"ESDU 08005 is an example of risk analysis applied the landing distance of an aircraft. The example uses a set of in-service landing distance measurements to compare with the available landing distance and with the operational landing distance factors in both dry and wet conditions. ESDU 08005 is one of a series of examples that compliment a parent Item@ ESDU 08003@ that introduces the treatment of risk within the context of the performance of commercial air transport. The concept of risk is introduced in relation to what is considered safe by the aircraft operators@ by the official bodies responsible for regulating air transport and implicitly by the users of the service. Risk is classified in terms of the severity and consequences of an event@ together with the probability of the occurrence of that event. The term ""unit of risk"" is introduced to quantify general risk and is seen as either events-based or time-based. "