Everyone calls the event "Jack Stall" but someone correct if I am wrong here....in "Jack Stall" one reduces collective to recover.....is this not the situation that occurred....the recovery action had already been taken well prior to onset of the controls locking.
On a fairly fast descent, in a turn, with low torque, the cyclic and collective locked up
Also...if the recovery action is to reduce collective....how does one do that if the controls are "locked" up?
Is it possible what happened here is the hydraulic pump cavitated due to the hydraulic fluid finding its way to the top of the tank and leaving the pickup open to air at the bottom of the tank? Thus, the real problem was a simple hydraulics failure that was cured by some positive "G" returning to the aircraft.
The Alouette III used to do that in severe turbulence in the mountains.....hit a very strong down draft and the controls would go stiff and pass a bit of feedback into the controls.....when the next up draft came along all was well again.