Newbie questions re alternative engine validation.

[RichB]

I've followed the threads for a while, and have a couple of thoughts and questions re the process the alternative engine development guys go through before they start selling / building for folks. It might sound a bit naive, because the answers to these questions is probably just $$$$$$ but...

First thing is ground testing. I'm not talking about putting it a dyno for 40 minutes, I'm talking about running it for 3 months or so - with a prop on - and yes, that means many thousands of dollars of fuel burn, noise, etc. Something computer controlled to emulate the various flight phases... start, run-up, 100% take-off, 75% cruise, idle, and shut-down, cool down, and repeat. Several times a day, for months. Does anyone do anything like this? How about with shaker rigs? Is it feasible to set up the test in a baro chamber to simulate change of altitude?

Second thing is component validation. Do any of the alternative folks go as far as the best aviation builders do, or is more like they un-crate a motor (and assume the factory got it right) and bolt on a PSRU (which also may or may not have been validated to the level desired) and call it done - until the next customer's engine breaks, and the next improvement is made? That development cycle might have worked in WWII, not so much these days.

How are the custom and add-on parts (if any) typically designed, built, and selected? Best practice or best guess? Reputation, or FEA and MTBF?

While packaging / FWF is certainly a huge part of the equation, it's difficult to find any hard data on longevity and testing / QA on most of what's advertised, beyond X customers for Y hours. From what I've seen and read from the Mistral Rotary guys, they've gotten serious about this sort of stuff... part of the certification program perhaps, but how about the Subaru and Chev (and any other) suppliers?

I'm not looking to stir the pot as much as these questions might imply, I'm just wondering how much formal design, engineering, and testing goes into the experimental solutions (customer flying shouldn't be product testing IMHO, but it's good feedback and fodder for further development).

[rv6ejguy]

All good questions. Capabilities and financial backing varies widely but generally very little real engineering is being done in this world. Some exceptions would be EPI but most people can't afford what they offer unfortunately. (The old double edged sword again) I hate that!

Powersport had some real validation and testing behind their PSRUs and FF packages.

Maxwell has actual engineers on staff I know for a fact.

Autoflight in NZ has a good rep and seem to apply science to their products.

You don't need a big in house engineering staff to do this right but it sure is helpful. You better be darn good in the practical world of mechanical things otherwise and no matter who you are, you still have to test a lot before product release.

You are right, customers should not be doing primary product testing for vendors. My advice is for customers not to even put down a deposit on this stuff unless the vendor has their own aircraft they do product flight testing with. If they don't have enough faith in their products or money for that, forget 'em. Unlike a some fancy glass, this stuff can kill you.