What happened
On 10 November 2017, a DHC-8-402 Dash 8 Q400, registration G-JEDU, was performing a commercial passenger flight from Belfast City Airport to Inverness Airport. Shortly after takeoff, the crew attempted to retract the landing gear. While the main gear retracted as expected, the nose landing gear (NLG) failed to retract properly, accompanied by cockpit warnings indicating the nose gear doors were still open.
The crew performed several abnormal checklists, including attempts to use the alternate landing gear extension system, but the nose gear remained in an unsafe position. After managing fuel levels, the flight was diverted to Belfast International Airport. During the approach, the crew prepared for an emergency landing, and the passengers were instructed to brace.
The aircraft touched down on its main wheels, and the nose was held off the runway until the speed decreased, at which point the nose gently contacted the surface. The aircraft came to a stop, and an emergency evacuation was initiated. There were 2 minor injuries among the 53 passengers, and no injuries were reported for the crew.
The investigation
Investigators examined the aircraft and found that the nose landing gear was retracted and off-centre, with the right tyre jammed against the bay wall. The forward nose gear doors had sustained significant damage and were partially detached. The investigation revealed that the nose landing gear tyres had made contact with the forward doors during the retraction sequence.
Technical analysis of the electrical system identified a damaged harness on one of the nose landing gear proximity sensors. This damage caused the sensor to send an intermittent, erroneous signal to the cockpit. This signal led the system to begin closing the nose gear doors while the gear was still in the process of retracting. The resulting physical interference between the tyres and the doors caused the gear to rotate off-centre and become jammed in the bay, which subsequently prevented the gear from extending during the landing.
Findings
- The primary cause of the incident was a fatigue failure in the electrical harness of the nose landing gear proximity sensor.
- This failure was driven by a cyclic fatigue mechanism caused by the harness being secured with a non-flexible cable tie, which prevented the wires from flexing naturally during normal gear operation.
- The damaged harness produced an erroneous signal that the system recognized as a valid state change, meaning the fault was not flagged as a system error by the sensors.
- The physical contact between the moving landing gear and the closing doors caused the gear to become misaligned and jammed.