High Hover Finds Hidden Hostiles

Signal, Jun 2007 by Robinson, Clarence A Jr

A retractable landing gear for the A160 enables autonomous takeoff and landing from airfields or from the decks of ships at sea. The landing gear arrangement also provides sufficient ground clearance to carry a centerline sensor or resupply pod beneath the aircraft. "With the retractable landing gear, the Hummingbird reduces drag and can carry a 1,000pound payload to a radius of 500 kilometers for priority resupply missions. This load-carrying capability provides a possible command, control, communications, computer, intelligence, surveillance and reconnaissance [C4ISR]/resupply platform for Army, Navy, Marine Corps and other government agencies," Hunt explains. "The UAV is also being evaluated for special operations, data relay and crew recovery missions, and it could be armed with weapons such as Hellfire and Javelin anti-armor missiles or similar ordnance."

The Hummingbird's concept of operations is to base the aircraft within theater using it as necessary to support dismounted troops. Lower echelon forces can provide input to the system for priority reconnaissance missions. The UAV also can carry an unmanned ground vehicle, which it would land at precise locations possibly for use in inspecting improvised explosive devices, Hunt discloses.

Advances in A160 aeronautical systems are expected to have a far-reaching effect on the U.S. helicopter industry. System reliability enables 1,000 flight hours between air vehicle losses. Industry is developing diesel aircraft engines for the Hummingbird separately for DARPA, and these will boost loiter time on station with a full sensor payload, Hunt notes. The UAV program is conducting development tests with heavy fuel engine technologies in support of, and in coordination with, other DARPA programs. These highly efficient diesel engines would improve operational reliability and battlefield logistics compatibility.

A challenge from the beginning of the A160 program is scarcity of aerodiesel engines. Karem and Frontier began development of the KW660 diesel engine for the Hummingbird, but with Boeing's purchase of the company the engine effort is slipping. Flight tests have been conducted with a fourcylinder Subaru engine and an upgraded version of that engine that flew more than 55 hours on 24 flights. A sixcylinder Subaru engine also completed six flights. More than 1,000 hours of engine-powered ground and flight testing have been completed.

A diesel no longer is planned for installation in A160 in the current Phase 1. The focus is on a turboshaft engine in order to prove the basic aircraft performance and value. "We still have some residual diesel engine studies going on during Phase 1, and a follow-on program could include diesel engine installation into the UAV," Hunt acknowledges. "Nominally, a diesel engine, with its lower fuel consumption, could nearly double the 20-hour endurance of Ae turboshaft variant to allow the Hummingbird to achieve around 40 hours endurance."

The diesel engine companies include FEV, Auburn Hills, Michigan, and Achates Power LLC, San Diego, California. Meanwhile, a Pratt & Whitney 207D turboshaft engine has been installed in the A160, along with a two-speed transmission. The A160 needs longer development and is not ready to enter Phase 2, Hunt asserts. While DARPA pushes the technology out as fast as possible, the A160 is being developed efficiently and economically. Many of the pending reliability and endurance gains may be achieved in a follow-on phase.