What happened
On June 3, 2023, during a glider competition at Bailleau-Armenville aerodrome, a Centrair ASW 20 F (registration F-CFFF) experienced a sudden loss of pitch control during a towed takeoff. The pilot, who had re-rigged the aircraft that morning, reported that the glider bounced several times on the grass runway, making heavy contact with the ground. Following these impacts, the glider suddenly pitched up at an angle exceeding 30 degrees, reaching an altitude approximately 20 meters higher than the tug aircraft. The pilot subsequently released the tow cable. The glider then entered a sharp stall dive, and despite the pilot deploying flaps to attempt to mitigate the descent, the aircraft collided with the ground. The accident resulted in one pilot seriously injured and substantial damage to the glider.
The investigation
The investigation focused on the flight control systems and the condition of the elevator assembly. Investigators found that the elevator ball and socket connector had become disconnected. While the roll, yaw, and flap controls remained functional, the elevator control was interrupted at the connection point between the vertical control rod and the elevator.
Technical examination of the L’Hotellable ball and socket connector revealed that the ball exhibited abnormal wear, with a diameter deviation of approximately 0.3 mm, exceeding the 0.1 mm limit specified in the manufacturer's maintenance instructions. Furthermore, the investigation found that the assembly had been in service for over 30 years, significantly exceeding the 10-year or 3,000-hour replacement limit introduced by the component manufacturer. The investigation also noted that the pilot had not utilized a locking pin to secure the connection, a practice that was not mandatory under French regulations at the time, though recommended by EASA.
Findings
- The primary cause of the accident was the disconnection of the elevator ball and socket connector, which led to the loss of pitch control.
- The elevator ball showed abnormal wear that had not been detected during the previous annual inspection.
- The component had far exceeded its recommended service life, as the periodic replacement criteria had not been effectively communicated to the operators of this specific aircraft type.
- The absence of a mandatory requirement to use a locking pin contributed to the failure to secure the control connection.
- A breakdown in the distribution of maintenance updates meant that the aircraft's maintenance manual did not include the latest instructions regarding the sphericity of the ball or the mandatory replacement interval.