PROCEDURE TROUBLESHOOTING REFERENCE
INSERT/ADVANCE key - Depress.
Left-hand and right-hand displays - Read arc-seconds
related to present inertial position to the nearest a tenth
of a second.
HOLD key - Depress to return to INS normal operation.
h. Magnetic variation - Check as follows:
Keys 3 and 9 - Depress simultaneously.
Right-hand display - Read magnetic variation to a tenth
of an arc-minute. Compare with local values.
While operating in the NAV mode, magnetic variation
is computed when aircraft roll is less than 9° and the
magnetic heading input is valid (absence of error
DATA/SELCTOR - Momentarily set to any position
except L/L WYPT to return to normal INS display
Distance and Time to Next Waypoint - Check as follows: