What happened
On January 24, 2018, a Robinson R44 helicopter, registration F-GZBD, was conducting a general aviation flight with a pilot and two passengers. The flight originated from a private field in Le Fayet (74) and was traversing the Tarentaise sector. While flying at approximately 7,500 ft near the Tignes dam, the pilot experienced unusual vibrations and felt that the engine was not delivering sufficient power, noting a sensation that the aircraft was overloaded and flying too high.
Due to the challenging terrain, the pilot decided to terminate the flight and divert to the nearby Les Boisses helipad. During the final approach, which was conducted on a shallow glide path with horizontal speed, the pilot was unable to achieve a hover. The aircraft struck the ground with significant force and slid until it came to a stop against a snow wall. The impact caused the main rotor blades to strike the tail boom, resulting in heavy damage to the helicopter.
The investigation
The investigation focused on the pilot's reports of engine performance issues and the circumstances of the landing. At the time of the incident, weather conditions at the helipad were reported as CAVOK with calm winds and a temperature of approximately 5 °C. The pilot, a private pilot holder with 421 total flight hours, had recently completed two hours of flight time in this specific aircraft.
Technical inspections of the aircraft were conducted by a maintenance workshop. These examinations found no evidence of engine malfunction or mechanical failures that could account for the lack of power or the vibrations reported by the pilot during the flight.