end of the blade contains a readily removable tip cap. Screws fasten the spar and tip pocket rib together. The root pocket of the blade is sealed at its inboard end by an aluminum alloy root cap that is cemented and riveted to the pocket. A stainless steel spar abrasion strip is found at the leading edge of the spar. It starts at blade pocket No. 10 and  extends  along  the  entire  leading  edge,  which includes the tip cap. The blade shown in figure 1-17 is fitted with a ice guard. The guard is composed of fine wire braid heating elements. It is interwoven in bands and embedded in a rubber strap, to which is bonded a stainless steel strap. The guard is bonded to the leading edge of the spar, and is molded to the contour of the blade. Rotor Head The rotary-wing head is splined to and supported by the rotary-wing shaft of the main gearbox. The head supports  the  rotary-wing  blades.  It  is  rotated  by  torque from the main gearbox, and transmits movements of the flight  controls  to  the  blades. The principal components of the head are the hub and swashplate. The hub consists of a hub plate and lower plate. It has hinges between each arm of the plates and sleeve-spindles, which are attached to the hinges. There is also a damper-positioner for each wing blade. The  swashplate  consists  of  a  rotating  swashplate  and stationary   swashplate.   Other   components   of   the rotary-  wing  head  are  anti  flapping  restrainers,  droop restrainers, adjustable pitch control rods, and rotating and stationary scissors. The  swashplate  and  adjustable  pitch  control  rods permit movement of the flight controls to be transmitted to the rotary-wing blades. The hinges allow limited movement  of  the  blades  in  relation  to  the  hub.  These movements are known as  lead, lag, and flap. Lead occurs during slowing of the drive mechanism when the blades have a tendency to remain in motion. Lag is the opposite  of  lead,  and  occurs  during  acceleration  when the blade has been at rest and tends to remain at rest. Flap is the tendency of the blade to rise with high-lift demands as it tries to screw itself upward into the air. The damper-positioners restrict lead and lag motion and position the blades for folding. Sleeve-spindles allow each blade to be rotated on its spanwise axis to change the  blade  pitch.  The  antiflapping  restrainers  and  droop restrainers   restrict   flapping   motion   when   the rotary-wing head is slowing or stopped. 1. 2. 3. Pitch  link 4. Pitch control beam Rotary  rudder  blade 5. Rotary rudder hub Spindle 6. Pylon Figure 1-18.—Tail rotor group. TAIL ROTOR GROUP The tail rotor group has helicopter components that provide the aircraft with directional control. See figure 1-18.  These  components  are  the  pylon,  rotary  rudder blades, and rotary rudder head. The rotary rudder head includes such items as the hub, spindle, and pitch control beams. Pylon The pylon, shown in figure 1-18, is of aluminum semimonocoque  construction.  It  has  beams,  bulkheads, stringer,  formers,  and  channels.  Various  gauges  of aluminum skin located on the sides of the box structure are part of the primary pylon structure. Reinforced plastic fairings in the leading and aft surfaces form the airfoil contour of the pylon and are secondary structures. The pylon houses an intermediate gearbox and a tail gearbox. The pylon is attached on the right side of the aircraft  to  the  main  fuselage  by  hinge  fittings.  These hinge fittings also serve as the pivot point for the pylon to fold alongside the right side of the fuselage. Folding of  the  pylon  reduces  the  overall  length  of  the  H-3 helicopter  by  7  1/2  feet,  thereby  aiding  shipboard handling. Rotary  Rudder  Head The  rudder  head  is  usually located on the left side of the pylon. It produces antitorque forces, which may be varied by the pilot to control flight heading. The 1-18