Even before the invention of the first working helicopter, the concept for one had been a fascination for engineers and deep thinkers all over the globe. With two or more large turbine engines on the wings or tail, it is easy to see how a fixed-wing aircraft moves forward, but helicopters rely on a different source for their thrust. In this blog, we will be discussing the working mechanics behind how a helicopter is able to create thrust and therefore move forward, to the right and left, and even backwards.
Overview of Helicopter Aerodynamics
Like fixed-wing aircraft, the three aerodynamic forces that affect helicopters are lift, thrust, and drag. Lift is the force that aircraft generate to fly upwards in the sky. Though the overall design is quite different, it is the airfoils on both fixed-wing airplanes and helicopters that generate lift. However, in a helicopter, the airfoils take the form of the rotary blades at the top of the vehicle. As these blades spin, they exert just enough lift to counteract gravity, even while remaining in a stationary hover with their main rotor blades and tail rotor spinning. In fixed-wing planes, thrust is produced directly through their engines. In contrast, helicopters convert lift into thrust when the main rotor tilt alters the lift vector. Finally, as with any aircraft, airflow across the body of a helicopter produces drag during flight. Therefore, helicopters must generate enough thrust and lift to counteract this drag and stay balanced in the air.
Helicopter Controls vs. Airplane Controls
Similar to fixed-wing planes, helicopters have a throttle as well as pedals, though they are used for the tail rotor rather than the rudder. However, the cyclic and collective controls are unique to rotary aircraft. The collective lever on the left side of the pilot controls the pitch of the main rotors. As the name would suggest, this pitch adjustment is made collectively to all the blades at once. These adjustments are used to move the helicopter vertically up and down. When the rotor pitch is increased, the helicopter climbs, and when it decreases, the helicopter descends. As increased pitch requires increased engine power to maintain the rotor speed, the collective control is also linked to the engine power.
The cyclic control affects the helicopter’s forward, backward, and side-to-side movements by way of a joystick positioned between the pilot’s legs. Like the collective, the cyclic control also adjusts the pitch of the main rotor blades, but instead of simultaneous adjustments, the cyclic control adjustments are made to each blade at the same point in its cycle. Lastly, the pedals on a helicopter are used to control the pitch of the tail rotor. The default pitch angle of the tail rotor is set to compensate for the helicopter’s natural right roll tendency that occurs because the rotor torque is oriented in a counterclockwise direction. Pressing the right foot pedal shifts the nose of the helicopter to the right, and the tail to the left, whereas pressing the left pedal moves the nose to the left and the tail to the right.
Though helicopters rely on the same forces to fly, they operate with different controls and design elements than fixed-wing aircraft. One of these significant differences is that helicopters exert thrust by tilting their main rotor rather than being directly pushed by the engine, as in a fixed-wing aircraft. To operate the various rotors onboard, helicopters depend on a system of crankshafts that are driven by the engine to translate lateral movement into rotation of the blades. Aviation Distribution is a leading supplier of crankshaft components and other rotorcraft parts which you can rely on for the long haul. If you are in need of high-quality parts such as this, we invite you to browse our ever-expanding inventory of aircraft parts which we provide to our customers with convenient shipping and cost savings. Start the purchasing process with us today to experience service that is catered to all your operational deadlines and procurement needs.
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