What happened
On August 28, 2017, at 15:10 UTC, a Bombardier DHC-8-Q400 operated by PLL LOT S.A. departed from Warsaw Chopin Airport (EPWA) bound for Krakow (EPKT). Shortly after takeoff, during the landing gear retraction sequence, the crew observed two warning lights in the cockpit: AMBER R DOOR (indicating the right main gear door was not closed) and RED RIGHT (indicating the right landing gear was not locked in the up position).
In response to these indications, the crew performed the procedures outlined in the alternate landing gear extension checklist. The flight was diverted back to the departure airport, where an emergency landing was successfully completed without further incident or damage to the aircraft. No injuries were reported among the passengers or crew.
The investigation
The investigation focused on the mechanical state of the landing gear assembly following the flight. Upon inspection by maintenance personnel, it was confirmed that the right main landing gear door had failed to close and the right main landing gear had failed to lock in the retracted position.
Findings
Technical analysis of the landing gear mechanism revealed a fracture in the locking spring located at the gear lock. This mechanical failure prevented the right main landing gear from properly retracting and locking into the up position, which subsequently prevented the associated gear door from closing.