500 Brake Control Linkage
Sep 20/82 Figure 2 (Sheet 2) 32-41-0
Page 5
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
Brake Metering Valve Schematic 500
32-41-0 Figure 3 Nov 15/71
Page 6
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
C. When the brake pedals are partially depressed for low braking pressure, brake pressure is directed to port 1 of the actuator through a hydraulic line downstream of brake metering valve (Fig. 8). This brake pressure will act against system A pressure coming from port 3. The differential pressure will be more and the check valve will remain open. The brake pressure from port 1 will be directed to act on head ends of the piston through slide assembly (Fig. 4). This pressure will cause the piston to move. The crank arm attached to the brake metering valve shaft will move with the movement of the brake input shaft to contact the piston causing it to move in the opposite direction of brake pressure applied on head ends of the piston thus increasing brake pedal resistance. The piston will move forward forcing brake pressure hydraulic fluid back to the slide assembly. This brake pressure will move slide assembly, controlled by a pressure regulator, thus compressing spring and opening the valve for return pressure.
D. When the brake pedals are fully depressed for high braking pressure, the brake pressure through port 1 will act against system A pressure coming from port 3. The differential pressure will be less or negligible. In this condition the spring-loaded check valve will move from open to the closed position thus preventing flow of hydraulic fluid through the actuator assembly. Brake pressure will not act on head ends of the piston but the crank arm will move with the brake input shaft thus contacting its roller with the piston. The piston will move without resistance as the brake pressure is not acting on head ends of the piston. So at maximum braking pressure pedal resistance will not be increased.
5. Main Gear Brakes
A. The main landing gear brake is a multidisk type consisting of four rotating and five stationary frictional elements called rotors and stators, respectively (Fig. 5). Two of the stators, referred to as pressure plate and torque tube backing plate, are lined on one surface with 13 lining blocks per surface. The remaining three stators are lined on both surfaces, with the same number of lining blocks per surface, and are notched on the inside diameter to enable then to fit and slide axially on the torque tube splines. The lining blocks are made from an inherently heat stable cerametallic material that will maintain its original strength and friction ability at incandescent temperatures. Each rotor is keyed to the wheel and consists of nine solid steel segments that are secured to a spider with keyed straps. The brake carrier houses six actuating pistons and four automatic adjuster assemblies with return springs. The cylinders for the actuating pistons are all hydraulically interconnected through drilled passages in the carrier. The piston housing provides two bleed ports to service the brake assembly.
591
Jun 20/84 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 32-41-0 Page 7
Brake Valve Feel Augmentation Actuator Schematic 500
32-41-0 Figure 4 Nov 15/68
Page 8
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
K42017
591 Main Gear Brake
Jun 20/84 Figure 5 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 32-41-0 Page 9
B. When the brakes are applied, hydraulic fluid under system pressure enters the inlet port of the brake, through a disconnect valve, and is distributed to the pistons. As the pistons move out, from the fluid pressure applied to them, they move the pressure plate axially against the stack of stators and rotors so that the stack is compressed between the pressure plate and the torque tube backing plate and rotational braking friction is developed. As the brake elements wear, the adjuster pin and ball assembly, attached to the pressure plate, is pulled through the adjuster tube (Detail A, Fig. 5). This movement forces the ball to expand the surrounding tube reducing an original interference fit between the ball and tube for a distance down the tube equal to the wear. When fluid pressure is released, the pressure plate is moved back by the return springs in the adjuster assemblies, thus allowing the rotors and stators to separate and rotate freely. The return spring pressure is enough to move the adjusting pin ball through the expanded portion of the adjuster tube but is not enough to force the ball through the interference portion. This maintains a constant running clearance throughout brake life. Separate lining wear indicator pins are provided at two places (Detail B). Dimension L is set at brake manufacture or overhaul. Subsequent lining wear will cause dimension L, with brake pressure applied, to decrease to a point indicating when the brake must be removed for lining replacement.
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