Performance of the Collision Avoidance Logic during Preliminary Flight Tests of the Traffic Alert and Collision Avoidance System (TCAS II)

摘要

Flight tests of a prototype Traffic Alert and Collision Avoidance System (TCAS II) were conducted by the FAA Technical Center between August and October 1981. One purpose of the flight tests was to verify the effectiveness of the TCAS logic in generating safe separation. Eight-three planned encounters were flown during the test program. In addition, 14 low approaches, which resulted in the display of seven resolution advisories, were made into Washington National and Chicago O'Hare Airports. Three encounters of opportunity were also recorded. A total of 93 encounters were analyzed for this document. The primary characteristics used to measure TCAS performance included the timeliness and correctness of the traffic and resolution advisories, and, where appropriate, the vertical separation provided by the system. The advisories generated during the flight tests were timely and were in the correct direction, based on the data at the time of sense selection. The vertical separation achieved at closest approach for each encounter was analyzed by a fast-time replay capability. With nine exceptions, this vertical separation was greater than or equal to the system threshold. In three of the exceptions, separation was reduced due to significant pilot delay in responding to the advisory; however the TCAS logic performed properly. Two exceptions produced only slightly less than the system's separation threshold. Logic enhancements added subsequent to the flights were found to successfully resolve these encounters. In the remaining four exceptions, abrupt intruder leveloff maneuvers foiled the TCAS sense selection logic, resulting in reduced separation.