My swash plate moves down on teh shaft after a few flights??

[BSchorr]

My swash plate moves down on teh shaft after a few flights and causes my forward and aileron movements to weeken.... I see there is a set screw stoper aobut 2 cenimeters below it, but i think that is for the main chassis and main shaft for something.

[Skiddz]

Are you tweaking the trim for the left stick at all when you fly?? The set screw on the collar is to hold the main shaft in place. It should be tight against the bearing right below it and there should be very little, if any vertical play in the main shaft when it's secure.

What are the servo arms doing between the time it's all working properly and when the swash drifts down??