TAILLESS SUPERSONIC PLANE REVIVED.

Byline: Jim Skeen Staff Writer

EDWARDS AIR FORCE BASE - The Defense Department is revisiting a page out of NASA Dryden's past to check out the viability of an unusual airplane design for future long-range military jets.

The oblique flying wing would be a tailless, supersonic airplane with a ``scissors'' wing in which one wingtip points forward and the other back at high speed - reducing drag and letting it fly fast on less power.

``What we envision is an X-plane program,'' said Thomas Beutner, program of the Defense Advanced Research Projects Agency. ``Like the X-1 or the X-29, the Oblique Flying Wing program will be a technology demonstrator that explores a concept that can only be proven in flight.''

Northrop Grumman is working on a $10.3 million DARPA contract for preliminary design and risk reduction work on the aircraft design.

If successful, the preliminary design effort may be followed by a second phase that would finalize a detailed design and build and flight test an X-plane, with first flight expected in 2010 or 2011.

The oblique-wing design concept is attributed to the late Robert T. Jones, a NASA aeronautical engineer credited with advancing the idea of swept wing aircraft in the 1940s. Jones believed that an oblique wing supersonic transport aircraft might achieve twice the fuel economy of an airplane with conventional wings.

``One of the things he was interested in was a plane with wings that pivoted,'' said Alex ``Skip'' Sim, a former NASA Dryden engineer. ``As a young engineer at the time, I was intrigued by it.''

NASA's own low-speed oblique-wing airplane, the AD-1, flew in the late 1970s and early 1980s at Dryden Flight Research Center. Burt Rutan, who would later gain fame with the Voyager aircraft and SpaceShipOne, contributed to the aircraft's design.

Dryden project participants described the project as a low-cost, simple effort. The airplane was built under a $240,000 contract.

``When we built the AD-1, we were not able to find funding for an airplane to go into a supersonic flight regime. What we could do with the money we had was look at handling qualities at slow speeds,'' said Sim, who worked on the AD-1. ``AD-1 was a handling qualities test - to see from a pilot's perspective how it would fly.''

The twin-engine jet had an electronically driven mechanism that would slowly pivot the wings. The wing could pivot to as much as 60 degrees.

The airplane was flown 79 times during a roughly three-year period. The angle of the pivot on the aircraft was slowly increased during the course of the flight test program until it reached the full 60 degrees.

``The side forces are very significant once you get past 45 degrees,'' said Tom McMurtry, a retired NASA test pilot who was the AD-1 project pilot. ``It was not a nice flying airplane.''

Jones considered the oblique wing a viable concept after the flight testing, but the aviation industry was cool to the idea, perhaps because of the AD-1's poor flying qualities. McMurtry and Sim said the AD-1 had a very simple mechanical flight control system and the poor flying could have been addressed in a more sophisticated airplane.

``I would have liked to have seen a high-speed demonstrator built, but at the time we couldn't find the funds within the agency,'' Sim said.

McMurtry said he was not surprised at the renewed interest in the concept.

``I wish them well,'' McMurtry said of the DARPA effort.

In announcing the contract award, DARPA acknowledged the NASA AD-1 effort and previous engineering studies on the concept. However, DARPA pointed out that no one has attempted high-speed flight and that their concept calls for a tailless aircraft.

Jim Skeen, [phone]

james.skeen(at)dailynews.com

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Photo:

(color) The oblique flying wing - a supersonic airplane concept from the 1940s being developed by DARPA - would be a tailless craft with a ``scissors'' wing in which one wingtip points forward and the other back at high speed, reducing drag.

Northrop Grumman