737 Flight Crew Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
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11.31.36 D6-27370-866-EGP
• if the airplane is more than 200 feet below the vertical path, VNAV
commands zero vertical speed until intercepting the path.
• if the MCP altitude is set more than 250 feet above the current altitude,
VNAV remains in VNAV PATH
Note: Display of a specified path angle is not limited to approaches. A path angle
may be defined for a leg in a STAR and displays on the RTE LEGS page
for the procedure.
The FMC transitions out of “on approach” under the following conditions:
• selecting TO/GA
• the airplane lands
• the waypoint cycles to the first waypoint of the missed approach
• executing a direct-to waypoint in the missed approach.
The following situations are generally encountered during approach operations,
but are not determined by “on approach” logic:
• If speed intervention is engaged:
• during a path descent with flaps up on an idle or non-idle leg, VNAV
switches to VNAV SPD
• with flaps down, VNAV remains in VNAV PTH
• when a point to point (geometric path) leg is active, VNAV remains
in VNAV PTH
• while a vertical angle leg (GP x.xx on RTE LEGS page) is active,
VNAV remains in VNAV PTH
• if a vertical angle leg (GP x.xx on RTE LEGS page) becomes active,
VNAV switches to VNAV PTH without pilot action
• if on a vertical angle leg, and cross track exceeds two times the RNP
value, while LNAV is not engaged, VNAV will disengage.
VNAV will remain engaged at all flap settings, allowing approaches to be flown
using the vertical angle guidance. Speed for final approach can be set on the
APPROACH REF page.
If an ILS approach is flown in VNAV using vertical angle guidance, VNAV will
disconnect when passing the GS–XXX point if G/S is armed, but it can be
reengaged. If the GS–XXX point is deleted, VNAV will remain engaged
throughout the approach.
For an approach without a runway waypoint on the RTE LEGS page, the VNAV
path is calculated to the MDA or a calculated altitude at the missed approach
point. The calculated altitude may be below the MDA to ensure a flight path angle
and normal threshold crossing height.
Note: It is the flight crew’s responsibility not to descend below the MDA until
adequate visual contact is achieved.
September 15, 2016
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