I have been through most of the training missions and have a fairly good feel for flying the helicopter. The trim works as I expect. I push the cyclic foward, hit the trim button, release it and slowly release the cyclic - the helicopter maintains that attitude well.
I've not tried flying in a multiplayer mission *AND* a single player mission I've downloaded from the net. In both situations the trim does not seem to be working for me at all, and I can't maintain forward direction without a LOT of force on the cyclic.
The only difference is, in the training missions, the bird is hot when you hit the 'control' button - in these missions and multiplayer I have cheatstarted the bird with the lwin-home button. I have checked that the three autopilot buttons are on. FCS is off.. But I still can't get this thing trimmed or stable.