Re: Flying wing UAV (X-47B)

Message posted by Matthew Ruch on December 31, 2008 at 16:04:54 PST:

You are referring to the X-47B UAV tha was just publically unveiled last week...see the attached picture...

This is the article that appeared in last weeks issue of Aviation Week and Space Technology...



Wraps Come Off U.S. Navy's First Tailless, Stealthy Unmanned Aircraft

Dec 21, 2008

By Guy Norris

Northrop Grumman's X-47B unmanned combat air system (UCAS) demonstrator reveals an unprecedented emphasis on all-aspect stealth for the maritime environment.

Unveiled at the company's Palmdale, Calif., site on Dec. 16, the X-47B is the U.S. Navy's first dedicated stealth aircraft since the ill-fated General Dynamics/McDonnell Douglas A-12, canceled in 1991. The X-47B is designed to demonstrate technology for a naval UCAS that would perform the stealthy strike mission originally intended for the A-12, but with the much-increased range and endurance of an unmanned aircraft.

The program's focus on low observability (LO) at sea potentially puts the Navy on a fast track to catch up with the U.S. Air Force in stealth design. But to be a viable option for the Navy's emerging F/A-XX requirement for a 2025-timeframe strike aircraft, the UCAS must show that it can replace a manned aircraft on carrier flight decks.

"She is as stealthy as she looks," says Scott Winship, Northrop Grumman's Naval UCAS program manager. The tailless flying wing combines "all-spectrum, all-aspect" low observability with the ruggedness required for day-to-day shipboard operations, he adds. Incorporating the B-2A bomber's low radar cross-section (RCS) design aspects with the systems and control features of the much smaller X-47A Pegasus demonstrator, the X-47B makes use of a wing-fold system derived from the A-12.

The first air vehicle, AV-1, is scheduled to fly on Nov. 11, 2009, while AV-2 will be completed around December 2009. Both will be used to evaluate the viability of an unmanned combat aircraft in carrier operations; the first X-47B carrier landing is expected in November 2011.

The outer 16 ft. of each wing folds up 135 deg. to reduce the overall 62.1-ft. wingspan to 30.9 ft. Achieving this with a wing-fold mechanism that did not compromise the RCS with a "bulge" in the outer mold line of the wing "was one of the more difficult design problems," says Winship. The same requirement drove the A-12 designers to develop a "double roll" hinging mechanism that was modified by Northrop Grumman to keep the X-47B wing skin smooth on both sides. The A-12 never advanced beyond the mockup stage.

The wing hinge line and narrowly slotted fold zone, although visible on AV-1, are expected to be given LO treatment with blade seals similar to those developed to cover the gaps between the edges of the elevons and ailerons as well as the wing trailing-edge "island" supporting structure. These were not shown at the rollout because of their proprietary design. The edges of the island will also be inlaid with conventional radar-defeating diamond, or cat's-eyes, shapes, says Winship. GKN Aerospace developed the X-47B's composite skins, covers and doors, and was responsible for the design, tooling and manufacture of the outboard wing and the forward center fuselage section.

GKN also developed large blade seals to minimize potential radar returns from the trailing-edge recess cavity exposed during aileron movement. Described simply by Winship as a "new material," the radar-absorbing material used in the broad seal is flexible and spring-mounted to maintain tension over the forward section of the aileron. The seal therefore moves with the aileron, but snaps shut to become flush with the wing surface with the ailerons in a neutral position. Roll and yaw control is also executed with very large spoiler panels measuring 3 X 5 ft. on the upper wing surface forward of the ailerons.

Elevons can be drooped by 20 deg. for landing, but no deflection is required for the catapult launch, says Winship. "We generate lift in a hurry, so much so that we can launch off in any direction," he adds. The company believes that being able to launch from the deck, regardless of wind direction, significantly increases operational flexibility as the carrier does not need to alter course into the wind. "I don't know of any other aircraft that can do that," he says.

Lockheed Martin was responsible for refining the detailed low-observable features of the leading and trailing edges, control surfaces and engine inlet. The work was largely perfected on a full-scale RCS pole model at Lockheed Martin's Helendale measurement facility in the Mojave desert, about 25 mi. from Palmdale.

The shift to the larger, winged configuration of the X-47B away from the sharp, diamond-kite-shaped X-47A - with a 55-deg. backward sweep on the leading edge and a 35-deg. forward sweep on the trailing edge - did not force Northrop Grumman "to give up on stealth," says Winship, who describes the larger UCAS as a "six-pointer instead of a four-pointer." The X-47B's wing extensions provide greater range and superior flying qualities compared with the unstable X-47A, which Winship called a "Flying Dorito" after the shape of a popular brand of tortilla chip. The A-12 was also given the same nickname.

Structural proof tests will be conducted in a loads test rig scheduled to run from March to May 2009. The tests will simulate carrier landing and critical flight loads, as well as check the structure for catapult and arrestment loads, fuel system integrity and control-surface freedom under load. From June 2009 onward, engine run-ups and taxi tests should take place prior to the vehicle's transfer to nearby Edwards AFB for flight tests. The X-47B may fly the short distance or "be trucked," he adds.

Following first flight, AV-1 will undergo a year-long envelope-expansion test period at Edwards before being ferried to the naval test center at NAS Patuxent River, Md. This phase will focus on working up to carrier demonstrations, and will include catapult certification tests at Lakehurst Naval Air Engineering Station, N.J. Further tests will include a period at Norfolk, Va., where it will be craned onto the deck of a Nimitz-class carrier for dock-side taxi trials.

A final phase at Patuxent will be followed by a November 2011 landing on a carrier at sea. This is likely to be the USS Truman, which "right now looks as if it's going to be in the right place at the right time," says Navy N-UCAS program manager Capt. Martin Deppe.

In Reply to: Flying wing UAV posted by Nelson on December 31, 2008 at 15:33:26 PST:


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