jellycopter,
Given that you and me and most other ppruners can fly, and we can actually fly by hand, the issue under discussion is whether the WIND is the source of the retrim effect. The belief that as you travel up or down wind you need to retrim is ficticious. The need to trim any helicopter, and fly it precisely, is not at issue!
The longitudinal trim of the helicopter is subject the the phugoid mode, where the pitch axis has an oscillation of perhaps 5 seconds. In a turn where you have upset the longtudinal trim of the helo, you have naturally upset this phugoid mode, so you can expect to see the nose work itself up and down in a divergent manner at perhaps 2 to 8 seconds (depoending on many factors, mostly the effectiveness of the horizontal tail). Thus, as you turn, you have to pump the cyclic longitudinally because the nose is slowly bobbing up and down. In windy days you have more turbulence, so the mode might be more active throughout the maneuver.
If I can simply state the main point of this thread (hey its your question, if I have it wrong, correct me!), it is the Assertion:
The wind direction makes the longitudinal axis retrim as the aircraft goes upwind and down wind in forward flight.
I contend that this is not true.
PS, the autopilot CANNOT invisibly fix the aerodynamics of the aircraft, it would show this "retrim" were it a fact. Autopilots are just dumb but precise pilots of their own right, and they cannot change the inherent stability of the aircraft, they can just use the controls to help quell the basic aircraft.
Last edited by NickLappos; 9th January 2005 at 21:04.