Fuel Switch

Why in news?

Fuel control switches on Boeing 787-8 aircraft have come under scrutiny after Air India plane crash in Ahmedabad, prompting discussions about their design, operation & potential role in aviation incidents.

Fuel switch

• Function – Fuel switch controls are critical in cockpit, by which the fuel supply to the 2 engines is regulated.
• Primary purpose – During the aircraft ground operation the switch is used to start or shut down the engines.
  • In the event of an inflight emergency like engine failure or fire, switches are used to manually stop or restart an engine.
• Switch location - Placed inside the cockpit, directly below and behind throttle levers between pilots’ seats.
  •  Positioned - where pilots’ hands rest easily during critical flight phases.

• Metal Guard brackets - Deployed to prevent accidental contact or movement.
• Spring-locking system – To move a switch from RUN to CUTOFF it require lifting of switch before sliding, designed to prevent accidents.
• Operation sequence - Engine starts by moving switches to RUN mode on ground.
  • During flight - Switches remain in RUN unless an engine fire or severe failure occurs.
  • Switches moved to CUTOFF after landing or during maintenance.

• Consequences of CUTOFF – Immediately stops fuel flow to the corresponding engine, causing it to shut down, lose thrust, and disable engine-driven generators, potentially impacting electrical systems.
• Emergency use – In case of fire or critical fault, a red light cue illuminates, signaling the crew to shut down the engine immediately.
  • Moving to CUTOFF instantly stops fuel flow and disables engine generators, impacting the electrical systems

• Redundant systems - are powered and wired separately, so one failure doesn’t compromise the backup.
  • Example - Multiple independent circuits allow safe operation even if one fails.
  • Power supply - Redundant generators/ Accelerated Processing Unit (APU)/Ram Air turbine keep critical systems running.
  • Flight controls - Multiple computers compare inputs, override faulty data automatically.
• Reactivation– If switch accidentally turned off by the pilot, the aircraft’s systems try attempt an automatic engine relight and reintroduce fuel when switch turns to RUN.
• Accident causing - Is highly unlikely due to safeguards, but possible under human stress or miscommunication.
• Industry practice - Most airlines, including Air India, comply with existing safety features unless directed otherwise by regulators.

Reference

The Hindu| Fuel Switches In Aircrafts