A PRELIMINARY report has found that the fuel supply to both engines of Air India flight AI171 was cut off within a second of each other, causing confusion in the cockpit and the airplane plummeting back to ground almost immediately after taking off. The 15-page report says that in the cockpit voice recording, one unidentified pilot asked the other why he had cut off the fuel, which the other denied.

 

On June 12, the Londonbound Boeing 787 Dreamliner began to lose thrust almost immediately after taking off from the Ahmedabad airport and ploughed into a medical college hostel, killing all but one of the 242 onboard and another 19 on ground in the deadliest aviation accident in a decade. According to a chronology laid out in the report by Aircraft Accident Investigation Bureau, both fuel control switches - which are used to turn the engines off - were moved to the cutoff position almost immediately after takeoff.

 

The report however did not say how this happened or who did it. Soon after both fuel cutoff switches moved from RUN to CUTOFF, one second apart, a RAT pump was deployed to supply hydraulic power as both engines fell below minimum idle rate. About 10 seconds later, Engine 1 fuel cutoff switch moved to its socalled RUN position, followed by Engine 2 four seconds later.

 

The pilots managed to relight both engines, but only Engine 1 recovers while Engine 2 failed to build up enough power again to reverse deceleration. One of the pilots issued a “Mayday, Mayday, Mayday” distress call but before air traffic controllers could get a response about what had gone wrong, the plane crashed just outside the Ahmedabad airport boundary having grazed some trees before plunging into a hostel packed with students. At the time the aircraft took off, the co-pilot was flying the plane, while the captain was monitoring. The time between the takeoff and the crash was only about 30 seconds. The preliminary report by AAIB released on Saturday, recommended no action for now for the operators of Boeing 787- 8 planes.

 

“The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC (13.38 IST) and immediately thereafter, the Engine1 andEngine2 fuelcutoff switches transitionedfrom RUN to CUTOFF position one after another with a time gap of 01 sec,” the report said. As per thereport, the engine N1 and N2 began to decrease from their take-offvaluesas the fuel supply to the engines was cut off. “In the cockpit voice recording, one of the pilots is heard asking theotherwhydid he cutoff.

 

The other pilot responded that he did not do so,” it said. Almost immediately after the plane lifted off the ground, CCTV footage shows a backup energy source calledramairturbine(RAT)had deployed, indicating a loss of power from the engines. The report provided only a limited picture of the interaction between the two pilots in the flight deck and also did not say how the switches could have flipped to thecutoffposition during the flight. Normally, flipping to cutoff, whichalmostimmediatelycuts fuel supply, is 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 did not indicate there was any emergency requiring an engine cutoff. The report said both fuel switcheswerefoundin therun position at the crash site and that there had been indications of both engines relighting before the low-altitude crash.Ina statement,AirIndia said that it “stands in solidarity with the families and those affected” and “[continues] to mourn the loss” of those killed in the accident. Air India said it was “working closely with stakeholders, includingregulators”and“continue to fully cooperate with theAAIB andother authorities as their investigation progresses.” On its part, Boeing said: “Our thoughts remain with the loved ones of the passengers and crew on board Air India Flight 171, as well as everyone affected on the ground in Ahmedabad. We continue to support theinvestigation and our customers.”

 

The US National Transportation Safety Board noted that there were no recommended actions in the report aimed at operators of Boeing 787 jets or the GE engines.Theill-fated flightwas commanded by Sumeet Sabharwal, 56, a veteran with 30 years of experience at Air India. He had logged 15,638 flyinghours,including8,596on theBoeing 787.Hewas also an Air India instructor. His copilotwasCliveKunder, 32,who had 3,403 hours of total experience, with 1,128 on the Dreamliner. Kunder was the pilot flying, while Sabharwal was the pilot monitoring. The crew had passed preflight breathalyser tests and were seen at the gate onCCTV before they took off, the report adds.TheJune 12 accidentwas India’s worst aviation disaster inalmost threedecadesand the industry’sdeadliestin11years, as well as the first fatal involving a Boeing Dreamliner.

 

The investigation was conducted with assistance from the UK’s Air Accident Investigation Branch and the US National Transportation Safety Board. Aviation experts have said it is difficult for pilots to inadvertentlymovethe fuelswitches as there is a little mechanical gate built into the switch. Switches need to be lifted up over this little gate to shut off supply.Theyalsoaskedwhy the report made no reference to cockpit camera footage.

 

The AAIB report cited a FAA airworthiness bulletin from 2018 on the “potential disengagementof fuelcontrolswitch locking feature” on Boeing planes including the 737 and 787. The Air India jet was not inspected for the locking mechanism fault asitwasnever mandatory and that there has been no defect reported pertaining to the fuel control switch since 2023, it said.

 

It said the aircraft took off at 08:08:39 UTC (13:38:39 IST) and at about 08:09:05 UTC (13:39:05 IST) one of the pilots transmitted ‘MAYDAY MAYDAY MAYDAY’. “The ATCO (Air Traffic Controller) enquiredabout the call sign.ATCO did not get any responsebut observed the aircraft crashing outside the airport boundary and activated the emergency response,” the report said.Inthereport,AAIB also said fuel samples taken from bowsers and tanks used to refuel the aircraft were tested at the DGCA (Directorate General of Civil Aviation) Lab and were found satisfactory