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.
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.
