That scenario gives me the willies. I’m not a pilot so I cannot give any answers to your question, but I’ll be watching for replies.. .FWIW, I was a pax in a 500 when that situation occurred. We were straight and level, about 1000’ AGL when the pilot tried to lower the collective. It was jammed solid!. .We cruised around for a while thinking that the engine was going to fail next just to make things even more interesting. After a bit of a conversation with him, we toyed with the idea of rolling off the throttle slightly and doing some turns, to lose altitude with the intention of ‘running it on’ when we got to the ground. He did not risk raising the stick in case it put us into a climb that we could not get out of.. .The pilot eventually loosened his harness to get a better look at the collective stick and noticed that the seat bottom had shifted slightly across and part of it was now under the lever preventing him from lowering it. The Velcro under the seat prevented him from sliding the seat back to its proper position, so the pilot had to completely undo his harness and raise his bum high enough for me to drag the seat back.