Required Action Time and Control Effectiveness in Resolving Pairwise Conflicts

Abstract

Due to limitations in their performance capabilities, aircraft must begin avoidance maneuvers well before specified minimum separation standards are reached. In other words, there is a time ahead of a predicted conflict at which aircraft must start to act. This paper presents the concept and a systematic procedure for determining the REquired ACtion Time, or REACT, for pairwise conflict resolutions. REACT marks the least advance time necessary for successful avoidance maneuvers and defines the minimum lookahead window for reliable trajectory predictions. In this paper, the process of conflict detection and resolution is divided into a series of segments, and typical times associated with these segments are estimated. Pairwise conflicts in different encounter geometries are considered. Aircraft flights are described with a dynamic pointmass model that uses position and velocity components as states, and excess thrust, lift, and bank angle as controls. Motion constraints due to both aircraft performance limitations and passenger comfort considerations are imposed. In resolving a potential conflict, it is assumed that one of heading change, altitude change, or speed change is used. Both cooperative and non-cooperative maneuvers are studied. Uncertainties in onboard trajectory state measurements, pilot response delays and behaviors, as well as initial aircraft speeds are represented as random variables. Monte-Carlo numerical simulations are conducted to establish trends of REACTs over different encounter angles for every single control authority. The effectiveness of different control authorities in resolving conflicts are compared.