(2)
To correct a flashing ALIGN light problem, the present position may be input through the Flight Management Computer (FMC) Control Display Unit (CDU).
NOTE: The CDU scratchpad must be reloaded with the present position and that input selected to the SET IRS POS field, even if the present position is already shown in the SET IRS POS field.
(3)
Make sure present position is shown on the ISDU for the IRS L and IRS R.
NOTE: This confirms that the two systems have accepted the present position.
(4)
Do not move the mode selector switches on the IRS MSU to OFF, except where called for in the procedure.
(5)
To remove power from the IRUs, set the mode selector switch on the IRS MSU to the OFF position. Do not open the circuit breakers.
E. The procedure for a flashing ALIGN light is as follows:
(1) Input the correct present position into the scratch pad.
NOTE: The box prompts or a position might not show under the SET
____
IRS POS line.
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(2)
Push the line select key (LSK) 4R.
(3)
If the ALIGN light continues to flash, input the same present position a second time.
NOTE: Make sure that the present position is first input into the
____ scratch pad before you push LSK 4R.
(4)
If the ALIGN light continues to flash, input the present position through the IRS display unit (ISDU).
(5)
If the ALIGN light continues to flash, input the present position again through the ISDU.
(6)
If ALIGN light continues to flash:
(a)
Set the IRS mode switch to the OFF position and wait for the ALIGN light to go out.
(b)
Set the IRS mode switch to the NAV position. 1) Make sure the ALIGN light stays on.
(c)
Input the present position again as described above.
(d)
If the ALIGN light continues to flash, replace the IRU.
5. Malfunction Codes
_________________
A. The IRS has provisions to do a failure analysis through ten malfunction codes that are shown on the ISDU. These codes are shown when the DSPL SEL switch on the ISDU is in the HDG/STS position and the SYS DSPL switch is set to an active IRU.
B. Fig. 102 lists the ten malfunction codes, and the status of the ALIGN and FAULT lights on the IRS MSU. The figure also shows the component unsatisfactory condition that causes a malfunction code to be shown. Also, Fig. 102 gives recommended steps to be followed by the operator to correct the unsatisfactory condition.
C. The malfunction codes are shown in the two right most digits in the ISDU display. These digits will be blank if no codes need to be shown or if the SYS DSPL switch is not set to an active IRU. If a malfunction code is shown and the CLR key light is off (on the ISDU), then there is only one malfunction code. If there is a malfunction code and the CLR key light is on, more than one malfunction has occurred. Thus, the CLR key light shows if there is more than one malfunction code.
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D. When there is more than one malfunction code, the second and subsequent codes may be shown if you push the CLR key. At that time, the next lower priority code will be shown. If the lowest priority code is shown and you push the CLR key, the display will return to the highest priority code.
E. When you do the recommended steps to clear the malfunction codes, make sure you follow these hints:
(1)
Do not move the mode selector switches on the IRS MSU to OFF, except where called for in the procedure.
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