Design, implementation and evaluation of a system to support Well Clear
Both from an operational and from a design perspective there is a need for an objective, quantitative definition of “well clear”. The Sense and Avoid Science and Research Panel (SARP) considered three concepts for the definition of well-clear. All concepts use a spatial threshold as part of the criterion. A so-called Velocity Scaled Protection Volume (VSPV) concept, additionally uses a time constant to compute two separate spatial thresholds: One based on ownship velocity and one based on intruder velocity. The other concepts use a temporal threshold based on the relative velocity between ownship and intruder. The quantitative definition was tuned to yield a 1.5% probability of an NMAC in case of an unmitigated well clear violation. In August 2014, the SARP recommended a quantitative definition of well clear to RTCA SC-228. To aid the pilot in remaining well clear, several concepts for the conflict prediction and resolution function are being pursued. These concepts differ in the design of the graphical user-interface but also in the level of automation (LOA) applied for Decision Selection. With a LOA of 2, the conflict prediction function offers a complete set of decision/action alternatives. An example of a concept in which this LOA is used is the conflict probe display. The conflict prediction function uses the well clear definition to compute whether and if so where a well clear violation is predicted to occur for a specified range of manoeuvre options, and presents the resulting conflict space to the pilot. Every manoeuvre that is predicted to avoid the conflict space is a potential option to remain well clear. Based on this and other information, the pilot can select a manoeuvre. In case the LOA of the function is increased to 4, the system will only present a single manoeuvre option to the pilot. This is more comparable to a Traffic alert and Collision Avoidance System (TCAS) Resolution Advisory (RA). Two designs of a conflict probe display have been realized as extensions to a CDTI. With both systems, the algorithms that define the well clear boundary and the spatial and temporal thresholds can be manipulated. The implementations have been used in a range of evaluations, both in simulation and actual flight test. The full paper will discuss the design aspects and decisions, the implementation and results in more detail.  For the purposes of this work, “Sense and Avoid” and “Detect and Avoid” are two terms referring to the same functionality.  For the purposes of this work, “Traffic Avoidance” and “Self Separation” are two terms referring to the same capability.  The SARP is a U.S. government funded organization designed to bring together SAA community stakeholders to close known research gaps.