▁gun fire , ▁could ▁leak ▁fuel ▁rapidly . ▁This ▁would ▁not ▁only ▁reduce ▁the ▁aircraft ' s ▁effective ▁range , ▁but ▁was ▁also ▁a ▁significant ▁fire ▁ha z ard . ▁Dam aged ▁fuel ▁t anks ▁could ▁also ▁ru pt ure , ▁destroy ing ▁the ▁air frame ▁or ▁crit ically ▁affect ing ▁flight ▁characteristics . ▁ ▁It ▁was ▁realized ▁that , ▁because ▁of ▁weight ▁limitations , ▁it ▁was ▁not ▁practical ▁to ▁simply ▁add ▁arm or ▁plate ▁to ▁aircraft ▁fuel ▁t anks ; ▁a ▁method ▁of ▁stopping ▁fuel ▁le aking ▁from ▁dam aged ▁t anks ▁was ▁necessary . ▁ ▁Early ▁attempts ▁at ▁protect ing ▁fuel ▁t anks ▁consisted ▁of ▁using ▁metal ▁t anks , ▁covered ▁inside ▁or ▁outside ▁by ▁a ▁material ▁that ▁expanded ▁after ▁being ▁pier ced . ▁Research ▁revealed ▁that ▁the ▁exit ▁of ▁the ▁project ile , ▁rather ▁than ▁the ▁entry , ▁was ▁the ▁greater ▁problem , ▁as ▁it ▁often ▁t umbled , ▁thus ▁creating ▁a ▁large ▁exit ▁hole . ▁Among ▁the ▁earliest ▁versions ▁of ▁these ▁types ▁of ▁t anks ▁were ▁those ▁manufact ured ▁in ▁the ▁UK ▁at ▁Port sm outh ▁air port ▁by ▁Fire proof ▁T anks ▁Ltd . ▁These ▁t anks ▁were ▁first ▁installed ▁in ▁the ▁F aire y ▁Battle ▁light ▁bom ber ▁with ▁other ▁versions ▁installed ▁in ▁Super marine ▁Sp it fire ▁and ▁Haw ker ▁H urr icane ▁f igh ters ▁and ▁larger ▁aircraft ▁such ▁as ▁the ▁Av ro ▁Lanc aster ▁heavy ▁bom ber . ▁The ▁Hend erson ▁Saf ety ▁T ank ▁company ▁provided ▁crash - proof ▁self - se aling