Airplanes with HMCDU/MCDU:
a. LEFT FMC INOPERATIVE - When operating in flight director mode with both F/D switches ON, LNAV and VNAV will engage if the Captain’s NAV source switch is selected to R FMC or L CDU position. Otherwise, LNAV and VNAV will engage if the right autopilot is engaged or only the right F/D is ON. Turning off the left F/D switch would allow use of LNAV and VNAV, but only the right flight director would operate.
Procedure: After liftoff (with F/D in TO mode), use HDG SEL and FL CH modes as desired until Captain’s NAV selector is moved to an alternate source, or right autopilot is engaged. Then use LNAV and VNAV as desired.
b. RIGHT FMC INOPERATIVE - When operating in flight director mode with both F/D switches ON, LNAV and VNAV will engage. If the First Officer’s NAV source switch is selected to the L FMC or R CDU position, LNAV and VNAV will engage with any autopilot engaged. Otherwise, LNAV and VNAV will engage if the left or center is engaged or the right F/D is ON.
Procedure: After liftoff (with F/D in TO mode), use HDG SEL and FL CH modes as desired until First Officer’s NAV selector is moved to an alternate source, or left or center autopilot is engaged. Then use LNAV and VNAV as desired.
In addition to above, prior to takeoff accomplish the following as appropriate:
1) For an inoperative left FMC:
a. Select the FMC-R position with the Captain's FMC NAV Source Select Switch to load data from the right FMC into the left CDU.
NOTE: The FMC switch should remain in this position for at least one minute after flight
planning is completed or after any flight plan modifications prior to takeoff.
b. After a minimum of one minute, select the CDU-L position with the Captain's FMC NAV Source Select switch.
c. Observe that Captain’s HSI (-200/-300) or ND (-400ER) Map display changes to a simplified route display without normal navigation database symbology. “CDU-L” should be displayed on the HSI/ND. This confirms availability of the Alternate
Navigation system.
d. Prior to takeoff, select the FMC-R position with the Captain’s FMC NAV Source SelectSwitch.
For an inoperative right FMC:
a. Select the FMC-L position with the First Officer's FMC NAV Source Select Switch to load data from the left FMC into the right CDU.
NOTE: The FMC switch should remain in this position for at least one minute after flight
planning is completed or after any flight plan modifications prior to takeoff.
b. After a minimum of one minute, select the CDU-R position with the First Officer's FMC
NAV Source Select switch.
c. Observe that First Officer’s HSI (-200/-300) or ND (-400ER) Map display changes to a
simplified route display without normal navigation database symbology. “CDU-R”
should be displayed on the HSI/ND. This confirms availability of the Alternate
Navigation system.
d. Prior to takeoff, select the FMC-L position with the First Officer’s FMC NAV Source Select Switch.
The ability to confirm availabilty of Standby Nav System should stop crews from operating with "Failed" FMC's and SNS not operating.
This should be carried out before flight and if not avail you should be staying put !
Hope this helps
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Fools rush in where Angels fear to tread
[This message has been edited by Golden Rivet (edited 11 March 2001).]
[This message has been edited by Golden Rivet (edited 11 March 2001).]