> Are you asking about testing for the initial certification of an
> aircraft type ...or simply for maintenance purposes "cwatters"?
I was thinking of the former. I'm familure with the basic theory of control systems and the impulse test but couldn't see how you could do this for real in the air. Can the rudder on an heavy produce enough yaw to simulate heavy turbulence? I was reading elsewhere on PRUNE that rudder throw has to be limited above certain speeds for stress reasons.