787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Controls -
System Description
Copyright © The Boeing Company. See title page for details.
9.20.12 D615Z003-TBC
Secondary and Direct Mode Pitch Control
In the secondary and direct flight control modes, the flight control system
continues to receive and process pilot control inputs using simplified
computations to generate flight control surface commands. The control columns
command a proportional elevator deflection instead of a maneuver command.
Secondary and direct modes do not provide automatic pitch compensation for:
In secondary and direct modes, the elevator variable feel system provides feel
force levels based on flap position instead of a continuous variation with airspeed.
With the flaps up, the feel forces provide maneuver force levels that discourage
over control in the pitch axis at high speeds. With the flaps not up, the feel forces
decrease to provide force levels appropriate for approach and landing.
In the secondary and direct modes there is no trim reference speed. Both the
primary and alternate pitch trim switches move the stabilizer directly.
Stabilizer Operation
Stabilizer position commands are processed through two independent channels
within the flight control system. The commands come from the primary or
alternate pitch trim switches and move the stabilizer using an electric control unit
powered by the L2 and R2 AC buses.
Stabilizer Shutdown
If uncommanded stabilizer motion is sensed, the stabilizer channel that caused the
motion is automatically shut down. If a channel is inoperative due to automatic
shutdown or failure, the EICAS advisory message STABILIZER L2 or
STABILIZER R2 is displayed. The stabilizer remains operative through the
remaining channel. If the affected channel can not be isolated, both channels are
shut down.
If both stabilizer channels automatically shut down or fail, the EICAS warning
message STABILIZER is displayed. This warning is also displayed if automatic
shutdown fails to stop the uncommanded motion.
The L2 and R2 stabilizer cutout switches, located on the aisle stand, control
electric power to the independent stabilizer channels. Placing both switches in the
CUTOUT position removes all power from the stabilizer and the EICAS advisory
message STABILIZER CUTOUT is displayed. With both switches in the
CUTOUT position the STABILIZER warning message is not displayed.
• flap and speedbrake
configuration changes
• gear configuration changes
• thrust changes
• turns to 30° bank angle
• turbulence
August 14, 2009
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