Super Scooper Frise Aileron

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GESchwarz

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Because I am wanting to give my plane STOL performance, I must allocate a large percentage of the wing trailing edge to the flap, leaving only about 20% of the span for ailerons. Therefore my ailerons must be very effective. They did this on the Heilo Courier, but they used spoilers located just inboard of the ailerons, in order to assist the upward-deflected aileron in lowering the wing. At high AoA, the upward-deflecting aileron is nearly ineffective; most of the rolling force is provided by the downward-deflecting aileron on the other wing. However, at high AoA, the downward-deflecting aileron is very close to stalling. Therefore, using ailerons at high AoA often results in entry into a spin.

So, I thought that there must be a better way to get more authority out of the upward-deflecting aileron, so I designed the Super Scooper. See the three attached images. The idea behind it is that the leading edge of the upward-deflecting aileron, drops down into the high energy air under the wing, like a Junkers aileron, and as it does so, a slot begins to open on the top of the airfoil, opening a slot for air to be directed upward over the top of the aileron. This is essentially an inverted slotted flap.

When the aileron deflects downward, it moves much like a conventional aileron.

The only issue I see right now is that because the scooping action may cause the aileron to tug on my control stick, if I get to aggressive with the geometry, or rather, to big a bite out of that air under the wing. I could use springs to neutralize the forces, but I am thinking I may be able to balance the forces aerodynamically through experimentation.

There is one other potential problem, there is a pinch point as the leading edge of the aileron moves from the lowered position to the neutral position...there is potential for it to get jammed if a large bird gets ingested into the slot. A remote possibility that could be handled with rudder for roll control.

This design may well be spin proof, and effective with huge span flaps.

What do you think?
 

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Riggerrob

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I suspect that the tiny ailerons (Helio Courier) are primarily to provide feedback to the control stick, similar to the tiny ailerons Mitsubishi MU-2 and Nothrop Black Widow.
Also look into Lu (sp?) where they have full-span flaps, but the outer 30 percent are split. The upper, outer flap skin hinges up to provide roll control. I am not sure how effective Lu ailerons are at steep angles of attack?????
 

TFF

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Spoilerons are usually there to fix adverse yaw by equalizing the drag top to bottom of the aileron action. I would not build it unless you can wind tunnel your idea; at least not on a real plane.
 

Rick McWilliams

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I think that the extreme aft position of the hinge line will produce a reversed stick force. The odd nose shape will likely have very unusual stick force curve.
 

GESchwarz

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The reverse stick force is the most obvious issue, what I may do is move the axis point to reduce that, but I may be reducing the amount of slot and scoop. Compromises.

Flaperons or anything like them, meaning with spoilers, do not work well because you lose mobility...they are too close to stall to do much maneuvering. The best way to maintain control is to have a dedicated aileron.

Complexity? I eat complexity for breakfast. I love it. I don't see this design as being very complex at all.

What I believe is great about this design is that it gives a lot more authority to the upward-deflecting aileron.

I think building a near scale prototype of it and mount it outboard of my truck's bed, I could get some good data.
 

GESchwarz

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The North American RA-5 Vigilante has full span flaps and along with using the stabilators for roll control, it has this sort of slot, located forward of the outboard flaps, which scoops air from below the wing and sends it up to the top of the wing, the same way I am doing it here. I discovered that while examining one aboard the USS Midway museum. Studying other airplanes is a favorite activity of mine. It doesn't matter how many times I walk around an airplane, it seems that I continue to discover things I never noticed before.
 

GESchwarz

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Just by moving the axis of rotation about 2" toward the leading edge of the aileron I significantly reduce the inlet size, while maintaining the a large exit. A lesson can be learned from engine cooling aerodynamics...the key to maximizing flow is not by having a large intake, but rather a well designed outlet.
 

JamesG

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Of course you could just go with a full chord "tiperon"... It could slip with AoA there by avoiding the whole high angle separation issue and gives strong authority (at the cost of kind of a messy flow between them). It couldn't possibly more of a headache than a complicated clamshell frise aileron.
 

GESchwarz

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Rick, looks like we are neighbors. I am redesigning the aileron to with the axis closer to the leading edge. It already is looking more like a conventional frise. You mentioned that you didn't like the shape of the leading edge. What do think would be better? Traditional frise leading edges are pretty angular with a small radius.
 

GESchwarz

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Of course you could just go with a full chord "tiperon"... It could slip with AoA there by avoiding the whole high angle separation issue and gives strong authority (at the cost of kind of a messy flow between them). It couldn't possibly more of a headache than a complicated clamshell frise aileron.
I have never seen a "tiperon" on a successful design. However all moving stabilizers and fins are a similar sort, but generally only seen on supersonic aircraft. Not sure why not on subsonics. I did read recently that ailerons are more effective if kept away from the tip. I believe it has something to do with the counteracting influence of the tip vortex. Tail surfaces have much smaller vortexes.
 

RPM314

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However all moving stabilizers and fins are a similar sort, but generally only seen on supersonic aircraft. Not sure why not on subsonics.
It's because camber doesn't affect lift much as you go supersonic (and flaps essentially are variable camber).
 

GESchwarz

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I remember the wording for why I am doing this. At high AoA the up deflecting aileron has a fair amount of deadband. Forcing air from under the wing to the top of the wing takes out all of that deadband.
 

Tiger Tim

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similar to the tiny ailerons Mitsubishi MU-2
Nope no ailerons there, not even tiny ones. All Mitsubishi gives you is a couple springs for artificial feedback.

You can add the Cessna Caravan to the list of planes with small-ish ailerons and roll spoilers to help out.
 

JamesG

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I have never seen a "tiperon" on a successful design. However all moving stabilizers and fins are a similar sort, but generally only seen on supersonic aircraft. Not sure why not on subsonics.
Because it generally isn't needed on anything that isn't on the bleeding edge of performance or the flight envelope... the later of which is your intent, right?

I did read recently that ailerons are more effective if kept away from the tip. I believe it has something to do with the counteracting influence of the tip vortex. Tail surfaces have much smaller vortexes.
Neither do airfoils near Vmin, and at high AoA flow is a mess anyway.

But... my suggestion wasn't an attempt to derail, only to highlight the magnitude of the task you have set for yourself. It will be interesting to see your experimental results!
 

StarJar

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Because it generally isn't needed on anything that isn't on the bleeding edge of performance or the flight envelope... the later of which is your intent, right?



Neither do airfoils near Vmin, and at high AoA flow is a mess anyway.

But... my suggestion wasn't an attempt to derail, only to highlight the magnitude of the task you have set for yourself. It will be interesting to see your experimental results!
A full-cord tiperon would introduce a higher l.e. angle of attack, which would have very nasty effects compared to anything done with the trailing edge.
 

billyvray

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Curious: do you intend for the upper "spoiler" to be actuated up upon applying the aileron up? Or would the airflow from below be expected to force it open?
I'm guessing you would actuate it upward, but wanted to clarify.

Bill
 

Rick McWilliams

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Frise Aileron

The sharp nose Frise aileron is not my favorite. When the pivot point is too far aft the aileron will have a very lumpy force gradient that makes it want to stay in one of three positions. It feels terrible.

I like a larger nose and an aft hinge point with the pivot near the upper surface. A differential linkage is also used to give +18 to -28 degree motion. With luck a picture is attached.
 

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