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 9.20.11
The autothrottle can support stall protection if armed and not engaged. If speed
decreases to near stick shaker activation, the autothrottle engages in SPD mode
and advances thrust to maintain minimum maneuvering speed (approximately the
top of the amber band) or the speed set in the mode control panel speed window,
whichever is greater. The EICAS caution message AIRSPEED LOW is displayed.
Note: When the pitch mode is FLCH or TOGA, or the airplane is below 400 feet
after takeoff, or below 100 feet radio altitude on approach, the autothrottle
does not automatically engage.
Note: During a descent in VNAV SPD, the autothrottle may activate in HOLD
mode and does not support stall protection.
For additional information on PFD flight mode annunciations, mode control panel
and autothrottle operation, refer to:
• MCP Mode Selection
, Ch. 4, Sec. 20
• AFDS Flight Mode Annunciations
, Ch. 4, Sec. 20
Overspeed Protection
Overspeed protection reduces the likelihood of inadvertently exceeding VMO or
MMO by providing enhanced crew awareness of the approach to an overspeed
condition.
Overspeed protection limits the speed to which the airplane can be trimmed. At
VMO/MMO, the trim reference speed is limited by inhibiting trim in the nose
down direction. The pilot must apply continuous forward column pressure, at
twice the normal force, to maintain airspeed above VMO/MMO.
Tail Strike Protection
During takeoff or landing, the PFCs calculate if a tail strike is imminent and
decreases elevator deflection, if required, to reduce the potential for tail contact
with the ground. Activation of tail strike protection does not provide feedback to
the control column. Authority is limited so that pilot input can override its effect
and rotate to tail contact attitude via additional column force. Protection does not
degrade takeoff performance and is compatible with the autoland system.
Elevator Variable Feel
The PFCs calculate feel commands based on airspeed. In general, control column
forces increase:
• as airspeed increases for a given column displacement, or
• as column displacement increases
February 15, 2010
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