The availability of unmanned air vehicles: A post-case study

An Unmanned Air Vehicle (UAV) is an unmanned, remotely controlled, small air vehicle. It has an important role in anti-surface warfare. This implies over-the-horizon detection, classification, targeting and battle damage assessment. To perform these tasks several UAVs are needed to assist or interchange with each other. An important problem is to determine how many UAVs are needed in this respect. The answer depends on the characteristics of the UAV and its mission. The UAV availability problem is very complex and the usual method to solve such a problem is simulation. A disadvantage of simulation is that it can be very time-consuming. Hence it is not very suitable for sensitivity analysis. Moreover, since simulation gives mere approximations and is not very generic, theoretical insights are hardly gained. In this paper we show how such a complex problem can still be tackled analytically by using a basic model from reliability theory, viz., a 1-out-of-n system with cold standby, ample repair facility and general life time and repair distributions.