What happened
On October 3, 2019, a SZD-51 glider, registration F-CAJC, was performing a local flight at the Issoire Le Broc airfield. After being towed and released at approximately 1,000 meters, the pilot was unable to maintain altitude and returned to the aerodrome. During the approach, the pilot experienced significant difficulties maintaining the aircraft's pitch. While attempting to land on the unpaved runway, the pilot was unable to flare the aircraft despite a forceful back-pressure on the stick. Consequently, the glider struck the runway with a nose-down attitude, resulting in one injury and damage to the aircraft.
The investigation
The investigation focused on the mechanical state of the flight controls and the aircraft's recent maintenance history. Investigators found that while the other flight controls were functional, the elevator was completely disconnected from the control column at the connection point near the top of the vertical stabilizer. The lower part of the forward fuselage was damaged, and the horizontal stabilizer showed a puncture near the elevator control.
Regarding the aircraft's assembly, the club's technical manager had recently overseen the reassembly of thirteen gliders following a hangar clearance. Because the regular maintenance staff were unavailable, volunteers were used for the task. The technical manager personally assembled the wings and the horizontal stabilizer but did not specifically supervise the connection of the elevator. The investigation noted that the connection mechanism for the SZD-51 elevator is uncommon and difficult to verify visually.
Findings
- The primary cause of the accident was the incorrect securing of the elevator control connection during the glider's recent reassembly.
- The pilot was unable to detect the defect during the pre-flight inspection because she had not received specific training on this particular connection mechanism, and the connection was not visually obvious.
- The reassembly process occurred under unusual circumstances, using volunteers who were less familiar with this specific aircraft model.
- The technical supervisor did not perform a specific check to ensure the elevator connection was properly locked.
- The connection mechanism involves a sliding sleeve with a locking trigger; if the sleeve is not fully seated, the trigger cannot engage, allowing the linkage to disconnect during flight.