Investigators have disclosed that an Emirates Boeing 777-300 captain perceived the aircraft had encountered a thermal updraught, and would not be able to land in the touchdown zone at Dubai, before an ill-fated go-around attempt resulted in the jet’s crashing on the runway.
While it had already explained why the go-around failed, the United Arab Emirates’ General Civil Aviation Authority has given a detailed insight into the decision-making which resulted in the 777’s crew’s opting to abort the 3 August 2016 landing.
It states that the aircraft had been conducting a stable approach to runway 12L in a tailwind but that, during an early flare at 40ft, the captain believed a thermal updraught from the hot ground was obstructing the descent.
“We had thermal updraught coming from the ground because of the heat, so it was pushing the aircraft up, so it caused a long flare,” the captain told the inquiry. “[The aircraft] was going towards the end of the touchdown zone, so after that we decided to go around.”
Investigators reveal that the captain remarked, “Thermals”, as the aircraft reached a point 840m past the threshold, beyond the touchdown zone which is located between 305m and 610m.
But while both pilots perceived thermal effects, the inquiry points out that neither had noticed a shift in wind direction about 650m from the threshold. The tailwind had diminished and transitioned to a headwind just before touchdown, increasing the aircraft’s airspeed.
Twelve minutes prior to the 777’s arrival, the inquiry says, a Boeing 737 crew had reported light-to-medium windshear on 12L short final.
While an aircraft immediately following the 737, an Airbus A321, was informed by tower controllers about the windshear report, the four subsequent arrivals – all Emirates 777s – were not. The inquiry points out that the A321 and the 777 behind it both executed go-arounds. Two 777s then made uneventful landings before the arrival of the 777 involved in the accident.
Emirates’ policy required pilots to consider a go-around if a landing could not be achieved within the touchdown zone.
As a result, says the inquiry, the 777 captain’s go-around decision was “in line” with the carrier’s policy.
But it adds that the decision was based on the perception that the aircraft would not land due to thermals, and not as a result of a windshear encounter.
“For this reason, the [captain] elected to fly a normal go-around and not to fly the windshear escape manoeuvre,” it states.
Although the aircraft was equipped with a long-landing warning system, the captain’s declaration of the go-around immediately preceded the automated long-landing annunciation. The inquiry notes that the long-landing alert occurred 1,280m beyond the threshold – some 92m further along the runway than its programmed alert distance.
The accident sequence in the aftermath of the go-around decision had been previously established by investigators.
Owing to the aircraft’s having briefly touched down for 6s, the go-around switches were inhibited when the crew attempted to command go-around thrust. The inquiry says the crew had not been fully trained in the inhibition logic and did not check the thrust situation during the go-around attempt, failing to realise that the aircraft had become airborne with only idle thrust – which was insufficient to maintain flight.
As a result the aircraft, its landing-gear in the process of retracting, reached just 85ft in height at 131kt before descending and striking the runway, sliding to a halt before being consumed by fire. All of the occupants survived, although a firefighter attending the scene suffered fatal injuries during an explosion.