This week, Eurocopter's X3 high-speed helicopter demonstrator wraps up its U.S. tour with a stop in Washington for military-customer demo flights from Fort Belvoir and a static display at the Pentagon on Thursday (July 26).
All photos: Mike Hirschberg, AHS
EADS North America is pushing the compound-helicopter's military potential and Steve Mundt, VP of business development and a former head of U.S. Army aviation, says the company is "very, very interested" in the Pentagon's Future Vertical Lift (FVL) initiative to replace the U.S. military's helicopters with a family of advanced rotorcraft beginning in 2030.
The X3 clearly offers more speed than a conventional helicopter—it has reached 232 kt. in level flight and 242 kt. in a dive—that's 50% faster than a conventional helicopter using just 80% of available power—but the U.S. military has been interested in speed before, and always ended up with conventional helicopters cruising around 150 kt.
The reason, says Mundt, is that more speed and range is great, but you still need to be able to maneuver with the agility of a helicopter when you get there. Especially when, as FVL plans, you are replacing the AH-64, AH/UH-1, UH-60 and MH-60. And the X3 can do it, he says, because it has a conventional helicopter main rotor to which are added two variable-pitch props at the ends of short wings, all driven from the same main gearbox.
The X3 takes off vertically and hovers like a helicopter, but push forward on the "coolie-hat" thumb switch on the collective lever and prop pitch increases, the helicopter accelerates into forward flight and flies—and climbs—like a fixed-wing turboprop. Subscribers who want to know how the X3 flies can read Doug Nelms' pilot report in the July 9 AW&ST.
Mundt sees military value in the X3's ability not only to accelerate and decelerate in a level attitude, but to point the nose up or down in flight to improve target tracking. Also, the props can be used to slow the aircraft in a dive— an ability to "hang" over the target that Sikorsky also claims for its X2 Raider coaxial-rotor compound helicopter.
But what about those big props? Are they vulnerable? No more than a tailrotor, Mundt says, and the X3 can fly with just one prop working. Do they get in the way? Yes, says Mundt, but only if you think in terms of loading and unloading through side doors."We need to change mentally. If we raise the tail and fit clamshell doors, troops can get in and out faster." The X3's ability to point its nose up or down also helps align the fuselage with the ground for slope landings, something a conventional helicopter can't do, he says.
The X3 is a technology demonstrator for something Eurocopter calls the H3—High-speed long-range Hybrid Helicopter—a concept that is scalable from 6 tonnes gross weight to "much more" than 14 tonnes, says Mundt. "We think it can replace the V-22 under FVL, where the desire of the DoD is to go for as much commonality as it can [across its fleet of rotorcraft]," he says.