LONDON -- BAE Systems is beginning to detail previously classified unmanned combat air vehicle (UCAV) research efforts, including flying a representative low observable air vehicle.

BAE first flew a UCAV demonstrator, dubbed Raven, in late 2003. The low observable design is part of the company's wider work into UCAV technology for the British Defense Ministry.

Two Raven carbon-fiber composite airframes have been built and flown. Test flights of the jet-powered UCAV demonstrator were carried out in Australia at the Woomera Range. Radar cross-section reduction is a key element of the airframe design. The air intake is mounted on top of the fuselage, with control surfaces on the wing aligned with the trailing edge. The airframe is a flying-wing configuration, with no vertical or horizontal tail surfaces.

British Defense Ministry interest in UCAV technology first emerged as part of its Future Offensive Air System (FOAS) program. The effort was intended to identify capabilities to fulfill the deep strike role now provided by the Royal Air Force's Tornado GR4. FOAS has since been succeeded by the Strategic Unmanned Aerial Vehicle (Experiment) (SUAVE) -- which Raven feeds into.

SUAVE will be the focus of additional UCAV work, including a further technology demonstrator program. A UCAV capability will form an element of the U.K.'s future deep strike capability, though the timeframe for its entry into service is likely 2015-2020.

Along with examining the design and manufacture of an Low Observable UCAV design, the Raven was also used to develop and test a digital flight control system for the aerodynamically unstable design. The Raven is fully autonomous from takeoff to landing, with the flight control system providing the air vehicle with considerable maneuverability.

The Raven's central fuselage is common with that of BAE's Corax program. This is a sub-scale design of a strategic surveillance UAV -- though its wingspan is still in excess of 10 meters. Corax first flew at Woomera in early 2005. Part of the trials were to examine the flight characteristics of the finless high-aspect ration wing design, in part to avoid the kind of control problems encountered by the U.S. Darkstar program.

Along with electro-optical payloads, the Corax configuration lends itself to the carriage of a large conformal array antenna on the wing.

The company is not only working on UCAV and strategic reconnaissance applications. Its Herti family is intended to develop a range of tactical long-endurance UAVs. The Herti has an operational radius of 540 nautical miles and is capable of flying at altitudes of 20,000 feet. A number of Herti air vehicle designs are also being flight-tested.