What happened
On December 8, 2020, a Hélicoptères Guimbal Cabri G2 was performing a solo navigation flight as part of a pilot training program. The flight originated from Egelsbach, with planned stops at Aschaffenburg and Speyer. After completing the previous legs of the flight, the pilot prepared for departure from Speyer airfield.
During the initial climb phase, the aircraft began to yaw significantly to the left. The pilot reported seeing a flashing warning light indicating low main rotor RPM and attempted to initiate an autorotation to find a suitable landing area. However, video footage from the airfield showed that the aircraft accelerated to over 70 knots along the runway before entering a climb and a left turn. As the aircraft climbed, it developed a nose-down attitude and began to spin rapidly around its vertical axis. The helicopter completed two full rotations within four seconds before striking the ground in a grassy area near a hangar. The impact caused heavy damage to the aircraft, though the pilot escaped with minor injuries.
The investigation
The BFU examined the aircraft's technical condition, the pilot's experience, and the flight's execution. Technical inspections of the engine, the Fenestron tail rotor, the drive belts, and the governor system revealed no mechanical failures or malfunctions. The electronic pilot monitor (EPM) showed no recorded sensor or alarm errors. The investigation also reviewed airfield camera footage, which contradicted the pilot's claim of an immediate autorotation, as the aircraft maintained high forward speed during the onset of the yaw.
Findings
- The primary cause of the accident was improper coordination between engine power applications and pedal inputs required to counteract torque.
- The pilot's flight profile deviated significantly from the manufacturer's recommended procedures, which suggest a slower, more controlled takeoff.
- The pilot, while highly experienced in fixed-wing aircraft, was still in the early stages of helicopter training and likely became overwhelmed by the rapid loss of control.
- There was no evidence of technical failure in the Fenestron or the engine; the aircraft's yaw was driven by the torque of the powered main rotor.