(a)  
Loosen the two screws in the rudder trim knob.

 (b)  
Remove the knob from the rudder trim switch.

 (c)  
Use a sponge and the detergent to clean the lightplate surface and the bottom surface of the trim knob (AMM 25-00-00/701).

 (d)  
Install the knob on the rudder trim switch.

 (e)  
Tighten the two knob screws.

 S 862-018
 (2)
Remove the DO-NOT-CLOSE tags and close these circuit breakers:

 (a)  
P7, Overhead Circuit Breaker Panel
 1) 7D16, RUD TRIM CONT

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747-400 MAINTENANCE MANUAL
 2) 7D17, AILERON TRIM
 S 862-019
 (3)  Remove the DO-NOT-OPERATE tags and put the the FLT CONTROL HYD POWER
 -TAIL switches No. 1, 2, 3 and 4 on the overhead panel to the ON position.
 S 712-020
 (4)  
Do the tests for the rudder trim system and the center switch in the operational test of the rudder trim control system (AMM 27-21-00/501).

 S 222-083

 (5)  
Make sure the trim switch knob is fully down on the trim switch shaft.

 F.
Put the Airplane Back to Its Usual Condition

 (1)  
Remove electrical power (AMM 24-22-00/201).

 S 862-022
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747-400 MAINTENANCE MANUAL
 RUDDER TRIM ACTUATOR - REMOVAL/INSTALLATION
___________________________________________
 1.  General_______
 A.  This procedure contains the removal and the installation tasks for the rudder trim actuator.
 B.  The rudder trim actuator is connected between the airplane structure and the feel, centering, and trim mechanism. Movement of the trim actuator turns the feel, centering, and trim mechanism and moves the rudder neutral position left or right.
 TASK 27-21-10-004-001
 2.  Rudder Trim Actuator Removal (Fig. 401)_______________________________________
 A.  Special Tools and Equipment
 (1)  
G12001-50 Rig Pin Kit

 B.  
References

 (1)  
AMM 06-09-07/201, Fin and Rudder Access Doors and Panels

 (2)  
AMM 24-22-00/201, Manual Control

 (3)  
AMM 29-11-00/201, Main Hydraulic Supply System

 (4)  
AIPC 27-21-11, Fig. 5

 (5)  
WDM 27-21-11

 C.  
Access

 (1)  
Location Zone 324 Vertical Stabilizer, Rear Spar to Trailing Edge

 (2)  
Access Panel
 324FL Inspection Access Panel
 324FR Centering Mechanism Access Panel

 D.  
Prepare for the Removal

 S 864-002
 (1)  Supply electrical power (AMM 24-22-00/201).
 S 864-003
 WARNING: MAKE SURE THAT PERSONS AND EQUIPMENT ARE CLEAR OF ALL CONTROL
_______ SURFACES BEFORE YOU SUPPLY HYDRAULIC POWER. AILERONS, RUDDERS, ELEVATORS, FLAPS, SPOILERS, LANDING GEAR, AND THRUST REVERSERS CAN MOVE QUICKLY WHEN YOU SUPPLY HYDRAULIC POWER. THIS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT.
 (2)  
Supply pressure to hydraulic systems No. 1 and 2 (AMM 29-11-00/201).

 S 864-036

 (3)  
Operate the rudder trim switch until the trim indicator shows zero units of trim.

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