Air India crash mystery deepens as report says fuel cut out for 10 seconds

Air India flight 171 crashed after fuel to its two engines was cut off for 10 seconds, according to an interim report into the disaster that killed 260 people in Ahmedabad last month.

But the reason why the fuel was cut remains a mystery. Was it a mechanical or computer failure, or was it done by one of the two pilots, either by accident or deliberately?

According to the report from India’s Air Accident Investigation Branch (AAIB), in a cockpit voice recording, one of the pilots asked the other why he had cut off the fuel. “The other pilot responded that he did not do so,” the report said.

The AAIB interim report was released early yesterday and gives a second-by-second account of the final moments of the Boeing 787-8 Dreamliner on its journey from Ahmedabad to London Gatwick on 12 June. The branch is legally obliged to issue a report within 30 days of the crash.

Investigators in India are continuing to gather evidence from Air India and other parties and will eventually issue a full report, although that could take a year or longer.

The plane, with 230 passengers and 12 crew on board, started gathering speed along the runway at 8:07am and its nose began lifting 58 seconds later. Three seconds after the plane was in the air, the flight data recorder shows that the switches controlling fuel supply to the engines moved to the cut-off position.

The engines lost fuel almost immediately and the turbines began to slow down, although they continued to generate enough thrust for the plane to continue its take off. At this point, the AAIB report says, one of the pilots asked the other about the fuel cut-off. Ten seconds later, the switch for engine one was turned on, and the other engine four seconds after that.

Engine one managed to relight, but the plane did not have enough thrust to continue its ascent. Thirteen seconds after the fuel was turned back on, one of the pilots transmitted a mayday signal, then the plane crashed just 32 seconds after leaving the ground. The AAIB report does not reach any conclusions as to what caused the crash.

Martin Alder, a former airline pilot and flight safety specialist at the British Airline Pilots’ Association, said: “It takes a while for jet engines to light – on the ground it can take 30 seconds from idle.”

Alder said that the fact that the two engines lost power at almost the same time meant that a software failure was a possibility, triggered by the aircraft sensors showing that the plane had left the ground.

“It’s an important message to a lot of subsystems,” he said. “So if something in that message gave an inappropriate signal to the engines, that could cause both engines to go idle.”

Another possibility is that one of the pilots flicked both of the fuel switches. The switches are meant to have a locking mechanism that means they have to be pulled out first, so it is unlikely that they would have been brushed accidentally, according to Professor Graham Braithwaite, director of aviation at Cranfield University.

It remains a possibility that one of the pilots cut off the fuel unintentionally. But although systems and cockpits are designed to prevent slips and lapses, with various layers to prevent accidents, pilots like all humans sometimes make unpredictable errors.