787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Engines, APU -
Engine System Description
Copyright © The Boeing Company. See title page for details.
7.20.10 D615Z003-TBC
The electrical system powers two starter motors mechanically connected to the N2
shaft via the accessory gearbox. During engine starts, power to run the starters is
drawn from the airplane’s electrical system. There are two power sources that can
provide starter power; the APU and the forward external power. Normally, APU
power is used to drive the engine starters.
Load shed always occurs during engine start. Shed systems appear on their
respective synoptics with the majority appearing on the electrical synoptic.
The START selectors control the starter motors. Ignition and fuel flow are
controlled through the FUEL CONTROL switches.
The EEC monitors the start and commands starter cutout when the engine reaches
idle speed. The START selector then releases to the NORM position.
In the event both starters on the respective engine fail, STARTERS displays across
the respective starter symbols on the electrical synoptic. The EICAS advisory
message ENG STARTERS L, R also is displayed. (Refer to Synoptic Indication
Symbology in Chapter 6, Section 10, for additional information.)
[Option – GE engines]
A maximum start limit line (red) is displayed on the EGT indication when the
FUEL CONTROL switch is moved to CUTOFF or engine N2 RPM is below idle
and the respective fire switch is not pulled. It remains displayed after the FUEL
CONTROL switch is moved to RUN and until the engine is stable at idle. The
EGT indication changes color to red if the EGT start limit is reached.
[Option – RR engines]
A maximum start limit line (red) is displayed on the EGT indication when the
FUEL CONTROL switch is moved to CUTOFF or the engine is not running and
the respective fire switch is not pulled. It remains displayed after the FUEL
CONTROL switch is moved to RUN until the engine is stable at idle. The EGT
indication changes color to red if the EGT start limit is reached.
Autostart
[Option – GE engines]
Autostart allows the EEC to control fuel and ignition. The autostart sequence is
initiated by rotating the START selector to START and moving the FUEL
CONTROL switch to RUN. For in-flight windmill starts the autostart sequence is
initiated by moving the FUEL CONTROL switch to RUN.
The START selector applies electrical power to the starter motors to begin dry
motoring the engine. Moving the START selector to START or the FUEL
CONTROL switch to RUN opens the spar fuel valve. The proper sequencing of
fuel and ignition is controlled by the autostart system. With the FUEL CONTROL
switch positioned to RUN, the EEC opens the engine fuel valve and energizes the
ignitor(s) at the appropriate N2 RPM.
February 15, 2010
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