Rotor System; Main Rotor; Main Rotor Head; Main Rotor Blades - Eads Eurocopter BO 105 CB-5 Flight Manual

EUROCOPTER
7.8

ROTOR SYSTEM

7.8.1 Main Rotor (see Fig. 7-11)
The main rotor ("System Bölkow") comprises a rigid-mounted head with four glassfiber
reinforced plastic (GRP) blades.
7.8.2 Main Rotor Head (see Fig. 7-11)
The rigid main rotor head is bolted directly to the main rotor mast and consists of a star
hub assembly and four blade-mounting forks with pitch horns. The hub assembly consists
of a single-piece cross-shaped drop forged titanium hub housing the blade retaining sys-
tem with tension-torsion straps and mounting the oil reservoir and feathering hinge bear-
ings. Each blade-mounting fork with inner sleeve assembly is inserted into an arm of the
hub and retained by a tension-torsion strap. The blade-mounting forks permit blade pitch
changes in response to flight control movements.
7.8.3 Main Rotor Blades (see Fig. 7-11)
Each main-rotor blade has an asymmetrical airfoil having a rectamgular plane-form in the
inner portion and a trapezoidal plane-form in the outer portion. The blade structure con-
sists of a skin, a C-spar and a core. The fiberglass prepeg skin has additional carbon fiber
laminates at the blade tip. For lightning protection, the carbon tip is covered with a copper
mesh. The C-spar is made of a unidirectional fiberglass rovings which form a loop around
the blade root to carry the centrifugal forces. The core of the blade is made of a hard
foam.
The blade leading edge is protected against erosion and foreign object damage by nickel
strips. A blade fitting assembly is bolted over the blade root and provides mounting of the
blade to the head. Two trim tabs are provided on the trailing edge of the outer portion of
each blade to allow for tracking adjustment.
Aerodynamic motions of lead/lag and flapping are absorbed by the blade inherent elastic-
ity. Each blade is fitted with pendulum absorbers near the root to reduce inflight vibrations.
7.8.4 Tail Rotor Assembly (see Fig. 7-12)
The tail rotor is of the semi-rigid teetering design. The two-bladed rotor fastened in a delta
hinged hub provides antitorque action and directional control. A titanium shaft having a
fork head and splined end houses two spherical teetering bearings and drives the rotating
part of the yaw control system sliding sleeve. The tail rotor shaft is splined to and driven
by the tail rotor output bevel gear.
Blade centrifugal forces are carried by laminated steel tension straps that attach outboard
to the blade mounting forks and inboard to a strap shoe which is held centered by the tail
rotor assembly mounting bolt. The blade mounting forks rotate about the hub on Teflon
bushings. Dynamic weights are installed on the control yoke to reduce control pedal
forces. These weights are adjusted to compensate for main rotor torque required at a
hover.
The tail rotor blades are constructed similar to the main rotor blades. The blades are re-
tained in the mounting forks by two bolts.
MANUFACTURER'S DATA
Rev. 0
FLIGHT MANUAL BO 105 CB-5/CBS-5
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