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10/23 Raptor Video

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231TC

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Aero momentum website implies inflight testing is more important. Doesn't list ground test hours, so I haven't found any industry standard yet:

"From this point we have spent over a year testing both in the lab and more importantly in the real world."
That sounds like more of a marketing line than a serious description of their testing program.

But regardless, in flight testing may be "more important" in some ways but that doesn't mean you should skip or shortcut the "less important" ground testing. It's still essential to do the ground testing before flight if you're trying to minimize risk, which should be a major consideration.

I don't know of an industry standard either, but I'd want at least 100 trouble-free hours at full power run through a new design PSRU before I'd leave the ground with it. Raptor may have had 100+ hours on the ground before flight, but seems like only a couple hours tops at full power. I lost track of the redrive iterations so I have no idea how much time the current one has on it. Each time you modify it, you're starting over with zero time on the current design (although not zero time in terms of wear on any parts reused from the previous version...worst of both measures).

Raptor is spending a lot of time at 3,000 feet and lower 3-6 miles from the airport. That's at least approaching reckless without a much more thorough test/proving of the drivetrain on the ground. (Actually, I don't like that even in a proven airplane, but it's not uncommon so I must be an outlier in that regard.) The low altitude loitering isn't even the biggest concern in this regard, since takeoff power is the most stress the PSRU sees.

All that aside, I'm still thinking it's more likely to be an electrical issue rather than a PSRU failure that causes the first undeniable emergency. The PSRU may very well last many hours without catastrophic failure. But the non-redundant throttle-by-wire still comes to mind every time I think of Raptor, again most significant at takeoff. But the designer/builder seems blissfully unconcerned by it, even though it could be fixed easily and cheaply.
 

Toobuilder

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Ground testing is very much related to flight test in the same sense that 1 G stall behavior is related to flutter testing - they are simply at different places in the operating envelope of the vehicle.

Most "Flight" test departments are in reality simply "test". We are involved in component bench testing, SIL, structures, GVT, Fuel flow, Engine runs, low and high speed taxi as well as flight envelope expansion.

Its all part of the same process of crawl, walk, run.
 

BBerson

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That sounds like more of a marketing line than a serious description of their testing program.
Website said the engines were used in boats and airboats years before aircraft. That might be the real world testing.
 

BBerson

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I don't know of an industry standard either, but I'd want at least 100 trouble-free hours at full power run through a new design
Part 33 Engines is 150 hours for certificated. I checked Viking and found nothing about testing. I suspect EA-B industry does little if any engine testing because each unit and airframe is unique.
 

231TC

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New vid is up, haven't watched a second of it and I'm already shaking my head from just the title.
 

231TC

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New vid is up, haven't watched a second of it and I'm already shaking my head from just the title.
And it's worse than I thought. He's testing the autopilot but apparently hasn't read the manual yet. I guess he'll get around to that after production is underway.
 
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donjohnston

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The FAA minimum 40 hours of flight test is a minimum, and in the case of funky-wonky-chunky-monkey powertrains like this... 40 hours is probably not nearly enough. The FAA I believe now gives you a reduction in E-AB test hours if you use a certified engine (from 40 to 25??), but in fairness there should be a quid pro quo and a longer or more demanding type of testing for something like this.
Correct. If you have a certified engine and prop then you only have a 25 hour phase I test period. I was flying my Velocity home at 27 hours. :pilot:
 

donjohnston

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And it's worse than I thought. He's testing the autopilot but apparently hasn't read the manual yet. I guess he'll get around to that after production is underway.
Yep. Testing the autopilot having not read the manual so he didn't know what "Trim Up" meant. Testing the autopilot before doing the first stall test to know where the canard is going to stall. And the static port error still hasn't been addressed.
 

PPLOnly

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Everything else is fixed and sorted, handling characteristics are well known, pitot system is spot-on, so time to test the accessories I guess. After that comes the real hard part, upholstery colors.
 

John Harlan

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Every landing seems to be performed at relatively high power and high speed. There seems to be no test objective to evaluate and develop experience with the power-off condition. Given the experimental nature of engine and PSRU, and associated vastly higher than typical likelihood of a power loss, in my view the omission of this objective is the single greatest self-imposed risk. This, combined with low altitude operations beyond gliding range (to the runway), for the majority of every flight, including even the portions of the pattern where this could easily be achieved, is particularly puzzling.
 

wsimpso1

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Aero momentum website implies inflight testing is more important. Doesn't list ground test hours, so I haven't found any industry standard yet:

"From this point we have spent over a year testing both in the lab and more importantly in the real world."
I keep preaching on this. To have a powertrain program be successful several things are essential:
  • Well schemed out and well analyzed designs so that fatal flaws are eliminated, high value failure modes are protected against and eliminated where possible, making the design likely to be durable;
  • Thorough bench and dyno test programs designed to expose weak spots, high value failures, design defects, and flaws in manufacture, and then demonstrate life targets are met. You tear down your stuff after it has run and see if anything is showing wear and tear you did not expect. You look for damage, pitting, wear materials, incipient failures, etc. Then you fix the things that you find wrong;
  • Then operational testing, because no bench test ever covers the exact conditions of actually using the product. And you repeat the skepticism about how it is doing, looking for wear materials in the oil, tearing them down to see how internals are doing, and so on.
Mark at AeroMomentum has a valid point. He has designed his stuff to be sturdy in the real world. He has run his powerplant systems on stands for bunches of hours. He has established his operating parameters and envelope. But how does one simulate spin entries or abrupt rolling and pitching on a stand? How does one find out how long it actually lives with someone flogging it or babying it with modest power and short runs? How does one one find out how it does in Alaska and the Caribbean and in deserts and jungles? Go fly it and see how it does. If you have done the job up until now, the customers using your Beta product have little in the way of problems, and you make a big effort to solidly fix what remains. Ultimately though, the customer runs the product that comes from the shop way more and in more varied ways than some folks will even believe. That is where one finds out if the product is really good or just a pretender. No way to avoid this, but if a good job was done designing, engineering solutions to any remaining issues, and knocking them out, it is a pretty ethical way to do business. Not perfect, but if done well, it can be pretty darned good.

In fairness to Mark, he already has a lot of good customer time on working airboats running hard. That should count for a lot compared to whatever he has on a bench, and also validates his design/analysis/test processes. The thing that I keep emphasizing is that design that is well based is hardly a guess - one KNOWS where your analysis puts you on all the critical parameters. Then one tests that product and see that it proves reliable and durable or adjusts the product until it does. Once one knows that, the parameter set on future products must also be as good or better than the already proven one. This is engineering the next product.

Now if instead one starts with a set of guesses, and do not know where things like stresses, temperatures, etcetera are, and just go test, then bump materials or sizes or coolers until it passes your base test, one still does not know how well it will last or if the guys doing their thing in the field will just shred it. And one has no basis for making the next product decent from the start.

The issue of "testing on the customer" comes about when one builds too few test pieces (amazing how often sample sizes of one are accepted) with guessed at parameters, run it a couple hours on a stand, inspect and fix the biggest issue you find, run and keep fixing things on that one powerplant for a few more hours, and then decide to market and ship a bunch to unknowing customers so it can launch on time and make some money now. Is the customer protected a reasonable amount? Done this way is fundamentally unethical. Will the outfit grow and prosper? I personally hope that this producer is punished by the customer base.

Billski
 
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BBerson

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Why would any customer watching these videos purchase a PSRU that needs repair every 30 minute flight?
Seems likely he will abandon the PSRU at some point after it fails in flight. That's why I suggested he stay close to the airport. I calculate an 8.5 mile glide from 3000 feet depending on the wind if the glide ratio is 15.
 
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Kyle Boatright

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I calculate an 8.5 mile glide from 3000 feet depending on the wind if the glide ratio is 15.
Most anyone is going to throw away a thousand feet of that altitude in A) Surprise and troubleshooting delay. B) Turning towards the airport. C) Pre-touchdown maneuvering.

So he's gonna have 2,000 of altitude to work with to calculate his glide distance. That gives him 2,000' x 15 = 30,000' = 5.5 miles.

And I'm not sure he's gonna get 15:1 with that fat shape.

Let's hope he has plenty of altitude in the bank if it comes to that.
 

BBerson

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Yeah, there are plenty of variables. If the belt breaks the prop will spin and make drag. Can it feather?
Then he also has a chute.
I assume he may stay closer or go higher if the prsu tests continue.
 
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