Fuel switches for the engines of the Air India jet which crashed last month, killing 241 people on board, were cut off, a preliminary report into the disaster has said.
The Boeing 787 Dreamliner crashed shortly after take-off from Ahmedabad on June 12.
The report from the Aircraft Accident Investigation Bureau said three seconds after take-off, the London Gatwick-bound aircraft was climbing and accelerating with an airspeed of 180 knots (207mph), in line with normal performance.
The report says: “Immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another.” There was a one-second gap between the transition for each engine.
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The first crucial question: what caused the transition?
The report says: “In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff? The other pilot responded that he did not do so.”
Both engines were starved of fuel at the moment when power was most needed.
It took 10 seconds for one engine and 14 seconds for the other for the switches to be returned to the normal position – “transitioned from CUTOFF to RUN”.
The second crucial question: why did that take so long?
Engines can relight, but it takes time. The report says that, after the switches reverted: “Engine 1’s core deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to increase core speed acceleration and recovery.”
With the engines “below minimum idle speed” at which they could supply the necessary power, the rapid air turbine (RAT) had automatically deployed. This is an emergency device to supply hydraulic power to the aircraft’s control surfaces. But with insufficient power, the plane was doomed.
“As the aircraft was losing altitude, it initially made contact with a series of trees and an incineration chimney inside the Army Medical Corps compound before impacting the northeast wall of the Building A,” the report says.
The final death toll appears to be settled at all 12 crew, 229 passengers and 19 on the ground – totalling 260.
