|Philippine 137, Embedded from[http://aviation-safety.net/photos/accidents/19980322-0-C-d-1-500.jpg] on 21 September 2010||Philippine 137, Embedded from[http://aviation-safety.net/photos/accidents/19980322-0-C-d-3-500.jpg on 21 September 2010|
On the 22nd of March 1998, an Airbus A320, conducting a VOR approach into Bacolod Airport, Philippines landed approximately halfway down the runway. Upon touchdown, it preceded to veer off the runway on the right hand side. It paralleled the runway, approximately 330 feet, before returning to the runway. It overran the end of the runway and went through a fence, crossed a river and came to a rest 650 feet from the end of the runway.
Three people on the ground sustained fatal injuries. The aircraft was damaged beyond repair.
HOW DID IT HAPPEN?
The aircraft was dispatched with the number 1 engine thrust reverser inoperative. This was done in compliance with the MEL. The approach was conducted by the captain with the auto throttles engaged in the “SPEED’ mode. The power setting for the NO 1 engine was left in the climb detent. Just before touchdown, the call “RETARD” was called five times by the first officer, as captured by the CVR. The No 2 engine thrust moved to idle but the No1 stayed in climb position. The thrust reversers were deployed but the No1 thrust stayed at climb power. As a result the spoilers failed to deploy. The FO was heard calling out “no spoilers, no reversers, and no deceleration”.
The auto throttle system disengaged when one engine was set to reverse. This led to the thrust on the No 1 to increase. The resultant effect was a loss of directional control, causing the aircraft to veer of the runway. It then proceeded to swerve back onto the runway, continued past the runway, hitting the perimeter fence and coming to a stop in some houses and trees.
FINDINGS BY THE PHILIPPINES CIVIL AERONAUTICS BOARD:
The Philippines CAB determined that the cause of the accident was the inability of the captain to control and assess the situation of the aircraft on touchdown. This inability to assess, with No 1 engine thrust reversers inoperative caused the extreme power differential which resulted in a runway excursion.
CONTRIBUTING HUMAN FACTOR ELEMENTS:
There was a lack of awareness on the part of the crew of the technical aspects of the MEL. They were not aware that with the selection of the reversers that the auto throttles would disconnect leading to the increase in power on one engine and ultimately extreme differential power.
The flight crew’s non compliance to the limitations on the use of full reversers, as stipulated by the MEL, led them to select full reversers leading to asymmetrical thrust setting. This then led to the runway excursion and overrun.
LACK OF SITUATIONAL AWARENESS:
The captain’s inability to recognise immediately the asymmetrical thrust setting (Level 1) led to the prolonged asymmetrical situation, which may have been mitigated if he had cancelled the reversers earlier and bringing the power back on the No 1 engine.
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