787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Engines, APU -
Engine System Description
Copyright © The Boeing Company. See title page for details.
7.20.12 D615Z003-TBC
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 N3 RPM.
During autostart, the EEC monitors EGT, N2 RPM, N3 RPM, and other engine
parameters until the engine reaches idle speed.
During ground starts, the autostart system monitors engine parameters and aborts
the start for any of the following:
• loss of both starters
• no N1 rotation
If one of the above conditions is detected the EEC aborts the autostart sequence
without motoring and does not make a second attempt. The starters are
de-energized and the START selector returns to the NORM position. The EICAS
caution message ENG AUTOSTART (L or R) displays.
During ground starts, the autostart system monitors engine parameters and
attempts to correct the start for any of the following:
If one of the above conditions is detected the EEC turns off fuel and ignition and
motors the engine for 20 to 30 seconds (depending on the detected condition)
before making a second start attempt. The second attempt uses a reduced fuel
schedule and both ignitors are enabled. On the ground, if the second attempt fails,
the EEC cancels the autostart. Fuel and ignition are shut off and the engine is
motored to clear residual fuel. The starters are de-energized and the START
selector returns to the NORM position. The EICAS caution message ENG
AUTOSTART (L or R) displays. There is a limit of 2 start attempts per start
sequence while on the ground. In the air, the EEC does not limit the start attempts.
Note: For in–flight starts, the autostart system temporarily discontinues the start
by cutting fuel if the takeoff EGT redline limit is reached, or if a no
light–off or a hung start is detected. If one of these conditions is detected,
autostart windmill motors the engine for 30 seconds before making another
attempt. The starters are re–engaged on the following start attempt.
Autostart takes corrective action if some start problems are detected, but
does not abort the start. During the second or subsequent start attempts
autostart re–introduces fuel and ignition when the EGT falls below 200º C.
• compressor stall
• hot start
• hung start
• loss of one starter
• no EGT rise
• start time exceeds the starter
duty cycle timer
February 15, 2010
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