Research On Minimum Safety Distance In Free Flight

The pilot has freedom to fly a continuously optimum trajectory in free flight. So compared with the present flight, free flight not only saves flight time, but also improves the utilization of airspace and gains greater capacity. However the flight mode has changed greatly in free flight. So in order to guarantee the safety of the flight, it is necessary to study the minimum safety distance.The main work of this paper is as following: Firstly based on taking the communication, navigation and surveillance(CNS)performances, human factors and the collision avoidance system into account, security guarantees based on flight process in free flight is proposed. Then calculation model of the minimum safety distance based on CNS performances in the same plane is established: analyze the impact of CNS performance on the position error of aircraft, and the affect is mapped to the distance between aircraft. The calculation model of the minimum safety distance based on CNS performances is established using probability theory. The combination algorithm of hill-climbing algorithm and dichotomy is used to optimize the minimum safety distance. And then conflict resolution model is established by adjusting the speed or turning heading angle in the long range. Finally the three-dimensional model of the minimum safety distance based on stochastic differential equations is built. Considering the response delay of pilots, hardware failures of the collision avoidance system and the lead time prior to initiating a maneuver, the latest maneuver moment is proposed. Given the randomness of the actual position of the aircraft, the collision risk model is built using stochastic differential equations. According to the conflict resolution rules of horizontal and vertical maneuver, the latest maneuver moment is optimized quickly using the dichotomy. Bringing the time margin, the minimum safety distance is calculated.