(15)
 Backup Battery Operation

 (a)  Because inertial navigation systems required continuous operation in flight, the INS is protected against electrical power interruptions by a backup battery. When the primary 400-Hz input power fails or drops below present limits, the INS will revert to the backup battery power source, and the BATT light on the control/display unit will illuminate.

 (16)
 CDU Test

 (a)  Test of the control/display unit can be accomplished by placing the display selector switch to TEST and the WPT switch to any position except 0. In this position, all annunciator lamps on the CDU will illuminate and all elements of the 7-bar incandescent lamps should be lit. Left and right numerical displays are degree signs, decimal points, arc-minute signs, NS, EW, and all eights, except left digit of right numerical display is R. FROM/TO display is all eights, and ALERT, BATT, and WARN annunciators and TK CHG, INSERT and HOLD indicators come on.

 (17)
 Attitude Slew

 (a)  Attitude slew allows the simulation of airplane attitude movements without the use of a tilt table or removal of the INS navigation unit from the equipment rack. The resulting outputs enable the checkout of INS attitude signal interfaces and the calibration of interfacing systems.
 EFFECTIVITY AIRPLANES WITH LTN-72 INS  
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 (b)  To perform the attitude slew test, insert special attitude slew test connector (Litton P/N 456058-01) into J4 on the front of the INU.
 (c)  Set INS MSU mode selector to STBY position. annunciator should flash continuously. CDU WARN
 NOTE:____ If CDU data selector is set to DSR TK/STS, action code 7 will be displayed.
 (d) (e)  Set INS CDU data selector to POS.Insert pitch slew angles up to a maximum of 15. on the data keyboard in the same manner as lattitude entry. Press the N pushbutton for a nose down angle and the S pushbutton for a nose up angle.
 EXAMPLE:_______ For 10 degrees nose down, press N 10 000 (10 deg. 00.0 min.) and insert.
 (f) (g) (h)  Insert roll slew angles (there is no limit on roll) on the data keyboard in the same manner as longitude entry. Press the E pushbutton for a left roll angle and the W pushbutton for a right roll angle.Set INS MSU mode selector to ALIGN.Set INS CDU data selector to DSR TK/STS and allow INS to align to status 80. After 2 minutes at status 80, platform slewing will proceed at approximately 1.33 degree/minute. The platform heading (used for compass stabilization) will also be slewed at 1.33 deg. per minute. This can be observed with the MAG-DG switch in the DG selection while monitoring compass heading.
 NOTE:____ If CDU data selector is set to DSR TK/STS and HOLD pushbutton is pressed, malfunction code 19 will be displayed in right display whenever the actual and selected gimbal angles differ by more than 3 degrees, indicating saturation of the gyro torquer loop. When within 3. of selected angle, the malfunction code will be removed.
 (i)  Position the captain's ATT/COMP STAB switch as required. When the slewing operation is complete, verify that appropriate ADI displays approximate pitch and roll angles selected.
 NOTE:____ The exact ADI display is dependent on airplane attitude. The platform will slew until the accelerometer outputs are equivalent to the angles loaded through the CDU. These must be considered as angles with respect to true horizontal.

 EFFECTIVITY AIRPLANES WITH LTN-72 INS  
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 (j)  To relevel the platform, turn the mode selector to OFF, remove the attitude slew test connector from J4 on front of the navigation unit, replace test connector cover at J4, and repeat align process.
 B.  Control
 (1)  INS Turn On (Fig. 18)
 (a)  
Set mode selector switch on MSU to OFF.

 (b)  
Provide electrical power.

 (c)  
Supply equipment cooling.

 CAUTION: ENSURE THAT COOLING AIR IS AVAILABLE TO NAVIGATION
_______ UNITS BEFORE OPERATING INS. FAILURE TO PROVIDE ADEQUATE AIR SUPPLY WILL RESULT IN FAILURE OF NAVIGATION UNITS.
 (d)  
Close all INS, and FLT INST SW RELAYS circuit breakers on electronic circuit breaker panels P7 and P126.

 (e)  
Set both VOR-ILS/INS switches to INS.

 (f)  
Set AUTO/MAN/RMT switch to MAN.

 (g)  
Set mode selector switch on MSU to STBY.

 (h)  
Place the control display unit data selector to POS, check that: 1) Red, amber and green lamps do not illuminate. 2) FROM/TO display is 0 0. 3) INSERT pushbutton illuminates. 4) On airplanes with INS program 72-28-0,
　
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