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the start for any of the following malfunctions:
Note: The autostart system does not monitor oil pressure or N1 rotation.
If the EEC detects no EGT rise, it cuts off fuel and ignition. The engine motors for
30 seconds. The EEC applies fuel and ignition to both igniters for another attempt.
The EEC makes three attempts before aborting the autostart sequence. The engine
motors for 30 seconds before the start and bleed air valves close.
If there is an EGT rise, but the EEC detects an impending hot start or a hung start
before starter cutout, it cuts off fuel, adjusts the fuel schedule, then reapplies fuel
for another attempt. The EEC makes three attempts before aborting the autostart
sequence. Fuel and ignition are cut off. The engine motors for 30 seconds before
the start and bleed air valves close.
If the EEC detects an impending hot start or a hung start after starter cutout, the
autostart sequence is aborted immediately. The engine does not motor.
In-flight Autostart
During in-flight flameout and/or start, the EEC reacts to a hung start or to EGT
reaching the takeoff limit. The crew reacts to a hot start or no EGT rise. If the EEC
detects the EGT reaching the takeoff limit or a hung start, it cuts off and then
reapplies fuel. The EEC allows the EGT to increase past the ground/single engine
in-flight start limit to the takeoff limit before cutting off fuel. The autostart
sequence is not automatically aborted. The EEC continues making start attempts
until the engine stabilizes at idle or the Fuel Control switch is moved to CUTOFF.
Manual Start
The Autostart switch must be OFF to accomplish a manual start. The start is
accomplished in accordance with the Manual Engine Start procedure (refer to
Chapter SP.7). Ignition and fuel are provided as soon as the Fuel Control switch is
positioned to RUN. The start must be monitored until the engine stabilizes at idle.
Engine Ignition
Each engine has two igniters. The igniters operate separately or together as
selected by the Auto Ignition selector and the EEC.
• hot start
• hung start
• noEGTrise
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
7.20.8 D6-30151-425
Engines, APU -
Engine System Description
Ignition is selected for each engine when the related Start switch is out, nacelle
anti-ice is on, or a flameout is detected. Ignition is selected for all engines when
trailing edge flaps are out of the up position or the Continuous Ignition switch is
ON.When ignition is selected, the selected igniter on each engine energizes when
the related Fuel Control switch is in RUN and, during autostart, when commanded
by the EEC. The selected igniter deenergizes when the Fuel Control switch is
placed in CUTOFF.
The AC power system is the normal power source for ignition. The standby power
system provides a backup source. When the Standby Ignition selector is in
NORM, the AC power system supplies power to the selected igniters. If the AC
power system is not powered, the standby power system supplies power
continuously to both igniters. When the Standby Ignition selector is in 1 or 2, the
standby power system supplies power continuously to the related igniter
regardless of Auto Ignition selector position or EEC selection.
October 1, 2000
747 Operations Manual
Engines, APU -
Engine System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 7.20.9
Engine Start and Ignition System Schematic
ENGINE
FUEL
VALVE
1 2
CUTOFF
RUN
FUEL CONTROL
3
VALVE
SPAR
EN 3 VLV
STARTER CUT UT 3
START
NORM
ON
3
STBY IGNITION AUTO
CON
1 2
START
BOTH
SINGLE
ON
AUTOSTART
ENGINE
CONTROL
ELECTRONIC
O
G
FUEL
BLEED
AIR
VALVE
AIR
START
UNIT
FUEL
METERING
VALVE
START
STARTER
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
7.20.10 D6-30151-425
Engines, APU -
Engine System Description
Engine Fuel System
Fuel is supplied under pressure from pumps located in the fuel tanks. Fuel for each
engine flows through a spar fuel valve located in the related main tank. The first
and second stage engine fuel pumps add additional pressure to the fuel. Engine oil
heats the fuel as it flows through the fuel/oil heat exchanger. A fuel filter removes
contaminants. The fuel metering unit adjusts fuel flow to meet thrust
requirements. The fuel flows through the engine fuel valve to the engine.
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