S76 collective dropping
Does anyone have any thoughts as to why the collective in a S76A++ could be extremely heavy to the point that the mag brake is unable to hold it in position?
This one machine out of 4 that I fly, the collective is very heavy from flat pitch all the way up to takeoff power, and getting increasingly heavy beyond 70% torque (aerodynamic load?? mechanical disadvantage??). I'd guess that there must be 10 lbs of force required at the end of the collective lever when moving it off flat pitch and close to 20 lbs of force needed to move it and hold it near takeoff power. Needless to say my left bicep is getting quite the workout.
If the force trim button is then released the collective will drop maybe 10% torque or more until the mag brake springs balances the force, then it does not drop any further. It's a DAFCS equipped bird and some of our pilots have resorted to using 3 cue mode temporarily to make small adjustments in power in the cruise as it is almost impossible to set power manually (pull power 10% TQ over desired power and hope that it falls back to the power you want!).
The mechanics seem to be completely clueless as to how to fix it. Since joining the company I've been told this has been an ongoing issue for years with this bird and I've been told that the mechanics' solution invariably has consisted of changing the mag brake unit when a pilot complains, yet it has done nothing to solve the problem. (Albert Einstein's definition of insanity?)
There is no collective to yaw coupling going on, the pedals feel fine, the controls are otherwise smooth and no noticeable fluctuations in hydraulic pressure going on. Any thoughts? Hydraulic restriction? Bad rigging? Bad MR spindles? Worn flight control bushings? Bad flight control dampers?