Cost Analysis of the Departure -En Route Merge Problem

Thetechnicalchallengesassociatedwithmergingdepartureaircraftontotheire ledroutesinacongestedairspace environment is discussed. A cost assessment of merge strategies that are based on four-dimensional e ight manage- ment principles and cone ict detection and resolution is given. Several merge cone icts are studied and a cost for each resolution is computed. In addition, the effects of uncertainties on the cost are assessed. In general, altitude hold for a departure aircraft is a less expensive resolution strategy than vectoring. HEFederalAviation Administration (FAA)has forecasted that thenumberofcommercialaircarrierandcommutere ightswill continue to increase yearly.Unless there are changes made tothe air trafe c control system, the increase in trafe c will resultin substantial delays. As a result, the FAA is undertaking a modernization of the air trafe c control system. This effort includes a hardware upgrade of the existing air trafe c computer system and the development of softwaretoolstocomplementtheairtrafe ccontroller' sexpertskills. Thesoftwaretools areintended toenhance theairtrafe ccontroller' s situational awareness and to provide decision support aids for tac- tical and strategic decisions. The Center terminal radar approach control (TRACON) Automation System (CTAS), which is being developed at NASA Ames Research Center in cooperation with the FAA, is one example of a set of software tools intended to enhance the air trafe c controller' s ability to schedule and control air trafe c through accurate trajectory predictions, scheduling algorithms, and trafe c forecasts. 1,2 Concurrently, Eurocontrol, a multinational con- sortium of western European countries, is developing a modernized air trafe c control system to be used throughout western Europe. These tools are intended to assist controllers with the management of air trafe c in all phases of e ight. Historically, the emphasis of air trafe c control research has been placed on solving problems regarding the handling of arrival trafe c, asthishasbeentheprimarysourceofdelayandcongestion.Morere- cently, the emphasis has moved toward cone ict detection and other concepts related to free e ight. Free e ight is an advanced concept whereby individual aircraft select, and are permitted to e y, optimal trajectories. It is foreseen that the job of the air trafe c controller may become more passive, requiring intervention only when con- e ictsarise.Cone ictresolutionanddetectionstrategieshavebeenthe subject of much research. 3i 5 In the United States the development of cone ict probe tools has occurred independently at the Center for Advanced Aviation Systems Development (CAASD) and NASA Ames Research Center. The foundation on which all decision support tools are built is an ability to accurately predict a given aircraft' s state in the near fu- ture. The necessity oftrajectoryprediction in a time-based airtrafe c controlsystemdue to the presence of aircraftwith and without four- dimensional e ight management systems has been discussed. 6 Ac- curate four-dimensional trajectories enable potential cone icts to be more reliably predicted. As a result the separation between aircraft can be maintained. Four-dimensional guidance and fuel-optimal