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 9.20.17
Automatic rudder trim is provided in the normal flight control mode. For pilot
awareness of any asymmetric condition on the ground or in the air, the system
automatically moves the rudder pedals to reflect the rudder position being
commanded. This trim position is also shown on the rudder trim indicator and the
flight control synoptic. If the rudder deflection is minimal, the rudder trim remains
centered. This prevents running the trim for normal situations such as to
coordinate a turn.
On landing, automatic and manual rudder trim inputs are zeroed so they do not
provide a yaw command when the airplane transitions from the air mode (sideslip
maneuver) to the ground mode (yaw maneuver).
Rudder trim is displayed on EICAS and the flight controls synoptic. The
indication on the synoptic is constantly displayed. The EICAS indication blanks
when either of the following conditions are satisfied:
• gear up for 10 seconds, or
• 60 seconds after liftoff
The EICAS rudder trim indication automatically displays if any of the following
conditions are satisfied:
• 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
• ENG SHUTDOWN L (or R)
• ENG FAIL L (or R)
• ENG THRUST L (or R)
Secondary and Direct Mode Yaw Control
Airplane yaw control is different in the secondary and direct flight control modes.
The flight control system continues to receive and process pilot control inputs and
uses simplified computations to generate flight control surface commands. The
rudder pedals command a proportional rudder deflection instead of a maneuver
command. Pedal feel forces are unchanged from normal mode and rudder
response is slightly different.
In secondary and direct modes, the rudder ratio changer is based on flap position.
With flaps up, the rudder response to pedal inputs is less than the response when
the flaps are not up.
In the secondary and direct modes:
• flight envelope protection is inoperative
• gust suppression is inoperative
February 15, 2010
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