Unmanned bomber prepares for crucial tests: Air Force UCAV development accelerated, but some technical challenges remain.

• Author: Tiron, Roxana

An influx of new funds and growing confidence in the technology are providing much needed momentum to the Air Force Unmanned Combat Air Vehicle. Program officials said that, at the current pace, the aircraft could be ready to join the fleet before the end of the decade.

The UCAV, built by the Boeing Corp. in Seal Beach, Calif., passed medium-speed taxi tests earlier this year at Edwards Air Force base. High-speed taxi tests were scheduled to begin last month and flight rests could take place as early as the end of May.

With the high-speed taxi, "We are going to be able to prove that we have command and control of the vehicle [moving at] up to 140 knots on the ground," Col. Michael Leahy, the UCAV program director at the Defense Advanced Research Projects Agency, told National Defense. "The data that we get on those tests say that we have sufficient confidence, regarding the navigation and control algorithm to proceed to the first flight."

Once the first flight is completed, a series of system checkup flights is planned. "That is going to take us into the late summer time, when we progressively expand the envelope," he explained. Unlike current drones, such as the Predator, the UCAV operates autonomously. It has to take off, land and taxi without any human operator directing it.

The UCAV is "not one of those toy vehicles," said a Boeing official close to the program, who did not want to be quoted by name. The aircraft is meant to go into combat during the "toughest first three days of the war," to try destroying enemy air defenses and feeding targeting information to other manned aircraft in the area.

The aircraft that is now being tested, has gone through several design changes since the first UCAV concept was designed in the late-1990s. The Air Force and DARPA are in charge of the program.

The first prototype, the X-45A, is representative of the requirements set in 1998, which have since changed.

George Muellner, president of Boeing's Phantom Works, explained that, after assessing the X-45A vehicle, the Air Force decided that it wanted a slightly larger payload and different maneuver tactics. The result is the current X-45B model. "It [the vehicle] increased slightly, but I don't think it is going to be dramatic," he said. The basic systems are going to be the same, he emphasized.

The overall length of the vehicle increased by 14 percent, and the wing area grew by 63 percent. The larger wing area offers a wider angle-of-attack range and...