giap69pavel,

I used century jet retracts and a Robart adjustable control valve. They look very realistic with about a 3-4 second rotation, and have never given me any trouble. Without the valve it they went so fast I though they were going to smash through top of the wing!!! You can see the valve in the picture here. One side of the servo drives the valve and the other the mechanicle pushrod to the tailwheel.