the elevators by pulling back on the stick or yoke and lowers them by pushing the stick or yoke forward. The rudder is connected to the rudder pedals and is used to move the aircraft about the vertical axis. If the pilot moves the rudder to the right, the aircraft turns to the right; if the rudder is moved to the left, the aircraft turns to the left. The pilot moves the rudder to the right by pushing the right rudder pedal, and to the left by pushing the left rudder pedal. Power control systems are used on high-speed jet aircraft. Aircraft traveling at or near supersonic speeds have such high air loads imposed upon the primary control surfaces that the pilot cannot control the aircraft without power-operated or power-boosted flight control systems. In the power-boost system, a hydraulically operated booster cylinder is incorporated within the control linkage to assist the pilot in moving the control surface. The power-boost cylinder is still used in the rudder control system of some high-performance aircraft; however, the other primary control surfaces use the full power-operated system. In the full power- operated system, all force necessary for operating the control surface is supplied by hydraulic pressure. Each movable surface is operated by a hydraulic actuator (or power control cylinder) incorporated into the control linkage. In addition to the current Navy specification requiring two separate hydraulic systems for operating the primary flight control surfaces, specifications also call for an independent hydraulic power source for emergency operation of the primary flight control surfaces. Some manufacturers provide an emergency system powered by a motor-driven hydraulic pump; others use a ram-air-driven turbine for operating the emergency system pump. Lateral Control Systems Lateral control systems control roll about the longitudinal axis of the aircraft. On many aircraft the aileron is the primary source of lateral control. On other aircraft flaperons and spoilers are used to control roll. AILERON.—Some aircraft are equipped with a power mechanism that provides hydraulic power to operate the ailerons. When the control stick is moved, the control cables move the power mechanism sector. Through linkage, the sector actuates the control valves, which, in turn, direct hydraulic fluid to the power cylinder. The cylinder actuating shaft, which is con- nected to the power crank through a latch mechanism, operates the power crank. The crank moves the push-pull tubes, which actuate the ailerons. In the event of complete hydraulic power failure, the pilot may pull a handle in the cockpit to disconnect the latch mechanisms from the cylinder and load-feel bungee. This places the aileron system in a manual mode of operation. In manual operation, the cable sector actuates the power crank. This lateral control system incorporates a load-feel bungee, which serves a dual purpose. First, it provides an artificial feeling and centering device for the aileron system. Also, it is an interconnection between the aileron system and the aileron trim system. When the aileron trim actuator is energized, the bungee moves in a corresponding direction and actuates the power mechanism. The power mechanism repositions the aileron control system to a new neutral position. FLAPERON.—As aircraft speeds increased, other lateral control systems came into use. Some aircraft use a flaperon system. The flaperon, shown in figure 1-5, is a device designed to reduce lift on the wing whenever it is extended into the airstream. With this system, control stick movement will cause the left or right flaperon to rise into the airstream and the opposite flaperon to remain flush with the wing surface. This causes a decrease of lift on the wing with the flaperon extended and results in a roll. SPOILER/DEFLECTOR.—Many aircraft use a combination aileron and spoiler/deflector system for longitudinal control. The ailerons are located on the trailing edge of the outer wing panel and, unlike most aircraft, can be fully cycled with the wings folded. The spoiler/deflector on each wing operates in conjunction with the upward throw of the aileron on that wing. They are located in the left- and right-hand wing center sections, forward of the flaps. The spoiler extends upward into the airstream, disrupts the airflow, and causes decreased lift on that wing. The deflector extends down into the airstream and scoops airflow over the wing surface aft of the spoiler, thus preventing airflow separation in that area. A stop bolt on the spoiler bell crank limits movement of the spoiler to 60 degrees deflection. The deflector is mechanically slaved to the spoiler, and can be deflected a maximum of 30 degrees when the spoiler is at 60 degrees. The spoilers open only with the upward movement of the ailerons. 1-6