The pilots of a passenger plane which left from Wellington and crash landed in Blenheim ignored two cockpit warning alerts as they approached the ground, a report reveals.
The Transport Accident Investigation Commission (TAIC) today released its findings on the crash of a Bombardier Dash-8 Q300 plane on September 30, 2010, which shows the pilots should have abandoned their landing attempt.
The plane, operated by Air New Zealand's subsidiary Air Nelson, had left from Wellington to Nelson Aerodrome with two pilots, one flight attendant and 43 passengers on board, but had to be diverted to Woodbourne Aerodrome in Blenheim because of poor weather conditions.
TAIC found that when the pilots moved the landing gear selector level to down, the left and right main landing gear legs extended normally, while the nose landing gear stopped before it was fully extended, probably because debris within the hydraulic fluid.
The system signalled the landing gear was "unsafe,'' since the nose landing gear was not down and locked and the gear's forward doors were open.
The pilots then began working through a checklist to troubleshoot the problem, and the system showed them green lights which verified that all the landing gear was working.
TAIC said despite this, other indicators continued to show that the nose landing gear was not locked down, leading the pilots to believe there was a fault in one of the sensors.
As they approached for landing a warning horn alerted them that it was not safe. A short time later, the ground proximity warning system also went off - but the pilots ignored both, TAIC said.
When the plane hit the ground, the nose gear was pushed into the wheel and the plane completed the landing skidding.
The damage to the aeroplane was minimal and no-one was injured.
TAIC said the primary landing gear indication system had shown correctly that the nose landing gear was not locked down, but the pilots had been misled by the verification system, which was unreliable.
The pilots should have heeded the warnings and abandoned the landing attempt, until the actual position of the nose landing gear had been determined, it said.
TAIC said Air Nelson and the aeroplane manufacturer, Bombardier, had taken a number of safety actions to address issues raised in the report.
However, as one safety issue had not been resolved, TAIC recommended the New Zealand Civil Aviation Authority (CAA) urge Transport Canada to require Bombardier to take action to improve the reliability and dependability of the down-lock verification system, it said.
TAIC believes other events involving the same nose landing gear in the weeks before the incident had probably been caused by the same condition - debris within the hydraulic fluid, but it has not been identified as the cause.
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