Did ‘Software Issues’ Cause Faulty Readings in Crashed PIA Airbus A320?

While preliminary findings of the Pakistan government probe into the crash of PIA flight PK-8303 on May 22 in Karachi blame the pilot and an Air traffic Controller, a media report flags ‘software issues’ in the Airbus A320 aircraft that may have led to faulty readings.

A report in Dawn newspaper quoted aviators who have flown the aircraft in question, having serial ID — AP-BLD — as saying that the Flight Management Guidance Computers of that plane and two others in PIA’s Airbus fleet had software issues, which included the appearance of ‘holdover’ when they selected Karachi Airport for landing. This causes the computer to show extra ‘track miles’. The problem, they believe, could have delayed ‘top of descend’ — the point from where pilot transitions from cruise phase to descent.

The inquiry report says: “The aircraft ended up higher than the required descend profile. At Makli the aircraft was at 9780 ft and at about 245 knots IAS. In order to manage the descent and lose the additional height, ‘OPEN DES’ (open descent) mode was selected via the FCU, both autopilots were disengaged and speed brakes were extended.”

The inquiry report says the pilot had lowered his landing gear at 7,221 feet and applied speed brakes, when the aircraft was around 10.5 nautical miles away from the runway, but then pulled the gears back at 1,740 feet, followed by retraction of the speed brakes.

This action of pulling back landing gears just five nautical miles short of runway needs to be further scrutinized. There is apparently no logic for a pilot to pull back the landing gears so close to runway and that too when he is coming ‘hot and high’ (higher altitude and greater speed than what is prescribed for landing)

The Dawn report continues; there can be two scenarios — first at high ‘indicated speeds’ (AIS) of 260 knots or above, hydraulics connected to landing gear sometime get cut, secondly pilot could retract the gear because of some ‘unsafe indication’ but then forgot to deploy it again. The first scenario can be ruled out because the aircraft speed was around 245 knots, but there is a real possibility of the second situation. The pilot, however, from the events, somehow looked to be confident that his landing gears were down.

The official inquiry report states that the pilot applied the reverser. The reversers can be applied only when landing gears are down and locked. A former PIA director flight operation told Dawn: “Few things defy logic. At 7500 feet landing gear was down, then at 1700 feet they go up and pilot on touchdown applies reversers.” Touching down without lowering the landing gears was the real fatal mistake by the pilot as it caused the engines to scrub the runway.

The pilot belatedly aborted the landing after realising that he was down without his landing gears. Opting for a ‘go around’ at this stage was the second major mistake. The damaged engines were on fire and the aircraft could not keep itself in air and crashed about four minutes later.