Specific Risk as an Aviation Safety Metric

摘要

This paper proposes formal definitions for two types of specific risk, using the terminology “Actual Specific Risk”(ASR) and “Potential Specific Risk” (PSR). The term “Actual Specific Risk” applies when one or more riskparameters differ from airplane to airplane, and the values of those parameters are identifiable for those airplanes.As an example, risk may increase with airplane age. This is ASR since airplane age is a tracked and identifiableparameter. The term “Potential Specific Risk” applies when a risk contributor is not known to exist, but is assumedto exist. As an example, risk will increase if an airplane suffers an undetected (latent) failure of a backup enginetemperature signal. This is PSR since latent failures, by definition, are undetectable. It will not be known whichairplanes will face this higher risk.This paper also reviews existing regulatory and industry guidance related to specific risk scenarios, and fits thisguidance within the ASR – PSR framework. It is hoped that the proposed ASR – PSR framework will facilitatecommunication and assist those in the aviation community who are working to harmonize specific risk practices.