Experimental study of collision detection schema used by pilots during closely spaced parallel approaches

An experimental flight simulator study was conducted to examine the mental alerting logic used by subjects to issue a traffic alert and execute an avoidance maneuver. Subjects flew a series of autopilot landing approaches with traffic on a closely-spaced parallel approach; the subject was to indicate the point when they recognized a potential traffic conflict, and select an avoidance maneuver. Five traffic displays with increasing amounts of convergence rate information were evaluated. Subjects appeared to use the lateral deviation of the intruder aircraft from its approach path as the criterion for an alert. With displays showing heading and/or trend information, their alerting thresholds became significantly less conservative. However, this type of range-only schema still resulted in many near misses, as a high convergence rate was often established by the time of the subject’s alert. Therefore no display system reliably compelled subjects to alert timely enough for certain collision avoidance. These results suggest the design of automatic alerting systems should take into account the alerting schema used by the human, such that the rationale for the automatic alert should be trusted by the operator. Although careful display design may help generate pilot/automation trust, issues such as user nonconformance to automatically generated commands can remain a possibility.