Floating aileron

[Sparky Paul]

Just got the DVD from the 2005 SAE Aerodesign West at Fort Worth.
The usual collection of unflyables, structural poor and amazing planes.
One plane had something occur inflight we'd all like to see (on someone else's plane, of coursr).. the left aileron servo fell off the wing, but remained attached to the aileron.
The expected situation would be the weight of the servo would pull the aileron down.. the pilot mentioned after the crash that he saw the servo dangling, and had problems with the plane.
On the DVD, the aileron ISN"T pulled down by the servo's weight, but in actuality floats up a considerable amount. (Can't get a usable screen print of the event.)
What this does to the plane is seriously reduce the amount of lift from that portion of the wing, so the unbalance would be rolling towards the upfloated surface, while the drag on that upfloated side is reduced a lot, resulting in an opposite roll towards the "normal" side.. the combined effect was apparently not all that bad watching the plane continue on down to the crash, which was more due to landing too fast and hard off the runway.
With the airfoil used (looks like a Selig 1223), the change in Cl and Cd with the upfloated surface is probably large...
The DVD is available from teamrcpilot.com

[biber]

That huge upfloating forces on flaps of high lift rated airfoils are a serious issue. They require strong servos and it´s hard to get the flaps torsional stiff since them beeing so thin. The FX 63-137 has caused fullsized aircraft manufacturers some trouble, due to this.

biber

[Sparky Paul]

Some of the earliest airplanes had ailerons that hung down until the plane got some airspeed.. the ailerons would float up until restrained by the cable to the control column.
If the aileron on that SAE plane had been able to transfer the load on it to the airplane, the plane would have done a uncontrolled left roll. It appeared to fly level instead, tending to go to the right.