What happened
On 27 April 2022, a GLASER DIRKS DG-600/18 glider, registration F-CIEA, was performing a winch take-off from the Seyne-les-Alpes airfield. Approximately 100 meters into the takeoff run, the aircraft reached a height of only a few meters before suddenly pitching into a nose-down attitude. The pilot attempted to apply nose-up input, but the controls met heavy resistance and failed to respond.
The aircraft subsequently collided with the runway. The impact caused the underside of the fuselage to deform, which resulted in the separation of the winch cable. The glider then entered a ground loop after the right wing contacted the terrain, eventually coming to rest in a field adjacent to the runway. The pilot was able to exit the aircraft without assistance.
The investigation
The investigation focused on the aircraft's assembly, as the pilot had reattached the tail plane alone the previous day. While the pilot noted some abnormal stiffness in the pitch controls during pre-flight checks, he attributed this to the trim being set at the nose-down limit.
Investigators examined the elevator control linkage and discovered that the roller, which facilitates the connection between the pitch control and the elevator, had slipped out of its guide. This mechanical misalignment prevented the elevator from achieving full deflection. Testing by the BEA confirmed that it is possible to install the tail plane assembly without the roller being properly seated in the guide, a condition that allows for minor control movement but prohibits full range of motion.
Findings
- The primary cause of the accident was the incorrect rigging of the elevator control connection during the assembly of the tail plane.
- The pilot failed to detect the error during the visual inspection through the provided Plexiglas window, as the manual did not specify exactly what the pilot should look for, and the window's design makes it difficult to see the roller when correctly positioned.
- The pre-flight control check was ineffective because the flight manual lacked a detailed procedure for a "positive control check" to ensure full range of motion.
- The pilot's observation of control stiffness was dismissed as a result of the trim position rather than a mechanical obstruction.