UAV "pitcherons"
UAV "pitcherons"
(OP)
Hi All,
As an electronic engineer my knowledge on this subject is rather lacking, so apologies if this is a simple/ridiculous question:
I recently cane across some remote control models that had variable incidence wings, i.e. both the aileron and in some cases the elevator functions were achieved by twisting the entire wing. I realize on an aircraft large enough to be manned this sounds like a mechanical nightmare, but I was wondering... Given a smaller, lighter airframe where this is mechanically more feasible, would this or would this not be a more efficient way of achieving these control inputs?
I have looked around and seen a few people (in the RC community) doing this, but no discussions about the aerodynamic effects, is it that obvious or are people ignoring it because of the mechanical complexity? Anywho, If you guys are interested, have at it!
Thanks!
As an electronic engineer my knowledge on this subject is rather lacking, so apologies if this is a simple/ridiculous question:
I recently cane across some remote control models that had variable incidence wings, i.e. both the aileron and in some cases the elevator functions were achieved by twisting the entire wing. I realize on an aircraft large enough to be manned this sounds like a mechanical nightmare, but I was wondering... Given a smaller, lighter airframe where this is mechanically more feasible, would this or would this not be a more efficient way of achieving these control inputs?
I have looked around and seen a few people (in the RC community) doing this, but no discussions about the aerodynamic effects, is it that obvious or are people ignoring it because of the mechanical complexity? Anywho, If you guys are interested, have at it!
Thanks!





RE: UAV "pitcherons"
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RE: UAV "pitcherons"
sorry if I wasn't clear.
RE: UAV "pitcherons"
RE: UAV "pitcherons"
For planes that are light, I think it's still a novelty item. What's the performance gain, or is there even any performance gain. Pitching the wings kills the lift, so why is that a good thing? While the plane might be able to snap roll faster, moving all that mass winds up slowing down everything down.
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RE: UAV "pitcherons"
The performance gain as my flawed model of the world sees is; with ailerons, during the rolling motion the apparent direction of the airflow is not lined up with the wing. e.g with a downward deflection of the aileron increasing lift, as the wing starts to rise, the apparent airflow changes to decrease the AOA as the wings velocity around the fuselage increases. With a pitcheron, I believe this is less of an issue, the issue is still there as the wingtip would have a different velocity and therefore a different apparent AOA than the root, but to fix that we need wing warping...
RE: UAV "pitcherons"
One model plane I like mounts the motors on pitch gimbals. Differential thrust produces yaw, differential motor pitch produces roll. I guess if you want pitch control you still need an elevator.
A pitcheron vs aileron still has the same AoA change during the roll maneuver. The main difference is the degree of control response for a certain amount of control surface deflection. Essentially a pitcheron is a wing consisting only of the aileron; not a separate case.
**Full-flying stabilizers are used on fighter aircraft and a number of them are differential.
RE: UAV "pitcherons"
The XF-91 Thunderceptor was designed with a variable incidence wing which could be adjusted in flight. Just one of several interesting design features of that aircraft.
Keep em' Flying
"I intend to live forever, or die trying" - Groucho Marx
RE: UAV "pitcherons"
"A pitcheron vs aileron still has the same AoA change during the roll maneuver. The main difference is the degree of control response for a certain amount of control surface deflection. Essentially a pitcheron is a wing consisting only of the aileron; not a separate case."
Is it not true that in the case of the aileron, the "fixed" part of the wing is working against the aileron when the aileron is deflected and the wing is rising/falling? or does the wing never rise/fall fast enough to have a noticeable effect on the apparent AoA?
Any thoughts on, disregarding the mechanical stuff for the moment, whether this is a more efficient way to achieve roll control for an aircraft?
RE: UAV "pitcherons"
The angle of attack of the pitcheron tends towards zero. When it doesn't it develops lift and causes the roll rate to increase until the AoA is zero.
Taken as a whole, the wing section with the aileron is changing the camber of the airfoil, which changes it's angle of attack. Like the pitcheron the AoA will tend towards zero, until there is no lift acting to increase the roll rate.
Since AoA change will be proportional to span for a given roll rate, changing the AoA by changing the camber towards the wing tips allows the maximum camber change where the maximum AoA change is needed. The inboard part of the wing has much less AoA change required; increasing the AoA of the inboard section to match that at the wing tips just increases the drag without influencing the roll rate much.
The ideal would be to twist the wing, but that's been elusive for practical airplanes.
A complicating factor for level flight is that both wings are at a comparable AoA, which also means they are producing comparable induced drag. When there is a roll input, one wing will be at a higher AoA than the other, and produce more induced drag. This produces an adverse yaw, which the Wright brothers noticed. The plane would roll one way, but the nose would turn the other, requiring the development of the moveable rudder and with it, the coordinated turn. In large aircraft spoilers are often used on the wing that should roll down. Not only does this tend to accomplish the same thing as aileron, it doesn't result in adverse yaw.
I just looked at the XF-91 Thunderceptor. Can't unsee that one. The entire wing was adjustable; or rather the fuselage had a variable incidence setting as the AoA of the wing is, for any flying condition, fixed. The articles indicate the wing incidence was changed for landing/takeoff, which really means not having to rotate the fuselage and scrape the tail. F-8 Crusader also, and a much prettier plane.
RE: UAV "pitcherons"
But in all seriousness, I'm sure it was well engineered for testing. It was an intriguing choice. I just like to poke fun at it because it's so bizarre in appearance.
Keep em' Flying
"I intend to live forever, or die trying" - Groucho Marx
RE: UAV "pitcherons"
OMG Spratt Control Wing
http://www.homebuiltairplanes.com/forums/attachmen...
RE: UAV "pitcherons"
Right, but with ailerons, when the AoA gets to zero (during a roll), you have a wonky airfoil, right? is that a good thing?
With pitcherons, at least at some point allong the span, you will have what you started with before the roll. i.e. zero AoA and the same section.
Also, seeing as you mentioned twisting wings (as in the tip having more of a change in angle that the root) would this not cause considerably worse induced drag related yaw problems at the start of the rotation?
Would the ideal not be: pitcherons/ailerons to start the roll, then as the speed of the roll increases, add some "twist" to keep the AoA of all parts of the wing equally positive/negative with respect to the airflow? Maybe not equally... Insert better lift distribution here :)
Thanks for your replies, really appreciate the input. Learning a lot here!
RE: UAV "pitcherons"
With pitcherons, at the start of the roll the entire wing lift coefficient changes. With ailerons only a small part of the wing changes, with a lower induced drag penalty.
Were pitcherons an overall good idea, given the number of variations people have put into flight, they would have bubbled to the top by now. Some ideas, like flying wings or tilt-rotor craft hang on by tenuous threads where aerodynamic performance is second in importance to some other consideration. Pitcherons are even lower in utility than those. Other oddities - VTO aircraft like Pogo; parasitic fighters like the Goblin; jet and rocket propelled rotor helicopters. All interesting, but mostly impractical. Still it's interesting to look at what makes them second best on the off chance they could be useful. Though now that I think on it, they are used as the main means for adjusting lift in helicopters, but helicopters can't adjust the rotor angle of attack by altering the fuselage angle of attack and therefore change the amount of lift- so there's no choice there.
RE: UAV "pitcherons"
RE: UAV "pitcherons"
Thanks again!
RE: UAV "pitcherons"
As alluded to above I suspect issues with structural efficiency & possible control sensitivity would make doing this with the main wing tricky for many applications.
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RE: UAV "pitcherons"
Thanks
RE: UAV "pitcherons"
RE: UAV "pitcherons"
The sprat Control wing aircraft designed in the 1930s seems to be what you are talking about in your original post.
B.E.
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