What happened
On July 5, 2020, a DJP 2000 gyroplane, registration 31LI, was participating in a formation flight near Sos, France. The flight was part of a weekend event organized by a local club, consisting of eight gyroplanes flying in a V-shaped formation and one fixed-wing microlight flying outside the group. The aircraft was flying at altitudes between 1,100 and 1,500 feet, navigating toward a turning point at the village of Sos.
As the formation reached the turning point, the 31LI experienced a sudden loss of control. The aircraft fell almost vertically and collided with the ground. The impact resulted in one fatality and the total destruction of the aircraft.
The investigation
The investigation focused on the mechanical state of the aircraft and the sequence of events leading to the impact. Investigators examined the wreckage, which was spread across a 50-meter radius. Key observations included:
- The main rotor blades showed white marks on their leading edges, which coincided with deformations and impact marks found on the tail fin and rudder.
- The rudder had been struck by the rotor, causing it to separate from the airframe.
- The rudder control cables were broken, and the rudder likely struck the engine's pusher propeller after the initial rotor strike.
- This secondary impact caused an engine oil leak, visible as a plume of white smoke, which subsequently led to a reduction in rotor rotation speed and the final descent.
Video footage from a witness supported these findings, showing a component—likely the rudder—partially separating from the aircraft while still trailing via the control cables, followed by the appearance of white smoke.
Findings
The investigation established that the main rotor struck the rudder during flight. This phenomenon, known as rotor flapping, was the primary cause of the accident. While the exact trigger for the flapping could not be definitively identified, the BEA noted several potential contributing factors:
- Rapid control inputs on the pitch axis lever.
- Localized aerological phenomena.
- Wake turbulence from the aircraft positioned ahead in the formation.
- A combination of these aerodynamic factors.
Due to the severity of the structural damage and the resulting loss of engine oil and rotor speed, the pilot was unable to maintain control of the aircraft.