What happened
On June 10, 2016, a Robinson R44 II, registration F-GZAH, was conducting a local flight near Le Pescher, France. The pilot, carrying three passengers, departed from a private property in Puy d’Arnolog with the intention of landing at a friend's property. After an initial reconnaissance pass, the pilot performed a maneuver along a power line before turning back toward the landing site.
During the final approach, the pilot attempted to stabilize the aircraft at a height of approximately 30 to 40 meters. At this stage, the aircraft began to yaw to the right. Although the pilot applied left pedal to counteract the movement, the yaw persisted and the aircraft entered a rotation of approximately two full turns. In an attempt to reduce the main rotor torque, the pilot reduced collective pitch, which inadvertently increased the rate of descent. The rear of the helicopter struck the ground heavily, resulting in the destruction of the helicopter, though the pilot and three passengers remained unharmed.
The investigation
The investigation focused on the aircraft's performance and the pilot's maneuvers. Investigators confirmed that the anti-torque controls were functional and rotating at the time of the accident. The pilot, who had approximately 100 total flight hours, noted that the landing site required high precision due to the slope and nearby obstacles.
Technical analysis of the aircraft's weight and environmental conditions revealed that the estimated mass of the helicopter was approximately 1,070 kg. Based on the ambient temperature of 20°C and the pressure altitude, the maximum allowable mass for hover out of ground effect (OGE) was 1,080 kg. This placed the aircraft very close to its performance limits.
Findings
- The aircraft was operating in a power-limited state during the final approach.
- The pilot was performing the approach out of ground effect (OGE) in hilly terrain without accounting for the reduced power margins.
- As the pilot attempted to correct the yaw with pedal inputs, the aircraft approached its maximum power limit for OGE flight.
- The loss of control was caused by the aircraft exceeding its available power capacity to maintain a hover or controlled descent out of ground effect, leading to an unrecoverable descent.