TM 1-1520-240-10
2-8-1/(2-8-2 blank)
SECTION VIII. ROTOR SYSTEM
2-8-1. General.
Lift is produced by a rotor system consisting of two fully
articulated counter-rotating rotors. Each rotor has three
fiberglass blades. The forward rotor is driven by the for-
ward transmission through a rotor drive shaft. The aft
rotor is driven by the aft transmission through a vertical
drive shaft.
The rotor head consists of a hub connected to three
pitch-varying shafts by three horizontal hinge pins.
These pins permit blade flapping. Stops on the top and
bottom of the hub limit the blade flapping motion. The aft
rotor head is equipped with centrifugal droop stops which
provide increased blade flapping angle for ground and
flight operation.
Covers may be installed on the centrifugal droop stop
operating mechanism. The covers prevent ice accu-
mulation on the mechanism and ensure proper droop
stop operation following flight in icing conditions. For in-
formation on use of the droop stop covers, refer to Chap-
ter 8, Section IV.
Mounted coaxially over the pitch-varying shafts are pitch-
varying housings to which the blades are attached by
vertical hinge pins. These pins permit blade leading and
lagging. Each pitch-varying shaft is connected to the
pitch-varying housing by a laminated tie bar assembly.
The high tensile strength and low torsional stiffness of the
tie bar retains the blade against centrifugal force and
allows blade pitch changes about the pitch axis.
Blade pitch changes are accomplished by three pitch-
varying links connected from the rotating ring of the
swashplate to the pitch-varying housing on each rotor
blade. Cyclic pitch changes are accomplished by tilting
the swashplate. Collective pitch changes are accom-
plished by vertical movement of the swashplate. Com-
bined collective and cyclic pitch change result from com-
bined control inputs by the pilot.
A direct-action shock absorber is attached to the blade
and to the pitch-varying housing. When the inboard end
of the shock absorber is disconnected, the blade can be
folded in either direction about the vertical hinge pin.
2-8-2. Rotor Blades.
a.
Each rotor blade consists of D-shaped fiberglass
spar assembly and a Nomex fairing assembly bonded to
the spar. The blade chord is 32 inches.
b.
A titanium nose cap is bonded to the leading edge
of the spar. A nickle erosion cap is bonded to the blade
along the outer 54 inches of leading edge. This cap pro-
tects the part of the blade most vulnerable to erosion.
c.
The fairing assembly is bonded to the trailing
edge of the spar. These fairings are constructed of a
Nomex honeycomb core covered with fiberglass skin.
Wire mesh screens are embedded in the fiberglass skin
at the tip and the trim tab. the wire mesh screens provide
an electrical path to the rotor hub from the metal trim tab
and tip for lightning protection. Also, to provide lightning
protection, each blade has two lightning cables and two
straps. The cables and straps complete the path from the
wire mesh to the rotor head.
d.
Balance and tracking weights are installed in the
tip of spar and fairing assembly. The tracking weights are
removable and are used for blade track and balance.
2-8-3. Rotor Tachometers.
Two rotor tachometer (16, fig. 2-1-7 and fig. 2-1-9), one
mounted on the pilot instrument panel, the other
mounted on the copilot instrument, indicate percent of
rotor revolutions per minute (RRPM). A small needle on
the tachometer indicates percent RPM from 0 to 60. The
large needle indicates percent RPM from 60 to 130. The
RRPM sense signal is supplied by the AC generators.
generator No. 1 supplies the copilot indicator and gener-
ator No. 2 supplies the pilot indicator. Power to operate
the indicators is supplied by the DC essential bus through
the ROTOR TACH circuit breaker on the No. 1 and No.
2 PDP.
