3 1 ▁October ▁ 1 9 4 1 , ▁a ▁contract ▁for ▁ 1 , 9 0 0 ▁P - 6 0 A ▁f igh ters ▁using ▁the ▁All ison ▁engine , ▁was ▁awarded . ▁ ▁Oper ational ▁history ▁In ▁the ▁meant ime , ▁flight ▁tests ▁of ▁the ▁XP - 6 0 ▁prototype ▁were ▁not ▁progress ing ▁smooth ly . ▁In ▁addition ▁to ▁landing ▁g ear ▁problems , ▁expected ▁top ▁speed ▁was ▁not ▁being ▁met ▁due ▁to ▁short com ings ▁in ▁the ▁l amin ar - flow ▁wing ▁surface ▁finish , ▁relatively ▁high ▁radi ator ▁drag ▁( comp ared ▁to ▁the ▁North ▁American ▁P - 5 1 ▁Must ang , ▁which ▁was ▁then ▁flying ), ▁and ▁less ▁than ▁specified ▁engine ▁output ▁performance . ▁Con sequently , ▁work ▁on ▁the ▁P - 6 0 A ▁was ▁stopped ▁on ▁ 2 0 ▁December ▁ 1 9 4 1 , ▁when ▁the ▁USA AC ▁recommended ▁that ▁Curt iss ▁concent rate ▁on ▁lic ence ▁production ▁of ▁Republic ▁P - 4 7 ▁Th under bol ts . ▁ ▁On ▁ 2 ▁January ▁ 1 9 4 2 , ▁the ▁order ▁was ▁changed ▁to ▁produce ▁one ▁XP - 6 0 A ▁with ▁the ▁All ison ▁V - 1 7 1 0 - 7 5 ▁engine ▁and ▁a ▁General ▁Electric ▁B - 1 4 ▁tur bo - super char ger , ▁one ▁XP - 6 0 B ▁with ▁the ▁All ison ▁V - 1 7 1 0 - 7 5 ▁engine ▁and ▁a ▁Wright ▁SU - 5 0 4 -