Flap

[Htin Aung]

Hi When you put flaps down, do you need to put elevator up or elevator down to compensate the increase lift from the flaps.What will happen to the nose of the aeroplane, will it go up or go down due to increase lift from the main wing? Need to increase the throttle slightly to compensate the drag from the flap.But I am not sure whether I need to give a bit of elevator up or elevator down. I could test it with a small amount of flap down at height to test the water. I would like to know the aerodynamic explanation. Thanks.

[Mike Rolls]

It depends upon the aircraft. Some will pitch nose up, some will pitch nose down, some will not pitch at all.
Only way to be sure, as opposed to theorising, is to try it.
Mike

[Htin Aung]

Hi Mike, Thanks. You are right. I have tested with Piper J3 Cub high wing plane with OS52 four stroke engine. I did not notice anything different.It takes longer run way to take off due to drag. It slows down the plane.I would like to try on VMAR Jodel400 60 size low wing scale plane.It would be nice if I could know in advance what I could expect with this low wing plane! Aerodynamically thinking,the nose should come up when the flaps are down due to increase lift from the wing, opposite to the effect of elevator down in put. But I am not sure about that. Hope that I am right!Many thanks.

[Tony Campbell]

Mikes right, it differs with every plane. I have an old Thunder tiger expo 3d. If I use the flapperon function on its huge ailerons, it dosen't change trim at all, Which is the exact opposite of what I was expecting considering the size of the ailerons.
Just get nice and high and if possible, have the flaps on a proportional control rather than a switch. If it has any drastic trim changes, seeing them come in gradually is easier than an 'all at once' deployment.

[Htin Aung]

Hi Geronimo, Futaba FF8 radio flaps are proportional control knob. I could bring down the flaps slowly and small amount one at a time to test the response of the aeroplane.If the weather is good tomorrow, I will try flaps down and see what happens.Fast scale low wing plane like Lancair 60 from Great plane will land better with flaps down, like a full size plane, nice and slow landing.Thanks.