What happened
On Monday, March 27, 2000, at approximately 18:00, an Eurocopter AS 350 B (registration F-GGTQ) was operating a flight from Saint-Valéry-en-Caux toward Cergy. During the flight, the pilot decided to land in a field near Bézu-Saint-Eloi to consult a navigational chart.
After landing, the pilot placed the collective pitch control into the locking device. While the pilot was reviewing the map, the collective pitch control unexpectedly disengaged from the locking mechanism. This caused the collective lever to move upward, resulting in an immediate change in the main rotor pitch. The sudden imbalance occurred before the pilot could intervene, causing the helicopter to tip onto its side.
The investigation
The investigation focused on the mechanical failure of the locking mechanism during the ground phase of the flight. Investigators examined the state of the collective pitch control and the locking device to determine why the lever was able to move without pilot input. The investigation established that the primary issue was the unintended disengagement of the collective pitch control locking plate.