PETER LA FRANCHI / ADELAIDE
Priority is being given to manned and unmanned military requirements but application may be extended to airliners
Algorithms for the automatic air collision avoidance system (ACAS) for manned and unmanned air vehicles being developed by Sweden and the USA are to be tested in Saab's Gripen simulator later this year.
Planning is also underway for flight trials using two Lockheed Martin F-16s at the US Air Force's Edwards AFB test centre. A proposed NASA trial involving an F-16 and a General Atomics RQ-1 Predator UAV has been suspended following the US space agency's withdrawal. Programme officials have also revealed they are looking at the long-term development of a passive, 360° sensor and alerting system to allow use on a wider range of aircraft types, including airliners. In the near term, however, priority is being given to manned and unmanned military requirements with data shared between approaching aircraft using tactical datalinks.
The USA is looking to the system to provide separation between UAVs during swarm strikes, while Sweden wants to use the system to improve pilot safety. Industry support is being provided by Boeing, Lockheed Martin and Saab.
Edward Griffin, a Lockheed Martin programme official, says preliminary simulations have shown the basic algorithm can achieve last-minute aircraft separations at only seconds notice. Griffin told the Institute of Electrical and Electronics Engineers Information, Decision and Control Conference in Adelaide last week: "We have done some preliminary ACAS simulations based on the current algorithm that we are working with. We have done a head-on collision scenario, an air combat manoeuvre scenario and we have looked at the latency impact on the algorithm."
One head-on collision test had aircraft at 6,000ft (1,830m), travelling at Mach 1.3, giving a M2.6 closure rate. "On one run, we did it at 0.5s temporal sphere, which was about a 1,400ft bubble around the aircraft. The algorithm executed around 4s into the test, gave us a 1,400ft separation distance, and it held [the manoeuvre] for about 4s. Another one that we did was a 100ft distance. It executed about 5-6s into the simulation run, and only held it for approximately 1s, but it gave us about 80ft minimum separation distance."
Source: Flight International
