AAIB investigation to DHC-8-402 Dash 8 Q400, G-JEDU
Aircraft made an emergency landing with the nose landing gear retracted at Belfast International Airport, 10 November 2017.
Summary:
The aircraft was carrying out the third sector of a four-sector day from Belfast City Airport to Inverness Airport. After takeoff, the landing gear was selected up. Cockpit indications indicated that the main landing gear (MLG) retracted normally but the nose landing gear (NLG) did not. The crew carried out the actions in the relevant abnormal checklists and were unable to lower the NLG. After burning off fuel, the aircraft was diverted to Belfast International Airport where it landed with the NLG retracted. The crew initiated an emergency evacuation.
It was determined that a damaged electrical harness on one of the nose landing gear proximity sensors caused an erroneous signal, which resulted in the forward NLG doors starting to close while the NLG was still in transit to the up position. The nose landing gear tyres contacted the forward doors, causing the NLG to rotate off-centre. Although the NLG subsequently retracted, the forward doors remained open and the tyres became jammed in the NLG bay. This prevented the nose landing gear from extending when subsequently commanded.
The damage to the harness resulted from a cyclically-driven fatigue failure mechanism, which occurred because the harness had been secured with a non-flexible cable tie which restricted it from flexing during normal nose landing gear operation. The aircraft manufacturer has taken action to clarify nose landing gear proximity sensor harness routing and attachment instructions in the Aircraft Maintenance Manual, and has published inspection requirements. Following the accident, the operator carried out an inspection of the nose landing gear proximity sensor harness routing on its Dash 8 Q400 fleet and undertook rectification of any anomalies noted. The aircraft and landing gear manufacturers are also working to identify a more flexible harness design; this activity had been initiated before the accident to G-JEDU.
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