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
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.
4. Pitch control beam
Rotary rudder blade
5. Rotary rudder hub
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
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
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