History of Flight
The student-pilot departed from Grenoble-Le-Versoud airport around 13:15 on his second solo cross-country flight. After landing on runway 27 at Grenoble-Isère airport, he turned left to vacate the runway and hover taxied on taxiway S3. He then proceeded toward parking point A7 assigned by the controller. While hover taxiing in the parking area on a heading of 160° at a ground speed of approximately 10 kt, the helicopter gradually turned left. The left yaw rate increased, and the student-pilot made control inputs. Subsequently, a more pronounced left yaw occurred. The student-pilot pressed the right rudder pedal without reaching the stop and pulled up on the collective pitch lever. The helicopter rose about 20 m while continuing to spin left, then descended. During this phase, the rudder pedal input was reduced and reversed to the left stop. After six complete rotations, the helicopter struck a lighting pylon beside the fuel pump and fell vertically to the ground.
Wreckage and Site
The helicopter wreckage lay on its right side at the edge of the parking area near the fuel tank at the base of a lighting pylon. The tail boom was broken, with the rear section several meters away. Damage to the pylon indicated impact at about five meters height. Airframe damage was consistent with collision with the pylon and then the ground. Flight control linkage continuity was verified; examination revealed no mechanical failure that could explain the loss of yaw control.
Pilot Information
The 32-year-old student-pilot was training for a Private Pilot Licence (Helicopters). He had accumulated 50 flight hours, including 46 hours dual and 3 hours solo, all on the Cabri G2. He had landed once at Grenoble-Isère during instruction and had never flown in strong winds or turbulence. His first solo cross-country flight that morning was between Grenoble-Le Versoud and Albertville. He then prepared for the flight to Grenoble-Isère under instructor supervision, consulting weather forecasts. The student-pilot reported that while hover taxiing on taxiway S3, the tower controller announced strengthening winds. He felt the wind increase near parking point A4 and recalled the helicopter "rolling" left, which he attributed to a gust. He corrected with right rudder, right cyclic, and a gentle collective pull. The helicopter then began a left spin; he tried to counter with right rudder and collective pull to avoid ground contact.
Meteorological Information
METAR at 13:00 reported CAVOK with variable wind 3 kt. The TAF forecast a mean wind from 080° of 6 kt, picking up between 12:00 and 14:00 to 210° at 10 kt, with temporary conditions between 16:00 and 19:00 of 210° at 20 kt gusting 30 kt. METAR at 13:30 indicated wind 190° at 10 kt, and at 14:00 210° at 9 kt gusting 19 kt. Météo-France reported that after 13:15, wind shifted to southwesterly, increasing to gusts over 20 kt after 13:17, likely due to turbulence from the Chambaran plateau. Estimated mean wind at ground level was 10-14 kt with gusts 20-23 kt; wind at 20 m height was 15 kt, and at 50 m 20 kt.
ATC Communication
At 13:29, the tower controller reported wind 200° at 8 kt and authorized a direct approach. At 13:33, the pilot reported long final and was cleared to land; controller noted wind 190° at 10-16 kt. At 13:35, controller warned of wind 200° at 13-20 kt. At 13:36, as the helicopter hover taxied, the controller instructed to vacate via taxiway S3 and proceed to parking point A7.
Helicopter and Yaw Control
The Cabri G2 is a light two-seat helicopter with a piston engine, three-blade main rotor (clockwise), and a shrouded tail rotor (Fenestron). The Fenestron provides yaw stability and, with a left-turning rotor, generates lateral lift in forward flight to counter torque. The manufacturer published Service Letters addressing yaw control risks. SL 12-001 (2012) warns of yaw control in approach when speed decreases; it describes a possible left yaw if sideslip is uncontrolled, aggravated by right crosswind. SL 19-001 (2019) covers throttle management during simulated engine failure; SL 19-002 (2019) addresses controllability in yaw at low rotor speed. Experienced pilots and instructors noted the Cabri G2 is demanding due to yaw sensitivity and quick pedal response requirements.