With its X2 design, Sikorsky is betting that a helicopter can fly faster with coaxial main rotors and an unusual "propulsor" tail rotor.
(Credit: Sikorsky Aircraft)How fast can a helicopter go? If Sikorsky Aircraft's plans work out, the answer could be: a lot faster than is possible right now.
For several years, Sikorsky has been working on what it calls X2 technology, a suite of systems that it says could let a helicopter "cruise comfortably" at 250 knots. That would be a far zippier pace than most current rotary wing aircraft can handle. The UH-60L variant of Sikorsky's Blackhawk, for instance, can fly at about 150 knots.
The tilt-wing MV-22 Osprey, meanwhile, can hit speeds upward of 240 knots, but it's a hybrid--half helicopter and half airplane. It can hover when its propellers are turned upward, but to go fast, it needs to fly like a plane. Sikorsky clearly has the controversial Osprey in its sights. The small chart here from Sikorsky suggests how an X2 aircraft could match the Osprey for speed while beating it at feats such as hovering. (The plane at lower right in the chart represents vertical-take-off jets like the Harrier.)
(Credit:
Sikorsky Aircraft)
On Sunday, Sikorsky showed off its X2 Technology Demonstrator suite at Heli-Expo 2008 in Houston. A first test flight, however, remains some unspecified distance off in the future, with the research project having spent 2007 in build and subsystem test phase.
The most striking thing about the X2 design is that it makes use of coaxial main rotors, in contrast with the single main rotor that's been characteristic of mainstream helicopters since--well, since Igor Sikorsky himself helped popularize that arrangement in the 1940s. The coaxial rotor system has largely been the lonely province of helicopter makers like Russia's Kamov. (Tandem-rotor designs like the Chinook, meanwhile, have two large rotors fore and aft.)
The other notable aspect of the X2 is the rear-facing tail rotor. Helicopters like the Blackhawk with a single main rotor invariably have a tail rotor that faces the side, a necessity to counter the torque from the main rotor that would otherwise spin the fuselage like a top. The X2's coaxial setup would eliminate the torque, allowing the tail rotor to propel the helicopter forward much like the propeller on a ship.
Internally, an X2-based aircraft would have fly-by-wire (that is, electronic) flight controls, as opposed to traditional mechanical or hydraulic controls. Sikorsky says the eventual aircraft would serve as a "flying wind tunnel" to measure the performance of the rigid main rotors and their relationship to the rest of the aircraft's aerodynamics. No, nobody said that being a test pilot is easy.
At the Heli-Expo, a Sikorsky VP told Aviation Week that the company was gathering feedback from industry reps to help determine the initial commercial X2 product.
Before there was the A160T Hummingbird, there was the A160, a piston-driven UAV on which the turbine-powered A160T is based. This A160 flight was in early 2005.
(Credit: Boeing)Like its diminutive avian namesake, Boeing's A160T Hummingbird is a whiz at hovering. And it turns out the prototype aircraft can also hoist a hefty load.
The unmanned helicopter this week flew for eight hours--its longest flight to date--and as high as 5,000 feet while burdened with a 1,000-pound payload. The test flight goes a long way toward proving the Hummingbird fit for use in military operations, where it could ferry supplies, sensors or weapons to the battlefield, perform surveillance and target acquisition, or even rescue pilots who've been shot down.
Over time, Boeing wants to see the 35-foot Hummingbird fly longer, but with a lower weight: 18 consecutive hours with a 300-pound payload.
The A160T Hummingbird flew for the first time in June, and has flown several times since then. It's a turbine-powered version of the earlier piston-powered A160, which dates back to 2002, and the second of a planned 11 A160Ts that Boeing is building for DARPA.
Eventually, Boeing sees the Hummingbird flying for up to 20 hours at speeds above 140 knots and at altitudes reaching 25,000 to 30,000 feet (but hovering below 15,000 feet). A notable element in the design of this unmanned aerial vehicle is the variable speed of its 36-foot rotor; the UAV operator can adjust the rotors' RPMs at different altitudes and cruise speeds to improve flight efficiency.
If you see this bird hovering outside your window, you may be in trouble.
(Credit:
Boeing)
The Boeing A160T Hummingbird, the latest in unmanned chopper stealth and endurance, is under serious consideration by the U.S. Special Operations Command. Possible missions would include direct action, precision resupply and hairy extractions from behind enemy lines.
Remote-controlled helicopters are nothing new, as Boeing is quick to point out. This one is based on an old Robinson R22, which is still used as a trainer and to round up cattle. The main feature that makes the A160T unique is that it uses a rigid rotor to improve performance. The system automatically adjusts rotor revolutions to compensate for different altitudes, weight and cruise speeds.
The goal is to go higher and farther, hover longer and do it more quietly. Boeing expects this thing to do 140 knots, carry a 1,000-pound payload for 20 hours at a time and reach altitudes up to 30,000 feet.
The White House is getting ready to trade in its aging "Marine One" helicopter for a new model, though don't go looking for President Bush to take it for a spin.
The VH-71's first flight, July 2007.
(Credit: Lockheed Martin)The first test aircraft built for the VH-71 Presidential Helicopters Program made its maiden flight Tuesday--in British airspace--in a flight that lasted about 40 minutes, at speeds up to 135 knots.
Why the overseas locale? The helicopter isn't quite a cutting-edge design, despite the billing by its manufacturers as "the world's most technologically advanced helicopter." Instead, it's based on AgustaWestland's decade-old, three-engine EH101 helicopter, relabeled more patriotically as the US101 by lead contractor Lockheed Martin. (A "Made in America" note on the company's US101 Medium-Lift Helicopter page points out that more than 200 U.S. suppliers in 41 states have joined the US101 program.) The test flight of the VH-71 took place at the Yeovil, England, facility of AgustaWestland, which in turn is a unit of Italy's Finmeccanica.
It makes sense, of course, to be using a proven commodity when the passengers will include the leader of the free world and other heads of state. Lockheed Martin et al. say that more than 130 of the 101s, designed from the start for military duty, have logged upwards of 120,000 flight hours handling assignments ranging from troop transport to battlefield logistics and combat search and rescue.
The current version of Marine One.
(Credit: White House photo by David Bohrer )In addition, the US101 companies say, the helicopter's "low vibration will allow the president to work in transit in unprecedented comfort and efficiency."
In its new VH-71 guise, the aircraft is slated for more shakedown cruises before crossing the Atlantic in the fall for structural testing at a facility in Patuxent River, Md. (Lockheed Martin is based in Bethesda.) Three more test vehicles are expected to head aloft by early 2008.
Those four aircraft plus five pilot production versions of the VH-71 are expected to be delivered by late 2009, to complete the Increment 1 phase. Increment 2 will look at the helicopters' command and control capabilities while in flight.
At the moment, the primary presidential helicopter is the Sikorsky VH-3D, also known as the Sea King.
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