Engine SGR
B737-700/800/900 Engine
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 maximum 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.
At starter cutout speed (approximately 56% N2), power is removed
from the start switch holding solenoid/relay. The engine start switch
returns to OFF, the engine bleed air valve returns to the selected
position, and the start valve closes.
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 maximum 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.
At starter cutout speed (approximately 56% N2), power is removed
from the start switch holding solenoid/relay. The engine start switch
returns to OFF, the engine bleed air valve returns to the selected
position, and the start valve closes.
Engine Ignition and Start System
Each engine has two igniter plugs. The EEC arms the igniter plug(s)
selected by the ignition select switch. The left igniter plug receives
power from the associated AC transfer bus. The right igniter plug
receives power from the AC standby bus.
Each engine has two igniter plugs. The EEC arms the igniter plug(s)
selected by the ignition select switch. The left igniter plug receives
power from the associated AC transfer bus. The right igniter plug
receives power from the AC standby bus.