Fort Hill Group completed a quantitative assessment of the positive safety impact provided by air traffic controllers at Class D Airports.

Airport Traffic Control Towers (ATCTs) provide many benefits to the aircraft that they serve, including increasing airport capacity, efficiency, and safety. Providing these benefits, however, comes with considerable expenses associated with building, staffing, and operating these towers. While the benefits of ATCTs clearly outweigh the costs at large, high-traffic airports, this may not be the case at very small, low-traffic airports. The Federal Aviation Administration (FAA) originally developed criteria for the establishment and discontinuance of ATCTs in 1990. Since that time, operations in the National Airspace System (NAS) have, and are continuing to, transition to support Next Generation Air Transportation System (NextGen) initiatives and other enhancements. Therefore, the FAA is reviewing and potentially updating the cost, safety benefit, and efficiency benefit criteria used to evaluate the benefits of ATCTs at lower volume airports in Class D airspace.

The FAA’s Human Factors Research and Engineering Division enlisted the expertise of Fort Hill Group to examine the risks managed by controllers at Class D ATCTs and to quantify the safety benefits controllers provide in that environment. The purpose of this study was to identify the safety-critical tasks performed by tower controllers, to assess the operational safety benefit provided by tower controllers in Class D airspace, and to determine the potential safety benefit that a controller could provide if present during safety events occurring at non-towered airports.

Fort Hill Group conducted an Air Traffic Analysis and Classification System (AirTracs) benefits assessment of narrative safety event reports submitted by both controllers and pilots at Class D ATCTs. The data analysis yielded three statistically significant risk-benefit pathways that quantify the relationship between operational risks and controller benefits at Class D ATCTs. Identified significant pathways included the dynamic risk-benefit pathway, static risk-benefit pathway, and communication risk-benefit pathway. The dynamic risk-benefit pathway (shown below) quantifies the specific controller safety benefits provided by controllers to mitigate dynamic operational risk characteristics present at Class D ATCTs. A modified AirTracs benefits assessment of narrative safety-event reports submitted by pilots at non-towered airports resulted in five statistically significant risk-benefit pathways showing the controller tasks that could have reduced the severity or consequences of the reported events.

Dynamic Risk-Benefit Pathway


For more information on this project, please contact us at [email protected]