Can Heliplane Fill the 'Connector' Gap in Navy's Sea Basing Concept?

Sea Power, Sep 2004 by Burgess, Richard R

'There Are People Who Believe' in Gyroplane Technology-Based Design

The Pentagon Office of Force Transformation and the Navy's fleet readiness and logistics office are assessing a 50-year-old technology to fill one of the biggest gaps in a naval warfighting concept for the future. The heliplane, a hybrid craft with both a rotor and wings, might be a way to provide the fleet with heavy lift "connectors" to rapidly move troops and materiel from ships at sea to tactical units ashore.

A key to the Navy's sea basing concept is for a craft that can lift a 40,000-pound cargo container and move it quickly to forward units. The idea behind sea basing is that U.S. forces sent to world hot spots will operate from the sea rather than building supply depots and headquarters ashore. Striking from ships at least 25 miles from shore, they would avoid traditional battlefront tactics and rely on the elements of high-speed strike, maneuver and surprise to force adversaries into a reactive posture. However, the services lack the fast, powerful "connectors" necessary to make that happen.

Arthur K. Cebrowski, director of the Office of Force Transformation, recently told reporters, "There are some things that we are keenly interested in. One of them is work on a gyrocopter. We stopped research on gyrocopters a long time ago, but right now there are people who believe" - and have demonstrated with a small-scale flying prototype - "that we may be able to lift upwards of 70,000 pounds at 450 knots and fly it over 30,000 feet and do vertical takeoff and landing."

The concept of which Cebrowski spoke is a proposed design by Carter Aviation Technologies of Wichita Falls, Texas. The design, called a Carter Heliplane Transport 150 (CHT-150), is a craft the size of a C-130 cargo plane. The heliplane is based on gyroplane technology in which a rotor is used for vertical and slow-speed flight. When cruising at high speeds, the wing provides all the lift, Carter Aviation said. The heliplane has long wings for efficient cruise, a four-blade rotor for hover and slow-speed flight, and two 24-foot-diameter lightweight pusher propellers for forward propulsion.

In flight, the heliplane gradually transfers lift and flight functions from the rotor to the wings. "A rotor is a very efficient device for providing lift at low speeds, but its drag increases rapidly" if the rotor must continue to support the aircraft as it picks up speed, according to a statement on the company's website. As the wings produce more of the lift, the rotor slows down, decreasing drag.

Jonathan Kaskin, director of strategic mobility and combat logistics for the office of the Chief of Naval Operations, said the heliplane is "going to be evaluated as a sea base connector" along with other concepts such as the large quad tiltrotor transport. "The Defense Science Board made a strong case for that type of capability."

At an Aug. 3 Defense Writers Group breakfast in Washington, D.C., Cebrowski said, "One of the things that you could probably start putting your money on is that we are going to see changes in transportation and battlefield mobility systems. ... You stop building the transportation system based on getting from the United States to someplace else. And you start focusing instead on what kind of battle the forces want to fight."

The heliplane is an old concept. In the 1950s, McDonnell built the four-person XV-I and a British company, Fairey, built the much larger Rotodyne, capable of carrying 45 passengers. Neither got beyond prototype development.

Carter maintains they gave up too quickly. "We're coming back to challenge helicopter and tiltrotor technology," said Rod Anderson, the company's vice president for marketing.

For the Navy, Carter Aviation is proposing the CHT-100, a scaled down version of the CHT-150. Anderson said the CHT-IOO would lift 50 troops or a standard 40,000-pound shipping container and fly a low-level combat radius of 300 to 600 nautical miles, depending on load, at 260 knots.

"We have the world's best rotor technology," Anderson said. The Carter rotor, with its tip-to-tip carbon spar, hollow airfoil shell and small rotor hub is much less complex and one-third the weight of a comparable commercially available rotor, Anderson said.

The company has built and is testing the CarterCopter, a five-seat gyroplane with a slowed rotor compound design, for concept development. It first flew in September 1998. The Defense Advanced Research Projects Agency recently awarded two contracts totaling $375,000 to help finance additional refinements of the aircraft's rotor, propeller and landing gear.

In April, the Army Research, Development & Engineering Command awarded an 18-month contract potentially worth $1 million to collect data during a 30- to 50-hour flight test program. The Army/NASA Rotorcraft Division at Ames Research Center, Moffett Field, Calif, and the Georgia Institute of Technology are developing more sophisticated software models for slowed rotor aircraft.

By RICHARD R. BURGESS