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R. Brad Perry*, David A. Hinton**, and Robert A. Stuever***

NASA Langley Research Center
Hampton, Virginia


The National Aeronautics and Space Administration (NASA) is addressing airport capacity enhancements during instrument meteorological conditions through the Terminal Area Productivity (TAP) program. Within TAP, the Reduced Spacing Operations (RSO) subelement at the NASA Langley Research Center is developing an Aircraft Vortex Spacing System (AVOSS). AVOSS will integrate the output of several inter-related areas to produce weather dependent, dynamic wake vortex spacing criteria. These areas include current and predicted weather conditions, models of wake vortex transport and decay in these weather conditions, real-time feedback of wake vortex behavior from sensors, and operationally acceptable aircraft/wake interaction criteria. In today?s ATC system, the AVOSS could inform ATC controllers when a fixed reduced separation becomes safe to apply to ?large? and ?heavy? aircraft categories. With appropriate integration into the Center/TRACON Automation System (CTAS), AVOSS dynamic spacing could be tailored to actual generator/follower aircraft pairs rather than a few broad aircraft categories.


ATC Air Traffic Control
AVOSS Aircraft Vortex Spacing System
CTAS Center/TRACON Automation System DOT Department of Transportation
FAA Federal Aviation Administration
ILS Instrument Landing System
ITWS Integrated Terminal Weather System MIT Massachusetts Institute of Technology ____________________________________________ * Manager, Reduced Spacing Operations. Associate Fellow AIAA.
** Research Engineer.
*** Research Engineer, Senior Member AIAA. Copyright ? 1996 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. Code. The Government has a royalty-free license to exercise all rights under the copyright claimed herein for Government purposes. All other rights are reserved by the copyright owner.

MOA Memorandum of Agreement
NASA National Aeronautics and Space
NOAA National Oceanic and Atmospheric Administration
RSO Reduced Spacing Operations
TAP Terminal Area Productivity
TASS Terminal Area Simulation System TRACON Terminal Radar Approach Control


Air travel delay and traffic congestion at major airports, projected increases in air travel, and environmental restrictions on new airport construction, together with associated costs to the traveling public and to the air carriers, have led to an increased interest in maximizing the efficiency of the national airspace system. The National Aeronautics and Space Administration (NASA) is responding to this interest through its Terminal Area Productivity (TAP) program. The major goal of the TAP program is to develop the technology, during instrument meteorological conditions, which allows air traffic levels to approach or equal levels presently achievable only during visual operations. Presently, a degradation in weather conditions which causes a loss of visual approach capability degrades capacity due to numerous factors. These factors include reducing the number of available runways and the longitudinal wake vortex separation constraints used by air traffic control (ATC) in the spacing of aircraft to a runway. Two major initiatives under TAP are the enhancements of basic ATC automation tools and the development of a wake vortex spacing system to improve terminal area efficiency and capacity. The NASA Ames Research Center is developing enhancements to the base Center/TRACON Automation System (CTAS). This automation will provide aids and interfaces to the controller to effectively schedule and sequence arrivals and minimize variations in desired interarrival spacing. Enhanced CTAS automation will provide an opportunity to dynamically alter the longitudinal wake vortex separation constraint as a function of both the weather effects on wakes and aircraft leader/follower pair types.