Aircraft wake vortices are strongly counterrotating tubes of air that are generated from aircraft as a consequence of the lift on the aircraft. The safety concern of wake vortices, particularly when lighter aircraft are following heavy planes, has caused the Federal Aviation Administration (FAA) to enact minimum separation requirements during the arrival phase of flight. These separation standards are imposed during Instrument Flight Rules (IFR) and are a significant capacity constraint at the largest U.S. airports. Any movement toward increasing air traffic efficiency, such as concepts toward free flight, must address increasing runway capacity if they are to be fully effective. Wake vortex measurements clearly show that current wake vortex separations are overconservative in many weather conditions, and that these separations could be safely reduced by adapting the separations to the current weather state.
The Aircraft Vortex Spacing System (AVOSS) is being developed by the National Aeronautics and Space Administration (NASA). The AVOSS project has been researching wake vortex behavior and preparing a demonstration of a weather-adaptive system for reducing aircraft arrival separations. In order to have aircraft available to take advantage of reduced arrival wake separations, Air Traffic Control (ATC) must have advance notice (> 30 minutes) of future aircraft separations. This requires that meteorological variables which influence vortex behavior be accurately forecast so that vortex behavior models can provide the separation criteria. Vortex transport is strongly affected by the local winds and vertical wind shear, while vortex decay is thought to be largely dependent on the level of turbulence and thermal buoyancy forces.
This paper addresses the requirements for the weather portion of AVOSS. The operational decisions that need to be supported are addressed, which helps to define the necessary time scales of the nowcasts. An analysis is presented of meteorological conditions during which an AVOSS would provide capacity enhancement at major U.S. airports. Finally, a discussion of the current understanding of the meteorological variables that affect vortex behavior will be made, including expected accuracy and temporal and spatial resolution.
* This work is sponsored by the National Aeronautics and Space Administration Lamgley Research Center. The views expressed are those of the author(s) and do not necessarily represent the official policy or position of the U.S. Government.
+ Opinions, interpretations, conclusions and recommendations
are those of the authors and are not necessarily endorsed by the United
States Air Force
The 8th Conference on Aviation, Range, and Aerospace Meteorology