A Baseline of Turbulence Impacts on Commercial Air Carrier Operations

Previous work by Northwest Research Associates showed that in-flight encounters with atmospheric turbulence accounted for 62 percent of all U.S. air carrier accidents when weather was cited as a factor. The most recent data published by the Federal Aviation Administration (FAA) places this figure as high as 79 percent. However, official accident reports indicate that on average there are about 10 turbulence upsets per year, whereas knowledgeable stakeholders place the actual number much higher. Some sources place the costs to the airline industry from encounters with turbulence at $100M annually, but others allocate nearly $90M of this figure to accidents involving general aviation aircraft. These estimates of the number of events and the economic consequences from turbulence encounters point out both the potential magnitude of this problem as well as the uncertainties that impede the development of accurate business models that can support decisions on investments in turbulence detection and warning technologies.

This paper presents the results of a study to develop a baseline that describes the “as-is” state of the problems faced by U.S. commercial air carriers from encounters with moderate or greater atmospheric turbulence. This baseline is intended to help develop requirements for new airborne turbulence detection and warning systems, and to help ensure that such technologies can be developed as efficiently and cost-effectively as possible. The baseline characterizes factors such as the number of turbulence encounters experienced by commercial aircraft, how often they occur, where and when they occur, meteorological conditions associated with these events, and consequences for aircraft occupants and the airlines. As part of this project we have developed a relational database that contains information on all official NTSB/FAA reports of accidents and incidents involving encounters with turbulence by Part 121 scheduled operations during the 17 year period 1983–1999. We have also surveyed a number of system stakeholders who are knowledgeable about the turbulence problem to help us characterize the accuracy and completeness of our baseline. The key conclusions and recommendations from the turbulence baseline study will be presented in this paper.