Yaw Damper Summing Lever
Figure 13
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(b) The yaw damper link is held fixed by the yaw damper servos which in turn hold the torque tube fixed. Primary and secondary control inputs from the ratio changer rotate about the torque tube along with the output rods. Yaw damper servo inputs cause the torque tube to rotate driving the output rods. Inputs from both the yaw damper servos and ratio changer control rods are combined to make the output to the PCAs.
(9) Power Control Actuator (PCA) (Fig. 12)____________________________
(a)
Each PCA is supplied hydraulic pressure by a separate system. Input to the PCA control valve comes from the yaw damper summing lever output, through the PCA linkages.
(b)
When the input lever is moved, hydraulic pressure is ported to either the retract or extend side of the piston. The opposite side is connected to the return line. As the piston drives the rudder surface, the reaction link backdrives the actuator body through the trunnion block. This action provides feedback to null out input command.
(c)
Counterclockwise rotation of the PCA input lever ports pressure to the retract side of the actuator which causes left rudder. Clockwise rotation of the PCA input lever ports pressure to the extend side of the actuator, which causes right rudder.
(10) Rudder Ratio Changer System (Fig. 14, 15 and 16)___________________________
TO CENTER
RUDDER PCA
AIRSPEED
SIGNAL LEFT RRCM
PRIMARY & SECONDARY
FROM SAM
CONTROL PATHS
ACTUATOR
AIRSPEED SIGNAL FROM SAM M528
(E3-1)
M529
MECHANICAL
HYDRAULIC
Ratio Changer Block Diagram
Figure 14
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OUTPUT CRANKS
TORQUE TUBE SEE A
INPUT CONTROL RODS
ACTUATOR INPUT
HIGH SPEED POSITION
TORQUE LOW SPEED
TUBE POSITION
RUDDER RATIO CHANGER SYSTEM RUDDER RATIO CHANGER SYSTEM
(LEFT SIDE VIEW) (TOP VIEW)
A B
Ratio Changer Operation
Figure 15
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E4-1
Ratio Changer Module Interface
Figure 16
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(a)
(b)
(c)
(d)
(e)
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The ratio changer system varies the amount of maximum rudder travel as a function of airspeed. The system provides structural protection and approximately constant rudder pedal response over the entire airplane operating speed range. The rudder ratio changer actuator (RCCA) is electrohydraulic and driven by two separate analog control channels.The RRCA mechanically varies the output of the ratio changer mechanism. In the low speed position, the RRCA is retracted and the left and right ratio changer cranks are swung out farther from the ratio changer torque tube axis of rotation. This increases the up or down control rod movement to the yaw damper as the torque tube rotates from control inputs. As airspeed increases, the RRCA is commanded to extend, causing the left and right cranks to swing inward. This decreases the control rod movement, which results in smaller control inputs to the yaw damper and PCAs. Rudder response varies from 30.6 degrees up to 127 knots to 3.5 degrees at 410 knots for full pedal travel.The rudder ratio changer system uses two digital air data computers (DADC), two stabilizer/elevator assymmetry modules (SAM), two rudder ratio changer modules (RRCM), a dual element LVDT and ratio changer mechanism. The system is arranged to form two independent computation channels, each of which can provide the rudder ratio changer function. The two channels each with one DADC, SAM, RRCM and pitot-static sensors operate in the active-standby mode and control the RRCA.Calibrated airspeed is sensed by the DADC and sent to the SAM unit. One DADC acts as the primary data source and the other as a secondary. Each DADC continuously monitors the pitot-static sensor data and self-monitors its own operation.Each SAM receives airspeed data from both DADCs. These signals are converted into two independent program airspeed signals Vpa and Vpc (designated ARM and CONTROL) and are sent to the corresponding RRCM. Each SAM monitors DADC data input, its own operation, and Vpa/Vpc agreement. Each SAM also generates a Vp VALID signal and sends it to the RRCM to signify its output is valid. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：757 AMM 飞机维护手册 飞行操纵 FLIGHT CONTROLS 1(136)
