Considering the differences of safety features between unmanned aircraft system(UAS) and manned aircraft

the ground impact was recognized as the critical risk condition by means of event tree analysis. Based on definition of equivalent level of safety

safety evaluation model for unmanned aircraft system was established by consideration of kinetic energy

configuration and flight environment factors. Target levels of safety evaluation approaches based on different UAS classes operating in different scenarios and Chinese population density were discussed. Results indicated that quantitative requirement for UAS operating in different scenarios may range between 4 or 5 orders of magnitude. On this basis

risk evaluation matrix of UAS operation based on ground impact condition was proposed

providing an effective approach to risk evaluation matrix for operations of UAS.