Preliminary investigations by the aviation authorities have indicated that pilot's navigational error could be the most likely cause of the crash. But the air traffic control tower's role has also come under the scanner for failing to warn the pilot that he had veered off the flight path.
“It could be even a combination of both,” a member of the investigation board appointed by the government told Dawn and added that technical failure might be another contributing factor.
Capt Pervez Iqbal Chaudhry, the pilot of flight ED202, who was in his mid-sixties, had a lot of flying hours under his belt. But his co-pilot, First Officer Muntajib Chughtai, was new to commercial flying.
The investigations so far have established the circumstances surrounding the crash and are now looking at what caused the pilot to deviate.
The aircraft, Airbus A321, had started its landing approach for Runway 30, one of the two runways at the Islamabad airport, but because of wind direction the pilot had to turn right for 'circling' the jet towards Runway 12 -- something normal for flights landing in Islamabad during monsoon.
As the plane started preparations for landing on Runway 12 it had descended to about 2,500 feet and was flying parallel to the runway over Islamabad highway.
The pilot was attempting visual landing at Runway 12 because the instrument-assisted landing is available only on Runway 30. Visual landing entails eye contact with the runway.
Pilots said the mandatory conditions for 'a circling approach' are to keep a minimum altitude of 2,500 feet; remain within 2-3 miles of the runway; and maintain a visual contact with the airstrip at all times.
Aviation experts opined that the aircraft's altitude was correct, but the pilot could have faulted on the other two conditions as he continued his 'dormant flight' and flew much farther than the mandated distance from the runway. The best option, in such a case, they said, could have been 'to go round' and make a fresh attempt for landing.
There were some indications that the pilot had made a belated effort to 'pull up', but probably it was too late.
Sources privy to the probe said that after the air traffic controllers noted that the pilot of ED202 was going for an unusual 'wider approach' beyond the allowed course and had failed to take the final 'base turn' towards left, approximately over Faizabad interchange, they advised two other aircraft, belonging to Shaheen Air and Pakistan International Airlines, which were positioning themselves behind the doomed plane for landing at Islamabad airport, to slow down.
But the question remains that why wasn't Capt Chaudhry alerted by the tower that he was going out of range and getting too close to the hills that are about 10 nautical miles away from the airport. The pilot had flown at least six miles beyond the minima for the circling approach.
The radar had noticed the deviation and had warned the traffic controllers, a source disclosed.
“Probably there was a communication breakdown,” one of the controllers assumed, but wasn't sure about the actual cause of the failure.
The plane that crashed at about 9.45am had last contacted the tower at 9.43am.
There were no 'May Day Calls' -- distress signal -- from the pilot either, which an aviation expert said made it a perfect CFIT (controlled flight into terrain) case. CFIT is used to describe an accident in which an airworthy aircraft, under pilot control, is unintentionally flown into the ground, a mountain, water or an obstacle.
The investigators are wondering whether or not the aircraft's Ground Proximity Warning System (GPWS) worked.
This may come to light once the plane's flight data recorder, commonly known as 'black box', is recovered and analysed.
TECHNICAL FAILURE But apart from a possible pilot error, there is also a growing body of evidence that a technical malfunction could have led the pilot into navigational error.
The fatal mistake by the pilot in continuing towards Margallas, instead of turning left while circling for Runway 12, was not the first. The aircraft had during its descent into Islamabad airport strayed into Kahuta area but was corrected by the control tower. The pilot had then switched over to the navigational system -- Flight Management System -- instead of utilising the radar facility.
WEATHER Although the debate on cause of the crash has focussed on inclement weather, experts say it was good enough for landing, even for visual one.
The weather conditions close to the crash site were wind 050 degrees at 16 knots; visibility at 2,000 metres; cloud base at 1,000 feet; and rain.
The minimum conditions for landing are 500m visibility and cloud base of 500 feet.
The government has appointed a five-member commission to probe the crash. Air Commodore Khawaja Abdul Majid, chief of the Civil Aviation Authority's safety investigation board, will head the commission.
Tahir Siddiqui adds from Karachi The Airblue said that there was no technical fault in the aircraft, putting the crash down to weather.
Raheel Ahmed, a spokesman for the airline, told Dawn that the plane was no more than eight years old and had no known technical problems.
The Pakistan Airline Pilot Association (Palpa) also said that the plane appeared to have strayed off course, possibly because of weather.
Palpa President Captain Sohail Baloch attributed the accident to the pilot's fatigue.“The pilot may have been suffering from accumulated fatigue because they are not given adequate leaves,” he said, adding that the flight route was not a no-fly zone, as was being speculated.
The plane probably exceeded the safety distance because of bad weather and the pilot might not have determined an appropriate landing route.
The airline spokesman said that the aircraft, made in 2000, was leased to the Airblue in January 2006 and it accumulated about 34,000 flight hours during some 13,500 flights.
The airline, which began operations in 2004 with a fleet of Airbus A320 and A321 aircraft, operates flights within Pakistan as well as to the United Arab Emirates, Oman and the United Kingdom.
The only previous recorded accident for Airblue was a tail-strike in May 2008 at Quetta airport by one of the airline's Airbus A321 jets. There were no casualties and the damage was minimal.
The private airline operates six aircraft from its A320 family of short-haul and medium-haul aircraft. The aircraft have a seating capacity of 185.
The Chairman of Airblue, Shahid Khaqan Abbasi, who is at present in London, expressed grief over the crash and said that the matter was being probed.
Our Staff Reporter in Lahore adds An air traffic controller said “non-functioning” of the GPWS might have been the main reason for the crash.
“The GPWS, installed in every plane, is a system that alarms the pilot when the plane descends to a low altitude,” Arif Ali Khan, president of the Air Traffic Controllers Guild, told Dawn.