摘要 : To reduce the possibility of mid-air collisions, Federal Aviation Administration has developed the Traffic-Alert-and-Collision-Avoidance-System. TCAS is mandated worldwide on all large aircraft. In this paper, an overall descripti... 展开 To reduce the possibility of mid-air collisions, Federal Aviation Administration has developed the Traffic-Alert-and-Collision-Avoidance-System. TCAS is mandated worldwide on all large aircraft. In this paper, an overall description of the existing TCAS system is presented, followed by a detailed description of the system and its functional performance. The current collision avoidance system has been in operation for more than a decade. But major transformations to the National-Airspace-System are being implemented through FAA's Next-Generation-Air-Transportation-System in the coming years and that will require substantial modification to the existing system. The development of such new collision avoidance system which is Airborne-Collision-Avoidance-System-X has been pioneered. This survey article also describes the basic concept behind ACAS-X and briefly demonstrates how this new flexible approach in collision avoidance logic is fully compatible with NextGen airspace procedures and technologies. The aim of this work is to review, understand and compare the current and next generation aircraft collision avoidance system. 收起