It's important to note the plane is a Cozy Mk IV, which is an experimental light aircraft that is built at home out of foam and fiberglass by following instructions you get online. The design is very good, and hundreds have been flown over the last ~35 years, but Cozy pilots are the aviation equivalent of people who run Arch Linux as their daily driver; many of them are tweaking their aircraft with some frequency.
This isn't a case of an established aircraft manufacturer cutting corners on a part; it's probably some small maker who made this part out of the wrong materials. It's a little shocking that neither the maker nor the buyer of this part thought to either stick it in an oven or run it with the engine on the ground to guarantee it could hold up to the expected intake air temps. I'm glad the pilot made it out with only mild injuries.
Actually, I think all of the jet engine manufacturers these days are using 3d printers for some of their parts? Although you usually find the press releases talking about this using the term "additive manufacturing" instead. See, e.g., this press release from 2018 about a notable jet engine manufacturer using 3d printing: https://www.geaerospace.com/news/articles/manufacturing/manu...
(Although note that these are not using plastic parts, to be clear.)
Yes, implicit was that it was an uncertified part 3D-printed by "someone" who sold it at an airshow. Obviously a certified part from the manufacturer is a different story.
The 3D printing isn't the actual problem, as you note.
It's not the "3D printed" aspect of the part that's driving the failure, it's that it's made out of thermoplastic. An injection molded part in this situation[1] would likely have failed in the same way.
[1] It's not clear what the source of the heat was or where this was in the motor enclosure. But yeah, one needs to be careful with structural plastic near running engines!
Thermoplastic is the problem here. There are plenty of thermoset and other kinds of plastics that handle heat well and don’t soften with heat in normal ranges. 3d printed thermoplastics typically need to be liquid at <300 C so the glass transition usually is closer to 200 or even less. Definitely not suitable for the engine bay.
Manufacturers who use 3D printing use specialized 3D printers, not the same thing that hobbyists use.
They also handle all of the testing of parts to ensure they meet the design spec and they have the equipment to validate each printed part to ensure it doesn't have any major defects.
You can see the layer lines in the part. WTF? I don’t build aircraft parts. But I sure as hell wont use thermoplastics in this situation. I don’t even 3D print parts for mildly hot environments where failure is just annoyance.
This is an uncertified experimental aircraft. At least in the US, it is up to the operator of an experimental to ensure that parts are fit for purpose.
I've printed and used intake manifolds for (automotive) engines in the past, without issue. Obviously that's not the same stakes as an aircraft, but I don't see why it wouldn't be possible to do safely.
I’m not necessarily saying it can’t be done. But these are plastics that fail under heat. I’d test part for non critical applications and I’m just a nobody amateur.
These guys are messing with planes and don’t test enough? Is there an explanation these people aren’t just incompetent?
Not that I can think of, honestly. I'd be extremely hesitant to use a part I printed on an aircraft. If I had to, I'd make very sure to test multiple copies to destruction.
> The aircraft owner [...] understood from the vendor that it was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material, with a glass transition temperature of 105°C [...] he was satisfied the component was fit for use in this application when it was installed.
> [...] Two samples from the air induction elbow were subjected to testing, [...] The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample.
I've known 3D printing folks who run off a throwaway prototype in a cheap, easy-to-print material to check for fit before printing in more difficult, expensive materials. Easy to imagine a careless manufacturer getting the PLA prototype mixed in with the ABS production parts, and selling it by mistake.
Of course, the aviation industry usually steers clear of careless manufactures....
I don't know if it is the same in the UK as it is in the US, but the appeal of experimental aviation (every Cozy is experimental) is that there are no specs or requirements around parts like this.
If you want to slap 15 weed-wacker engines to a wing you made from styrofoam and call it an airplane, the FAA will not stop you.
I'm oversimplifying, a bit, but less than non-pilots might think.
In other words, the engine maker probably has some thoughts about how that piece should be made, but the FAA would have no problem with you installing it on an experimental.
My understanding of the UK CAA is that it isn’t as liberal as the US FAA when it comes to amateur-built experimental aircraft airworthiness. I would still be surprised if a 3d-printed intake manifold on a homebuilt passed an airworthiness inspection in the US without a number of detailed questions being answered to the satisfaction of the airworthiness representative.
But not that much better compared the better filaments out there. Fair chance it was printed out of PLA, ABS or PETG, by the shade of the part it looks like it was CF loaded filament.
A better choice would have been PEEK. But even then, I would have done a lot of on-the-ground testing before trusting my life to a part from the printer.
100% -- the original design for the Cozy is from the early 90s, before 3D printing became popular, and this part seems like a good candidate for 3D printing. It just seems like the maker chose the wrong materials and didn't test it adequately.
It's a candidate, but it is definitely not a run race, temps under the engine covers of a plane can get surprisingly high (surprising because you'd think you have plenty of airflow half a meter behind a pocket hurricane). I'm not sure if high temp filaments would be the solution here, but they'd be better candidates. It would need some very thorough testing before trusting your life (or in this case: someone else's) to that kind of solution.
Yes, that's why I listed them. And even then: none of those first three are (safely) usable for this application. PEEK or ULTEM or something better than that.
I absolutely agree. At the same time, I’m just flabbergasted that someone really thought they’d pass off PLA crap for such a purpose, it literally loses shape in sunlight. PETG isn’t going to cut it and I wouldn’t want to be on a plane with PETG in a heat-sensitive part, but that would still have been less ridiculous given that a) it’s significantly better than PLA in this regard, and b) unlike PEI and PEEK, it can be printed with ease on just about any FDM.
Whoever sold that part deserves to be sued. I'm not from the 'sue happy' department but this was extremely irresponsible and unless the swap for PLA was accidental (which can easily be proven, they must have sold more than just one of these). At a minimum they should recall each and every one of these they have made and on top of that they should review all of the other parts that person has made for similar issues.
The analogy they weren't making: "This is life critical, just like Arch Linux"
The analogy they were making: "This is a commonly home-built and heavily customized hacker aircraft, just like Arch Linux is a commonly home-built and heavily customized hacker Linux distro"
Two things can be analogous in one aspect while being disanalogous in another aspect. That doesn't make the analogy invalid.
General aviation (and especially experimental light aircraft) is not a particularly safe hobby. This pilot literally put his life in the hands of a 3D printed part someone sold him at an airshow. Pilots can and do "brick" their planes as a result of "innovative" approaches to repairs, upgrades, and maintenance. Luckily, much of the time these errors are caught before the plane gets off the ground.
Guy, the person who bet his life on a part with questionable quality is a moron. People who choose an OS are not betting their life on their OS booting up. Do you not grasp the difference in stakes?
I don't think anyone is struggling with grasping the difference in stakes. The stakes are different, the size and shape are different, there are a lot of things different.
You don't make analogies out of things that are the same, that's one of the hallmarks of an analogy.
mort96 explained my analogy better than I could. Obviously your OS and your plane are not equally risky choices. Regardless, there exist communities of people who like to heavily customize either of those things.
This is the mechanical equivalent of vibe coding. 3D printing itself isn't exactly to blame but the negligence of the company that created and sold this part and omitted it's use from an inspection.
Just because a part has the shape of an engineered part does not make it compatible, strong, safe, and fit for purpose. This part could have likely been fine if it used a different material such as Ultem.
In what way is this like vibe-coding -- or do you just mean both are bad?
According to the report:
> The aircraft owner who installed the modified fuel system stated that the 3D-printed induction elbow was purchased in the USA at an airshow, and he understood from the vendor that it was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material, with a glass transition temperature3 of 105°C.
I think by vibe coding he means taking these things at face value instead of rigorously looking if they are up to the standard. When coding you would rigorously look if the code is good / produces any bugs. With vibe coding, you give a prompt and just accept the output, which might be full of errors and blow up (or melt). The analogy is that, yes you can print airplane parts, but they were sloppy and just accepted them at face value instead of rigorously looking if they are up to the required (bug free) standard, ie they wont melt.
The problem is we have different terms that all mean doing something without real risk management or analysis in software. Both "cowboy coding" and "vibe coding" mean the same thing, if you remove the agent doing the production.
And since vibe coding is so recently coined, I think a lot of people take it to specifically mean "LLM" and not some generalized "any third-party agent".
Then, a vibe coded engine part sounds like it would need a generative AI producing the CAD file that is then printed. And it might have some bizarre topology like a Klein bottle or some fever dream.
>I think by vibe coding he means taking these things at face value instead of rigorously looking if they are up to the standard.
Yeah, exactly -- which is why it's a stupid phrase for what happened here.
Not every negligence is somehow equatable to an AI pitfall, it's just on parents' mind so it's the only metaphor that gets applied.
A poorly fit hammer in a world of nails.
I say this as an engineer/proprietor with years of additive manufacturing experience, it's insulting. A poorly chosen and wrongly used process conveys nothing about the underlying fundamentals of the process itself -- it conveys everything about the engineer and the business processes that birthed the problem.
Similarly if I came across a poorly vibe-coded project I wouldn't blame Anthropic/oAI directly -- I would blame the programmer who decided to release such garbage made with such powerful tools..
tl;dr : it's not vibe-coding itself that makes vibe-coding a poor fit to rocket science and brain surgery -- it's the braindead engineer that pushes the code to the THERAC-25 without reading.
I think the idea was that 3D printing made doing a thing accessible, previously required solid fundamental knowledge (and very expensive kit). Now you can just take some specs off the internet and press go.
The comparison does not seem as absurd to me as it does to you. vOv
The lesson here is that one should never attempt analogies on HN, because people can't just relax and try to see the point of the analogy. They are compelled to fixate on the fact that an analogy is different from the thing it is being compared to.
I feel like Hacker News commenters love to make analogies more than average people in your average space, though. You can't come across a biology/health topic on here without someone chiming in with "it's like if X was code and it had this bug" or "it's like this body part is the Y of the computer."
Analogies can be useful sometimes, but people also shouldn't feel like they need to see everything through the lens of their primary domain, because it usually results in losing nuances.
3D printing is to mechanical engineering what vibe coding is to computer science.
With the rise of accessible 3D printers that can print engineering materials, there are a lot of people who try to create functional parts without any engineering background. Loading conditions, material properties, failure modes, and fatigue cycling are all important but invisible engineering steps that must be taken for a part to function safely.
As a consumer with a 3D printer, none of this is apparent when you look at a static, non-moving part. Even when you do start to learn more technical details like glass transition temperature, non-isotropic strength, and material creep, it's still not enough to cover everything you need to consider.
Much of this is also taught experimentally, not analytically - everyone will tell you "increasing walls increases strength more than increasing infill", but very few can actually point to the area moment of inertia equation that explains why.
3D printing has been an incredible boon for increasing accessibility for making parts in small businesses, but it has also allowed for big mistakes to be made by small players. My interpretation is the airshow vendor is probably one of these "small businesses".
You don't need to be able to mathematically jerk the equation off to understand why increasing material at the perimeter adds more strength than the center (within reason and in typical cases) or why you probably shouldn't use something that melts around 200deg in an engine bay.
Everything you need to consider is really not that much when it comes to most typical consumer 3d printing projects. Mostly because they are usually about stuff like "fixing a broken tashcan". The engineers who made that bullshit plastic part that broke after a year probably knew all about area moment of inertia, but that doesn't mean I need to to print a replacement part that lasts longer - or not, in which case I'll just iterate on my process.
I really don't get the dismissiveness, and frankly, I've never experienced that from engineers in my life. They just seem delighted when someone, kid or adult, tinkes with additive manufacturing.
Hmm, I suppose the analogy could be interpreted as dismissive, which is not my intent.
I think both vibe coding and 3D printing are wonderful things. Lowering the barrier to entry and increasing technology accessibility allows those without formal training to create incredibly capable things that were previously difficult or not possible to do.
What I meant to specifically highlight is the 3D printing of functional parts that have some level of impact on safety, things that can lead to significant property damage, harm, or loss of life. Common examples include 3D printed car parts (so many) and load bearing components in all sorts of applications (bike mounts, TV mounts, brackets, I even saw a ceiling mounted pull-up bar once).
This isn't to say it can't or shouldn't be done. What I'm saying is that both on the digital side (files for personal use) and the production/sale side (selling finished parts), there is no guarantee of engineering due diligence. 3D printers enable low volume small businesses to exist, but it also means that, purposefully or not, their size means they can go quite a while without running into safety regulations and standards meant to keep people safe.
I call bullshit. 3d-printing is just a manufacturing method. Basic woodworking is much cheaper and more accessible than 3d-printing, do you call it vibe-coding?
If you carve a wooden part with "the right shape" for an engineering application that the part lacks the physical properties that allow it to perform under load stress ... then yes, that's vibe carving.
Looks good - falls apart in practice, and a junior can't tell the difference as they "look the same" to the inexperienced eye.
From practical experience, you cannot just replace a tyre on a car with any old bit of wood - you really need to use hard wearing mulga (or equivilant) as an emergency skid. (And replace that as soon as possible)
What you're describing is more like someone who doesn't know computer science principles hacking on code, manually. Part of the definition of "vibe coding" is that AI agents (of questionable quality) did the actual work.
This whole thread is a stretch, IMO. But, I like this phrase.
As a fabricator (large wood CNC, laser cutting and engraving, 3D Printing, UV Printing, Welding). I put engineering into a whole different job scope. I can make whatever you tell me really well, not vibe-carving.
I don't necessarily write the specs or "engineer" anything. I'm just saying, don't blame the medium, 3D printing. The fact is a fabricator is not necessarily an engineer, regardless of the medium.
Don't get me wrong, wood is great, I've made a lot of things and replacement parts from appropriate woods.
Using scrublands wood (slow growing tough long grain mulga) as a skid when a rubber tyre destroys itself is an old old hack passed on by my father (he's still kicking about despite being born in the early 1930s).
Point being, I don't blame processes (3D printing, etc) for part failure, that comes down to whether the shape and material are fit for purpose, whether material grain structure can be aligned for sufficient strength if required, whether expansion coefficients match to avoid stress under thermal changes, etc.
Engineering manufacturing can sometimes be suprisingly holistic in the sense that every small things matter including the order in which steps are performed (hysteresis) .. there's more t things than meet the eye.
In the report they tested samples of the part and found that they actually had glass transition temperatures of 52.8°C, and 54.0°C... so sounds like the owner fell victim to false advertising.
This is an experimental homebuilt aircraft, so the regulations on manufacture and replacement parts are much less stringent than commercially sold aircraft.
Also, the part it was replacing was a fiberglass part in an epoxy resin, with a glass transition temperature of 84°C. So the 105°C glass transition temperature of the replacement part should have been better than the original.
However, the original had an aluminum tube supporting the inlet, which provided extra structural support beyond fiberglass epoxy resin. And upon testing, the actual glass transition temperature of the 3D printed part was 52.8°C for one sample and 54.0°C for another, so much lower than expected.
Now, because the regulations are much less strict for experimental homebuilt aircraft, there may not be the traceability to figure out where in the chain the issue came up. Was it a bad batch of filament? Did the person making the part use the wrong kind of filament? Who should have tested the glass transition temperature of a coupon of the same material as the replacement part? Did the 3d printed material glass transition temperature change over time, possibly due to something like fuel or exhaust fumes?
The recommendation from this report is to disallow 3d printed replacements for this part, but it should be possible to do with the right material and proper testing and analysis (as well as leaving in the aluminum tube for additional support), as this is an air intake and it should be possible to find a 3d printed material that can withstand the kind of temperatures an air intake is subjected to, given that the original part is a fiberglass with epoxy resin.
The report further states that the part included in the original design (part of the kit) was made of a carbon fiber composite where the epoxy had a listed glass transition temperature of 84⁰C. If there is an element to be critical of along these lines it's that the part as originally designed is supposed to include an aluminum tube at one end that may stiffen the part - the report makes no conclusions whether it truly would have, but notes that the actual glass transition temperature was found to be much lower than listed, and lower than that of the epoxy used in the original design.
The person who coined the term vibe coding is now doing a soylent-like [1] experiment where he only will read content that has been regurgitated by an AI [2], so yes I think it's a fair characterization of "vibe coding".
The vendor selling the 3D-printed part at an airshow probably didn't think: "I'll deceive pilots." They likely thought: "I can 3D-print this part to spec, it looks right, it fits, and pilots will be happy." The capability to create professional-looking outputs outpaced the discipline required to validate them.
Same with vibe coding: the LLM isn't lying. It's producing code that passes basic inspection. But both technologies have collapsed the cost of creating something that looks production-ready while preserving all the ways something can fail in actual use.
Before 3D printing and LLMs, there were natural friction points that forced validation:
• Manufacturing a metal aircraft part required industrial equipment, precision tooling, material selection expertise. The process itself embedded quality gates.
• Writing professional software required years of training, code review practices, deployment infrastructure. The difficulty forced rigor.
Now, both technologies let anyone produce outputs that visually and functionally resemble professionally engineered work without any of the underlying validation:
• A 3D printer can output a part that looks dimensionally correct, has proper tolerances, fits perfectly—but the material choice was never stress-tested against thermal cycling.
• An LLM can generate code that compiles, runs, produces correct output for test cases—but has no error handling, SQL injection vulnerabilities, or memory leaks that only appear at scale.
This is a relatively new failure mode where professional appearance becomes decoupled from professional rigor. And customers can't easily tell the difference until something breaks.
I think a more useful definition of vibe coding is "something you can do when it really doesn't matter". Which requires a hell of a lot of judgement to know when it doesn't.
Installing life-critical parts of shoddy engineering into a vital system of your airplane is a good example of when things do matter.
> The Cozy Mark IV is a 4-seat, single engine, homebuilt light aircraft [...] The aircraft is built from plans using basic raw materials. It is not a kit aircraft
You could scarcely get more DIY than this aircraft. Home-built, and not even from a kit - the builder gets to lay up every part in glass fibre themselves, by hand. And this guy had been flying it for 26 years.
It sounds like the guy was sold a part 3D printed in the wrong plastic, and it melted. He thought it was ABS, but it melted at the temperatures PLA melts at. If your engine air inlet is made of plastic that melts at 54°C (130°F) you're going to have a bad time.
It's easy to imagine how a chaotic 3D printing business might have run off a test part in a cheaper black plastic, then a confused worker could have stored the test part in with the other 'identical' parts in a different black plastic.
The 'serious' aerospace industry avoids this with lots of paperwork and procedure; when an airline maintains an airbus plane, they use only airbus-approved parts from airbus-approved sources with a paperwork trail confirming they were inspected for being-the-right-material using an approved procedure. I don't know if the home-built aircraft community would be eager to adopt those practices, though.
> That should be so obvious that I wonder if it was DIY by the pilot.
I don't know how the regulatory environment is in the UK for experimental craft (this is considered to be "experimental" category in the US and Canada), but yes, the idea behind an experimental is that everything is DIY.
I have an experimental, and I can do close to anything I want. What I can't do is complain when my plane crashes because I installed a part that isn't fit for duty. I, as the owner and operator, am the one that signs off on the airworthiness of the plane.
E.G. If I install a Cessna part on my plane, and that is the cause of a crash, that is my fault from the point of view of the FAA.
There may be legal considerations outside of airworthiness and flight rules, but as far as the FAA is concerned (or would be if this had happened in the US), the manufacturer of a part is off the hook once the thing is installed on an experimental.
>> This part could have likely been fine if it used a different material such as Ultem.
Maybe, but FDM printed parts are still much weaker than molded parts. We tried printing some coolant pump housings once during development. They worked fine until the pressure went up and then layers separated and someone got to clean the lab. At least an air intake is gonna have negative pressure which might help hold the layers together.
but it didn't fail because of stress. It failed exactly because it was made from wrong material. If the exact same part was injection molded from the same material it would melt too
It’s also a validation failure as well, because somebody assumed that the 3d-printed part could work as intended without validating it under various use-cases and situations.
Looks like they would like to make the early flight mistakes themselves instead of following air worthiness guidelines.
Taken at face value, this is engineering negligence. I've done industrial design with plastics and 3D printed parts. Regardless of the forming techniques, with plastics you still need to consider properties like minimum melting temperatures, tensile stress, and so forth. Then you must test that rigorously. This is all standard procedure. That information is in the data sheet for the material.
I did a quick search and found that many plastics are governed by ISO 11357 test standard [1]. Some of the plastics I have worked with used this standard.
Also, strictly as a combo 3D-printing and engine enthusiast: Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine. This is spectacularly poor judgement on the part of the owner.
Then you are not up to speed with what the 3D printing world has to offer. You can 3D print full metal stress free parts and chances are very high that if you have flown in an airplane in the last five years that some of the parts of that plane (and I'm not talking about trim here) were made using additive processes.
Rocket engines can be 3D printed, in fact there are some engines that can only be made using that kind of technique due to internal structures.
Yes, real parts CAN be 3D printed and even used successfully.
The printing is the easy part.
The extensive testing and validation that it will actually work as intended and in your situation is the hard part.
Skip that hard part, especially for anything that flies, and you are risking lives, both those in the air and on the ground.
Seriously, just because the specs on the label say X and other docs say the running temperature is Y, does NOT mean it will work. Take the measurements in your situation, test the thing extensively on the ground.
Then, maybe, it'll be worth flying. Or, you'll be there after some hours of testing saying: "good thing I didn't try to fly with this", and still have a usable aircraft.
Depends. Some older or rare cars have no source for parts. 3D printing has been a boon to keeping them operating. However you absolutely have to use appropriate materials to avoid problems or failures, and know where it isn't feasible.
FWIW, I wouldn't hesitate to install a 3D printed air-filter housing in my car, if I had printed it myself out of e.g. PAHT or sourced it from a trusty vendor. It's not rocket science, just engineering.
Well, there are more and less important parts of the car. I wouldn't bat an eye for 3d printed dash parts or the extreme example, a cup holder, but on flip side anywhere where there is heat is potentially bad for anything 3d printed with heat that's not metal or some hard to print high temp stuff, and anywhere where mechanical robustness = safety is spot where you want something very well tested, not "I printed it and it looks light".
> Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine.
The fabrication technology doesn't matter. The qualification process, on the other hand ...
This is the primary reason why I never got a pilot's license. I suspect I would spend far too much time making sure the maintenance was up to standard and far too little actually enjoying flying.
You should be thrilled to know that any plane you will learn to fly in typically has full maintenance records for the entire life of the plane, including who did the work, their FAA certificate number, and all of the paperwork for any parts that were involved in the repair.
The shortcut is to ask the mechanic to come for a test flight after repairs. The place I learned to fly was owned by a mechanic, and the daughter ran the flight school. Given that the daughter might be test flying the mechanic's work, I trusted him to keep his planes in good shape.
> The fabrication technology doesn't matter. The qualification process, on the other hand ...
Well, yes, but... In this case the fabrication technology and the lack of qualification process likely go hand in hand. They wouldn't have a qualification process unless they were manufacturing enough of these that plastic 3d printing wouldn't be cost effective. The shortcut is the point.
Yes but are they printed with PLA or PETG, or even ABS? Or are they using material designed exactly for their use case, and tested thoroughly before being certified for flight?
Or do they get their parts from some vendor at a swap meet who spends most of his time fiddling with his Ender 3?
Neither of those is suitable for this application. Ultem or PEEK. Anything else would be a very bad idea, and even for those two you would want to do a lot of testing.
I'm sure it's fine you do it properly ([1] for example). The issue here was the utter lack of engineering, not the specific manufacturing technique (although those do seem to be highly correlated, due to low-end 3D printing having become very cheap and easy).
The part was claimed to be ABS-CF. UK AAIB tested the part and found it to have a Tg of approximately 53C. The Tg of ABS is far higher, around 100C. I suspect that the part may have been accidentally printed with PLA-CF (which has a Tg of approximately 55C.)
The original part was fiberglass/epoxy with the epoxy having a Tg of 84C.
HDT does, kind of, but that’s already covered by the load being defined for the various conditions. HDT is always defined at a specific load so it also does not change with load (since load is fixed).
Isn't Tg a poorly defined metric? It seems like thermoplastics will lose their strength as temperature goes up and there's no abrupt transition where there's a near step-change in behavior
I doubt there is any form of ABS filament with such a low glass transition temperature. As the original poster said, it was probably PLA.
I find it odd that the report didn't name the manufacturer of the part, and that the part was not listed on the LAA modification form. There can't be many people selling such parts at airshows, so you'd think the investigators would have been able to find out who made it.
Now I wonder if the previous owner (who installed the new fuel system) printed the part himself, then claimed he bought it overseas to avoid blame.
Maybe "load" includes the heat that comes from the changes forces from the vibrations? But even then, that would be additional heat sources, rather than a change in the temperature where it happens.
Polycarbonate shows little change vs pressure [1]:
Glass-liquid transition temperature, which is approximately where plastics and other materials change from hard and relatively brittle into flexible and rubbery.
As the other comments here noted, it doesn’t exactly mean that the material is safe to use for a rigid part below that temperature, and the transition extends over a range in temperatures, but it does give you a rough idea about the behavior of a material at various temperatures.
I showed this to a pilot friend of mine out of curiosity, he noted that this type of aircraft is usually kit built / home built. So the fact a part of it was 3D printed was not a total shock.
Except that it wasn't, it's just what "the owner understood from the vendor". But the AAIB measured the Tg of material samples to be about 53 °C, which is very low and strongly suggests it being PLA or PLA-CF.
I wonder if he was erroneously sold a demonstrator part?
Looks like either CF loaded ABS or PLA, the difference is super hard to tell visually but given that they determined that particular temp my bet would be PLA because even PETG would be higher.
And yet "Two samples from the air induction elbow were subjected to testing, using a heat-flux differential scanning calorimeter, to determine their glass transition temperature. The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample."
I wonder if just including the aluminum tube that was effectively acting as a heat break would have been enough...
Really it seems like a problem of not understanding the environment, and testing (with margins) your replacement in it... 3D printing seems nearly entirely unrelated apart from enabling people to make parts.
An injection molded part, for a close more traditional analogue, would presumably have failed the same way here.
Also the glass transition temperature reported in the report is suspiciously low for ABS and the only source on the material is the owner saying the person they bought it from said... I wonder if it was just outright made out of the wrong material by accident.
The difference is, injection molds are expensive. And the type of people who can afford them tend to cover their ass better - or do slightly less insanely dumb things.
3D printing (especially using filament) allows idiots to enter entirely new areas of endeavor.
I agree, but I note that the 3d printing people are making progress in making really cheap injection molds. I wouldn't count on the difference in cost remaining prohibitive enough that only reasonably serious people can afford it for much longer.
Edit: And I hope the lesson that the safety critical people take away from this is "actual engineering work is needed for airplane components" and not "3d printed parts are scary" because sooner or later they'll run into the same issue with parts made in other ways
Just imagine, chainsaws, lathes, welders and now <gasp> 3D printers. What will they come up with next to give these irresponsible dilettantes a way to create their own objects... what we need here is some proper gatekeeping. Maybe a certificate or two, and some very expensive software that proves that you're a company that is serious.
And while we're at it we should forbid home brew software too.
Also it's insane that they used a bolted joint with plastics on a critical place, the plastic will creep under the clamp load and will lose clamp force.
Well, no, it's in the UK. It also has a gross weight of around 2000lbs, so it's probably not subject to any of the relaxed regulations anywhere, although I don't know how the UK homebuilt rules work these days.
Aside from the failure it looks like it wasn't the best print to start with. Lots of rashing from support and curling at the edges. You can see on the flats where the support was and the outer curve of the elbow looks like it likely wasn't airtight.
Appears to me to be printed with the inlet facing upwards.
Better support planning, settings and possibly orientation may have helped.
Other commenters are saying it was likely PLA-CF, which I totally agree with based on the testing, but I can't help but think there is no possible way the person printing this item did not know that.
I doubt the print would have come off as good as it did when using ABS-CF settings on PLA-CF.
I've almost made that exact same mistake (but not on a critical part). I had a bunch of identical rolls with CF loaded filament of different base materials and just looking at the filament you really couldn't tell.
"Two samples from the air induction elbow were subjected to testing, using a heat-flux
differential scanning calorimeter, to determine their glass transition temperature. The
measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the
second sample"
Yeah, they might have used ABS-CF filament, but unless they got it from a good brand that uses good resin and proper printing parameters, the actual Tg will be lower, plus the stress from the vibration/load could have made the part fail if it was not for the heat later in flight.
Polymaker's ABS is dubious too because it is blended with PETG. They are coming out with a Pro version that has a higher Tg and requires way higher chamber temps to print properly.
> An alternative construction method for the air induction elbow, shown in the Cozy Mk IV
plans, is a lamination of four layers of bi-directional glassfibre cloth with epoxy resin. The
epoxy resin specified for the laminate has a glass transition temperature of 84°C, after the
finished part has been post-cured. The aircraft owner stated that as the glass transition
temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied
the component was fit for use in this application when it was installed
What a misunderstanding -- glass transition temperature means different things for thermoplastics (i.e. anything that comes out of an FDM printer like the CF-ABS in question) and for thermosetting resins like epoxy that actually undergo molecular cross-linking during the curing phase. Thermoplastics will get soft and can deform without limit, while thermosets get rubbery but still more or less hold their formed shape.
I think an extended quote shows that this was a really bad call:
“ The aircraft owner stated that as the glass transition
temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied
the component was fit for use in this application when it was installed.
A review of the design of the laminated induction elbow in the Cozy Mk IV plans showed
that it featured a section of thin-walled aluminium tube at the inlet end of the elbow, where
the air filter is attached. The aluminium tube provides a degree of temperature-insensitive
structural support for the inlet end of the elbow. The 3D-printed induction elbow on G-BYLZ
did not include a similar section of aluminium tube at the inlet end.
Tests and research
Two samples from the air induction elbow were subjected to testing, using a heat-flux
differential scanning calorimeter, to determine their glass transition temperature. The
measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the
second sample.“
> The epoxy resin specified for the laminate has a glass transition temperature of 84°C
This seems very low for the kinds of epoxy I've used. I wonder if the manufacturer specs are highly conservative? Or maybe the material has a shortened lifespan with even moderate temperatures?
I was thinking about the ABS in the article and wondering if I would have made the same mistake. Close to every car manufactured today has plastic intakes, usually bolted right on top of the engine. The incoming air should help keep it cool, especially on aircraft. Maybe it was the radiant heat from a nearby cylinder that melted it?
There are some incredibly low Tg epoxies out there, such as West Systems 105 where "TG onset" is 54°C and the heat deflection temperature is even lower.
The aircraft owner who installed the modified fuel system stated that the 3D-printed induction
elbow was purchased in the USA at an airshow, and he understood from the vendor that it
was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material,
with a glass transition temperature3
of 105°C.
An alternative construction method for the air induction elbow, shown in the Cozy Mk IV
plans, is a lamination of four layers of bi-directional glassfibre cloth with epoxy resin. The
epoxy resin specified for the laminate has a glass transition temperature of 84°C, after the
finished part has been post-cured. The aircraft owner stated that as the glass transition
temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied
the component was fit for use in this application when it was installed.
A review of the design of the laminated induction elbow in the Cozy Mk IV plans showed
that it featured a section of thin-walled aluminium tube at the inlet end of the elbow, where
the air filter is attached. The aluminium tube provides a degree of temperature-insensitive
structural support for the inlet end of the elbow. The 3D-printed induction elbow on G-BYLZ
did not include a similar section of aluminium tube at the inlet end.
It was an intake manifold, so it's continuously under suction. At the temperatures in an engine bay the plastic probably gradually creeped to a point where the restriction increased the suction and suddenly it collapses completely.
I wonder who installed it. Was the pilot home 3D printing mods for their plane? And is that even allowed? Super concerning if there was a company behind the installation.
I'd think any semi competent engineer would know better.
Edit: from the report - "A modification application was made to the LAA in 2019, by
the aircraft owner2
, to replace the engine’s throttle body fuel injector with a mechanical fuel
injection system. This system consisted of a fuel controller, high-pressure engine-driven
fuel pump, electric auxiliary fuel pump, fuel flow transducer and associated fuel hoses,
filters and fittings. Following flight testing, the modified fuel system was approved by the
LAA in 2022. The modified fuel injection system had accumulated 37 hours in service when
the accident occurred."
So the pilot himself and the LAA were incompetent. LAA is an association for amateur pilots though so I'm not sure what level of rigour they "approve" things with.
Nearly anything is allowed for experimental amateur-built aircraft like the one in this incident. Unapproved modifications to certified aircraft are forbidden in most parts of the world.
The LAA classified the proposed modification pf the overall fuel system as minor based on the owner’s description of it, and approved it on that basis. But the owner lied and did not disclose the fact that the induction elbow was modified at all or that it was 3D printed. The report does not discuss any required inspection by a person authorized by the LAA prior to returning the aircraft to service. So it seems like the LAA modification process is a trust-don’t-verify policy.
I'm massively paranoid that some cable clips I printed that will sit on a circuit board will perish in the heat. Meanwhile, some idiot couldn't care less about thermal stability for flight hardware!
The person that installed should have thought more carefully about it. But the person that printed it and sold it should face some legal repercussions. Totally irresponsible what they did.
Belite, a company that folded (and just renamed themselves) after a certain number of crashes of their experimental ultralights, sold my dad a plane where the AOA sensor was malfunctioning, the propeller hit the ground if there was someone in the plane, and one wing side was longer than the other. By a visible amount. My dad broke a set of propellers and they sent him a new set with 3" cut off each blade. i have those in my shed.
I'm no aerospace engineer or anything, but that plane shouldn't have been able to stay in the air.
and, lo, it didn't, the motorcycle engine used as the prime mover sputtered out at 200' AGL and since it's not a glider (and i don't even think it can glide), it crashed straight into the ground.
Fly an ultralight if you want, just be aware that people will think very poorly of you.
At a glance, that looks like worse than merely the negligence of using a new technology.
The whole point of 3D printing is that the material is moldable when hot but rigid when it cools. And people really should be aware that engines get hot.
>The whole point of 3D printing is that the material is moldable when hot but rigid when it cools.
Which means what exactly? Aluminum will go soft under high temperatures as well, yet this part would not have failed if it was made out of aluminum.
The failure is not the material, the failure is someone neglecting the operating conditions or material properties when choosing materials.
This exact part could have also been milled out of some plastic and would have failed the same way. The method to produce that part is only relevant in so far it is open to more people.
Looks like the part was advertised as ABS-CF, but may have actually been PLA-CF, which makes a big difference.
There are plenty of even higher temperature materials that can be 3d-printed. PAHT-CF is fine at fairly high temperatures (the nozzle temperature needs to be over 260C), and SLS printers can print things like aluminum.
A thermoplastic in an engine cowling is insane. It’s crazy that this was being sold the supplier should have known better, as should the buyer. 3D printing can be used to make a fiberglass or carbon fiber mold which is already a lot of the work of making the part.
It would be interesting to know what filament was used, in theory some high temp filament could be suitable but I would be nervous putting those on a car let alone a plane.
The actual report includes the important details, ABS-CF which they thought was safe because they underestimated the glass transition temperature of epoxy fiberglass.
I just watched a fun video of a guy bringing a 1978 Datsun 280Z up to date. He kept the existing engine but upgraded it with modern electronic ignition and computer control. As part of all that, he fabricated various parts in plastic by 3D printing, but then had the final versions made elsewhere in metal -- some by a CNC shop you send CAD files to, and one by a manual machinist in Switzerland with his own Youtube channel. The latter has to be case hardened, which the machinist did.
The 3D printed plastic parts were very useful to prove out the parts' shapes.
>The Light Aircraft Association (LAA) said it now intends to take safety actions in response to the accident, including a "LAA Alert" regarding the use of 3D-printed parts that will be sent to inspectors.
Does this mean that anybody using any 3d printed part in an aircraft will be subjected to this scrutiny? If I use the proper materials with a suitable printer (eg, printing PEEK with a properly specced printer), how much convincing will it take to get these governing bodies off my back?
so, if you were thinking "who would use a 3D-printed part", remember that it may otherwise also have been made with some liquid material, but using a mold, and perhaps two parts using a mold that are joined with re-heating etc. - and now it no longer sounds so outlandish.
Hardware engineering is hard. Especially for any safety critical component.
In this case engineering was done by someone, who either did not understand the material he was working with, or the operating conditions in which that part was deployed.
Obviously no testing or any kind of proper engineering was done to create requirements validate them and verify them.
Being able to design a 3D model and print it does not mean you are done with engineering. It is just one step in a very long chain, which is needed to produce devices which stand up to their use.
And this is why (at least for the US) aviation parts have such an onerous paperwork overhead, why a seemingly cheap part like a $.50 bolt balloons to much greater. Granted this aircraft was a UK-equivalent to "experimental" in the US, where you can pretty much do anything to it, I'm of the opinion that doesn't excuse maintenance and adding fly-by-night parts that borders on negligence. Stick to a minimum standard, if not just out of shame of something that could happen.
Hah! I've actually 3D printed a part of an intake before. Just as a prototype, to allow me to get a Keihin carb on a motorcycle that had a CV carb.
Printed it on an SLA machine though! I was concerned enough about chemical attack even then, even though it was a temporary part. Never really thought about doing it in filament.
correction to the title: the plane crashed because the owner is a moron, not because he bought a 3d printed part but because he failed to ensure his provider is trustworthy and instead used a fly-by-night nobody to fit a machine that can kill him at any moment.
Why is the 3d-printed part highlighted; upon first reading this looks like the part softened; it didn't separate on FDM boundaries. Wouldn't a similar thing have happened if it were formed in a different way, but of the same materials?
They included everything but the 3D printed material. If it was PLA, no surprise (and no excuse). Even ABS might not stand up to the temperatures at that location. I hate it when a news report tells you everything except details that might make a difference going forward.
> The aircraft owner who installed the modified fuel system stated that the 3D-printed induction elbow was purchased in the USA at an airshow, and he understood from the vendor that it was printed from CF-ABS
This occured in the UK, so not really relevant to the FAA.
In the US though, yes, the FAA would not have a problem with this. This plane would be registered as experimental, meaning you can install unapproved parts. It does have to be inspected, but that can be done by the builder (not the designer, just the guy who built that particular example), or an airplane mechanic.
I know quite a few experimentals with 3d printed parts (including my own). I don't know any where they are installed in a place where failure would result in a crash. Typically I see them used as convenience stuff, in my case I am using a 3d printed catch to hold my upward opening door while I load the plane. If it breaks in flight, I wouldn't even know. If it breaks on the ground, the door will close.
Flea markets at US airshows are not under FAA jurisdiction.
I have attended said airshow for decades and occasionally buy stuff in the flea market myself. Old used scrapyard parts, next to some inventor’s homemade jet engine, next to tons of raw materials of unknown provenance, next to ginsu knives and miracle frying pans. Here’s what it looks like on video. Wow, I missed those hand grenades for only $10 each, what a bargain.
I hope 3-D printing becomes obsolete when robots can achieve the same efficiency with using the standard construction materials. That should take away all benefits of 3-D printing over regular builds.
You don’t need a robot, especially in the colloquial sense meaning humanoid. Better additive manufacturing techniques than desktop FDM printers exist, and CNCs can turn these parts out from much better materials all day.
3D printing isn’t entirely about automation, it’s also a way to get shapes that are impossible to manufacture traditionally. Modern rocket engines almost all use 3D printing because the shapes are so highly optimized.
It's important to note the plane is a Cozy Mk IV, which is an experimental light aircraft that is built at home out of foam and fiberglass by following instructions you get online. The design is very good, and hundreds have been flown over the last ~35 years, but Cozy pilots are the aviation equivalent of people who run Arch Linux as their daily driver; many of them are tweaking their aircraft with some frequency.
This isn't a case of an established aircraft manufacturer cutting corners on a part; it's probably some small maker who made this part out of the wrong materials. It's a little shocking that neither the maker nor the buyer of this part thought to either stick it in an oven or run it with the engine on the ground to guarantee it could hold up to the expected intake air temps. I'm glad the pilot made it out with only mild injuries.
edit: here's a fun video from a Cozy pilot in case you're curious about the plane and the people who fly them: https://www.youtube.com/watch?v=Ipqmb09wbSQ
I think this needs to be added to the urban dictionary "Cozy pilots are the aviation equivalent of people who run Arch Linux as their daily driver"
Figured it was experimental; no A&P who cared about his future would install a 3D printed part on a certified aircraft.
Actually, I think all of the jet engine manufacturers these days are using 3d printers for some of their parts? Although you usually find the press releases talking about this using the term "additive manufacturing" instead. See, e.g., this press release from 2018 about a notable jet engine manufacturer using 3d printing: https://www.geaerospace.com/news/articles/manufacturing/manu...
(Although note that these are not using plastic parts, to be clear.)
Yes, implicit was that it was an uncertified part 3D-printed by "someone" who sold it at an airshow. Obviously a certified part from the manufacturer is a different story.
The 3D printing isn't the actual problem, as you note.
It's not the "3D printed" aspect of the part that's driving the failure, it's that it's made out of thermoplastic. An injection molded part in this situation[1] would likely have failed in the same way.
[1] It's not clear what the source of the heat was or where this was in the motor enclosure. But yeah, one needs to be careful with structural plastic near running engines!
Thermoplastic is the problem here. There are plenty of thermoset and other kinds of plastics that handle heat well and don’t soften with heat in normal ranges. 3d printed thermoplastics typically need to be liquid at <300 C so the glass transition usually is closer to 200 or even less. Definitely not suitable for the engine bay.
Manufacturers who use 3D printing use specialized 3D printers, not the same thing that hobbyists use.
They also handle all of the testing of parts to ensure they meet the design spec and they have the equipment to validate each printed part to ensure it doesn't have any major defects.
You can see the layer lines in the part. WTF? I don’t build aircraft parts. But I sure as hell wont use thermoplastics in this situation. I don’t even 3D print parts for mildly hot environments where failure is just annoyance.
Whoever built this should be charged.
> Whoever built this should be charged.
This is an uncertified experimental aircraft. At least in the US, it is up to the operator of an experimental to ensure that parts are fit for purpose.
I've printed and used intake manifolds for (automotive) engines in the past, without issue. Obviously that's not the same stakes as an aircraft, but I don't see why it wouldn't be possible to do safely.
I’m not necessarily saying it can’t be done. But these are plastics that fail under heat. I’d test part for non critical applications and I’m just a nobody amateur.
These guys are messing with planes and don’t test enough? Is there an explanation these people aren’t just incompetent?
Not that I can think of, honestly. I'd be extremely hesitant to use a part I printed on an aircraft. If I had to, I'd make very sure to test multiple copies to destruction.
> But these are plastics that fail under heat.
All materials ultimately succomb when exposed long enough at some high enough temperature.
What is the temperature range to match here?
I think spacex uses it too, that's probably key to their engine becoming smaller and smaller over time.
Getting it certified for flight is insanely difficult because one of the challenges of AM parts reproducibility.
Loads of commercial aircraft and jet engine parts are manufactured using additive manufacturing, or ”3D printing”
Yes… but more often something like laser-sintered metal printing, which is not going to melt when hot.
Yep, and it works even in the SpaceX Raptor engine.
A 3d printed Inconel part would be fine. 3d printed plastic is something else entirely...
Do we know whether the part was made out of spec, or whether the spec specified inappropriate materials?
It sounds like it was something like PLA when it was supposed to be ABS.
According to https://assets.publishing.service.gov.uk/media/69297a4e345e3...
> The aircraft owner [...] understood from the vendor that it was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material, with a glass transition temperature of 105°C [...] he was satisfied the component was fit for use in this application when it was installed.
> [...] Two samples from the air induction elbow were subjected to testing, [...] The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample.
I've known 3D printing folks who run off a throwaway prototype in a cheap, easy-to-print material to check for fit before printing in more difficult, expensive materials. Easy to imagine a careless manufacturer getting the PLA prototype mixed in with the ABS production parts, and selling it by mistake.
Of course, the aviation industry usually steers clear of careless manufactures....
That's... absurd. ABS is a terrible choice for anything in an engine bay - ABS breaks down over time when in contact with oils.
I've used PA6-CF for similar purposes in the past. Obviously not for aircraft, though.
Even in ABS I would not use something 3D printed on a consumer machine as a critical part of an airplane.
I don't know if it is the same in the UK as it is in the US, but the appeal of experimental aviation (every Cozy is experimental) is that there are no specs or requirements around parts like this.
If you want to slap 15 weed-wacker engines to a wing you made from styrofoam and call it an airplane, the FAA will not stop you.
I'm oversimplifying, a bit, but less than non-pilots might think.
In other words, the engine maker probably has some thoughts about how that piece should be made, but the FAA would have no problem with you installing it on an experimental.
My understanding of the UK CAA is that it isn’t as liberal as the US FAA when it comes to amateur-built experimental aircraft airworthiness. I would still be surprised if a 3d-printed intake manifold on a homebuilt passed an airworthiness inspection in the US without a number of detailed questions being answered to the satisfaction of the airworthiness representative.
The spec is fiberglass, which has better thermal resistance.
But not that much better compared the better filaments out there. Fair chance it was printed out of PLA, ABS or PETG, by the shade of the part it looks like it was CF loaded filament.
A better choice would have been PEEK. But even then, I would have done a lot of on-the-ground testing before trusting my life to a part from the printer.
100% -- the original design for the Cozy is from the early 90s, before 3D printing became popular, and this part seems like a good candidate for 3D printing. It just seems like the maker chose the wrong materials and didn't test it adequately.
It's a candidate, but it is definitely not a run race, temps under the engine covers of a plane can get surprisingly high (surprising because you'd think you have plenty of airflow half a meter behind a pocket hurricane). I'm not sure if high temp filaments would be the solution here, but they'd be better candidates. It would need some very thorough testing before trusting your life (or in this case: someone else's) to that kind of solution.
My guess, given the sheen that looks like CF would be PA-CF, which is the most appropriate and common filament with CF.
And PA-CF is usually pretty good with temps, I have used it for parts on engines before with good results, but not in safety critical scenarios.
There’s a massive difference between the thermal properties of the materials you listed.
Yes, that's why I listed them. And even then: none of those first three are (safely) usable for this application. PEEK or ULTEM or something better than that.
I absolutely agree. At the same time, I’m just flabbergasted that someone really thought they’d pass off PLA crap for such a purpose, it literally loses shape in sunlight. PETG isn’t going to cut it and I wouldn’t want to be on a plane with PETG in a heat-sensitive part, but that would still have been less ridiculous given that a) it’s significantly better than PLA in this regard, and b) unlike PEI and PEEK, it can be printed with ease on just about any FDM.
Whoever sold that part deserves to be sued. I'm not from the 'sue happy' department but this was extremely irresponsible and unless the swap for PLA was accidental (which can easily be proven, they must have sold more than just one of these). At a minimum they should recall each and every one of these they have made and on top of that they should review all of the other parts that person has made for similar issues.
[flagged]
Please don't post shallow dismissals on HN. We're aiming for a higher standard of discussion here. https://news.ycombinator.com/newsguidelines.html
The analogy they weren't making: "This is life critical, just like Arch Linux"
The analogy they were making: "This is a commonly home-built and heavily customized hacker aircraft, just like Arch Linux is a commonly home-built and heavily customized hacker Linux distro"
Two things can be analogous in one aspect while being disanalogous in another aspect. That doesn't make the analogy invalid.
General aviation (and especially experimental light aircraft) is not a particularly safe hobby. This pilot literally put his life in the hands of a 3D printed part someone sold him at an airshow. Pilots can and do "brick" their planes as a result of "innovative" approaches to repairs, upgrades, and maintenance. Luckily, much of the time these errors are caught before the plane gets off the ground.
Guy, the person who bet his life on a part with questionable quality is a moron. People who choose an OS are not betting their life on their OS booting up. Do you not grasp the difference in stakes?
I don't think anyone is struggling with grasping the difference in stakes. The stakes are different, the size and shape are different, there are a lot of things different.
You don't make analogies out of things that are the same, that's one of the hallmarks of an analogy.
mort96 explained my analogy better than I could. Obviously your OS and your plane are not equally risky choices. Regardless, there exist communities of people who like to heavily customize either of those things.
Clearly you have a boring life. Dial it up a bit!
This is the mechanical equivalent of vibe coding. 3D printing itself isn't exactly to blame but the negligence of the company that created and sold this part and omitted it's use from an inspection.
Just because a part has the shape of an engineered part does not make it compatible, strong, safe, and fit for purpose. This part could have likely been fine if it used a different material such as Ultem.
In what way is this like vibe-coding -- or do you just mean both are bad?
According to the report:
> The aircraft owner who installed the modified fuel system stated that the 3D-printed induction elbow was purchased in the USA at an airshow, and he understood from the vendor that it was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material, with a glass transition temperature3 of 105°C.
https://assets.publishing.service.gov.uk/media/69297a4e345e3...
Isn't this simply a part that shouldn't have been allowed to be sold based on it being both faulty and also misleading?
I think by vibe coding he means taking these things at face value instead of rigorously looking if they are up to the standard. When coding you would rigorously look if the code is good / produces any bugs. With vibe coding, you give a prompt and just accept the output, which might be full of errors and blow up (or melt). The analogy is that, yes you can print airplane parts, but they were sloppy and just accepted them at face value instead of rigorously looking if they are up to the required (bug free) standard, ie they wont melt.
This is more like adding a third party dependency to your project without vetting it.
The original vibe coding.
The problem is we have different terms that all mean doing something without real risk management or analysis in software. Both "cowboy coding" and "vibe coding" mean the same thing, if you remove the agent doing the production.
And since vibe coding is so recently coined, I think a lot of people take it to specifically mean "LLM" and not some generalized "any third-party agent".
Then, a vibe coded engine part sounds like it would need a generative AI producing the CAD file that is then printed. And it might have some bizarre topology like a Klein bottle or some fever dream.
>I think by vibe coding he means taking these things at face value instead of rigorously looking if they are up to the standard.
Yeah, exactly -- which is why it's a stupid phrase for what happened here.
Not every negligence is somehow equatable to an AI pitfall, it's just on parents' mind so it's the only metaphor that gets applied.
A poorly fit hammer in a world of nails.
I say this as an engineer/proprietor with years of additive manufacturing experience, it's insulting. A poorly chosen and wrongly used process conveys nothing about the underlying fundamentals of the process itself -- it conveys everything about the engineer and the business processes that birthed the problem.
Similarly if I came across a poorly vibe-coded project I wouldn't blame Anthropic/oAI directly -- I would blame the programmer who decided to release such garbage made with such powerful tools..
tl;dr : it's not vibe-coding itself that makes vibe-coding a poor fit to rocket science and brain surgery -- it's the braindead engineer that pushes the code to the THERAC-25 without reading.
I think the idea was that 3D printing made doing a thing accessible, previously required solid fundamental knowledge (and very expensive kit). Now you can just take some specs off the internet and press go.
The comparison does not seem as absurd to me as it does to you. vOv
The lesson here is that one should never attempt analogies on HN, because people can't just relax and try to see the point of the analogy. They are compelled to fixate on the fact that an analogy is different from the thing it is being compared to.
I see multiple examples of it in this thread.
I feel like Hacker News commenters love to make analogies more than average people in your average space, though. You can't come across a biology/health topic on here without someone chiming in with "it's like if X was code and it had this bug" or "it's like this body part is the Y of the computer."
Analogies can be useful sometimes, but people also shouldn't feel like they need to see everything through the lens of their primary domain, because it usually results in losing nuances.
On the other hand, if you are communicating with a bunch of people who share that primary domain, it can be a useful way of making a point.
(unless that primary domain tends to attract a lot of people who tend to the hyper-literal /s)
3D printing is to mechanical engineering what vibe coding is to computer science.
With the rise of accessible 3D printers that can print engineering materials, there are a lot of people who try to create functional parts without any engineering background. Loading conditions, material properties, failure modes, and fatigue cycling are all important but invisible engineering steps that must be taken for a part to function safely.
As a consumer with a 3D printer, none of this is apparent when you look at a static, non-moving part. Even when you do start to learn more technical details like glass transition temperature, non-isotropic strength, and material creep, it's still not enough to cover everything you need to consider.
Much of this is also taught experimentally, not analytically - everyone will tell you "increasing walls increases strength more than increasing infill", but very few can actually point to the area moment of inertia equation that explains why.
3D printing has been an incredible boon for increasing accessibility for making parts in small businesses, but it has also allowed for big mistakes to be made by small players. My interpretation is the airshow vendor is probably one of these "small businesses".
You don't need to be able to mathematically jerk the equation off to understand why increasing material at the perimeter adds more strength than the center (within reason and in typical cases) or why you probably shouldn't use something that melts around 200deg in an engine bay.
Hmm, apparently it would have been useful..
Ehh.
Everything you need to consider is really not that much when it comes to most typical consumer 3d printing projects. Mostly because they are usually about stuff like "fixing a broken tashcan". The engineers who made that bullshit plastic part that broke after a year probably knew all about area moment of inertia, but that doesn't mean I need to to print a replacement part that lasts longer - or not, in which case I'll just iterate on my process.
I really don't get the dismissiveness, and frankly, I've never experienced that from engineers in my life. They just seem delighted when someone, kid or adult, tinkes with additive manufacturing.
Hmm, I suppose the analogy could be interpreted as dismissive, which is not my intent.
I think both vibe coding and 3D printing are wonderful things. Lowering the barrier to entry and increasing technology accessibility allows those without formal training to create incredibly capable things that were previously difficult or not possible to do.
What I meant to specifically highlight is the 3D printing of functional parts that have some level of impact on safety, things that can lead to significant property damage, harm, or loss of life. Common examples include 3D printed car parts (so many) and load bearing components in all sorts of applications (bike mounts, TV mounts, brackets, I even saw a ceiling mounted pull-up bar once).
This isn't to say it can't or shouldn't be done. What I'm saying is that both on the digital side (files for personal use) and the production/sale side (selling finished parts), there is no guarantee of engineering due diligence. 3D printers enable low volume small businesses to exist, but it also means that, purposefully or not, their size means they can go quite a while without running into safety regulations and standards meant to keep people safe.
I call bullshit. 3d-printing is just a manufacturing method. Basic woodworking is much cheaper and more accessible than 3d-printing, do you call it vibe-coding?
If you carve a wooden part with "the right shape" for an engineering application that the part lacks the physical properties that allow it to perform under load stress ... then yes, that's vibe carving.
Looks good - falls apart in practice, and a junior can't tell the difference as they "look the same" to the inexperienced eye.
From practical experience, you cannot just replace a tyre on a car with any old bit of wood - you really need to use hard wearing mulga (or equivilant) as an emergency skid. (And replace that as soon as possible)
What you're describing is more like someone who doesn't know computer science principles hacking on code, manually. Part of the definition of "vibe coding" is that AI agents (of questionable quality) did the actual work.
> then yes, that's vibe-carving.
This whole thread is a stretch, IMO. But, I like this phrase.
As a fabricator (large wood CNC, laser cutting and engraving, 3D Printing, UV Printing, Welding). I put engineering into a whole different job scope. I can make whatever you tell me really well, not vibe-carving.
I don't necessarily write the specs or "engineer" anything. I'm just saying, don't blame the medium, 3D printing. The fact is a fabricator is not necessarily an engineer, regardless of the medium.
Don't get me wrong, wood is great, I've made a lot of things and replacement parts from appropriate woods.
Using scrublands wood (slow growing tough long grain mulga) as a skid when a rubber tyre destroys itself is an old old hack passed on by my father (he's still kicking about despite being born in the early 1930s).
In the early 1980s I used to enjoy hanging out with Chris Brady and helped out making jigs to assemble snare drums: https://www.youtube.com/watch?v=jdBHtUN5gAE
His jarrah, wandoo, and sheoak snares are still loved: https://www.youtube.com/watch?v=tKmDuu5Iba4
Point being, I don't blame processes (3D printing, etc) for part failure, that comes down to whether the shape and material are fit for purpose, whether material grain structure can be aligned for sufficient strength if required, whether expansion coefficients match to avoid stress under thermal changes, etc.
Engineering manufacturing can sometimes be suprisingly holistic in the sense that every small things matter including the order in which steps are performed (hysteresis) .. there's more t things than meet the eye.
In the report they tested samples of the part and found that they actually had glass transition temperatures of 52.8°C, and 54.0°C... so sounds like the owner fell victim to false advertising.
That’s low for ABS, that’s more like PLA. If it’s ABS then perhaps there are additives to make it easy to print.
And in fact the owner was not the person who installed the part!
The implication was that the part took shortcuts and made something that only looked good on the surface. But couldn't stand up to deeper scrutiny.
This is an experimental homebuilt aircraft, so the regulations on manufacture and replacement parts are much less stringent than commercially sold aircraft.
Also, the part it was replacing was a fiberglass part in an epoxy resin, with a glass transition temperature of 84°C. So the 105°C glass transition temperature of the replacement part should have been better than the original.
However, the original had an aluminum tube supporting the inlet, which provided extra structural support beyond fiberglass epoxy resin. And upon testing, the actual glass transition temperature of the 3D printed part was 52.8°C for one sample and 54.0°C for another, so much lower than expected.
Now, because the regulations are much less strict for experimental homebuilt aircraft, there may not be the traceability to figure out where in the chain the issue came up. Was it a bad batch of filament? Did the person making the part use the wrong kind of filament? Who should have tested the glass transition temperature of a coupon of the same material as the replacement part? Did the 3d printed material glass transition temperature change over time, possibly due to something like fuel or exhaust fumes?
The recommendation from this report is to disallow 3d printed replacements for this part, but it should be possible to do with the right material and proper testing and analysis (as well as leaving in the aluminum tube for additional support), as this is an air intake and it should be possible to find a 3d printed material that can withstand the kind of temperatures an air intake is subjected to, given that the original part is a fiberglass with epoxy resin.
Well how confident would you be that this part isn't exposed to temperatures above that glass transition temperature? It is installed near the engine.
The report further states that the part included in the original design (part of the kit) was made of a carbon fiber composite where the epoxy had a listed glass transition temperature of 84⁰C. If there is an element to be critical of along these lines it's that the part as originally designed is supposed to include an aluminum tube at one end that may stiffen the part - the report makes no conclusions whether it truly would have, but notes that the actual glass transition temperature was found to be much lower than listed, and lower than that of the epoxy used in the original design.
Installed _on_ an engine that operates at 200ºC!
In the sense that production costs have undercut evaluation costs permitting a cadre of un(der)-qualified entrants to the space.
Not a new story in the progression of human endeavors; see the printing press, perspective painting, digital photography, residential construction.
The person who coined the term vibe coding is now doing a soylent-like [1] experiment where he only will read content that has been regurgitated by an AI [2], so yes I think it's a fair characterization of "vibe coding".
1: https://nymag.com/intelligencer/2014/10/soylent-creator-hack...
2: https://x.com/karpathy/status/1990577951671509438
He is gonna get slopabetes!
Experimental Aircraft are less licensed than non-experimental, so this is more of a YOLO pilot.
I mean it in a very particular way.
The vendor selling the 3D-printed part at an airshow probably didn't think: "I'll deceive pilots." They likely thought: "I can 3D-print this part to spec, it looks right, it fits, and pilots will be happy." The capability to create professional-looking outputs outpaced the discipline required to validate them.
Same with vibe coding: the LLM isn't lying. It's producing code that passes basic inspection. But both technologies have collapsed the cost of creating something that looks production-ready while preserving all the ways something can fail in actual use.
Before 3D printing and LLMs, there were natural friction points that forced validation:
• Manufacturing a metal aircraft part required industrial equipment, precision tooling, material selection expertise. The process itself embedded quality gates.
• Writing professional software required years of training, code review practices, deployment infrastructure. The difficulty forced rigor.
Now, both technologies let anyone produce outputs that visually and functionally resemble professionally engineered work without any of the underlying validation:
• A 3D printer can output a part that looks dimensionally correct, has proper tolerances, fits perfectly—but the material choice was never stress-tested against thermal cycling.
• An LLM can generate code that compiles, runs, produces correct output for test cases—but has no error handling, SQL injection vulnerabilities, or memory leaks that only appear at scale.
This is a relatively new failure mode where professional appearance becomes decoupled from professional rigor. And customers can't easily tell the difference until something breaks.
If vibe coding is shipping code that you don't understand and can't ensure it's safety,
And if this part was simply 3d scanned and printed in whatever material seemed strongest,
Then it could be an apt analogy
[dead]
I think a more useful definition of vibe coding is "something you can do when it really doesn't matter". Which requires a hell of a lot of judgement to know when it doesn't.
Installing life-critical parts of shoddy engineering into a vital system of your airplane is a good example of when things do matter.
> blame ... the negligence of the company that created and sold this part
That should be so obvious that I wonder if it was DIY by the pilot.
https://en.wikipedia.org/wiki/Cozy_MK_IV
> The Cozy Mark IV is a 4-seat, single engine, homebuilt light aircraft [...] The aircraft is built from plans using basic raw materials. It is not a kit aircraft
You could scarcely get more DIY than this aircraft. Home-built, and not even from a kit - the builder gets to lay up every part in glass fibre themselves, by hand. And this guy had been flying it for 26 years.
It sounds like the guy was sold a part 3D printed in the wrong plastic, and it melted. He thought it was ABS, but it melted at the temperatures PLA melts at. If your engine air inlet is made of plastic that melts at 54°C (130°F) you're going to have a bad time.
It's easy to imagine how a chaotic 3D printing business might have run off a test part in a cheaper black plastic, then a confused worker could have stored the test part in with the other 'identical' parts in a different black plastic.
The 'serious' aerospace industry avoids this with lots of paperwork and procedure; when an airline maintains an airbus plane, they use only airbus-approved parts from airbus-approved sources with a paperwork trail confirming they were inspected for being-the-right-material using an approved procedure. I don't know if the home-built aircraft community would be eager to adopt those practices, though.
> The Cozy Mk IV light aircraft was destroyed after its plastic air induction elbow, bought at an air show in North America, collapsed.
> That should be so obvious that I wonder if it was DIY by the pilot.
I don't know how the regulatory environment is in the UK for experimental craft (this is considered to be "experimental" category in the US and Canada), but yes, the idea behind an experimental is that everything is DIY.
I have an experimental, and I can do close to anything I want. What I can't do is complain when my plane crashes because I installed a part that isn't fit for duty. I, as the owner and operator, am the one that signs off on the airworthiness of the plane.
E.G. If I install a Cessna part on my plane, and that is the cause of a crash, that is my fault from the point of view of the FAA.
There may be legal considerations outside of airworthiness and flight rules, but as far as the FAA is concerned (or would be if this had happened in the US), the manufacturer of a part is off the hook once the thing is installed on an experimental.
>> This part could have likely been fine if it used a different material such as Ultem.
Maybe, but FDM printed parts are still much weaker than molded parts. We tried printing some coolant pump housings once during development. They worked fine until the pressure went up and then layers separated and someone got to clean the lab. At least an air intake is gonna have negative pressure which might help hold the layers together.
but it didn't fail because of stress. It failed exactly because it was made from wrong material. If the exact same part was injection molded from the same material it would melt too
It’s also a validation failure as well, because somebody assumed that the 3d-printed part could work as intended without validating it under various use-cases and situations.
Looks like they would like to make the early flight mistakes themselves instead of following air worthiness guidelines.
Vibe coding can make code that is suitable for production. 3d printed plastic can not be a substitute for a fiberglass-metal part.
It absolutely can. Not all 3D printing is kids' toys.
In the end it depends on the application. Vibe coded flight management systems, anyone?
Taken at face value, this is engineering negligence. I've done industrial design with plastics and 3D printed parts. Regardless of the forming techniques, with plastics you still need to consider properties like minimum melting temperatures, tensile stress, and so forth. Then you must test that rigorously. This is all standard procedure. That information is in the data sheet for the material.
I did a quick search and found that many plastics are governed by ISO 11357 test standard [1]. Some of the plastics I have worked with used this standard.
A spec sheet for that material is here [2].
[1]: https://www.iso.org/standard/83904.html
[2]: https://um-support-files.ultimaker.com/materials/1.75mm/tds/...
Also, strictly as a combo 3D-printing and engine enthusiast: Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine. This is spectacularly poor judgement on the part of the owner.
Then you are not up to speed with what the 3D printing world has to offer. You can 3D print full metal stress free parts and chances are very high that if you have flown in an airplane in the last five years that some of the parts of that plane (and I'm not talking about trim here) were made using additive processes.
Rocket engines can be 3D printed, in fact there are some engines that can only be made using that kind of technique due to internal structures.
Yes, real parts CAN be 3D printed and even used successfully.
The printing is the easy part.
The extensive testing and validation that it will actually work as intended and in your situation is the hard part.
Skip that hard part, especially for anything that flies, and you are risking lives, both those in the air and on the ground.
Seriously, just because the specs on the label say X and other docs say the running temperature is Y, does NOT mean it will work. Take the measurements in your situation, test the thing extensively on the ground.
Then, maybe, it'll be worth flying. Or, you'll be there after some hours of testing saying: "good thing I didn't try to fly with this", and still have a usable aircraft.
Edit: missing words, clarity.
Indeed, I think I already covered that in an older comment and didn't want to repeat the same info: https://news.ycombinator.com/item?id=46159905
Depends. Some older or rare cars have no source for parts. 3D printing has been a boon to keeping them operating. However you absolutely have to use appropriate materials to avoid problems or failures, and know where it isn't feasible.
FWIW, I wouldn't hesitate to install a 3D printed air-filter housing in my car, if I had printed it myself out of e.g. PAHT or sourced it from a trusty vendor. It's not rocket science, just engineering.
Well, there are more and less important parts of the car. I wouldn't bat an eye for 3d printed dash parts or the extreme example, a cup holder, but on flip side anywhere where there is heat is potentially bad for anything 3d printed with heat that's not metal or some hard to print high temp stuff, and anywhere where mechanical robustness = safety is spot where you want something very well tested, not "I printed it and it looks light".
> Never with a GUN to my head would I install 3D printed parts in a CAR engine, let alone in an aircraft engine.
The fabrication technology doesn't matter. The qualification process, on the other hand ...
This is the primary reason why I never got a pilot's license. I suspect I would spend far too much time making sure the maintenance was up to standard and far too little actually enjoying flying.
You should be thrilled to know that any plane you will learn to fly in typically has full maintenance records for the entire life of the plane, including who did the work, their FAA certificate number, and all of the paperwork for any parts that were involved in the repair.
The shortcut is to ask the mechanic to come for a test flight after repairs. The place I learned to fly was owned by a mechanic, and the daughter ran the flight school. Given that the daughter might be test flying the mechanic's work, I trusted him to keep his planes in good shape.
> The fabrication technology doesn't matter. The qualification process, on the other hand ...
Well, yes, but... In this case the fabrication technology and the lack of qualification process likely go hand in hand. They wouldn't have a qualification process unless they were manufacturing enough of these that plastic 3d printing wouldn't be cost effective. The shortcut is the point.
I wouldn’t be that absolute, but not until Boeing and Airbus use them in their aircraft on a regular basis.
Yes but are they printed with PLA or PETG, or even ABS? Or are they using material designed exactly for their use case, and tested thoroughly before being certified for flight?
Or do they get their parts from some vendor at a swap meet who spends most of his time fiddling with his Ender 3?
Neither of those is suitable for this application. Ultem or PEEK. Anything else would be a very bad idea, and even for those two you would want to do a lot of testing.
That was my point. They used the wrong filament. And there isn't really a right one for the cowl of a single engine aircraft
I'm sure it's fine you do it properly ([1] for example). The issue here was the utter lack of engineering, not the specific manufacturing technique (although those do seem to be highly correlated, due to low-end 3D printing having become very cheap and easy).
[1] https://www.youtube.com/watch?v=rV74KhPNg1w
The part was claimed to be ABS-CF. UK AAIB tested the part and found it to have a Tg of approximately 53C. The Tg of ABS is far higher, around 100C. I suspect that the part may have been accidentally printed with PLA-CF (which has a Tg of approximately 55C.)
The original part was fiberglass/epoxy with the epoxy having a Tg of 84C.
Plastics under load have a lower Tg.
Tg does not change with load.
HDT does, kind of, but that’s already covered by the load being defined for the various conditions. HDT is always defined at a specific load so it also does not change with load (since load is fixed).
Isn't Tg a poorly defined metric? It seems like thermoplastics will lose their strength as temperature goes up and there's no abrupt transition where there's a near step-change in behavior
It kind of is, a better metric is HDT (Heat Deflection Temperature), and it is based on curve usually load over temp.
And a datasheet for a (not necessarily the same) CF-ABS filament claims a HDT at 1.82 MPa of 93C: https://um-support-files.ultimaker.com/materials/1.75mm/tds/...
Something funny is going on with this material given the report is saying they measured a glass transition temperature of ~50C.
I doubt there is any form of ABS filament with such a low glass transition temperature. As the original poster said, it was probably PLA.
I find it odd that the report didn't name the manufacturer of the part, and that the part was not listed on the LAA modification form. There can't be many people selling such parts at airshows, so you'd think the investigators would have been able to find out who made it.
Now I wonder if the previous owner (who installed the new fuel system) printed the part himself, then claimed he bought it overseas to avoid blame.
Tg changes? Or do you mean they deflect sooner under more load?
Maybe "load" includes the heat that comes from the changes forces from the vibrations? But even then, that would be additional heat sources, rather than a change in the temperature where it happens.
Polycarbonate shows little change vs pressure [1]:
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6403934/
What's Tg?
Glass-liquid transition temperature, which is approximately where plastics and other materials change from hard and relatively brittle into flexible and rubbery.
As the other comments here noted, it doesn’t exactly mean that the material is safe to use for a rigid part below that temperature, and the transition extends over a range in temperatures, but it does give you a rough idea about the behavior of a material at various temperatures.
Glass transition temperature.
https://en.wikipedia.org/wiki/Glass_transition
Glass transition temperature I think
Sounds plausible but I guess it's something that they would've confirmed, had it been true
Or it was ABS-CF but they forgot to dry the filament /s
I showed this to a pilot friend of mine out of curiosity, he noted that this type of aircraft is usually kit built / home built. So the fact a part of it was 3D printed was not a total shock.
Edit:
https://en.wikipedia.org/wiki/Rutan_VariEze
https://en.wikipedia.org/wiki/Burt_Rutan
Actual report: https://aviation-safety.net/wikibase/487013
Material was CF-ABS
Except that it wasn't, it's just what "the owner understood from the vendor". But the AAIB measured the Tg of material samples to be about 53 °C, which is very low and strongly suggests it being PLA or PLA-CF.
I wonder if he was erroneously sold a demonstrator part?
Looks like either CF loaded ABS or PLA, the difference is super hard to tell visually but given that they determined that particular temp my bet would be PLA because even PETG would be higher.
>> Material was CF-ABS
With a glass transition temp of 105C.
And yet "Two samples from the air induction elbow were subjected to testing, using a heat-flux differential scanning calorimeter, to determine their glass transition temperature. The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample."
Which is not coincidentally roughly the Tg of PLA.
I wonder if just including the aluminum tube that was effectively acting as a heat break would have been enough...
Really it seems like a problem of not understanding the environment, and testing (with margins) your replacement in it... 3D printing seems nearly entirely unrelated apart from enabling people to make parts.
An injection molded part, for a close more traditional analogue, would presumably have failed the same way here.
Also the glass transition temperature reported in the report is suspiciously low for ABS and the only source on the material is the owner saying the person they bought it from said... I wonder if it was just outright made out of the wrong material by accident.
The difference is, injection molds are expensive. And the type of people who can afford them tend to cover their ass better - or do slightly less insanely dumb things.
3D printing (especially using filament) allows idiots to enter entirely new areas of endeavor.
I agree, but I note that the 3d printing people are making progress in making really cheap injection molds. I wouldn't count on the difference in cost remaining prohibitive enough that only reasonably serious people can afford it for much longer.
Edit: And I hope the lesson that the safety critical people take away from this is "actual engineering work is needed for airplane components" and not "3d printed parts are scary" because sooner or later they'll run into the same issue with parts made in other ways
> 3D printing (especially using filament) allows idiots to enter entirely new areas of endeavor.
That's true for any tool.
And when someone makes a new affordable tool that opens up making new types of things…. What happens?
Stuff gets made.
Just imagine, chainsaws, lathes, welders and now <gasp> 3D printers. What will they come up with next to give these irresponsible dilettantes a way to create their own objects... what we need here is some proper gatekeeping. Maybe a certificate or two, and some very expensive software that proves that you're a company that is serious.
And while we're at it we should forbid home brew software too.
Sounds like you’re the one who isn’t getting the point.
Personally, I think 3D printed drop in auto sears are pretty awesome.
But it changes the game, and the laws don’t know what to do on that front.
I also bet I own more chainsaws than you do.
Is this a Part 103 Ultralight?
Also it's insane that they used a bolted joint with plastics on a critical place, the plastic will creep under the clamp load and will lose clamp force.
> Is this a Part 103 Ultralight?
Well, no, it's in the UK. It also has a gross weight of around 2000lbs, so it's probably not subject to any of the relaxed regulations anywhere, although I don't know how the UK homebuilt rules work these days.
I'm astounded that anyone would sell, buy, or mount this to an engine or in an engine bay.
This is Darwin award nomination stuff for everyone involved.
Not to be a 3d print snob but....
Aside from the failure it looks like it wasn't the best print to start with. Lots of rashing from support and curling at the edges. You can see on the flats where the support was and the outer curve of the elbow looks like it likely wasn't airtight. Appears to me to be printed with the inlet facing upwards.
Better support planning, settings and possibly orientation may have helped.
Other commenters are saying it was likely PLA-CF, which I totally agree with based on the testing, but I can't help but think there is no possible way the person printing this item did not know that. I doubt the print would have come off as good as it did when using ABS-CF settings on PLA-CF.
Big chain of poor choices.
I've almost made that exact same mistake (but not on a critical part). I had a bunch of identical rolls with CF loaded filament of different base materials and just looking at the filament you really couldn't tell.
Right...I have loaded the wrong material before.
It didn't take long before I noticed. PLA is super liquid at ABS temps :)
(Not to mention that in my case ABS bed temps would melt the bottom of the PLA)
Oh that could have been quite messy if you had done that unattended.
I've gone through a couple of thousand kg of filament in the last year and I've had some 'interesting' failures.
The actual report[1] holds the answer to the question you’re asking.
CF-ABS (or so claimed)
[1] https://www.gov.uk/aaib-reports/aaib-investigation-to-cozy-m...
With a melting temperature that jist happens to be the same as PLA.
They should sue the seller.
I wonder what material it was printed with.
edit: It was ABS-CF, which shouldn't be used under stress long-term in higher temperatures than maybe 65-70°C, or lower depending on the blend.
Lower, according to the report
"Two samples from the air induction elbow were subjected to testing, using a heat-flux differential scanning calorimeter, to determine their glass transition temperature. The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample"
Yeah, they might have used ABS-CF filament, but unless they got it from a good brand that uses good resin and proper printing parameters, the actual Tg will be lower, plus the stress from the vibration/load could have made the part fail if it was not for the heat later in flight.
Some manufacturers fudge the Tg.
Polymaker Polylite ABS has a claimed Tg of 101°C but the HDT curve clearly shows it starting to lose strength at 50°C, for example.
Polymaker's ABS is dubious too because it is blended with PETG. They are coming out with a Pro version that has a higher Tg and requires way higher chamber temps to print properly.
by the glass transition temperature, i'm willing to bet it was printed with pla (probably pla-cf).
CF-ABS
> An alternative construction method for the air induction elbow, shown in the Cozy Mk IV plans, is a lamination of four layers of bi-directional glassfibre cloth with epoxy resin. The epoxy resin specified for the laminate has a glass transition temperature of 84°C, after the finished part has been post-cured. The aircraft owner stated that as the glass transition temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied the component was fit for use in this application when it was installed
https://assets.publishing.service.gov.uk/media/69297a4e345e3...
What a misunderstanding -- glass transition temperature means different things for thermoplastics (i.e. anything that comes out of an FDM printer like the CF-ABS in question) and for thermosetting resins like epoxy that actually undergo molecular cross-linking during the curing phase. Thermoplastics will get soft and can deform without limit, while thermosets get rubbery but still more or less hold their formed shape.
I think an extended quote shows that this was a really bad call:
“ The aircraft owner stated that as the glass transition temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied the component was fit for use in this application when it was installed. A review of the design of the laminated induction elbow in the Cozy Mk IV plans showed that it featured a section of thin-walled aluminium tube at the inlet end of the elbow, where the air filter is attached. The aluminium tube provides a degree of temperature-insensitive structural support for the inlet end of the elbow. The 3D-printed induction elbow on G-BYLZ did not include a similar section of aluminium tube at the inlet end. Tests and research Two samples from the air induction elbow were subjected to testing, using a heat-flux differential scanning calorimeter, to determine their glass transition temperature. The measured glass transition temperature for the first sample was 52.8°C, and 54.0°C for the second sample.“
> The epoxy resin specified for the laminate has a glass transition temperature of 84°C
This seems very low for the kinds of epoxy I've used. I wonder if the manufacturer specs are highly conservative? Or maybe the material has a shortened lifespan with even moderate temperatures?
I was thinking about the ABS in the article and wondering if I would have made the same mistake. Close to every car manufactured today has plastic intakes, usually bolted right on top of the engine. The incoming air should help keep it cool, especially on aircraft. Maybe it was the radiant heat from a nearby cylinder that melted it?
There are some incredibly low Tg epoxies out there, such as West Systems 105 where "TG onset" is 54°C and the heat deflection temperature is even lower.
Full report here: https://assets.publishing.service.gov.uk/media/69297a4e345e3...
The aircraft owner who installed the modified fuel system stated that the 3D-printed induction elbow was purchased in the USA at an airshow, and he understood from the vendor that it was printed from CF-ABS (carbon fibre – acrylonitrile butadiene styrene) filament material, with a glass transition temperature3 of 105°C.
An alternative construction method for the air induction elbow, shown in the Cozy Mk IV plans, is a lamination of four layers of bi-directional glassfibre cloth with epoxy resin. The epoxy resin specified for the laminate has a glass transition temperature of 84°C, after the finished part has been post-cured. The aircraft owner stated that as the glass transition temperature listed for the CF-ABS material was higher than the epoxy resin, he was satisfied the component was fit for use in this application when it was installed.
A review of the design of the laminated induction elbow in the Cozy Mk IV plans showed that it featured a section of thin-walled aluminium tube at the inlet end of the elbow, where the air filter is attached. The aluminium tube provides a degree of temperature-insensitive structural support for the inlet end of the elbow. The 3D-printed induction elbow on G-BYLZ did not include a similar section of aluminium tube at the inlet end.
> The Cozy Mk IV light aircraft was destroyed after its plastic air induction elbow, bought at an air show in North America, collapsed.
Given what it was would it have been under actual stress?
Certainly seems questionable to use any 3-D printed plastic material for exhaust. That’s absolutely going to be too hot.
It was an intake manifold, so it's continuously under suction. At the temperatures in an engine bay the plastic probably gradually creeped to a point where the restriction increased the suction and suddenly it collapses completely.
Oh the suction, I wasn’t considering that. I was thinking of general compression or tension between the connections on the ends.
I wonder who installed it. Was the pilot home 3D printing mods for their plane? And is that even allowed? Super concerning if there was a company behind the installation.
I'd think any semi competent engineer would know better.
Edit: from the report - "A modification application was made to the LAA in 2019, by the aircraft owner2 , to replace the engine’s throttle body fuel injector with a mechanical fuel injection system. This system consisted of a fuel controller, high-pressure engine-driven fuel pump, electric auxiliary fuel pump, fuel flow transducer and associated fuel hoses, filters and fittings. Following flight testing, the modified fuel system was approved by the LAA in 2022. The modified fuel injection system had accumulated 37 hours in service when the accident occurred."
So the pilot himself and the LAA were incompetent. LAA is an association for amateur pilots though so I'm not sure what level of rigour they "approve" things with.
In addition to what other users have mentioned, the airplane changed hands in August 2024, after the modifications were made.
Nearly anything is allowed for experimental amateur-built aircraft like the one in this incident. Unapproved modifications to certified aircraft are forbidden in most parts of the world.
The LAA classified the proposed modification pf the overall fuel system as minor based on the owner’s description of it, and approved it on that basis. But the owner lied and did not disclose the fact that the induction elbow was modified at all or that it was 3D printed. The report does not discuss any required inspection by a person authorized by the LAA prior to returning the aircraft to service. So it seems like the LAA modification process is a trust-don’t-verify policy.
The plane is an experimental class, so I doubt they have to follow a lot of regulations.
I'm massively paranoid that some cable clips I printed that will sit on a circuit board will perish in the heat. Meanwhile, some idiot couldn't care less about thermal stability for flight hardware!
The person that installed should have thought more carefully about it. But the person that printed it and sold it should face some legal repercussions. Totally irresponsible what they did.
Belite, a company that folded (and just renamed themselves) after a certain number of crashes of their experimental ultralights, sold my dad a plane where the AOA sensor was malfunctioning, the propeller hit the ground if there was someone in the plane, and one wing side was longer than the other. By a visible amount. My dad broke a set of propellers and they sent him a new set with 3" cut off each blade. i have those in my shed.
I'm no aerospace engineer or anything, but that plane shouldn't have been able to stay in the air.
and, lo, it didn't, the motorcycle engine used as the prime mover sputtered out at 200' AGL and since it's not a glider (and i don't even think it can glide), it crashed straight into the ground.
Fly an ultralight if you want, just be aware that people will think very poorly of you.
At a glance, that looks like worse than merely the negligence of using a new technology.
The whole point of 3D printing is that the material is moldable when hot but rigid when it cools. And people really should be aware that engines get hot.
I think there's some nuance missing here. "Hot" is a scale, not just a true/false check.
>The whole point of 3D printing is that the material is moldable when hot but rigid when it cools.
Which means what exactly? Aluminum will go soft under high temperatures as well, yet this part would not have failed if it was made out of aluminum.
The failure is not the material, the failure is someone neglecting the operating conditions or material properties when choosing materials.
This exact part could have also been milled out of some plastic and would have failed the same way. The method to produce that part is only relevant in so far it is open to more people.
Looks like the part was advertised as ABS-CF, but may have actually been PLA-CF, which makes a big difference.
There are plenty of even higher temperature materials that can be 3d-printed. PAHT-CF is fine at fairly high temperatures (the nozzle temperature needs to be over 260C), and SLS printers can print things like aluminum.
Apparently they thought it's ok because the published glass transition temp is higher than the epoxy used for fiberglass construction
Bought it at a get-together.
Like gunshows, it’s a magnet for bad ideas.
I think the main issue is that many filament manufacturers mislead or outright lie about their filament capabilities.
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Thankfully minor injuries.
A thermoplastic in an engine cowling is insane. It’s crazy that this was being sold the supplier should have known better, as should the buyer. 3D printing can be used to make a fiberglass or carbon fiber mold which is already a lot of the work of making the part.
It would be interesting to know what filament was used, in theory some high temp filament could be suitable but I would be nervous putting those on a car let alone a plane.
Edit: https://assets.publishing.service.gov.uk/media/69297a4e345e3...
The actual report includes the important details, ABS-CF which they thought was safe because they underestimated the glass transition temperature of epoxy fiberglass.
I just watched a fun video of a guy bringing a 1978 Datsun 280Z up to date. He kept the existing engine but upgraded it with modern electronic ignition and computer control. As part of all that, he fabricated various parts in plastic by 3D printing, but then had the final versions made elsewhere in metal -- some by a CNC shop you send CAD files to, and one by a manual machinist in Switzerland with his own Youtube channel. The latter has to be case hardened, which the machinist did.
The 3D printed plastic parts were very useful to prove out the parts' shapes.
https://www.youtube.com/watch?v=jZ38C-M3tyk -- engine upgrade
https://www.youtube.com/watch?v=D2bxsEyYdo0 -- My Mechanics making the part
This last line is concerning:
>The Light Aircraft Association (LAA) said it now intends to take safety actions in response to the accident, including a "LAA Alert" regarding the use of 3D-printed parts that will be sent to inspectors.
Does this mean that anybody using any 3d printed part in an aircraft will be subjected to this scrutiny? If I use the proper materials with a suitable printer (eg, printing PEEK with a properly specced printer), how much convincing will it take to get these governing bodies off my back?
The part was a "plastic air induction elbow", i.e. this kind of thing:
https://duckduckgo.com/?q=plastic+air+induction+elbow&ia=ima...
so, if you were thinking "who would use a 3D-printed part", remember that it may otherwise also have been made with some liquid material, but using a mold, and perhaps two parts using a mold that are joined with re-heating etc. - and now it no longer sounds so outlandish.
The picture of the collapsed one is at https://ichef.bbci.co.uk/news/1024/cpsprodpb/7fee/live/52acf...
It would be curious to know what parts and connectors it should look like are.
And that texture on the right hand side of the image doesn't exactly look like something in a healthy engine.
Hardware engineering is hard. Especially for any safety critical component.
In this case engineering was done by someone, who either did not understand the material he was working with, or the operating conditions in which that part was deployed.
Obviously no testing or any kind of proper engineering was done to create requirements validate them and verify them.
Being able to design a 3D model and print it does not mean you are done with engineering. It is just one step in a very long chain, which is needed to produce devices which stand up to their use.
And this is why (at least for the US) aviation parts have such an onerous paperwork overhead, why a seemingly cheap part like a $.50 bolt balloons to much greater. Granted this aircraft was a UK-equivalent to "experimental" in the US, where you can pretty much do anything to it, I'm of the opinion that doesn't excuse maintenance and adding fly-by-night parts that borders on negligence. Stick to a minimum standard, if not just out of shame of something that could happen.
Hah! I've actually 3D printed a part of an intake before. Just as a prototype, to allow me to get a Keihin carb on a motorcycle that had a CV carb.
Printed it on an SLA machine though! I was concerned enough about chemical attack even then, even though it was a temporary part. Never really thought about doing it in filament.
correction to the title: the plane crashed because the owner is a moron, not because he bought a 3d printed part but because he failed to ensure his provider is trustworthy and instead used a fly-by-night nobody to fit a machine that can kill him at any moment.
Absurd what people will do to save a buck.
Why is the 3d-printed part highlighted; upon first reading this looks like the part softened; it didn't separate on FDM boundaries. Wouldn't a similar thing have happened if it were formed in a different way, but of the same materials?
They included everything but the 3D printed material. If it was PLA, no surprise (and no excuse). Even ABS might not stand up to the temperatures at that location. I hate it when a news report tells you everything except details that might make a difference going forward.
It sounds like simply running the engine on the ground for a few hours would have been a much cheaper way to debug this issue. Safer, also.
It's a light aircraft, the owner probably built it and is allowed to fix it. So it's probably not a company that printed the part.
Per the report
> The aircraft owner who installed the modified fuel system stated that the 3D-printed induction elbow was purchased in the USA at an airshow, and he understood from the vendor that it was printed from CF-ABS
Are those class 8 bolts holding a plastic (PLA? PETG?) part in place? I guess the original part would have been some sort of metal?
Wow. It's called "thermoplastic" for a reason.
i'm confused: if they were on final and lost power, why not just glide to the runway??
edit: nvm, i found my answer in the actual report.
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3D printing parts is FAA approved?
This occured in the UK, so not really relevant to the FAA.
In the US though, yes, the FAA would not have a problem with this. This plane would be registered as experimental, meaning you can install unapproved parts. It does have to be inspected, but that can be done by the builder (not the designer, just the guy who built that particular example), or an airplane mechanic.
I know quite a few experimentals with 3d printed parts (including my own). I don't know any where they are installed in a place where failure would result in a crash. Typically I see them used as convenience stuff, in my case I am using a 3d printed catch to hold my upward opening door while I load the plane. If it breaks in flight, I wouldn't even know. If it breaks on the ground, the door will close.
I'm not sure Gloucestershire is under FAA jurisdiction.
It was purchased at a U.S. airshow
Flea markets at US airshows are not under FAA jurisdiction.
I have attended said airshow for decades and occasionally buy stuff in the flea market myself. Old used scrapyard parts, next to some inventor’s homemade jet engine, next to tons of raw materials of unknown provenance, next to ginsu knives and miracle frying pans. Here’s what it looks like on video. Wow, I missed those hand grenades for only $10 each, what a bargain.
https://youtu.be/kKZ8Omj5cNA?si=bMQGS3VxN6ljyW19
https://www.aero-news.net/index.cfm?do=main.textpost&id=cf1c...
They sold an entire UK county at an airshow?
Yes. I mean not this one, but the FAA has definitely approved 3D printed parts. SpaceX's raptor rocket engines, for instance.
Some of the most advanced aircraft engines for commercial airliners contain 3D printed parts: https://www.cfmaeroengines.com/leap
The FAA denying approval to parts based on how it was manufactured and not how it performed under testing would be totally ridiculous.
Lots of F1 parts are 3D printed, as well as many satellite rocket parts still flying. You just need the proper materials.
You may want to ask about the LAA: Light Aircraft Association.
Crash occurred in UK
I hope 3-D printing becomes obsolete when robots can achieve the same efficiency with using the standard construction materials. That should take away all benefits of 3-D printing over regular builds.
You're against additive manufacturing because you want robots to become craftsmen? That's... a pretty wild take, to put it mildly.
I'm curious, what are "standard construction materials" and "regular builds" to you? And what do you think those robots are made of?
You don’t need a robot, especially in the colloquial sense meaning humanoid. Better additive manufacturing techniques than desktop FDM printers exist, and CNCs can turn these parts out from much better materials all day.
3D printing isn’t entirely about automation, it’s also a way to get shapes that are impossible to manufacture traditionally. Modern rocket engines almost all use 3D printing because the shapes are so highly optimized.
This might be Darwin Award eligible!
> The sole occupant was taken to hospital with minor injuries.