NOTE: If invalid hours (greater than 23) or minutes or
____ seconds (greater than 59) are entered, the GMT line flashes. Press CLR and repeat steps (c) and (d).
D. Alignment Status Check
(1) To check INS alignment status press CDU STS pushbutton. Verify that SYS STS/TEST page appears on CDU display and that:
(a) The number on ALIGN line is the status number. (Status numbers start at 90 and decrement through 80, 70, 60, 50, 40, 10, and 2 as alignment sequence progress).
NOTE: The LTN-92 does not have status 40.
____
(b) The number on TIME line is minutes and tenths of minutes remaining in ALIGN.
(2)
On airplanes with LTN-72RL INS, verify that MSU READY NAV annunciator comes on when the INS aligns to status 2.
(3)
On airplanes with LTN-92 INS, verify that MSU ALIGN annunciator goes out when the INS aligns to status 2.
(4)
On airplanes with LTN-72RL INS, when MSU READY NAV annunciator is on, place MSU mode selector switch to NAV, the READY NAV annunciator will go out. Verify that ALIGN line changes to NAV with a status number of 1, and TIME line changes to time in navigate mode.
(5)
On airplanes with LTN-92 INS, when status 2 is reached, place MSU mode selector switch to NAV. Verify that ALIGN line changes to NAV with a status number of 1, TIME line changes to time in navigate mode, and the MSU ALIGN annunciator goes out.
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(a) After status 1 is attained the airplane may be moved.
NOTE: Do not set the mode switch out of NAV after status 1
____ (navigation mode) is reached. Doing so destroys the alignment of the inertial platform and the complete alignment sequence must be repeated on the ground.
E. Display Test
(1)
The display test procedure verifies that each prompt/display line and the CDU and MSU annunciators are operating correctly. The display test may be performed at any time with the INS in STBY, ALIGN, or NAV.
(2)
Press STS pushbutton on each CDU. Verify that SYS STS/TEST page appears on each CDU display with ALIGN between entry line markers.
(3)
Slew each CDU display up until SYSTEM TEST page appears (on each display) with DISPLAY TEST between entry line markers.
(4)
Press EXP on INS-1 CDU and verify that:
(a)
Display pattern rotates through each of the five lines on INS-1 CDU display.
(b)
On INS-1 CDU, the WRN, BAT, ALR, and OFS annunciators come on.
(5)
On airplanes with LTN-72RL INS, on each MSU, press READY NAV and BATT annunciators. Verify that READY NAV annunciator comes on green and BATT annunciator comes on red. On airplanes with LTN-92 INS, on each MSU, press ALIGN and BATT annunciators. Verify that ALIGN annunciator comes on amber and BATT annunciator comes on red.
(6)
INS Shut Down
(a) Place mode selector in OFF position.
CAUTION: FAILURE TO MOVE MODE SELECTOR TO OFF WILL CAUSE INS
_______ TO AUTOMATICALLY SWITCH TO BATTERY POWER WHEN POWER IS REMOVED FROM THE AIRPLANE.
(b)
Remove electrical power if no longer required.
(c)
Remove equipment cooling if no longer required.
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INERTIAL NAVIGATION SYSTEM - TROUBLE SHOOTING
_____________________________________________
1. General_______(See figures 101 and 102.)
A. There are two distinct yet related trouble shooting techniques provided for the INS system. The first relates to the malfunction code analysis. Malfunction codes identify INS problems detected during INS self-test. If a flight crew squawk can be related to a specific malfunction code, the malfunction code analysis procedure (paragraph 3 and figure 101) should be performed. After performing this procedure, an operational test should be performed. Or, if the malfunction code analysis does not clear the trouble, the trouble shooting procedure (figure 102) based on an operational test, and in tree form, should be accomplished.
B. The second and more complete method is the trouble shooting tree, figure
102. This trouble shooting procedure is a complete procedure, based upon the performance of a simplified operational test of the system. It is presented in a tree-type format to aid in the rapid isolation of any failure in the system. The test steps (heavy-line boxes) making up the simplified test are connected by shaded arrows to show the OK condition path. When all of the steps in the OK condition path check out, the system is operable. When a test step does not check out, follow the NOT OK line, selecting the box and isolation procedure for the trouble symptom listed. After turning to the appropriate procedure, continue to follow a single line by analyzing the results of each test step until required corrective action is determined. After performing corrective action, repeat the step at which failure was encountered and complete the simplified operational test procedure to check out the system.
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