The United States is currently experimenting with a type of aircraft that until now was almost exclusive to the Russian armed forces, a coaxial twin-rotor helicopter, which promises to improve the performance of current aircraft with more speed and more cargo capacity.
Manufactured by the North American Sikorsky, the S-97 Raider this helicopter will be capable of reaching 440 km/h, compared to the little more than 300 that are common in these aircraft.
To understand the difference between this and normal helicopters, just look above and behind, because in a conventional device there are two propellers: one on the helicopter, which is used to lift it up and move forward, and another smaller one on the tail.
The latter is designed to counteract the twisting of the former, and keep the device pointing straight. Without it, the fuselage would spin uncontrollably in the opposite direction of the main rotor.
In contrast, with coaxial rotor helicopters, the tail propeller is unnecessary. With two sets of blades, one located above the other but rotating in the opposite direction -in the style of many commercial radio-controlled helicopters- the aircraft’s fuselage remains level and the load capacity is also increased.
The problem is that helicopters with twin coaxial rotors tend to be slower, and that’s where the rear propeller comes into play, located at the end of the fuselage, and which works like a normal turbine: it is responsible for providing the horizontal thrust, while the two upper propellers are responsible for keeping the helicopter flying.
A second prototype of the S-97 is scheduled to fly later this year, with the intention of blocking competition from manufacturers such as Bell and Lockheed Martin.
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