*
Hardware monitors valid
*
ADIRU data valid
*
Other FMCF active
*
LNAV captive criteria
*
Active FMCF
*
Active route
*
50 feet above ground level (AGL)
*
LNAV arm/operate input set
*
Not localizer mode active
EFFECTIVITY
BEJ ALL
* Not go-around mode active.
This is the LNAV capture criteria:
*
A crosstrack distance of 2.5 nautical miles or less or a crosstrack distance from which the guidance sub-function can initiate path capture when on an intercept heading. Path capture is a function of ground speed intercept angle and bank angle (25 degree maximum)
*
Intercept heading -the current aircraft heading intercepts/ crosses the active leg.
The active FMCF sends the LNAV engage status to the guidance sub-function and display sub-function. LNAV engages for these flight phases:
*
Climb
*
Cruise
*
Descent
*
LNAV approach.
Localizer capture cancels or inhibits LNAV operation. Go-around start also cancels LNAV operation.
The LNAV guidance sub-function receives navigation partition data from the inactive FMCF when its navigation partition fails.
VNAV Engage Logic
These are the other inputs for VNAV engage logic:
* Software monitors valid
34-61-00
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FMCS -FMCF FUNCTIONAL DESCRIPTION -LNAV AND VNAV ENGAGE LOGIC
*
Hardware monitors valid
*
ADIRU data valid
*
Other FMCF active
*
Active FMCF selected
*
Active route
*
VNAV arm/operate input set
*
Performance data valid
*
400 feet above ground level (AGL)
*
Not glideslope mode active
*
Not go-around mode active.
The VNAV engage logic also gets inputs about the climb, cruise and descent flight phases. The VNAV engage logic uses this data to engage into the VNAV SPD or VNAV PATH mode.
The active FMCF sends the VNAV engage status to the guidance sub-function, speed and altitude intervention logic, and the display sub-function. VNAV engages for these flight phases:
*
Climb
*
Cruise
*
Descent
*
VNAV approach to glideslope capture.
Glideslope capture cancels or inhibits VNAV operation. Go-around initiation also cancels VNAV operation.
The VNAV guidance sub-function does not receive VNAV sub-function data from the inactive FMCF when its VNAV sub-function fails. In this case, the FMCF fails.
EFFECTIVITY BEJ ALL 34-61-00
Page 98.80
D633W101-BEJ May 05/2003
FMCS -FMCF FUNCTIONAL DESCRIPTION -LNAV AND VNAV ENGAGE LOGIC
EFFECTIVITY BEJ ALL 34-61-00
Page 98.81
D633W101-BEJ May 05/2003
FMCS -FMCF FUNCTIONAL DESCRIPTION -VNAV SPEED AND ALTITUDE INTERVENTION ENGAGE LOGIC
General
The active FMCF sends speed and altitude targets to the autopilot flight director system (AFDS). The FMCF sends speed targets to the thrust management computing system (TMCS) in cruise. The flight crew can change the speed (speed intervention) and altitude (altitude intervention) targets with a switch selection and a manual entry.
Speed Intervention
The guidance sub-function sends speed commands to the AFDS to control speed. The mode control panel (MCP) IAS/mach window blanks the display when VNAV SPD engages.
VNAV speed intervention lets the operator override the active FMCF speed target. To do this, push the IAS/mach selector on the MCP. The window then shows the FMCF target airspeed. Turn the selector knob to change the target airspeed.
Push the selector again to make the window go blank. The active FMCF then uses the FMCF target airspeed.
Altitude Intervention
The active FMCF sends altitude commands to the AFDS. The active FMCF uses the altitude window and altitude selector to do these functions:
*
Remove altitude constraints
*
Change the FMCFs cruise altitude
* Capture the MCP altitude.
Altitude constraint removal occurs when the MCP altitude is higher than the constraint altitude in climb or lower than the constraint altitude in descent. To do this, push the altitude selector. Each push of the altitude selector removes one constraint between the airplane and the MCP altitude.
Set a new cruise altitude above or below the current airplane altitude. Altitude intervention in cruise occurs with a push of the altitude selector on the MCP. This causes the airplane to go in the direction of the altitude change. This also causes the present cruise altitude to change to the MCP altitude.
MCP altitude capture occurs when the airplane attempts to fly through the MCP altitude in climb and descent or away from the MCP altitude in cruise. In these conditions, the active FMCF gives a VNAV altitude hold command. This causes the airplane to fly to and capture the MCP altitude. This occurs when the AFDS VNAV mode is active. Annunciation of the VNAV ALT mode shows on the primary display system.
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