The preliminary investigation into the Air India crash incident in Ahmedabad, which left 260 dead, has suggested that issues in the movement of engine fuel control switches may have caused the tragedy.
Following an analysis of the Boeing 787’s flight and voice data recorders, Aviation industry publication Air Current reported on Tuesday that there may have been a possibility of improper movement of fuel control switches in the cockpit.
On June 12, the London-bound AI 171 crashed into the BJ Medical College hostel building in Ahmedabad within seconds of take-off. The tragedy left 260 people, including 241 passengers and crew on board and 19 others on the ground, dead.
What are fuel control switches?
Engine fuel control switches in Dreamliner 787 (RUN and CUTOFF) are used on the ground for engine start or shutdown. The switches are located below the jet’s throttle levers and placed inside a fuel control module. The switches are surrounded by brackets to stop them from being moved by mistake. Each switch also has a metal stop lock which requires the crew to lift it before shifting position.
How do these switches function?
Moving a fuel control switch from RUN to CUTOFF in flight would cause the fuel supply to stop flowing to the associated engine. This may result in its immediate shutdown and the loss of any thrust, according to Air Current. That would also stop the two electrical generators on each engine from providing power to many of the aircraft’s systems and some of its cockpit displays.
If an engine catches fire, the fuel control switch for the affected engine would turn red to alert the crew.
However, according to reports, the advanced fly-by-wire flight control system of Boeing-787 automatically compensates for any difference in thrust coming from one of the engines.
Its flaperons, ailerons and rudder would automatically adjust to keep the aircraft flying straight. The pilots also receive a tactile cue.
Sources told Air Current that the black box data does not confirm whether the switches were moved by mistake, on purpose, or due to some other issue before or after the apparent loss of thrust.
US aviation safety expert John Cox told Air Current that a pilot would not be able to accidentally move the fuel switches that feed the engines. "You can't bump them, and they move," he said.
According to Reuters, however, the investigation has not raised any immediate concerns over mechanical failure, and there has been no bulletin to airlines recommending changes to 787 operations.
The investigation is being led by AAIB officials and includes technical members from the Indian Air Force, Hindustan Aeronautics Limited (HAL), and the National Transportation Safety Board (NTSB) from the United States, which is the official investigative agency of the country of the aircraft's design and manufacture.
The Aircraft Accident Investigation Bureau (AAIB) has already submitted the preliminary report on the AI-171 crash to the Ministry of Civil Aviation this week.
The investigation team, including members from the Indian Air Force, Hindustan Aeronautics Limited (HAL), and the National Transportation Safety Board (NTSB) from the United States, which is the official investigative agency of the country of the aircraft's design and manufacture, Boeing, and GE, successfully retrieved and downloaded data from the black boxes at the AAIB Lab.
Also, a panel of Parliamentarians will review safety in the civil aviation sector. They have also invited several industry and government officials to answer questions on Wednesday, with topics set to include the recent plane crash.
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