OPERATIONS MANUAL

Automatic Flight
MCP:
Vertical navigation switch
Push If VNAV mode is armed:
Disarms VNAV mode.
If VNAV is not armed and not engaged:
Arms VNAV mode.
When armed or engaged, switch light illuminates and
PFDs annunciate VNAV in white (armed) or green
(engaged).
Armed VNAV will automatically engage when all of
the following conditions are true:
+ Aircraft is above 400 ft.
+ Three or four engines are running.
+ Master FMC is operative.
+ Gross weight, cost index, and cruise altitude are
entered in FMC.
+ IRS is aligned.
+ Pitot/static and TAT probe heat power is available.
When VNAV SPD is engaged:
AFDS commands pitch to maintain command speed,
while A/T is engaged in THR, THR REF, IDLE, or
HOLD.
When VNAV PTH is engaged for descent:
AFDS commands pitch to maintain predicted descent
profile and to remain within +15 and -10 kt of
command speed (±10 kt when below 10000 ft), while
A/T is engaged in THR, IDLE, or HOLD mode when
on idle path; or SPD mode when on approach.
When VNAV ALT or VNAV PTH is engaged in level
flight:
AFDS commands pitch to maintain target altitude,
while A/T is engaged in SPD.
When aircraft is between FMC target altitude and
MCP altitude with any VNAV mode engaged:
AFDS commands pitch to maintain current altitude
until conflict is cleared by resetting the MCP or FMC.
If command speed exceeds airspeed limit, VNAV uses
respective minimum or maximum airspeed.
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