What happened
On May 22, 2023, a Cessna C-172 RG, registration SP-WLF, was conducting flight training as part of a CPL(A) program at the Depułlot Królewskie (EPCD) aerodrome. The crew, consisting of an instructor and a student, was performing their first circuit after takeoff. During the landing configuration process, the student moved the landing gear lever to the down position. While the instructor visually confirmed the extension of the right main gear, the student observed that the left main gear had failed to extend.
The crew noted a "Gear Fault" message on the Primary Flight Display (PFD1) and a lack of down-and-locked indication. The crew returned to the pattern and attempted to extend the gear several times, eventually following the emergency gear extension checklist. After notifying air traffic control, the crew performed a low pass over the runway to allow ground personnel to visually inspect the aircraft. The controller confirmed that the left main gear was hanging in an incorrect position. Following unsuccessful attempts to manually lock the gear, the crew decided to land on the grass runway. After a practice approach to runway 36L, the crew completed a full circuit and performed a safe landing at 13:38 UTC. All occupants exited the aircraft safely.
The investigation
The PKBWL examined the mechanical components of the landing gear system and the maintenance history of the aircraft. The investigation focused on the failure of the hydraulic actuator and the inspection protocols used for the landing gear assembly.
Findings
- The direct cause of the incident was a fracture of the mounting bracket for the hydraulic actuator responsible for extending and retracting the left main landing gear.
- Accelerated operational wear of the actuator occurred due to the aircraft's use in flight training, which involves a higher frequency of gear extension and retraction cycles compared to standard operations.
- Maintenance deficiencies were identified, specifically that inspections of the landing gear actuators for cracks were performed too infrequently given the high-cycle nature of training operations, and the inspection methods used did not align with the requirements of the aircraft maintenance program.