A preliminary investigation report into the Air India crash on June 12 has revealed what happened on the Boeing Dreamliner during its final moments — a 32-second journey from lift-off to its crash into hospital buildings near the airport.
The crash near Ahmedabad airport killed 241 people on board and 19 on ground. Just one passenger survived.
The report focused on the moments after the takeoff, showing the aircraft’s two fuel control switches moved to the ‘cutoff’ position in quick succession. This action cut off fuel supply to the engines, immediately causing the aircraft to lose all thrust.
The switches are on the centre console of the cockpit, just below the engine thrust levers. They are used to control fuel flow to the engines—primarily during engine start-up and shutdown on the ground, or to shut down an engine in the event of an engine failure during flight.
The fuel control switches are equipped with a spring-loaded locking mechanism that keeps them in position and prevents unintended movement. You would have to pull the switch up before moving it from run to cutoff, or vice versa.
Aviation experts say a pilot would not have been able to move the fuel switches accidentally. Once moved, the effect would be immediate, cutting off engine power.
The preliminary report highlighted key events before and after the aircraft took off. All systems were reported to be functioning normally up until the moment the aircraft became airborne.
A series of critical events unfolded in the 32 seconds after the aircraft became airborne, lost thrust and started going down — from the fuel control switches transitioning to the ‘cutoff’ position to the activation of emergency power supply units and the attempted relighting of the engines.
29 seconds before crash
(3 seconds after lift-off) Aircraft achieves the maximum recorded airspeed of 180 knots.
Immediately thereafter
The left engine fuel control switch transitions from ‘run’ to ‘cutoff’ position.
(1 second later) The right engine fuel control switch also transitions from ‘run’ to ‘cutoff’ position. The investigation report did not say
how the switches flipped.
The engines’ power begins to decrease from their take-off level as fuel supply is cut off.
Confusion in the cockpit
One of the pilots is heard “asking the other why did he cutoff”. The other pilot responds that he did not do so.
The report does not identify any of the pilots in this conversation.
24 seconds before crash
(8 seconds after lift-off) Ram Air Turbine (RAT) starts supplying hydraulic power to the aircraft after being deployed immediately after lift-off and engine cutoff.
19 seconds before crash
(13 seconds after lift-off) The left engine fuel cutoff switch.
17 seconds before crash
(15 seconds after lift-off) The air inlet door of the Auxiliary Power Unit (APU) begins opening, consistent with its auto start logic.
15 seconds before crash
(17 seconds after lift-off) The right engine fuel cutoff switch.
The aircraft was equipped to automatically restart the engines when the fuel control switches are moved from the ‘cutoff’ to ‘run’ position.
The report said:
The Exhaust Gas Temperature was observed to be rising for both engines, indicating relight. Left engine’s core deceleration stopped, reversed and started to progress to recovery.
Right engine was able to relight but could not arrest core speed deceleration and reintroduced fuel repeatedly to increase core speed acceleration and recovery.
6 seconds before crash
(26 seconds after lift-off) One of the pilots transmits “Mayday Mayday Mayday”, an emergency distress call used in aviation to signal a life-threatening emergency.
Air traffic controller enquired, did not get any response from the pilots, and then saw the aircraft crashing outside the airport boundary.
13:39:11
Aircraft’s flight data recorders stop recording.
Both fuel switches were found in the run position at the crash site.
India’s Aircraft Accident Investigation Bureau is leading the investigation into the crash. A final report is expected within a year.
By Reuters
