TCAS Operational Performance Assessment in the U.S. National Airspace

Ongoing monitoring of safety critical systems is an important means of ensuring that system performance meets requirements and facilitating proactive identification and resolution of potential problems. The Federal Aviation Administration (FAA) recently implemented one such effort, the TCAS Operational Performance Assessment (TOPA) program. This program records automatic downlinks of all TCAS Resolution Advisory (RA) events within sensor coverage and correlates the RAs with surveillance data, calculates performance parameters and permanently stores the data for future analysis. Periodic and focused reports are prepared based on these data. This paper summarizes key analyses of over 15,000 TCAS RAs collected in the period April - September 2009 at 5 major terminal areas in the U.S. National Airspace (NAS). Most RAs occurred below 5,000´ in Class E airspace and involved low performance General Aviation (GA) intruders. Although no significant issues were observed with the performance of TCAS logic, the analysis showed that pilot compliance with Climb and Descend RAs did not meet system design assumptions. These results indicate that pilot training and the design of future systems must explicitly consider these factors.