▁as ▁the ▁Mi G - 2 5 ▁is ▁a ▁much ▁bigger ▁and ▁faster ▁aircraft ▁with ▁a ▁substantial ▁alt itude ▁advantage . ▁His ▁other ▁confirmed ▁kill ▁was ▁an ▁Su - 2 0 ▁on ▁October ▁ 1 7 , ▁ 1 9 8 0 . ▁ ▁In ventory ▁ 1 9 2 0 – 1 9 7 9 ▁ ▁Gallery ▁ ▁References ▁ ▁External ▁links ▁▁ ▁Historical ▁mem orial ▁site ▁for ▁the ▁Imperial ▁Iran ian ▁Air ▁Force ▁ ▁Air ▁force ▁Category : I sl am ic ▁Republic ▁of ▁Iran ▁Air ▁Force ▁Iran ian ▁Air ▁Force ▁Air ▁Force ▁Category : A viation ▁history ▁of ▁Iran <0x0A> </s> ▁A ▁cam less ▁or ▁free - val ve ▁p ist on ▁engine ▁is ▁an ▁engine ▁that ▁has ▁po ppet ▁val ves ▁operated ▁by ▁means ▁of ▁elect romagnet ic , ▁hyd ra ul ic , ▁or ▁p neum atic ▁actu ators ▁instead ▁of ▁conventional ▁c ams . ▁Act u ators ▁can ▁be ▁used ▁to ▁both ▁open ▁and ▁close ▁val ves , ▁or ▁to ▁open ▁val ves ▁closed ▁by ▁spr ings ▁or ▁other ▁means . ▁ ▁Cam sh aft s ▁normally ▁have ▁one ▁lo be ▁per ▁val ve , ▁with ▁a ▁fixed ▁val ve ▁duration ▁and ▁lift . ▁Although ▁many ▁modern ▁engines ▁use ▁cam sh aft ▁ph asing , ▁adjust ing ▁the ▁lift ▁and ▁val ve ▁duration ▁in ▁a ▁working ▁engine ▁is ▁more ▁difficult . ▁Some ▁manufact ur ers ▁use ▁systems ▁with ▁more ▁than ▁one ▁cam ▁lo be , ▁but ▁this ▁is ▁still ▁a ▁comprom ise ▁as ▁only ▁a ▁few ▁profiles