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
(Although note that these are not using plastic parts, to be clear.)
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.
The 3D printing isn't the actual problem, as you note.
[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!
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.
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.
You don't make analogies out of things that are the same, that's one of the hallmarks of an analogy.
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.
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?
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.
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.
The comparison does not seem as absurd to me as it does to you. vOv
I see multiple examples of it in this thread.
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.
(unless that primary domain tends to attract a lot of people who tend to the hyper-literal /s)
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".
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.
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)
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.
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.
Not a new story in the progression of human endeavors; see the printing press, perspective painting, digital photography, residential construction.
1: https://nymag.com/intelligencer/2014/10/soylent-creator-hack...
And if this part was simply 3d scanned and printed in whatever material seemed strongest,
Then it could be an apt analogy
Installing life-critical parts of shoddy engineering into a vital system of your airplane is a good example of when things do matter.
That should be so obvious that I wonder if it was DIY by the pilot.
> 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.
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.
Looks like they would like to make the early flight mistakes themselves instead of following air worthiness guidelines.
In the end it depends on the application. Vibe coded flight management systems, anyone?
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/...
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.
Or do they get their parts from some vendor at a swap meet who spends most of his time fiddling with his Ender 3?
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.
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.
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).
Something funny is going on with this material given the report is saying they measured a glass transition temperature of ~50C.
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.
Polycarbonate shows little change vs pressure [1]:
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.
Or it was ABS-CF but they forgot to dry the filament /s
Edit:
Material was CF-ABS
I wonder if he was erroneously sold a demonstrator part?
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."
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.
3D printing (especially using filament) allows idiots to enter entirely new areas of endeavor.
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
That's true for any tool.
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.
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.
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)
I've gone through a couple of thousand kg of filament in the last year and I've had some 'interesting' failures.
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.
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
CF-ABS (or so claimed)
[1] https://www.gov.uk/aaib-reports/aaib-investigation-to-cozy-m...
They should sue the seller.
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.
"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 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.
> 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...
“ 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.“
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?
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.
Certainly seems questionable to use any 3-D printed plastic material for exhaust. That’s absolutely going to be too hot.
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.
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.
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.
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.
Like gunshows, it’s a magnet for bad ideas.
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.
> 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
I'm curious, what are "standard construction materials" and "regular builds" to you? And what do you think those robots are made of?
edit: nvm, i found my answer in the actual report.
Absurd what people will do to save a buck.
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.
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.
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.
The FAA denying approval to parts based on how it was manufactured and not how it performed under testing would be totally ridiculous.
