General Atomics Aeronautical Systems (GA-ASI) said it has demonstrated an early prototype of its “due regard” radar for unmanned aircraft systems (UAS) on a manned surrogate aircraft, joining other efforts to develop airborne “sense-and-avoid” systems that could help introduce UAS into unrestricted airspace.

Installed on a Twin Otter turboprop, the active electronically scanned array (AESA) radar-based system was tested in flight for the first time October 17 in California off the coast of San Diego and in Borrego Springs, an area surrounded by the Anza-Borrego Desert State Park. During the test, the system successfully detected an “intruder” King Air encroaching on the Twin Otter’s airspace.

GA-ASI said the due regard radar is a company-funded effort that supports its overall radar-based airborne sense-and-avoid architecture for the Predator B UAS. Following the completion of manned flight tests, testing will begin on unmanned aircraft. “Development work will continue until the radar has achieved technology readiness level seven, tentatively setting the stage for customer introduction in 2015,” the company said.

The company called the California demonstration, announced in late February, “a major milestone” in the development of its airborne sense-and-avoid architecture. “Equipping a highly reliable UAS such as Predator B with this capability will expand its capacity to operate routinely in domestic and international airspace, ensuring its interoperability with civilian air traffic and airspace rules and regulations,” said Linden Blue, president of the GA-ASI reconnaissance systems group.

The U.S. Air Force Research Laboratory (AFRL) said in January that it completed a multiple intruder autonomous avoidance flight demonstration using a Calspan Flight Research-operated Learjet and four intruder aircraft, two of them operated by the FAA Tech Center. The Learjet in-flight simulator was fitted with electro-optic sensors, traffic collision avoidance system and automatic dependent surveillance-broadcast system working in conjunction.

In November, Sierra Nevada said it completed the first airborne demonstration of a prototype X-band radar with electronically reconfigurable array under the AFRL-sponsored Multi-Sense Detect, Sense and Avoid program. Colorado Engineering is leading the development of an electronically scanned array C-band radar for the AFRL. Meanwhile, last March the U.S. Navy awarded prime contractor Northrop Grumman a $25 million contract to design a common sense-and-avoid system for the MQ-4C Broad Area Maritime Surveillance (Bams) aircraft and the Air Force’s RQ-4 Global Hawk. The solution includes a nose-mounted lightweight AESA radar supplied by ITT Exelis, plus ADS-B and TCAS.

The European Defense Agency has selected the Alenia Aeronautica Sky-Y medium-altitude, long-endurance UAS for the Midair Collision Avoidance System project to demonstrate an in-flight sense-and-avoid system for use in non-segregated airspace. The five-nation effort has a stated goal of developing baseline solutions for UAS collision avoidance “acceptable by the manned aviation community” by 2015.