Carl Westin

122 Consistency and agreement in conflict resolution sents the second DS (including order of interactions if more than one interactions is made). Third is the resolution type , which identifies the general category of control maneuvers (i.e., altitude, heading, speed, or a combination thereof). The fourth DS defines the resolution type by assigning direction (e.g., left or right vector). The final, and fifth DS specifies the exact directional value of the resolution (e.g., vector 035 degrees or increase speed to 300 knots). Although time of intervention is an essential solution component, it was con- sidered independently. Time is a qualitatively different measure from other solution parameters that define the physical interaction, although the conflict geometry, and thus solution options, changes over time. Moreover, the time of intervention does not accurately reflect the time of detection or when the solution is conceived as the controller can choose to postpone intervention and monitor the conflict. 6-3-1 Solution parameters hierarchy classification The solution parameters hierarchy argues that controllers distinguish between the aircraft in conflict and selectively decide on which to control, which resolution type to use and in which direction to deviate. The hierarchy reflects the algorithm archi- tecture of several CD&R systems that have been based on controller-elicited knowl- edge, such as ISAC, 131 COCOS, 31 and the artificial intelligence A* graph search model. 32 The specific choice of aircraft to interact with is also supported by re- search indicating that controllers at times assign one aircraft as the “trouble maker” causing the conflict. 29 The first DS specifies the number of interactions made to solve the conflict (i.e., whether one or both aircraft were controlled). 6-3-2 Control problem classification Alternatively, a conflict can be viewed as a control problem . This perspective fo- cuses on the control action implemented to solve the conflict (e.g., vector aircraft ahead or behind), 24 and argues that a conflict only can be solved by one aircraft going behind, in front, above, or below the other. The aircraft interacted with first is designated the controlled aircraft that is instructed to avoid the other intruder air- craft. As such, the first DS describes the solution in relation to where the controlled aircraft will pass the intruder aircraft (laterally behind or in front , or vertically un- der or above ). In contrast to the solution parameters hierarchy, the control problem classification disregards the number of interactions made as only the first interaction is relevant. Moreover, the first DS does not differentiate between aircraft interacted with as only the control action is of interest. For example, for DS 1, vectoring air- craft A behind B is considered the same as vectoring B behind A. In both solutions, the controlled aircraft is vectored behind the intruder.