The families of the passengers killed in the Air India tragedy last month want to know why the plane’s fuel switches were cut-off at take-off, an act which led to a catastrophic loss of trust for the aircraft.

Air India flight AI171 had barely left the runway last month when it lost momentum and crashed in a densely populated area of India’s western city of Ahmedabad, killing all but one of the 242 people on board and 19 others on the ground.

Now, a preliminary report by India’s Aircraft Accident Investigation Bureau (AAIB) has revealed that fuel supply to both engines was cut in the crucial minutes as the aircraft was ascending in the air.

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The plane’s black box data recorder showed the aircraft had reached an airspeed of 180 knots when the fuel switches of both engines were “transitioned from RUN to CUTOFF position one”, the report says.

The report says the switches were flipped within a second of each other, halting the flow of fuel to the engine.

In the audio, one pilot asks the other why he flipped the switches. The other pilot responds he did not do so.

Seconds later, the switches were flipped back on.

Both engines were able to relight, and one began to “progress to recovery”, the report said, but it was too late to stop the plane’s gut-wrenching descent.

While the report identified the problem, it did not say whether the crash was caused by a crew error, mechanical malfunction, or electronic failure.

Speaking to the UK’s Telegraph, Ameen Siddiqui, whose bother-in-law and niece died in the crash, argued it was a cover-up.

“It’s a cover-up to protect Air India and the government,” he said.

“They want to blame dead pilots who can’t defend themselves.

“How can the fuel switches end up turning off at a critical moment, either through pilot error or a mechanical fault?”

Appearing on Sunrise on Monday, former Qantas pilot Richard De Crespigny spoke about the fuel switches, saying if it was mechanical failure, it would be remarkable.

“The fuel control switches you turn them on at the start of the flight, turn them off at the end. You turn them on and off if you have to restart the engine or if there is a fire,” De Crespigny explained.

“You have to move them in flight. But to have two turn off within a second of each other is remarkable. If it’s a switch failure, it is a really remote (chance of it happening).

“I suspect there is a human error in this (tragedy). But we just don’t know.

“The investigators could release the voice transcript, so we know exactly what was said and correlate it to what happened.

“(But) they haven’t done that.

“They have left a lot open.”

Is it a cover-up?

De Crespigny was asked on his thoughts of it being a cover-up.

“If it was a cover-up, and there was a mechanical fault, then we have had two switches that are faulty turning-off within one second of each other,” De Crespigny said.

“After 10 years of this 787’s operations, this is highly (unlikely) ... Almost impossible.

“I don’t think they want to cover it up.

“They’re (just) not used to exposing all the facts and shutting down these rumours.”

Turning the fuel switches off?

De Crespigny said turning off the fuel switches would cause an aviation disaster.

“If you turned off the fuel switches, the engines would be running down within one second because you are turning off the main pumps and it’s dramatic,” he said.

“It has to be because you have to stop fuel getting to the engine if there’s a fire.

“The fuel switches were turned off and within 10 seconds they’re both turned on.

“It suggests there was some interaction, somewhere in the cockpit.

“The switches didn’t just float up or float down.”

What do the switches look like?

De Crespigny described the switches.

“They look like little mushrooms in the supermarket, button mushrooms you have to pull the switch out and move it up or down and then release it,” he said.

“It won’t move by itself or by accident.”

De Crespigny explained he did hear of one incident where the switches were faulty.

“There was a report of these switches not having a lock to secure them,” he said.

“This would mean the switch might fall down in turbulence and turn off.

“To have two doing this (during) take-off ... This is very remote.”

- with CNN