ADC IRS Rudder and Rudder Trim Control Figure 1
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 27-21-00
 ALL  ú ú 01 Page 1 ú May 20/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

 (1)  
The captain's and first officer's rudder pedals provide rudder control through a cable and linkage system to the power control actuators (PCAs) at the rudder. An electric actuator which repositions the feel and centering springs provides rudder trim control about system centered position. Trim switches on the aft electronic control panel P8 control the trim actuator. Three directional autopilot servos are also connected to the input controls. A rudder ratio changer system in the input linkage reduces rudder control commands as a function of airspeed. Yaw damper servo outputs, summed with other control inputs, provide a command signal to the PCAs.

 (2)  
The rudder is powered by the three hydraulic PCAs. Each PCA is independently supplied with pressure by one of three separate hydraulic systems. Any one PCA is capable of providing the required rudder travel.

 D.
Indication

 (1)  
Rudder position is indicated on the EICAS status page from the rudder position transmitter. A trim position indicator next to the rudder trim switch on aft electronic control panel P8 displays the amount of rudder trim. An amber RUDDER RATIO caution light and EICAS message identifies an inoperative ratio changer system. A yaw damper INOP light for each yaw damper indicates yaw damper inoperative or OFF.

 2. Component Details
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 A. Rudder Pedals (Fig. 2)
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 (1)  
Two sets of rudder pedals are located below the captain's and first officer's instrument panel. Each pair have rig pin holes R1 located in the pedal arms below the flight deck floor. Access to this area is through access door (113AL) forward of the nose gear wheel well. Pedal travel is limited to about 3.7 inches (94 mm) from neutral in each direction by stops on the two forward quadrant and jackshaft assemblies.

 B.
Forward Quadrant and Jackshaft Assembly

_______________________________________
 (1)  
An adjustable yoke is mounted on the aft side of each forward quadrant. The yoke is attached to the pedals by two control/push rods and is operated by a cable-driven jackshaft to provide fore and aft pedal adjustment. A bus rod ties both forward quadrants together, so either set of pedals provides input to both quadrants.

 (2)  
The quadrants are the forward terminal for the rudder cables. The left quadrant has stop bumpers that contact structural stops to limit pedal movement. The left quadrant also contains rig pin hole R2 which is used to rig the rudder pedals and set cable tension.

 C.
Pedal Adjustment Crank

______________________
 (1)  The captain's and first officer's adjustment cranks are found on the pedal cover front panel. The cranks adjust pedals independently of one another and are detented to retain position. Each crank turns a flex cable which drives the jackshaft yoke.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú

 27-21-00
 ALL  ú ú 01 Page 2 ú Jan 28/02
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A

757
MAINTENANCE MANUAL

SEE  B 
113AL ASEE  CRANKS ADJUSTMENT PEDAL  FIRST OFFICER'S RUDDER PEDALS 
HOLES R-1B RIG PIN 
(2 PLACES) FLEX CABLE  CAPTAIN'S PEDALS RUDDER  (2 PLACES) YOKE ADJUSTABLE (4 PLACES) ADJUSTABLE PUSH ROD 
R-1A HOLES RIG PIN  QUADRANT FORWARD 
ADJUSTMENT RUDDER PEDAL AFTFWD ACTUATING LINKAGE (REF) WHEEL BRAKE  HOLE R-2 RIG PIN  SEE  C  RB  RA 
B  A 
HOLE R-2 RIG PIN  FLEX CABLE FWD QUADRANT (2) RB-1  NUT JACKSHAFT SLIDING 
(NON ADJ) BUS ROD 
JACKSHAFT  YOKE ADJUSTABLE 
STOP QUADRANT  A  A-A 
A 
FLEX CABLE  C  Figure 2 Rudder Pedals and Jackshaft Assembly (REF) INTERCONNECT STEERING RUDDER PEDAL 

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