Air NZ jet cleared for takeoff after birdstrike suffers engine failure
An Air New Zealand Airbus A320 cleared to fly after a birdstrike at Wellington International Airport suffered engine failure on its next flight.
It was approaching Auckland Airport on June 20, 2012, when the right engine failed, a Transport Accident Investigation Commission (TAIC) report found.
The captain reduced the engine thrust to idle and continued with the landing, the report said.
"Although damaged internally, the engine continued to run and was used during the landing."
The Wellington bird strike - the bird was a black-backed gull - did not affect the landing.
Maintenance engineers inspected the engine and released the aircraft the same day for a flight to Auckland with 167 passengers, and five five crew members.
As the birdstrike involved only one engine and no damage was found, the aircraft was allowed one more take-off and landing, before a more intense inspection.
It flew to Auckland under this "continued operating allowance".
Approaching Auckland, the same engine failed but continued to run and was used during the landing.
An inspection found damage caused by the bird being ingested into the core of the engine.
A crack in a compressor blade hit by the bird grew further under the stress of the next flight.
It fractured completely and caused significant damage to other components as it passed through the jet engine.
It was the first reported occurrence worldwide where a V2500 engine had failed while operating under the continued operating allowance having had a bird strike down the engine core, TAIC said.
After reviewing the decision to continue operating the engine, TAIC found that the resultant risk to aviation safety was reasonable, so made no recommendations.
"The aeroplane systems would normally have generated automatic reports to the operator's maintenance operations control during the flight, which could have alerted it that the damage to the engine from the birdstrike was worse than initially thought. However, these did not reach the control centre as intended. The reasons that gave rise to this have now been rectified," it said.
TAIC also reviewed the Wellington Airport measures to control bird life, and found these met industry best practice.
Although the safety of the aeroplane and the persons on board was not unduly compromised by releasing it to service, operators needed to balance the cost of having inspection services available at key airports with the cost of an engine failure of this scale, it said.