What happened
On July 12, 2018, a Robinson R44 Raven 2, registration F-GTRG, was completing a local training flight at the Villefranche-Tarare airfield. Following the flight, the pilot and an instructor landed on the grass near the airfield's refueling station to take on fuel.
As part of the engine shutdown procedure, the pilot reduced engine power to approximately 70% in accordance with the flight manual. After landing, the instructor exited the aircraft to walk toward the fuel pump. While the engine was still running, the pilot noticed an insect inside the cockpit. In an attempt to chase the insect away, the pilot made a sudden movement with his hand. This motion resulted in an unintentional application of the collective pitch control. The helicopter lifted approximately one meter off the ground before dropping and tipping onto its left side.
The investigation
The investigation focused on the mechanical state of the aircraft and the actions of the crew. Investigators examined the wreckage and found that the damage was limited to the tail boom, the tail rotor, and the main rotor blades. The deformation of the main rotor blades suggested that the aircraft was at a low power setting when the blades struck the ground. No technical failures were identified that could have contributed to the accident.
Regarding the flight controls, the investigation noted that the pilot had engaged the friction device on the cyclic and collective controls. While this device increases the effort required to move the controls, it does not mechanically lock them. The investigation established that even at a reduced power setting of 60-70%, the engine still provided sufficient power to lift the aircraft if a sudden, forceful movement was applied to the collective control.
Findings
- The primary cause of the accident was the unintentional movement of the collective pitch control caused by the pilot's reflexive action to swat an insect.
- The presence of the insect created a sudden distraction and surprise for the pilot.
- The aircraft was at a power setting sufficient to generate lift despite the use of the control friction device.