A runway veer-off risk assessment based on frequency model. Part I. probability analysis

This two-part paper presents a comprehensive airport risk assessment methodology for veer-off accidents of aircraft runways. Veer-off is a lateral runway excursion, and it occurs when an aircraft leaves the runway during a movement. The most frequent causes for this type of accidents are inappropriate pilot performance and aircraft condition; while other contribution factors include transversal wind, contamination of the runway, and poor visibility. The consequences of these events involve both damage to the aircrafts and potential health effects on passengers and crew members. Statistical data collected throughout the world by the authors were used as a reference to conduct frequency and risk assessments of veer-offs. The objective of the first part of the paper is to assess the probability of a veer-off accident. To accomplish this objective, a cumulative probability distribution was used to represent the phenomenon. It was found that the exponential curve described by the Poisson distribution could be properly used to describe this type of accident. The results show that the average frequency of a veer-off accident is 1.44 in ten million movements for commercial flights over 30 Mg (ton) and that veer-offs are more frequent to occur during landing than during take-off procedures. The proposed analysis permits to compute the probability of veer-offs at any airport, after considering its specific conditions (e.g. number and type of plane, kind of movement, bearing capacity of the subgrade, etc.).