Evolution of the US Navy's collision avoidance systems (CAS) to future airborne capability environment (FACE)

The US Navy's collision avoidance systems (CAS) software product consists of five different system capabilities: ground proximity warning system (GPWS), terrain awareness warning system (TAWS), obstacle avoidance system (OAS), mid-air collision avoidance system (MCAS), and auto-recovery CAS (AutoCAS). GPWS provides directive controlled fight into terrain (CFIT) protection against fight into level or descending terrain. TAWS provides directive CFIT protection against level, descending, and rising terrain. OAS provides directive protection and situational awareness, through a display, of man-made obstacles. MCAS provides passive protection and awareness of other airborne aircraft. AutoCAS provides active protection by interacting with the avionics system to take control of the aircraft to automatically avoid impact with terrain, obstacles, and/or aircraft. For each capability, the software product provides advisories or directive aural warnings and visual indications to the aircrew. The goal is to maximize protection and minimize nuisance warnings to ensure aircrew trust the system in a dynamic tactical environment [1]. Balancing protection with nuisance warnings is done by embedding an aircraft-specific performance model into the CAS software product.