What happened
On May 20, 2011, an Agusta 109 helicopter, registration F-GLEE, was performing training maneuvers at the Valence Chabeuil aerodrome. The flight, conducted by an instructor and a trainee pilot, was intended to fulfill requirements for a type rating. The flight plan included circuit patterns and specific engine failure exercises during takeoff, which required simulating a power reduction, entering autorotation, performing a flare to reduce descent rates, and leveling the cyclic to prevent tail rotor contact with the ground.
During the circuit, the instructor noted variable wind conditions and elected to perform the first exercise facing north. After takeoff, the instructor began the demonstration at approximately 80 feet. During the flare maneuver, the instructor noted a sudden sink in the aircraft. Despite applying collective pitch, the tail rotor struck the ground, resulting in a hard landing with a recorded vertical acceleration of 1.72 g. The aircraft sustained heavy damage.
The investigation
The investigation focused on the execution of the autorotation maneuver and the environmental conditions at the time of the accident. Investigators reviewed the flight experience of both pilots, noting that while the instructor had significant total flight time, they had limited recent experience performing engine failure exercises specifically on the Agusta 109. The trainee pilot had very limited experience on this specific type, with only three hours recorded in the previous three months.
Meteorological data indicated a light, variable wind of approximately 4 knots, trending from the east, with gusts below 10 knots. The investigation examined how these low-wind, crosswind conditions influenced the effectiveness of the flare maneuver.
Findings
- The primary cause of the accident was the instructor's delayed control inputs during the flare phase of the maneuver.
- Low wind speeds and crosswind components reduced the effectiveness of the flare, requiring more proactive and anticipatory control inputs.
- The instructor's limited recent experience performing engine failure simulations on this specific aircraft type served as a contributing factor.