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 the present position is shown on the ISDU for the IRS 1 and IRS 2.

 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.

 (6)  
Make sure that the airplane is not moved during the alignment of the LRU.

 B.  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.

 (2)  
Push the line select key (LSK) 4R.

 (3)  
If the ALIGN light continues to flash, input the same 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).
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 (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 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.
 6.  BITE Procedure______________
 A.  Malfunctions or failures of the IRS system can also be identified by the use of the FMS BITE (Built-In Test Equipment) procedures, contained in Chapter 22.
 B.  The FMS BITE is started and controlled through the FMCS CDU. The CDU is the flight compartment control and display for actuating and evaluating FMCS, DFCS, A/T, and IRS BITE (Ref 22-01-00, FMS BITE - D&O). Once the test has been started from the CDU, the system under test will transmit plain text messages to be shown on the CDU. In response to the messages, the operator can set flight compartment controls, and/or do data entries through the CDU. Test pass or failure is shown on the CDU display.
 C.  Do the IRS BITE trouble shooting per 22-05-00, IRS BITE - T/S.
 NOTE: Trouble shooting procedures for FMCS, DFCS, and, A/T are in
____
 these sections:

 FMCS BITE - T/S, 22-02-00
 DFCS BITE - T/S, 22-03-00
 A/T BITE - T/S, 22-04-00

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 D.  After you have completed all BITE tests, push the INIT REF key on the FMCS CDU to exit the BITE mode.
 7.  IRS Accuracy Criteria
　
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