曝光台 注意防骗
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takes approximately 10 minutes.
When the INS achieves align complete, the IFA GPS legend is removed and the MC automatically
transitions to AINS position keeping mode. This is indicated by the NAV display replacing the IFA
GPS align display. If good GPS satellite data is available and then lost while an IFA GPS align is being
performed, the INS goes to align hold for 65 seconds waiting to reacquire good satellite data. If good
satellite data is reacquired within 65 seconds, the INS continues to align using GPS data. If good
satellite data is not reacquired within 65 seconds, the MC attempts to finish the INS alignment with
a radar IFA as described in If IFA RDR Indicated.
A1-F18EA-NFM-000
VII-24-17 ORIGINAL
Figure 24-5. INS In-Flight Align
A1-F18EA-NFM-000
VII-24-18 ORIGINAL
24.2.5.4.3 If IFA RDR Indicated. Maintain straight-and-level flight for as much as practical during
alignment. If a turn must be executed, rapidly exceed 30° AOB and return to straight-and-level flight
as soon as possible. This prevents the INS from aligning to a false reference by placing the alignment
on hold until straight-and-level flight is regained. During IFA, air data dead reckoning is used for
navigation to maintain a current present position. If GPS is acquired, then finish the INS alignment
with GPS IFA as described in If IFA GPS Indicated.
When the In-Flight Align display displays an OK after the QUAL number, place the INS mode select
knob to the NAV position.
PVU mode may be overridden by deselecting the CONT PVU option but IFA quality will be
affected. Deselecting CONT PVU commands PVU for 10 seconds of each minute, alternating with the
last selected radar mode. When air-to-ground ranging (AGR) mode is selected (e.g., by HUD
designation) CONT PVU is deselected, 20 seconds of AGR is commanded, and PVU is commanded for
10 seconds of each minute alternating with AGR. In PVU mode, the radar provides Doppler velocities
for INS alignment. The radar look-down angles are optimized for land or sea return by selection of
LAND or SEA option at the bottom of the display. PVU is inhibited for IFA if the aircraft is not in the
NAV master mode.
If the radar is not operating or is inhibited from operating in PVU the time-in-alignment display
flashes and the CONT PVU option is not displayed because continuous PVU can not be commanded.
Present position can be provided for the alignment by performing a position update using the UPDT
option or by entering the aircraft data on the UFCD using the DATA option. Another very good
technique is to select TACAN position keeping if a stationary TACAN is available. Velocity updates
cannot be performed during IFA. The VEL update option is displayed but returns to the In-Flight
Align display top level when selected.
Following an IFA RDR, make every attempt to maintain VMC with a
discernible horizon. Residual attitude errors may be subtle and difficult
to discern without reference to a visible horizon or the standby instruments.
If velocity vector information is suspect, select STBY to the HUD.
24.2.5.4.4 For Landing. Crosscheck HUD information with standby instruments.
Inflight Alignment -
1. ATT switch - STBY
2. NAV master mode - SELECT
3. INS knob - OFF (5 seconds minimum)
4. HSI/DATA/(A/C) format - Update MVAR , position, and winds aloft (if required)
5. Maintain straight and level, unaccelerated flight for 20 seconds prior to selecting IFA.
6. INS knob - IFA
7. Maintain straight and level flight for at least 30 seconds after selecting IFA.
A1-F18EA-NFM-000
VII-24-19 ORIGINAL
8. HSI format - SELECT SEA or LAND (IFA RDR only)
After 20 seconds in IFA -
9. ATT switch - AUTO (VV position is degraded if flashing slowly)
If IFA GPS indicated -
10. Perform one gentle, 90° S-turn (less than 20° AOB and ±10° pitch), then maintain straightand-
level as much as practical.
After approximately 10 minutes -
11. HSI format - Verify transition to POS/AINS
If IFA RDR indicated -
10. Maintain straight-and-level flight as much as practical during alignment. If a turn must be
executed, rapidly exceed 30° AOB and return to straight-and-level flight as soon as possible.
When QUAL indicates OK (approximately 20 minutes) -
11. INS knob - NAV
Following an IFA RDR, make every attempt to maintain VMC with a
discernable horizon. Residual attitude errors may be subtle and difficult
to discern without reference to a visible horizon or the standby instruments.
If velocity vector information is suspect, select STBY to the HUD.
For landing -
12. Crosscheck HUD information with standby instruments.
24.2.5.4.5 CV/GND Alignment Completion (Without GPS Selected and Operating). An IFA may be
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NATOPS Flight Manual 飞行手册 2(96)
