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activates.
Early Descent
An early descent is a descent started prior to the T/D. The VNAV descent page
becomes active.
During cruise, setting an altitude below the current cruise altitude in the MCP
altitude window and pushing the altitude selector activates the DES NOW
function when the aircraft is within 50 nm of the T/D or if the MCP altitude is set
below the highest descent altitude constraint in the VNAV descent profile.
Descent
During descent, the RTE LEGS and PROGRESS pages are used to control the
lateral route. The DES page is used to control the vertical descent profile.
The additional descent pages listed below are used to:
• DESCENT FORECAST page – enter forecast wind data to aid descent
planning
• OFFPATH DES page – analyze descent performance with and without the
use of speedbrakes
Descent Page
The DES page is used to monitor and revise the descent path. Descent speeds are
economy (ECON) and selected speed (SEL). The default VNAV descent speed is
ECON. A selected speed descent is flown when speed intervention is used or a
speed is entered on the DES page. The DES page is blank with DES as the title
until an altitude constraint below the cruise altitude is entered.
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
11.43.2 D6-30151-425
Flight Management, Navigation -
FMC Descent and Approach
1 Page Title
The page title displays active (ACT) or modified (MOD) descent. Usually, the title
contains ECON for economy descent. Other fixed or selected speeds modify the
title.
The page title displays the type of descent:
• ECON – speed based on a cost index
• LIM SPD – speed based on airplane configuration limiting speed
• MCP SPD – MCP speed intervention is selected
• XXXKT – fixed CAS descent speed profile
• M.XXX – fixed Mach descent speed profile
• END OF DES - E/DAT waypoint reached if not followed by a climb
segment
Fixed or selected descent speeds are for:
• a flight crew selected speed (SEL SPD)
• a speed transition
• a speed restriction associated with an altitude constraint
• waypoint speed constraints
VNAV
AC T
- -- --- --- -- --- -- --- -- ---
/
E S P D
>
O
ECO N DE S
E / D A T
2 00
C N
S P D T R A N S
2 40 /10 000
S P D R E S T R
- -- /-- ---
F ORE CA ST
DES D IR>
A T
0/ 00
-
3 3
R U B E L
24 60
. 80 5/2 70
< OF FPA TH DE S
2 8 PE LL Y
3
4
5
6
7
8
9
1
October 1, 2000
747 Operations Manual
Flight Management, Navigation -
FMC Descent and Approach
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.43.3
2 End Of Descent At (E/DAT)
Displays end of descent altitude and waypoint.
End of descent point is a point in descent phase with the lowest altitude constraint.
Page is blank if no E/D point exists.
3 Economy Speed (ECON SPD), Selected Speed (SEL SPD)
Both CAS and Mach values display.
ECON SPD –
• economy speed based on cost index
• displays CAS and Mach values
SEL SPD –
• displays when transitioning from ECON speed into a selected speed
segment (waypoint speed constraint, SPD RESTR, or SPD TRANS)
• displays when flight crew enters speed
• valid entries are CAS or Mach value
4 Speed Transition (SPD TRANS)
Transition speed is usually 10 knots less than the destination airport limiting speed
from the navigation database.When no airport limit speed exists, the default speed
of 240 knots displays. Transition altitude is the point transition speed is active for
the destination airport. When no altitude exists in the navigation database, the
default of 10,000 feet displays.
Blanks below SPD TRANS altitude.
Deleting causes the airplane to fly economy or selected speed if not limited by a
waypoint constraint or speed restriction.
5 Speed Restriction (SPD RESTR)
Speed restrictions at an altitude higher than E/D altitude and not associated with
specific waypoints are manually entered on this line.
Displays dashes before entry by flight crew.
Valid entry is a CAS and altitude (example: 240/8000).
6 Off Path Descent (OFFPATH DES)
Push – displays OFFPATH DES page.
7 AT XXXXX
Displays the next waypoint constraint from RTE LEGS page.
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
　
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