Eurocopter's X3 Shows Old Designs Could Be The Future of Army Aviation

By Dan Parsons

By Dan Parsons

MANASSAS, Va. — Helicopter manufacturers in pursuit of Pentagon contracts are combining airplane propellers with helicopter rotors. The goal is to satisfy the military's growing demands for fast and agile helicopters.
Eurocopter brought its experimental “high-speed long-range hybrid helicopter,” or X3, to the Washington, D.C., area to show it off to potential commercial and military customers as part of a cross-country demonstration.
The X3 was put through its paces for defense reporters and company employees at Manassas Regional Airport July 23. Two test pilots swooped low over the airfield, pulling high-angle climbs and tight, nearly inverted rolls. It also accelerated and decelerated in level flight — a trick traditional helicopters can’t pull off — and took off and landed vertically, a feat impossible for airplanes. 
“In the center of the frame, which is a conventional frame, a conventional gearbox, which is a well-known technology in helicopters,” said Daniel Semioli, an X-flight test engineer. “In place of a tail rotor we add propellers … and that’s all. It’s simple.”
Company officials did not reveal a price tag for the aircraft, but said that they are confident that X3 will be cost competitive in future Army programs, such as the replacement of 4,500 medium-lift aircraft.
Stephen Mundt, vice president of business development for Eurocopter’s U.S. division EADS North America, and a former chief of Army aviation, said the aircraft has a huge potential. As the Army moves toward its self-imposed 2030 deadline to achieve a radically new vertical-lift technology, Mundt said the X3 could conceivably replace the Apache, Cobra, Blackhawk and Huey designs currently in use.
“Do I believe this aircraft has military applications?” he said. “As a pilot who’s been there and done it, you bet I do.”
The experimental model that has been making rounds at Army bases in recent weeks is a light-medium version that Eurocopter officials say can be scaled from 6 tons to a 14-ton version. It could conceivably be scaled even larger — heavier designs would require bigger engines, but the basic technologies like the wings and rotors can be made larger and longer, said experimental test pilot Herve Jammayrac.
“We will need an engine with a specific conception” to go larger than 14 tons, he said. “We know the performance already as long as we have the same shape.”
The X3 could even replace the tilt-rotor V-22 Osprey, Mundt said. Unlike the Osprey, the X3 combines fixed-wing with rotary wing technologies in such a way that there is no transition period between hover and flight modes. The Osprey, while both fast in airplane mode and maneuverable in hover, is vulnerable when in transition, and is less agile than traditional helicopters even with its engines in hover, Eurocopter officials said.
The X3 combines a traditional overhead rotor with dual forward-facing props mounted on short wings. Standing in for a single tail rotor, the propellers allow forward flight in excess of 260 miles per hour, while retaining the hover and maneuvering capabilities of a traditional helicopter, company officials said. That speed was achieved with 80 percent of the X3’s power. “We haven’t even seen what the X3 is capable of,” said Eurocopter President and CEO Marc Paganini.
The aircraft can accelerate and decelerate in level flight, a capability that allows pilots to remain focused on their objective. Its propellers allow a 40-degree climb at 3,500 feet per minute and can bank up and down at hover through a range of 40 degrees, which would help in target acquisition, Mundt said.
The X3 is one of only two hybrid aircraft that have flown under “high-hot” circumstances with airplane-like speed and the hover and maneuverability of a traditional rotorcraft. High-hot refers to the Army’s preferred performance requirements that its future helicopters fly at 6,000 feet at 95 degrees Fahrenheit. The other is Sikorsky’s X-2 demonstrator, which is currently being developed into the S-97 Raider, but no longer flies. 
The Raider hasn’t flown, so the Army will have to wait until at least 2014 if it wants to consider the new aircraft. Sikorsky officials have pointed out that the Raider’s basic technologies — coaxial rotors and an airplane propeller — are currently in use and well understood.
Combined in a similar, yet very distinct way, the two technologies are the same that power the X3. Instead of a singe “push” propeller, the X3 has two forward-facing props suspended out and downward from the base of the main rotor by short wings. It also has only a single main rotor. Like Sikorsky, Eurocopter is marketing the design as a low-risk combination of mature technologies that are familiar to pilots and engineers.

Topics: Aviation, Rotary Wing

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