitude flying is already at a disadvantage. "Two hours of reserves" is significantly less than that spent holding at a few thousand feet. Fuel efficiency while climbing is yet again dramatically worse
The problem isn’t getting the energy back, it’s doing so more slowly than gravity. Planes are somewhat limited in their ability to glide.
Some of it, but much is lost to drag. They do have to limit speed at all times.
Not really. While you have a large potential energy buildup at a higher altitude, you cannot "bank it" / "save it" on descent. There is no way to store it in batteries or convert it back into fuel.
One of the challenges of aeronautics is the efficient disposition of the potential energy without converting it all into kinetic energy (ie speed) so that the landing happens at an optimally low speed - thus giving you a chance to brake and slow down at the end.
> "While you have a large potential energy buildup at a higher altitude, you cannot "bank it" / "save it" on descent. There is no way to store it in batteries or convert it back into fuel."
An electric fan aircraft absolutely can recharge it's batteries on descent. The fans simply act as turbines, creating drag to slow the aircraft and electricity to charge the batteries. Large commercial airliners already have a small turbine that works this way, the Ram Air Turbine (RAT) which is used to generate electrical power in emergencies.
You can use a turbine to generate electricity, so yes, you are converting potential energy into electrical potential. However, no real mass produced passenger plane today can use that electricity for flight (thrust).
RAT is only used when sh*t hits the fan. Even then, it can help you power some hydraulics / electrical, not “store” energy for further flight.
The OP asked - in a low fuel situation, can the energy spent on a climb get effectively recovered - and the answer is not really. We convert as much as we can into unpowered (low-powered) descent. But once you are at a spot where you make a final decision to land or not, you are by design low and slow - and all that energy you had 15m ago is gone.
If you need to keep flying, those engines need to spool back up. And that takes fuel.
> "no real mass produced passenger plane today can use that electricity for flight (thrust)"
Such aircraft do exist. For example, the Pipistrel Velis Electro trainer. And more recently, the Rhyxeon RX4E became the first electric aircraft to be type-certified for commercial passenger operations.
It's likely that we'll see many more electric fan aircraft in the coming years/decades, whether powered by batteries and/or hydrogen fuel cells, or hybrids with both conventional turbofan and electric propulsion in order to improve efficiency and environmental performance.
> It has a cruise speed of about 200 km/h (\(124\) mph), a payload of \(350\) kg (\(770\) lbs), and a range of approximately 300 km (\(186\) miles)
While it’s a real plane, I think we can both agree this is more of a prototype than what the general public would consider to be a passenger plane.
Yes, energy recovery is possible. It’s not happening currently in commercial aviation.
> RAT is only used when sh*t hits the fan.
Isn't it when air hits the fan, technically?
(Sorry.)
> As others have said, final fuel reserves are typically at least half an hour, and you shouldn't really be cutting into them.
This is one of the multiple layers of defense that airlines employ. In theory, no one single failure should cause a major incident because of redundancies and planning. Airlines rely on the "Swiss-cheese" model of safety. Each layer has its own risks and "holes" but by layering enough layers together there should be no clear path between all of the layers. In theory this prevents major incidents and given the commercial airline's safety records I'd say it works pretty fucking well. Landing with minutes of fuel left should be exceptional. But it also shouldn't be fatal or a major risk due to the other layers of the system. ATC will move heaven and earth to land a plane low on fuel or with engine trouble safely. And everyone else in the system having 30+ minutes of extra fuel gives the space for this sort of emergency sorting.
I think this also reflects on the "efficiency" that MBA types bring to companies that they ruin. If an MBA sees a dozen landings with an extra hour of fuel, their mind starts churning at saving money. Surely an hour of extra fuel is too much and just wasted. Wasted because every extra gallon of fuel you take off with is extra weight you have to carry throughout the flight. Surely things would be more efficient if we could make sure planes only carry enough fuel to make their trip with very minimal overhead. And when everything goes perfectly according to plan, these decisions work out fine. Money is saved. Bonuses are paid. But the inevitable always happens. That's why it's called inevitable. Lives are lost. Wrists are slapped. Some people at the bottom lose their jobs. The world moves on.
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I thought a lot of airlines had rules to limit the number of attempts you could make at a single airfield in an attempt to prevent this exact kind of situation.
It sounds to me like they tried harder at their intended destination than maybe they should have, followed by going to an alternate airport that probably wasn’t a good choice in the first place, and then having to divert to the final airport where luckily they could land in time.
Interesting. To me it does not really make sense to think in terms of fuel left because, no matter the reserves, there can always be a situation so unlikely, so outside the ordinary, that it will drain all fuel reserves before you make it to the planned destination.
I have no clue how else to think about it though.
So maybe the thing we can improve is an understanding of likelihood?
I.e. prevent the journey from occurring if weather conditions are likely to be adverse above a certain threshold?
I'm not an aviation expert, but generally in safety engineering, safety buffers are not simply calculated as [normal situation] * [safety factor], but [worst case scenario] * [safety factor]
If you ever cut into your safety allowance, you've already fucked up. Your expected design criteria should account for all use cases, nominal or worst-case. The safety factor is there for safety, it is never intended to be used.
This is really helpful and I think I understand now.
The approach is basically “accounting for everything that might go wrong to the best of our experience, including problems arising from the complex interactions between the airplane and supporting ground systems and processes, this is how much fuel you need in the worst case scenario. And now lets add more to give us a cushion, and we will treat consumption of this last reserve as tantamount to a crash.”
Precisely.
This is exactly how it is in this case. Any consumption of the fuel reserve would result in an investigation, this is a very extreme case and it may even result in a change in the rules depending on the root cause.
Yeah idk people debating about this, if this justifiable then its all gucci and world can learn from such experience
Yes, exactly. The day it's normal to eat into the allowance is the day we start seeing planes falling out of sky for lack of fuel again. The only way to prevent that is to treat 30 min of fuel as seriously as you would 0 minutes.
Yes. Similarly, safety needs to be there even after the aging of materials over product lifetime. So basically when aging is the only variable to be considered end of life date is the worst case scenario.
"I’m a little confused by what there is to investigate at all."
You're confused why they should investigate how everyone on that flight came within minutes of dying?
Something about the fuel reserves, procedures, or execution was clearly flawed.
I think the argument is that this is precisely the tail end of exceptional conditions overfueling is designed for. If it's typical to fill fuel for 4 hours on a 2 hour flight, and the flight took 4 hours. It seems like this is exactly why they overfuel to 4 hours. If this happens once every 100k flights, then it doesn't even beg the question of "why aren't we overfuelling to 4.5 hours".
This is just clarifying the question from the perspective of an outsider.
That said, an investigation would be pretty reasonable, even if only to confirm that the abornamlity were forces majeures
> If this happens once every 100k flights, then it doesn't even beg the question of "why aren't we overfuelling to 4.5 hours".
- This does not happen once every 100k flights. That's once per day
- If this were happening once every 100k flights we would be adding another half hour to the reserve tomorrow.
Although credit is due to fuel reserve policies considering they landed after two diversions and three go arounds.
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Why not? It's a factual report stating that the AAIB has opened an investigation into a potentially dangerous incident. There's not any editorial bias evident. See other extensive comments as to why this is not just a case of "it landed, so what's the problem?".
Sensational headline completely missing the point.
Or did it work as intended? The plane had multiple failed landing attempts, was re-routed, and had enough fuel to land safely. While no one wants to cut it this close, this was not a normal flight.
I’m not an expert in this field, but it would seem that the weight of extra fuel would increase operating costs, so it’s is effectively insurance. How much extra fuel should be carried to account for unplanned events like this, while not carrying so much that it becomes cost prohibitive.
Fuel depletion is risky, but not that risky; see the Gimli Glider for a case much more dangerous than this, which still worked out amazingly well.
Edit: Here is the Wiki on incidents... https://en.wikipedia.org/wiki/Fuel_starvation_and_fuel_exhau...
That example is so well known due to how exceptional it was, especially how the pilots handled it. Robert Pearson, the captain, was a very experienced glider pilot. That's something that not many commercial pilots have.
There were also two factors in the landing, that allowed for this to happen. You're going to be coming in really fast for a landing, when gliding in a commercial jet, and you don't have access to your thrust reversers to slow it down. There was a repurposed runway, that they used to land, that just happened to have been used as a drag racing track and had a guard rail. They were able to slow down by scraping across that. It also just so happened the nose gear didn't deploy fully so scraping the nose of the plane against the ground also helped slow it down.
Needless to say it was a bunch of very fortunate events that allowed it to not end in disaster. In any case I would consider it very risky.
And even with all that scraping damage they were able to fly the plane out, repair it, and put it back in service. Amazing.
The "scraping helped slow it down" theory makes no sense to me. What do you think has a higher coefficient of friction - tire rubber on asphalt, metal on asphalt, or metal on metal?
I would hesitate to chalk it up to just theory, given it was in the NTSB report and they don't really mess around with throwing baseless stuff around. I'd be interested to take another look at it. They likely go into the material science and physics behind this very thing. They're usually filled with gems.
You also have to keep in mind, it wasn't just rubber against asphalt, it was rubber on a wheel that spins. I'm not sure if the front nose gear on a 767 has any brakes but even if it did, I can't imagine it would be sufficient at the speeds they were going.
They could have died. The nosewheel assembly being pushed up through the floor of the cockpit has killed more than one pilot.
I mistyped, as this was Canada it wouldn't be the NTSB but the Canadian equivalent at the time: Canadian Aviation Safety Board. The report is a good read.
Don't forget the surface area of contact...
Rubber likely grips much better than metal, however three wheels have massively lower surface area than the body of the plane, or even a small section of it like the head.
Of course we don't land tireless for other reasons (metal transfers heat exceptionally well unlike rubber, paint doesn't survive high speed impact, and it tends to deform upon impact with anything, making any future flights unsafe), but the fastest way to slow down if you don't care about safety or comfort would probably be to land tireless, if you could introduce some rotational spin, that might be faster (more force directed in multiple directions).
Also, on the note of "coefficient of friction", remember that this number is not just some innate property of a molecule - as the metal scratches the pavement and deforms, its coefficient of friction goes up as micro-deformities accrue.
You seem to be assuming those are "or" rather than "and"
Fuel depletion is stupendously risky, it is one of the most risky things that can happen to a jet. The only things more dangerous are fire and control systems failure.
The Gimli Glider was a case of many items of luck lining up.
You could've read at least the Wikipedia page on how miraculous Gimli Glider was.
From "all engine failure is never expected and not covered in training" to "Pearson was an experienced glider pilot familiar with techniques rarely needed in commercial flights" to the amount of maneuvers they had to execute on a barely responding aircraft
Exactly, the takeaway from that saga is that extreme luck does happen, not that flying without fuel is perfectly safe.
They also happened to know about an old airport which was no longer active, but did not know about the concrete barrier in the middle.
I know you're trolling, but for anyone that hasn't heard of Gimli Glider, look it up or watch a documentary on youtube. The stars definitely aligned to make that happen.
Depends largely on the altitude when fuel runs out. If it runs out when they're at 4,000 ft and it's windy, it's probably game over.
Fuel depletion is _not that risky_ is an interesting take. But hey, it won Chapecoense its first and only Copa Sudamericana, so maybe it isn't that bad after all?
https://en.wikipedia.org/wiki/LaMia_Flight_2933
And what happens if you're not at 40k feet when the fuel runs out?
Good thing that airliners spend so much time at altitude!
Especially while making landing attempts?
Depends if our goal is to have zero aircraft crashes. If the goal is zero, then for any given parameter, you have to define a margin of safety well before crash territory and treat breaching that margin as seriously as if there had been a crash.
Similarly planes are kept 5 nautical miles apart horizontally, and if they get closer than that, you guessed it - investigation. Ofc planes could come within inches and everyone could live, but if we normalize flying within inches, the we are also normalizing zero safety margin, turning small minor inevitable human failings into catastrophe death & destruction. As an example, planes communicate with ATC over the radio and are given explicit instructions - turn left 20 degrees, fly heading 140 etc. From time to time these instructions are misunderstood and have to be corrected. At 5nm separation everyone involved has plenty of time to notice that something was missed/garbled/misinterpreted etc and correct. At 1 inch separation, there's no such time. Any mistake is fatal, even though in theory you are safe when separated by 1 inch.
TBC an investigation doesn't mean investigating the pilots in order to assign blame, it means investigating the entire aviation system that led up to the breach. The pilot's actions / inaction will certainly be part of that, but the goal is to ask, "How could this have been avoided, and ask how every part of the system that we have some control or influence over might have contributed to the outcome"
We shouldn't aim for 0 crashes due to low fuel though. How many deaths does carrying around 3x fuel than what you reasonably need contribute to via extra pollution?
We should aim for 1 every 10-100 years or something reasonable like that.
We should account for deaths from pollution, but if we are going to do that, we should be willing to do that for 99% of aviation fuel that has nothing to do with reserves & safety margins, in addition to fuel used to drive cars.
Any regulation short of "carry infinite fuel" will be a trade-off, and entail some risk and anyone involved in setting these knows that. Zero may not be our actual target or even possible, but it is a useful aspiration to ensure that everyone is pulling in the right direction.
We dont aim for 0. Zero means dont fly. one in every 100 years globally for all flights would be very safe.
On the contrary - commercial aviation does aim for perfection.
At 3x the number of deaths would be 0 because there would be no more flights.
Well imagine they had to do a go-around on that landing. Go-arounds are extremely normal and might be done for a million reasons; your speed is wrong, your descent rate is wrong, your positioning is wrong, there's bad wind, there's an issue on the ground, etc etc etc. Six minutes of fuel is really not enough to be sure that you can do a go-around. So now, if ANY of those very normal everyday issues occurs, the pilot has to choose between two very bad options: doing a go-around with almost no fuel, or attempting a landing despite the issue. That's just way too close for comfort.
Aviation operates on a Swiss cheese model; the idea is that you want many many layers of safety (slices of cheese). Inevitably, every layer will have some holes, but with enough layers, you should still be safe; there won't be a hole that goes all the way through. In this case, they basically got down to their very last slice of cheese; it was just luck that the last layer held.
I think he would attempting a landing despite the issue in most cases because running out of fuel during go-around would be worse.
>I’m a little confused by what there is to investigate at all.
One of the most important aspects of taking safety seriously is that you do not just investigate things which had an impact, but that you proactively investigate near misses (as was the case here) and even potential incidents.
A plane with 6 minutes of fuel left is always a risk to every person on board and potentially others if an emergency landing becomes the only option.
Indeed that is the definition of a "aviation incident" where there was a risk of injury or damage. If there is actual injury or damage it becomes an "accident".
The investigations into incidents aren't usually particularly long or noteworthy and often the corrective action will be to brief X on dangers of Y, or some manner of bulletin distributed to operators.
If you cut into the final reserve, it’s a full-blown emergency requiring a mayday call.
This should not happen. So what’s there to investigate? How it was allowed to happen, and how to prevent it from happening again.
EDIT: it’s a mayday even earlier than that. It’s a mayday once the pilots know that they WILL land with less than the final reserve.
If they have to touch and go, how long would it take until they get the plane around for another approach? In fact, you might not get as far as that touch and go and have to go around. You need some margin for all of these eventualities. The likelihood is low that these happen, but they have to be accounted for.
Sure, but the flight was a lot longer than planed. How much extra do we need. They declared an emergency, and thus put themselves at the front of the line. They had 6 more minutes to do that touch and go around if that happened, and since they were already in a low fuel emergency they get priority and so there is enough time to do that if they needed. (edit - as others have noted, 6 minutes with high error bars, so they could have only had 30 seconds left which is not enough)
They landed safely, that is what is important. There is great cost to have extra fuel on board, you need enough, but it doesn't look to me like more was needed. Unless an investigation determines that this emergency would happen often on that route - even then it seems like they should have been told to land in France or someplace long before they got to their intended destination to discover landing was impossible.
> They had 6 more minutes to do that touch and go around if that happened
6 minutes is way out of the comfort zone. They might not have made it in that case.
Correct, article says they landed with 220kg which is around 6 minutes of average fuel burn over an entire flight - bit less at cruise, a hell of a lot more at takeoff/climb.
So I don't think 220kg is enough to do a go-around in a 737 (well, a go-around would've been initiated with a bit more than 220kg in the tank - they burned some taxing to the gate - but you get my point.) I've read around 2,300kg for takeoff and climb on a normal flight in a 737-8. A go-around is going to use close to that, it's a full power takeoff but a much shorter climb phase up to whatever procedure is set for the airport and then what ATC tells you.
I just flew 172s but even with those little things we were told, your reserve is never to be used.
These people came very, very close to a disaster. Fortunately they had as much luck left as they did fuel.
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That’s about as useful as opening a fortune cookie and reading it off as an answer.
Straight from the horse’s mouth: https://web.archive.org/web/20230630013840/http://www.boeing...
In the first table they list 2307-2374 kg of fuel for takeoff and climb.
You’re talking to the wrong horse though.
Isn’t a 737-8 the max 8 variant? It uses newer dual CFM LEAP-1B engines. How does it compare? I can’t really find the data. The spec you’re referring to is for the older 737-800.
Another fortune cookie:
https://www.aircraft-commerce.com/wp-content/uploads/aircraf...
It suggests an overall savings of ~14% over the 737-800 but doesn’t look at specific takeoff/climb comparison.
I wasn’t posting the LLM output as a source of truth. I was just using it to question the uncited value. And I still really don’t know the answer. If you’ve got another data source I’d love to get it.
Why do people keep insisting on pasting LLM output to HN when every time it happens, it gets downvoted to oblivion? The community clearly doesn't want it. If we wanted to know a computer program's opinion about something, we could ask it ourselves.
I was using it to question that exact stated fuel consumption number without a citation. For hard data (like fuel consumption) getting a value from an LLM isn’t absurd.
If not absurd, it's very poor form. You should never use LLM as input for a discussion, nobody wants to hear that. Use it to search for authoritative sources.
It’s fine if you post an actual citation that you might have found through the LLM. Just posting AI slop is worse than useless, though, and also unpleasantly dystopian.
ok, how do we verify that?
Maybe he should ask Claude next.
That’s the point? I wasn’t suggesting it was correct. Just that the value is wildly different from their own non-cited number. The next stage was to get a citation from an actual datasheet. Their reasoning was nothing beyond “I’ve read”
I agree, well out of comfort zones. However to my reading multiple different things went wrong to get to this point.
That could be. We just don't know right now, but your intuition may well be correct, even if there is a single root cause there could very well be multiple contributory causes.
They failed to land at two airports before the third. I can't say if they made the right decisions but that already is two failures.
Go arounds are not failures.
They are expected situations, but still a failure of the original plan.
They are not a failure of the original plan, they are a mandatory component of the original plan that if everything is nominal never gets executed. Every pilot on approach is ready for one or even more go-arounds and they happen quite frequently for a variety of reasons.
They happen a few hundred times per day at ~100 k flights.
How much extra do you need? Enough that a pilot/crew doing their job properly will never run out of fuel and crash.
So yes they will do an "investigation". It's not a criminal investigation. It's to understand the circumstances, the choices, the procedures, and the execution that ended with a plane dangerously close to running out of fuel.
This will determine if there were mistakes made, or the reserve formula needs to be adjusted, or both.
Don't tell me about cost, just stop. Let MAGA-Air accept some plane deaths to have cheap fares.
With 6 minutes left everyone could have died if anything went wrong with the final landing, even a gust of wind could have ended everybody's life.
Could have, but pilots practice no fuel landings all the time (in simulators). If they can get to ground that is "level enough" nobody dies. It is not something you ever want to see in the real world (and in the real world people often do die when it happens), but it isn't automating people die.
I don't think that's all that true for airliners. Pilots definitely practice for engine-out scenarios during all levels of training up to the airlines, but the ability of a plane the size of a 737 to safely land on anything but a runway is...limited. And if you're low, slow, and trying to go around, that's not a lot of time to glide to ground that is "level enough".
i didn't mean to imply no runway landings. Landing on grass is questionable. They would practice water landings though
Those landings are practiced from a reasonable altitude.
Surely the issue is more that they decided to make so many attempts to land local. There should be a max level of attempts.
There is a lot of pressure on pilots to land local. But 3 go-arounds happens, not often, but it does.
Perhaps that decision needs to be removed from the airline and there needs to be an independent decision maker there.
Pilots are ultimately responsible for the aircraft, that's pretty much set in stone but if ATC would tell them to divert they would unless there already was an emergency.
There is a max level, and it is three.
Well clearly that number should depend on distance to next airport and how much fuel is onboard. It isn't sensible to have a set number when other parameters change.
This reminds of discussions following the Fukushima disaster where one commenter claimed that it wasn't a design flaw, because it was an extraordinary circumstance. I found this appalling, because I do not at all think that was the risk profile that was sold to the public; I think people believed that it was supposed to be designed to safely survive 1000-year earthquakes and the tsunamis that they create.
Likewise, I think that the flying public is lead to believe fuel exhaustion is so rare that when airlines are compliant with regulations, no such disasters across all flights across all carriers will occur during your lifetime.
It's also a communication problem, because labels like "100-year/1000-year event" are easily misunderstood.
* they're derived from an estimated probability of the event (independently) happening each year. It doesn't mean that it won't happen for n years. The probability is the same every year.
* the probabilities are estimates, trying to predict extreme outliers. Usually from less than 100s of years of data, using sparse records that may have never recorded a single outlier.
* years = 1/annual_probability ends up giving large time spans for small probabilities. It means that uncertainty between 0.00001% and 0.00002% looks "off by 500 years".
https://practical.engineering/blog/2025/9/16/an-engineers-pe...
I find a useful exercise is to have a cheat sheet of historic flood heights in some area, tell someone the first record high, ask them how high they would make the levee and how long they think it would last. Peoples' sense for extremal events is bad.
That's a great exercise. Where I live a lot of people died because in the past we were not able to make that guess correctly. A lot was learned, at great expense.
I'm sure we can all remember at least one person in any situation who will say something we find memorably awful.
6 min, is empty, 6 min is purely theoretical, 6 min would not clear for ground handling or a test start, or a fuel system check,6 min would not do a go around. will interesting to see if they release info about what the real amount of fuel left is, and an authorative discussion on how much useable flight time was there. did they actualy make the taxi to the terminal?, or run out on the apron?
I think the article says that someone saw 220kg written on a log - that's about 6 minutes worth at cruise. So yeah, it's zero basically.
Yes. There is another comment above making light of the 6 minutes as if another go-around was still an option, that is a ridiculous take. They were going to bring that plane in and land it no matter what on this last run, otherwise they'd crash for sure. 6 minutes may not even be within the margin of readout.
By your logic you need an infinite amount of fuel.
If you define X the amount of fuel you need after you land.
And you say that X needs to be enough to make an emergency landing.
And we define that the amount of fuel required for an emergency landing should cover the amount required for the landing operation while still having X in the tank when landed.
X > X + landing_cost
The plane already had made 3 failed attempt before and was redirected to two different airports.
Naively as an outsider, this situation seems like everything worked as intended?
I don't remember all of the rules off the top of my head, but if you are ever landing with less than 30 minutes of fuel, something has gone seriously wrong. You are required to take off with sufficient fuel to fly to your destination, hold for a period of time, attempt a landing, fly to your alternate, and land all with 30 minutes remaining. If you are ever in a situation where you may not meet these conditions, you are required to divert immediately. In choosing your alternate, you consider weather conditions along with many other factors. This was, without question, a serious emergency.
From the very brief description in the article, I would say they should have diverted to Manchester at least 25 minutes sooner than they did. I will include the GP's caution, however:
I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
If you are ever in a situation where you estimate you will land with less than 30 minutes of fuel, you are legally obliged to declare a MAYDAY. One of the few situations where a mayday is legally required.
My understanding is that they shouldn't have spent that much time in the air (not intended as a guess for the cause). The margin is there for situations where you can't land earlier, not the margin for scheduling the landing. There is margin for expected potential delays, they were in the other margin that should never be used except in true emergencies.
Oh I think I see; so is the question not “why did they land with so little fuel”, but more like “why did it take so long to decide to redirect to a known-safe airport”?
Possibly. Or 'why did your fuel readings deviate from what was actually in the tanks' or 'why did we leave with less fuel than we thought we did' and so on. There are so many variables here speculation is completely pointless. All we know is that something went wrong, that it almost led to a crash and that it involves an airline with a very good record when it comes to things like this.
Low fuel happens, but this is (very) exceptional.
I don't know. As the parent said, I'd be careful with guessing the root cause right now. They should not have been this low even if diverted due to weather.
By asking such a question you understand the need for an investigation
Thirty minutes.
If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call.
Mayday is a term enshrined in law. It is only to be used when people will die if you do not receive help. In the US, calling it inappropriately can be punished with up to 10 years in jail and a $250k fine. It's protected in this way because as soon as you call mayday, in many situations there are actions that must be taken by law or regulation. Other appropriate uses include things like "our plane is on fire" or "our wing just fell off and we can't steer the plane".
As soon as you think you can't land with the fuel reserves you are _required_ to call mayday, other pilots are _required_ to clear the radio for you, and ATC is _required_ to provide any and all supported possible until you're on the ground.
The investigation is not to figure out who to send to jail or something. The investigation is because a flight just came this >< close to having hundreds of people die. That fuel is there as a safety margin, yes. That's how everyone ended up walking off this plane instead of dying as the plane was ripped apart by some trees somewhere. That is good.
But air travel did not become as safe as it with an attitude of "this hasn't killed anyone yet, all good". The fact there was an incursion into the safety margin should not be looked at as "eh, working as intended" but "holy hell we just came this close to disaster, what went wrong that almost killed all these people? how do we stop that happening again?". That is what an investigation will be looking to figure out.
To put it in vaguely IT terms, this is something like... your application has started corrupting its database, but you have _a_ backup copy. On one hand, you can think "eh, we have a backup, that's what it's there for, who cares". On the other you can go "holy shit, any time we need to restore from the backup we narrowly averted disaster... how do we make sure we're not in that situation again?". The former is probably going to lead to irrecoverable data loss eventually. The second will have you addressing problems _before_ they ruin you.
What is fascinating about this whole discussion is that the general world of software development is so far away from actual engineering that all of these basics require painstaking explanation.
5 9's uptime in aviation means one airliner crash a day.
> If at any point you expect to touch down at the nearest safe airport with less than 30 minutes of fuel remaining, you are required by regulation to make a mayday call.
From the article, they did issue a mayday call, when the closest airport was presumably Edinburgh. Then they flew to Manchester and landed.
There must have been a very good reason to do that.
>One pilot who reviewed the log said: “Just imagine that whenever you land with less than 2T (2,000kg) of fuel left you start paying close attention to the situation. Less than 1.5T you are sweating. But this is as close to a fatal accident as possible.”
Only issue I see is that should there have been stricter rules to diverting way earlier. If winds were such as to make landing harder. Would just directly going somewhere else been the correct choice to force.
It also sounds like they went to an alternate airport they probably shouldn’t have bothered with.
Well, if you know you're pretty low on fuel, you are likely to pick an airport where the weather is good, rather than risking three more missed approaches at a closer one where the weather is probably also bad.
Of course, Manchester is also a Ryanair base. There are two Ryanair bases closer to Prestwick (Edinburgh and Newcastle), but maybe the weather was bad there too? If the fuel situation was so dire, questions might be asked during the investigation why they didn't pick a closer airport with good weather that wasn't a Ryanair base (if one existed), but ultimately it's the pilots' decision to fly a bit further to an airport they are familiar with, and second guessing them with the benefit of hindsight is probably not a good idea...
They made two attempts to land at Prestwick, then diverted to Edinburgh (which also had bad weather). After one attempt at Edinburgh, they then diverted to Manchester.
This is likely one of the questions the investigation will focus on.
If you get shot, but had a bullet proof vest on, and hence didn’t die, technically everything worked as intended.
Personally, I’d still want to figure out why I got shot and work on making sure that didn’t happen again.
Especially if you basically got shot multiple times (for an analogy in this case).
> I’m a little confused by what there is to investigate at all.
So because the safety margin still worked while down to near vapors we should conclude there's nothing to learn for the future to reduce the risk of similar incidents?
That's certainly... a take.
Flight from Edinburgh to Manchester is just a bit more than 1 hour, so after trying 2 landings, diverting to Edinburgh (15-20 minutes flight), 1 more landing attempt, well, you get very close to 2 hours.
I felt like that seems a little long from EDI to MAN (after all, EDI to LHR is typically a flight time of under an hour!), so:
https://globe.adsbexchange.com/?icao=4d2256&lat=54.720&lon=-... is the track of this flight.
Went around at EDI at about 19:10Z, landed at about 19:51Z, so about a 41 minute flight.
Right, I probably got the information for flight time as seen by a passenger on a ticket, not for a plane already flying. Thanks!
Whether it can be prevented in the future. Should planes fly with even more reserve fuel? It's possible. Or maybe different ways of selecting alternate landing sites?
It may even be the answer is "no, everything went as well as it possibly could have, and adding more reserve fuel to every flight would be unacceptably wasteful, so oh well", but at a minimum they'll probably recommend even more fuel on certain flights into risky weather.
Similarly naive outsider, but I've read things here and there. My understanding is that they should have declared mayday (emergency) and landed (potentially at another airport, potentially in the middle of nowhere) _way_ before so that when they have landed they still had 30 minutes or more of fuel in the tanks.
Imagine you're standing on a balcony and discover that the supports are cracked almost all the way through.
Do you shrug and say, that's why they have a safety factor, everything worked as intended? Or do you say, holy crap, I nearly died, how did this happen?
The purpose of the safety factor is to save you if things go badly wrong. The fact that it did its job doesn't mean things didn't go badly wrong. If you don't address what happened then you no longer have a safety factor.
I think a more insightful answer is how often is it acceptable for the reserves to actually be cut into. If this was happening often, then there’s a likelihood of a future disaster. As it is there is 1 isolated case that still ended with a positive outcome. I think it almost adds support for the current reserve levels to be pretty dialed-in.
Officially: never. Unofficially, a minute or two would be cause for concern and the regulators would most likely be showing an interest. The airline may have a higher margin than the official one. This is exceptional, they were within the margin of error on readout and the pilots must have known that. It's one thing to know you have half an hour of fuel give-or-take in the tank it is another to know that give-or-take you are running on fumes.
The answer is 'never' as the reserves are only added for worse-than-worst case scenario, i.e. in this case something went literally unimaginably (as of then) wrong.
Might not be about fuel but about why they even tried instead of diverting earlier.
Might even be 100% done by the book but book needs changing (tho I doubt that, it's not exactly first case of "a lot of bad weather")
Our definition of 'bad weather' is definitely changing as we gather more data.
Besides regular weather (which airliners aim to avoid except during take off and landing) there are many other factors at play here. There are several almanacs that are used for fuel calculations & navigation, they are updated annually.
The fastest jet stream (the aviation equivalent of the trade winds) recorded is north of 400 Kph, having that with you, against you or perpendicular to your flight path will have a substantial influence on fuel consumption and flight duration.
I agree with you that it may well end up with a regulatory change but that's one of many possible outcomes here. I will definitely keep an eye out for the report on this flight's investigation. It is going to make for very educational reading.
> How much fuel should they have landed with?
I think about 30 minutes worth of fuel.
Not knowing their flight plan, it could have been that Edinburgh was the first alternate and Manchester the second alternate.
I dont know but maybe they should have diverted sooner. Maybe an hour into the flight?
30min+
Yes, I believe this is correct for this model aircraft.
ideally, enough to divert to another airport, in the off chance something happens, like a pending emergency at point post.
At what point should they investigate?
0 minutes?
-1 minutes?
Anything less than 60 minutes would be looked at by the airline, anything less than the legally required amount (30 minutes for a jet of this type iirc) will result in a very serious investigation. Note that for slower aircraft (for instance a turbo-prop) the time requirement goes up not down because they may have to spend more time in the air to reach an alternate (or secondary alternate, if things are really bad, like what happened here).
They should investigate after the first failed landing, regardless of the amount of fuel in the tank.
Go arounds are perfectly normal and are not a 'failed landing', a failed landing is a crash.
One of those YouTube channels where a professional pilot evaluates flying incidents had a similar incident when the pilot started yelling at the tower when they tried to make him go around again. He essentially said he would declare an emergency if he didn’t hear different instructions. I think he had 10-15 minutes when he touched down.
One of the things the reserve is for is if the plane immediately in front of you fucks up the runway, you now have to divert to the next airport. You need at least enough fuel to get there and for the tower to shove everyone else out of the way so you can make an emergency landing.
There are other reasons someone could abort a landing and have to go around again, besides debris in the runway. And sometimes two of them can happen consecutively.
In the case I’m referencing, it was pointed out that p the pilot made things worse by going faster than he was told to fly, using up fuel and also making him too close to a previous plane which forced him to go around the previous time, so it wasn’t all the tower.
Really? Equally as an outsider - it feels like one "go-around" and you're fucked.
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I have known former air traffic controllers that won't fly certain airlines because of a notorious habit some have for queue jumping by claiming they're low on fuel. If they are low on fuel is something else, but in any case when the ATCs have noticed a pattern then something is up.
This situation sounds a lot less nefarious, but it does also sound like they should have rerouted earlier.
Since there's a lot of confusion in the comments below I'm going to hijack one of the top comments to make a couple points clear from the article and FlightRadar24 data: [1]
They did reroute earlier. It was 2 failed attempts on Prestwick (Glasgow), 45 minutes in the landing pattern, then they diverted to Edinburgh (15 minute flight), a failed attempt at Edinburgh (~5-10 minutes), and then they diverted to Manchester (45 minute flight) and landed successfully there. Likely they hit their reserve just as the Edinburgh landing failed and decided to fly to Manchester, with clearer skies, rather than risk another failure in their reserve.
IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately. But this is somewhat understandable: first of all, dropping the passengers off at Edinburgh (an hour drive from Glasgow) is significantly less costly and less inconvenient than dropping them at Manchester (an overnight bus ride). Second, if the Edinburgh landing had been successful they would not have eaten into their reserve and no investigation would've been needed. Third, the Monday-morning quarterbacking could've easily gone the other direction if they had diverted to Manchester ("Why did you choose an airport 178 miles away and risk eating into your fuel reserve when Edinburgh was right there?")
[1] https://www.flightradar24.com/data/flights/fr3418#3c7f91f4
> IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately. But this is somewhat understandable: first of all, dropping the passengers off at Edinburgh (an hour drive from Glasgow) is significantly less costly and less inconvenient than dropping them at Manchester (an overnight bus ride).
Yeah, as someone who knows next to nothing about airlines, but has seen these type of decisions in businesses, this was the thing that stood out to me. This is all pure speculation of course, but I'd be curious how clear it was that Edinburgh would also have a high risk of being unsuccessful and whether the pilots felt any pressure to try that anyway. E.g. are there consequences for pilots who cause delays for passengers?
> E.g. are there consequences for pilots who cause delays for passengers?
I'd imagine heavily depends on how often that happens vs other pilots on same route. Tho I'd imagine consequences are "here is more training".
Quick note that Preswick is not really Glasgow (35 miles away) and Glasgow has its own airport which presumably was also affected by the same weather so they couldn't divert to that. Between the Scottish lowlands (where they had already tried all the commercial airports) and anywhere else, Manchester is about the closest option.
As someone totally ignorant of British airports, a Google maps search for "airports northern england" shows Teesside, Carlisle, and Newcastle all significantly closer to Edinburgh than Manchester. Are these not places where a 737 under emergency could land? Or was the weather also bad there?
Carlisle is small (and not currently licensed for public use) - not an ideal place to drop a 737 if there's a choice. It's also not that far from Prestwick so may have had similar weather. Newcastle and Teesside are both on the East coast and likely to be affected by similar weather to Edinburgh given the storm coming in from the North East. The next closest will be Manchester or Leeds/Bradford, with Manchester being larger, closer to where passengers want to go (Glasgow) and further away from the storm.
There's precedent for this kind of situation to generate quite extensive investigations. An incident in 2017 where a flight from the Isle of Man to Belfast was unable to land in a storm, diverted back to the IOM, then landed in unsafe weather conditions because of insufficient fuel to divert again got a 48 page report[0], safety recommendations, and the airline being banned from the UK.
[0]: https://assets.publishing.service.gov.uk/media/5a82ede440f0b...
Leeds/Bradford is on a plateau and can get affected by wind.
> Or was the weather also bad there?
That's likely, these places are not very far apart, and weather systems that cause 100mph winds don't tend to be small. And presumably if you have at most one landing attempt remaining you don't want to be taking any more chances.
Carlisle is a small domestic airport. The other two might have been affected by the storm as well. The weather was bad enough to down trees in London.
> IMHO the only questionable pilot decision here is to divert to Edinburgh rather than Manchester immediately.
The decision will have been made based on the forecast weather at Edinburgh prior to the flight (that is used to select a suitable alternate), and the actual reported weather at the time. Both the forecast and actual weather are precisely reported in an aviation weather language ("TAF" and "METAR") and assessed objectively. The investigation will certainly consider if the pilots erred there. Mostly likely the outcome will be that the decision was the correct one given the weather information they had available to them - this is what has been found in similar previous incidents.
To me the 45 minutes in the landing pattern also seems questionable.
At the point they left it, they still had about an hour and 20 minutes of fuel remaining, with an alternate airport 20 minutes away. They had not declared an emergency, so they were in with any other traffic waiting for takeoff and landing. (Which does make me wonder, did any other planes try to land at Prestwick at the time and how did they fair?)
so the pilot fucked up either way right????
when you piece it together like that its a close call and maybe a hindsight but its understandable if pilot do this
Claiming you're low when you are not is going to cause a major headache for the PIC, they're going to have to write that up and they may well be investigated. If it turns out they were lying they would likely find out that that is a career limiting move and if it happens too often then that too should result in consequences. The main reason is that your fake emergency may cause someone else to have a real one.
What’s the mechanism for them to get caught?
When you declare a fuel emergency or even urgency, there's often follow up to figure out why (mechanical issue? problem with dispatch? problem with flying technique? exceptional weather condition that could be forecast better? etc). And there is plenty of data in aviation to know what happened.
Dispatch knows how much fuel they say they put in.
Your flight time, speeds, and profile are known.
ACARS may be reporting fuel use throughout the flight.
etc, etc, etc.
Random spot checks. Every day at every airport some of these will get verified. Also, the next pilot would have to be willing to cover for you because they are going to have to falsify their records to make your trick invisible. You record the amount of fuel in the tank when you take command of the aircraft, the amount of fuel that was loaded and from that it is trivial to compute how much was left the last time it landed.
Lets say a plane crew claims low fuel.
The pilot in charge has to file a writeup.
When someone accepts the writeup, there's a random chance it's selected for followup. If/when they discover there was enough fuel, it will affect the career(s) of person(s) involved.
First, generally, people don't like having to do paperwork, and especially don't like doing paperwork to help you land a little quicker.
While one time may not be a fireable offense, you will find you career affected in the number of ways people can find to be uncooperative with you, or not support you when you attempt to advance your career within the company.
Developing a habit would lead your interlocutors to escalate the situation, which would lead to discipline up to and including the company firing person(s) involved.
Which airlines? I feel like if this is an issue we should be naming names.
RyanAir is famously one of them.
Edit: I was recalling articles claiming the company purposely fueling less than other airlines in order to increase their rate of claims for priority landing to have a better "on time" statistics.
This forum post disputes that: https://aviation.stackexchange.com/questions/38501/is-it-tru...
also carrying less fuel does save on fuel usage
No way.
Having attended meetings at ICAO I can also tell you many details of various aviation incidents, including their existence, are covered by some secret classification. This fact being disclosed caused most of the attendees to lose all hope in the rest of the proceedings. To their credit the FAA reps on that occasion were by far the most reasonable gov representatives in the room, and the FAA are one of the major voices pushing for greater transparency on it.
Which specific civil aviation incidents are covered by some secret classification?
> Which specific civil aviation incidents are covered by some secret classification?
You would have to have secret clearance to know which ones
It's cool, I have Top Secret Level 3 (Omega Sector) clearance so you can go ahead and tell me.
It’s generous of the classifying authority to send to the ICAO meeting somebody both appropriately credentialed to know about the information in question, and willing to talk coyly about it. Did these additional incidents inform the policy discussions at the meetings you attended?
It's funny you say that, because the way it happened was it was blurted out by a diplomat from a certain country, at which point most of the regulators facepalmed and all of those of us from outside were having the same reaction as many here.
The whole subject of discussion prior to this was efforts to improve data sharing wrt incidents.
Kinda surprised there's no data link for that sort of telemetry so that you don't necessarily have to take the pilot's word for it.
Second guessing a pilot saying they have a problem is a really bad idea. ATC second guessing an emergency is a really bad idea. Making a pilot explain why they're actually low on fuel, despite whatever some computer is saying, instead of focusing on flying the plane is a really, really bad idea.
Also, that sort of telemetry does exist for most major airlines, however it goes via satellite to the airline not the ATC.
I am not saying you are wrong, but both Type I and Type II errors are problematic. What if the pilot is wrong?
Korean Air Flight 801 could have used someone 2nd guessing a pilot. They didn't until they were almost dead and then it was too late. Not 2nd guessing the pilot was a really really bad idea.
If the pilot is wrong you hope the copilot or someone else on the crew picks up on the error and corrects it. If they’re both wrong, or if they don’t feel empowered to challenge the pilot like in Korean Air 801, everyone is usually fucked.
ATC doesn’t have the kind of situational awareness or manpower to fix these kinds of problems the vast majority of the time. It only seems like they could have done something after the fact when the disaster has already happened and hindsight activates.
Like the GP said, ATC second guessing pilots is a really, really bad idea. A few incidents doesn’t change that.
That specific incident resulted in a lot of changes to the rulebook and some very specific notes about training in terms of cultural differences.
> Korean Air Flight 801 could have used someone 2nd guessing a pilot.
...yeah, the second pilot. And in this case, also flight engineer.
IIRC The problem was pretty much aside from errors the cultural issues with pilots, the "lower ranks" wouldn't dare to be assertive to seniority and just voiced the issues they saw without doing anything.
I expect that they take the pilot's word in case of a rare situation [1] and then make the fill a ton of paparwork to try to solve the main cause and also discourage lies.
[1] In one case someone mixed imperial and metric unix, and instead of $something-kilograms, they put only $something-pounds of fuel.
This incident is known as the Gimli Glider and was actually due to multiple failures before the pound-kilogram issue (and the backdrop of Canada's then-recent metrication) even became relevant: https://en.wikipedia.org/wiki/Gimli_Glider
Would that be more reliable than just ensuring there are consequences for lying?
Perhaps. If the pilot knows that the ATC can see he's full of it, he might be less likely to lie.
Those who still do can be grounded and be moved into management or take up a career in politics.
Putting a theory of "you shouldn't trust pilots" into ATC breaks the entire system.
It is a system built out of very regulated parts, very professional people, and tight controls.
Pilots are encouraged to be very forward and proactive about fuel situations because of https://en.wikipedia.org/wiki/Avianca_Flight_052
Minimum fuel requirements are calculated as "Time of fuel for cruise to certain points", which is usually good enough, but if an Airport is stupid busy, or has bad wind patterns, just a couple go-arounds will chew through your fuel way faster than the regulation expects.
Turbofan engines are also dramatically less efficient at low altitude than high altitude cruise. So holding at low altitudes because a congested airport is dealing with traffic will chew through your reserves much faster than you expect.
Ryanair flies short hops to congested airports. They will have relatively low reserves, and you should expect them to run into "Hey we are low on fuel" more often than international flights for example.
> It is a system built out of very regulated parts, very professional people, and tight controls.
also worth mentioning that most of the civil aviation regulations and SOPs regarding commercial flights are written in blood.
"It is a system built out of very regulated parts, very professional people, and tight controls."
Locally, this is true. Globally, not so much. I remember my friend's vivid description of a flight taken in Nepal. It was absolutely wild.
I mean, obviously, it's better to trust the pilots, but if they are jumping the line because "fuel low" when it's not low, well, they're not being very professional, are they?
I’m surprised the “fuel on board” isn’t something communicated via transponder considering previous low fuel emergencies/crashes.
It wouldn’t change anything. The line between a “mayday - fuel emergency” and any other flight waiting for a landing slot is crystal clear. Of course, in low-but-not-emergency fuel scenarios the pilots can request priority, but the ATC don’t have to oblige them.
As a rule airline pilots don't lie about this stuff. They take safety pretty seriously.
Might be useful for fire crews in an emergency. Maybe have data for souls on board also.
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"claiming they're low on fuel"
It is almost fascinating how humans will stoop to dishonesty even in banal situations - and not just any humans, but pilots, who should be subject to at least some vetting.
Maybe planes should be retrofitted as to transmit their actual fuel state including a qualified assessment in minutes to the ATC. Not just because of the cheaters, but also to warn the ATC in the rare case that some plane crew isn't very assertive about their dwindling fuel, or hasn't noticed the problem.
It would make prioritizing the queue a bit more neutral.
If I designed such a system from scratch, "remaining fuel" would be part of my telemetry.
>If I designed such a system from scratch, "remaining fuel" would be part of my telemetry.
Careful what you wish for. I'd rather people skip the queue by pretending to be low on fuel than people skip the queue by actually being low on fuel.
You mean that ATC would abuse their position by making planes circle as long as they have some fuel left?
No I mean people would take off with less fuel so that by the time they reach their destination they could skip the queue
This is provable, though (there are regulations that say how much fuel you must have at takeoff - enough to divert comfortably to a suitable airport + some reserve for circling), and could be heavily punished. Up to the withdrawal of necessary licences.
And the reason why those fuel reserves exist is to be a guard band allowing situations like this to happen without flames, wreckage, and death.
Having worked with many US airline pilots over the years, this is also why they are so proud to be unionized. Sure, senior pilots make as much as some FAANG developers, but the union is also there so that management doesn't get bright ideas about things like cutting fuel reserves to cut costs without the union telling them to stuff it.
Management can't cut fuel reserves, not because the pilots are unionized but because there are some very strict rules about these fuel estimations prior to take off and margins be damned. And those rules are exactly there because otherwise this kind of incident would happen far more frequently. But it's regulation that is the backstop here, not the pilots.
The point is that the unions are there to allow the pilots to advocate for all kinds of safety-of-flight related things like fuel reserves, crew rest, and so forth that management would be happy to cut to save money. And to do so without fear of retaliation.
And if you don't think the airlines would love to lobby Congress about the regulatory backstop, well . . .
As I wrote elsewhere in this thread I actually wrote software to estimate the amount of fuel a jet should load to comply with the rules. This was commissioned by the airline and they were scared shitless that they would ever be found to be in breach of the regulations on this aspect. It is one of those red lines that you really do not wish to cross. There are other aspects of flight where you are right but this particular one is different.
The main reason why airlines would like to take the least amount of fuel is because it immediately increases payload capacity and thus flight efficiency. This being a cut-throat market there is a serious incentive to cut it as fine as possible. So the regulations around this particular issue are incredibly strict: you have to have a certain amount of fuel left upon landing, you have to write up truthfully how much you still had left and you will be investigated without fail if you cut into the reserve. The good thing about unions here is that they help to make sure that pilots know they are safe reporting truthfully because the airlines can not retaliate if they would pressure the pilot to not report an incident (which all pilots would normally definitely do). So they're a factor, but it is the regulator that writes the rules here and they are super strict about this.
And that's immediately why the calculation of the estimate becomes so important: you now have 30 minutes (or 45, depending) of deadweight + the deadweight for two alternates and an x amount of time in a holding pattern, plus up to three go-arounds. That really adds up, so you have to do your best to get the calculation as close as possible to what it will be in practice without ever cutting into that reserve.
It took me the better part of a year and massive amount of learning to write a small amount of code + associated tests to pass certification. It also taught me more about software engineering (as opposed to development) than anything I did up to that point in time and it made me very wary about our normal software development practices.
As an aviation fan just reading this thread is quite eye-opening in terms of how much risk tolerance the average commenter has vs what is standard in the aviation community and on aviation forums. It's almost like peeking into two different worlds. I wonder if there would be any value in teaching an "engineering when lives are on the line" or "war stories from accident investigations" classes to new engineers. I feel like there's value in appreciating just how much more work goes into building a system where people's lives are at stake.
Yeah it bothers me to no end with the "engineering"-inflation of various jobs.
Like, I'm definitively not an engineer, nor does my day job really involve engineering, yet my title contains Engineer! I'm a proud CRUD monkey and designer.
I have done engineering work previously when developing hardware, and it's really a different mindset (even in an agile & fast-moving engineering org). Safety, cost, reliability, multidisciplinary integration, etc. just don't really come up in a lot in web and app development (which is a wonderful thing, really—I love it!)
It is an endless source of frustration to see poorly engineered software solutions powering critical systems.
> I wonder if there would be any value in teaching an "engineering when lives are on the line" or "war stories from accident investigations" classes to new engineers.
There would be immense value in that. But who is going to pay for it? It's a course that will essentially cause your crew to start producing software at 1/10th the rate they would otherwise do.
The average commenter here is a software guy. I imagine for the average software guy a Master Caution would be like a minor compile-time warning, i.e. feel free to just disregard it. :)
That would be funny if it wasn't uncomfortably close to the truth.
I think the literal fear of death _might_ be motivation enough for pilots to advocate for safety? And if they want to fire you, would you want to work for them anyways?
> I think the literal fear of death _might_ be motivation enough for pilots to advocate for safety?
You'd think, but individual humans are very very bad at estimating risk, and in toxic group and work situations, humans will often take on increased personal risk rather than risk conflict. I.e., they will value group conformity over their own safety ... especially if their paycheck is involved. Fear of death is not nearly as powerful as robust regulation and unions.
Famously, this fact is also why no one drives recklessly and no one has lost any limbs with power tools.
The alternative to employment is death. Many people are willing to take a possible chance of dying to avert a certainty of dying.
Regulations are paper. Who enforces the behaviour, of whether to take off or not, on a windy night in central Italy?
Of course the pilots are the backstop, and the unions are theirs, so they can make necessary calls the money doesn't like.
The union is a nice backstop for issues around the edges that come up with corporate, but the real backstop is the pilots’ licensing. By making them directly responsible for the plane as PIC, it gives them leverage over their employer that few other professions have. AIR-21 gives them significant protection from retaliation and the ASRS is confidential. ALPA helps them navigate that mess if it comes to it, but that’s the real legal backing that pilots have.
Same thing happens with Professional Engineers regardless of whether they are employed or work as independent consultants/firms. They’re legally responsible for the bridges and other infrastructure they sign off on with laws protecting them from employers and clients.
(I fully support the ALPA and other unions, I just don’t think it plays as significant a role in following regulations as you claim)
...that regulation is text in a database. It can be changed capriciously at any moment, like they often are.
It takes people with ideas and a willingness to put pressure in the right places to be sure that sane policies prevail.
I think it's pretty obvious that as time moves forward, we need to rely on "regulations" less. The root and history of the word in the political context is to make things regular. But state actions increasingly bring irregularity to the world.
It seems absolutely fair to say that, in this situation, the people - the pilots in particular, but also cabin crews, ATCs, engineers, and their unions, are the backstop worth observing and celebrating.
If you land with less fuel than the legal minimum you are going to have a lot of explaining to do, there will be an investigation and you, the pilot and the airline will get enough headache from it that you will make bloody sure it does not happen again. The pilot(s) may not be able to fly until that investigation has run its course, the airline may get fined or warned if this is the first time it happened. In an extreme case the pilots may lose their license.
> It seems absolutely fair to say that, in this situation, the people - the pilots in particular, but also cabin crews, ATCs, engineers, and their unions, are the backstop worth observing and celebrating.
I will hold off on that conclusion until the report is in. There are so many possible root causes here that speculation is completely useless, and celebrations would be premature.
My apologies - I didn't mean to speculate about this incident in particular, but about the general role of so-called "regulation"; I thought it was unfair to minimize the role of the people and unions compared to the (in my view, comparatively flimsy) legislation.
I think the thing that's being pointed out as overlooked when praising the employees and the unions, is the regulators, who are the people who play a very large part in making sure that the regulations are enforced. The regulations are just text in a database, but it's the regulators who actually make it happen. A pilot who wants to push back against a beancounter cutting corners has a union and a regulatory agency to back them up.
> Sure, senior pilots make as much as some FAANG developers
That's a funny way to phrase it. I'd probably go the other way and say "sure, FAANG developers make as much as some pilots..."
Those pilots have hundreds of lives on the line every day.
Yes. I think the average bus and train driver is completely underappreciated as well and they have a massive responsibility too. I know I could not do their jobs, it would weigh on me too much.
Those FAANG devs have milions of (social) lives on the line, though. Every day.
Is this a joke?
> I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened, the one thing that I know for sure is that it shouldn't have happened, no matter what.
Just watch Juan Browne, he usually turns out pretty good in analyzing the mishaps. He didn’t upload anything for Manchester yet but will probably soon: https://youtube.com/@blancolirio
I'm also a Blancolirio subscriber. Juan also doesn't try to get ahead of the investigation, really. It's part of what makes him a valuable voice in the space.
Anybody that does isn't worth listening to.
I remember this stuff being a bigger story for a short moment x years ago, where low cost carriers (it might have been Ryanair then, too) routinely flew with unreasonably small amounts of "backup" fuel and had to declare emergencies in order to get on the ground safely.
I guess they're trying it again now that the whole thing had blown over.
Pretty obviously not the case here if you read the article.
Yeah, again, I’m going to wait for the Mentour Pilot analysis on this one.
> it shouldn't have happened, no matter what
You hear that a lot, with Ryanair stories.
Sounds like a great airline!
Ryanair has an impeccable safety record.
How many go-arounds and alternates are usually accounted for? Assuming EU, high-airport density etc, typical 2h flight.
Does the estimation change depending on weather forecast, season of the year etc?
3 go arounds + 2 hours in a holding pattern should result in at least 45 to 60 minutes left in the tanks after landing. Depending on the kind of aircraft that can be a pretty impressive amount of fuel.
> Does the estimation change depending on weather forecast, season of the year etc?
Yes. There are many factors that go into this including trade winds (which vary quite a bit seasonally and which can make a huge difference), time of day, altitude of the various legs, route flown, weather, distance to alternates, altitude of the place of departure and altitude of the place where you are landing, weight of the aircraft, engine type, engine hours since last overhaul, weight of passengers, luggage and cargo, angle-of-attack and so on. The software I wrote was a couple of thousand lines just to output a single number and 10x as much code for tests, and it was just one module in a much larger pre-flight application.
I can only imagine how the test suite looks like. Wild.
This made me think about the fuel itself: is aviation fuel globally standardised and the same quality in every single airport in the world?
The test suite was much larger than the code. It took ages to get it certified, the calculations had to be correct to the last significant digit on reference problems to prove that the algorithms had been implemented correctly. This caused a bit of a headache because the floating point library that I used turned out to be slightly different than the one from the benchmark.
There are three different kinds of jet fuel and all are produced to strict standards, and then there are allowances for ppm water contamination (very low, to ensure the fuel system will never freeze at altitude or in freezing weather on the ground or at lower altitude).
"make speculative statements"
isn't this 99 percent of modern infotainment "journalism" though? making speculative statements, omitting and lying..
Yeah, to give some idea, I believe the technical term that would have been radioed from the pilot in this situation would have been "mayday fuel."
I'm just curious, is this hard on the fuel pumps? I've always been told to not run gas down in your car because the pumps will get hot.
The pumps are fuel cooled, but it's designed such that the pumps remain in the fuel even in a low fuel situation.
>I'd be very wary to get ahead of the investigation and make speculative statements on how this could have happened
>Ryanair
I wouldn't be so wary.
Very insightful, thanks. Glad everything was ok.
All I had to contribute was to ask if they were trying to hypermile or something?
This honestly makes me think that we're missing a trick if an option for this sort of circumstance can't be "send a military fuel tanker up to refuel them in air" as a last ditch emergency measure (which IMO you would've triggered in this exact scenario).
The argument in favor is simply that we need in air refueling for the military, but justifying all that expenditure is a lot easier if it's dual use technology.
Isn't midair refueling notoriously difficult to get right? The headlines would become "airliner crashes after crew couldn't thread the needle for 45 min"
It's a ridiculous proposition.
Do forecasted storms go into the fuel estimate formulas?
Yes. Even not forecasted storms in the form of a probability of wind at low altitude when the engines are at their least efficient. And tradewinds at altitude, which are quite variable as well.
const estimateFuel = (distanceInKms, litersPerKm) => distanceInKms * litersPerKm;
I don't even know what I'm talking about, but you at least forgot to account for headwinds and differing drag amounts at different altitudes/speeds.
The big one is the trade winds. Those can really kill your efficiency on long distance flights.
Yes it was a bit of humor, sad it didn’t land.
Under FAA rules this was a screwup. [edit: see my own reply] (However, the rules are subtle, so they can be partially forgiven.) However, I'm not only a dispatcher but also a philosophy BA, so I've found a good way to explain it.
Your reserve fuel (the "extra" fuel over what the actual flight burn) can of course be used (hello, that's what it's there for) but—and here's the rub—you can never plan on using it.
That is to say, in this case, when they missed their first or second approach, they CANNOT say, "We'll use our reserve fuel and make another go at it" because that would be intentionally planning to burn your reserve.
You may only dip into your reserve when you have no other choice. In this case, when the only fuel they had left was reserve, they are obligated by law to proceed to the alternate airport, which clearly they did not do [correction: they did do the proper thing; see my 2nd reply below]. No bueno.
[this is a slight simplification (minor details omitted for brevity) but the kernel of the issue is properly described]
Update: OK, if *Edinburgh* was their alternate and they missed there and were then forced to bugout for Manchester, that's then an example of when reserve is OK to be burned. (The 'slight simplification' I omitted was unpacking how the alternate fuel plays into the process, but here, that was a key part of the series of events.) That's what I get for not reading TFA first :-/
Not really, you should have enough fuel to make it to multiple alternatives or make emergency landing somewhere else. You should never burn that last 45 mins unless you want to make the news and file a lot of paperwork.
The regs are quite specific on if and when we need an alternate, which is weather dependent, and what your fuel requirements are. And we don't really have the idea of "multiple alternatives", but I guess it's implied by the additional reserve - what us Americans call a reserve or the Europeans call "final reserve". In case you're curious, we use the TAF (termimal area forecast) to determine if we need an alternate, and use a 1,2,3 rule which is 1 hour before and 1 hour after arrival time we need ceilings of at least 2000 ft and 3 statute miles of horizontal visibility.
Er.. and maybe crash and kill yourself, all your passengers and crew and people on the ground.
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I'm curious why you did that? It's not a very complicated sequence. The whole point of engaging in a discussion here is to think about the issues raised and offer a point of view while incorporating other perspectives into yours. You've spent your money to bypass the whole intent of this site; akin to you being hungry then sending someone else to a restaurant for you so you can later read their review of the food.
EDIT and you of most of the commenters here, with your industry background, are better placed to offer an opinion!
> It's not a very complicated sequence.
For me, it was. I have trouble forming a mental model of itineraries so I’m grateful for the summary.
Why? I saw no upside to reading a layman's media source and teasing out the sequence, which is all I wanted to know. I read NTSB reports for pleasure and my favorite YT creator is Blancolirio. There's an infintesimal chance that the story had any juicy details I cared about. Also, it was work hours and I really didn't have any more time to devote to topic. I was in a rush to get my take out there, since I am a legitimate SME.
I think you missed the point.
Presenting information in different ways is useful (and the method of display can offer informational insights itself). And for different users it might help parse larger connections. And by using the LLM to summarize just that one facet of the problem (itinerary and sequence) and sharing it here, they’ve contributed in a meaningful way. It may not have warranted a response. But it added to overall understanding of the problem space to help facilitate discussion. And they did well enough by citing that the info came from an LLM. They didn’t bypass the intent of the site. They added to it and fell right in line with that intent.
Okay that's fair.
I had no issue with the contribution itself, the route summary is helpful.
> And they did well enough by citing that the info came from an LLM.
In terms of acknowledging AI contribution, you're damned if you do, damned if you don't. Here it's sidetracked a discussion; but transparency is better than otherwise I suppose. Perhaps it just boils down to taste - and I don't like it.
Anyway, you made me think!
You also made me think. I think the problem lies in the nature of “threaded” discussions. The information was useful, but it wasn’t necessarily a “reply” to any particular comment. But, the design here leaves no other choice when adding it. It maybe doesn’t make sense as a top-level comment either. It’s almost like we need to have…side comments? Asides? Like a place to just drop in relevant tidbits and informational helpers rather than a true “comment”. Maybe it’s as simple as having a means to turn off replies to signify that a contribution was an “relevant aside”.
But yes, in a perfectly meta way, I think we’ve both thought more about the nature and design of web comments and information and the implications of LLM-assisted chat ‘augmentation’. (All those AI summaries forced upon us in every site is probably the worse implementation of this!)
With all due respect, you are the one that sidetracked the discussion, not the person that acknowledged AI
Thanks, I appreciate it!
Even though I’ve read the entire article, I found it very difficult to mentally visualize and ended up not noticing that there were three destination airports involved.
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"Under FAA rules this was a screwup."
Not necessarily. And I get that you've caveated yourself with an edit and a reply etc, but lets assume that you're not hedging for the moment.
They carried required reserves on departure. Multiple approaches thwarted by extreme unforseen weather. They declared Mayday Fuel, which is mandatory under EASA regulations, when reserve fuel use became unnavoidable. They diverted to the nearest suitable airport.
Landing with 220kg is close, but within bounds of a declared fuel emergency.
Crew decision to declare Mayday and divert was proper airmanship, not negligence.
Yes, reserve fuel may not be planned for. But it may be used. It's there for a reason. Your accusation doesn't account for dynamic evolving weather and realtime decision making.
I'm an instrument rated pilot and an advanced ground instructor under FAA and I fly IMC in bad weather as single pilot IFR around the pacific northwest and colorado.
This is the right answer.
Was this good/bad? Idk Room for improvement? Maybe? Clearer direction with the benefit of hindsight? Maybe. but the majority of the sentiment in the responses is coming from people not type rated in a 737.
Where's Nathan Fielder when you need him?
Some commenters are claiming the flight should have never taken off and that the weather situation was entirely predictable. What's your take on that?
Generally, if it's legal to take off, we're going.
(Source: am airline captain)
> That is to say, in this case, when they missed their first or second approach, they CANNOT say, "We'll use our reserve fuel and make another go at it" because that would be intentionally planning to burn your reserve.
Is that what happened? That's not in the article, what's the source?
And other comments here are saying the third attempt was in Edinburgh, so they were already trying to land anywhere possible by the third attempt.
At what point are you saying they chose to plan on using reserves when they still had any option for landing without reserves?
OP didn’t have the full picture. They’ve offered appropriate edits/updates
> you can never plan on using it
In off-roading, we have a similar rule with 4 wheel drive. You don't use it to go in, you use it to get out.
in what way do FAA rules apply to operators doing a European to UK flight in an airline that doesn't operate in the US?
Similar philosophies but with differences. e.g. FAA reserve requirements is destination + alternate + 45 mins reserve. EASA is destination + alternate + final reserve which is 30 mins holding for jets and 45 mins for pistons IIRC. But in both cases it's that idea of a destination, an alternatite, and additional. And then there's the requirements around whether you need an alternate, etc.
See my comment, https://news.ycombinator.com/item?id=45541096 [I am expert in CFR 14 Part 121, so I made reference to the regulations I'm qualified to directly speak on.]
I was wondering that too. I've taken it to mean "if this situation had happened in the Americas..." as the most generous interpretation I can make.
If you're into your reserves you should declare an emergency immediately to get priority in air traffic sequencing and control.
Pilots may be organizationally disincentivized when making this decision.
It's required when using your reserve under EASA to declare Mayday Fuel.
> Under FAA rules this was a screwup
An oversight I'm sure they can fix ;-)
FAA as a yardstick? Hm
Looks like they tried two attempts to land in Prestwick over two hours, then flew to Edinburgh and made one aborted landing, then finally went to Manchester.
What a nerve wracking experience for those pilots. I wonder if on the final attempt they knew they had to force it down no matter what.
Per the FlightRadar24 logs, it looks like only about 45min was wasted over Prestwick, not 2hrs. First approach was around 18:06, and they're breaking off to head for Edinburgh by about 18:51.
If there's considered to be a mistake here though, I'm guessing it's going to be spending too long before committing to the initial diversion.
Without knowing the weather they were seeing at the time, seems hard to say if they should have gone for a closer 2nd alternate than Manchester.
I don't think we know yet when min fuel was declared. At that point, they will be resequenced. Then we need to know when mayday fuel was declared. It sounds pretty odd, like perhaps there were multiple simultaneous situations and the crew did not have adequate information.
About 5 years ago before ATC recordings became mainstay on YouTube, there was an American pilot that declared an emergency at JFK and very firmly said "we are turning back and landing NOW. Get the aircraft OFF all runways".
He was low in fuel and also frustrated with Kennedy ATC because he declared "minimum fuel" earlier and was still getting vectored around. (I know "minimum fuel" is not an emergency and has a very precise meaning).
They must have been very close to running out. But it was a valuable lesson learned in speaking up before you get to that point.
I’m guessing that pilot had also been taught the lesson of Avianca 052, which crashed at JFK because the FO / captain did not explicitly declare a fuel emergency.
JFK ATC in particular has an enormous workload with many international flights, combined with direct, even conflictual at times, NY communication style. It puts the onus on the pilot for conveying the message to ATC, rather than ATC for extracting the message from the pilot.
You might be thinking of https://www.youtube.com/watch?v=-sQuHnrJu1I
For comparison, this is what can happen when the pilots are not that assertive https://en.wikipedia.org/wiki/Avianca_Flight_052
this was it, thanks for finding it. I didn't realize it happened 14 years ago
> But it was a valuable lesson learned in speaking up before you get to that point.
I'm not sure it was a lesson learned per-se because the captain was merely doing his job as fundamentally defined.
A captain has ultimate responsibility for the aircraft.
However there is a side question in relation to your post...
When you say "declared an emergency" in your post, the more interesting question would be whether it was actually formally declared by the captain (i.e. "MAYDAY") or whether the captain was merely "working with" ATC at a lower level, maybe "PAN" or maybe just informal "prioritised".
If the captain DID declare "MAYDAY" earlier in the timeframe then yes, Kennedy would have a lot to answer for if they were spending excessive time vectoring around.
But if the captain did not formally declare and then came back later and started bossing Kennedy around, that would be a different set of questions, focused on the captain.
The word Mayday is not required to declare an emergency. Pan pan still indicates an emergency. And neither phraseology is required as long as the intent is clear, see https://www.faa.gov/air_traffic/publications/atpubs/atc_html...
In fact, it doesn’t even need to be the pilots who declare an emergency https://hsi.arc.nasa.gov/flightcognition/Publications/non_EA...
> The word Mayday is not required to declare an emergency.
That may be so in the US.
But it is a bad habit to pick up.
Especially if you are an airline pilot and you frequently fly to destinations where English is not the first language.
Or indeed in US airspace where you frequently get international carriers flying in and out.
There is a reason why there is internationally agreed standard phraseology for radio communications.
Everyone learns MAYDAY/PAN and the associated expectations around it (e.g. radio silence etc. etc.)
Not everybody will be able to adequately follow along if you have a long drawn-out waffle discussion over the radio ... "we have a little problem" ... "do you want to declare?" ... "oh wait, standby ...." ...."oh, we're ok for now" ... "oh actually maybe this or that"... yada yada yada.
If its truly an emergency then cut the crap and use the standard phraseology and keep the communications terse.
In the US, we don't typically call Mayday/PanPan (despite it being both allowable and more correct). Pilots literally say "N777DS declaring an emergency. Engine out/Low fuel/Birdstrike". The effect is that all emergencies are Mayday.
someone further down found the incident [1] I was referring to. It was 14 years ago, not 5 as I had initially thought. Curious to hear your take on it. Pilot said "if you don't give me this runway, I'm going to declare an emergency..." which I don't think is the most helpful thing to say. But there were definitely many swiss-cheese holes lining up that day.
1. https://www.youtube.com/watch?v=-sQuHnrJu1I
Assuming it wasn't just luck, it seems impressive they managed to maximize their (landing attempts/fuel reserves) ratio like that.
It is a requirement [1] to land with 45 minutes of fuel remaining, if the pilots go under that, it is considered an incident. As soon as estimated landing fuel goes under the limit, the flight needs to declare an emergency (as was done in this case).
[1]: https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F... is the US rule, EASA has a similar rule.
Exactly. This will have a lot of consequences.
They got within a hair of crashing, there is nothing impressive about this. 30 minutes, ok, you still get written up but this is cutting it way too fine.
> this is cutting it way too fine.
Either this is true, or this is why there’s a 45 minute reserve requirement. There were three failed landing attempts in two airports prior to the successful landing, and they spent almost as much time attempting to land as the scheduled flight took.
Seems like this was exactly the scenario it was designed for?
No, this is what should never happen. I wrote fuel estimation software for cargo 747's and the one thing I would have never ever wanted to read is that an airliner of the company I worked for had landed with too little fuel.
Right but this is an emergency… they didn’t plan to run out of fuel
Clearly, that's why it makes the news.
Are there ever situations where running into the reserve would be a good trade off?
This one. The reserve is there in the same way that a crash barrier is there on the highway. You really don't ever want to use it, but when you do use it and it ends well you treat it just as seriously as though you would treat a crash.
I would imagine 6 min fuel left was designed for something extreme. Maybe involving damage to aircraft limiting where it can land etc. Or extreme weather event such had high winds affecting all airports within 500 miles.
Context: because of bad weather.
But I'm truly surprised (in a bad way) people on the ground couldn't solve the situation earlier. The plane was in an emergency situation for hours, wtf.
Also, the airport density in the UK is high, they should have been diverted since before the first attempt, as it has happened to me and thousands of flights every single day around the world.
The incident investigation will surely focus on exactly those things. But: just like shipping aviation is at the mercy of the weather and even though the rules (which are written in plenty of blood) try to anticipate all of the ways in which things go wrong there is a line beyond which you are at risk. I've had one triple go-around in my life and it soured me on flying for a long time afterwards because I have written software to compute the amount of fuel required for a flight and I know how thin the margins are once you fail that third time. I am not going to get ahead of the investigation and speculate but I can think of at least five ways in which this could have happened, and I'm mostly curious about whether the root cause is one of those five or something completely different. Note that until there is weight on the wheels you don't actually know how much fuel remains in the tanks, there always is some uncertainty, to the pilots it may well have looked as if the tanks were already empty while they were still flying the plane. Those people must have been extremely stressed out on that final attempt to land.
There must be measurements of the fuel tanks state, right?
There are but this is not as precise as you might think due to a lot of confounding factors. Even the best flow meters are only about 0.2% accurate, and I find that seriously impressive.
Armchair quarterbacking it, but it was human error. They should have diverted sooner and been more aware of the weather.
Edit: there might also be part of Ryanair culture that contributed, but that's speculation.
That's one conclusion. But don't rule out a lot of other things that may have been a factor, for instance, they may have had a batch of bad fuel, they may have had less fuel to start with than they thought they had (this happens, it shouldn't but it does happen), the fuel indicators may have been off (you only know for sure after touch down), there may have been a leak, an engine may have been burning more than it should have. There are probably many others that I can't think of of the top off my head but there are a lot of reasons why the margins are as large as they are.
Those are all possibilities, but
https://www.flightaware.com/live/flight/RYR3418/history/2025...
They had at least an extra hour of fuel, and they landed at the third airport they tried.
Yes, that's how it should be. Something went badly wrong here. The big question is what.
I read and agree with all those options being possible. Except the "they may have had a batch of bad fuel". How would that work in your thinking? I can imagine a bad batch of fuel leading to engine damage or flameout and many other things, but it is hard for me to imagine how a bad batch would lead to not enough fuel remaining in the tank.
If you have more water in the fuel than you think you do (there always is some due to condensation in the tanks) then you might be able to reach your destination but you'll be burning more 'fuel' than your original estimate would have you believe because there is less power per unit weight of (contaminated) fuel.
This is fairly common in GA and there are cases where it has happened in scheduled flights as well. That's why fuel sampling is common practice.
Interesting. That makes sense. Thank you for the explanation!
It's supposed to be an extremely low amount and the fuel pick-ups are placed such that it should never be a problem but there have been cases where water in the fuel caused problems, including at least one notorious crash where the cause was identified to be fuel contamination.
I saw this plane out my window when it was landing at Prestwick. It was dark and windy about 60mph and I said to my wife "what's that in the sky". The airport is about 5 miles away, for some reason this one caught my eye - in the hundreds/thousands of planes that go by I've never said that before, don't know if it was pointed an odd direction but it appeared stationary. We thought it was like a star, but too bright. We looked it up on flight radar to see if it was a plane and it was the one that later came out.
I know this will not be relevant to anything but I thought it was a strange coincidence then I saw it on my hn feed.
> One pilot who reviewed the log said: “Just imagine that whenever you land with less than 2T (2,000kg) of fuel left you start paying close attention to the situation. Less than 1.5T you are sweating. But (220kg) is as close to a fatal accident as possible.”
Now that is range anxiety.
> The Boeing 737-800 had just 220kg of fuel left in its tanks when it finally landed, according to a picture of what appears to be a handwritten technical log. Pilots who examined the picture said this would be enough for just five or six minutes of flying.
For reference, passenger airlines immediately declare emergency if their planned flight path would put them under 30 minutes of fuel (at least in the US). Landing with 5 minutes remaining of fuel is very atypical
220kg is about 1% of the plane's fuel capacity. They must've had a lot of faith in their fuel probes.
For anyone interested, here is the flight playback:
https://fr24.com/data/flights/fr3418#3c7f91f4
Sub required.
I can wait for the Pete the Irish Pilot’s take though.
this one is available - https://www.flightaware.com/live/flight/RYR3418/history/2025...
Is there a way to hear the pilots / ground conversing?
I think monitoring ATC comms is banned in the UK.
Certainly banned enough that you can't listen to ATC playback anywhere online. I think in practice you can use an air band radio at home (not sure how anyone would know if you were anyway).
Better links
https://avherald.com/h?article=52dfe5d7&opt=0
https://www.reddit.com/r/aviation/comments/1nzet3a/flight_a_...
Quoted:
Incident: Malta Air B738 at Prestwick, Edinburgh and Manchester on Oct 3rd 2025, landed below minimum fuel By Simon Hradecky, created Sunday, Oct 5th 2025 14:39Z, last updated Friday, Oct 10th 2025 15:02Z
A Malta Air Boeing 737-800 on behalf of Ryanair, registration 9H-QBD performing flight FR-3418 from Pisa (Italy) to Prestwick,SC (UK), was on final approach to Prestwick's runway 20 when the crew went around due to weather. The aircraft entered a hold, then attempted a second approach to runway 20 about 30 minutes after the go around, but again needed to go around. The aircraft again entered a hold, about 10 minutes after entering the hold the crew decided to divert to Edinburgh,SC (UK) where the aircraft joined the final approach to runway 24 about one hour after the first go around but again went around. The aircraft subsequently diverted to Manchester,EN (UK) where the aircraft landed on runway 23R about 110 minutes after the first go around.
On Oct 5th 2025 The Aviation Herald received information that the aircraft landed below minimum fuel with just 220kg fuel (total, 100kg in left and 120 kg in right tank) remaining.
The aircraft returned to service about 13 hours after landing.
On Oct 10th 2025 the AAIB reported the occurrence was rated a serious incident and is being investigated.
A passenger reported after the first go around at Prestwick the crew announced, they would do another attempt to land at Prestwick, then divert to Manchester. Following the second go around the crew however announced they were now diverting to Edinburgh, only after the failed approach to Edinburgh the crew diverted to Manchester.
> the Boeing 737-800 had just 220kg of fuel left in its tanks... enough for just five or six minutes of flying
Maybe I'm just unaware, but it's crazy to me that these planes burn 40 kilograms of jet fuel per minute.
I don’t think that’s so much? A car burns 1 liter to travel 15 kilometer’ish, and carries 4 people.
An airplane burns 40 liters to travel 15 kilometers too (900 kph), but carries 160 people.
That’s about 40x more than the car, so the fuel economy per passenger is about the same.
Of course jet fuel is probably a bit more polluting, but it’s still interesting how close it is.
The greenhouse effects of flying is about 3-5x the effect of just burning the fuel.
Could you explain why this is?
Water vapor in the stratosphere has a very high radiative forcing. Offset somewhat by particulates in the upper atmosphere.
Cirrus clouds and contrails have a distinct, and large, additional forcing.
What do you mean by this? What else than burning the fuel contributes to the greenhouse effect?
Building the airplanes? Servicing them? Heating the airports?
That's nebulous, are we going to claim that for all industrial processes?
In commercial aviation (passenger/cargo), typically about half the take-off weight is fuel. That's not half the payload weight (pax + cargo + fuel), it's half the takeoff weight.
For a medium-range flight (say ~2000 mi / 3200 km) each passenger incurs somewhat more than their own weight in fuel.
I don't think that's correct. The MTOW (Maximum Take-Off Weight) of an A320ceo is 78,000 kg, while the max fuel capacity is approximately 24,210 litres. Using Jet A-1's density of roughly 0.804 kg/L, that's about 19,460 kg of fuel, which represents only 25% of the take-off weight. The OEW (Operating Empty Weight) for that aircraft is approximately 42,600 kg, which means you'd need the fuel to weigh around 35,400 kg for your "half the take-off weight is fuel" claim to be true—nearly double the actual fuel capacity.
Even for a long-range aircraft like the A350-900, with an MTOW of 280,000 kg and a fuel capacity of approximately 138,000 litres (roughly 111,000 kg at 0.804 kg/L), fuel represents about 40% of the take-off weight. The OEW is approximately 155,000 kg, meaning even a completely empty plane (except for crew) loaded with maximum fuel still wouldn't reach your claimed 50% fuel fraction.
Yeah, when people say "flying has a high carbon footprint", they're not kidding. It's really quite massive.
I don't fly any more.
Want to bake your noodle?
Because the market responds to your behavior by slightly lowering the cost of flying to fill those seats, demand increases to match from slightly lower income people. Because they then organize their lives slightly more around cheap flights, it gets even harder to lower the impact of flying.
Paradoxically, rich people like us (you're a tech worker too...) flying more, because we're less sensitive to price, leave more room for pricing in carbon reduction strategies in the tickets/taxes. If you have more seats from the lower end of the market... you don't have as much flexibility in solutions.
Which is a strong argument for a carbon tax on (fossil) fuels. Indexed to consumption over greenhouse gas emissions targets.
Taxes are one way to make markets internalise externalities.
Hi, I'm the choir you're preaching to
Sing louder, damnit!!!
;-)
That might be true within a certain band, but if enough people stop flying, there's only so much elasticity there. Eventually they stop flying as many planes.
(Of course, subsidies probably throw a wrench in all of this.)
> leave more room for pricing in carbon reduction strategies in the tickets/taxes
that is politically driven and has nothing to do with whether rich or poor bums are on seats.
What makes you say that?
Clearly you have thought a lot about carbon reduction, so I have a question for you.
Is a plug in hybrid or EV less polluting if you don’t have rooftop solar?
edit: I think I know the general answer, but I’m splitting hairs comparing a replacement car for an ICE vehicle that I have.
You don't need your own rooftop solar. You can time your charges for when power is cheap (i.e. renewables are highly represented in the grid mix). In many locations you can get an electricity tariff that changes by time of day, either fixed times of day or nearly real-time to track the current wholesale price.
Here in Scotland, we have an EV electricity tariff that give us low rates between 00:30 - 05:30 while the wind turbines spin and demand is low, and our plug-in hybrid is programmed to charge during those hours. (We also run the dishwasher, washing machine, and tumble dryer on time delay during those hours as much as possible)
With nearly all of our car trips being local, the ~25 mile electric range the plug-in hybrid is rarely exceeded. We fill the petrol tank maybe once every 3 or 4 months, or when we're on a road trip.
Pure EVs are harder to justify in the UK currently unless you do basically all of your charging at home, because with 20% VAT added to the price of electricity from public chargers, and too-low fuel taxes, the per-mile cost is similar to—or sometimes more expensive than—driving on petrol. It's shockingly bad public policy.
Octopus Energy in the UK. Sometimes you can get paid to take power off the grid. Unfortunately batteries are too expensive to make really good use of it.
The EV is by far the least polluting option. In a year or two of normal driving, even on a dirty grid, you generate less pollution than if you were burning fuel in the car.
Grids are getting lower carbon intensity every year, so it just gets better after that.
It's also not clear that rooftop solar is better than anything else, the carbon involved in getting it to you, installing it, the business that does the installation… It's not very efficient.
Don't look up the carbon footprint of driving then. That is even higher in comparison to most passenger flights.
The data on https://ourworldindata.org/travel-carbon-footprint disagrees, do you have a source?
It doesn't though. The vast majority of flights are short-haul or long-haul flights and not domestic. This data uses the UK flight data so let's look that up.
Non-Domestic flight passengers: 14,124,617 [1] Domestic flight passengers: 1,455,330 [2]
So you can see that over 90% of all passengers do not fly domestically within the UK. So only the domestic flights emit more CO2 than combustion engine cars, but they are the minority. If you were to look at the US, flights that short probably play even less of a role due to longer distances between cities in the US (in comparison to the UK).
In conclusion the data you provided very much proves my point so thank you for providing the source for my statement yourself.
[1] https://www.caa.co.uk/Documents/Download/10276/b2eedadb-6813... [2] https://www.caa.co.uk/Documents/Download/10276/b2eedadb-6813...
Well, I don't drive either, except for a longer distance trip once or twice a year...
Especially crazy considering the 737 is not a particularly large commercial aircraft.
40kg/minute is around 12 gallons (47 liters) of fuel per minute. Meanwhile a 777 burns around 42 gallons (160 liters) per minute. A 747 burns 63 gallons (240 liters) per minute - more than a gallon per second!
Is that at cruising altitude?
Yes
Each of the four F1 engines on the Saturn V burned 1.8 metric tonnes of liquid oxygen and 0.8 tonnes of rocket fuel every second.
And each engine's propellant pumps required 55,000 HP to deliver that propellant.
40kg of fuel per minute is a lot but airplanes carry a lot of people.
Web searches suggest a 737-800 gets about 0.5mpg at cruise. With 189 passengers in a one-class layout that’s 95mpg per passenger. With 162 in a two-class layout that’s 81mpg per passenger.
This is better than a single person in a car but four people in a Prius gets 50mpg * 4 = 200 mpg.
This is what vexes me about the lack of emphasis on highway self-driving. Everyone's obsessed with robo taxis.
An overnight trip that's automated could go at 40 mph and get seriously good gas mileage. I mean man with four people would probably get almost 100 miles per gallon.
And this would eliminate a lot of short-range flights
It should be a lot easier to implement than having to worry about a whole class of problems that robo taxis in cities have
Sounds like a train.
The robo taxi links the last few miles to transit.
I recently travelled from my house in Seattle to my office in SF without ever getting in a car. I walked more in the airport than I did anywhere else.
Home -> Walk 11 min -> Metro Bus -> light rail -> SEA -> SF -> BART -> Walk 2 min to Hotel.
Next time I go down I’m going to take Amtrak. I couldn’t this time because it was full. In 2024 360,000 people rode that route on 730 trips for an average of about 500 people per trip. Looks like Amtrak gets between 0.6 and 2mpg. That’s 300mpg to 1000mpg per person which is better than a Prius’ 200mpg at 40mph.
Seattle to SF is 1019 miles. At 40mph that’s 25 hours, which is an hour slower than the Amtrak schedule.
Yes. Electric self driving cars are why I am not too concerned about all the tunnel and highway building. They are train tracks of the future.
Train tracks are the train tracks of the future.
Trains are far more efficient than cars, especially at scale.
Assumes everyone is in medium to high density urban areas.
I like the idea, rural life excepted, but hard to imagine sprawl will ever be replaced.
It doesn’t. Trains cover the same distances as airplanes. Take a train across Washington, or anywhere, most of the stops are small towns.
Light rail, busses, and robotaxis cover sprawl.
That is why some people avoid flying for environmental reasons. Planes use crazy amounts of fuel.
Look at it (2.5 t/h) by volume (0.82 kg/L): 3 kL/h (790 gal/h) == 50 L/m (13 gal/m) == 830 mL/s (0.9 qt/s), and then divide the total flow rate by 2 for rate per engine.
Or divide the total by the number of passengers (~189) flying to consider effective fuel economy (per passenger) or 13 kg/pax/h or 3.6 g/pax/s.
They must plan to never land with less than 30 minutes of fuel, or about 1.25 t, and I'd say they should never, ever land with less than 15 minutes in their career during a pan/mayday bingo fuel emergency.
> 40 kilograms of jet fuel per minute.
That is going to vary considerably between cruising and ascending.
Possibly related, but not definite, this apparently has happened before with Ryan Air.
https://avherald.com/h?article=454af355
https://www.independent.co.uk/travel/news-and-advice/exclusi...
These were not definitive but it did raise concerns due to the budget nature of the airline.
The latest Captains Speaking podcast has an discussion about one of the hosts being in a similar situation: https://youtu.be/5ovlZ221tDQ
Fortunately, the flight left with extra fuel, because it was cheaper to carry excess from the origin airport than to buy it at the destination airport, so reserve fuel wasn't needed, but it was close. Also, there was lots of lightning.
I absolutely love insights like this into areas of the world I have no knowledge. Makes absolute sense in the modern world but also something I'd not think about
Trucking companies started adding this to their logistics about a decade ago as well. Once they had accurate fuel price information for most of the country they started telling their drivers precisely how much fuel to onboard at each stop.
Yeah makes sense. Similar to my electric car now I think about it. Optimises charges based on capacity and price.
It reminds me of a Transavia flight from Girona to Rotterdam that had to be diverted to Amsterdam back in 2015 (1 attempt at Rotterdam, decided to divert to Amsterdam, then 2 attempts in Amsterdam).
It was a particularly stormy weekend and it turns out from the article that they had 992kg of fuel left:
https://avherald.com/h?article=489d4c3f
Massive respect for pilots and the job they do.
As a naive person, I have a simple question - why would they even fly to an airport where there's 100mph winds? Wouldn't ATC know this and tell the flight way in advance to fly to a different destination?
Because the weather is very changeable. You may get a lull in the wind for a couple of mins, enough to land.
I've been on a couple of flights like that. Once where we did two attempts and landed on the 2nd, the other where we did 3 but the had to divert. Other planes were just managing to land in the winds before and after our attempts.
The other problem is (as I found out on that flight) that mass diversions are not good. The airport I diverted to in the UK had dozens of unexpected arrivals, late at night. There wasn't the ground staff to manage this so it took forever to get people off. It then was too full to accept any more landings, so further flights had to get diverted further and further away.
So, if you did a blanket must divert you'd end up with all the diversion airports full (even to flights that could have landed at their original airport) and a much more dangerous situation as your diversions are now in different countries.
Forecasts are based on multiple weather simulation runs.
It's a often good working gamble that you will pick a short period of weather that is within your operational limits.
Commercial pilots don't have "personal limits". It's defined by their airplane and/or companies constraints.
This very recent Mentour documentary is extremely relevant, came to mind immediately. Multiple redirects due to bad weather, extreme "Get-there-itis" and eventually running out of fuel.
Great edutainment if you're feeling in the mood for that. If you're inpatient you can skip to 14 minutes, before that it's just backstory.
https://www.youtube.com/watch?v=vK_7q9tixX4
I wonder if the pilots considered Newcastle (or Teeside)? The METARs showed favourable weather conditions at Newcastle and many planes landed there that day without issue I believe. Also far closer to Edinburgh than Manchester. I wonder if they thought that Manchester being further south, had a better chance of better weather?
The only real question for the inquiry is how the decision was made to divert to Edinburgh and whether that was a reasonable decision at the time.
And then from Edinburgh to Manchester (184 miles) instead of Newcastle (91 miles) or Teeside (125 miles), both airports Ryanair operate out of.
Most of the trains north between Preston and Glasgow were being cancelled that day due to the weather. Perhaps knowing they only had one more attempt at landing safely left, Manchester further south seemed like the better bet.
I look forward to watching this one on Mentour Pilot
You'll probably have to wait a while. Petter is pretty insistent on waiting for the full incident report so that he can be completely thorough and avoid speculating.
Given it's Ryanair I doubt we will see it, still hope so (Peter works for them)
I believe he's retired
The headline is about the landing, but the issue here happened at takeoff. There were 100 mph winds at the destination and this was their 4th fallback attempt and their third airport. This flight should never have taken off, the risk of multiple diversions was easily predictable, but the flight took off headed toward an airport in dangerous conditions, got diverted to a second airport that was just as dangerous, then finally to a third where conditions were so bad other flights were being cancelled (https://uk.news.yahoo.com/storm-amy-brings-flight-chaos-2019...) and where it finally landed because it was either land at that airport or land somewhere that is not at all an airport. Once this flight was in the air, disaster was more or less inevitable and we lucked into a narrow eviting window.
This seems to be a case where the error was that the 2nd diversion was to another commercial/passenger airport. The situation after it was determined Edinburgh was a no-go was dire and making it to an airport like Manchester was a luxury they did not have safe fuel for.
> The pilots had been taking passengers from Pisa in Italy to Prestwick in Scotland on Friday evening, but wind speeds of up to 100mph meant they were unable to land.
> After three failed attempts to touch down, the pilots of Ryanair flight FR3418 issued a mayday emergency call and raced to Manchester, where the weather was calmer.
#1 - if Prestwick had wind speeds up to 100mph, then why the h*ll was the airport not closed down?
#2 - if the pilots had experienced conditions that dire during their first two landing attempts at Prestwick, then why the h*ll did they stick around for a third attempt?
EDIT: The article's a big vague, but it seems to have been 2 attempts at Prestwick, then 1 at Edinburgh, then the last-minute "oops, do I really want to die today?" decision to run to Manchester.
Looks like the third attempt was actually in Edinburgh
The third attempted landing was in their diversion airport, Edinburgh, not a third at Prestwick.
The third attempt was in Edinburgh, looks like.
This one is pretty straightforward so it doesn't need an AAIB report. Failure of pilots to brief destination weather conditions and anticipate proper bingo fuel accordingly. Storms in the area == brief max go arounds, brief alternates, and carry extra fuel. They screwed up by taking unnecessary risks of too many go arounds and barely making an alternate because they didn't play it safe by carrying additional fuel. Take these bold pilots to the chief pilot's office for an uncomfortable conversation without tasty snacks.
United Airlines Flight 173 ran out of fuel while circling Portland International Airport trying to troubleshoot a landing gear. Six more minutes of fuel could have helped the airliner to land in the Columbia river by the airport or belly land on the runway. The captain chose to keep troubleshooting and crashed just 6 miles away from the airport.
https://en.wikipedia.org/wiki/United_Airlines_Flight_173
Can anyone say whether airline pilots make each diversion decision solely based on their own information and judgment, or do they loop in the company?
Airline captain here.
We definitely involve the dispatcher in the diversion decision. Especially if it's an unplanned diversion, where the big-picture view the dispatcher has is very useful for us in our metal tube.
Sure, company dispatchers are usually part of the conversation, and in non-emergency diversions (i.e. the vast majority), they may suggest specific airports that would be more convenient for company logistics. But the final decision is always the pilots' - and once they've declared an emergency, more or less every single airfield, including military, becomes available to them.
Unless they are in an emergency and are busy with aviating, they will coordinate with their dispatcher on diverting, even if only to verify that the weather at the intended alternate is still favorable. Per the FAA regulations, the PIC and the dispatcher have joint operational control over the flight. Of course, at the end of the day, only the pilots have their hands on the controls, so they can make the plane do what they want—but from a legal standpoint, the dispatcher and pilot-in-command have equal & shared responsibility for the safe operation of the flight.
I realize this is a UK carrier and was operating in the EU/UK, but for the most part, the rest of the world uses the US legal framework for aviation as a boilerplate for their own civil code. Yes, there are some differences, but these are usually minor and more of "differences in quantity" rather than "differences in kind". [Since the airplane was invented here the US had a head start on regulating civil aviation.]
Are there any good online databases with fuel level details for individual commercial flights? I've been on a few flights that had to circle for a long time / had a number of go-round attempts, and I've never been able to find details after the fact about how close to the margins we were.
This happened in my country with I think a Vistara flight, where they had 5 minutes of fuel left.
I myself went from Bangalore to Delhi a couple of weeks back, and the poor pilots told the air hostesses at least twice or thrice to prepare for landing but the plane did not land until much much later.
Had a 1 maybe 1.5h holding pattern in Oslo once in Ryanair where they hoped they could land in extreme snow. Then diverted in the end (surprise!). Happened in 2009 though. Joked they were very desperate to land at Oslo because they cant afford to divert.
And that is how fuel reservoir requirements rise for all. Im sure, the whole airline industry is looking at the whole markets share prices going down- writing happy songs and packing gift baskets for Ryanair.
On the positive side, if they had made a crash landing with so little fuel, there would not likely have been a fiery explosion, and many more passengers would have survived than normal?
Air + fuel explodes just fine. You really don't want to crash an airliner. At landing speed the number of people dead will still be > 0 and the remainder has a good chance of being injured seriously.
For instance:
https://en.wikipedia.org/wiki/Turkish_Airlines_Flight_1951
This happened at landing speed (the airport is only a few hundred meters from the crash site) and the plane was at the end of its flight from Turkey, it did not catch fire. Still, 9 people perished and the remainder were all but one injured 11 of them seriously.
Only 7% died, pretty good for a plane of that size with a rough landing.
Dunno about "only" ... 99.99998% of flights kill 0% of their passengers. Even if "just" one passenger dies in an incident, your flight is already in the 0.00002th percentile for safety, very bad!
Yes, even though that is a harsh conclusion to make and for the families involved of course it doesn't matter at all. But as these come this was bad but still not nearly as bad as it could have been. They were about to cross one of the busiest highways in NL, another 100 meters and it would have been an entirely different story. The field they landed in is in the Haarlemmermeerpolder, so clay and it had just been plowed.
that was equipment failure crew had to fight it, not something predictable like running out of fuel
> and many more passengers would have survived than normal?
This[1] kind of crash landing is very rare (in that case there was no fire despite being immediately after take off, perhaps because of the cold). Normally an outcome like this is only reasonable to expect if you actually reach a runway despite being out of fuel. Like Gimli[2].
[1] https://en.wikipedia.org/wiki/Scandinavian_Airlines_System_F...
[2] https://en.wikipedia.org/wiki/Gimli_Glider
Username checks out. I don’t think the fire is your first concern in a plane crash.
Well there'd probably be a fire but not a sustained fire which would improve survivability.
Even fighter jets have more fuel reserves when they land. This is insane.
Looks like the emergency reserve management worked?
The Guardian can’t be trusted with their sensationalist headlines.
The flight couldn’t land in 3 other airports and eventually declared emergency.
The plane landed with approx 67 gallons of fuel. They typically land with 670 gallons.
A US gallon of Kerosene weights approx 6.5 lbs
Why such a large surplus?
Guess which airline I won't be flying with next time...
So this is about the stopping problem, but for airplane fuel, kinda?
Ryanair: Cutting cost at all cost
Yup. They also popularised excessive baggage under the seat, and I routinely used to see obvious hazards that would impede an evacuation. Staff would turn a blind eye. Probably still do
Further, with the baggage being there in easy reach under the seat, I reckon people would be more tempted to take it with them when evacuating.
That they're are a safe airline seems to be incredible luck - they have all the components for it not to be.
Each passenger will be required to bring a 5 gallon can of JET A.
Nothing beats a Jet2 holiday...
Is it like in the car where you have no fuel left but there’s a reserve of another 10 liters?
Yes and no. I had this happen recently and looked into it.
My wife has been using my car, which is a Diesel Golf with a fuel capacity of 14.5 gallons. We set off driving one Saturday to visit my parents, and I noticed the fuel gauge was below empty already. By the time I got to the gas station, I put 14.3 gallons of fuel into it. I calculated that that works out to be about a cup and a half of fuel.
So once you hit empty on my car, you definitely have a ways you can drive still. I feel comfortable driving about 30+ miles, and it's never died on me. That puts it at no more than 1 gallon of fuel left in the car based on my experience (not scientific I know, but I've owned 2 of these cars, with about 190k total driven miles). It's a lot less than 10 liters from E to Dead on the roadside.
You shouldn't tempt fate with a diesel, or any direction injection car for that matter. The high pressure pump will shred itself very quickly as the diesel is used for lubrication.
Best Practice.
probably depends between cars. on my old civic fuel light is ~5L/1.3 gallons
It's more like
* enough reserve to waste some in traffic. On top of that * enough reserve to find gas station. On top of that * enough reserve to drive to neighbouring city for gas station. On top of that * enough to cruise 30 minutes around that neighbouring city looking for other gas station in case the previous ones were closed. On top of that * enough station to run around parking lot looking for space to park
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Another metric conversion error?
Sounds like pilot error - they didn't pay the extra fee to have reserve fuel.
"Worth it" - Ryanair probably
I imagine the next step will be RyanAir asking passengers to carry fuel cans onto the plane. B*tards.
Between overworked, understaffed ATC and undertrained pilots, I'm expecting some major disasters in the coming years.
One of the problems with modern internet discourse is there is an implicit assumption that the problem of one country is automatically the problem of another country.
I think that's just Americans tbh.
Flights operate internationally?
Yes, between other countries without having to go via the US!
Internationally yes, but Ryanair don't travel transatlantic.
I've never heard of any of these problems with RyanAir. They treat you as less than cattle and generally their service is shit, but I'm not aware of RyanAir being unsafe.
Actually, in a quick check it seems the total fatality count for RyanAir is zero, with only two (on-fatal) major incidents (2008, 2021). That's seems a pretty good track record considering the amount of flights they do.
Yeah there's a lot of hatred of Ryanair given their somewhat pugnacious attitude. But as far as I know they don't mess around when it comes to safety.
> Between overworked, understaffed ATC and undertrained pilots, I'm expecting some major disasters in the coming years.
Maybe in the US, but this story is based in Europe, each country maintains a regulated standard and there are no EU wide disruptions that have ever happened to the best of my knowledge. Also Ryanair don't travel transatlantic flights.
Three weeks ago in Nice, France it was a fraction of a second away from two A320s crashing [0] and possibly hundreds of deaths, similar to Tenerife disaster [1].
Investigation is ongoing and many factors are at play (bad weather, extra work for ATC due to that, confusing lighting of runways etc) but also, from French media reports, there used to be 15 people per shift 5y ago in Nice ATC, now there are just 12, and traffic is higher.
Many people left the profession during Covid and haven't been replaced.
[0] https://avherald.com/h?article=52d656fd&opt=0
[1] https://en.wikipedia.org/wiki/Tenerife_airport_disaster
Mistakes and disasters happen, unfortunately the safety we have while flying today has been written in blood, but there is no major understaffed ATC and undertrained pilots in general as mentioned.
15 down to 12 in 5 years with more traffic is not out of the question with advancements in technology but of course, if there is a report that shows understaffing then absolutely it should be addressed straight away and it will be, by the French government.
Ryanair does use low-hour fresh-out-of-training pilots though. Certainly not the only airline that does that either.
I mean, the US also hasn't had any widespread waves of disruptions that led to incidents or flight problems. Same as the EU. American flights and airspace are usually safer too, statistically speaking.
Why? Is ATC a problem in other countries than the US? Are they also under training pilots? If anything RyanAir with its flamboyant history of cost cutting (CEO always threatening to charge for use of the onboard lavatory) seems a more likely source than the flying infrastructure itself.
Ryanair has a very good safety history, among the highest in the world.
They make outrageous claims for publicity, and their customer experience is all about hidden extras and "gotcha" pricing, but I don't think they fuck around when it comes to safety.
They know that with their reputation they would be sunk if they did have a major incident.
It's both true that Ryanair has very good safety record, and that in the past there were incidents with them landing on low fuel.
https://www.eurocockpit.eu/news/mayday-mayday-wins-over-ryan...
> In 2012 and 2013 “Brandpunt Reporter” broadcasted a two episode TV investigation in which Ryanair pilots, speaking anonymously, raised concerns about the airline’s fuel policies and company culture. The pilots revealed that the company may be exerting pressure on them to minimize the amount of fuel they take on board – a practice which limits significantly the fuel costs for the company but could jeopardise safety in certain circumstances. The direct reasons for this broadcast were 3 emergency landings of Ryanair aircraft in Valencia Spain on the 26 July 2012, within a short timeframe due to low fuel levels.
So it's sunk? They just had a major incident.
Let's wait for the investigation results before coming to that conclusion.
What indication is there that our pilots are undertrained?
I am just a PPL, and that was not an easy thing to accomplish (most pilots complete 50% more hours than required before they are able to pass that test), but my impression is that western training standards for commercial pilots are incredibly high, and the safety record seems to back that up.
Its arguably too high, constraining the supply of pilots, and the supply of well-paying jobs, resulting in things like Colgan Air Flight 3407.
In the US, I think that's probably true especially using hours as a proxy for training.
The EU has shown us that you can safely have far fewer hours.
As a pilot I do think that nothing replaces butt in seat, but I also think that 1500 hours of instructing/aerial surveying/hour building is well into the diminished marginal returns area.
Internet vibes, basically.
This had nothing to do with any of that tho.
Pilots are ultimately the ones who are responsible for when and where to land, when to divert, and how much fuel to take along.
In this case, they likely had adequate fuel for, the usual eventualities but the weather in Scotland was particularly bad that night across the whole country (source: I live near Prestwick airport).
Either Edinburgh (on the east coast) or Prestwick (on the west coast) are ok (one or the other or both) but in this case neither was suitable so the nearest was Manchester - definitely an edge-case.
I don't know how much fuel they had, or if they could've fitted any more on the plane but it was unusual circumstances.
There was a military plane right behind it with the same issue that night too.
Were these pilots undertrained?
Closely followed by the ritual lampooning of some senior middle managers who by the fish-in-barrel method were discovered to not be doing very much.
Story time, from my past.
Waiting on full flight in Europe, good airport, for take off. Pilot says over speaker : " We are delayed becuase FUEL guy got UPSET on tarmac and has QUIT. We know need someone ELSE to fill the plane with FUEL. " Said in a COMPLETELY nonchalant voice.
Immediately I get concerned, try not to think what cause a FUEL TECH to QUIT regarding THIS PLANE and fuel issue. Just close my eyes, relax.
2 minutes later pilot comes on intercom again "For some WEIRD reason, someone wants to get off the plane. Now we have to wait for ground crew to find his suitcasebecause of rules. How annoying.."
Plane waits for an hour on tarmac for BOTH passenger to get off and for FUEL to be finally "resolved".
Arrive eventually at destination.
Most of the trouble would have been avoided if the pilot had not sounded nonchalant about a "NON ISSUE about FUEL that a technician just QUIT OVER". I swear i even rememebr saying the statement with a hint of humour, like what on earth is the problem.
This is a true story, and the fact this incompetence happened to me, well I wouldnt have believed it otherwise.
I imagine everyone involved know that they are doing dangerous things, not taking a drop more fuel than is legally required for profit, knowing that none of that is going to change unless there is a major accident... They keep[1] landing these planes with X minutes of fuel left, but it doesn't do anything, until some plane falls from the sky with 0 minutes of fuel left then everyone knew all along and the rules are changed and nobody is held accountable.
[1] https://www.bbc.com/news/world-europe-19267153
lacking fuel in plane that has not started flying isn't exactly something that should stress anyone and most definitely non issue
You missed the point of the story, the issue was not lack of fuel, it was a crew member quitting because of a fuel issue, most likely a misunderstanding.
Fuel misunderstandings have resulted in numerous serious incidents, try googling it bro