What happened
On July 2, 2024, at approximately 10:10 local time, a Guimbal Cabri G2 helicopter, registered HB-ZOQ, was conducting flight training near Orbe, Switzerland. The aircraft, operated by Heli-Lausanne SA, was performing a hover maneuver under Visual Flight Rules (VFR). The flight was part of an instructional session, with a student pilot operating the aircraft alone while an instructor monitored the maneuver from the ground.
During the hover, the instructor observed smoke emitting from the engine's exhaust pipe. Immediately following this observation, the helicopter experienced a sudden loss of altitude, resulting in a hard landing. The aircraft sustained light damage during the impact, though no injuries were reported to the pilot or any third parties.
The investigation
Following the incident, the Swiss Transportation Safety Investigation Board (SUST) initiated an inquiry. Post-incident inspections of the Guimbal Cabri G2 were conducted to identify the mechanical source of the smoke and the subsequent loss of power. The investigation focused on the engine components to determine why the aircraft failed to maintain altitude during the hover.
Findings
Technical inspections of the aircraft revealed that the issue originated within the one-way clutch assembly (freewheel assembly). The failure or malfunction of this specific component was identified as the primary factor leading to the visible smoke and the subsequent drop in altitude.