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747 Operations Manual
Flight Management, Navigation -
Flight Management System
Operation
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.31.31
4 Subsequent Cruise Descent
Condition: FMC in engine out mode, setting a lower MCP altitude, and pushing
the altitude selector.
Result: VNAV cruise descent at approximately 1,250 feet per minute at E/O LRC
airspeed. The thrust limit remains CON and the autothrottle adjusts to maintain the
E/O LRC airspeed. The altitude set on theMCP becomes the CRZ ALT on the EO
CRZ page.
Required Time of Arrival (RTA)
VNAV controls cruise speed to arrive at a specified waypoint within ± 30 seconds
of a specified time. The FMC displays the scratchpad message, UNABLE RTA, if
the RTA is not achievable. RTA is not available with engine out.
Data Entry Rules
Altitude Entry
Altitudes can be entered into the FMC as three digit (XXX), four digit (XXXX),
five digit (XXXXX), or flight level (FLXXX) numbers. The FMC displays
altitude or flight level entries in the proper form based on the transition altitude.
Some data lines further restrict the valid entry forms.
Three digit entries represent altitude or flight levels in increments of 100 feet.
Leading zeros are required.
Examples of three digit (XXX, FLXXX) entries with transition altitude = 10,000
feet:
• 800 feet is entered as 008 or FL008; displays as 800
• 1,500 feet is entered as 015 or FL015; displays as 1500
• 11,500 feet is entered as 115 or FL115; displays as FL115
• 25,000 feet is entered as 250 or FL250; displays as FL250
Four digit entries represent feet, rounded to the nearest ten feet. Leading zeros are
required. This form is used when the altitude does not exceed 9,994 feet.
Examples of four digit (XXXX) entries with transition altitude = 18,000 feet:
• 50 feet is entered as 0050; displays as 50
• 835 feet is entered as 0835; displays as 840
• 1,500 feet is entered as 1500; displays as 1500
• 8,500 feet is entered as 8500; displays as 8500
• 9,994 feet is entered as 9994; displays as 9990
Five digit entries represent feet, rounded to the nearest ten feet. This form is used
when the altitude exceeds 9,994 feet
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
11.31.32 D6-30151-425
Flight Management, Navigation -
Flight Management System
Operation
Examples of five (XXXXX) digit entries with transition altitude = 4,000 feet:
• 50 feet is entered as 00050; displays as 50
• 835 feet is entered as 00835; displays as 840
• 1,500 feet is entered as 01500; displays as 1500
• 8,500 feet is entered as 08500; displays as FL085
• 9,995 feet is entered as 09995; displays as FL100
• 11,500 feet is entered as 11500; displays as FL115
• 25,000 feet is entered as 25000; displays as FL250
Negative altitude entries are allowed to -1000 feet.
Airspeed Entry
Airspeeds can be entered into the FMC as calibrated airspeed, CAS, or Mach
number,M. Calibrated airspeeds are entered as three digits (XXX) in knots. Mach
numbers are entered as one, two, or three digits following a decimal point.
Data Pairs
Many CDU pages display data in pairs separated by a slash “/.” Examples of these
pairs include wind direction/speed and waypoint airspeed/altitude constraints.
When entering both values in a pair, the slash is inserted between the values.When
it is possible to enter only one value of the pair, the slash may not be required.
When entering only the outboard value of a pair, the trailing or leading slash may
be entered, but is not required before transferring to the data line. When entering
the inboard value of a pair, the trailing or leading slash must be entered before
transferring to the data line. Omission of the required slash normally results in an
INVALID ENTRY message.
October 1, 2000
747 Operations Manual
Flight Management, Navigation Chapter 11
Flight Management Computer Section 32
Copyright © The Boeing Company. See title page for details.
D6-30151-425 11.32.1
FMC Databases
The FMC contains two databases:
• performance
• navigation
The performance database supplies performance data to the flight crew. It supplies
the FMC with data to calculate pitch and thrust commands. All pertinent data can
be displayed on the CDU. The database includes:
• airplane drag and engine characteristics
• maximum and optimum altitudes
• maximum and minimum speeds
The crew can enter correction factors for drag and fuel flow to refine the database.
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