▁considered ▁the ▁lack ▁of ▁an ▁on board ▁rad ar ▁on ▁the ▁SR . 5 3 ▁and ▁the ▁Av ro ▁ 7 2 0 ▁to ▁have ▁been ▁a ▁vital ▁f law ▁despite ▁it ▁not ▁being ▁a ▁requirement ▁of ▁the ▁specification , ▁leaving ▁the ▁pilot ▁dependent ▁on ▁his ▁own ▁vision ▁and ▁direction ▁being ▁provided ▁by ▁ground - based ▁rad ar ▁control . ▁B ren nan ▁had ▁also ▁been ▁diss atisf ied ▁with ▁the ▁use ▁of ▁the ▁tur bo jet ▁engine ; ▁he ▁believed ▁that ▁a ▁larger ▁jet ▁engine ▁should ▁match ▁the ▁steady ▁su person ic ▁cru ising ▁speed ▁of ▁the ▁aircraft , ▁and ▁that ▁the ▁ro cket ▁motor ▁should ▁be ▁mainly ▁used ▁for ▁high ▁performance ▁clim bs , ▁turns , ▁and ▁rapid ▁acceleration ▁instead . ▁According ly , ▁the ▁SR . 1 7 7 ▁was ▁a ▁much ▁larger ▁and ▁s oph istic ated ▁aircraft ▁that ▁would ▁provide ▁for ▁more ▁range ▁and ▁overall ▁superior ▁performance ▁to ▁the ▁SR . 5 3 . ▁It ▁was ▁s ized ▁to ▁be ▁able ▁to ▁carry ▁a ▁useful ▁air bor ne ▁rad ar , ▁which ▁B ren nan ▁had ▁de emed ▁to ▁be ▁essential ▁for ▁inter ception ▁at ▁the ▁high ▁alt itudes ▁in ▁where ▁the ▁new ▁f ighter ▁was ▁meant ▁to ▁operate . ▁The ▁new , ▁larger ▁aircraft ▁was ▁also ▁to ▁be ▁developed ▁into ▁separate ▁versions ▁for ▁mar itime ▁use ▁by ▁the ▁Royal ▁Navy ▁and ▁for ▁West ▁Germany ▁as ▁well ▁as ▁for ▁the ▁R AF . ▁Sau nd ers - R oe ▁worked ▁on ▁both ▁the ▁SR . 5 3 ▁and