What happened
On 7 June 2019, a Guimbal Cabri G2, registration F-HOLA, was performing an introductory flight at the Grenoble Le Versoud aerodrome. The flight was operated by Hélisair, with an experienced instructor and a student on board. The aircraft was transitioning from forward level flight into a hover at the Final Approach and Take Off area (FATO) when the collective stick in the instructor's seat suddenly separated from its base.
This mechanical failure caused the helicopter to yaw sharply to the left and upwards. While the instructor attempted to maintain control using the cyclic and rudder pedals, the rotor RPM decreased and the aircraft began to descend. The helicopter's tail boom and skids struck the ground, causing the aircraft to slide into the grass at the edge of the runway. There were no injuries to the two occupants, though the helicopter sustained substantial damage.
The investigation
The BEA examined the aircraft and recovered video footage from a witness. The investigation confirmed that the engine and power transmission components, including the fenestron, were functioning normally. The primary failure was the separation of the left-seat collective stick from its base.
Investigators analyzed the dual control assembly mechanism, which uses a locking sleeve and four balls to secure the stick. While the system was designed for easy installation, the investigation found that the uniform black color of the base and sleeve made it difficult to visually identify if the sleeve was properly seated.
It was established that during the flight prior to the accident, a student pilot had removed the dual controls to prepare for a solo flight and had reinstalled them. Although the instructor had performed a pre-flight check and a control deflection test, the improper assembly went undetected.