Sikorsky X2

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Sikorsky X2 in flight.jpg
Sikorsky X2 Demonstrator
Role Experimental compound helicopter
Manufacturer Sikorsky Aircraft / Schweizer Aircraft
First flight 27 August 2008[1]
Retired 14 July 2011
Status Retired
Number built 1
Developed into Sikorsky S-97 Raider

The Sikorsky X2 is an experimental high-speed compound helicopter with coaxial rotors developed by Sikorsky Aircraft.

Design and development[edit]

Sikorsky developed the X2 helicopter on a $50 million budget. The design includes expertise gathered from several earlier design projects. The S-69/XH-59A Advancing Blade Concept Demonstrator had shown that high speed was possible with a coaxial helicopter with auxiliary propulsion, but that vibration was excessive;[2] the Cypher UAV expanded the company's knowledge of the unique aspects of coaxial flight control laws with a fly by wire aircraft; and the RAH-66 Comanche developed expertise in composite rotors and advanced transmission design.[3][4] Other features include slowed[5] "de-swirling"[6] rigid rotors 2 feet apart, active force counter-vibration inspired by the Black Hawk,[7] and using most of the power in forward flight 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 technology from Moog Inc, and propeller by Aero Composites.[8]

On 4 May 2009, Sikorsky unveiled a mock-up of a Light Tactical Helicopter derivative of the X2.[9]

In June 2014, Sikorsky/Boeing submitted a helicopter design for the Future Vertical Lift program based on the X2 principle.[10][11]

Operational history[edit]

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.[12] The X2 completed flights with its propeller fully engaged in July 2009.[13] Sikorsky completed phase 3 of the testing with the X2 hitting 181 knots in test flight in late May 2010.[14]

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.[15] The X2 flight was purposefully made 37 years to the date of the S-69's first flight.[16]

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,[17][18] an unofficial speed record for a helicopter[2][19] until surpassed by the Eurocopter X3 in 2013.[20] The demonstrator also reached a speed of 260 knots (300 mph; 480 km/h) in a shallow 2˚ to 3˚ dive,[21] slightly less than the 303 mph of the XH-59A.[22] 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 from 446 to 360 RPM[23][24] 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.[25]

On 14 July 2011, the X2 completed its final flight and was officially retired after accumulating 22 hours over 23 test flights.[26] With the end of development, the X2 will be followed by its first application, the S-97 Raider high-speed scout and attack helicopter.[27]


The Sikorsky Aircraft Corporation and the X2 Technology Demonstrator Team was awarded the 2010 Robert J. Collier Trophy by the National Aeronautic Association[28][29] "...For demonstrating a revolutionary 250 knot helicopter, which marks a proven departure point for the future development of helicopters by greatly increasing their speed, maneuverability and utility." For 2011, the X2 team received the Howard Hughes Award (American Helicopter Society).[30]


Data from Flug-Revue[8] NOTE: No other specifications have been released by Sikorsky.

General characteristics

  • Crew: 2
  • Length: not available ()
  • Rotor diameter: 26.4 ft[24] (8.05 m)
  • Height: not available ()
  • Disc area: 548 ft²[24][31] (50.9 m²)
  • Empty weight: lb (kg)
  • Max. takeoff weight: 5,300[24] - 6,000 lb[32] (or 3,600 kg[8])
  • Powerplant: 1 × LHTEC T800-LHT-801 turboshaft, 1300–1800 shp (1000–1340 kW)
  • Propellers: 1 six-bladed pusher-type propeller
  • Rotor configuration: 2 four-bladed co-axial


See also[edit]

Related development
Aircraft of comparable role, configuration and era
Related lists


  1. ^ a b Trimble, Stephen. "Sikorsky's X2 speedster completes first flight"., 27 August 2008.
  2. ^ a b c Goodier, Rob (September 20, 2010). "Inside Sikorsky's Speed-Record-Breaking Helicopter Technology". Popular Mechanics. Retrieved 22 September 2010. 
  3. ^ Sikorsky to Build and Test X2 Technology Demonstrator Helicopter. Sikorsky
  4. ^ Trimble, Stephen (26 July 2010). "Sikorsky X2 sets unofficial helicopter speed record". FlightGlobal. Reed Business Information. Retrieved 29 July 2010. 
  5. ^ First Flight Of Sikorsky X2 Demonstrator,[dead link] Aviation Week & Space Technology, 27 August 2008. Accessed: 9 March 2012.
  6. ^ Chandler, Jay. "Advanced rotor designs break conventional helicopter speed restrictions (page 1)" Page 2 Page 3. ProPilotMag, September 2012. Accessed: 10 May 2014. Archive 1 Archive 2 Archive 3
  7. ^ X2 marks the spot for radical rotor designs,, 12 June 2007.
  8. ^ a b c "Sikorsky X2". Flug-Revue. Archived from the original on June 12, 2008. Retrieved 2007-06-25. 
  9. ^ Trimble, Stephen. Sikorsky unveils mock-up X2 armed scout., 4 May 2009.
  10. ^ Majumdar, Dave. "Sikorsky and Boeing Team Submit New Army Helicopter Design" -, 17 June 2014. Accessed: 19 June 2014. Archive
  11. ^ Sikorsky and Boeing to pitch ‘X-2’-based design for US Army JMR TD effort -, February 28, 2013
  12. ^ Trimble, Stephen. "Sikorsky high-speed X2 prototype starts flight-test phase". Flight International, 2 September 2008.
  13. ^ Lynch, Kerry. "Sikorsky X2 Flies With Engaged Propeller"[dead link] Aviation Week, 13 July 2009. Paywall
  14. ^ Croft, John. "Sikorsky completes third-phase X2 tests with 181kt flight". Flight International, 27 May 2010.
  15. ^ "Rotorcraft Absolute: Speed over a straight 15/25 km course". Fédération Aéronautique Internationale (FAI). Note search under E-1 Helicopters and "Speed over a straight 15/25 km course". Accessed: 26 April 2014.
  16. ^ "X2 Technology Demonstrator Achieves 225 Knots, Sets New Top Speed for Helicopter - Target Milestone of 250 Knots Looms in Q3 2010"., 26 July 2010.
  17. ^ Croft, John (September 15, 2010). "Sikorsky X2 hits 250kt goal". Flight International. Retrieved 2010-09-16. 
  18. ^ Sikorsky's X2 Chases World Speed Record
  19. ^ "Sikorsky X2 Technology Demonstrator Achieves 250-Knot Speed Milestone". 15 September 2010. Retrieved 23 September 2010. "The speed, reached during a 1.1-hour flight, is an unofficial speed record for a helicopter." 
  20. ^ Paur, Jason. "X3 Helicopter Sets Speed Record At Nearly 300 MPH" Wired (magazine), 11 June 2013. Accessed: 17 June 2014. Archived on 31 March 2014
  21. ^ Finnegan, Joy editor-in-chief (1 October 2010). "Sikorsky Breaks 250 KTAS Record". Rotor & Wing. Retrieved 6 October 2010. 
  22. ^ Robb, Raymond L. Hybrid Helicopters: Compounding the Quest for Speed p49, Vertiflite, Summer 2006. Quote: "Ultimately, the XH-59A achieved an incredible 303 mph"
  23. ^ Datta, Anubhav et al. Experimental Investigation and Fundamental Understanding of a Slowed UH-60A Rotor at High Advance Ratios, page 2. NASA, 2011. Accessed: April 2014.
  24. ^ a b c d e f Jackson, Dave. "Coaxial - Sikorsky ~ X2 TD" Unicopter, 18 September 2010. Accessed: April 2014. Archived on 13 September 2013.
  25. ^ D. Walsh, S. Weiner, K. Arifian, T. Lawrence, M. Wilson, T. Millott and R. Blackwell. "High Airspeed Testing of the Sikorsky X2 Technology Demonstrator" Sikorsky, May 4, 2011. Accessed: October 5, 2013.
  26. ^ Paur, Jason (15 July 2010). "Sikorsky’s Record-Setting Helicopter Retires". WIRED. Retrieved 15 July 2011. 
  27. ^ "Award-Winning X2 Technology Demonstrator Takes its Final Flight - Program paved the way for upcoming S-97 Raider helicopter", Sikorsky Aircraft Corp., 14 July 2011.
  28. ^ Warwick, Graham. "Sikorsky's X2 - Collier Win, Commercial Next?"[dead link] Aviation Week, Mar 16, 2011. Accessed: March 8, 2014. Archive
  29. ^ Larson, George. "Sikorsky's X2 and the Collier Trophy"[dead link] Aviation Week, Mar 23, 2011. Accessed: March 8, 2014. Archive
  30. ^ "Howard Hughes Award", American Helicopter Society
  31. ^ Note: this is the disc area of one rotor set, not the effective area of the whole coaxial rotors set.
  32. ^ Tomkins, Richard. "Sikorsky powers on S-97 avionics" United Press International, 17 June 2014. Accessed: 19 June 2014. Archived on 18 June 2014.
  33. ^
  34. ^ a b Green, Ronald D. Flight Plan 2011 - Analysis of the U.S. Aerospace Industry, Rotorcraft Developments p18, U.S. Department of Commerce / International Trade Administration, March 2011. Accessed: 2 March 2012. Quote: "Several companies--including Sikorsky, Eurocopter, and Carter Aerospace Technologies--are developing compound helicopters to combine vertical/short take-off-and-landing capabilities with one or more propellers for increasing forward speed over conventional helicopter design."

External links[edit]