The fastest helicopter ever built is the Sikorsky X2, which reached a top speed of 250 knots (463 km/h) during a test flight in 2010.
The Sikorsky X2 is a technology demonstration helicopter built by Sikorsky Aircraft. It is the fastest helicopter ever built, reaching a top speed of 250 knots (463 km/h) during a test flight in 2010. This exceeded the previous speed record for helicopters of 216 knots (400 km/h) set in 1986 by the Westland Lynx.
The X2 is a compound helicopter, which means it uses a combination of traditional rotor lift and an additional propulsion system, in this case a pusher propeller, to achieve high speeds. The X2 also features a rigid coaxial rotor system which eliminates the need for a tail rotor, reducing drag and allowing for greater speed.
The X2 technology was developed to demonstrate the potential for a next-generation aircraft, and it was intended to pave the way for a new class of aircraft that would be able to perform missions that are currently not possible for traditional helicopters, such as high-speed cruise and high-speed, low-altitude pursuit.