The captain of the crashed Air India jet is likely to have cut off the fuel supply before it went down in Ahmedabad, US officials believe.
The first officer, who was flying the Boeing 787-9, questioned why the captain had moved switches to the cut-off position, according to a US assessment of the black box data.
The first officer reportedly expressed surprise and panic while the captain remained calm, the Wall Street Journal reported.
All but one of 242 people on board the Boeing 787 Dreamliner were killed when the aircraft plunged into a medical student hostel in a built-up suburb last month, less than a minute after take-off from Ahmedabad airport.
It follows a preliminary report released by Aircraft Accident Investigation Bureau’s (AAIB) that found that switches controlling fuel flow to the jet’s two engines were turned off, leading to a catastrophic loss of thrust at take-off.
According to the report, one of the pilots is heard asking the other why “did you cut off” the fuel supply in the recovered cockpit voice recording. The other pilot responded that he “didn’t”.
It was not previously clear who said what. However, sources in the US who have reviewed the cockpit voice recordings told the Wall Street Journal that it was the captain who was questioned about why he cut off fuel to engines.
The switches were moved in succession, one second apart, according to the report. Some 10 seconds later, the switches were turned back on. The report did not say whether the switches may have been turned off accidentally or deliberately.
Sumeet Sabharwal, the captain, and Clive Kundar, the co-pilot had more than 9000 hours of flying time between them.
On Sunday, the Telegraph revealed that Air India crash investigators were examining the medical records of Sabharwal amid claims that he suffered from depression and mental health problems.
Sabharwal, 56, had been considering leaving the airline to look after his elderly father following the death of his mother in 2022.
In the moments before the disaster, Sabharwal issued a mayday call. However, after the aircraft reached a maximum altitude of barely 400ft above the runway, all contact was lost. The plane then fell towards the ground and exploded on impact.
Campbell Wilson, the Air India chief executive, said in a staff memo that the report had “triggered a new round of speculation in the media”.
Wilson said the report neither identified any cause nor made any recommendations and urged people to avoid drawing premature conclusions as the investigation was far from over.
Indian media, however, reported that investigators were examining potential electrical and digital faults that could have triggered “uncommanded” actions.
“The probe will ascertain the possibility of an ‘uncommanded transition’ of the fuel control switches to the cut-off mode seconds after the lift-off,” an official aware of the investigation was reported to have said.
Just hours before take-off, a pilot flying the same aircraft from Delhi to Ahmedabad noted in the technical log a “stabiliser position transducer defect”, the newspaper said.
The stabiliser position transducer is a sensor that controls the up and down movement of the aircraft’s nose, and transmits the data to flight control systems. The official said the malfunction was checked and the engineer did the troubleshooting.
“The malfunction is a critical issue as it can trigger incorrect responses in flight control, including unintended fuel cut-off signal,” the official was quoted as saying.
There had been at least two more similar incidents on the aircraft in the weeks before the crash, the newspaper said.
One involved a false fuel system warning that flashed on the screen of the plane’s control panel. Another was an electrical fault that led to the cancellation of a flight.
The official added that the aircraft had previously experienced two major problems, including an emergency landing in 2015 because of a cabin air compressor issue.
The Federation of Indian Pilots has expressed dissatisfaction at pilot representatives being excluded from the investigation process, saying: “We also firmly object to the way in which the preliminary report has been interpreted and presented publicly.”
Captain C S Randhawa, the federation’s president, said: “The report, as released, lacks comprehensive data and appears to rely selectively on paraphrased cockpit voice recordings to suggest pilot error and question the professional competence and integrity of the flight crew.
“This approach is neither objective nor complete. Assigning blame before a thorough, transparent, and data-driven investigation is both premature and irresponsible.”
The crash was the first fatal accident involving Boeing’s Dreamliner. However, the airline had already suffered reputational damage after a string of safety and quality problems.
The Dreamliner, which entered service in 2011, is popular among commercial airlines and is commonly used on international long-haul routes.