The US Defense Advanced Research Projects Agency (DARPA) and Frontier Systems are completing fabrication of the first long-endurance A160 Hummingbird unmanned air vehicles (UAV) which will enter flight testing late this year or in early 2001.

DARPA and Frontier Systems have been secretly working on the project since early 1998. They decided to lift the veil partially off the closely-held technology only recently.

The 1,820kg (4,000lb), 11.3m (37ft)-long A160, which is about the size of the General Atomics Predator medium-altitude UAV, is expected to have an un-refuelled range of 5,550km (3,000nm) with 30-40h endurance. This will allow for non-stop self-deployment from the continental USA to Western Europe with a 182kg payload.

Dr Arthur Morish, DARPA's programme manager, says: "The payoff is to get the aircraft to the US armed forces, allowing them to do things they can't do now. It promises very dramatically-improved performance, greater ranges and longer endurance than was previously possible for UAVs. This has the potential to be really revolutionary." Military and civil rotorcraft applications could follow, he adds.

The A160 exploits a hingeless, rigid, three-bladed rotor system to produce a vertical take off and landing UAV with very low disk loading and rotor tip speeds. The result is an efficient, low power loiter and high endurance, says Morish. The Hummingbird employs a 224kW (300shp) piston engine. The breakthrough comes from a patented Frontier Systems-designed flight control system (FCS) that allows for routine flight operations just above the stall. The A160's predicted top speed is 140kt (260km/h).

Two A160 demonstrators are being built and a third may follow. Remotely-piloted Robinson Maverick R22 helicopters were used to test the FCS and avionics destined for the A160. The basic flight test schedule, which includes 200h of flight envelope expansion, will be followed by a technology development programme lasting 3-4 years, during which a four-blade rotor system is expected to be evaluated.

Various US military services are monitoring the project. Its transition to engineering and manufacturing development and to production will depend on establishing a military requirement.

Source: Flight International