A Summary Index of Risk with Application to Aviation

摘要

The risk for an event is a combination of the severity of outcomes for that event and the likelihood ofoccurrence. When the event is a failure in a mechanical system of a commercial aircraft, then the severity isdefined by classification schemes from the Federal Aviation Administration and The Flight SafetyFoundation. The rate of occurrence of failures in a period of time varies for different aircraft. A graph orfunction representing the severity and rate, generated by (severity, rate) values across mechanicalclassification codes, provides a risk curve or profile. A method for characterizing the severity of the riskcurve is the absolute Lorenz curve- ALC, where the product: severity X rate is accumulated up to eachseverity value. If a benchmark or standard ALC is provided, then a measure of departure such as the Ginicoefficient: area between the standard and specific ALC, describes the degree of risk.In this paper, the absolute Lorenz curve is used to define the overall risk index. The value of the indexdescribes the deviation of the risk curve for a unit (e.g., aircraft, model, operator, manufacturer) from astandard. The calculation of the index value is illustrated with failure data on commercial helicopters.