The pitch change rods that were seen earlier, in Figures 2 and 3, are controlled by the cyclic pitch lever and they are what change the pitch of the rotor blades. The difference in lift is caused by changing the blade angle, or pitch, of the rotor blades. When the cyclic pitch lever is pushed forward, the rotor blades create more lift as they pass through the back half of their rotation and less lift as they pass through the front half. The cyclic pitch control lever, like the yoke of an airplane, can be pulled back or pushed forward, and can be moved left and right. The collective pitch lever may have adjustable friction built into it, so the pilot does not have to hold upward pressure on it during flight. On many helicopters, the throttle automatically rotates and increases engine power as the collective lever is raised. The grip on the end of the collective pitch control is the throttle for the engine, which is rotated to increase engine power as the lever is raised. When the collective pitch control lever is raised, the blade angle of all the rotor blades increases uniformly and they create the lift that allows the helicopter to take off vertically. The collective pitch lever is on the side of the pilot’s seat, and the cyclic pitch lever is at the front of the seat in the middle. In the cockpit, there are two levers that control the main rotor, known as the collective and cyclic pitch controls. A NOTAR system is shown in Figures 8 and 9.Ĭontrol Around the Longitudinal and Lateral AxesMovement around the longitudinal and lateral axes is handled by the helicopter’s main rotor. The air exits the nozzle at a high velocity, and creates an additional force, or thrust, that helps counteracts the torque of the main rotor.
The remainder of the air travels back to a controllable rotating nozzle in the helicopter’s tail. The higher pressure on the left side of the boom creates the primary force that counteracts the torque of the main rotor. The fan forces air into the tail boom, where a portion of it exits out of slots on the right side of the boom and, in conjunction with the main rotor downwash, creates a phenomenon called the “Coanda effect.” The air coming out of the slots on the right side of the boom causes a higher velocity, and therefore lower pressure, on that side of the boom.
This system uses a high volume of air at low pressure, which comes from a fan driven by the helicopter’s engine. A third method of counteracting the torque of the helicopter’s main rotor is a technique called the “no tail rotor” system, or NOTAR.
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