Engine Start System
Starter operation requires pressurized air and electrical power. Air from the bleed air
system powers the starter motor. The APU, an external ground cart, or the other operating
engine provides the bleed air source.
In the GRD position, the engine start switch uses battery power to close the engine bleed
air valve and open the start valve to allow pressure to rotate the starter. When the start
valve opens, an amber START VALVE OPEN alert is provided on the upper display unit.
The starter rotates the N2 compressor through the accessory drive gear system. When the
engine accelerates to the recommended value (25% N2 or max motoring), moving the
engine start lever to the IDLE position opens the fuel valves on the wing spar and engine,
and causes the EEC to supply fuel and ignition to the combustor where the fuel ignites.
Initial fuel flow indications lag actual fuel flow by approximately two seconds, therefore,
during engine start, an EGT rise may occur before fuel flow indication.
Option - Without automatic ignition
At starter cutout speed (approximately 56% N2), power is removed from the start switch
holding solenoid. The engine start switch returns to OFF, the engine bleed air valve returns
to the selected position, and the start valve closes.
Option - With automatic ignition
At starter cutout speed (approximately 56% N2), power is removed from the start switch
holding solenoid. The engine start switch returns to AUTO, the engine bleed air valve
returns to the selected position, and the start valve closes.
