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situations when all other available actions have been taken and terrain contact is
imminent.
EEC Idle Selection
The EEC selects minimum idle or approach idle automatically. Minimum idle is a
lower thrust than approach idle. Approach idle is selected in flight if:
• engine anti–ice is operating
• the flaps are commanded to 25 or greater
Approach idle decreases acceleration time for go–around. Approach idle is
maintained until after touchdown, when minimum idle is selected.
Engine Start and Ignition System
The engines are started using the autostart system. Autostart is the only starting
mode. There is no manual start mode.
The electrical system powers the starter motor which is connected to the N2 rotor.
The starter power source is normally the APU, but external power or another
running engine can be used.
The START selectors control the starter motors. Ignition and fuel flow are
controlled through the FUEL CONTROL switches.
787 Flight Crew Operations Manual
Engines, APU -
Engine System Description
7.20.6 Boeing Proprietary
The EEC monitors the start and commands starter cutout when the engine reaches
self-sustaining speeds. The START selector releases to the NORM position.
A maximum start limit line (red) is displayed on the EGT round dial when the
respective 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 stabilized at idle. The EGT indication changes color to red if the EGT
start limit is reached during starting.
Autostart
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.
The START selector applies electrical power to the starter motor 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.
During autostart, the EEC monitors Turbine Gas Temperature (TGT), N2 RPM,
N3 RPM, and other engine parameters until idle speed is achieved. During ground
start, the autostart system monitors engine parameters and will abort the start for
any of the following:
Note: The autostart system does not monitor oil pressure and temperature.
If a hot start or hung/stall start is detected and N2 RPM is less than starter cutout
speed, the EEC turns off fuel and ignition and motors the engine for (TBD)
seconds. Following 30 seconds of motoring and after TGT falls below (TBD)
degrees C, the EEC re-introduces fuel and ignition using both igniters. If the
second attempt fails and N2 is less than starter cutout speed, the EEC turns off fuel
and ignition and motors the engine for (TBD) seconds and until the TGT is below
(TBD) degrees C. The starter is de-energized and the START selector returns to
the NORM position. The EICAS caution message ENG AUTOSTART (L or R)
display.
• hot start
• hung start
• no EGT rise
• compressor stall
• starter shaft failure
• locked N1, N2, or N3 rotor
• insufficient electrical power for
starter operation
• start time exceeds the starter
duty cycle timer.
787 Flight Crew Operations Manual
Engines, APU -
Engine System Description
Boeing Proprietary 7.20.7
If a no light condition is detected, the EEC turns off fuel and ignition and motors
the engine for approximately 20 to 30 seconds before making a second attempt.
Following the motor period and after TGT is below (TBD) degrees C, the EEC
re-introduces fuel and ignition, using both igniters. If the second attempt fails, the
EEC turns off fuel and ignition, and motors the engine for another 20 to 30
seconds and until the TGT is below (TBD) degrees C. The starter is de-energized
and the START selector returns to the NORM position. The EICAS caution
message ENG AUTOSTART (L or R) displays).
Note: On the ground, autostart does not attempt a second start if there is no N1
rotation, insufficient air pressure, the starter shaft fails, or the start time
exceeds the starter duty cycle.
In–Flight Start
In-flight start envelope information is displayed on the EICAS display when an
engine is not running in flight or when an engine is shut down in flight and the
respective engine fire switch is not pulled. The in-flight start envelope indicates
the airspeed range necessary to ensure an in-flight start at the current flight level.
　
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