Modeling the spatial distribution of aircraft on visual flight rules

Introduction T Note summarizes an FAA-supported pilot program to develop models which estimate the average and peak instantaneous aircount (IAC) of aircraft flying on visual flight rules (VFR). The IAC are distributed spatially, similar to a checkerboard effect, over the cross-sectional area of each state in the continental United States (CONUS) for a typical VFR day in 1980. VFR aircraft are primarily general aviation (GA) aircraft and they constitute the bulk of all in-flight aircraft (at least 85%). Knowledge of aircraft densities helps to estimate the size of replacements for the enroute air traffic control computers. Peak density is especially important to the design of aircraft collision avoidance devices. An earlier model estimated the average IAC of VFR aircraft over each Air Route Traffic Control Center, of which there are 20 covering the CONUS.' The new models described here will be referred to collectively as the VFR spatial model. Without this model, it would be necessary to process radar data on all in-flight VFR aircraft in order to obtain their peak and average spatial distribution. This approach is not only enormously costly and time-consuming, but it would also require the solution of several formidable technical problems.