S 985-011

 (2)  
Push the left yaw damper engage switch on the yaw damper panel and make sure that the ON light comes on.

 (a)  Make sure that the left yaw damper INOP light is off.
 S 985-013
 (3)  Put the YAW DMPR test switch on the right side panel, P61, in the L position, then put the switch back to the center.
 (a) Make sure that the left yaw damper INOP light comes on.
 NOTE: The right yaw damper INOP light can also come on.
____
 (b)  
Make sure that the rudder position indicator on the lower EICAS display (Ref 31-41-00) shows this sequence of rudder movement in less than 10 seconds: 1) the rudder moves approximately 3 degrees trailing edge

 right 2) the rudder moves approximately 3 degrees trailing edge left 3) the rudder goes back to the center.

 (c)  
Make sure that the left yaw damper INOP light goes off in less than 15 seconds.

 S 985-014
 (4)  Push the right yaw damper engage switch and make sure that the ON light comes on.
 (a) Make sure that the right yaw damper INOP light is off.
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757 MAINTENANCE MANUAL
 S 985-016
 (5)  Put the YAW DMPR test switch in the R position then put the switch back to the center.
 (a) Make sure that the right yaw damper INOP light comes on.
 NOTE: The left yaw damper INOP light can also come on.
____
 (b)  
Make sure that the rudder position indicator on the lower EICAS display (Ref 31-41-00) shows this sequence of rudder movement in less than 10 seconds: 1) the rudder moves approximately 3 degrees trailing edge

 right 2) the rudder moves approximately 3 degrees trailing edge left 3) the rudder goes back to the center.

 (c)  
Make sure that the right yaw damper INOP light goes off in less than 15 seconds.

 S 285-018
 (6)  
AIRPLANES WITH YDM DASH NUMBERS -101 THRU -121; make sure that all faultballs on the front of yaw damper modules show black.

 S 985-021

 (7)  
AIRPLANES WITH YDM DASH NUMBERS -122 AND SUBSEQUENT;
 Do these steps:

 (a)  
Push the DISPLAY button on the left and right yaw damper modules.

 (b)  
Make sure that the message NO FAULTS or NO FAULT NOW shows on the display of the two modules.

 S 865-347
 (8)  Push and release the left and right yaw damper engage switches to disengage the yaw damper system.
 G. Put the Airplane Back to Its Initial Condition.
 S 865-023
 (1)  
Remove power from the left, center and right hydraulic systems (Ref 29-11-00).

 (2)
Remove electrical power if it is not necessary (Ref 24-22-00).

 S 865-024
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757 MAINTENANCE MANUAL
 S 865-922
 (3)  Put the L, C, and R FLT CONTROL SHUTOFF switches on the P61 panel in
 the OFF position.
 ú
 ú TASK 22-21-00-735-026
 ú3. AIRPLANES WITH YDM DASH NUMBERS -101 THRU -121;

 System Test - Yaw Damper System
_______________________________ GUNú A. General GUNú GUNúú NOTE:
____Verify the part number of the Yaw Damper Module before testing. ú
 (1)  
The system test makes sure these system interfaces operate correctly:

 (a)  
Yaw Damper Servos

 (b)  
Inertial Reference Units

 (c)  
Air Data Computers

 (d)  
EICAS

 (e)  
Air/Ground relays

 (f)  
Hydraulic pressure switches and sources

 (g)  
　
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