General EICAS Controls Start Ignition Fuel Oil Thrust Reverse Vibration APU EICAS Messages

Engines - Ignition (RR) Show Schematic only

Engine start system schematic Engine Fuel System Fuel Control Switch Pneumatic System Pneumatic System Ignition Selector Start Selector

The ignition system provides the means of initiating combustion for engine starting or in-flight relighting and maintaining combustion in adverse conditions. The engine ignition control is provided by the Engine Start Switch and Ignition Selection Switch.

Each engine has two igniters. Dual igniters are always used for in-flight starts.

Engine Start Panel Start Valve Light Start Valve Light Engine Ignition Switch Engine Start Switch Engine Start Switch

Main AC power (Left AC bus for the left engine ignition system and Right AC bus for the right engine) is the normal power source for ignition. Standby AC power provides a backup source.

Engine Start Switch

The Engine Start Switch, in conjunction with the Fuel Control Switch, controls power application to the ignition exciters. The Engine Start Switch also controls the Starter Control Valve. The Fuel Control Switch allows ignition to be applied at the correct time in the engine start cycle and maintains the ignition system in the armed state during engine operation

Each Engine Start Switch has five positions:

  • OFF

  • GND for engine ground start using starter assist.

    The Engine Ignition Switch is positioned to applicable igniter and the engine start switch is positioned to GND, which opens the engine Start Valve. The selector is automatically held at GND. When N3 is approximately 25% the Fuel Control Switch is positioned to RUN or RICH (depending on conditions). This completes the ignition system circuit and supplies AC power to the applicable ignition exciters. At 50% N3 RPM, the selector automatically returns to AUTO, which closes the Start Valve and terminates ignition.

  • AUTO for automatic ignition under certain conditions. Usually after the engine has been started the engine start switch is positioned to AUTO instead of the OFF position. This is to prevent engine flame-out due to loss of power when:

  • CONT for continuous ignition - no time limit.

    Continuous ignition during takeoff, landing or adverse weather conditions is provided for each engine by positioning the respective Engine Start Switch to CONT. The automatic cutoff circuit is bypassed and ignition continues until the engine start switch is turned to OFF or AUTO.

  • FLT for inflight start of a windmilling engine - no time limit.

    With the Fuel Control Switch in RUN position the Ignition Selector Switch is bypassed and both ignition systems are energised for the respective engine.

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