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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

#131

Post by genewitch »

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.

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

#132

Post by jacquesm »

Ccecil wrote: post #100

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. O…

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.

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

#133

Post by jacquesm »

shmeeed wrote: post #116
ohazi wrote: post #4

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.

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

#134

Post by ggreer »

gpm wrote: post #65
brovonov wrote: post #47

Earlier quoted context omitted.

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.

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

#135

Post by jacquesm »

lazide wrote: post #61
gpm wrote: post #43

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…

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.

> 3D printing (especially using filament) allows idiots to enter entirely new areas of endeavor.

That's true for any tool.

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

#136

Post by [deleted] »

jacquesm wrote: post #127
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.

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 kin…

[deleted]

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

#137

Post by Centigonal »

phoronixrly wrote: post #122
Centigonal wrote: post #110

Earlier quoted context omitted.

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?

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.

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

#138

Post by soursoup »

SoftTalker wrote: post #115
Centigonal wrote: post #102

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. Th…

Figured it was experimental; no A&P who cared about his future would install a 3D printed part on a certified aircraft.

Loads of commercial aircraft and jet engine parts are manufactured using additive manufacturing, or ”3D printing”

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

#140

Post by crumpled »

phoronixrly wrote: post #122
Centigonal wrote: post #110

Earlier quoted context omitted.

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.

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