Simulation and Lockheed Martin F-16 flight trials next year could pave way for autonomous UAV operations

A Swedish/US team will this week test an automatic air-to-air collision avoidance system (AutoACAS) in simulators at Saab's factory in Linköping.

AutoACAS has been designed to prevent collisions during training and is an enabling technology for autonomous unmanned air vehicle (UAV) operations.

The $12 million programme is funded jointly by Swedish defence materiel administration FMV and the US Air Force Research Laboratory. Boeing, Lockheed Martin and Saab are participants.

Ragnar Rosengren, Saab project manager, says the week-long trial - with Swedish and US pilots - will be run in two of Saab's JAS39 Gripen simulators and on two PC-based simulators. Flight tests are planned on USAF Lockheed Martin F-16s starting June/July next year.

The tests follow an initial phase, which ended last year, during which the three companies separately developed AutoACAS proposals. AutoACAS builds on a terrain-avoidance system - the ground collision avoidance system - developed by the same team, but without Boeing, between 1997 and 1999.

Saab's proposal was selected for further development. AutoACAS works by reserving areas to where the aircraft automatically flies, if a collision is imminent, using a 5g manoeuvre.

Each safe area is a cone of space, which widens the further from the fighter it is. When two cones intersect, the escape manoeuvre is triggered, the control is removed from the pilot and AutoACAS commands the escape manoeuvre. Each fighter has three possible escape manoeuvres, one that represents the current escape path and two that are efforts to reserve areas for the next escape zone. System refresh rate is 10Hz. A special mode allows two aircraft to join for formation flying, says Rosengren.

By linking the aircraft with a datalink, the system - which is software-based and does not require hardware changes - ensures each fighter has reserved a unique sanctuary. Risk is further reduced as the AutoACAS turns the fighters away from each other during a manoeuvre. Saab has simulation-tested the system with four aircraft.

Rosengren says there are plans to test an "out of network" system, without datalinks, relying on other sensors. Changes for UAVs would require the vehicle to manoeuvre before a manned aircraft has to alter course, and have a less aggressive escape manoeuvre.

Source: Flight International