MULTIPLE/TRIMETALLIC DISC BRAKES Multiple disc brakes are heavy-duty brakes designed for use with power brake control valves or power boost master cylinders. The brake assembly consists of a bearing carrier bearings and retaining nut; the annular actuating piston; and the heat stack, which is composed of a pressure plate, rotating discs (rotors), stationary discs (stators) and backup plate, an automatic adjuster, retracting springs, and various other components. Regulated hydraulic pressure is applied through the automatic adjuster to a chamber in the bearing carrier. The bearing carrier is bolted to the shock strut axle flange and serves as a housing for the annular actuating piston. Hydraulic pressure forces the annular piston to move outward, compressing the rotating discs, which are keyed to the landing wheel, and the stationary discs, which are keyed to the bearing carrier. The resulting friction causes a braking action on the wheel and tire assembly. When the hydraulic pressure is relieved, the retracting springs force the actuating piston to retract into the housing chamber in the bearing carrier. The hydraulic fluid in the chamber is forced out by the return of the annular actuating piston, and is bled through the automatic adjuster to the return line. The automatic adjuster traps a predetermined amount of fluid in the brake–an amount just sufficient to give correct clearances between the rotating discs and stationary discs. See figure 12-33. The trimetallic disc type brakes are used on most naval aircraft. They operate on the same basic principle as the multiple disc brakes and will be discussed in detail later in this chapter. SEGMENTED ROTOR BRAKES Segmented rotor brakes are heavy-duty brakes, especially adapted for use with high-pressure hydraulic systems. These brakes may be used with either power brake control valves or power boost master cylinders. Braking is accomplished by means of several sets of stationary, high-friction type of brake linings making contact with rotating (rotor) segments. A cutaway view of the brake is shown in figure 12-34. As you can see, the segmented rotor brake is very similar to the multiple disc type, described in the previous section. The brake assembly consists of a carrier, two pistons and piston cup seals, a pressure plate, an auxiliary stator plate, rotor segments, stator plates, a 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. Carrier assembly Piston cup (outer) Piston cup (inner) Piston (outer) Piston (inner) Piston end (outer) Piston end (inner) Pressure plate Stator drive sleeve Auxiliary stator and lining assembly Rotor segment Rotor link Stator plate Backing plate 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. Torque pin Adjuster pin Adjuster clamp Adjuster screw Adjuster washer Adjuster return spring Adjuster sleeve Adjuster nut Clamp holddown assembly Shim Bleeder screw Drive sleeve bolt Dust cover (inner) Dust cover (outer) Figure 12-34.-Segmented rotor brake–cutaway view. compensating shim, automatic adjusters, and a backing plate. BRAKE SYSTEM MAINTENANCE Learning Objective: Identify the two primary brake systems and the checks required to make sure these systems operate properly. Brake systems are designed to retard or to stop aircraft motion on the ground. They also aid in controlling the direction of the aircraft while it is taxiing. Provisions exist for applying either one or both brakes 12-39