Time–Space Diagram as Controller Support Tool for Closed-Path Continuous-Descent Operations

Abstract

Tactical control during a closed-path continuous-descent operation is unwanted because it reduces the aircraft’s ability to follow the optimized descent profile. To prevent tactical control, air traffic controllers apply arbitrarily large spacing buffers to ensure separation throughout the descent. A controller support tool is required for early deconfliction, spacing, and sequencing to facilitate these operations without the need to apply large buffers. The time–space diagram decision support tool was developed previously to make the constraints and complexity of a continuous-descent operation perceptually evident and provide tools and information to the controller to be an active problem solver. This paper addresses the further development and validation of the interface. The concept of visual momentum was applied to enhance the efficiency of working the multidisplay interface that consists of the plan view display and time–space diagram. Direct-manipulation tools were developed to enable the controller to plan and implement actions, such as speed and altitude control. A controller-in-the-loop-experiment was set up to validate the interface. In the experiment, subjects used either the time–space diagram support tool or, as a baseline, a stack list that provided the required spacing and the time to lose or gain. Both interfaces enabled the subjects to space the aircraft safely and efficiently. Compared to the baseline, the time–space diagram interface freed time to plan traffic ahead using the direct-manipulation interfaces, which (according to all subjects) worked intuitively. The number of instructions per aircraft was decreased by 35%. Early accurate speed control was applied, and use of heading vectors was no longer necessary in most scenarios. As a result, aircraft commenced their continuous descent at a higher altitude and greater distance from the runway. Controller workload was significantly reduced, and situation awareness was increased.