737 Flight Crew Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
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11.31.26 D6-27370-866-EGP
YW273, YW274
(SB Changes YK981 - YQ456)
• the missed approach point for approaches not showing a runway
waypoint on the active RTE LEGS page, or
• the last descent waypoint, or
• the lowest “at” altitude restriction if no arrival procedure is entered.
Entering an instrument arrival procedure provides an E/D point.
If there is no E/D point, FMC predictions assume a computed profile to 1000 feet
above the destination field elevation, at a position which will vary according to
selection of arrival procedures. The FMC will provide a slowdown profile for
approach. VNAV path descent is not available if there is no E/D point.
VNAV Descent and Approach Path
The descent path starts at the calculated top of descent (T/D) point and includes
waypoint altitude restrictions. The path is based on:
After the first “at” or “at or below” restriction, the path angle is constant between
waypoints.
Note: When passing top of descent and using high target speeds (within
approximately 6 knots of Vmo/Mmo), VNAV may revert to LVL CHG to
prevent overspeed. Reduce airspeed to the VNAV target descent speed
prior to reengaging VNAV.
Normally, the target speed is economy speed above the airspeed restriction
altitude and 240 knots below that altitude, until deceleration for approach. VNAV
will not permit descent below the airspeed restriction altitude until the airspeed is
at or below the restricted value plus ten knots. The start and end of the airport
speed restriction deceleration segment is shown on the map as a green open circles
with no labels.
The descent path assumes deceleration to reach the final approach fix (FAF), or
the glideslope intercept point at VREF 40+20 knots.
Target speeds are changed by entries on the DESCENT page. Entries made on the
LEGS page are “at or below” and may limit the target speed. Wind and thrust
assumptions are changed on the DES FORECASTS page.
•idle thrust
• speedbrakes retracted
• descent wind speed
decreasing with decreasing
altitude
• applicable target speed.
September 15, 2016
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