787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Controls -
System Description
Copyright © The Boeing Company. See title page for details.
9.20.22 D615Z003-TBC
Cruise Flaps
Cruise flaps is an automated function that improves the airplane’s cruise
performance by symmetrically moving the flaps, ailerons, flaperons, and spoilers
based on airplane parameters such as weight, airspeed and altitude. Cruise flaps
optimizes performance in cruise by varying the camber of the wing and thus
reducing drag. Control surface movements are minor and no pilot interaction is
required. The EICAS advisory message CRUISE FLAPS SYS is displayed if the
system fails with the flaps in an increased drag condition.
Cruise flaps are only available in the Normal mode.
Flap and Slat Asymmetry Detection
In primary and secondary modes the flap and slat systems are designed to
shutdown when a skew condition or asymmetric deployment is detected. When
the system is shutdown, the corresponding EICAS caution message FLAPS
DRIVE and/or SLATS DRIVE is annunciated.
Uncommanded Flap or Slat Motion
Uncommanded motion is detected when the flaps or slats:
• move away from the commanded position
• continue to move after reaching a commanded position
• or move in a direction opposite to that commanded
If the flap or slat is operating in the primary mode, uncommanded motion first
causes an automatic transfer to the secondary mode. The EICAS caution message
FLAPS PRIMARY FAIL and/or SLATS PRIMARY FAIL is displayed. If motion
continues, the system shuts down. The EICAS caution message FLAPS DRIVE
and/or SLATS DRIVE is displayed.
Flap or Slat Disagree
A disagree is detected when the flaps or slats do not move or move too slowly after
a commanded input. If the flap or slat is operating in the primary mode, and the
rate of motion is less than half the normal rate, an automatic transfer to the
secondary mode occurs. The EICAS caution message FLAPS PRIMARY FAIL
and/or SLATS PRIMARY FAIL is displayed. If motion continues at less than half
the normal rate, the system shuts down. The EICAS caution message FLAPS
DRIVE and/or SLATS DRIVE is displayed.
Flap Indications
Flap position indications are displayed on the primary EICAS display. In primary
mode a single vertical indicator displays combined flap and slat position. The
position commanded by the flap lever is also displayed. Ten seconds after all flaps
and slats are up, the entire indication is no longer displayed. A loss of position
sensing removes the tape fill and flap lever position indications.
February 15, 2010
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