7. To monitor station selection Observe
TO-FROM data display.
Observe only the number of stations eligible for
mixing will be displayed. A 0 indicates that none of the
9 stations are eligible for selection.
8. Monitor INS UPDATE annunciator.
Mixing will not be annunciated if: (a)
TACAN control is inappropriately set;
(b) TACAN station data loaded in
error; (c) aircraft look-down angle is
ground distance is less than two
times the altitude. When 2 minutes
elapse without an update, the NO INS
UPDATE annunciator will illuminate.
9. To return INS display to normal Set
data selector to any position except
WYPT or DIS/TIME.
10. To monitor program of mix Set data
selector to DSRTK/STS. (Observe
Accuracy Index (A1) will decrement
To ensure favorable geometry during
the update process, the following
TACAN station criteria should be
One station must be at least 15 nm
updating, update should continue
station.For optimum dual TACAN
TACAN station and one on-track
should be evenly distributed in
azimuth around the aircraft.
11. Waypoint thumbwheel Set to number
of first TACAN station to be used.
Observe selected station number is displayed on the
TO side of TO-FROM data display.
(10) Switching from aided to unaided inertial
1. Data selector - DSRTK/STS.
2. Key 5 - Press.
Observe INSERT/ADVANCE pushbutton annunciator
illuminates; 000005 appears in right data display.
3. INSERT/ADVANCE pushbutton Press.
Observe INSERT/ADV'ANCE pushbutton annunciator
extinguishes. Data display returns to normal with 5
appearing in first digit of right display.
Benefits of previous aiding are
automatic updates will be made.
(11) To obtain readouts from INS:
The computer is assumed to be in
the NAV mode for all data displays.
(a) System status: Data selector DSRTK/STS.
Observe numbers indicating system status appear in
right data display.
(b) Geographic present position: Data selector -
Observe latitude and longitude of present position
appear in left and right data displays, respectively.
Both displays are to tenth of a minute.
(c) UTM position: Data selector UTM POS.Observe
northing and zone with easting of present position
appear in left and right displays, respectively. Both
displays are in kilometers.
(d) True heading and MAG heading: Data
selector - HDG/DA.
Observe aircraft true heading appears in left data
display to nearest tenth of a degree. Press and hold
keys 3 and 9 simultaneously. MAG heading appears in
left data display to nearest tenth of a degree. Release
keys 3 and 9. Left display reverts to true heading.
(e) Groundspeed: Data selector - TK/GS.
Observe groundspeed appears in right data display to
(f) Ground track angle: Data selector TK/GS.
Observe ground track angle appears in left data