▁pro tot ypes ▁were ▁ordered ▁built ▁in ▁France ▁by ▁the ▁Far man ▁Brothers ▁and ▁four ▁pre - production ▁pro tot ypes ▁by ▁the ▁He inkel ' s ▁He inkel - N ord ▁headquarters ▁at ▁its ▁Rost ock - Mar iene he ▁( today ' s ▁Rost ock - Sch mar l ) ▁facility . ▁Far man ▁at ▁S ures nes , ▁began ▁their ▁prototype ▁development . ▁ ▁Work ▁on ▁the ▁requested ▁half - do zen ▁He ▁ 2 7 4 ▁prototype ▁air frames ▁was ▁lever aged ▁off ▁He inkel ▁aircraft ▁production ▁at ▁A IA ▁B reg uet , ▁Toul ouse ▁where ▁French ▁fact ories ▁produced ▁He inkel ▁components ▁and ▁J unk ers ▁av iation ▁engines . ▁French ▁production ▁facilities ▁at ▁Toul ouse ▁for ▁He inkel ▁aircraft ▁were ▁sever ely ▁dam aged ▁by ▁Royal ▁Air ▁Force ▁( RA F ) ▁air ▁ra ids ▁on ▁the ▁night ▁of ▁ 5 / 6 ▁March ▁ 1 9 4 4 ▁and ▁again ▁by ▁the ▁US ▁E ighth ▁Air ▁Force ▁on ▁ 2 5 ▁June ▁ 1 9 4 4 . ▁This ▁fr ustr ated ▁completion ▁of ▁the ▁French ▁pro tot ypes , ▁as ▁the ▁design ▁work ▁in ▁Germany ▁and ▁Austria ▁had ▁begun ▁by ▁February ▁ 1 9 4 3 , ▁on ▁what ▁had ▁emer ged ▁as ▁the ▁He inkel ▁entry ▁in ▁the ▁trans - At l antic ▁Amer ik ab om ber ▁strateg ic ▁heavy ▁bom ber ▁design ▁competition , ▁the ▁He inkel ▁He ▁ 2 7 7 . ▁While ▁the ▁R LM - design ated ▁