Control Surfaces/Floater

[jptonks]

Hello all,

I am considering the various possibilities of stopping a floater (high wing) from floating. In other words, how to kill the lift 4-6 inches above the runway when landing without decreasing the engine idle any lower.

The airplane in question is under construction but everyone knows from prior experience that it is a floater. The plane will have flaps and will be flown with a computer radio. We're pretty well locked into a certain engine size and type of propeller (budget restrictions).

Obviously, we could wait until the flying season comes around and just experiement with everything that we can think of. But we are anxious for information that might be of help.

We have considered lowering the flaps more than usual down to almost 80 degrees, but we have also considered putting the flaps up. Flaps up has effect of reducing drag while reducing lift. Not sure here which of the opposing factors will dominate. Maybe a flaperon function on the ailerons just before touch down. Or even a crow mix.

Any thoughts would be appreciated.

John T.

[jkettu]

You will want to add drag. Since you already have both flaps and ailerons, the easiest and most efficient solution would be to use crow (flaps down, ailerons up).

Another way would be to use lots (70 - 90 deg) of flap, but then you would need to be prepared to compensate for ballooning during flap extension. Once the flaps are down and the plane settled into the new equilibrium, there should be no trim problems.

Lots of flap up (used as spoilers) would add drag but not do anything to reduce stall/approach/landing speed

Both ailerons down (flaperons) at low speed should be avoided due to risk of tip stalling

Whatever you decide to do, be prepared to push the nose well down to maintain airspeed when drag devices are in use.

[biber]

In order to kill lift and add to the drag, you could use spoilers or SH airbrakes on the top of the wing.
That's what the quite floaty full size gliders do.

Another thing would be pivoting trailing edge airbrakes which are about neutral to lift, but can produce huge amounts of drag.

biber