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What is the fuel switch at the heart of the Air India crash investigation?

Investigators' preliminary report on the Air India crash, which killed 260 people, revealed that the Boeing 787 aircraft's fuel control switches had been briefly turned off seconds after takeoff. This deprived the engines of fuel.

Here are some facts about switches, their function in the aircraft, and their movement on an Air India flight.

What are fuel switches?

These switches regulate the fuel flow to a plane's engine. Pilots use them to shut down or start engines manually on the ground, or to shut down or restart an engine if it fails during flight.

Experts in aviation say that a pilot could not accidentally move fuel switches feeding the engines. If moved, however, it would immediately cut off the engine's power.

According to John Cox, an aviation safety expert from the United States, there are separate power systems and wirings for the fuel shutoff switches and fuel valves that they control.

Where are the fuel switches located?

The fuel control switches are located under the thrust levers on a 787. In Air India's example, they were equipped with two GE engine.

The switches have a spring loaded mechanism that keeps them in place. The pilot must first lift the switch and then change it from cutoff to run.

There are two different modes: 'CUTOFF" and "RUN".

What happened on the fatal AIR INDIA flight?

According to the flight recording, after takeoff switches for both engines were switched from "RUN" to "CUTOFF", one after the other, with a gap of one sec. The engines started to lose power as a result.

On the cockpit voice recording, one pilot is heard asking the other pilot why he has cut off the fuel. The report stated that "the other pilot replied that he had not done so."

The flight's first officer and captain did not make any specific remarks.

The preliminary report states that the switches were flipped back into 'RUN" seconds later. The report said that both fuel control switches had been found in the "RUN" position on the crash site.

The report stated that when fuel control switches from 'CUTOFF to RUN' are changed while an aircraft is flying, the control system of each engine automatically manages the relighting and thrust recovery sequences for ignition and fuel injection.

John Nance, an aviation safety expert from the United States, said that "no sane person would turn off those switches in flight," particularly as the plane was just beginning to climb. (Reporting from Abhijith Gaapavaram, New Delhi; Dan Catchpole, Seattle; editing by Jamie Freed).

(source: Reuters)