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2-44 Change 4
Section VIII MAIN AND TAIL ROTOR GROUPS
2.44 ROTOR SYSTEMS.
The rotor system consists of a main rotor and tail rotor. Both systems are driven by the engines through the trans-mission system, with pitch controlled by the .ight control system.
2.45 MAIN ROTOR SYSTEM.
The main rotor system consists of four subsystems: main rotor blades, hub, .ight controls and the bi.lar vibration absorber. Four titanium-spar main rotor blades attach to spindles which are retained by elastomeric bearings con-tained in one-piece titanium hub. The elastomeric bearing permits the blade to .ap, lead and lag. Lag motion is con-trolled by hydraulic dampers and blade pitch is controlled through adjustable control rods which are moved by the swashplate. When the rotor is not turning, the blades and spindles rest on hub mounted droop stops. Upper restraints called anti.apping stops retain .apping motion caused by the wind. Both stops engage as the rotor slows down during engine shutdown. Blade retaining pins can be pulled from the blade spindle joint and the blades folded along the rear of the fuselage. The bi.lar vibration absorber reduces rotor vibration at the rotor. The absorber is mounted on top of the hub and consists of a four arm plate with attached weights. Main rotor dampers are installed between each of the main rotor spindles modules and the hub to restrain hunting (lead and lag motions) of the main rotor blades during rotation and to absorb rotor head starting loads. Each damper is supplied with pressurized hydraulic .uid from a reservoir mounted on the side of each damper. The reservoir has an indicator that monitors the reserve .uid. When the damper is fully serviced, the indicator will show full gold.
2.45.1 Main Rotor Blades. Four main rotor blades use a titanium spar for their main structural member. The struc-ture aft of the spar consists of .berglass skin, Nomex hon-eycomb .ller and a graphite/.berglass trailing edge. The leading edge of each blade has a titanium abrasion strip, the outboard portion of which is protected by a replaceable nickel strip. Electro-thermal blankets are bonded into the blades leading edge for deicing. A Blade Inspection Method (BIMt) indicator (Figure 2-14), is installed on each blade at the root end trailing edge to visually indicate when blade spar structural integrity is degraded. If a spar crack occurs, or a seal leaks, nitrogen will escape from the spar. When the pressure drops below minimum the indicator will show red bands. A manual test lever is installed on each BIM indicator to provide a maintenance check. The blades are attached to the rotor head by two quick-release expandable pins, that require no tools to either remove or install. To conserve space, all blades can be folded to the rear and downward along the tail cone. When mooring, the blades can be tied down with a .tting on the bottom of each blade.
2.45.2 Main Rotor Gust Lock. The gust lock prevents the blades from rotating when the helicopter is parked. The gust lock is designed to withstand torque from one engine at IDLE, and thus allow engine maintenance checks inde-pendent of drive train rotation. The locking system consists of a locking handle at the rear of the cabin (Figure 2-5), a GUST LOCK caution legend on the caution/advisory dis-play (Figure 2-8), and a locking device and teeth on the tail rotor takeoff .ange of the main transmission. The lock shall only be applied when the rotor system is stationary; it can only be released when both engines are shut down. Power to operate the caution light is provided from the No. 1 dc primary bus through a circuit breaker marked LIGHTS ADVSY.
2.46 TAIL ROTOR SYSTEM.
A cross-beam tail rotor blade system provides anti-torque action and directional control. The blades are of graphite and .berglass construction. Blade .ap and pitch change motion is provided by de.ection of the .exible graphite .ber spar. This feature eliminates all bearings and lubrication. The spar is a continuous member running from the tip of one blade to the tip of the opposite blade. Electro-thermal blankets are bonded into the blade leading edge for deicing. The tail rotor head and blades are installed on the right side of the tail pylon, canted 20° upward. In addition to providing directional control and anti-torque reaction, the tail rotor provides 2.5% of the total lifting force in a hover. A spring-loaded feature of the tail rotor control sys-tem will provide a setting of the tail rotor blades for bal-ance .ight at cruise power setting in case of complete loss of tail rotor control.
　
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