Conflict detection algorithms can be broadly classified as state based and intent based algorithms. State based algorithms predict the path of aircraft by projecting their current position and velocity vectors. The path predictions are then used to determine if the aircraft are in conflict within a look ahead time. That is, if loss of separation occurs in the future. Intent based algorithm uses flight plans and other information, which usually resides in a flight management computer, to predict the path of aircraft. Algorithms that use intent information for conflict detection obtain the intent of other aircraft and broadcast their own intent via some type of communication link. Intent information that is exchanged among the aircraft is defined as explicit intent. A conflict detection algorithm can also make use of intent information based on aircraft nominal routes, corridors, published approaches, etc., and in this case, there is no information exchange between aircraft. This kind of intent is defined as implicit intent. Implicit intent can be used very effectively in conflict detection without the added cost and complexity of communication links. The use of implicit intent, in combination with state information, reduces false alarms over a state based conflict detection algorithm and therefore increases the effectiveness of the alerting system. In this paper, conflict detection using implicit intent information is described and its performance is compared with a state based conflict detection algorithm.
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