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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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747-400
MAINTENANCE MANUAL
9. Feel and Centering Mechanism
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A. The rudder feel and centering mechanism transfers rudder pedal or rudder trim input through linkage rods to the upper and lower rudder PCMs, through the RRCs. Rudder pedal feel is provided by a centering cam and roller mechanism. The centering and feel assembly consists of a shaft, torque tube, centering cam, input crank, two output cranks, rudder trim coordinating crank, two springs, and cam roller arm. The shaft is connected to the vertical stabilizer structure and the rudder trim coordinator rotates about it. The torque tube, with the input, output, and centering cam attached to it, rotates about the shaft independent of the trim coordinators. The trim coordination crank and cam-roller arm are attached. The cam roller is spring-held to ride on the centering cam providing a pedal feel force. The rudder trim coordination crank is normally held stationary by the trim actuator.
10. Rudder Ratio Changer
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A. The upper and lower rudder ratio changer systems are each composed of two separate units, SRM in the E/E rack and a servo unit, interconnected electrically to form an electromechanical closed servo loop. Each servo unit contains a jackscrew, a gear train, an electric motor and two positional potentiometers.
B. Both ratio changer control systems are installed in the vertical fin close to their associated PCP. The RRC control system consists of an input crank, a trunnion, output crank, and a servo unit. The input crank is fixed to the trunnion. The trunnion is mounted with bearings in brackets attached to the fin. The bearings serve as axis of rotation for input and output of the ratio changer. The output crank is mounted in a yoke of the trunnion. The mounting in the yoke of the trunnion permits movement of the output crank for changing the effective moment arm to the lever leading to the main valve of the PCP. The output crank has two arms. One arm connects by a swivel joint to the servo unit and the other arm connects by a linkage to the summing lever on the PCM.
C. The servo unit receives electrical inputs from the stabilizer trim/rudder ratio module (SRM) to produce changes in the overall length of the servo unit through the electric actuator. The change in length is proportional to the airspeed input (Vc) at the SRM module. The electrical inputs from the SRM limit rudder travel from 31.5 degrees with no load, to approximately 7 degrees above 367 knots.
11. Upper Rudder Power Control Package
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A. The upper rudder power control package (PCP) consists of a PCM, three hydraulically driven PCAs, mounting trunnions, and associated hydraulic connections. The PCM consists of a triple spool valve, yaw damper actuator, solenoid valve, and position transducer. Airplane hydraulic systems No. 1 and 3 supply the upper rudder PCM. The PCM then regulates flow to the three PCAs attached to the rudder front spar. Replaceable filters in the PCM protect the unit from contamination.
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27-21-00
ALL ú ú 02 Page 8 ú Jun 18/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
12. Lower Rudder Power Control Package
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