moldy oldy

mvsgas yours is a much more difficult question to answer than one might expect at first blush. There are two different types of flight control systems in helicopters. One is the mechanical system and the other is the boosted system. In both types of systems you have a means of applying friction to the controls, this keeps rotors from doing unpected actions during startup and shutdown. It also enables the indivdual pilot to apply a level of friction that is comfortable for him/her. In flight, force trim allows the pilot to trim off pressure in the controls and also will allow the pilot to release the controls for short duration actions such as tuning a radio or picking up a map. If the aircraft is hit by a wind gust or becomes dynamicly unstable the force trim will allow it try to return to its approximate pre upset attitude. Force trim hat switch would generally relate to spring or a brake gradient form of cyclic positioning. However in some systems the aircraft will have a stability augmentation system which trys to hold attitude by gyros in which case the attitude would be adjusted by using a trim hat switch. The result is the same but the means is different. In the unboosted system a certain amount of feedback will come back through the linkage from the rotating dynamics and some of this is mitigated by the springs in the linkage. The controls can still be moved against the force trim but will want to return to the prepostion. In a boosted system without the force trim engaged or friction applied the controls can move without a pilot induced action if the controls are released.

Sorry Alpha one six I must disagree, I have flown quite abit in legacy aircraft such as Hiller, Enstrom, Kaman, Hughes, and Schweizer and all of the models I have experience in have a trim hat on the cyclic that functioned electrically through motored spring displacement for cyclic load for trim. If one looks at current military aircraft in the U.S. Army, the mh-6 and the uh-60 do have a funtioning trim hat just like their civilian counterpart. On the uh-60 you have the option of trim hat and gradient disconnect with a button. This is an interesting thread thanks for making me pull out my manuals.