787 Flight Crew Operations Manual
DO NOT USE FOR FLIGHT
Flight Management, Navigation -
Flight Management System
Operation
Copyright © The Boeing Company. See title page for details.
D615Z003-TBC 11.31.25
If flight plan modifications or unknown winds occur when above the first speed
constraint, VNAV continues to maintain the path and allows the speed to vary up
to the following limits:
• with greater than 15 knots below the target speed, and autothrottles not
active, the CDU help window message THRUST REQUIRED displays.
The airspeed may decrease to minimum maneuvering speed. Subsequently,
VNAV commands the airplane to fly below the path to stop the
deceleration. If VNAV can no longer maintain the airplane within 150 feet
of the path without further deceleration, speed reversion occurs, the pitch
mode annunciation changes from VNAV PTH to VNAV SPD, VNAV
resets the target speed to 5 knots above the greater of best holding speed or
minimum maneuvering speed, and the CDU help window message
THRUST REQUIRED displays again. With autothrottles active, this
condition should not occur as thrust levers are in SPD and target speed is
maintained during the descent
• with greater than VMO/MMO minus 16 knots, the CDU help window
message DRAG REQUIRED displays. The airplane may accelerate up to
VMO/MMO minus 11 knots to maintain the path. If further correction is
required, VNAV may allow the airplane to rise up to 150 feet above the
path. If VNAV can no longer maintain the airplane within 150 feet of the
path without further acceleration, speed reversion occurs, the pitch mode
annunciation changes from VNAV PTH to VNAV SPD, VNAV resets the
target speed to VMO/MMO minus 16 knots, and the CDU help window
message DRAG REQUIRED displays again. The speed tape displays a
VNAV PTH speed band during descent
February 15, 2010
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