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Experimental Aircraft Control Concept: Raked Swing-Wingtip

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REVAN

Well-Known Member
Joined
Dec 6, 2016
Messages
605
Location
Tucson, Arizona USA
I'm spinning off this new thread from the thread Anti-Spin Ideas - http://www.homebuiltairplanes.com/forums/showthread.php?t=27801

There, I had proposed the concept of using a wing design that replaces the standard aileron with an outboard raked swing-wingtip that would trade sweep and polyhedral for span, area and washout angle. I drew this concept on a Sportsman. The question here is to gather ideas for what would be the best aircraft choices for a testbed on which to test an idea like this. The second goal is to reach out to see if anyone is working on a project for one of these candidate aircraft that may be interested in incorporating this in their project to demonstrate efficacy.

This quote from the other thread is brief summary of the concept.

A Hershey Bar wing modified with a raked swing-wing tip as was described in the pdf file posted earlier may be completely yaw stable, exhibiting proverse yaw characteristics. While the fuselage will still need a vertical stabilizer to make the fuselage yaw stable, a wing as described here may remove the need for a rudder.


Neutral control position:
View attachment 62910


Left turn control deflection:
View attachment 62911


Right turn deflection:
View attachment 62912


Superposition:
View attachment 62913


Superposition from the front:
View attachment 62914


What's good about this type of concept is that when raising a wing to turn, the wing tip swings forward. When this happens the tip speed increases, and the span increases. With a higher 'q' and a more efficient span loading than the other wing, it will both climb and accelerate, affecting a coordinated roll and yaw without the need for any rudder input from the pilot. This is the desired control behavior for a wing to have.

I believe a wing of this design should exhibit proverse yaw characteristics in normal flight. Furthermore, in a stall, the pilot should be able to fly the plane with the stick the same as when the plane is not stalled (i.e. - stick left to lower left wing, stick right to lower right wing). The benefit being that the pilot does not need to recognize the wing is stalling and mentally change from stick control to rudder control to prevent spinning the plane. One control law for the pilot simplifies task loading and reduces the chances for pilot error contributing to an aircraft loss of control.
 
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