E-Paper
Air India plane crash report: What happens when fuel switches flip from ‘run’ to ‘cutoff’ during takeoff
The AAIB's preliminary report into the Air India flight AI171 crash indicates that both engines lost power moments after takeoff.
A preliminary investigation into the Air India flight AI171 crash by India's Aircraft Accident Investigation Bureau (AAIB) has revealed that just seconds before the aircraft lost power and went down near Ahmedabad airport, one pilot asked the other why he had cut off fuel to the engines, an action the second pilot reportedly denied, saying, “did not do so”.
"In the cockpit voice recording, one of the pilots is heard asking the other why did he cut off. The other pilot responded that he did not do so," the preliminary report on the Air India crash said.
Also Read | Pilot association questions direction of Air India crash probe: ‘Presumes guilt’
On June 12, the Boeing 787 Dreamliner bound for London from Ahmedabad immediately began to lose thrust and sink down, according to the report on the world's deadliest aviation accident in a decade released on Saturday by Indian accident investigators.
The report mentions that both engines of the Boeing 787-8 Dreamliner shut down one second apart shortly after takeoff. This caused the aircraft to lose altitude rapidly and crash near the boundary of Ahmedabad's Sardar Vallabhbhai Patel International Airport. Investigators have ruled out any bird strike or external damage, although the cause of the fuel cutoff remains under investigation.
Also Read | Air India flight 171 crash: What AAIB preliminary report reveals – and doesn’t
Almost immediately after the plane lifted off the ground, CCTV camera footage shows a backup energy source called a ram air turbine had deployed, indicating a loss of power from the engines.
What happens when fuel cutoff switches flip from run to cutoff during takeoff?
The fuel switches had almost simultaneously flipped from run to cutoff just after takeoff. The preliminary report did not say how the switches could have flipped to the cutoff position during the flight.
Also Read | Final moments before Air India flight 171 crashed: A blow-by-blow account
Experts have said a pilot would not be able to accidentally move the fuel switches, news agency Reuters reported.
"If they were moved because of a pilot, why?" Reuters quoted US aviation safety expert Anthony Brickhouse as saying.
The switches flipped a second apart, the report said, roughly the time it would take to shift one and then the other, according to US aviation expert John Nance.
He added that a pilot would normally never turn the switches off in flight, especially as the plane is starting to climb.
Flipping to the cutoff almost immediately cuts the engines. It is most often used to turn engines off once a plane has arrived at its airport gate and in certain emergency situations, such as an engine fire. The report does not indicate there was any emergency requiring an engine cutoff.
- Immediate engine shutdown: Fuel cutoff switches control the fuel flow to engines. When moved to cutoff, fuel is instantly cut, causing a flameout— engines lose power immediately.
- Loss of thrust at low altitude: Since this happened shortly after takeoff, the aircraft had insufficient altitude or speed to glide or recover. Experts note that even if the switch is returned to run, restarting the engines takes too long at that low altitude, The Washington Post reported.
(With inputs from Reuters)
