Aiming at safety requirement for unmanned aircraft system(UAS)

it was initially demonstrated that current safety assessment process and methodology based on regulation and reference for manned aircraft were limited for UAS because of its unique features.In views of this principle

some improvements for UAS safety assessment were proposed:(1) take consideration of UAS including the unmanned aerial vehicle and assured equipments

and enlarge the scope of safety assessment during functional hazard analysis at system level;(2) take consideration of the feature that pilot and unmanned aircraft are physically separated

and reclassify and redefine the serious level of UAS failures.(3) consider that the quality of take-off has a huge impact on system

and the safety analysis must be conducted for two key events-‘air collision’ and ‘ground impact’.The result indicates that the above improvements are in accordance with features of UAV and ensures safety through establishing targeted safety level.