Raytheon has delayed its planned flight test of a heavy fuel engine with Swift Engineering's blended wing-body Killer Bee unmanned air vehicle from May, with bench testing ongoing, the company confirms.

Also on trial with Raytheon's Cobra UAV, which has already tested the Killer Bee's avionics, the new engine is intended to meet demand from the US military for a heavy fuel design to provide better logistics.

The Killer Bee is Raytheon's proposal for the US Navy/US Marine Corps small tactical unmanned air system (STUAS)/Tier II requirement, which also has US Air Force involvement.

"We have a purpose-built heavy fuel engine built for the Killer Bee," Raytheon mission system solutions advanced programmes director Ryan Hartman said during the Association for Unmanned Vehicle Systems International North America 2008 convention in San Diego, California. Flight International has previously reported this as being a 15hp (11kW) XRDi design.

Raytheon has also been working with the USN on arming the Killer Bee, and is expecting to conduct a guided firing of the service's Spike miniature missile.

Raytheon's known competitors for the STUAS/Tier II programme are the AAI Aerosonde Mk4, Insitu Integrator, and the General Dynamics/Elbit Systems Skylark II.

Source: Flight International