(b)  
Set the APU battery switch on the P5 panel to the ON position.

 (c)  
Set the APU control switch on the P5 panel to the ON position.

 (d)  
Make sure the EICAS message APU DOOR shows after 60 seconds.

 (e)  
Close the AIR INLET DOOR circuit breaker on the P83 panel in the E8 aft equipment center.

 (f)  
Make sure the EICAS message APU DOOR does not show after 30 seconds.

 (g)  
Set the APU control switch on the P5 panel to the OFF position.

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747-400 MAINTENANCE MANUAL
 APU AIR INLET - INSPECTION/CHECK
________________________________
 1.  General_______
 A.  This procedure gives the steps to examine these items:
 (1)  
The acoustic material of the air inlet plenum

 (2)  
The air inlet screens

 (3)  
The position switch on the air inlet door.

 B.  
You can get access to the inner part of the air inlet plenum through the three access doors. The three access doors are on the top, aft side of the air inlet plenum. You can get access to the position switch for the inlet door through the APU access doors. The position switch is on the forward, lower side of the APU inlet duct.

 TASK 49-15-00-206-023
 2.  Examine the Plenum Acoustic Material and the Screens of the Air Inlet_____________________________________________________________________
 A.  Standard Tools and Equipment
 (1)  
Brush - Bristle, Soft

 B.  
References

 (1)  
49-11-01/401, Auxiliary Power Unit

 (2)  
IPC 49-15-01 Fig. 1

 C.  
Access

 (1)  
Location Zone 317 APU Compartment-Upper Aft Side of Air Inlet Plenum, LH 318 APU Compartment-Upper Aft Side of Air Inlet Plenum, RH

 (2)  
Access Panel
 317AL APU Access Door
 318AR APU Access Door

 D.  
Prepare to Examine the Plenum Acoustic Material and the Screens of the Air Inlet.

 S 866-001
 (1)  
Make sure the APU control switch, on the P5 panel, is OFF and attach a DO-NOT-OPERATE tag.

 S 866-002

 (2)  
Open these circuit breakers and attach DO-NOT-CLOSE tags:

 (a)  
P6 Main Power Supply Panel
 1) 6K18 APU ALTN CONT

 (b)  
P83 Panel, E8 Aft Equipment Center
 1) APU PRIMARY CONT

 S 016-003
 (3)  
Open the APU access doors.

 (a)  
Open the latches on the APU access doors.

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747-400 MAINTENANCE MANUAL
 (b)  
Open the APU access doors.

 (c)  
Engage the support rods for the APU access doors.

 S 036-004
 (4)  
Loosen the turnlock fasteners on the three access panels on the top, aft side of the inlet plenum.

 S 016-005

 (5)  
Remove the plenum access panels.

 NOTE: Let the access panels hang from the tethers on the inlet
____
 plenum.

 E. Examine the Plenum Acoustic Material and the Screens of the Air Inlet.
 S 216-006
 (1)  
Do these steps to examine the air inlet screens:

 (a)  
Remove all the unwanted objects from the inlet screen area

 (b)  
Clean the inlet screens with a clean, soft-bristle brush

 (c)  
Visually examine the mesh for damage in the primary screen area and at the flanges.

 NOTE: If the inlet screen is damaged, a borescope inspection
____ of the load and high impeller is recommended (AMM 49-21-00/601).
 S 216-007
　
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