The Gazelle getting airborne seems straightforward - if you switch off the hydraulics, the lever tends toward mid-position (you have to push it down to get it to land). So if the engineer hasn't really put enough friction on then it isn't a surprise that it jumps up when the hyd pressure is removed. The 180 turn is because the pedal forces are very high without hyds and if you don't have a strong right leg ready to brace, you will yaw very quickly.