Human Factors Studies of an Ads-b Based Traffic Alerting System for General Aviation

Mid-air collisions are a concern for general aviation. Current traffic alerting systems have limited usability in the airport environment where a majority of mid-air collisions occur. A Traffic Situation Awareness with Alerting Application (TSAA) has been developed which uses Automatic Dependent Surveillance – Broadcast (ADS-B), a Global Positioning System (GPS) based surveillance system, to provide reliable alerts in a condensed environment. TSAA was designed to be compatible with general aviation operations. It was specifically designed to enhance traffic situation awareness and provide traffic alerting. The system does not include guidance or resolution advisories. In addition, the design was consistent with established standards, previous traffic alerting system precedents, as well as air traffic control precedent. Taking into account the potential financial burden associated with installation of a multi-function display (MFD), an audio based TSAA system was also designed to account for constrained cockpit space and the added cost of a MFD. TSAA system performance and usability was tested by installing the system in an aircraft and having 21 general aviation pilots use the system in-flight. Pilots flew with the system during planned encounter testing as well as in typical high density traffic pattern environments in Daytona Beach, FL. Pilot’s awareness of traffic awareness, out-the-window visual acquisition, and evasive action were recorded throughout the testing. A total of 109 encounters were analyzed comprising of 89 planned encounters and 20 targets of opportunity. The alert provided the first indication of an encounter in a majority of cases. In general, pilots considered alerts to be appropriate in both the planned encounter cases and the targets of opportunity. In most cases, pilots did not deem evasive action necessary during the high density flights, despite considering the alerts to be appropriate. Out-the-window visual acquisition was made in 40.5% of cases for the planned encounters, and 81.0% of cases for the targets of opportunity. For the cases where visual acquisition was made in the planned encounters, pilots made visual acquisition approximately 13s (SD=21s) after an alert annunciated. In target of opportunity cases, pilots made visual acquisition approximately 8 seconds (SD=32s) before an alert annunciated. The differences in visual acquisition could be due to the different geometries experienced with planned encounters as well as the different flight test regimes. Pilots also indicated that the alert provided accurate information, and reported that they could trust the system. Pilots considered the alerts to be timely in 64% of encounters and too late in 36% of all encounters. In general subjective feedback suggested that the display symbology was effective, with some improvements desired in terms of font size and target vs obstacle discriminability. Overall the system was well received by pilots in the postflight evaluation. This research tested the pilot performance using the display system and the audio system. The findings of the studies will contribute to TSAA standards development for the FAA and design recommendations for avionics manufacturers. . HUMAN FACTORS STUDIES OF AN ADS-B BASED TRAFFIC ALERTING SYSTEM FOR GENERAL AVIATION