Analysis of Terminal Separation Standards and Radar Performance

The United States is in the process of commissioning new consolidated Terminal Radar Approach Control (TRACON) facilities to serve large complex terminal areas. In addition to receiving surveillance data from radars formerly serving each individual TRACON, the consolidated TRACON facilities will receive surveillance data from all available sensors in the area including long-range en route radars. The new facilities will have the ability to use mosaic displays to combine surveillance data from multiple surveillance sensors. Current terminal area separation requirements allow three-mile separation between aircraft provided both aircraft are within 40 miles of a single terminal radar. At issue is whether three-mile separation can be maintained throughout consolidated TRACON airspace using a mosaic display. This paper reviews the error characteristics of longrange and short-range sliding-window Air Traffic Control Radar Beacon System (ATCRBS) and Monopulse Secondary Surveillance Radar (MSSR) surveillance sensors. Errors in the separation distance between targets displayed to a controller were analyzed for both single sensor and mosaic displays. Monte Carlo simulations were run to compute the errors in displayed separation as a function of range from the sensor. It was found that MSSR sensors offer an approximately three-fold increase in azimuth accuracy over sliding-window ATCRBS and provides equivalent separation performance at a range of over 100 miles in single sensor mode. It was also found that MSSR sensors in a mosaic display offered separation performance equivalent to a single sliding-window ATCRBS sensor when each aircraft is within 40 miles of its respective sensor. Sliding-window ATCRBS shortrange sensors in mosaic display mode offer acceptable performance when each aircraft is within 28 miles of its respective sensor. This work is sponsored by the Federal Aviation Administration under Air Force Contract No. F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the U.S. Government. Introduction The United States is in the process of commissioning new consolidated Terminal Radar Approach Controls (TRACON) facilities to serve large complex terminal areas. Southern California TRACON is now operational, Northern California TRACON and the Potomac TRACON are in the transition stage. Other consolidated TRACONs are planned in the future. Consolidated TRACONs replace the individual TRACONs serving the area, each formerly relying on a single terminal radar to serve a single major airport and surrounding satellite airports. Consolidated TRACONs offer operational advantages in complex airspace including increased surveillance coverage and the capability to optimize airspace and operations within the area covered by the facility. This promises more efficient control of aircraft during transition to and from airports. In addition to receiving surveillance data from radars formerly serving the individual TRACONs, the consolidated TRACONs will receive surveillance data from all available sensors in the area including longrange en route radars. The new facilities will have the capability of mosaic display of multiple surveillance sensors. In mosaic display mode, the airspace is divided into equally sized square or rectangular “sort boxes.” Each sort box represents a geographic area and is assigned a preferred sensor, a supplemental sensor, and tertiary sensors (if available). The preferred sensor is used to provide surveillance data as long as a satisfactory track of the target is maintained. In mosaic mode, different sensors may track aircraft being separated by a controller. Problem Statement and Approach An Individual TRACON controlling traffic in it’s respective terminal area separates traffic by three nautical miles for aircraft less than 1000 feet apart in altitude. At issue is whether or not the current three-mile _________________________________________ 1 In this paper, “miles” refers to nautical miles.