Raptor Aircraft

Even certified electronics (like EFIS and GPS NAVCOM) have glitches from time to time. I don’t trust engine ECUs unless they’ve been thoroughly tested (like major manufacturers’ daily drivers). I have experience tuning aftermarket automotive EFI system and I would never trust myself to not have effed up a tune or trust in an aftermarket piece of engineering that is not already mass produced for millions of miles of service (aftermarket ECUs are good for hobbies, not life/death).

As for flutter, can wind-tunnel testing predict some of that?

And why one would experiment with a new airframe design and power plant with so many other variables (gear function), is lost on me. Like someone earlier said - run an Audi with your setup (redrive, ECU) on a proven airframe, and a Lyco, TCM, or Rotax on this contraption. Leave the gear fixed for now.

Sneak up on the combo, don’t kamikaze it.

Also, looking at the Wasabi clip where he apparently glued the visual separation at the wing trailing edge- how does a test pilot get a feel for the quality of the composite work if you can’t see the inside or witness the build? Wasn’t there a recent fatal in-flight loss of wing on a composite experimental, turbine maybe, from an experienced builder? How could I strap myself into such an unknown without being drunk or having a terminal disease? That’s too much faith in another human.
 
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3393RP said:
This is a damning indictment of Peter's lack of knowledge, and a perfect example of how he routinely ignores well founded criticism of the aircraft's design and execution.

https://www.homebuiltairplanes.com/forums/threads/raptor-composite-aircraft.24721/post-547398
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Did peter not use the stock Audi turbo setup? Why would the car engine with those turbos work fine, yet an airplane would suffer "exhaust valve stress" and other breathless calamities?

I like HBA but I'm not understanding the grievance. If Raptor-guy did his own turbo setup, that would make sense to me, but I haven't seen that he did that?

(I know nothing about turbos, little about raptors, but I enjoy armchair quarterbacking immensely :) )
 
schmookeeg said:
Did peter not use the stock Audi turbo setup? Why would the car engine with those turbos work fine, yet an airplane would suffer "exhaust valve stress" and other breathless calamities?

I like HBA but I'm not understanding the grievance. If Raptor-guy did his own turbo setup, that would make sense to me, but I haven't seen that he did that?

(I know nothing about turbos, little about raptors, but I enjoy armchair quarterbacking immensely :) )
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It doesn't appear he deviated from stock turbos. The audi vw "bi/twin" turbo is esentially a "twin scroll" as used by BMW and Subaru.

It esentially uses exhaust gasses to spin a small turbine to allow for faster spool for your intake side turbine.
 
That's what I thought. BMW did this as well (*edit* as you already mentioned). It's a proven system for its intended use. No clue about this use case.
 
schmookeeg said:
Did peter not use the stock Audi turbo setup? Why would the car engine with those turbos work fine, yet an airplane would suffer "exhaust valve stress" and other breathless calamities?
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The problem with most car engine conversions is that car engines are not built to deliver 65-75% of their power 95% of the time like aircraft engines do. Depending on how they are driven, some cars may never even see 75% power. The majority of the time is spent at idle or around 25-35% power or less while cruising. It is like taking a square peg and trying to drive it through a round hole. There is a reason engines are engineered for the job they are being built for.
 
midwestpa24 said:
The problem with most car engine conversions is that car engines are not built to deliver 65-75% of their power 95% of the time like aircraft engines do. Depending on how they are driven, some cars may never even see 75% power. The majority of the time is spent at idle or around 25-35% power or less while cruising. It is like taking a square peg and trying to drive it through a round hole. There is a reason engines are engineered for the job they are being built for.
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Sure. So is the HBA thread claiming, then, than this Audi TDI will melt its exhaust valves once hitting (75%? 100%?) power? I don't see why the compound turbo here is at fault, I think ANY car engine suffers from "can't do 100% duty cycles" problem. The HBA post seemed to suggest the turbos were badly matched/engineered, which seems like, frankly, nonsense.
 
schmookeeg said:
Sure. So is the HBA thread claiming, then, than this Audi TDI will melt its exhaust valves once hitting (75%? 100%?) power? I don't see why the compound turbo here is at fault, I think ANY car engine suffers from "can't do 100% duty cycles" problem. The HBA post seemed to suggest the turbos were badly matched/engineered, which seems like, frankly, nonsense.
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Didn't read much into the HBA thread, but I'm not sure I've seen sequential turbos in aircraft. Usually a twin turbo aircraft is using two distinct turbos, one to drive each bank of cylinders. I'd guess part of the issue is heat. Turbos can create a lot of extra back pressure and heat on the exhaust side of an engine, and heat management is critical.
 
midwestpa24 said:
Didn't read much into the HBA thread, but I'm not sure I've seen sequential turbos in aircraft. Usually a twin turbo aircraft is using two distinct turbos, one to drive each bank of cylinders. I'd guess part of the issue is heat. Turbos can create a lot of extra back pressure and heat on the exhaust side of an engine, and heat management is critical.
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Sequential turbos are not appropriate for most aircraft. The main idea of sequential turbos is reduced turbo lag. Not an issue in an aircraft, but significant for performance auto's.
 
schmookeeg said:
The HBA post seemed to suggest the turbos were badly matched/engineered, which seems like, frankly, nonsense.
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Thats what I was getting at with my post. They're great for their intended use, but I can see how they would do terribly for this use as their designed goal is completely negated here.
 
jaxcessnadriver said:
I was curious about the compound turbo setup and it appears this was a VAG/Audi choice from the factory

https://www.audi-technology-portal.de/en/drivetrain/tdi-engines/3.0-tdi-biturbo_en
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Peter is not using those pieces that were engineered to operate in a compound configuration. He chose two large turbos from a Summit Racing catalogue and bolted them onto the engine. They are not the proper size for compound use, and the second turbo is making huge backpressure that results in an EGT that will melt the exhaust valves, and the compressor side is operating near or at the surge limit.

Apparently he doesn't have good instrumentation of the EGT at the exhaust manifold, or pressure and temperature information at each turbocharger.
 
jaxcessnadriver said:
It doesn't appear he deviated from stock turbos. The audi vw "bi/twin" turbo is esentially a "twin scroll" as used by BMW and Subaru.

It esentially uses exhaust gasses to spin a small turbine to allow for faster spool for your intake side turbine.
Click to expand...

schmookeeg said:
Did peter not use the stock Audi turbo setup? Why would the car engine with those turbos work fine, yet an airplane would suffer "exhaust valve stress" and other breathless calamities?

I like HBA but I'm not understanding the grievance. If Raptor-guy did his own turbo setup, that would make sense to me, but I haven't seen that he did that?

(I know nothing about turbos, little about raptors, but I enjoy armchair quarterbacking immensely :) )
Click to expand...

Sierra_Hotel said:
That's what I thought. BMW did this as well (*edit* as you already mentioned). It's a proven system for its intended use. No clue about this use case.
Click to expand...

schmookeeg said:
Sure. So is the HBA thread claiming, then, than this Audi TDI will melt its exhaust valves once hitting (75%? 100%?) power? I don't see why the compound turbo here is at fault, I think ANY car engine suffers from "can't do 100% duty cycles" problem. The HBA post seemed to suggest the turbos were badly matched/engineered, which seems like, frankly, nonsense.
Click to expand...

Not nonsense. They aren't stock parts, they are two large Garrett turbos almost identical in size. That goes against the most basic engineering precepts. Peter made the selection, apparently after watching YouTube videos and researching hot rodder websites. The ECU doesn't even know the turbos are on the engine.

I wouldn't have posted the link to HBA if the turbochargers were an OEM setup. Did you guys even bother to read it?
 
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3393RP said:
Not nonsense. They aren't stock parts, they are two large Garrett turbos almost identical in size. That goes against the most basic engineering precepts. Peter made the selection, apparently after watching YouTube videos and researching hot rodder websites. The ECU doesn't even know the turbos are on the engine.

I wouldn't have posted the link to HBA if the turbochargers were an OEM setup. Did you guys even bother to read it?
Click to expand...

Just watched "Turbos Meet at Last."

Yeah you aren't kidding those are massive turbos compound setup. Probably putting out enough heat to melt your face off lol.
 
You guys are very familiar with my frustration with the current crop of GA engines, and welcome whatever technology we can borrow from automotive engines..

However, his Audi set up to me was dubious from the get-go..

If this guy at least put a Lyco or Conti he would at least be able to tackle one thing at a time and consider power plant stuff at a later date.. it would be a good idea to take his engine and put it on a test stand and run it through a programmed loop of hundreds of hours of operation

He has accidentally discovered many issues with it just taxiing around an airport..
 
455 Bravo Uniform said:
Even certified electronics (like EFIS and GPS NAVCOM) have glitches from time to time. I don’t trust engine ECUs unless they’ve been thoroughly tested (like major manufacturers’ daily drivers). I have experience tuning aftermarket automotive EFI system and I would never trust myself to not have effed up a tune or trust in an aftermarket piece of engineering that is not already mass produced for millions of miles of service (aftermarket ECUs are good for hobbies, not life/death).

As for flutter, can wind-tunnel testing predict some of that?

And why one would experiment with a new airframe design and power plant with so many other variables (gear function), is lost on me. Like someone earlier said - run an Audi with your setup (redrive, ECU) on a proven airframe, and a Lyco, TCM, or Rotax on this contraption. Leave the gear fixed for now.

Sneak up on the combo, don’t kamikaze it.

Also, looking at the Wasabi clip where he apparently glued the visual separation at the wing trailing edge- how does a test pilot get a feel for the quality of the composite work if you can’t see the inside or witness the build? Wasn’t there a recent fatal in-flight loss of wing on a composite experimental, turbine maybe, from an experienced builder? How could I strap myself into such an unknown without being drunk or having a terminal disease? That’s too much faith in another human.
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His cavalier attitude towards the delamination of that area really sums up his apparent attitude of “how dare you criticize my plane” instead of “thanks for catching that...let’s look deeper to verify there’s nothing hiding that we can’t see.”

It is abundantly clear that he has a severe case of “get there-itis” on this project, and doesn’t want to hear anything that results in delays. Bad, bad attitude to have with this airplane.

If I were a prospective test pilot, I would never be able to get past the iceberg principle.
 
Finally some good news!

50239248632_74dc1ae097_z.jpg
 
You guys see the video he posted today? "That amount of shimmy is totally acceptable.. given that it's a castering nose wheel it's going to do that" <- I have never seen a Tiger or Cirrus nose wheel shake like that, but I guess the engineers at Grumman and Cirrus weren't up to the caliber of Raptor

 
Tantalum said:
You guys see the video he posted today? "That amount of shimmy is totally acceptable.. given that it's a castering nose wheel it's going to do that" <- I have never seen a Tiger or Cirrus nose wheel shake like that, but I guess the engineers at Grumman and Cirrus weren't up to the caliber of Raptor

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A castering nose wheel will shimmy like that, or worse if there isn’t proper tension. Had it happen on my Grumman when it came out of annual once and the mech didn’t put any friction (18 lbs required) on the nut. So loud that the guys in the FBO heard the shudder!
 
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This thing is going to end up a smoking crater in the ground. All his responses to defects are "It's fine". No, they're not fine and your normalization of deviance and anti-authority attitudes are going to kill you if you fly it.
 
It’s getting to be more than a bit odd. It’s almost like it’s intentional.
 
Velocity173 said:
A castering nose wheel will shimmy like that, or worse if there isn’t proper tension. Had it happen on my Grumman when it came out of annual once and the mech didn’t put any friction (18 lbs required) on the nut. So loud that the guys in the FBO heard the shudder!
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I had noticed the shimmy in the video from last week too. Almost looked like the wheel was loose on the axle.

Also interesting in the new video the difference in ground speed versus indicated air speed, and how the altimeter fluctuates 60-80 feet depending on power setting.
 
midwestpa24 said:
I had noticed the shimmy in the video from last week too. Almost looked like the wheel was loose on the axle.

Also interesting in the new video the difference in ground speed versus indicated air speed, and how the altimeter fluctuates 60-80 feet depending on power setting.
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Can you imagine you have to do a go around and you go full power and all of a sudden your altimeter says you gained 500 ft

The Wasabi guys questioned why he wasn't using the integrated static in the pitot on the canard and instead went with the static port infront of the prop.
 
One question I have, although not unique to the Raptor, is how far can you pitch up before striking the prop? The canard design has always left me wondering if any have ever suffered a prop strike either on rotation or in the flare.
 
midwestpa24 said:
I had noticed the shimmy in the video from last week too. Almost looked like the wheel was loose on the axle.

Also interesting in the new video the difference in ground speed versus indicated air speed, and how the altimeter fluctuates 60-80 feet depending on power setting.
Click to expand...
The altitude went as high as 330 that I saw. Field elevation is 203. The static port is basically being pulled 0.13” below ambient pressure by the propeller, movement of the airframe through the air, or a combination of the two. That probably contributes to the drastic airspeed error. (Top wind yesterday morning was 7 mph, not even half of the error between the panel’s calculated TAS of 94 knots and GPS GS of 58.)
 
Tantalum said:
Can you imagine you have to do a go around and you go full power and all of a sudden your altimeter says you gained 500 ft

The Wasabi guys questioned why he wasn't using the integrated static in the pitot on the canard and instead went with the static port infront of the prop.
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What pitot has an integrated static port? The Garmin GAP 26 has pitot and AOA plumbing and that is the model I would have expected to see on the Garmin-infused Raptor.
 
midwestpa24 said:
One question I have, although not unique to the Raptor, is how far can you pitch up before striking the prop? The canard design has always left me wondering if any have ever suffered a prop strike either on rotation or in the flare.
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A "well designed" machine I assume would be such that with not enough airspeed the canard won't work, and once there's enough speed once the canard lifts the nose the whole plane lifts off.. I imagine. I assume that's how the Long EZ and Velocity are setup (though I could be wrong)

In Peter's case, he did a video, maybe a year ago (??) where he took a tape measure and measured the distance from the prop to the ground and said "I think it's fine" <- this was based on some user comments from a prior video.
 
iamtheari said:
What pitot has an integrated static port?
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The Piper PA28 does.. it's a blade with holes on the bottom (static), back (drain) and front (pitot).

upload_2020-8-19_13-49-53.png

The Wasabi guys apparently observed that the pitot he has in the front on the canard has an integrated static port but that it wasn't in use.

I actually really like the Piper setup. Although static ports generally don't ice up I like knowing that as well is also heated
 
Tantalum said:
In Peter's case, he did a video, maybe a year ago (??) where he took a tape measure and measured the distance from the prop to the ground and said "I think it's fine" <- this was based on some user comments from a prior video.
Click to expand...

That prop is toast on the first firm landing where the pilot tries (late) to correct with pitch. Between pitch angle, tire flex, and gear flex that prop is hitting asphalt or concrete.
 
midwestpa24 said:
One question I have, although not unique to the Raptor, is how far can you pitch up before striking the prop? The canard design has always left me wondering if any have ever suffered a prop strike either on rotation or in the flare.
Click to expand...

The Rutan canards have zero issues with takeoff/landing prop strikes. Different story if you exit the plane after parking with the nosewheel still extended.....
 
Kenny Phillips said:
I'm torn between "awesome plane" and "terrible shooting".
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Looking at the patch sizes... many of the them look like 20mm cannon holes. 20mm is more violent and hard hitting then .30 cal machine guns. I remember seeing interviews with WW2 veterans talking about the distinctive sound of 20mm verses .30 cal striking the air frame.

.30 cal puts a hole in an air frame rib, 20mm rips it in two.
 
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Tantalum said:
A "well designed" machine I assume would be such that with not enough airspeed the canard won't work, and once there's enough speed once the canard lifts the nose the whole plane lifts off.. I imagine. I assume that's how the Long EZ and Velocity are setup (though I could be wrong)
Click to expand...

You're right. At least as far as the Velocity is concerned. I suppose if you held it down and got enough airspeed and then really yanked the stick back you could get a prop strike. But you would have to try really hard to make that happen.
 
donjohnston said:
You're right. At least as far as the Velocity is concerned. I suppose if you held it down and got enough airspeed and then really yanked the stick back you could get a prop strike. But you would have to try really hard to make that happen.
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<-------Note - Zero Canard Experience

What about on landing? Is it possible to over-flare trying to grease it on and prop strike? Or is that aerodynamically impossible? Just a training issue?
 
Just like on the takeoff, it's not impossible, just very unlikely.

You don't flare a canard aircraft during landing. You literally fly it onto the ground. And the canard has to be flying (not stalled) until the mains are on the ground. And to make a nice smooth landing, the nose should be on the ground before you're slow enough for the canard to stall.

If the mains are not on the ground before the canard stalls, you're going to have a bad day.
 
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