What happened
On June 1, 2022, an Alexander Schleicher ASK 21 glider, registration TC-PTA, was participating in a training flight at the KTO Karatay University landing strip. The aircraft was under the control of an instructor and a student pilot. The flight was being conducted via a winch takeoff method.
As the winch began the takeoff sequence, the pilot attempted to transition from the pitch position to an upward angle. During this maneuver, the flight controls became jammed. The instructor attempted to use the release mechanism to disconnect from the winch cable, but the aircraft was only at an altitude of approximately 3 to 4 meters when the release occurred. This resulted in a hard landing on the grass runway.
The instructor sustained one serious injury, specifically a fracture to the T11 vertebra, while the student pilot remained uninjured. The aircraft sustained light damage, including cracks to the left wingtip fin, damage to the composite nose landing gear, and damage to the main landing gear components and the elevator torque tube.
The investigation
The UEİM investigation examined the aircraft's maintenance history, the winch operations, and the flight crew's actions. The investigation revealed that while pre-flight checks indicated the controls were free and functional, a previous hard landing had occurred that had not been reported to the technical team.
Furthermore, investigators discovered discrepancies in the aircraft's maintenance logs. Specifically, a required periodic maintenance task for the avionics (WINTER Avionics Control) appeared to have been backdated in the aircraft logbook without a corresponding test report or evidence that the work had actually been performed.
Findings
- The primary cause of the accident was that the flight controls had sustained internal damage during a previous hard landing, which went unreported because no external damage was visible during the subsequent pre-flight inspections.
- The lack of reporting regarding the previous incident prevented the technical team from identifying and repairing the jammed control mechanism.
- There were regulatory gaps regarding the oversight of winch takeoff operations, including a lack of defined technical specifications for the winch and a lack of maintenance procedures for winch-related components.
- The investigation noted that the aircraft's maintenance log contained entries that appeared to have been entered retroactively to simulate completed maintenance.
- Emergency response times were noted as a concern, as the arrival of an ambulance to the site took approximately 50 minutes.