Sunday, September 12, 2021

Pilot error, Air India Express' repeated systemic failures; probable cause of Kozhikode Aug 2020 crash: AAIB report

Mumbai: : The Air India Express Kozhikode landing accident that killed 21 people in August last year occurred due to the commander’s non-adherence to standard operating procedures, said the final investigation report into the accident, released by Aircraft Accident Investigation Bureau on Saturday.

On August 7, an Air India Express Boeing 737-800 aircraft, operating a Kozhikode-Dubai flight with 184 passengers, including ten infants and six crew members on board, crashed on landing at 7.41 pm. The aircraft landed in tailwind condition, touched down deep into the runway, and overshot the runway end safety area, damaged a navigation aid antenna before plunging about 110 feet down the tabletop runway where it hit the airport perimeter wall. The fuselage broke into three, the engines sheared off the wings.

``The role of systemic failures as a contributory factor cannot be overlooked in this accident. A large number of similar accidents/incidents that have continued to take place, more so in Air India Express, reinforce existing systemic failures within the aviation sector,’’ said the report, released by Capt Surender Singh Chahal, investigator-in-charge. ``These usually occur due to prevailing safety culture that gives rise to errors, mistakes, and violation of routine tasks performed by people operating within the system,’’ it said.

The Air India Express B737-800 aircraft (VT-AXH) was operating a quick return flight on sector Kozhikode-Dubai-Kozhikode under ‘Vande Bharat Mission’. The aircraft and crew had an uneventful flight from Kozhikode to Dubai. With the same crew, the aircraft departed from Dubai for Kozhikode at 3.30 pm (IST) as flight AXB 1344. The weather at Kozhikode was poor with heavy rain and strong winds, which had the pilots carry out a missed approach on the first attempt while coming into land on runway 28, said the report.

Even as the pilots were preparing for a second attempt to land on runway 28, the pilots of an Air India aircraft, departing for Delhi asked for a take-off on runway 10. The air traffic controller changed the `runway in use’, from runway 28 to runway 10, and flight operations moved in the opposite direction. What was a headwind on runway 28, now turned into a tailwind on runway 10. When the air traffic controller ``suggested runway 10 for landing.. the commander accepted without careful deliberation,’’ said the report. The controller also did not caution the pilots about strong tailwinds. Runway 10 had a tailwind of 29kmph and not 18 kmph as reported to the pilots. Aircraft land and take off in headwind. In a tailwind landing, aircraft consume a longer length of the runway to touch down and come to a halt.

Flight 1344 was now making an approach to land on runway 10, in tailwind condition. About five seconds after the autopilot was disengaged, in preparation for the landing, the aircraft deviated off a particular navigation signal that helps a plane track a safe angle of descent to land. With this, the aircraft was now on an ‘unstabilized’ approach to land. An unstabilised approach is simply an unsafe descent to land. The factors that contribute to an unstabilised approach include aircraft’s failure to adhere to the speed limits or descent rate or flight path for approach to land etc. This in turn forces the pilot to make corrections leading to an approach to land that isn’t stable and consistent.

The first officer called out the unstabilised approach and the commander initiated a correction but over-corrected in the process, the report said. The pilots should have carried out a `missed approach’__that is abort the landing, climb and return for a fresh attempt at landing. The first officer should have taken over the controls and carried out a `go-around’, the report said. A go-around is a procedure performed when a pilot isn’t entirely sure of a safe landing. The descent is aborted, the aircraft is put in a climb to return for a fresh attempt at approach and landing.

With no such action from the first officer and the commander continuing with the `unstabilised approach’, the aircraft crossed the runway threshold at 92 ft, instead of the correct threshold crossing height of 50 ft, the report said. It touched down approximately at 4,438 ft on an 8,858 ft long runway, in light rain with a tailwind component of 15 knots and a ground speed of 165 knots. The aircraft could not be stopped on the runway and this ended in a runway overrun. The aircraft exited runway 10 end at a ground speed of 84 knots and then overshot the Runway End Safety Area, breaking a navigation aid antenna and a fence before plummeting down the tabletop runway, the report said. ``The aircraft fell to a depth of approximately 110 ft below the runway elevation and impacted the perimeter road that runs just below the tabletop runway, at a ground speed of 41 knots and then came to an abrupt halt on the airport perimeter road just short of the perimeter wall,’’ it said. There was a fuel leak from both the wing tanks; however, there was no post-crash fire.

The factors that led to poor decisions:

Before operating the said flight, Air India Express had informed the commander that he had to operate the next day’s flight out of Kozhikode to Doha. ``The actions and decisions of the commander were steered by a misplaced motivation to land back at Kozhikode to operate next day morning flight. The unavailability of a sufficient number of Captains at Kozhikode was the result of faulty Air India Express HR policy,’’ said the report. ``The commander had vast experience of landing at Kozhikode under similar weather conditions. This experience might have led to overconfidence leading to complacency and a state of reduced conscious attention..,’’ the report said. ``The commander was taking multiple un-prescribed anti-diabetic drugs that could have probably caused subtle cognitive deficits..,’’ it added.
Another aspect pointed out in the report was that of aircraft maintenance. During the first approach to land in Kozhikode, the cockpit windshield wiper on the commander’s side had stopped working after operating for approximately 27 seconds while at approximately 1881 ft, the report said. The cockpit voice recorder (CVR) recorded the commander saying: “Wiper is gone...what a day for the wiper to go”. The CVR recordings revealed that the commander had given detailed instructions to the first officer about the wiper pointing to the probability of wiper malfunction instances in the past as well. “You just see that it works....remember put it to high...high speed”, the commander said to the co-pilot referring to the wiper.

The final seconds after the aircraft touched down deep into the runway point to confusion in the cockpit. The aircraft, flying at 20 feet over the runway had crossed over 1300 feet of the runway when the commander increased the engine power up to 83 %. ``This burst of additional power kept the aircraft afloat and resulted in a long landing with a touchdown at 4438 ft on the 8858 ft long runway,’’ the report said. The aircraft touched down deep, almost close to the runway midpoint. Before the thrust reversers (used to slow down the aircraft by changing the direction of the engine thrust) could take any effect, they were stowed back. ``While the reversers were being stowed, the aircraft brake pressure was momentarily reduced, decreasing the longitudinal deceleration. Thrust reversers were deployed for the second time 15 seconds after touchdown when the aircraft was at 8200 ft beyond the threshold, the max reverse thrust was commanded and the engine began to spool up,’’ the report said. At no stage, after touchdown, were the thrust levers moved forward at any time on the landing roll. The aircraft did not stop on the runway and this resulted in runway overrun.

12/09/21 Manju V/Times of India

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