What happened
On May 17, 2003, a Robinson R22 helicopter, registration 3A-MGM, was performing its third solo flight at the Monaco heliport. After a successful landing on the mobile platform "Bravo," the trainee pilot remained on the platform with the rotors turning while waiting for an instructor to join him.
While waiting, the pilot began following the post-landing checklist. During this process, the pilot turned the RPM governor switch to the "Off" position and reduced the engine speed to 75%. Shortly after, a sudden and significant increase in engine RPM occurred. The aircraft abruptly lifted off the platform, pitching forward and backward before pivoting sharply to the left. During this uncontrolled movement, the main rotor blades and the tail boom struck the wooden platform with great force. The helicopter eventually came to a rest on its skids near the edge of the platform. There were no injuries to the pilot.
The investigation
Investigators examined the wreckage and the landing site, which consisted of a wooden mobile platform. The examination of the platform revealed deep, arc-shaped gouges caused by the impact of the main rotor blades. The damage to the blades, the tail boom, and the drive shaft indicated that the engine was delivering high power at the moment of impact.
Technical inspections of the engine, airframe, and landing gear revealed no mechanical failures or pre-existing anomalies. The electronic engine regulation unit (governor) and its associated switch were found to be functioning normally.
In the cockpit, investigators found that the collective pitch friction mechanism was set to the tight position, and the metal bracket for this mechanism had been broken by an upward force applied with significant energy. The checklist was recovered from a door pocket. The investigation also noted that the governor switch was in the "Off" position.
Findings
- The pilot had begun executing the post-landing shutdown checklist, which includes turning the governor off, despite only intending to slow the engine.
- Because the RPM governor was turned off, the engine was susceptible to an overspeed.
- The inappropriate use of the throttle while the collective pitch friction was tightly set likely caused the sudden engine overspeed.
- The pilot's sudden movement on the controls during the engine surge led to the loss of control and subsequent collision with the platform.