Future of Rotorcraft
The first few ideas of vertical flight can be traced back to 400 BC in China where children used to play with Chinese tops that consisted of feathers attached at the end of a stick which was spun rapidly between their hands which generated lift. During the past 70 years since their first success in flights, helicopters have matured from unstable, vibrating mechanisms that could barely produce any lift from the ground, into sophisticated machines of war for the military as well as many civilian usages. There is an absolute need for these special aircrafts due to their advantages over fixes wing aircrafts; they able to hover, fly backwards and side wards, perform other desirable manoeuvres and land in areas inaccessible to fix wing aircrafts and ground vehicles. In the modern world today, helicopters play important civilian roles which encompass basic transportation of goods, humanitarian aids, police surveillance, corporate services and fire fighting. Military roles of the helicopter include ground troop transport, battlefield surveillance and assault missions. In various operations, the helicopter has saved the lives of over a million people. Over the last few decades, intensive and sustained scientific researches and developments in many different aeronautical disciplines have allowed for improvements in helicopter performance; lifting capability, high speed cruising efficiencies, manoeuvrability and mechanical reliability. Continuous aerodynamic improvements to the efficiency of the rotor have allowed the helicopter to lift more than its empty weight itself and fly in speeds in excess of 200 knots. Since post world war two, there has been an accelerating scientific effort to understand and overcome some of the most difficult technical problems related to a helicopter’s flight, particularly in regards to aerodynamic limitations imposed by the main rotor. One of the first problems helicopter designers encountered when they first attempted to build a machine that could hover was the problem of torque reaction. Newton's third law of motion states that for every action there is an equal and opposite reaction. A typical single main rotor helicopter has a rotor system mounted on a rotor mast. The helicopter engine supplies power to the rotor mast which turns it and the rotor system connected to it. When the helicopter applies torque to the mast to spin it, there is an equal-and-opposite torque reaction which tries to turn the helicopter in the opposite direction which makes it impossible for any stability during flight.
Due to the nature of this physics limitation, all configuration designs of helicopters have been made to tackle this problem by introducing a counter reacting force to prevent the aircraft from spinning out of control. The following 3 main types of rotor configuration: 1) single rotor, 2) coaxial rotor and 3) tandem type rotor are currently the most widely used. Igor Sikorsky was the first Russian man to invent the first successful single rotor helicopter which was massed produced in the 1940s called the Sikorsky R-4. Today, the single main rotor configuration is the most common design in the world, compared to the others. We will now discuss the merits of a single rotor compared to tandem and coaxial type’s configuration, putting into consideration their mechanical complexity, aerodynamic performance, handling qualities, maintenance issues and last but not least, cost. Coaxial rotors are a pair of rotors mounted one above the other on concentric shafts, with the same axis of rotation, which turn in opposite directions. Tandem rotors have two large horizontal rotor assemblies mounted in front of each other. Both eliminate the torque by producing an equal amount torque in the opposite direction which stabilises the aircraft. However, a huge disadvantage with twin-rotor machines is the high parasitic drag of the rotor hubs and controls in forward flight. Generally, the parasitic...
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