(d)  Connect the borescope cable to the light source.
 1)  If the light is not sufficiently bright, adjust the intensity knob to make the light brighter.
 CAUTION: MAKE SURE THE ACTUATOR LEVER FOR THE DISTAL TIP IS IN THE
_______ NEUTRAL POSITION WHEN YOU INSTALL OR REMOVE THE BORESCOPE. THIS WILL PERMIT THE TIP TO MOVE FREELY IN THE GUIDE TUBE.
 CAUTION: MAKE SURE YOU LET 40 MINUTES GO BY AFTER AN ENGINE
_______ SHUTDOWN BEFORE YOU DO THE INSPECTION. DAMAGE TO THE BORESCOPE CAN OCCUR IF THE APU IS TOO HOT.
 (e)  
Slowly install the borescope tip into the guide tube while you look through the eyepiece. 1) Stop the installation when you can see the cooling fan.

 (f)  
Remove the two bolts and the washers that attach the crank cover to the load gearbox housing (View A, Fig. 601).

 (g)  
Remove the crank cover with the PWC 41350 puller. 1) Remove and discard the packing.

A
747-400 MAINTENANCE MANUAL
 (h) Attach a wrench to the square end socket of the gear shaft.
 CAUTION: MAKE SURE THE BORESCOPE DISTAL TIP DOES NOT ENGAGE THE
_______ COOLING FAN BLADES. DAMAGE TO THE BLADES AND THE BORESCOPE CAN OCCUR WHEN YOU TURN THE LOAD SECTION.
 (i)  Examine the fan rotor assembly while a different person slowly turns the load section with the wrench: 1) Visually examine the rotor assembly for the cooling fan to
 make sure it is in the inspection limits (Ref Fig. 602): a) Cracks in the cooling fan blades are not permitted. b) Nicks or dents larger than 0.125 inch (3.1 mm) on the
 leading edge and 0.50 inch (12.4 mm) below the blade
 tip are not permitted.
 c)  Nicks or dents less than 0.125 inch (3.1 mm) on the leading edge are permitted if you do a borescope inspection at the subsequent "A" check.
 (j)  
When you complete the inspection, carefully remove the borescope and the guide tube from the cooling fan housing.

 (k)  
Install a new packing, lubricated with engine oil, on the borescope inspection cover.

 (l)  
Install the borescope inspection cover on the cooling fan housing with the two washers and the nuts. 1) Tighten the nuts to 32-36 pound-inches (3.6-4.0 N.m).

 (m)  
If the load impeller and the power turbine inspections are not to be done at this time, install the crank cover: 1) Install a new packing, lubricated with engine oil, on the

 crank cover.
 2)  Install the crank cover on the load gearbox housing with the two washers and the bolts. a) Tighten the bolts to 36-40 pound-inches (4.0-4.5 N.m).
 S 296-005
 (5)  
Do the borescope inspection of the load impeller (Fig. 603):

 (a)  
Disconnect the P23 electrical connector from the T12
 temperature sensor.

 (b)  
Remove the T12 temperature sensor and the gasket from the housing. 1) Discard the gasket.

 (c)  
Manually retract the IGV actuator rod to fully open the inlet guide vanes.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A  A 747-400 MAINTENANCE MANUAL  T12 TEMPERATURE GASKET SENSOR 
SENSOR HOUSING INLET CASE 
CONNECTOR P23 ELECTRICAL 
A 
LOAD IMPELLER SEE A A 

SEE  B 
LOAD IMPELLER 
FWD  AREA INSPECTION  TUBE GUIDE  VANE GUIDE INLET VARIABLE 
Figure 603 (Sheet 1) Load Impeller Borescope Inspection A-A 

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