(3)
Spoilers No. 6 and 7 have three positions (full down, 20 degrees, and 45 degrees).
E.
With both the spoiler and speed brake systems operating the same five outboard spoiler panels, the input from one system will modify the position of the surfaces as determined by the other system. The final surface position is determined by the spoiler differential which provides the single output to control the flight spoiler power control packages. Spoiler position is further modified by aerodynamic loads on the spoiler surfaces. When these forces cause hydraulic pressure within the power control packages to reach maximum values, the hydraulic pressure is relieved prohibiting further spoiler travel or permitting spoiler blow-down.
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3. Rudder Control System (Fig. 6)
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A. Two rudders located at the trailing edge of the vertical fin provide directional control of the airplane. The rudder control system is controlled from rudder pedals in the flight compartment. Forward control quadrants and cables transmit the pedal motion to an aft control quadrant in the vertical fin. Motion of the aft quadrants then positions the rudder ratio changers which provide input to the power control module at each rudder. The power control modules also receive input from the yaw damper system (Ref 22-21-00/001), and the rollout power packages receive input from the autopilot system (Ref 22-13-00/001).
B. Rudder pedals can be adjusted fore and aft to satisfy pilot requirements. This is accomplished by a pedal adjustment mechanism located in the flight compartment.
C. Available travel of the rudders is controlled by rudder ratio changers in the power control package input mechanism. Maximum travel of the rudders is available at low speeds and is reduced as airplane speed increases. This is accomplished by changing the ratio of pedal travel to power control package input. Rudder ratio changer position is determined by "q" pressure from a pitot-static system.
D. Rudder trim, centering and artificial feel are provided by a feel and centering mechanism connected to the aft control quadrant. Rotation of the rudder trim control switch on the pilots' control stand operates an electric trim actuator which positions the mechanism to give a new system neutral position, thus providing the trim correction. A spring in the mechanism provides the centering and feel forces.
4. Pitch Control System (Figs. 7 and 8)
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A. Four elevators located at the trailing edge of the horizontal stabilizer provide primary pitch control of the airplane. The elevator control system is controlled from columns located in the control cabin. This input from the control columns is transmitted mechanically through cables and linkages to a hydraulically powered elevator power control package (PCP) located forward of each inboard elevator. The PCPs contain control valves and actuators which position the elevators. Movement of the inboard elevator operates a series of control rods and levers providing an input to the outboard elevator PCP. The outboard elevator is then positioned by an actuator located within its PCP. Each outboard elevator responds to its respective inboard elevator. Elevator feel at the control column is provided by a feel unit connected mechanically to the elevator aft quadrants. This feel force is related to airplane speed and is controlled by "q" pressure and stabilizer position. Autopilot input to the elevator control system is received by the elevator autopilot servo control modules (Ref 22-12-00/001).
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B. The horizontal stabilizer is positioned to provide pitch trim. Stabilizer trim is set by a hydraulically powered drive mechanism. Primary control of stabilizer trim is from switches on each aileron control wheel. The switches provide input to two stabilizer trim/rudder ratio modules (SRM) in the main electrical equipment center. The SRMs compute required stabilizer trim position and command the stabilizer trim control modules (STCM) in the empennage to move the stabilizer. The SRMs also receive autopilot input for stabilizer position (Ref 22-22-00/001). The STCMs regulate the flow of hydraulic fluid to the hydraulic motors and brakes at the stabilizer drive mechanism. Stabilizer movement can be stopped by interruption of the electrical command to the STCMs if the control column is moved more than a small amount in a direction opposed to the trim direction. Alternate stabilizer trim switches on the pilots control stand bypass the SRMs and allow direct control of stabilizer trim. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：747-400 AMM 飞机维护手册 飞行操纵 FLIGHT CONTROLS 1(15)
