Publications

Measurements of signals in the 1030 and 1090 MHz frequency bands have been made by MIT Lincoln Laboratory in the last several years, previously in the Boston area and most recently in April 2011, at JFK International Airport near New York City. This JFK measurement activity was performed as a part of the Lincoln Laboratory Traffic Alert and Collision Avoidance System (TCAS) work for the Federal Aviation Administration (FAA) and is the subject of this report. This report includes: 1) Overall characteristics of the 1030/1090 MHz environments, 2) Analysis of the TCAS air-to-air coordination process, 3) Examination of 1090 MHz Extended Squitter transmissions for use in TCAS, 4) Assessment of the extent and impact of TCAS operation on the airport surface.

Traffic Alert and Collision Avoidance System (TCAS) behavior in New England airspace is being monitored and analyzed, making use of an omni-directional 1030/1090 MHz receiver. The receiver system, located in Lexington, Massachusetts, and operated by MIT Lincoln Laboratory, is used to record data for subsequent analysis in non-real-time. This is the second report of MIT Lincoln Laboratory 1030/1090 MHz monitoring, covering the period March through June 2010. There are three main areas of study: 1. 1030 MHz data related to TCAS air-to-air coordination and other communications, 2. 1030 and 1090 MHz data related to TCAS surveillance, and 3. 1090 MHZ Extended Squitter data, i.e., the Mode S implementation of Automatic Dependent Surveillance-Broadcast (ADS-B). In addition to a summary of results, this report answers specific questions raised during the previous 2009 analysis and attempts to provide insights into the meaning of the data with respect to TCAS operation. This four-month period will be used to baseline 1030/1090 MHz activity in the New England area. Future plans call for the 1030/1090 MHz receiver to be moved so that limited data recording can be performed at various TCAS RA monitoring system (TRAMS) sites throughout the NAS.

This report documents the Lincoln Laboratory evaluation of the Traffic Alert and Collision Avoidance System II (TCAS II) logic version 7.1. TCAS II is an airborne collision avoidance system required since 30 December 1993 by the FAA on all air carrier aircraft with more than 30 passenger seats operating in the U.S. airspace. Version 7.1 was created to correct two potential safety problems in earlier versions. The first change focuses on the sense reversal logic. The second change focuses on avoiding "wrong way" responses to Vertical Speed Limit or "Adjust Vertical Speed, Adjust" RAs. Lincoln Laboratory evaluated the logic by examining more than eight million simulated pairwise encounters, derived from actual tracks recorded in U.S. airspace. The main goals of the evaluation were: (1) to study the performance of the revised sense reversal logic for encounters where one pilot ignores the TCAS advisory; (2) to determine if the revised sense reversal logic has an adverse impact on encounters where both pilots follow the TCAS advisories; (3) to determine if the change from "Adjust Vertical Speed, Adjust" advisories to "Level Off, Level Off" advisories provides a safety benefit for TCAS. Three sets of encounters were examined in order to fulfill these goals: encounters where both aircraft are TCAS-equipped and both pilots follow the advisories; encounters where both aircraft are TCAS-equipped and one pilot does not follow the advisory; and encounters where only one aircraft is TCAS-equipped. A detailed analysis followed by a summary is provided for each set of encounters. An overall summary is given at the end of the report.

Appendix to Project Report ATC-346, Evaluation of TCAS II Version 7.1 Using the Fast-Time Encounter Generator Model, Volume 1.

Volume I described the analysis procedures and inputs. This volume presents tables and figures that were generated during the assessment to the TCAS Logic Performance.

This report documents the Lincoln Laboratory evaluation of the Traffic Alert and Collision Avoidance System II (TCAS II) logic version 7. TCAS II is an airborne collision avoidance system required since 30 December 1993 by the FAA on all air carrier aircraft with more than 30 passenger seats operating in the U.S. airspace. Version 7 is a major revision to the TCAS II logic consisting of more than 300 separately defined changes affecting all majot TCAS areas (surveillance, CAS logic and displays/aurals). Lincoln Laboratory Evaluated the logic by examining approximately two million simulated pairwise TCAS-TCAS encounters, derived from actual tracks recorded in U.S. airspace. The main goals of the evaluation were: (1) to study the performance of the new TCAS-TCAS coordinated reversal logic; (2) to detect and explain any areas of performance; (3) to examine the performance of the version 7 logic for the 30 Representative NMACs identified during the 6.04a logic evaluation; and (4) to understand the limitations of the logic by analyzing every version NMAC. Five Lincoln Laboratory analysis programs written for previous logic evaluation work were updated and new software was written to aid in the evaluation of TCAS-TCAS sense reversals. There were four phases of the evaluation corresponding to the above goals. For each phase the report gives an overview of the evaluation approach taken and a description of the results. An overall summary and perspective on the evolution of the TCAS II logic are given at the end of the report.