(e)
Roll attitude signals to the yaw damper system for turn coordination
(f)
Platform heading to the compass couplers of the magnetic heading reference system
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(g)
Flag output signals to INS updating annunciators.
(h)
Roll and pitch attitude signals, drift angle and INS BCD signals to the flight recorder and AIDS systems.
C. INS Instrument Switching
(1)
The transfer switching for INS navigation data is shown in Fig. 13. The navigation display signals normally are applied from INS 1 to the captain's HSI and from INS 2 to the first officer's HSI. Selection of an alternate INS may be made by operating the INS transfer switch which positions the associated ledex relay. The VOR-ILS/INS switch determines whether radio navigation data or INS navigation data will be displayed.
(2)
The INS pitch and roll attitude signals drive the attitude display sphere in the ADI. A flag signal is provided to the ADI's in case of loss or failure of attitude reference signals (Fig. 14). The attitude signals are normally routed from INS 1 to the captain's ADI and from INS 2 to the first officer's ADI. INS 3 is selected as an alternate source for either ADI by operating the ATT/COMP STAB transfer switch which positions the appropriate transfer relay.
(3)
Platform heading signals from the INS are used by the magnetic heading reference system (MHRS) for compass stabilization. Refer to 34-21-00. Platform heading signals are normally routed from INS 1 to MHRS compass coupler 1 and from INS 2 to MHRS compass coupler 2. (Fig. 14). INS 3 is selected as an alternate source for either compass coupler by operating the ATT/COMP STAB transfer switch which positions the appropriate transfer relay.
(4)
VHF Navigation Frequency Tuning and INS Approach Mode Enable
(a)
Applying a ground at the frequency select common of the INU establishes at the INU the autotune mode of tuning the VHF navigation receiver (Fig. 13). When the ground is removed from the INU frequency select common and the tuning head in the VHF navigation control panel is enabled, the tuning head may then be used to manually select one of the VORTAC frequencies stored in the INU, and manually tune the VHF navigation receiver.
(b)
When the approach mode is enabled the INU is allowed to provide a magnetic heading output and a signal for magnetic heading annunciation.
21. INS Power Interface (Fig. 15)
___________________
A. Power for the INS system is derived from the standby bus, the fail-op bus and from the essential and No. 2 flight instrument buses. Control is through the electronic circuit breaker panel (P7), the overhead circuit breaker panel (P126) and the main power circuit breaker panel (P6).
B. The system is energized by closing the circuit breakers which supply power to the navigation units, central air data computers (CADC), horizontal situation indicators (HSI), attitude director indicators (ADI), 26-volt ac autotransformers, and flight instrument switching relays. The INS battery units contain individual circuit breakers which must also be closed to energize the system.
C. System power requirements include 115-volt ac primary power, 26-volt ac synchro power, 28-volt dc relay control power and 5 volts ac for panel lighting.
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D. By operating the INS BAT PARALLEL switch on the flight engineer's panel (P4), battery unit No. 3 can be switched in parallel with battery unit No. 1. This increases the emergency operating time of INS 1 to approximately 30 minutes.
22. Operation_________
A. INS Startup and Data Base Validity Check.
(1)
Verify that the MSU mode selector switch is set to OFF.
(2)
Provide ground power to airplane and energize buses on the P7 and P126 circuit breaker panels.
(3)
Provide cooling air to electronic equipment (Ref 21-58-00).
CAUTION: ENSURE EQUIPMENT COOLING IS OPERATED BEFORE TURN ON OF
_______ ELECTRONIC SYSTEMS OR DAMAGE TO EQUIPMENT MAY RESULT. EQUIPMENT COOLING SYSTEM MUST BE SET FOR NORMAL COOLING AS DESCRIBED IN 21-58-00.
ENSURE THAT COOLING AIR IS AVAILABLE TO INS NAVIGATION UNITS BEFORE OPERATING INS. FAILURE TO PROVIDE ADEQUATE AIR SUPPLY WILL RESULT IN FAILURE OF NAVIGATION UNITS.
(4)
Close all INS circuit breakers to apply power to the INS.
(5)
On airplanes with LTN-92 INS, place mode selector switch on each MSU to STBY. After 6 seconds, verify the following on each CDU display:
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