Maximum lateral flight deviations from the ILS centerline

A procedure is presented for developing spatial confidence intervals about the instrument landing system (i.e., ILS) centerline to determine the likelihood of catastrophic blunder for simultaneous arrivals to closely-spaced parallel runways. The spatial confidence interval is based on the statistics of the maximum lateral deviations (i.e., max(δ_L)) of arriving aircraft position data with respect to the ILS centerline. The procedure was applied at Memphis International Airport (MEM) and Lambert-St. Louis Airport (STL).