Analysis of divergences from area navigation departure routes at DFW airport

Abstract

The Next Generation Air Transportation System (NextGen) calls for the extensive use of trajectory management for aircraft to achieve precision flight paths [1]. To understand, develop, and model systems that support these NextGen operations, especially in the terminal area, NASA is looking at today's precision operations to gain insight into the expected behavior. This paper documents characteristics of aircraft that are both on and vectored from routes in the execution of area navigation (RNAV) precision departures to support precision modeling and provide for NextGen super density operations research. Dallas/Fort Worth International Airport (DFW) was selected for this case study as these kinds of precise departure procedures have been in daily use there for years. One-third of DFW RNAV departures encounter some form of vectoring away from the defined RNAV routes. The majority of these, about one-quarter of the departures, are given direct routings that bypass fixes on the route and shorten the distance flown within the Terminal Radar Approach Control (TRACON). These divergences primarily result from controllers taking advantage of opportunities in the airborne traffic, similar to direct-to routing in enroute airspace [2], and are not the result of departure sequencing or avoiding loss of separation. During the planning of the RNAV procedures, some of this vectoring was expected and even encouraged, but the number of aircraft so affected has grown over time. Pilots and air traffic controllers use the precision navigation capability required for the RNAV departure procedures to bypass portions of the routes. While this is applicable to DFW alone, it is a reminder that the human elements in the system frequently find new and innovative uses for elements of the procedures, or the technology behind them. The numbers of aircraft vectored in the course of RNAV departure operations is comparable to those departing with reduced spacing, the main benefit of the original RNAV implementation. The data presented here demonstrate the flexibility of the procedures as currently used.