Pakistani investigators have catalogued the arrogance and poor airmanship demonstrated by an Airblue Airbus A321 captain before the twinjet crashed into high terrain during a bungled circling approach to Islamabad.

The inquiry found that the enhanced ground-proximity warning system issued 15 'pull up' warnings, among a total of 21 alerts, but the crew failed to respond.

It also determined that the first officer had tried in vain to warn the captain of danger, but that he had been subjected to humiliation, castigation and an overbearing manner during the flight.

The aircraft had lined up for Runway 30 before breaking off for the circling approach, in low visibility, to the opposite-direction Runway 12.

But the A321 strayed north-west after the crew failed to follow the prescribed course, and the captain inadvertently turned the aircraft towards mountainous terrain while attempting to correct its heading.

Evidence of poor crew co-operation had emerged at the beginning of the flight from Karachi. During the initial climb the captain "tested the knowledge" of the first officer, using "harsh words and snobbish tone", said the Pakistan civil aviation authority.

These "intermittent humiliating session" continued over the space of an hour, sapping the first officer's confidence and rendering him "quiet" and "submissive", with the result that he did not challenge the captain's subsequent violations of procedure during the flight.

The captain had a "strong fixation" for a right-hand downwind circling approach, said the Pakistani accident report, and air traffic control twice had to refuse his request for such a manoeuvre, as it was not permitted. The CAA also pointed out that the successful touchdown by a Pakistan International Airlines flight - albeit at the third attempt - probably put the captain under "further pressure" to land the Airblue jet.

After breaking off to execute the left-hand circle, the captain then took the aircraft down to 2,300ft, below the minimum descent altitude of 2,510ft. The first officer - who had logged fewer than 1,900h, against nearly 25,500h for the captain - did not challenge the breach.

The circling procedure required the jet, after the break-off, to turn left in order to track downwind parallel to the runway - displaced no more than 1.3nm from the centreline.

But the captain, in another breach of procedures, had instructed the first officer to insert four additional, unauthorised waypoints into the flight management system, effectively creating a new flightpath for the approach.

"The [cockpit] recording and flight simulation show that the captain probably decided to fly a managed approach on pre-selected [unauthorised waypoints] unbeknown to [air traffic control]," said the Pakistani CAA.

Against procedures the captain failed to maintain visual contact with the airport. The aircraft continued to fly north-west, heading for high terrain and an area of restricted airspace. This caused the terrain-warning system to begin issuing cautionary alerts, and prompted air traffic control to instruct the A321 to turn left. The first officer also verbally informed the captain of the terrain risk.

But while the captain kept dialling in a reduced heading, the aircraft did not respond because he had opted to fly the approach using the A321's 'NAV' mode.

"The pilots were unsure of their geographical position and did not seek radar help," said the CAA. "The consequent loss of situational awareness caused the aircraft to go astray."

Forty seconds before the accident the correct mode for a heading change was engaged. But by this time the requested heading had been dialled down to 086°, and the aircraft naturally took the shortest approach to this new heading - turning right instead of left, taking the twinjet towards the Margalla hills.

Despite the ground-proximity warning system sounding 'pull up' warnings, and the first officer urging the same, the captain failed to respond, instead executing extreme manoeuvres - including banking 52° - and expressing his inability to understand why the aircraft was not turning as instructed.

"The aircraft had ended up in a dangerous situation because of [the] most unprofessional handling by the captain," said the CAA. "Since the desired initiative of [the first officer] had been curbed and a communication barrier had already been created by the captain, the first officer failed to intervene, take over the controls to pull the aircraft out of danger and display required [crew resource management] skills."

None of the 146 passengers and six crew members survived when the aircraft hit the Margalla hills, some 7.3nm north of the Runway 12 threshold.

In its conclusions over the 28 July 2010 accident the CAA said the crew "failed to display superior judgement and professional skills", and added: "In their pursuit to land in inclement weather they committed serious violations of procedures and breaches of flying discipline, which put the aircraft in an unsafe condition over dangerous terrain at low altitude."

Source: Air Transport Intelligence news