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

The Wall Street Journal reported Wednesday that a cockpit recording of the dialogue between two pilots on the Air India flight which crashed last month shows the captain cut off the fuel flow to the Boeing 787's jet engines.

Here are some facts about the engine fuel switches. They describe their function in the aircraft, and how they moved 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 engines or start engines manually on the ground.

Experts in aviation say that a pilot could not accidentally move fuel switches feeding the engines. If moved, however, the engine would immediately stop working.

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 both switches were switched to 'CUTOFF,' with an interval of 1 second. 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 report didn't identify the remarks made by either the captain or the first officer. The Wall Street Journal reported Wednesday that the first-offer asked the captain, citing sources familiar with U.S. authorities' initial assessment of the evidence found in the investigation, why he had moved the fuel switches from 'CUTOFF to'seconds after lifting off the airport.

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 moved while the aircraft is flying, each engine's system will automatically manage a relighting and thrust recovery sequence, including ignition and fuel introduction.

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

(source: Reuters)