What happened
On November 30, 2019, a pilot operating a CH77 Ranabot microlight helicopter, registration 83ARU, was conducting a local flight near Vinon, France. After departing from Vinon aerodrome, the pilot maintained a routine flight path, eventually announcing his approach toward Manosque.
While flying at an altitude of approximately 50 meters, the left side door of the aircraft suddenly detached from the airframe. Shortly thereafter, the right side door also became detached. This event caused the aircraft to lose stability and enter a steep descent. The microlight struck trees and collided with the ground, resulting in a post-impact fire. The pilot was fatally injured, and the aircraft was destroyed.
The investigation
Investigators examined the wreckage and the distribution of debris, noting that the left door was found approximately 300 meters from the main impact site, while the right door was found 60 meters away. The examination of the hinges revealed that both doors underwent a similar detachment process, characterized by a sudden tearing of the rear attachment points.
Testing conducted by the BEA revealed that the door locking mechanism could be deceptive; specifically, the internal latch can create the impression that a door is securely closed even if the primary locking bolts are not fully engaged. Furthermore, the investigation noted that aerodynamic forces at certain speeds could cause the door to lift from its jamb if not properly secured. The investigators also identified a previous error in the aircraft's assembly where a drill hole near the latch had been covered with adhesive tape.
Findings
- The primary cause of the accident was the successive detachment of the aircraft doors during flight, which destabilized the microlight.
- The pilot was likely caught off guard by the sudden loss of the doors, leading to an inadequate response on the flight controls.
- The low altitude of the flight prevented the pilot from executing an effective recovery maneuver before the collision.
- Aerodynamic forces acting on the doors contributed to the separation from the airframe.