787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Controls -
System Description
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 9.20.13
In the normal mode, when the stabilizer is manually shut down or has failed, pitch
trim is still available through the elevators. Pitch trim commands from the primary
or alternate pitch trim switches change the trim reference speed. The elevators
then trim the airplane but the stabilizer does not move.
Column Cutout
The column cutout function is designed to stop the effects of uncommanded pitch
trim input from jammed or failed pitch trim switches. If a nose up or nose down
pitch trim command from either the primary or alternate trim switches is opposed
by either control column for more than 2 seconds, the column cutout function
disables the specific pitch trim switch commands until the switch input indicates
no trim input. If the column cutout function remains active for more than 20
seconds, i.e. the trim switch remains jammed or failed, the STABILIZER L2/R2
EICAS advisory is displayed, the flight control system reverts to Direct mode, and
the uncommanded input is removed by system shutdown.
Column cutout is only available in the Normal and Secondary modes and is not
active while on the ground to allow trimming nose down stabilizer with aft column
input during a touch-and-go.
Stabilizer Position Indication and Green Band Monitor
Stabilizer position is displayed on EICAS and on the flight controls synoptic. The
EICAS stabilizer position indication includes a takeoff green band. The indication
on the synoptic is constantly displayed. The EICAS indication is displayed on the
ground at power-up and blanks when either of the following conditions are
satisfied:
• gear up for 10 seconds, or
• 60 seconds after liftoff
The EICAS stabilizer position indication automatically displays if any of the
following conditions are satisfied:
• after landing and any pair of pitch trim switches are used, or
• after landing and groundspeed is less than 40 knots, or
• in the air and any of the following EICAS messages are active:
• PRI FLIGHT COMPUTERS
• FLIGHT CONTROL MODE
• STABILIZER
• STABILIZER CUTOUT
• PITCH UP AUTHORITY
• PITCH DOWN AUTHORITY
February 13, 2009
To Next Page
Loading...
