> 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.
