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

bbc.com

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

#191

Post by cjbgkagh »

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.

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

#192

Post by cjbgkagh »

mwambua wrote: post #89
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°…

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.

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

#194

Post by scarier »

dghlsakjg wrote: post #186
ahepp wrote: post #103

Earlier quoted context omitted.

Do we know whether the part was made out of spec, or whether the spec specified inappropriate materials?

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 m…

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.

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

#195

Post by jibe »

potato3732842 wrote: post #176
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…

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..

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

#196

Post by aidenn0 »

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?

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

#197

Post by [deleted] »

dghlsakjg wrote: post #186
ahepp wrote: post #103

Earlier quoted context omitted.

Do we know whether the part was made out of spec, or whether the spec specified inappropriate materials?

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 m…

[deleted]

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

#198

Post by kube-system »

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.

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.

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

#199

Post by aidenn0 »

o11c wrote: post #7

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.

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.

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

#200

Post by buildsjets »

elicash wrote: post #181
stetrain wrote: post #22

Earlier quoted context omitted.

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...

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