Download video: WORLDS FASTEST HELICOPTER Sikorsky X2 unveiled in US

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A helicopter is a type of rotorcraft in which lift and thrust are supplied by rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward, and laterally. These attributes allow helicopters to be used in congested or isolated areas where fixed-wing aircraft would usually not be able to take off or land. The capability to hover efficiently for extended periods of time allows a helicopter to accomplish tasks that fixed-wing aircraft and other forms of vertical takeoff and landing aircraft cannot perform.

The word helicopter is adapted from the French language hélicoptère, coined by Gustave Ponton d'Amécourt in 1861, which originates from the Greek helix/helik- (ἕλιξ) "twisted, curved"[1] and pteron (πτερόν) "wing".[2][3][4] English-language nicknames for helicopter include "chopper", "helo", "heli" and "whirlybird".
Helicopters were developed and built during the first half-century of flight, with the Focke-Wulf Fw 61 being the first operational helicopter in 1936. Some helicopters reached limited production, but it was not until 1942 that a helicopter designed by Igor Sikorsky reached full-scale production,[5] with 131 aircraft built.[6] Though most earlier designs used more than one main rotor, Due to the operating characteristics of the helicopter—its ability to takeoff and land vertically, and to hover for extended periods of time, as well as the aircraft's handling properties under low airspeed conditions—it has been chosen to conduct tasks that were previously not possible with other aircraft, or were time- or work-intensive to accomplish on the ground. Today, helicopter uses include transportation of people and cargo, military uses, construction, firefighting, search and rescue, tourism, medical transport, and aerial observation, among others.

The Sikorsky X2 is an experimental high-speed compound helicopter with coaxial rotors developed by the American aircraft manufacturer Sikorsky Aircraft.
Sikorsky has incorporated decades of company research and development into the X2 helicopter on a $50 million budget. The S-69/XH-59A Advancing Blade Concept Demonstrator showed high speed was possible with a coaxial helicopter and auxiliary propulsion but it vibrated too much;[2] the Cypher UAV expanded company knowledge of the unique aspects of flight control laws in a fly by wire aircraft with coaxial rotors; and the RAH-66 Comanche, which developed expertise in composite rotors and advanced transmission design.[3][4] Other features include slowed[5] rigid rotors 2 feet apart, active force counter-vibration inspired by the Black Hawk,[6] and using most of the power for the pusher propeller rather than the rotor.[2] The fly-by-wire system is provided by Honeywell, the rotor by Eagle Aviation Technologies, anti-vibration by Moog Inc, and propeller by Aero Composites.[7]

On 4 May 2009, Sikorsky unveiled a mock-up of a Light Tactical Helicopter derivative of the X2.[8]

Sikorsky plans to submit a helicopter for the Future Vertical Lift program based on the X2 design.[9]
The X2 first flew on 27 August 2008 from Schweizer Aircraft's (a division of Sikorsky Aircraft Corporation) facility at Horseheads, New York. The flight lasted 30 minutes.[1] This began a 4-phase flight test program, to culminate with reaching a planned 250-knot top speed.[10] The X2 completed flights with its propeller fully engaged in July 2009.[11] Sikorsky completed phase 3 of the testing with the X2 hitting 181 knots in test flight in late May 2010.[12]

On 26 July 2010, Sikorsky announced that the X2 exceeded 225 knots (259 mph; 417 km/h) during flight testing in West Palm Beach Florida, unofficially surpassing the current FAI rotorcraft world speed record of 216 knots (249 mph; 400 km/h) set by a modified Westland Lynx in 1986.[13] The X2 flight was purposefully made 37 years to the date of the S-69's first flight.[14]

On 15 September 2010, test pilot Kevin Bredenbeck achieved Sikorsky's design goal for the X2 when he flew it at a speed of 250 knots (290 mph; 460 km/h) in level flight,[15][16] an unofficial speed record for a helicopter.[2][17] The demonstrator also reached a speed of 260 knots (300 mph; 480 km/h) in a shallow 2˚ to 3˚ dive,[18] slightly less than the 303 mph of the XH-59A.[19] Sikorsky states that the X2 has the same noise level at 200 knots that a regular helicopter has at 100 knots. Above 200 knots, the rotor speed is reduced to keep tip speed below Mach 0.9, the rotor disc is slightly nose-up, and Lift-to-drag ratio is about twice that of a conventional helicopter. Hands-off flying was sometimes performed.[20]

On 14 July 2011, the X2 completed its final flight and was officially retired after accumulating 22 hours over 23 test flights.[21] With the end of development, the X2 will be followed by its first application, the S-97 Raider high-speed scout and attack helicopter.[22]