Sikorsky X2
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Sikorsky X2
Sikorsky X2 World Record Speed Demonstrator RSideFront MacDill AirFest 5Oct2011 (14513000689).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
US$50 million[2]
Sikorsky S-97 Raider

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

Design and development

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 supplied using two jet engines, but that vibration and fuel consumption was excessive;[3][4][5] 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.[6][7]

Other features include slowed[8] "de-swirling"[9]rigid rotors two feet apart, active force counter-vibration inspired by the Black Hawk,[10] and using most of the power in forward flight for the pusher propeller rather than the rotor.[3] Unusually for helicopters, the power required for high speed is more than the hover power. The pilot controls the independent propeller power with a thumb wheel on the collective.[11]

Test flights and flight simulations were combined to improve test procedure.[12][13] 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.[14] The rotor hub can have 10-20 times the drag of the blade.[15] Sikorsky intended to test hub fairings to reduce drag by 40%,[16] and test flew fairings on the hubs themselves but not the central hub fairing ("aero sail") in between the hubs.[17] Sikorsky has since patented a "Standpipe" (fixed tube between rotating rotor axes) suitable for a central hub fairing.[18]

On 4 May 2009, Sikorsky unveiled a mockup of a Light Tactical Helicopter derivative of the X2,[19] and unveiled a prototype in October 2014.[20][21][22]

In June 2014, Sikorsky/Boeing submitted the SB-1 Defiant helicopter design for the Future Vertical Lift program based on the X2 principle,[23][24] which was approved by the Army in October.[25]

Operational history

The X2 first flew on 27 August 2008 from Schweizer Aircraft, a division of Sikorsky Aircraft Corporation's facility at Horseheads, New York. The flight lasted 30 minutes.[1] This began a four-phase flight test program, to culminate with reaching a planned 250-knot top speed.[26] The X2 completed flights with its propeller fully engaged in July 2009.[27] Sikorsky completed phase three of the testing with the X2 reaching 181 knots in test flight in late May 2010.[28]

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.[29][30]

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,[31][32] an unofficial speed record for a helicopter.[3][33] The demonstrator then reached a new record speed of 260 knots (300 mph; 480 km/h) in a shallow 2? to 3? dive,[34] which was just short of the 303 mph achieved by the Sikorsky S-69 technology demonstrator helicopter.[35] 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[36][37] to keep tip speed below Mach 0.9, the rotor disc is slightly nose-up, and the lift-to-drag ratio is about twice that of a conventional helicopter. Hands-off flying was also successfully performed during flight tests.[38]

On 14 July 2011, the X2 completed its final flight and was officially retired after accumulating 22 hours over 23 test flights.[39][40] With the end of development, the X2 will be followed by its first application, the S-97 Raider high-speed scout and attack helicopter.[41] It was donated to the National Air and Space Museum in October 2016 and is on display in the Steven F. Udvar-Hazy Center in Chantilly, Virginia.[42][43]


The Sikorsky Aircraft Corporation and the X2 Technology Demonstrator Team was awarded the 2010 Robert J. Collier Trophy by the National Aeronautic Association[44][45] "...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).[46]


Data from Flug-Revue[14]NOTE: No other specifications have been released by Sikorsky.

General characteristics

  • Crew: Two
  • Aspect ratio: 9.5
  • Empty weight: 5,300 lb (2,404 kg) [42]
  • Gross weight: 6,000 lb (2,722 kg) [47][48][49]
  • Max takeoff weight: 5,300 lb (2,404 kg) [37][50]-6,000 lb (2,700 kg)[]
  • Powerplant: 1 × LHTEC T800-LHT-801 turboshaft, 1,800 shp (1,300 kW)
  • Main rotor diameter: 2× 26 ft 5 in (8.05 m)
  • Main rotor area: 548 sq ft (50.9 m2) contra-rotating four-bladed coaxial.[37][51]
  • Propellers: 6-bladed pusher


  • Maximum speed: 290 mph (460 km/h, 250 kn) [52]
  • Range: 35 mi (56 km, 30 nmi)
  • Wing loading: 0.44 lb/sq ft (2.1 kg/m2)
  • Power/mass: 3.66 hp/lb[37]

See also

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. ^ Warwick, Graham (22 May 2015). "Sikorsky Conducts First Flight Of S-97 Helo". Aviation Week & Space Technology. Retrieved 2015.
  3. ^ a b c Goodier, Rob (September 20, 2010). "Inside Sikorsky's Speed-Record-Breaking Helicopter Technology". Popular Mechanics. Retrieved 2010.
  4. ^ Thomas Lawrence and David Jenney (31 Aug 2010). "The Fastest Helicopter on Earth". IEEE Spectrum. Archived from the original on 30 January 2017. Retrieved 2017. the helicopter vibrated so much at these higher speeds that its pilots struggled to control it .. The heavy and fuel-hungry jets pushed the aircraft to high speedCS1 maint: uses authors parameter (link)
  5. ^ XH-59A / X2 comparison IEEE
  6. ^ Sikorsky to Build and Test X2 Technology Demonstrator Helicopter Archived July 14, 2008, at the Wayback Machine. Sikorsky
  7. ^ Trimble, Stephen (26 July 2010). "Sikorsky X2 sets unofficial helicopter speed record". FlightGlobal. Reed Business Information. Retrieved 2010.
  8. ^ First Flight Of Sikorsky X2 Demonstrator, Archived March 7, 2012, at the Wayback Machine Aviation Week & Space Technology, 27 August 2008. Accessed: 9 March 2012. Archived on 7 March 2012.
  9. ^ Chandler, Jay. "Advanced rotor designs break conventional helicopter speed restrictions (page 1) Archived July 18, 2013, at the Wayback Machine" Page 2 Archived July 18, 2013, at the Wayback Machine Page 3 Archived 2013-07-18 at the Wayback Machine. ProPilotMag, September 2012. Accessed: 10 May 2014. Archive 1 Archive 2
  10. ^ X2 marks the spot for radical rotor designs,, 12 June 2007.
  11. ^ Fell, William (April-May 2018). "X2 From the Pilot's View". Archived from the original on 8 May 2019.CS1 maint: date format (link)
  12. ^ Wilson, J.R. "Defense Interview: Mark Miller" Defense Media Network, 9 September 2011. Accessed: 4 October 2014. Archived on 2 November 2012.
  13. ^ "Sikorsky Innovations Introduces X2 Technology(TM) Light Tactical Helicopter Simulator" Sikorsky PR
  14. ^ a b "Sikorsky X2". Flug-Revue. Archived from the original on June 12, 2008. Retrieved .
  15. ^ Harris, Franklin D. "Rotor Performance at High Advance Ratio: Theory versus Test Archived 2013-02-18 at the Wayback Machine" page 119 NASA/CR--2008-215370, October 2008. Accessed: 13 April 2014.
  16. ^ Croft, John (20 May 2010). "Sikorsky X2 breaks helicopter speed barrier". Flightglobal. Reed Business Information. Archived from the original on 28 May 2015. Retrieved 2015.
  17. ^ Dubois, Thierry (26 July 2011). "AgustaWestland". Aviation International News. Archived from the original on 11 October 2014. Retrieved 2015.
  18. ^ US 20150125299  "Counter-rotating Rotor System With Stationary Standpipe" PDF
  19. ^ Trimble, Stephen. Sikorsky unveils mock-up X2 armed scout., 4 May 2009.
  20. ^ S-97 Rollout video Sikorsky
  21. ^ Parsons, Dan (2 October 2014), "Sikorsky rolls-out high-speed Raider rotorcraft", Flightglobal, Reed Business Information, retrieved 2014
  22. ^ Warwick, Graham. "Sikorsky Talks To Customers About Potential Raider Applications" Aviation Week & Space Technology, 6 October 2014. Accessed: 3 October 2014. Photos Archived on 3 October 2014
  23. ^ Majumdar, Dave. "Sikorsky and Boeing Team Submit New Army Helicopter Design" -, 17 June 2014. Accessed: 19 June 2014. Archive
  24. ^ Sikorsky and Boeing to pitch 'X-2'-based design for US Army JMR TD effort -, February 28, 2013
  25. ^ U.S. Army Selects Bell and Sikorsky/Boeing to Build Prototypes for Next Generation Helicopter Program -, 3 October 2014
  26. ^ Trimble, Stephen. "Sikorsky high-speed X2 prototype starts flight-test phase". Flight International, 2 September 2008.
  27. ^ Lynch, Kerry. "Sikorsky X2 Flies With Engaged Propeller" Aviation Week, 13 July 2009. Paywall
  28. ^ Croft, John. "Sikorsky completes third-phase X2 tests with 181kt flight". Flight International, 27 May 2010.
  29. ^ "Rotorcraft Absolute: Speed over a straight 15/25 km course Archived 2013-12-03 at the Wayback Machine". Fédération Aéronautique Internationale (FAI). Note search under E-1 Helicopters and "Speed over a straight 15/25 km course". Accessed: 26 April 2014.
  30. ^ "X2 Technology Demonstrator Achieves 225 Knots, Sets New Top Speed for Helicopter - Target Milestone of 250 Knots Looms in Q3 2010"., 15 June 2015.
  31. ^ Croft, John (September 15, 2010). "Sikorsky X2 hits 250kt goal". Flight International. Retrieved .
  32. ^ Sikorsky's X2 Chases World Speed Record
  33. ^ "Sikorsky X2 Technology Demonstrator Achieves 250-Knot Speed Milestone". 15 September 2010. Retrieved 2010.
  34. ^ Finnegan, Joy editor-in-chief (1 October 2010). "Sikorsky Breaks 250 KTAS Record". Rotor & Wing. Retrieved 2010.
  35. ^ Robb, Raymond L. Hybrid Helicopters: Compounding the Quest for Speed[permanent dead link] p49, Vertiflite, Summer 2006. Quote: "Ultimately, the XH-59A achieved an incredible 303 mph"
  36. ^ 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.
  37. ^ a b c d Jackson, Dave. "Coaxial - Sikorsky ~ X2 TD" Unicopter, 18 September 2010. Accessed: April 2014. Archived on 13 September 2013.
  38. ^ D. Walsh, S. Weiner, K. Arifian, T. Lawrence, M. Wilson, T. Millott and R. Blackwell. "High Airspeed Testing of the Sikorsky X2 Technology Demonstrator[permanent dead link]" Sikorsky, May 4, 2011. Accessed: October 5, 2013.
  39. ^ Paur, Jason (15 July 2010). "Sikorsky's Record-Setting Helicopter Retires". WIRED. Retrieved 2011.
  40. ^ "Sikorsky X2 rotorcraft prototype makes final flight after proving technology for S-97 scout/attack helicopter". 17 July 2011.
  41. ^ "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.
  42. ^ a b Connor, Roger (25 October 2016). "Sikorsky X2 Helicopter Reaching New Speeds". National Air and Space Museum. Archived from the original on 16 May 2020. Retrieved 2016. Weight, empty: 2,404 kg (5,300 lb)
  43. ^ "Sikorsky X2 joins Smithsonian collection". Helicopter Association International. Helicopter Association International. 28 October 2016. Retrieved 2016.
  44. ^ Warwick, Graham. "Sikorsky's X2 - Collier Win, Commercial Next?" Aviation Week, Mar 16, 2011. Accessed: March 8, 2014. Archive Archived March 9, 2014, at the Wayback Machine
  45. ^ Larson, George. "Sikorsky's X2 and the Collier Trophy Archived 2014-03-09 at the Wayback Machine" Aviation Week, Mar 23, 2011. Accessed: March 8, 2014.
  46. ^ "Howard Hughes Award", American Helicopter Society
  47. ^ Johnson, Wayne (January 18-20, 2012). "Design and Performance of Lift-Offset Rotorcraft for Short-Haul Missions" (PDF). NASA. p. 4. nominal gross weight of 5950 lb.CS1 maint: date format (link)
  48. ^ Drew, James (2016-02-19). "ANALYSIS: Sikorsky seeks next leap in rotorcraft technology". Flight Global. Archived from the original on 30 August 2020. We started with [the] X2 technology demonstrator at about 6,000lbs (2.7t) gross weight.
  49. ^ Walsh, D (January 2011). "High airspeed testing of the Sikorsky X2 Technology(TM) demonstrator".
  50. ^ Tomkins, Richard. "Sikorsky powers on S-97 avionics" United Press International, 17 June 2014. Accessed: 19 June 2014. Archived on 18 June 2014.
  51. ^ Note: this is the disc area of one rotor set, not the effective area of the whole coaxial rotors set.
  52. ^

External links

External video
Official Sikorsky X2 videos
video iconSikorsky X2 technology on YouTube, mitigating dissymmetry of lift and air compressibility near rotor blade tip
video iconSikorsky X2 record flight on YouTube in 2010
video iconSikorsky X2 Collier Trophy on YouTube, pilot and staff commentary

  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.



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