The student pilot, who was in the right-hand seat and accompanied by an examiner, took off from Lyon Bron airport for a practical examination with a view to obtaining his helicopter private pilot licence.
While the helicopter was hovering in ground effect at Lyon-Brindas aerodrome, the examiner informed the student that the next exercise would be a simulated engine failure in hover. The examiner began the simulation by decreasing the engine power. The student pilot felt the helicopter sinking and a right yaw movement. He complied with the "engine failure in hover" procedure by applying full left pedal and pulling on the collective pitch control to counteract the sinking of the helicopter and cushion the contact with the ground. During this manoeuvre, the engine power suddenly increased and the helicopter started rotating left while rising. The student asked the examiner to "shut down the engine”. When the engine power was finally reduced, the helicopter sunk and hit the ground.
The examiner’s action on the twist grip had not reached the engine idle mechanical stop when the student pilot started the procedure associated with this failure. The improper management of the twist grip by the examiner at the start of the simulated engine failure in hover combined with the student pilot's application of the engine failure IGE procedure led to the loss of control in yaw.