Accident to the Robinson R22 registered F-GJYB on 11/01/2024 at Cannes

The investigation was not able to determine who had the controls and what actions were carried out on the controls, and in particular on the collective pitch lever and the carburettor heat control, by the instructor or the student pilot.

A few minutes after taking off, the helicopter experienced a substantial reduction in power. The investigation was not able to determine with certitude, what caused this. However, given the temperature and humidity conditions which existed at the time of the accident, the risk of severe carburettor icing was present. If hypothetically such a phenomenon occurred, associated with possible prior inadequate management of the carburettor heat control, it is possible that the carburettor air duct became blocked, accompanied by a loss of engine power.

The instructor's perception of icing may have been delayed by the governor temporarily maintaining the engine RPM. When the governor was no longer able to compensate for the decrease in engine RPM, and in the absence of an immediate autorotation, the rotor RPM decreased and then the helicopter fell nearly vertically until collision with the surface of the water. 

It was not possible to establish the reason why the collective pitch lever had not been completely lowered although the “LOW RPM” aural warning was sounding.