When the collective is further raised (producing a total rotor thrust greater than its weight) to lift-off, a pitching moment is about to be generated. Because, if the helicopter slides downhill towards the flat surface, the aft edge of the skids, when in contact with the flat surface, will act as a pivot point causing the helicopter to pitch up with the risk of a tail boom strike.

In this case, if the collective is further raised, the problem will become worse, since an increased total rotor thrust will generate an increased pitching moment, thus pitching the helicopter more up.

Also, if applying forward cyclic control, inclining the total rotor thrust forward, it may not be a sufficient recovery action, especially in case the helicopter has already started to slide downhill or to pitch up when in contact with the flat surface. Forward cyclic may also cause a main rotor strike to the opposite direction (uphill).

The recommended recovery action will be to lower the collective decisively, but smoothly, so as to zeroize the total rotor thrust and allow the helicopter’s weight, in conjunction with the skids’ friction drag, to prevent any downhill sliding and pitching moment.