Boeing is pinning its long-term future in the strike aircraft market on a US Navy contract worth roughly $2 billion that could be awarded as soon as 3 August for a carrier-based, unmanned warplane. The Unmanned Combat Aircraft System-Demonstrator (UCAS-D) deal is all that remains from a convoluted, seven-year series of plans to develop two candidates - Boeing's X-45 and Northrop Grumman's X-47 - to compete for a range of surveillance, electronic attack and strike missions for both the USN and the US Air Force.

The air force withdrew after the Joint Unmanned Combat Aircraft System (J-UCAS) programme was cancelled in 2005, leaving only the USN's requirement to demonstrate that a low-observable, unmanned aircraft could safely and efficiently operate from carrier decks by fiscal year 2013. The navy then has the option to pursue a follow-on acquisition programme.

The programme is now seen as the only hope for Boeing and Northrop to keep a foothold in the market for carrier-based strike aircraft. UCAS-D is the first and only contract for a new naval combat aircraft since Lockheed Martin won a competition in 2001 to develop the F-35C Joint Strike Fighter.

UCAS-D "is critical to the long term for our ability to be in the strike aircraft business", says Darryl Davis, Boeing's vice-president for Global Strike Systems. The company's challenge is to produce the X-45N, a virtually all-new aircraft compared with the land-based X-45A/B/C series developed to meet the USAF's needs for a stealthy penetrator. The X-45N will be scaled up by 25-30% compared with the X-45C, resulting in a 16,300kg (36,000lb) aircraft with a wingspan not to exceed 21.3m (70ft), says Davis.

Boeing is designing the X-45N to carry a 2,720kg payload of undisclosed sensors and weapons, with the shape of its weapons bay based on carrying Raytheon's AGM-154 JSOW air-to-surface missile. General Electric is named as the company's only public partner, and is believed to be supplying its F110 engine.

The most visible change to the X-45N's outer-mould line is a bulge running down the length of the centreline on the underside of the fuselage, Davis says. This feature was required to meet the USN's need for sensors and field of regard, he adds. The aircraft's structure comprises three major subassemblies.

But Northrop's X-47B has the advantage of having been designed from the start to meet the USN's carrier landing requirements, although the company has trailed Boeing's flight-test progress with earlier models of the X-45. The X-47B is designed to hold about 2,040kg of weapons stores, including Boeing's GBU-31 JDAM guided bomb, Northrop says. The aircraft also should accommodate either the Raytheon APG-79 or Northrop APG-81 active electronically scanned array radar.

"We based the electronic support measures system provisions on the J-UCAS common ESM system, a derivative of the [Raytheon] ALR-69U," Northrop says. "These provisions include four upper and four lower antenna locations to satisfy coverage requirements. The imaging sensor provisions are included in the weapons bay, providing the ability to accommodate alternative sensors."

Source: Flight International