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The S-97 Raider is a helicopter currently under development by the pioneering Sikorsky aircraft corporation. The raider is the latest in a line of coaxial rotor helicopters such as the Sikorsky X-2 and S-69. In fact, the S-97 was developed from the X-2 technology demonstrator. The S-97 continues efforts to turn the advancing blade concept into a practical and successful design. This design meant to overcome the airspeed limitations of traditional helicopters. By using two rigid coaxial rotors and a pusher-type clutch propeller on the tail. Since the main rotors counter-rotate and therefore cancel out any torque effects, an anti-toque tail rotor is unnecessary. The tail rotor on the S-97 has the sole purpose of making it go faster. The clever part is that the two rigid rotors provide two advancing blades, one for each side of the aircraft. In theory this compensated for retreating blade stall, the main limiting factor to helicopter top speeds. The main rotors can concentrate on providing consistent lift, while propulsion is provided from the tail. The end result is an aircraft that is comparable with a fixed-wing aircraft in forward flight, but does not lose the vertical takeoff, hovering or agility of a traditional helicopter. When this design has been tried before there have been serious problems with vibration, however advances in material science and avionics have largely mitigated those issues. In the case of the S-97 these come in the form of fly-by-wire control and anti-vibration actuators that eliminate shudders and shaking. In theory this allows the S-97 to dash at 276 Mph (444 Kph) and cruise at a maximum of 253Mph (407Kph). These speeds are perfect for the Raider’s intended role as a fast, armed scout helicopter or light tactical helicopter. The power to reach these speeds comes from a single GE YT706 turboshaft engine used in the prototype. However, a more powerful and currently unnamed engine will be at the heart of the production model. Two pilots crew the Raider, seated side-by-side. Tactical options will include Hellfire missiles, 2.75 in. unguided rockets, one .50 caliber and another 7.62mm gun. The Raider can carry additional fuel and ammunition for extended missions in enemy airspace. The Raider made its maiden flight on May 22 2015 without incident. It represents a serious push by Sikorsky to convince the U.S. Army of the technology’s future role as a light tactical aircraft for the 21st century.
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