ARRESTING GEAR

Figure 1-13.—Nose gear assembly. Nose Gear A typical nose gear assembly is shown in figure 1-13. Major components of the assembly include a shock strut, drag struts, a retracting mechanism, wheels, and a shimmy damper. The nose gear shock strut, drag struts, and retracting mechanism are similar to those described for the main landing gear. The shimmy damper is a self-contained hydraulic unit that resists sudden twisting loads applied to the nosewheel during ground operation, but permits slow turning of the wheel. The primary purpose of the shimmy damper is to prevent the nosewheel from shimmying (extremely fast left-right oscillations) during takeoff and landing. This is accomplished by the metering of hydraulic fluid through a small orifice between two cylinders or chambers. Most aircraft are equipped with steerable nose- wheels and do not require a separate self-contained shimmy damper. In such cases, the steering mechanism is hydraulically controlled and incorporates two spring-loaded hydraulic steering cylinders that, in addition to serving as a steering mechanism, auto- matically subdue shimmy and center the nosewheel. For more information concerning landing gear components (shock struts, shimmy dampers, power steering units, and brakes), you should refer to chapter 12 of this TRAMAN. ARRESTING GEAR A carrier aircraft is equipped with an arresting hook for stopping the aircraft when it lands on the carrier. See figure 1-14. The arresting gear is composed of an extendible hook and the mechanical, hydraulic, and pneumatic equipment necessary for hook operation. The arresting hook on most aircraft is mechanically released, pneumatically lowered, and hydraulically raised. The hook is hinged from the structure under the rear of the aircraft. A snubber, which meters hydraulic fluid and works in conjunction with nitrogen pressure, is used to hold the hook down to prevent it from bouncing when it strikes the carrier deck. 1-14