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