Nepalese investigators have detailed the extraordinary approach path taken by a US-Bangla Airlines Bombardier Q400 before its fatal impact with the runway at Kathmandu.
Such was the erratic course taken by the aircraft in its final moments of flight that controllers at Kathmandu tower physically ducked at one point, because the Q400 was heading towards the tower in a vain, last-ditch bid to land on runway 20.
The Nepalese accident investigation commission found that evidence of difficulties emerged after the aircraft was cleared for a VOR approach to runway 02.
Owing to their being engaged in “unnecessary conversation”, says the inquiry, the pilots forgot to cancel a hold instruction in the flight-management system, only realising their error when the Q400 started turning left to enter a holding pattern.
In an effort to regain the approach path, the captain selected a heading of 027° to turn back towards the 202° inbound. But the aircraft, experiencing winds from the west, overshot the radial and continued to deviate to the east of the approach path.
The aircraft reached a point 2-3nm north-east of the VOR and the Kathmandu tower controller informed the pilots that, while landing clearance had been granted for runway 02, they appeared to be heading for the opposite-direction runway 20.
After the captain confirmed the aircraft would land on 02, the aircraft began a right-hand orbit, exiting towards the west after a three-quarter turn, before crossing perpendicular to the extended centreline of runway 20.
The tower controller instructed the Q400 to remain clear of runway 20 and to hold position, because another flight, a Buddha Air aircraft, was landing on runway 02.
After giving the Q400 the option to land on either runway, the aircraft entered another right-hand orbit, north-west of the airport. As it orbited through a south-east heading, crossing the extended centreline again, its captain stated that he could see the runway, and requested landing clearance.
The inquiry says the aircraft turned right in a late bid to regain the centreline but crossed the threshold of 20 while virtually heading west.
“Alarmed by the situation, the tower controller hurriedly cancelled the landing clearance of the aircraft,” it adds.
The aircraft then banked sharply left over the domestic apron, flying so low that the controllers, for an instant, believed it was heading for them.
“While the aircraft was turning inwards and momentarily headed towards the control tower, the tower controllers ducked down their heads out of fear that the aircraft may hit the tower building,” says the inquiry.
The Q400 missed the tower, and descended on a south-east heading towards the centre of runway 20, banking to the right and touching down on the right-hand main landing-gear, while 25° off the centreline heading, before suffering an excursion that destroyed the aircraft.
Investigators state that the landing was probably made in “sheer desperation”, with “no attempt” at executing a go-around – even though this was still possible up to the point when the aircraft struck the runway.
The inquiry details the increasing pressure on the crew, stating that they experienced a “complete loss” of situational awareness and were facing the threat of surrounding high terrain which triggered “multiple” alerts from the ground-proximity warning system.
Cockpit-voice recordings show the pilots’ conversation indicated they had entirely lost their orientation with respect to the runway, but that they did not communicate this to controllers.
As the crew manoeuvred the aircraft, during the orbits north of the airport, they subjected it to bank angles of 35-40° and descended to within 175ft of terrain.
“In spite being pilot flying, the [captain] himself was communicating with [air traffic control] the entire time, inflating his flightdeck duties in an already-overloaded situation,” says the inquiry.