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A
747-400 FAULT ISOLATION/MAINT MANUAL

SELECT MODULE, CAPTAIN'S SOURCE M7991 (REF)  SELECT MODULE, F/O'S SOURCE M7995 (REF) 
C 

Inertial Reference System - Component Location
Figure 102 (Sheet 1)

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747-400
FAULT ISOLATION/MAINT MANUAL

E1 RACK
LEFT IRU SEE D
RIGHT IRU
SEE D

CENTER IRU SEE D
MAIN EQUIPMENT CENTER
TOTAL TIME FAULT INDICATOR INDICATOR (REF) (REF)
TEST SWITCH
1
(REF)
LEFT, RIGHT, CENTER INERTIAL REFERENCE UNIT, B7161, B7162, B7163
D
AIRPLANES WITH -110 IRUs AND SUBSEQUENT;
NO FAULT BALL INDICATOR IS INSTALLED. THE
CHASSIS INDICATOR HOLE CONTAINS A PLUG.

1
Inertial Reference System - Component LocationFigure 102 (Sheet 2)
F59801
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747-400 MAINTENANCE MANUAL
 INERTIAL REFERENCE SYSTEM - MAINTENANCE PRACTICES
_________________________________________________
 1.  General_______
 A.  This procedure contains one task. That task is the alignment of the inertial reference system (IRS).
 B.  The Honeywell IRS has a regular and a high latitude alignment.
 (1)  
A regular alignment is used between latitudes 70.2 degrees south to

 70.2 degrees north. A regular alignment takes 10 minutes.

 (2)  
A high latitude alignment is used between latitudes 70.2 degrees north to 78.2 degrees north and between latitudes 70.2 degrees south to 78.2 degrees south. A high latitude alignment takes 17 minutes.

 (3)  
Above 78.2 degrees north latitude and below 78.2 degrees south latitude, you cannot align the IRS.

 C.  You can align the IRS from the left or the right flight management computer (FMC) control display unit (CDU). You do not have to align the IRS from both the left and the right CDU. You only have to align the IRS from a single source.
 D.  You cannot move the airplane while you align the IRS.
 E.  The local latitude and longitude are necessary to align the IRS.
 TASK 34-21-00-712-088
 2.  IRS Alignment_____________
 A.  References
 (1)  AMM 24-22-00/201, Manual Control
 B.  Access
 (1)  Location Zones
 221 Flight Compartment, LH
 222 Flight Compartment, RH

 C.  Procedure
 S 862-080
 (1)  Make sure these circuit breakers are closed:
 (a)  P6 Main Power Distribution Panel
 1) 6D7 IRS LEFT AC

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747-400 MAINTENANCE MANUAL
 2) 6D8 IRS CENTER AC
 3) 6D9 IRS RIGHT AC
 4) 6E7 IRS LEFT DC
 5) 6E8 IRS CENTER DC
 6) 6E9 IRS RIGHT DC
 7) 6E32 C IRS DISCONNECT

 (b)  P7 Overhead Circuit Breaker Panel
 1) 7C1 FMCS FMC L
 2) 7C2 FMCS CDU L
 3) 7C4 FMCS A/T SERVO L
 4) 7E24 AUTO FLT WARN
 5) 7F8 UPR EICAS
 6) 7F9 EIU L
 7) 7F10 EIU C
 8) 7F15 EIU R

 S 862-083
 (2)  
Supply electrical power (AMM 24-22-00/201).

 S 862-087
　
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