figure 4-20. These components are similar in function
to the main rotor.
The pylon, shown in figure 4-20, attaches on the
aircraft to the main fuselage by hinge fittings. These
hinge fittings serve as the pivot point for the pylon to
fold along the fuselage. Folding the pylon reduces the
overall length of the helicopter, which helps for
confined shipboard handling.
The pylon houses the intermediate and tail rotor
gearboxes, tail rotor drive shaft, cover, tail bumper,
position/anticollision lights, hydraulic servos, flight
control push-pull tubes/cables/bell cranks, stabilizer/
elevator flight control surface, some antennas, and
rotary rudder assembly.
Rotary Rudder Head
The rudder head can be located on either side of the
pylon, depending on the type of aircraft, and includes
such items as the hub, spindle, pitch control beam, pitch
change links, bearings, and tail rotor blades.
Change in blade pitch is accomplished through the
pitch change shaft that moves through the horizontal
shaft of the tail gearbox, which drives the rotary rudder
assembly. As the shaft moves inward toward the tail
gearbox, pitch of the blade is decreased. As the shaft
moves outward from the tail gearbox, pitch of the blade
is increased. The pitch control beam is connected by
links to the forked brackets on the blade sleeves.
Rotary Rudder Blades
Like the blades on a main rotor head, the blades
found on a rotary rudder head may differ, depending on
the type of aircraft. Tail rotor blades may consist of the
! Aluminum alloy, graphite composite, or
! Aluminum pocket and skin with honeycomb
core or cross-ply fiber glass exterior
! Aluminum or graphite composite tip cap
PITCH CHANGE LINK
ROTARY RUDDER BLADE
ROTARY RUDDER HUB
PITCH CONTROL BEAM
Figure 4-20.Tail rotor group.