Instantaneous availability models of URAS basic combat unit during mission

Instantaneous availability models of Unmanned Reconnaissance Aircraft Systems (URAS) basic combat unit (BCU) are studied based on reconnaissance operation missions. The configuration and typical reconnaissance mission of URAS BCU are analyzed at first. Mission demand functions are established using Fourier series expansion, which makes discrete mission demands be transformed to continuous´. Moreover, Instantaneous availability models of URAS BCU are proposed considering dynamic mission demands. Then, non-stationary spares demands based on mission are analyzed and time-varying expected backorder (EBO) models of two-echelon single-indenture repairable item are established taking limited repair equipments into account. Solution algorithm of time-varying LRU expected number in non-stationary multi-class finite-server queueing system is presented. Finally, an example is provided to verify the validities of the models.