Démonstrateur Sikorsky X 2

The Army’s 160th Special Operations Aviation Regiment is feeling the need for speed to contend with the sprawl of Afghanistan, the unit’s commander, Col. Clay Hutmacher, told an Assn. of the U.S. Army aviation symposium here in January.
The “Night Stalkers”—so-called because most of their missions are flown in darkness—conduct raids to capture or kill enemy leadership. Flying from Bagram AB often puts their MH-6 Little Bird, MH-60 Black Hawk and MH-47 Chinook troop-carrying helicopters 2 hr. from targets. “We’re looking to go farther and faster and carry more stuff,” Hutmacher said.
The top cruising speed for military helicopters is usually 150-160 kt. One reason is the aerodynamic phenomenon of “retreating blade stall.” The only operational rotorcraft that overcomes it is the V-22 Osprey tiltrotor, flown by the Marines and Air Force Special Operations Command. By tilting its wingtip rotors forward after taking off vertically and flying like an airplane, the Osprey escapes retreating blade stall to cruise at around 250 kt. and fly farther, unrefueled, than helicopters. Hutmacher, though, said the V-22 doesn’t seem to be the answer for the 160th because it can’t hover as well as most helicopters.
“Above 4,000 ft., there’s a significant [hovering] limitation on the V-22,” he said. Tiltrotor engineers concede that while the V-22 hovers well in many situations, the special twist and size of its “proprotors” leave it unable to carry as much useful load pound-for-pound as most helicopters hovering in similar conditions.
“I’m not disparaging the V-22,” Hutmacher said. Hovering ability, however, is critical to the 160th, because “at the end of the day, our mission is going to terminate in a hover.”
Two technologies Hutmacher has seen might provide faster rotorcraft: Piasecki Aircraft Corp.’s X-49A SpeedHawk and Sikorsky Aircraft Corp.’s X2 technology. Both are “compound helicopters,” which have an extra means of forward thrust. Compounds have been tried for decades but none has gone into production, partly because the weight of the additional gear used for extra thrust tended to cut into range and payload. Another problem is the dramatic increase in drag a helicopter’s rotor and rotorhead create as speed increases.
Piasecki and Sikorsky say they’ve solved the retreating blade stall and drag problems. The Army, however, has no plan to develop SpeedHawk or X2 technology, and neither will be ready for years in any event.
The SpeedHawk, a modified Sikorsky SH-60F Sea Hawk with a vectored-thrust, ducted propeller on its tail for forward propulsion, might make it first. Piasecki is developing SpeedHawk on an Army R&D contract. If the military funded a program to put SpeedHawk technology on Black Hawks, “you could transition this technology within five years,” says John Piasecki, president.
The aircraft has a small wing that provides lift so the rotor doesn’t have to provide it all. That delays the onset of retreating blade stall, Piasecki said, and its propeller allows the SpeedHawk to fly forward in level attitude, rather than having to pitch its nose down. Those features, coupled with a rotorhead fairing, he said, significantly reduce high-spe
The Army’s 160th Special Operations Aviation Regiment is feeling the need for speed to contend with the sprawl of Afghanistan, the unit’s commander, Col. Clay Hutmacher, told an Assn. of the U.S. Army aviation symposium here in January.
The “Night Stalkers”—so-called because most of their missions are flown in darkness—conduct raids to capture or kill enemy leadership. Flying from Bagram AB often puts their MH-6 Little Bird, MH-60 Black Hawk and MH-47 Chinook troop-carrying helicopters 2 hr. from targets. “We’re looking to go farther and faster and carry more stuff,” Hutmacher said.
The top cruising speed for military helicopters is usually 150-160 kt. One reason is the aerodynamic phenomenon of “retreating blade stall.” The only operational rotorcraft that overcomes it is the V-22 Osprey tiltrotor, flown by the Marines and Air Force Special Operations Command. By tilting its wingtip rotors forward after taking off vertically and flying like an airplane, the Osprey escapes retreating blade stall to cruise at around 250 kt. and fly farther, unrefueled, than helicopters. Hutmacher, though, said the V-22 doesn’t seem to be the answer for the 160th because it can’t hover as well as most helicopters.
“Above 4,000 ft., there’s a significant [hovering] limitation on the V-22,” he said. Tiltrotor engineers concede that while the V-22 hovers well in many situations, the special twist and size of its “proprotors” leave it unable to carry as much useful load pound-for-pound as most helicopters hovering in similar conditions.
“I’m not disparaging the V-22,” Hutmacher said. Hovering ability, however, is critical to the 160th, because “at the end of the day, our mission is going to terminate in a hover.”
Two technologies Hutmacher has seen might provide faster rotorcraft: Piasecki Aircraft Corp.’s X-49A SpeedHawk and Sikorsky Aircraft Corp.’s X2 technology. Both are “compound helicopters,” which have an extra means of forward thrust. Compounds have been tried for decades but none has gone into production, partly because the weight of the additional gear used for extra thrust tended to cut into range and payload. Another problem is the dramatic increase in drag a helicopter’s rotor and rotorhead create as speed increases.
Piasecki and Sikorsky say they’ve solved the retreating blade stall and drag problems. The Army, however, has no plan to develop SpeedHawk or X2 technology, and neither will be ready for years in any event.
The SpeedHawk, a modified Sikorsky SH-60F Sea Hawk with a vectored-thrust, ducted propeller on its tail for forward propulsion, might make it first. Piasecki is developing SpeedHawk on an Army R&D contract. If the military funded a program to put SpeedHawk technology on Black Hawks, “you could transition this technology within five years,” says John Piasecki, president.
The aircraft has a small wing that provides lift so the rotor doesn’t have to provide it all. That delays the onset of retreating blade stall, Piasecki said, and its propeller allows the SpeedHawk to fly forward in level attitude, rather than having to pitch its nose down. Those features, coupled with a rotorhead fairing, he said, significantly reduce high-speed drag.
The sole SpeedHawk demonstrator has flown 86 hr., reaching 180 kt. indicated airspeed, a limit imposed by the Navy because the aircraft is a modified Sea Hawk. Pending a waiver of that limit, more funding and modifications to the aircraft, Piasecki hopes to soon reach 215 kt. Applying the technology to a new design could produce a helicopter capable of 270 kt. or more, he ventures.
Sikorsky’s X2 technology combines two coaxial rotors with an 80-in.-dia. pusher propeller. The coaxial rotors delay retreating blade stall by rotating in opposite directions, eliminating the need to raise the pitch on a blade as it retreats and meets less lift-assisting relative wind. The advancing blades of each rotor create lift in balance, says Chief X2 Engineer Steve Weiner, making it unnecessary to add pitch to retreating blades. Fairings on both rotor hubs and a sleek body hold drag to acceptable levels, Weiner adds.
The X2 demonstrator, which was built on a specially designed airframe, has flown only 6.2 hr. and no faster than 106 kt., but Sikorsky plans to take it to 250 kt. this summer. Sikorsky is funding the project, says Program Manager Jim Kagdis, and has no restrictions on reaching its goals if the technology performs as expected. Even so, X2 technology won’t be ready for prime time before 2018.
ed drag.
The sole SpeedHawk demonstrator has flown 86 hr., reaching 180 kt. indicated airspeed, a limit imposed by the Navy because the aircraft is a modified Sea Hawk. Pending a waiver of that limit, more funding and modifications to the aircraft, Piasecki hopes to soon reach 215 kt. Applying the technology to a new design could produce a helicopter capable of 270 kt. or more, he ventures.
Sikorsky’s X2 technology combines two coaxial rotors with an 80-in.-dia. pusher propeller. The coaxial rotors delay retreating blade stall by rotating in opposite directions, eliminating the need to raise the pitch on a blade as it retreats and meets less lift-assisting relative wind. The advancing blades of each rotor create lift in balance, says Chief X2 Engineer Steve Weiner, making it unnecessary to add pitch to retreating blades. Fairings on both rotor hubs and a sleek body hold drag to acceptable levels, Weiner adds.
The X2 demonstrator, which was built on a specially designed airframe, has flown only 6.2 hr. and no faster than 106 kt., but Sikorsky plans to take it to 250 kt. this summer. Sikorsky is funding the project, says Program Manager Jim Kagdis, and has no restrictions on reaching its goals if the technology performs as expected. Even so, X2 technology won’t be ready for prime time before 2018.

West Palm Breaking News: Sikorsky X2 hits 181kt

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Sikorsky reported earlier today that the X2 has reached 181kt, a key milestone in the company's plan to test the vehicle out to 250kt, as well as the final flight in the third of four phases of testing. Time to update my table [Vous devez être inscrit et connecté pour voir ce lien]. Do I have to add an entry for the Lynx doing 216.5kt in August 1986, as written in the [Vous devez être inscrit et connecté pour voir ce lien] today?

Tableau des Héllicoptères comparables

X2	Coaxial twin pusher	No	181kt (as of 25 May 2010)	Sikorsky
Westland Lynx	Single rotor	Yes	174kt	Wikipedia
Piasecki Pathfinder II	Single rotor ringtail with wing	No	195kt	Aviastar.org
Boeing 360	Tandem twin	No	200kt	Wikipedia
Bo-46	Single rotor with auxiliary turbojets

Has Sikorsky's X2 seen its highest speed?

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[Vous devez être inscrit et connecté pour voir ce lien] written by Thomas Lawrence (the technical fellow) and David Jenney reports that engineers had planned to reach the 250kt (463km/h)speed goal during a flight in August, but the LHTEC 800-powered pusher quit accelerating at 235kt (435km/h). In July, [Vous devez être inscrit et connecté pour voir ce lien]

..Most recently, we set our sights on 463 km/h.
On the day of that flight, in August of this year, the test team got started at the crack of dawn. To ensure that the pilots would be flying in smooth air, the crew had to be on site by 5:00 a.m., before the sun had a chance to heat the air enough for the wind to pick up. The crew rolled the aircraft out onto the runway, where a dozen safety officers in bright orange jumpsuits and noise-canceling headsets were on patrol. Two chase vehicles were there to observe the test flight--another helicopter and a fixed-wing turboprop. The latter would be needed to keep up with the X2 as it accelerated to higher speeds. The test team was on high alert as it orchestrated flight activities to keep the three vehicles a safe distance apart.
With everyone's nerves on edge, the X2 started up its engine at 6:30 a.m., and the helicopter took off. Within a few minutes the X2 had reached a speed of 350 km/h. A dozen people watched from the ground as the airspeed crept up, first to 400, then 410, and finally topping out at 435 km/h--not quite the goal we'd set, but good enough for this round. Cheers and applause broke out on the ground. The pilot slowed the X2, turned it around, and flew back to land on the runway....

Even so, Sikorsky broke the long standing official speed record for a helicopter set by Westland Lynx in 1984 at 216kt (400km/h). The company's own XH-59A coaxial demonstrator in the early 1970s however recorded an unofficial speed of 263kt (487km/h), though technology at the time couldn't handle the types of vibrations required to go that fast.
The company has said it will continue pushing the X2 until the end of September, with simulations putting the ultimate top speed between 251kt and 264kt, just a tad faster than the XH-59A.

Sikorsky X2 helicopter reaches 250 knots

Sikorsky Aircraft's X2 Technology demonstrator reached its ultimate target speed of 250 knots in level flight Wednesday at the company's Development Flight Center in West Palm Beach, Fla.
The speed, reached during a 1.1-hour flight, is an unofficial speed record for a helicopter. In July, the X2 [Vous devez être inscrit et connecté pour voir ce lien] a top speed of 225 knots, topping the the previous record of 216 knots for a 3,500 kg class of rotorcraft, which a Westland Lynx set in the 1980s.
The demonstrator also reached 260 knots in a very shallow dive during Wednesday's flight, Sikorsky reported.
"The aerospace industry today has a new horizon," Sikorsky President Jeffrey Pino said in a news release. "The X2 Technology demonstrator continues to prove its potential as a game-changer, and Sikorsky Aircraft is proud to be advancing this innovative technology and to continue our company's pioneering legacy."
The demonstrator is designed to show that a helicopter can cruise comfortably at 250 knots while retaining such desirable attributes as excellent low-speed handling, efficient hovering, and a seamless and simple transition to high speed.

Sikorsky expects 265kt from X2

[Vous devez être inscrit et connecté pour voir ce lien] engineers say the company's self-funded X2 advanced technology helicopter could reach 265kt (490km/h) or more in the next few months after a central sail fairing is installed on the rotor mast.
The twin coaxial contra-rotating rotor demonstrator reached its project goal speed of 250kt in level flight during a morning test flight on 15 September in West Palm Beach, Florida.
At that speed, test pilot Kevin Bredenbeck says the T800-powered pusher had a reserve of around 300hp (225kW), although test limits held the speed to 250kt, a programme target speed achieved about midway through the 1.1h flight. Total power required to maintain 250kt was 1,300hp, 80% of the T800's capability.
In slightly over two years of testing, the X2 has flown for 16.2h on 17 flights, far exceeding the maximum level cruise speed for a helicopter to date - officially 217kt by a [Vous devez être inscrit et connecté pour voir ce lien], and unofficially 236kt by the company's XH-59A demonstrator in the early 1970s.
Sikorsky is investigating whether to attempt an official speed record during the final flight-testing on the vehicle, which is likely to involve two flights for acoustic testing and two flights for sail fairing and higher speed testing.
Steve Weiner, chief engineer for the X2 programme, says the stationary sail fairing, sandwiched between the two main rotors, could add 15kt to the cruise speed, once engineers perfect the installation.
Ground tests of the fairing are to start in the next few weeks.
Weiner says Sikorsky is investigating whether to attempt an official speed record during the remaining testing on the vehicle, which is likely to involve two flights for acoustic testing and two flights for sail fairing and higher speed testing.

Sikorsky X2 speed king - Facts, figures and sail fairings...

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Here are some additional facts and figures that Sikorsky has provided regarding its [Vous devez être inscrit et connecté pour voir ce lien] of the X2 technology demonstrator in Florida.

• To date, Sikorsky has flown the twin contra-rotating main rotor pusher for 17 flights and 16.2 flight hours.
  
• Sikorsky expects to fly four more flights before the vehicle is retired, after which it will likely travel to a variety of airshows as a static display item. Two of of the four remaining flights will be for noise measurements; the other two for speed.
  
• Test pilot Kevin Bredenbeck reached the 250kt target speed for the program about halfway through the 1.1h flight at 5,500ft altitude. Aircraft weight was approximately 6,500lb
  
• Bredenbeck says there was approximately 300hp of power reserve in T800 engine at 250kt
  
• The main rotor was slowed by 5% compared to hover speed for the high speed cruise testing
  
• Bredenbeck says vibation levels with the active vibration cancellation system on were "consistent with Blackhawk at 140kt cruise speed". He says the vibration levels plateua at about 200kt and remain the same thereafter
  
• Bredenbeck accelerated to 260kt by putting the X2 in a shallow dive of "1-2 degrees" nose down
  
• Control feel: Bredenbeck says it flies like a fixed wing aircraft "as soon as you utilize the prop and go into X2 modes". Sikorsky exercised the X2 through 30 deg of bank and up to 1.5G, though pilots have flown some "higher aggressive profiles" in simulator, says Bredenbeck, adding, "Yet to be discovered is the potential of this aircraft"
  
• Test flights have provided a "test verified" digital model of the X2 which is being used for future designs
  
• Fuel burn - Sikorsky says that the X2 at 210-220kt speed has the samne fuel flow as a conventional helo at 120-130kt due to its improved lift-to-drag ratio
  
• Sikorsky is currently installing a "sail fairing" between the two main rotors for the upcoming two high speed flights, which could see cruise speeds beyond 265kt. The picture below shows how the stationary fairing is mounted
  

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