Final Approach Spacing Tool (FAST) velocity accuracy performance analysis

Abstract

The NASA passive Final Approach Spacing Tool (FAST) provides advisory information to the terminal air traffic controller for sequencing and merging of landing aircraft. It consists of the Trajectory Synthesizer (TS) and the Scheduling Logic (SL). FAST has undergone extensive field testing and performance evaluations of the FAST TS algorithms have been conducted. However, no analytical performance evaluations of the FAST SL logic have been performed to date. This paper evaluates the sensitivity of the FAST SL algorithms to velocity errors which are introduced by the radar tracking software. A linear error covariance analysis was performed of the terminal area radar and its alpha-beta tracking filter software. For comparison, an alternate Kalman tracking filter was also evaluated. Using these radar tracking velocity estimation error histories for a typical aircraft flight profile, the FAST TS estimated time of arrival (ETA) statistics history was obtained. To determine the impact of the velocity and ETA errors on FAST SL, figures of merit were defined which predict the probability that FAST SL will reach an incorrect aircraft sequencing decision. These figures of merit were then evaluated, based on the velocity and ETA statistics histories.

The Trajectory Synthesizer Generalized Profile Interface

“…As trajectory generation requirements continued to evolve based on the advanced descent and conflict prediction algorithms being researched, 17,18 the TS was rewritten again, this time in C++. This effort resulted in the Baseline TS with many of the benefits inherent with Object Oriented design, such as code reuse, code extensibility, and improved maintainability.…”

“…19 Although the TS software has gone through many design iterations, its core trajectory algorithms have remained intact, providing a consistent platform to conduct research and support operational systems. The trajectory engine has been repeatedly validated through research, and operationally via the deployed TMA system 16,17,20 . The GenProf interface is the next phase of redesign of this software.…”

Final approach throughput analysis for conventional and enhanced air traffic management

“…It is clear, however, that the ability of the surveillance system to deliver accurate, responsive speed estimates will be important to this application. Previous studies of the CTAS passive FAST decision support tool have shown that current generation alpha-beta trackers need to be replaced by modern tracking software to deliver the accuracy and reliability required for that tool [4]. It is anticipated that the Rh4S speed accuracy will then be on the order of 3 knots or better 131.…”

“…The other surveillance issue is that of update rate, which determines tracker lag in speed estimates. Based on results in [4], we assume that good steady state speed values are obtained within 30 seconds after completing a deceleration transient. Increasing the sensor update rate to reduce tracker lag is also highly desirable.…”