The nose gear is steered by an electrically controlled, hydraulic powered steering cylinder which is mounted on the nose gear recoil strut. The cylinder is connected through mechanical linkage to an eccentrically mounted drive stud on the recoil strut inner cylinder.

This nose steering system is mechanically con-trolled and hydraulically actuated in much the same manner as an electrically controlled nose steering system. The steering actuator is of a different design but serves the same dual function of providing steering and dampening, when steering is not engaged.

Steering on the typical aircraft is accomplished by swiveling the lower portion of the nosewheel shock strut. A rotary-vane type of hydraulic steering unit is mounted on the fixed portion of the shock strut, and is linked to the swiveling portion to which the nosewheel, or wheels, arc attached. The nosewheel steering power unit, shown in figure 12-13, uses gears. The steering range varies with each aircraft. For specific degrees of steering range for a particular model of aircraft, you must consult the applicable MIM. For turns requiring a greater steering angle, the pilot can usually use differential braking, in which case the steering unit is

automatically disengaged and the nosewheel, or wheels, swivel freely.

A typical hydraulic steering unit (fig. 12-14) has built-in valves and a follow-up system, and auto-matically reverts to the shimmy damper mode when not being used as a steering actuator. The valve varies with the type of aircraft. One method is by means of mechanical linkage tied directly to the rudder pedals. Gearing, through a caroming arrangement, gives the necessary sensitivity range, permitting satisfactory maneuvering of the aircraft through all speed ranges and turn rates.

Methods of arming or activating the steering systems of the various aircraft used in naval aviation are numerous, and for convenience, a typical aircraft that has capabilities for both land- and carrier-based operations is discussed.

During land-based operation, steering is armed or activated by the pilot. During shipboard operations, the

steering system is armed or activated automatically by a switch actuated by the arresting hook when it is extended. Both switches work in conjunction with a weight-on-gear proximity switch (scissor switch) located on one of the main landing gears. When the strut is compressed a certain amount, the scissor switch completes the electrical circuit to activate the nosewheel steering. Nosewheel steering is desired for carrier landing operations to prevent the nosewheel, or wheels, from swiveling during rollback after arrestment.