ORIGINAL: Marian
During the take off it moves on runway as on rails. Airborne: it gains altitude smoothly. When I try to make the first turn, at the beginning everything goes well, but suddenly it falls on wing. I was able to gain speed and level it,.......
Marian
Marian,
In addition to previously mentioned ideas... I am wondering if you are using any differential in your ailerons? This may help. Sounds to me as you might be stalling out a wing with the ailerons.
A way to confirm this would be to try a rudder turn leaving the ailerons alone. Just something to try. Good luck.