What happened
On May 31, 2019, a Robin DR221, registration F-BOZH, was performing a takeoff from the unpaved runway at the Saint Roch Mayères altisurface. During the takeoff roll, after traveling approximately 200 meters, the pilot attempted to align the aircraft with the runway centerline. However, the aircraft began to deviate to the left. The pilot was unable to counteract this movement, causing the aircraft to exit the runway and enter the sloping terrain bordering the strip.
As the aircraft moved into the slope, it underwent an involuntary takeoff. To avoid hitting visible rocks, the pilot applied back pressure on the controls. This maneuver caused the propeller tips and the tail section to strike the rocks, resulting in a significant impact felt from the rear of the aircraft. The impact caused the tailwheel to be torn off. Despite the damage and degraded performance, the pilot maintained control and diverted to Annecy Meyellhet airport, performing a precautionary landing on an unpaved runway.
The investigation
The BEA examined the aircraft's condition and the pilot's actions. The investigation found damage to the propeller blade tips, punctures in the upper and lower wing surfaces, and damage to the tail cone, rudder, and vertical stabilizer caused by the loss of the tailwheel.
Investigators also reviewed the environmental conditions and the pilot's preparation. The weather was favorable, with a light northeast wind and clear visibility. The pilot had performed a visual inspection of the runway prior to takeoff but had parked the aircraft offset from the centerline to avoid other parked aircraft. The investigation also noted that the grass at the edges of the runway was unmaintained and taller than the center, increasing rolling resistance on the left main gear.
Findings
Several factors contributed to the loss of directional control:
- The combination of leftward yawing forces, including P-factor (spiraling slipstream), gyroscopic precession, and the weathercock effect from the wind.
- Increased resistance on the left main landing gear as it encountered taller grass at the runway edge.
- The pilot's decision to align the aircraft with the flight path while still at a low speed, which reduced the effectiveness of the rudder.
- The presence of a slope (devers) at the edge of the runway that facilitated the involuntary takeoff once the aircraft left the paved surface.
- A lack of vigilance due to overconfidence in familiar, favorable flying conditions.