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and the INS can be switched to the NAV mode. If it is not switched it automatically reverts to the NAV
mode when weight is off the wheels.
If the carrier heading changes more than 10° or carrier speed varies more than 1 knot and the AC
number on the DDI is 3 or less during manual alignment the aircrew must enter data to reinitialize the
alignment. This usually results in the QUAL number starting over at 99.9 but it rapidly aligns to the
QUAL number achieved prior to the update. The continuation of the alignment will be faster than if
the update had not been made. When AC=4 is displayed on the DDI the INS tracks CV heading and
speed changes and the INS does not need to be reinitialized.
The parking brake must remain set until alignment is complete. If the parking brake is released
before OK is displayed and the align quality is greater than 5 the system sequences into GYRO mode.
If the brake is released with the align quality less than 5 the system goes into a limited performance
navigation mode, or complete reinitialization is required to complete the normal alignment (see figure
24-2). The aircrew can enter present position anytime after selecting the INS manual carrier alignment
mode.
A1-F18EA-NFM-000
VII-24-12 ORIGINAL
Figure 24-3. INS CV Align
A1-F18EA-NFM-000
VII-24-13 ORIGINAL
MANUAL ALIGNMENT
1. Parking brake - SET
The parking brake must remain SET until the manual alignment is complete. If the parking brake
is released before the alignment is complete the alignment must be reinitiated.
2. ATT select switch - AUTO or INS
3. INS mode selector knob - CV
4. HSI MAN option - PRESS
On the UFCD -
5. POSN option - PRESS
6. Direction (N/S) - SELECT
7. ENT - SELECT
8. Enter Latitude (leading zeroes must be entered)
9. ENT - SELECT
10. Direction (E/W) - SELECT
11. ENT - SELECT
12. Enter Longitude (leading zeroes must be entered)
13. ENT - SELECT
14. CHDG - SELECT
15. True heading - ENTER data
16. ENT - SELECT
17. CVEL - SELECT
18. Velocity - ENTER data
19. ENT - SELECT
After alignment is complete -
20. INS mode selector knob - NAV or IFA
24.2.5.2 CV Alignment Mode. Selecting CV alignment provides CV alignment options of RF (radio
frequency), CBL (cable), and MAN (manual). With the RF or CBL alignment option selected the
aircraft is data linked to the SINS (ships inertial navigation system). The MAN option has no data link
capability and alignment data must be entered manually.
A1-F18EA-NFM-000
VII-24-14 ORIGINAL
24.2.5.3 GND (Ground) Alignment Mode. To perform an INS ground alignment the parking brake
must be set and the INS mode selector knob switched to GND. When this is done the INS is turned
on, the GND align display appears on the MPCD, and the TIME display on the GND align display
begins to increment. During the first 1 minute of alignment NO ATT is displayed to the right of QUAL:
GND. After the platform has leveled NO ATT is replaced with a quality number and the INS begins
to determine true north. The quality number is an estimate of present position accuracy. The aircraft
may be taxied without restarting the alignment but the parking brake must be reset to complete the
alignment, see figure 24-4.
NOTE
The most accurate alignment of the AN/ANS-139 is achieved by
changing aircraft heading at least 70° (180° optimum) after OK is
displayed next to the quality number and allowing the alignment to
continue.
The MC automatically transfers waypoint zero to the INS to be used as aircraft present position.
This information appears on the GND align display. Waypoint zero position can be updated prior to
selecting GND align but if an error is noticed after the alignment has begun aircraft present position
must be corrected because waypoint zero is transferred to the INS only once. If aircraft present
position is found to be incorrect it must be corrected or the INS will align improperly. Refer to A/C
Programming, this chapter to enter new aircraft position data.
After the INS alignment has reached an acceptable level OK is displayed next to the quality number
and the INS may be switched to NAV. When NAV is selected the alignment display is removed from
the MPCD. If the NAV mode is not manually entered the INS automatically switches to NAV when
groundspeed is greater than 80 knots and weight is off wheels.
24.2.5.3.1 Stored Heading (STD HDG) Alignment. A stored heading alignment may be selected to
reduce INS alignment time if the INS has been shut down after a good alignment, the aircraft has not
been moved, and NAV has not been selected. The STD HDG option is provided on the CV/GND align
display. The STD HDG option is removed when a GND alignment has progressed to the point where
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NATOPS Flight Manual 飞行手册 2(94)
