(2)  
The drift angle bug is biased out of view upon loss of INS navigation flag voltage.

 8.  Attitude Director Indicator (Fig. 11)
___________________________
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ATTITUDE SPHERE

INCLINOMETER
INDICATOR
Attitude Director Indicator
Figure 11

EFFECTIVITY CONFIG 2
AIRPLANES WITH LTN-72 INS 799 Page 27

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 751777
 A.  Two attitude director indicators (ADI) are installed in the airplane, one on each pilot's instrument panel. The indicators are used primarily to display airplane attitude. Each is, however, a composite instrument which accepts and displays glide slope and localizer deviation, radio altitude, speed deviation, decision height, flight director commands, and rate of turn signals from other navigation systems.
 B.  The captain's ADI receives pitch and roll attitude information from INS No. 1 or 3 as selected from the ATT/COMP STAB switch on the captain's flight instrument panel. Similarly, the first officer's ADI receives attitude information from INS No. 2 or 3. An illuminated annunciator adjacent to the switch shows which two of the three INS systems are supplying information to the ADI's (Fig. 1).
 C.  Airplane attitude is indicated by a dc torque motor-driven sphere, representing the horizon and moving relative to a fixed airplane symbol near the center of the instrument face (Fig. 11). The sphere rotates in pitch and roll to correspond to the airplane attitude. In the event of power loss to the indicator, loss of the attitude valid signal to the indicator or detection of failures by the indicator monitor circuits, the instrument attitude (ATT) warning flag appears to indicate an invalid attitude indication.
 D.  Each ADI contains self-test provisions. When the test button on the front of the indicator is depressed, the sphere will indicate a change in attitude indication of approximately 20 degrees right bank and 10 degrees climb. The attitude warning flag will also appear.
 9.  INS No. 3 Fail Op Annunciator
_____________________________
 A.  When the No. 3 inertial navigation unit provides a valid attitude flag signal, the INS-3 annunciator on the pilots' center instrument panel displays black. The annunciator displays red when the altitude flag signal is not valid.
 10. Flight Instrument Switching
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 A.  The horizontal situation indicators and attitude director indicators are multipurpose instruments used to display flight information from several different systems. Because of this, INS information is transferred to these instruments through a flight instrument switching network.
 B.  The various instrument switching relays are located in the flight instrument relay panel (P73) which is attached to the left side of the electronic equipment rack (E1) in the main equipment center (FIG. 1 and 12).
 C.  The portion of the switching network involving the INS consists of a captain's VOR-ILS/INS switch and transfer relay, a first officer's VOR-ILS/INS switch and transfer relay, captain's and first officer's INS transfer relays, captain's and first officer's attitude/compass stabilization transfer relays and a flight instrument switching accessory box. The INS and attitude/compass stabilization transfer relays are controlled by the INS and ATT/COMP STAB switches on the captain's flight instrument panel. There are no attitude and INS transfer switches on the first officer's flight instrument panel.
 EFFECTIVITY AIRPLANES WITH LTN-72 INS  
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34-41-00
R304 B556 R288
R306
R302
R297
P73 FLIGHT INSTRUMENT
SWITCHING RELAY PANEL
R449

R855
B231
R856
R288 FLIGHT DIRECTOR COMPUTER SELECTR450
RELAY NO. 1 (CAPT)
R289 FLIGHT DIRECTOR COMPUTER SELECT RELAY NO. 2 (F/O)
R298
R297 RADIO/INS RELAY NO. 1 (CAPT)

R303 R298 RADIO/INS RELAY NO. 2 (F/O)
R302 INS TRANSFER RELAY NO. 1 (CAPT) R307
R303 INS TRANSFER RELAY NO. 2 (F/O)
R304 ATTITUDE TRANSFER RELAY NO. 1 (CAPT)

R289 B557
R305 ATTITUDE TRANSFER RELAY NO. 2 (F/O) R305
R306 COMPASS TRANSFER RELAY NO. 1 (CAPT)
R307 COMPASS TRANSFER RELAY NO. 2 (F/O)
R449 VOR/ILS TRANSFER A RELAY NO. 1 (CAPT)
R450 VOR/ILS TRANSFER A RELAY NO. 2 (F/O)
R855 VOR/ILS TRANSFER B RELAY NO. 1 (CAPT)
R856 VOR/ILS TRANSFER B RELAY NO. 2 (F/O)
B231 INSTRUMENT SWITCHING ACCESSORY BOX
B556 VOR/ILS ISOLATION AMPLIFIERS
　
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