, ▁only ▁the ▁first ▁two ▁were ▁completed . ▁The ▁prototype ▁aircraft ▁( V L 5 1 5 ) ▁first ▁fle w ▁in ▁ 1 9 4 7 . ▁ ▁The ▁use ▁of ▁the ▁Gi ps y ▁Queen ▁engine ▁resulted ▁in ▁disappoint ing ▁performance , ▁and ▁so ▁the ▁A . 4 / 4 5 ▁was ▁not ▁ordered ▁by ▁the ▁R AF . ▁Scottish ▁A viation ▁decided ▁instead ▁to ▁produce ▁a ▁civil ▁version . ▁This ▁was ▁achieved ▁by ▁fitting ▁the ▁two ▁pro tot ypes ▁( V L 5 1 5 ▁and ▁V L 5 1 6 ) ▁with ▁new , ▁more ▁powerful ▁engines ▁as ▁the ▁" P ione er ▁II ". ▁ ▁The ▁prototype ▁P ione er ▁II ▁was ▁the ▁former ▁prototype ▁P ione er ▁I , ▁( V L 5 1 5 ) ▁which ▁was ▁civil ▁registered ▁as ▁G - AK BF . ▁Power ed ▁by ▁a ▁ 5 2 0   hp ▁Al vis ▁Leon ides ▁engine , ▁and ▁first ▁fle w ▁on ▁ 5 ▁May ▁ 1 9 5 0 . ▁The ▁second ▁prototype ▁P ione er ▁I ▁( V L 5 1 6 ) ▁was ▁similarly ▁converted , ▁and ▁civil ▁registered ▁as ▁G - AN A Z .. ▁ ▁The ▁P ione er ▁II ▁demonstrated ▁excellent ▁S TO L ▁performance , ▁and ▁was ▁ordered ▁by ▁the ▁R AF ▁as ▁the ▁P ione er ▁CC . 1 . ▁ ▁Production ▁examples ▁of ▁the ▁P ione er ▁CC . 1 ▁were ▁fitted ▁with ▁full - span ▁controlled ▁leading - edge ▁wing ▁sl ats