Analysis of Turbulence Encounters and Impacts in the National Airspace System

This paper describes results of analysis of turbulence encounters and impacts in the National Airspace System (NAS). It introduces an analytical framework for processing historical weather and flight track data and quantifying the impact of turbulence on Air Traffic Control (ATC) operations. Six months of flight track and turbulence intensity data spanning winter and summer seasons were processed to develop a repository of turbulence encounters and analyze pilots’ responses to these encounters.

Pilot maneuvers, including altitude changes and deviations, were analyzed during the cruise phase of flight. The results showed that the vast majority of turbulence encounters in the NAS occur at the lowest turbulence intensity levels but encounters with higher intensity values are also quite common in today’s NAS, in some cases exceeding hundreds of minutes a day.

Pilots’ responses, including altitude changes and deviations, were analyzed to estimate the impacts of turbulence on flight operations and ATC workload. Specifically, we considered not only the altitude changes associated with the actual turbulence encounters but also secondary altitude changes triggered by turbulence encounters located within a spatiotemporal vicinity (i.e. flight changing altitude due to turbulence encounters may trigger altitude changes for nearby flights). The analyses showed that turbulence can be attributed to a significant portion (i.e. between 15% and 65%) of all altitude changes occurring on a daily basis in the NAS.