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In
dual couple transition the following events occur:
Command bars are in-view on both pilot and copilot PFDs.
The GP-820 PFD-CMD button illuminates both L and R
annunciators.
the dual couple mode the high priority FGC (i.e., the FGC
selected on the-DC-884 sensor page) averages the radio data
from the pilot and copilot NAV sources. This allows the
approach mode to be continued in the event of a failure of one
navigation receiver or if there is an unflagged miscompare
between the NAV receivers.
The high priority FGC outputs
identical FD commands (based on the average radio deviations)
to both pilot and copilot PFDs in the dual couple mode.
Navigation failures in the dual couple mode result in the
following automatic reconfiguration:
. NAV 1 Fails - Pilot PFD command bars are removed and the
PFD-CMD reverts to R.
Approach mode continues using data
from NAV 2. If NAV 1 becomes valid the dual couple mode
will automatically return.
. NAV 2 Fails - Copilot PFD command bars are removed and the
PFD-CMD reverts to L. Approach mode continues using data
from NAV 1. If NAV 2 becomes valid the dual CPL mode will
automatically return.
. Unflagged Miscompare Between NAV 1 and NAV 2 - The system
will automatically select the NAV source with the smallest
deviation (must be greater than 1/3 DOT). The PFD-CMD logic
and command bars operate the same as in the NAV failure
case.
This is annunciated on the EICAS.
NOTES: 1. Although the FGC uses averaged ILS data for
guidance, the EFIS comparison monitor always
annunciates LOC/GS miscompares based on nonaveraged
data (i.e., direct comparison of NAV 1 and NAV 2).
2.
The PFD-CMD pushbutton is inhibited in dual couple
mode.
3. After cancellation of the APR mode the PFD-CMD
status reverts to the side which was selected prior
to the dual couple transition.
22-14-00
Page 298.120
Aug 15/91
Use or disclosure of information on this page IS subjecf to the restrictions on the title page Of this document.
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