737 Flight Crew Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
Boeing Proprietary. Copyright © Boeing. May be subject to export restrictions under EAR. See title page for details.
D6-27370-866-EGP 11.31.33
1 Cruise
Before the top of descent, FMC is in cruise mode and uses VNAV PTH and ECON
cruise speed.
2 Descent
After top of descent, FMC is in descent mode and VNAV changes to economy
descent speed and descends in VNAV SPD.
3 Speed Restriction Deceleration
Before the speed restriction altitude, VNAV decelerates to commanded speed
using VNAV SPD.
When at restricted speed, VNAV commands decreased pitch and descends in
VNAV SPD.
4 VNAV Path
During a speed descent, VNAV may not maintain the FMC computed VNAV path.
However, if E/D shows, a VNAV path is available.
5 Altitude Restrictions
VNAV conforms to altitude restrictions at MNO and EPG. After MNO VNAV
continues an idle thrust descent using VNAV SPD.
Upon reaching the next altitude restriction, VNAV commands level flight using
VNAV PTH. The thrust mode changes to FMC SPD.
6 Descent and Approach
After EPG, VNAV continues the idle thrust descent using VNAV SPD.
Prior to the approach, VNAV decelerates to approach speed. The FMC prompts
manual flap extension.
Vertical Angle
A vertical angle can be assigned to a waypoint from the navigation database. This
vertical angle defines a VNAV path between the waypoint and the waypoint
preceding it. This feature can be available in approaches, approach transitions, and
STARs. For example, the vertical angle for the glideslope of an ILS approach
would typically be 3 degrees. This angle is displayed on the ACT RTE LEGS page
above the speed/altitude line for the associated waypoint. Vertical angles may be
expected in any approach ending at RWXXX or MAXXX. The E/D will be
RWXXX or MAXXX, and the E/D altitude will be either threshold crossing
height (TCH – typically 50 feet above the touchdown zone elevation) or the
altitude specified at MAXXX.
September 15, 2016
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