4 ▁Height ▁( m ): ▁ 0 . 7 2 ▁ ▁PS Y OP ▁U AV ▁Psych ological ▁operation ▁U AV ▁is ▁an ▁un mann ed ▁hel ic opter ▁developed ▁by ▁Nobel ▁Mor al ▁for ▁military ▁and ▁para - mil it ary ▁operations , ▁and ▁it ▁is ▁directly ▁developed ▁from ▁rem ot ely ▁controlled ▁un mann ed ▁hel ic op ters ▁used ▁in ▁compet itions . ▁The ▁un mann ed ▁hel ic opter ▁has ▁a ▁more ▁powerful ▁engine ▁and ▁was ▁deployed ▁by ▁Chinese ▁military ▁in ▁psych ological ▁war fare ▁operations , ▁as ▁well ▁as ▁aer ial ▁reconna issance ▁mission ▁for ▁post - st rike ▁battle field ▁assess ment . ▁The ▁U AV ▁went ▁into ▁service ▁after ▁the ▁development ▁completed ▁in ▁February ▁ 2 0 0 6 . ▁ ▁See ▁also ▁List ▁of ▁un mann ed ▁aer ial ▁vehicles ▁of ▁the ▁People ' s ▁Republic ▁of ▁China ▁ ▁References ▁ ▁Category : Un mann ed ▁hel ic op ters ▁of ▁China <0x0A> </s> ▁A ▁p neum atic ▁bar rier ▁is ▁a ▁method ▁to ▁contain ▁oil ▁sp ills . ▁It ▁is ▁also ▁called ▁a ▁b ubble ▁cur tain . ▁Air ▁b ub bling ▁through ▁a ▁per for ated ▁pipe ▁causes ▁an ▁up ward ▁water ▁flow ▁that ▁slow s ▁the ▁spread ▁of ▁oil . ▁It ▁can ▁also ▁be ▁used ▁to ▁stop ▁fish ▁from ▁entering ▁poll uted ▁water . ▁A ▁further ▁application ▁of ▁the ▁p neum atic ▁bar rier ▁is ▁to ▁decrease ▁the ▁salt - water ▁exchange ▁in ▁navigation ▁lo cks ▁and ▁prevent ▁salt ▁intr usion ▁in