LANDING GEAR, BRAKES, AND HYDRAULIC UTILITY SYSTEMS

Chapter Objective: Upon completion of this chapter, you will have a working knowledge of the maintenance required for the aircraft landing gear and brakes. You will have a working knowledge of the hydraulic utility systems, such as nose gear steering, catapult, arresting gear, skid control systems, and other related systems.

Maintenance on the landing gear and brakes, at times, requires maintenance of related systems. In this chapter, we will discuss the general landing gear systems and brake systems first, and then we will discuss various hydraulic utility systems. We will also examine drop checking procedures, troubleshooting, and the alignment and adjustment of the landing gear. The systems discussed in the following paragraphs are representative. For training purposes, we will use many values for tolerances and pressures to illustrate normal operating conditions. When actually performing the maintenance procedures discussed, you must consult the current applicable technical publications for the exact values to be used.

Learning Objective: Identify the various types of landing gear systems used on fixed-wing and rotary-wing aircraft.

Every aircraft maintained in todays Navy is equipped with a landing gear system. Most Navy aircraft also use arresting and catapult gear. The landing gear is that portion of the aircraft that supports the weight of the aircraft while it is on the ground. The landing gear contains components that are necessary for taking off and landing the aircraft safely. Some of these com-ponents are landing gear struts that absorb landing and taxiing shocks; brakes that are used to stop and, in some cases, steer the aircraft; nosewheel steering for steering the aircraft; and in some cases, nose catapult com-ponents that provide the aircraft with carrier deck takeoff capabilities.

Landing gear systems in fixed-wing aircraft are similar in design. Most aircraft are equipped with the tricycle-type retractable landing gear. Some types of landing gear are actuated in different sequences and directions, but practically all are hydraulically operated and electrically controlled. With a knowledge of basic hydraulics and familiarity with the operation of actuating system components, you should be able to understand the operational and troubleshooting procedures for landing gear systems.

The typical aircraft landing gear assembly consists of two main landing gears and one steerable nose landing gear. As you can see in figure 12-1, a main gear

Figure 12-1.Tricycle landing gear.

is installed under each wing. Because aircraft are different in size, shape, and construction, every landing gear is specially designed. Although main landing gears are designed differently, all main gear struts are attached to strong members of the wings or fuselage so that the landing shock is distributed throughout the main body of the structure. The main gears are also equipped with brakes that are used to shorten the landing roll of the aircraft and to guide the aircraft during taxiing.

On aircraft with tricycle landing gear, the nose gear is retracted either rearward or forward into the aircraft fuselage. Generally, the nose gear consists of a single shock strut with one or two wheels attached. On most aircraft the nose gear has a steering mechanism for taxiing the aircraft. The mechanism also acts as a shimmy damper to prevent oscillation or shimmy of the nosewheel. Since the nosewheel must be centered before it can be retracted into the wheel well, a centering device aligns the strut and wheel when the weight of the aircraft is off the gear. Damping, steering, and centering devices are discussed later in this chapter.