Raptor Composite Aircraft

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pictsidhe

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He wedged the tow bar against it to demonstrate he has around 1/2" of free play in the aileron control system. Which naturally is just fine.
Yeah, about that. I wouldn't want to fly an ultralight with 1/2" of play in the ailerons. Am I just being paranoid? Is it all just fine on a 300kt aircraft? I thought he was showing the (lack of) stiffness at first, then the true situation dawned on me.
 

flyboy2160

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Yeah, about that. I wouldn't want to fly an ultralight with 1/2" of play in the ailerons. Am I just being paranoid? Is it all just fine on a 300kt aircraft? I thought he was showing the (lack of) stiffness at first, then the true situation dawned on me.
Didn't you get Peter's memo? It's like the pitch on a prop: the faster you go, the less that deflection is in terms of an angle to the flight velocity. So, it's fine. :p
 

blane.c

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If there was that much play … I would not like it. When I move control I like the ailerons to move and when I don't move control I like ailerons to not move either.
 

BoKu

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Yeah, about that. I wouldn't want to fly an ultralight with 1/2" of play in the ailerons. Am I just being paranoid? Is it all just fine on a 300kt aircraft? I thought he was showing the (lack of) stiffness at first, then the true situation dawned on me.
I've flown a handful of loosey-goosey airplanes without problems. What scares me about this one is that the control circuits seem fairly limber, and the aileron deflection we see when Peter shakes the wings. Are the ailerons even mass balanced? They don't seem to act like it.

And, yes, speed definitely matters. The v^2 term in kinetic energy says that at 300kts there is four times the energy available to do mischief than at 150kts.
 

Jay Kempf

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Look at it as an optimist would. Loose ailerons at least if he doesn't push the speed will float up and increase washout. So at least that will prevent stall spin... He probably won't do maxV runs on the first hop.
 

flyboy2160

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What a joke. He keeps telling the Youtube True Believers that he's being oh so careful, but:
- he assembled his damper with just Blue Loctite - no safety wire!
- he didn't bother to spot weld the other belt flanges after having trouble with one.

If the test pilots see this stuff and still agree to fly, I have no sympathy if anything bad happens. None.
 

pictsidhe

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I've flown a handful of loosey-goosey airplanes without problems. What scares me about this one is that the control circuits seem fairly limber, and the aileron deflection we see when Peter shakes the wings. Are the ailerons even mass balanced? They don't seem to act like it.

And, yes, speed definitely matters. The v^2 term in kinetic energy says that at 300kts there is four times the energy available to do mischief than at 150kts.
The airplane has done what, taxied 10 miles? How does it already have that much play? Is it likely to get even worse?
Is the play between ailerons, or between ailerons and the yoke?
The trouble with borderline ailerons, is that when they become a problem, they can remove a wing...
 

Marc Zeitlin

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... I wouldn't want to fly an ultralight with 1/2" of play in the ailerons. Am I just being paranoid? Is it all just fine on a 300kt aircraft? I thought he was showing the (lack of) stiffness at first, then the true situation dawned on me.
So on the largest batch of canard aircraft I inspect (Variezes, Long-EZs, COZYs, Berkuts) all of which have torque tubes, belcranks and pushrods between the stick and the ailerons, I generally look for no more than +/- 1/16" of "play" in one aileron TE at the root end of the aileron when clamping the other aileron fixed. If it's more than +/- 3/32", I tell folks to start examining ALL of the places where play can exist and eliminate it. If there's more than +/- 3/16" of play, it's time to take the system apart and fix it. I've had customers with +/- 1/2" of play, and I tell them to ground the plane, and almost always they will find a loose bolt somewhere, or worn bushings, or dead rod-ends, or the like.

On Velocities that have ailerons that are teleflex cable actuated (they've gone away from that on the newer, higher speed aircraft) there can be more play - on the order of +/- 1/4" even when everything is right. I don't like the teleflex cable actuation for flight control surfaces, but there you are - I don't know of any flutter events on Velocities.

On the Raptor, unless I'm mistaken, the ailerons are cable driven. There's nothing intrinsically wrong with that if the system is very stiff (good support for all pulleys, etc.). I just completed (for a non-canardian project) aircraft system surveys on an ATR-42 and a Twin Otter, both of which have unboosted cable controls for their control surfaces. But the tension in their large diameter cable system is extremely high and the mounting for all cable pulleys is extremely stiff. There was very little play, if any, in the system, although I was not able to hold one aileron clamped and try to move the other, so I can't give a number.

All that for this. 1/2" of play at the TE is not acceptable _IMO_. Peter states that he's run it past Mark Bettosini (his engineer), who said it's OK. Difference of opinion, I suppose - it's certainly possible that when the ailerons float up under air loads, the play won't be meaningful - when they do their Vd testing/flutter testing (if they ever get that far) we'll find out. But play always lowers flutter margin and eliminating play on a new design would be prudent, IMO.

My GUESS is that the cable tension is way too low, and that the system mounting stiffness is way too low (reference the pulleys on the floor that were deforming the belly of the aircraft prior to stiffening - there are probably more areas like that leading to the play in the system, even after "fixing" the floor issue). Given that it takes almost no force to create the 1/2" of play at the TE, I'd say that the cable tension is too low, but increasing it will only stress/deform the pulley mounts, and still allow motion, albeit under load.

If nothing else, having that much play in the system leads to difficulties in control, as there will be a hysteresis band where the stick will need to move some amount before any control surface motion occurs. I had a friend back in college (1976 or so) who had a 1965 Mustang. It was a POS - the steering box was shot, and there was (I **** you not) 180 degrees of hysteresis in the steering wheel - you had to spin the wheel 180 degrees before anything would start moving left or right. So there was a LOT of steering wheel motion just to keep going straight. It was a fun car to watch him drive - I never tried to drive it. This almost certainly isn't anywhere near THAT bad, but it's a step in that direction, which is counterproductive.

My $0.02.
 

BBerson

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Play from wear in the control system is normally loose bolts or loose sloppy hinges moving back and forth. Play is felt with light finger shake. What he did in the video might be aileron twist from end to end or loose cables. But those are two different things.
It's hard to imagine how such a heavy carbon aircraft could be floppy.
 

flywheel1935

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I'm a little concerned with the re-drive. The belt moving out of center of the pulley is symptomatic of a bigger problem, not the ring falling off.
My thoughts too, these belts should and do track straight without 'flanges' in normal operation. While I admire Peters drive to build the Raptor some of the basic engineering
is lacking in finesse, the re-drive being a prime example.
I'm part way through a kit build by an 'amateur aircraft designer' and quite simply once built, will only be used to develop a 'proper' kit, using known aero techniques.
see LMA uk build, in Tube and Fabric section.
 

Voidhawk9

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It's heavy because of all the steel girders holding the important things together like, say, the variable geometry intake duct...
I hope you didn't miss that he changed to thicker steel for the revised nose gear arms last week...
 

Turd Ferguson

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Except for the EGT concerns which he still says are fine, even up to 1900-2000F! Apparently addressed by his sensor location.
"My sensor is at the Y pipe, not at the exit from the heads. Where the Y pipe converges cross sectional volume goes from 2 to about 1.5. That reduction in cross sectional area drives up the temperature at the sensor. So when it reports 1800f the temps coming out of the cylinders are likely closer to 1350f."

The explanation does seem to be tainted with with optimism. I would think it could be verified relatively easy; a temp stick from a welding shop is about $10.

If the probe reading is high because of a choke point in the exhaust, is that not going to be an issue in flight?
 

TarDevil

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"...
are likely closer to 1350f."
Seriously asking.... do any of you allow such guesswork in design work?

I can't imagine it being difficult to determine, with certainty, the actual EGTs. Regardless, I would not risk machinery or lives knowing this blowtorch is a few feet from the occupant portion of this vehicle.
 
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