![]() ![]() Juan de la Cierva developed the fully articulating rotor for the autogyro. Three non-rotating control rods transmit pitch information to the lower swashplateĭiagram of fully articulated main rotor head.Swashplates, transmitting cyclic and collective pitch to the blades (the top one rotates).Rubber covers protect moving and stationary shafts.Scissor link and counterweight, carries the main shaft rotation down to the upper swashplate.This motion occurs whenever translational relative wind is present, or in response to a cyclic control input. Teeter hinge, allowing one blade to rise vertically while the other falls vertically.Pitch hinges, allowing the blades to twist about the axis extending from blade root to blade tip.The following are driven by the link rods from the rotating part of the swashplate.The simple rotor of a Robinson R22 showing (from the top): An example of such tips are the tips of the BERP rotors created during the British Experimental Rotor Programme. Tips of some helicopter blades can be specially designed to reduce turbulence and noise and to provide more efficient flying. As of 2010, research into active blade control through trailing edge flaps is underway. The Kaman K-MAX uses trailing edge flaps for blade pitch control and the Hiller YH-32 Hornet was powered by ramjets mounted on the blade ends. Rotorcraft blades are traditionally passive however, some helicopters include active components on their blades. Rotor blades are made out of various materials, including aluminium, composite structure, and steel or titanium, with abrasion shields along the leading edge. They generally contain a degree of washout that reduces the lift generated at the tips, where the airflow is fastest and vortex generation would be a significant problem. The blades of a helicopter are long, narrow airfoils with a high aspect ratio, a shape that minimizes drag from tip vortices (see the wings of a glider for comparison). The inner third length of a rotor blade contributes very little to lift due to its low airspeed. The hover efficiency ("figure of merit") of a typical helicopter is around 60%. As it is more efficient at low speeds to accelerate a large amount of air by a small degree than a small amount of air by a large degree, a low disc loading (thrust per disc area) greatly increases the aircraft's energy efficiency, and this reduces the fuel use and permits reasonable range. This permits a lower downwash velocity for a given amount of thrust. Unlike the small diameter fans used in turbofan jet engines, the main rotor on a helicopter has a large diameter that lets it accelerate a large volume of air. The rotors are designed to operate at a fixed RPM (within a narrow range of a few percent), but a few experimental aircraft used variable speed rotors. A rotor is a finely tuned rotating mass, and different subtle adjustments reduce vibrations at different airspeeds. There are three basic classifications: rigid, semirigid, and fully articulated, although some modern rotor systems use a combination of these classifications. Main rotor systems are classified according to how the main rotor blades are attached and move relative to the main rotor hub. The rotor blades are then attached to the hub, and the hub can have 10-20 times the drag of the blade. At the top of the mast is the attachment point (colloquially called a Jesus nut) for the rotor blades called the hub. The mast is a cylindrical metal shaft that extends upward from-and is driven by-the transmission. The helicopter rotor is powered by the engine, through the transmission, to the rotating mast. ![]()
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