ier ), ▁with ▁a ▁Nap ier ▁Sab re ▁engine , ▁and ▁the ▁Type ▁R ▁( for ▁Roll s - Ro y ce ), ▁equ ipped ▁with ▁a ▁Roll s - Ro y ce ▁V ulture ▁power plant . ▁Haw ker ▁presented ▁an ▁early ▁draft ▁of ▁its ▁ideas ▁to ▁the ▁Air ▁Ministry ▁which ▁ad vised ▁that ▁a ▁specification ▁was ▁in ▁the ▁off ing ▁for ▁such ▁a ▁f ighter . ▁The ▁specification ▁was ▁released ▁by ▁the ▁min istry ▁as ▁Spec ification ▁F . 1 8 / 3 7 ▁after ▁further ▁prompt ing ▁from ▁Haw ker . ▁The ▁specification ▁called ▁for ▁a ▁single - se at ▁f ighter ▁armed ▁with ▁twelve ▁ 0 . 3 0 3   in ▁( 7 . 7   mm ) ▁machine ▁guns , ▁a ▁maximum ▁speed ▁of ▁ 4 0 0   m ph ▁( 6 4 4   km / h ) ▁at ▁ 1 5 , 0 0 0   ft ▁( 4 , 6 0 0   m ) ▁and ▁a ▁service ▁ce iling ▁of ▁ 3 5 , 0 0 0   ft ▁( 1 0 , 7 0 0   m ) ▁were ▁required . ▁Two ▁pro tot ypes ▁of ▁both ▁the ▁Type ▁N ▁and ▁R ▁were ▁ordered ▁on ▁ 3 ▁March ▁ 1 9 3 8 . ▁ ▁Techn ical ▁description ▁Both ▁pro tot ypes ▁were ▁very ▁similar ▁to ▁the ▁H urr icane ▁in ▁general ▁appearance , ▁and ▁shared ▁some ▁of ▁its ▁construction ▁techniques . ▁The ▁front ▁fus el age ▁used ▁the ▁same ▁sw