What happened
On June 14, 2013, a flight training mission was being conducted between Rzeszów (EPRJ) and Lublin (EPLB). The flight involved an instructor and a student pilot performing a "conveyor" type maneuver, which included a landing and subsequent takeoff from Lublin.
Shortly after departing Lublin Airport on runway 25, while the aircraft was climbing at an altitude of approximately 30 meters above the airfield, the left-side door—the side occupied by the student—opened unexpectedly. The instructor immediately took control of the aircraft to maintain stability, while the student attempted to close the door. Due to the difficulty in securing the door while in flight, the crew decided to perform an immediate landing on runway 07, landing with a wind component. After landing, the aircraft taxied to the apron, where the crew inspected the locks, mounts, and hinges.
The investigation
The investigation examined the mechanical state of the door locking mechanism and the sequence of events leading to the failure. The investigators analyzed the possibility of the door being left unlatched prior to takeoff from the initial departure point in Rzeszów. The investigation also reviewed the physical condition of the door's locking lever and the impact of aerodynamic forces during the climb.
Findings
- The probable cause of the incident was that a portion of the knee bolster caught the door locking/closing lever, causing it to release. Once released, the incoming airflow forced the door open.
- It is possible that the lever had not been moved to the fully "closed" position; if the lever was in an intermediate, unlatched position, it would have been susceptible to accidental movement.
- The investigation determined that if the door had been properly closed and the lever fully engaged, the mechanical resistance of the lock would have prevented the door from opening in this manner.
- The investigators dismissed the possibility that the door was left unclosed during the initial departure from Rzeszów, noting that an unclosed door would likely have been detected due to increased aerodynamic noise during the flight to Lublin, and would have been more likely to open on the uneven grass runway at Rzeszów rather than the concrete runway at Lublin.