Incident Details
On 21 February 2018, a Bombardier DHC-8-402 departed from Warsaw Chopin Airport (EPWA) on a scheduled flight to Riga International Airport (EVRA). Approximately at 22:40 UTC, shortly after takeoff, the flight crew initiated the landing gear retraction procedure. During the retraction sequence, the nose landing gear indicator light illuminated red, and the main landing gear lights extinguished. After 15 to 20 seconds, an amber light for the nose landing gear door open indication appeared. Following another 10 to 15 seconds, the landing gear retracted normally. The crew interrupted the climb and contacted the airline's maintenance control center (MCC). After consultation, an in-flight landing gear extension test was performed; the same anomaly recurred. During the test, the nose landing gear extended but took approximately 20 seconds to lock into place. The crew decided to return to EPWA. The landing was completed without further incident.
Investigation
The operator conducted an investigation into the abnormal operation of the nose landing gear retraction mechanism. The cause was identified as a fault in the proximity sensor (part number NGDCRCL PROXIMITY SENSOR P/N: 40102-0101) associated with the nose landing gear door opening and closing mechanism.
Corrective Actions
Technical maintenance personnel analyzed the fault in accordance with the manufacturer's documentation. The faulty proximity sensor was replaced. A subsequent system test was performed successfully, and the aircraft was returned to service. The event was recorded in the operator's safety management system (SMS) database and classified according to the operator's criteria. It will be included in the operator's safety performance indicators (SPI), which are monitored as described in the Safety Management Manual. The investigating authority did not issue any safety recommendations.