. ▁Mark ..., ▁F . ▁Mark .. ▁and ▁H . F ▁Mark ▁indicated ▁whether ▁the ▁engines ▁fitted ▁were ▁su ited ▁for ▁low , ▁medium ▁or ▁high ▁alt itude . ▁The ▁use ▁of ▁these ▁prefix es ▁did ▁not ▁change ▁according ▁to ▁the ▁wings , ▁which ▁could ▁be ▁fitted ▁with ▁" cli pped " ▁tips , ▁reducing ▁the ▁wings pan ▁to ▁about ▁ 3 2   ft ▁ 6 ▁in ▁( 9 . 9 ▁m ) ▁( this ▁could ▁vary ▁slightly ), ▁or ▁the ▁" point ed " ▁tips ▁which ▁increased ▁the ▁wings pan ▁to ▁ 4 0   ft ▁ 2 ▁in ▁( 1 2 . 2 9 ▁m ). ▁ ▁The ▁original ▁Mer lin ▁and ▁Griff on ▁engine ▁designs ▁used ▁single - stage ▁super charg ers . ▁For ▁engines ▁equ ipped ▁with ▁a ▁single - stage ▁super char ger ▁the ▁air ▁being ▁forced ▁through ▁the ▁super char ger ▁air ▁int ake ▁was ▁com pressed ▁by ▁the ▁super char ger ' s ▁imp eller . ▁In ▁the ▁case ▁of ▁the ▁Mer lin ▁II / III , ▁XII ▁and ▁ 4 0 ▁series ▁as ▁the ▁air ▁was ▁being ▁com pressed ▁it ▁was ▁mixed ▁with ▁fuel ▁which ▁was ▁fed ▁through ▁an ▁SU ▁car b ure tt or ▁before ▁being ▁fed ▁into ▁the ▁engine ' s ▁cyl ind ers . ▁The ▁Mer lin ▁III ▁produced ▁ 1 , 0 3 0 ▁h p ▁( 7 7 0   k W ) ▁at ▁+ 6 ¼ lb / in ² ▁( 4 3 ▁k Pa ) ▁of ▁"