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Raptor Composite Aircraft

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Hot Wings

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That last flight didn't look so bad - until I saw the cockpit view. The low frequency roll response looked to me to be divergent and pretty well matched to what we can see of the motion of the left aileron.
The higher frequency aileron 'flutter' seen in the stick starting about 13:58 doesn't look, to me, to have any relationship to the aileron motion from the exterior view?
 

BBerson

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I looked at the video again and he is doing those roll motions with his hand. The yaw might be adverse yaw from the quick roll inputs. Needs a bit of rudder with the roll jabs, perhaps.
 

pictsidhe

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To use non technical language, it looked drunk! Hard to believe all those commentators praising its stability weren't too... He's a **** fool not to get someone with canard experience to fly it. Unfortunately, he didn't like all the demands Wasabi were making before they would try.

One of the comments deleted from the 2nd ground effect video was one of Peter's. He explained how he needed to pull back on the stick until the nose rose, then the stick forces reverse and he has to push. That screams unstable to me. Perhaps another 100lb of lead in the nose would help, if there is any room left.
 

BJC

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lelievre12

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wsimpso1

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The stick had a vibration in the roll axis. There is the big roll input needed to the left to make it go straight. That is two things that need a root cause found and fixed before committing to flight again...
 

pictsidhe

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The stick had a vibration in the roll axis. There is the big roll input needed to the left to make it go straight. That is two things that need a root cause found and fixed before committing to flight again...
I wonder what the natural frequency of the aileron circuit is. Those are honking big weights hung on the spades and I don't think the control circuits ever got very stiff. With some design details of the ailerons and a compliance measurement, that is not hard to ballpark. Far harder to do by guesswork from videos...
 

TFF

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Wasabi learned their aircraft was uncontrollable with one engine out. Everyone under the same circumstance would have crashed. They might have been able to save it if they could have cut the running engine in a safe place.
 

Speedboat100

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Wasabi learned their aircraft was uncontrollable with one engine out. Everyone under the same circumstance would have crashed. They might have been able to save it if they could have cut the running engine in a safe place.

Wouldn't it be useful to testfly the prototype then with just one engine on it ? At least a model ?

Angel had very large fin on theirs.

Angel_Aircraft_Corporation_Model_44_Angel.jpg
 

hammer

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I just had a look at the latest video. This gives us a bit more information for the horsepower calculation.

Look at the cockpit view starting at around 12 minutes

At 12:09 he is rolling about 7kts and the engine is at full power.
At 12:29 (20s) he is at 71kts
At 12:39 (30s) he is at 90kts

We can correlate this with distance. Rwy 35 is almost exactly 8000' long

He passes the 7K marker at about 12:23 and 53kts
6K marker at 12:31 and 76kts
5K marker at 12:38 and 88kts

(over 3k' to get airborne)
 

Scheny

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Two engined aircraft are mostly limited by Vmca (minimum control airspeed) rather than stall speed. They will tend to stall at incredibly low stall speeds, but if an engine fails below Vmca, the only chance is to remove power or it will spin immediately. It is so dangerous, that it is the only thing I have not trained in my DA42... Stalls? No problem, go for it. Have done it multiple times.

As for his flight: The vertical stability looks not too bad to me. The high required pitch to "unstick" the plane seems in line with CoG vs. flight surfaces and it stays at altitude with around center stick.

But the vibrations on the aileron input cause my alert bells to ring too.
 

rbarnes

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I looked at the video again and he is doing those roll motions with his hand. The yaw might be adverse yaw from the quick roll inputs. Needs a bit of rudder with the roll jabs, perhaps.
If he would take up Velocity on their offer for flight training PM would know that winglet canards yaw before they roll and that most roll control is started and finished with your feet and not your hand... as explained by Paul B in his Velocity training article.
 

BBerson

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Could be similar to Velocity. I wonder if the ailerons have differential?
Also thinking I might prefer the fins at the wing root like Jeff did on Orion. Not sure, but I think fins at wing root can be larger and more effective. And structurally easier. The Velocity/Raptor types have less sweep than Rutan. So tips are not that far aft.
 

TFF

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Speedboat, the necessity of testing is relative. I’m sure they would have tested it during a controlled test, found out there was a problem and modified their aircraft. Just so happens they didn’t get that far and had to ride it out. Conditions were not on their side either with the wind.

Building an RC may or may not have shown the problem as they surely were not going to build an RC model that was going to cost more than the prototype to be perfectly Scaled accurate, or if it happened to a model do you chalk it up to being an RC model or actual issue, or does an inaccurate model mask it?

Wasabi didn’t design an airplane, they added engines to a design that they hoped would make a nice calling card. I don’t think they thought they were testing engine reliability conditions. They definitely would have picked a different airplane for that.
 

Volzalum

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I guess PM could hang a BOM on a wing and get airspeed from it instead of trying to rely on the questionable static on the Raptor.
 

TFF

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I have seen some BOM YouTube commercials, they might be trying to avoid this one. I have some friends that have one. Put it on an Aerostar and then a Cirrus.
 

Doggzilla

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One of the comments deleted from the 2nd ground effect video was one of Peter's. He explained how he needed to pull back on the stick until the nose rose, then the stick forces reverse and he has to push. That screams unstable to me. Perhaps another 100lb of lead in the nose would help, if there is any room left.
That is the divergence I have been talking about.

Now that it’s been confirmed by his own comment it needs to be taken more seriously.

The problem is not entirely from the elevator. The same elevator is only mildly dangerous on the Rutan, but the Raptor has a far wider fuselage, which adds surface area ahead of the CG.

This might not make sense at first glance, but consider the moment arm and it becomes much more obvious. The moment arm of the canard and forward fuselage is probably 10-12 times higher than the main wing and rear fuselage because they are very close to the CG.

That much longer moment arm gives the canard and nose area a disproportionate effect on stability or instability.
 

Turd Ferguson

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One of the comments deleted from the 2nd ground effect video was one of Peter's. He explained how he needed to pull back on the stick until the nose rose, then the stick forces reverse and he has to push. That screams unstable to me.
That's true of a lot of planes and does not necessarily indicate divergence. PM does not know what he is describing.
 

Wild Bill

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One of the comments deleted from the 2nd ground effect video was one of Peter's. He explained how he needed to pull back on the stick until the nose rose, then the stick forces reverse and he has to push. That screams unstable to me. Perhaps another 100lb of lead in the nose would help, if there is any room left.
It doesn’t look dangerously unstable. The abrupt pitch up on rotation is somewhat canard typical. Especially with a relatively high rotation speed.
He’s probably not comfortable with doing it yet.. But with some time he will learn to rotate and get the nose up at a lower speed.
If you do that you can fly it down the runway only on the main gear. As speed increases it just flies off without the abrupt pitch up.

As for what appears to be vibration on the stick in the roll axis.. Could that be Peter just simply being tense on the controls?
 
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