What happened
On Thursday, January 11, 2024, at approximately 15:55 local time, a Robinson R22 Beta II registered F-GJYB crashed into the sea near Cannes-Mandelieu. The aircraft was operated by Green Bees Helico 2 for an instruction flight. Two people were on board: an instructor and a student pilot. Both occupants were fatally injured, and the helicopter was destroyed.
The flight began with a walk-around inspection and engine start at 15:33. The crew performed ground effect maneuvers over the runway for about ten minutes before taking off from Runway 22 at 15:54. Following the published departure procedure, the helicopter turned left and then right. Shortly after the turn, the instructor requested clearance to cross the extended centerline of Runway 17/35. At 15:55:59, a continuous "LOW RPM" aural warning was audible on radio transmissions. Three seconds later, the helicopter lost altitude rapidly with nearly zero horizontal speed. The instructor reported an engine failure while the warning continued to sound. Witnesses observed the rotor blades slowing and rising upwards before the aircraft struck the water surface at 15:56:12 and sank immediately.
The investigation
The BEA examined the wreckage recovered from a depth of approximately 30 meters, about 300 meters from the coast. The damage was consistent with high vertical energy impact and low rotor energy at collision. Examinations of the drive system and control linkages revealed no mechanical anomalies that would prevent free travel of the controls. The carburettor heat control was found in the "on" position, but it could not be confirmed if this was due to pilot action or impact forces.
Meteorological data indicated a temperature of +13°C and relative humidity of 62% at the surface. Although these conditions are above freezing, they fall within the range where carburettor icing can occur, particularly with high humidity. The investigation noted that the engine had not fully cooled since the previous flight, which may have affected the accuracy of the carburettor temperature gauge check during pre-flight.
Findings
The BEA concluded that a substantial reduction in engine power occurred shortly after take-off. While the exact cause could not be determined with absolute certainty, the atmospheric conditions presented a significant risk of severe carburettor icing. The engine governor likely masked the initial symptoms by maintaining constant RPM, delaying the instructor's perception of the problem. Once the governor could no longer compensate for the power loss, the rotor RPM dropped below the critical threshold, leading to a vertical descent and impact with the sea.
A contributing factor was identified as the instructor’s lack of recent autorotation practice relative to her total experience, which may have affected her reaction time during the sudden power loss. The investigation also noted that the "LOW RPM" warning was audible, suggesting the collective pitch lever had not been fully lowered to initiate an immediate autorotation.
Safety action
The BEA emphasized the risk of carburettor icing on R22 helicopters even in clear skies and temperatures above freezing. It recommended that pilots use carburettor heat when in doubt to keep the temperature outside the yellow arc on the gauge. Additionally, the authority highlighted the importance of immediate collective pitch reduction during engine failure simulations, rather than attempting to diagnose the problem first.