Engine SGR
B737-700/800/900 Engine
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 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.
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.
Engine Ignition 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.