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Coastal buffer distances and secondary sonic booms

This presentation describes how secondary sonic booms have influenced our understanding of appropriate coastal buffer distances for supersonic aircraft. The International Civil Aviation Organization issued its Circular 126 in 1975 after the completion of test flights for the supersonic aircraft Concorde but before it began routine operations. This guidance was to prepare everyone for Concorde’s introduction. Particularly Chapter 5 recommended that a supersonic aircraft over the ocean should slow down to subsonic speeds at least 45 nautical miles before reaching the coastline, providing a coastal buffer distance to keep the sonic boom off of land. However, when Concorde began regular transatlantic service, the phenomenon of secondary sonic booms was better appreciated. Air France and British Airways changed their operations to provide much larger coastal buffer distances on the order of 150 nautical miles. Increasing the coastal buffer distances was successful in enabling routine Concorde operations. Implications for the introduction of future civilian supersonic aircraft are described. [Work funded by the FAA through ASCENT Project 57. Any opinions, findings, conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the FAA.]