have two, four, five, six, or seven blades. Figure 4-18
shows some typical rotor blades.
aluminum alloys, fiber glass, graphite, honeycomb
core, nickel, and steel. Each has a nitrogen-filled,
pressurized, hollow internal spar, which runs the length
of the blade. The cuff provides the attachment of the
blade to the rotor hub. A titanium abrasion strip covers
the entire leading edge of the spar from the cuff end to
the removable blade tip faring. This extends the life of
the rotor blade.
The examples shown in figure 4-18 show other
markings, and construction.
Main Rotor Head/Hub Assembly
The rotor head is fully articulating and is rotated by
torque from the engines through the drive train and
main gearbox or transmission. The flight controls and
hydraulic servos transmit movements to the rotor
blades. The principal components of the rotor head are
the hub and swashplate assemblies (fig. 4-19). The hub
is one piece, made of titanium and sits on top of the
rotor mast. Attaching components are the sleeve and
spindles, blade fold components, vibration absorber,
adjustable pitch control rods, blade fold hinges, balance
weights, antiflapping and droop stops, and faring.
The swashplate consists of a rotating disc (upper),
stationary (lower) portion with a scissors and sleeve
assembly separated by a bearing. The swashplate is
permitted to slide on the main rotor vertical driveshaft
and mounts on top the main transmission. The entire
assembly can tilt in any direction following the motion
of the flight controls.
The hydraulic servo cylinders, swashplate, and
adjustable pitch control rods permit movement of the
Figure 4-18.Types of main rotor blades.