G04119
Rudder Control System Component Location 526
27-21-0 Figure 1 Aug 15/69
Page 2
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
F. System A pressure is supplied by two engine-driven hydraulic pumps, one being located on each engine. System B pressure is supplied by two electric motor-driven hydraulic pumps. A and B flight control hydraulic modular units are identical in components and operation. Pressurized hydraulic fluid flows through the modular unit which consists of a spoiler shutoff valve, a flight controls shutoff valve, low pressure warning switch, compensator, and check valve. The flight controls shutoff valve controls the flow of hydraulic fluid to the ailerons, elevator, and rudder. When either the A or B flight control switch on the overhead panel is moved to STBY RUD the standby hydraulic system pump will start. The standby rudder actuator shutoff valve located in the standby hydraulic module will also open, porting hydraulic fluid to the standby actuator.
G. A rudder isolation shutoff valve is installed in the system A and the system B hydraulic lines between the respective system A and system B flight controls hydraulic modular units and the rudder power unit. The valve is part of the hydraulic isolation shutoff valves module, which consists of six hydraulic isolation valves. The valves are individually operated and provide a means of isolating individual hydraulic components for ground leakage and flow tests.
2. Rudder
A. The rudder provides yaw control for the airplane. It is a monospar, aluminum alloy structure with chordwise ribs. On some airplanes, the rudder is of graphite/composite construction. The skin is made of honeycomb core fiberglass. On some airplanes, the skin is made of graphite reinforced epoxy. There is no rudder tab. There are seven rudder hinges, the bottom one being a thrust hinge. Balance weights are fastened to the rudder nose. These are aluminum alloy forgings with steel castings attached. On some airplanes, the balance weights are made of tungsten. Refer to Structural Repair Manual, Chapter 51, for rudder balancing. There is a stainless steel body seal attached to the bottom rib of the rudder. On some airplanes, the body seal is made of honeycomb nomex core material. This seals the gap between the rudder and the body.
3. Rudder Pedals
A. The captain and first officer are each provided with a pair of rudder pedals which are used for controlling the airplane about its vertical axis (Fig. 1). Each pair of pedals consist of right and left pedals mounted on a shaft. The pedal shaft is attached to the upper end of the pedal arm assembly. The lower end of the pedal arm assembly is mounted on a support shaft which is attached to the structure below the floor. The rudder pedals are located below the captain's and first officer's instrument panel. Rudder pedal support and quadrant assemblies are accessible through the lower nose compartment.
B. Fore and aft movement of the pedals is transmitted by the two pushrods to the jackshaft yoke. The rotary motion of the jackshaft yoke is passed to the forward quadrant by means of the jackshaft. The two sets of rudder pedals are bussed together by means of a bus pushrod connecting the two jackshaft assemblies. Toe pressure on the rudder pedals causes pedals to rotate about their shafts and initiate braking action.
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Jun 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 27-21-0 Page 3
4. Rudder Pedal Adjustment Crank
A. The two pairs of rudder pedals can be adjusted independently to suit the captain and first officer. This is accomplished by means of the rudder pedal adjust shaft (Fig. 1). The rudder pedal adjustment mechanism consists of an adjustment crank, adjustment shaft, a jackscrew, and pedal adjustment nut attached to the jackshaft assembly.
B. The adjustment crank is located on the instrument panel forward of the control wheel. It is connected to a flexshaft routed forward under the instrument panel, then down under the floor, and aft to the universal joint in the rudder control jackshaft assembly. Rotation of the rudder pedal adjustment crank actuates the jackscrew which causes the yoke, containing the pedal adjustment nut, to move fore and aft.
C. Rudder pedal adjustment crank and crank handle stops are installed to prevent the rudder pedal adjustment screw from being backdriven by heavy foot pressure simultaneously applied to both rudder pedals. The crank incorporates a spring-loaded pin within the knob. The stops are incorporated into the crank housing bearing retainer. Rotation of the crank handle is prevented in either direction beyond the stop blocks, by contact of the spring-loaded pin that protrudes from the crank handle. To permit crank rotation for rudder pedal adjustment, the knob must be pulled aft so the pin clears the stops.
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