*
Flight management function (FMF) partition.
The flight management computing function (FMCF) does these sub-functions:
*
Lateral navigation (LNAV) -NAV partition
*
Nav radio tune -NAV partition
*
Vertical nav (VNAV) -FMF partition
*
Guidance -FMF partition
*
BITE/fault monitoring -FMF partition
*
Display control -FMF partition.
The active FMCF sub-function sends this data to these user systems:
*
Guidance sub-function sends LNAV and VNAV commands and mode data to the AFDS
*
Guidance sub-function sends VNAV thrust commands mode and data to the TMCF
*
Radio tune sub-function sends radio tune commands and mode data to the navigation radios
*
BITE sub-function sends fault and display data to the PDF and CMCF of AIMS
*
Display control sub-function sends page and display data to the CDUs, PDF, and CMCF of AIMS.
NAV -Lateral Navigation Position Calculation
The LNAV sub-function uses these inputs to calculate the current airplane position:
*
Air data inertial reference unit (ADIRU) inertial data
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Global position system (GPS) position data
*
Navigation data base (NDB)
*
Nav radio data.
The LNAV sub-function sends these outputs to the VNAV and guidance sub-function for the autopilot flight director system (AFDS):
*
Position and velocity data
*
Flight path data
*
Heading and track data.
NAV -Nav Radio Tune
The nav radio tune sub-function allows autotune and manual tuning of the navigation radios. The FMCF uses the autotuned radios for position update. The flight crew uses the data to verify their position.
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The FMCF does not auto tune the ADF radios.
The nav radio tune sub-function receives these inputs to do its calculations:
*
Nav radio data
*
LNAV data
*
NDB
*
CDU requests.
The nav radio tune sub-function sends these outputs to the nav radios:
*
Tune mode
*
Tune frequency
*
Identifier
*
Course
*
ILS course.
FMF -Vertical Navigation
The VNAV sub-function uses these inputs to calculate VNAV (pitch) commands and other display data:
*
Airframe and engine performance data from the performance data base (PDB)
*
Inertial data from the ADIRU
*
Air/ground data
*
LNAV data from the NAV partition
*
Engine data from the engine controllers
*
Fuel data from the fuel quantity system
EFFECTIVITY
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* Crew entries from the CDU performance initialization and the takeoff reference page.
The VNAV sub-function sends these outputs to the guidance sub-function for the AFDS and the thrust management computing function (TMCF):
*
Altitude
*
Vertical track (VTK)
*
Cross track (XTK)
*
Fuel used
*
Thrust limits
*
Gross weight
*
Takeoff speeds
*
Approach speeds.
FMF -Guidance
The guidance sub-function calculates steering and thrust commands. To do this, it looks at inputs from external sensors, components, and internal FMCF interfaces. The guidance sub-function compares the actual position from the LNAV sub-function with the flight plan from the display control sub-function. It compares the VNAV sub-function targets (pitch and thrust) with actual airplane pitch and actual thrust. The guidance sub-function sends roll and pitch steering commands to the AFDS.
The guidance sub-function also supplies these outputs to the AFDS:
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LNAV operate mode
*
VNAV operate mode.
It sends this data to the TMCF:
*
Thrust commands
*
Speed commands
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Thrust limit mode
*
Autothrottle mode.
The guidance sub-function also supplies these outputs to the display control sub-function:
*
Roll flight path data
*
Pitch flight path data.
FMF -BITE/Fault Monitoring
The BITE/fault monitoring sub-function contains hardware monitors, software monitors and fault detection circuits. The BITE/fault monitoring sub-function stores BITE and fault detection information and status for the last ten flight legs in non-volatile memory (NVM). It also records the status of the input source in BITE history. The BITE/fault monitoring sub-function supplies FMCF faults to the display control sub-function.
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