X-47 Pegasus Naval Unmanned Combat Air Vehicle (UCAV-N), USA

The Pegasus unmanned air vehicle was initially developed under private funding by the Integrated Systems Sector of Northrop Grumman at El Segundo in California. Pegasus received its X-47A designation in June 2001.

The X-47A provided a proof of concept for the Defense Advanced Research Projects Agency (DARPA) and the US Navy UCAV-N programme, and is Spiral 0 in the spiral development programme which was targeted towards US Navy requirements. A similar programme managed by DARPA and the US Air Force covered the development of the Boeing X-45 targeted towards the US Air Force requirement.

DARPA announced the Joint Unmanned Combat Air Vehicle (J-UCAS) programme to meet both the Air Force and Naval requirements. In October 2005, DARPA handed the programme over to a joint USN and USAF office. The Spiral 1 development phase under the J-UCAS program includes the design of the improved demonstrator air vehicles, X-45C and the X-47B.

The roll out ceremony of the proof-of-concept X-47A vehicle was in July 2001 and the first flight was successfully completed in February 2003.

The X-47B is a larger variant of the X-47A. In August 2004, DARPA awarded the contract to Northrop Grumman for three X-47B demonstrator UCAVs and an operational assessment phase to last from 2007–2009.Construction of the X-47B began in June 2005.

In February 2006, the J-UCAS programme was cancelled by the US Department of Defense and the USAF and USN were to follow separate UAV programmes. Northrop Grumman halted work on the X-47B.

In August 2007, Northrop Grumman was selected by US Navy for the Unmanned Combat Air System Demonstrator (UCAS-D) with a version of the X-47B with Pratt & Whitney F100-PW-229 engine. The programme is to demonstrate the suitability of an autonomous UAV for aircraft carrier operations and identify critical technologies. Two demonstrator air vehicles are to be built. Flight testing is scheduled to begin in late 2009, carrier landings in 2011 and the programme will conclude in 2013. It will include catapult take-offs, arrested landings and flight in the immediate vicinity of the carrier.

X-47 PEGASUS AIR VEHICLE

The airframe is a stealthy planform design. It is diamond-kite shaped with a 55° backward sweep on the leading edge and a 35° forward sweep on the trailing edge. The X-47A has a wingspan of 8.47m and is 8.5m long; the dimensions of the X-47B have yet to be finalised.

Scaled Composites Inc of Mohave, California, were contracted to manufacture the all-carbon composite airframe. The air vehicle has no tail or vertical fin. Instead of a traditional rudder for yaw control, the upper and lower surfaces are each fitted with two sections of moving surfaces. A large elevon is clearly visible at the mid-section of each trailing edge.

The vehicle is robustly built for carrier take-off and landings and uses a conventional wheeled take-off and landing with an arrestor hook. The retractable tricycle-type landing gear consists of a single nose wheel, twin wheel main landing gear and a fully retractable arrestor hook. Smiths Aerospace is providing the landing gear for the X-47B.

PEGASUS AVIONICS

The Pegasus is equipped with an avionics suite supplied by BAE Systems Platform Solutions of Johnson City, New York. The avionics and vehicle management computer performs flight control processing, autopilot control, engine control processing, mission command and control, navigation and other functions.

The computer features an embedded, open-architecture CsLEOS real-time operating system which uses 'brick-wall' time and memory partitioning to allow multiple applications to run on the same system without interfering with each other. The system also provides multiple scheduling modes, allowing users to switch between different schedule profiles in real time.

The navigation systems include the United States Navy Shipboard Relative Global Positioning System (SRGPS) automatic landing system.

TURBOFAN ENGINE

The Pegasus is powered by a single Pratt & Whitney Canada JT15D-5C turbofan engine rated at 14,19kN. The air vehicle carries 472kg of fuel but has a maximum capacity of 717kg of fuel for long-range operations or for increased loiter times.