Meanwhile I found the solution and in case someone one day finds this problem, he will be happy to find the solution here.
Setting a controller axis to the airbrake brakes the code of this plane. So i had to remove the spoilers command from my rx axis. Key commands work fine and can also be assigned to a controller button. After using the controller axis on the spoilers, a reload of the plane is needed to make it work again. Something gets stuck in th code when using an axis. For me it is still not clear, what makes the airbrakes, the rudders and/or the flaps since when deploying airbrakes these do hardly move but the plane gets slower. At a certain point the flaps and slats deploy and both rudders turn towards inside to brake but not a higher speeds.
Now what remains, i loved to have an axis for airbrakes for all other planes. Maybe one could program the FSUIPC to avoid this axis in the F35. I think it's easier to get used to another spoiler command while flying.
Regards Dan
