Impact of the Reduced Vertical Separation Minimum on the Domestic United States

Aviation regulatory bodies have enacted the reduced vertical separation minimum standard over most of the globe. The reduced vertical separation minimum is a technique that reduces the minimum vertical separation distance between aircraft from 2000 to 1000 ft, for cruise altitudes between 29,000 and 41,000 ft It was first introduced over the North Atlantic in March 1997, and, more recently, over the domestic U.S. in January, 2005. Previous studies by EUROCONTROL and the Federal Aviation Administration have found that, by allowing for more efficient flight trajectories, the implementation of reduced vertical separation minimum can reduce fuel burn and related emissions by 1.5%-3%. However, the modeling techniques used in these prior studies did not directly include weather or the influence on changes in engine-specific fuel consumption with throttle setting, Mach number, or altitude. Because of the influence that these factors may have on accurately predicting changes in fuel burn with small changes in aircraft operations, we sought to assess the influence of these assumptions, to develop improved modeling methods, and to use these improved methods to make a new estimate of the impacts of the reduced vertical separation minimum. This document estimates the impact of reduced vertical separation minimum within the continental U.S. for a sample of 100,000 radar-based flight trajectories. We incorporated meteorological conditions resolved along the individual flight trajectories. Computer flight data recorder archives from 2800 flights were statistically analyzed to develop an improved model for estimating changes in aircraft fuel burn with changes in Mach number, throttle setting, and ambient conditions. Using these methods, we estimate that fuel burn and nitrogen oxide production per distance traveled decreased by about 2% and 3%, respectively, with the implementation of reduced vertical separation minimum over the continental U.S. Although our estimate for the benefits of reduced vertical separation minimum is similar to previous studies, we also show that the use of detailed meteorological conditions, and the advancements in aircraft fuel burn estimation described in this paper, are important for analyzing small changes in efficiency related to the implementation of reduced vertical separation minimum. In particular, if these advancements were not incorporated, the estimated benefits of reduced vertical separation minimum for this sample of 100,000 radar-based flight trajectories would be approximately 0%.