(a)  Make sure that the INIT/REF INDEX page shows.

 (9)  
Push the LSK adjacent to <POS.

 (a)  Make sure that the POS INIT page shows.

 (10)
 Push the NEXT PAGE key on the CDU.

 (a)  Make sure that the POS REF page shows.

 (11)
 Push LSK 2L on the CDU.

 (a) Make sure that the IRU position is in the scratchpad.

 (12)
 Push the LEGS key on the CDU.

 (a)  Make sure that the LEGS page 1/1 shows with the reference point name on the top line.

 (13)
 Push LSK 2L on the CDU.

 (a)  Make sure that two different identification points show.

 (14)
 Record the number in nautical miles that shows between the two identification points.

 NOTE: This is the radial position error.
____
 (15)
 Compare the radial position error and the time in NAV mode to the limits shown on Fig. 103.

 (16)
 Replace the IRU (Ref 34-28-31/401) if one of these conditions occurs:

 (a)  
The radial position error of the IRU is in the "REPLACE-1 FLIGHT" area of Fig. 103.

 (b)  
The radial position error is in the "REPLACE-2 CONSECUTIVE FLIGHTS" area of Fig. 103 for two consecutive flights.

 8.  Prepare for Trouble Shooting
____________________________
 A.  Set the two mode selector switches on the IRS MSU (pilot's aft overhead panel) to the OFF position.
 B.  Supply electrical power (Ref 24-22-00/201).
 CAUTION: MAKE SURE EQUIPMENT COOLING IS ON BEFORE YOU TURN ON THE ELECTRONIC
_______
 SYSTEMS. IF YOU DO NOT, DAMAGE TO EQUIPMENT CAN OCCUR.

 C.  Supply equipment cooling air (Ref 21-58-02/501 and 21-58-03/501).
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

 34-28-01

 ú ú 01 Page 106 ú Nov 15/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 D.  Make sure the systems that follow are operational:
 (1)
DADC (No. 1 and No. 2)

 (2)
EFIS

 (3)
Captain's RDDMI and first officer's RDDMI

 E.  Make sure the LANDING GEAR LATCH & AIR/GND relay circuit breaker, on the P6 circuit breaker panel, is closed.
 F.  Close these circuit breakers on the P6 and P18 circuit breaker panels:
 (1)
IRS (No. 1 and No. 2)

 (2)
DAA (No. 1 and No. 2)

 (3)
INST XFR

 (4)
INST XFMR (No. 1 and No. 2)

 (5)
VOR/ILS (No. 1 and NO. 2).

 (6)
VERT SPEED IND (captain's and first officer's)

 G.  Make sure the IRS, EFI, and VHF NAV switches are in the NORMAL position.
 H.  Tune the frequency on the VHF NAV control panels (P8) to 108.00.
 I.  Set the mode switches on the EFIS control panels to the VOR/ILS position.
 J.  Set the two mode selector switches on the IRS MSU to the ALIGN position.
 K.  Input the present position latitude and longitude coordinates into each IRS. You can use the IRS ISDU or the FMS CDU.
 NOTE: You can input local latitude and longitude after you set the mode
____ select switches on the IRS MSU to the ALIGN or NAV position.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. AIRPLANES WITH EFIS ú

 34-28-01
 ú ú 01 Page 107 ú Nov 15/92

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
FLIGHT DECK EFFECT  SIGNIFICANCE  RECOMMENDED ACTION 
FLASHING ALIGN LIGHT ON IRS MSU.  IRU CANNOT ACHIEVE ALIGN-MENT WITHOUT ADDITIONAL OPERATOR ACTION.  1. 2. 3. 4. 5. ENTER KNOWN ACCURATE PRESENT POSITION. IF ALIGN LIGHT IS STILL FLASHING, RE-ENTER THE IDENTICAL POSITION ENTERED IN STEP 1. IF ALIGN LIGHT IS STILL FLASHING, PLACE MODE SELECTOR SWITCH TO OFF. WAIT UNTIL ALIGN LIGHT GOES OUT (APPROXIMATELY 30 SEC). ENSURE THAT AIRPLANE IS NOT MOVING AND REPEAT THE 10-MINUTE ALIGN PROCEDURE. REPLACE IRU IF FAULT LIGHT COMES ON. 
ALIGN LIGHT ILLUMINATES STEADILY. ATT AND HDG FLAGS APPEAR ON FLIGHT INSTRUMENTS. AFTER 30 SECONDS, ATT FLAG DIS-APPEARS AND ALIGN LIGHT GOES OUT. ISDU DISPLAYS NO DATA OTHER THAN STATUS.  ATTITUDE MODE HAS BEEN NOTE:____ NAV CAPABILITY IS LOST WHEN MODE SELECTOR SWITCH IS PLACED TO ATT. SELECTED.  IF ATTITUDE MODE IS NOT DESIRED: PLACE MODE SELECTOR SWITCH TO OFF. WAIT UNTIL ALIGN LIGHT GOES OUT (APPROXIMATELY 30 SEC). RESTART THE 10-MINUTE ALIGNMENT PROCEDURE. IF ATTITUDE MODE IS DESIRED: ENTER MAGNETIC HEADING, USING THE ISDU, OR FMS CDU POS INIT PAGE 1/2. IF ISDU IS USED TO ENTER HEAD-ING, THE LETTER H MUST BE ENTERED FIRST. HEADING FLAGS WILL DISAPPEAR WHEN HEADING IS ENTERED. 
　
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