Prelims: Current Events of National and International Importance
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
