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 point-mass 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.