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Raptor Composite Aircraft

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Victor Bravo

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The old film of the F-14 becoming uncontrollable and crashing into Long Island is pretty memorable. I've only seen it once on some TV documentary, and it was years ago, and I still remember it. I didn't remember it was on the first flight.
 

Billrsv4

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Valid post, and has oft been mentioned that a 2nd pre-production craft is going to be an absolute must do.

But the time and expense is a major setback, about another 2 years from whenever #1 flies in some sort of controllable manner, to when #2 will see airtime.
Racer, often times there is even more time between first flights ans a pre-production example. Witness the DeltaHawk Diesel development. they first flew the engine about 6 years ago (est.) on a velocity and only now are they talking about selling to the public, and I still don't know if they have delivered any customer engines. They did get one into a Cirrus SR20 and claim to be the NEXT BIG THING. We will see...
Bill
 

Tom Nalevanko

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I still struggle with the concept that in the States you can build anything that requires little or no validation of the materials/design/execution , inview of the fact that you could sell said product to Joe Public. Here in the UK, we have SSDR ( Single Seat De Regulated ) but are constrained by weight, wing loading and stall speed, (this is what I am building), but still have my design and engineering validated by a member of our LAA ( your EAA).
We declared our independence in 1776. Of course, before aeroplanes...

Best,

Tom
 

jet guy

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I think Peter is going to have a difficult time finding a bona fide test pilot to try to fly this thing. He has already been declined by Wasabi and Len Fox, and Saso Knez, the Pipistrel test pilot has taken the extraordinary step of issuing a very blunt and public warning about trying to fly this plane, on Peter's youtube channel. The test pilot community is a small one, and word gets around pretty good, so anyone considering getting involved with this 'program' is going to go through it with a fine tooth comb.

They will find many items that raise questions. Even a look at his published specs will show this: Max speed of 300 knots at 25,000 ft on 300 hp.

A quick calculation will show that 300 hp at this height and speed, and an assumed prop efficiency of 0.85 will yield just 277 pounds of thrust on an ISA standard day. Dynamic pressure at this speed and height is 137 lbf/ft^2, so in order to make that speed on 277 lbf of thrust requires a drag area of no bigger than 2 square feet.

That's less than half of the drag area of an SR22, and about twice the drag area of Mike Arnold's tiny, amazing AR5. No aeronautical engineer on earth could possibly come up with that kind of number, and any professional is going to wonder just what kind of person could seriously come up with something like that.

Even more worrisome is the 'design' section of the Raptor website. On this page we have a lot of fancy-looking illustrations that are supposed to be CFD results. Note the graph here, supposedly showing his 'CFD' comparison of Raptor drag and lift to a SR22.

We see that at 190 knots the Cirrus drag is a nice even 2,000 pounds of force...which would of course require a 2,000 pound thrust in straight and level flight, about what a Lycoming/Honeywell ALF502 turbofan engine makes in cruise on the Challenger 600 [7,500 lbf static].

And if you look at his plot lines for lift, you will find that the SR22 thus has a very sleek L/D of about 1.8 to 1.

In reality, the SR22 cruising at 190 knots would have about 380 pounds of drag, only about FIVE times less than the 'CFD' results from Peter. [Since drag equals thrust in straight and level, engine power of 310 hp * 0.85 prop efficiency * 0.85 max power setting = 224 THP, times 550 lb*ft/hp, divided by airspeed of 320 ft/s = 384 lbf of thrust = 384 lbf of drag.]

Who could possibly come up with numbers like that? And what about that 'range' of 3600+ nautical miles? Most midrange bizjets don't have that kind of range; the Gulfstream G280 clocks in at 3,590 nm.

Then he 'engineers' an absolutely 'unique' staged turbo setup that is on backwards and makes the engine a ticking time bomb. He gets aileron flutter on a high-speed taxi, then 'fixes' that by attaching a weight far below the hinge line, which means that if there is any fore-aft flexibility in that wing, it will go right into flutter again, like that which plagued the old TBF-1, which despite being properly mass balanced with a weight just slightly below the hinge line, had slightly more fore-aft wing flex due to the carrier wing-folding setup.

At what point does the moderately knowledegable aviator say to himself, 'stay far far away from this thing and this guy?'

PS: I seem to recall that he weighed his engine on the hoist and it weighed something like 900 pounds.

PPS: His cooling system will make huge amounts of drag. The SR22 turbo has about 25 percent more drag than the NA version, due only to the extra cooling drag of the extra hp and the intercoolers. There is a reason that liquid cooled fighters of WW2 spent a lot of time on reducing cooling drag, best example being the P51.
 
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Victor Bravo

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The test pilot community is a small one, and word gets around pretty good, so anyone considering getting involved with this 'program' is going to go through it with a fine tooth comb.
Somebody call "Crazy Dave" Morss, and tell him to disconnect the phone!

Norm Howell is busy at Boeing and probably retired, Jim Payne is busy flying a glider, and our own cblink.007 is about to go back and be a rotor-head,... so none of them are not gonna get hurt by this.

Is Sean Roberts and the National Test Pilot School still running at Mojave? I met one or two of those folks 25+ years ago. Maybe they can take this on as a school project, with generous educational grant funding from Peter.
 
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pictsidhe

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I suspect that Peter was unhappy with Wasabi turning up and not flying his baby, three times. It can't be cheap flying them out, especially if bringing a chase plane. With the number of squawks already found, they likely told him it would probably be many visits to complete the test program.

With Len and now Wasabi out, he may have trouble finding a professional pilot.

Is there a 'Test flying for dummies' book? A website, perhaps?
 

jet guy

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And just to put Peter's 'numbers' into perspective. When the TBM 700 came out it could go 300 knots at 25,000 ft on 700 hp [it could carry full power to FL280]. That's an airframe with just 10 percent more drag area than an SR22 turbo, about 5.5 square feet. It's almost certain that the Raptor has at least that much drag area, what with its cooling 'system' where intake air is just dumped into the engine compartment. It could in fact be much higher than that.

There is nothing inherently wrong with the idea of taking a diesel engine and adapting it for light aircraft propulsion, Diamond has been working on that for a long time, with mixed success and shooting for goals much more modest, to say the least.

But the way so many things have been badly botched here, right from the initial performance projections and basic aerodynamic computations, to the redrive and turbo problems, to the massive weight growth, indicates strongly that the person in charge has no business trying to design an airplane.

Anyone considering signing up to fly this thing needs to think hard about what other problems such a level of competence may have got wrong.
 

datadriver

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Witness the DeltaHawk Diesel development. they first flew the engine about 6 years ago (est.) on a velocity
That flight occurred in 2003. 17 years of fail. I am slightly bitter, because since 2003 I had been hoping to power a Velocity with such a beast. When 2017 rolled around and I needed an engine they were still not ready ;)
 
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TurbAero

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They will find many items that raise questions. Even a look at his published specs will show this: Max speed of 300 knots at 25,000 ft on 300 hp.

A quick calculation will show that 300 hp at this height and speed, and an assumed prop efficiency of 0.85 will yield just 277 pounds of thrust on an ISA standard day. Dynamic pressure at this speed and height is 137 lbf/ft^2, so in order to make that speed on 277 lbf of thrust requires a drag area of no bigger than 2 square feet.

That's less than half of the drag area of an SR22, and about twice the drag area of Mike Arnold's tiny, amazing AR5. No aeronautical engineer on earth could possibly come up with that kind of number, and any professional is going to wonder just what kind of person could seriously come up with something like that.

Even more worrisome is the 'design' section of the Raptor website. On this page we have a lot of fancy-looking illustrations that are supposed to be CFD results. Note the graph here, supposedly showing his 'CFD' comparison of Raptor drag and lift to a SR22.

We see that at 190 knots the Cirrus drag is a nice even 2,000 pounds of force...which would of course require a 2,000 pound thrust in straight and level flight, about what a Lycoming/Honeywell ALF502 turbofan engine makes in cruise on the Challenger 600 [7,500 lbf static].

And if you look at his plot lines for lift, you will find that the SR22 thus has a very sleek L/D of about 1.8 to 1.

In reality, the SR22 cruising at 190 knots would have about 380 pounds of drag, only about FIVE times less than the 'CFD' results from Peter. [Since drag equals thrust in straight and level, engine power of 310 hp * 0.85 prop efficiency * 0.85 max power setting = 224 THP, times 550 lb*ft/hp, divided by airspeed of 320 ft/s = 384 lbf of thrust = 384 lbf of drag.]
On another thread, Autoreply attached an Excel spreadsheet calculator for flat plate area which includes a second tab listing the (claimed/verified) flat plate areas for some common aircraft. I am attaching that calculator to this post for interested folks to view.

In the list of aircraft are some with flat plate areas listed as being under or close to 2 sq.ft. such as the Lancair 360, Nemesis NXT and the 4 seat White Lightning. The author of the list questions the White Lightning's claimed FPA of under 2 square feet but if I insert known powers/speeds for the WL into the calculator, even the calculator spits out a FPA of under 2 sq.ft. so again, if the calculator is accurate, a 4 seater could potentially have a low FPA.

Of course, it now begs the question whether the Raptor is in the same league as the Lancair 360, Nemesis NXT and even the White Lightning in relation to flat plate area. Many will have their suspicions or opinions but any validation will only be forthcoming when it flies. Let's see what transpires.
 

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cblink.007

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Is there a 'Test flying for dummies' book?
There was such a publication I got while a student at NTPS, among many: Fixed Wing Performance

Then, there is the DoD Flying Qualities Handbook and the SFTE Reference Handbook.

Plenty more where these came from!

PM can call me if he wants; I'll be happy to advise, but as for flying, I think I'll take a hard pass on this one, especially since he seems to not want to give a test team carte blanche over the program
 

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cblink.007

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That flight occurred in 2003. 17 years of fail. I am slightly bitter, because since 2003 I had been hoping to power a Velocity with such a beast. When 2017 rolled around and I needed an engine they were still not ready ;)
I was watching DH way back in the day too. Since about 2005-ish if I remember. The price of them have skyrocketed!!
 

pictsidhe

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On another thread, Autoreply attached an Excel spreadsheet calculator for flat plate area which includes a second tab listing the (claimed/verified) flat plate areas for some common aircraft. I am attaching that calculator to this post for interested folks to view.

In the list of aircraft are some with flat plate areas listed as being under or close to 2 sq.ft. such as the Lancair 360, Nemesis NXT and the 4 seat White Lightning. The author of the list questions the White Lightning's claimed FPA of under 2 square feet but if I insert known powers/speeds for the WL into the calculator, even the calculator spits out a FPA of under 2 sq.ft. so again, if the calculator is accurate, a 4 seater could potentially have a low FPA.

Of course, it now begs the question whether the Raptor is in the same league as the Lancair 360, Nemesis NXT and even the White Lightning in relation to flat plate area. Many will have their suspicions or opinions but any validation will only be forthcoming when it flies. Let's see what transpires.
The Raptor is going to have high intersection and cooling drag. Peter did a rather poor job there. Redoing most of FWR is needed anyway, so that would be the opportunity to fix those.
 
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