Collective bounce?
The S-61 had
The 61 collective bias used to be easy to correct, BUT, someone filled up the nose bay with avionics and now it's one helluva job getting to the area to do so, if the
bias is set correctly, the collective is a dream, you just have to get used to the 'Sikorsky Shuffle' if you're slow in getting the SSL(s) forward on engagement!!