MD-11 Flight Crew Operations Manual
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Automatic Flight -
Description and Operation
Auto.10.18
When the FMS NAV capture criteria are satisfied, the roll control window on the
FMA changes to NAV1 or NAV2 and the AFS captures and controls to the FMS
lateral flight plan in response to steering commands from the selected FMC.
The FMS steering command is limited to an optimum maximum bank angle which
also provides a stall speed and initial buffet bank angle limit. The FMS bank limit
is used by the FCC to provide bank angle limiting. Bank angle limiting is
displayed on the PFD attitude sphere.
If NAV is not engaged, and the NAV switch is pushed (aircraft within NAV
capture threshold) the FMS/AFS will momentarily cycle through the NAV
ARMED phase to verify the capture criteria. It will then annunciate NAV1 or
NAV2 and control to the FMS lateral flight plan.
NAV mode may be armed on ground once all engines are started. NAV can be
cancelled on ground by pushing the heading select knob. NAV guidance will be
available in FD at 100 feet AGL. If NAV was armed on the ground, NAV
guidance will auto engage at 100 feet in FD mode. In air below 400 feet, NAV can
be disengaged by pushing the heading select knob or pushing the GA switch.
Pushing GA switch reengages parallel rudder if the AP is engaged. The earliest
altitude at which AP NAV can be coupled is 400 feet. Below 400 feet, when NAV
is armed or engaged, the AP cannot be engaged unless NAV is exited. If the pilot
attempts to engage the AP while NAV is armed/engaged, an AP disconnect
warning will occur (AP OFF box flashes red and a CAWS warning sounds). To
clear the warning, the AP disconnect switch must be pushed or the AP engaged
above 400 feet. Below 400 feet, if the AP is engaged, NAV cannot be engaged
until above 400 feet. Parallel rudder is only available with AP engaged. If NAV is
armed on the ground, parallel rudder is not available unless NAV is cancelled.
Engaging another lateral control mode cancels the NAV mode. The NAV mode
may also be disengaged by the FMS.
FMS VOR Approach Mode
VOR control is provided by the FMC to FCC NAV steering command. The mode
is requested from the NAV radio page on the MCDU by entering a VOR
frequency and the desired VOR radial to the station.
Upon receiving the VOR mode request, the AFS is armed to capture the VOR
radial. VOR ARMED is then annunciated on the FMA.
VOR ARMED is reset by:
• Clearing the VOR course entered on the MCDU.
• Pushing the HDG/TRK select knob on the FCP to select the existing
heading.
• Selecting APPR/LAND.
• Selecting NAV.
• Selecting the LOC ONLY mode
October 02, 2006
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