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A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

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Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#121

Post by michaelt »

delichon wrote: post #54
fudged71 wrote: post #27

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.

> 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.

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#122

Post by phoronixrly »

Centigonal wrote: post #110
phoronixrly wrote: post #107

Earlier quoted context omitted.

[flagged]

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?

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#123

Post by SoftTalker »

ToucanLoucan wrote: post #85
lemonwaterlime wrote: post #40

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…

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.

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.

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#124

Post by geocrasher »

Aeolun wrote: post #98
ToucanLoucan wrote: post #85

Earlier quoted context omitted.

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.

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?

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#125

Post by cibyr »

ToucanLoucan wrote: post #85
lemonwaterlime wrote: post #40

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…

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.

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

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#126

Post by saltcured »

Treegarden wrote: post #64
elicash wrote: post #57

Earlier quoted context omitted.

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°…

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 th…

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.

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#127

Post by jacquesm »

ToucanLoucan wrote: post #85
lemonwaterlime wrote: post #40

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…

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.

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#128

Post by defrost »

phoronixrly wrote: post #111
averynicepen wrote: post #105

Earlier quoted context omitted.

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 func…

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)

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#129

Post by jacquesm »

geocrasher wrote: post #124
Aeolun wrote: post #98

Earlier quoted context omitted.

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.

Re: A Cozy Mk IV light aircraft crashed after 3D-printed part was weakened by heat

#130

Post by Centigonal »

jacquesm wrote: post #120
Centigonal wrote: post #106

Earlier quoted context omitted.

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.
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