▁concern ▁that ▁the ▁contra - rot ating ▁prop ellers ▁would ▁not ▁be ▁available ▁on ▁time , ▁the ▁XP - 6 0 B ▁was ▁modified ▁to ▁take ▁the ▁R - 2 8 0 0 - 1 0 ▁engine ▁driving ▁a ▁four - bl aded ▁prop eller . ▁This ▁modification ▁was ▁red es ign ated ▁XP - 6 0 E . ▁ ▁On ▁ 2 7 ▁January ▁ 1 9 4 3 , ▁the ▁XP - 6 0 C ▁fle w ▁for ▁the ▁first ▁time , ▁power ed ▁by ▁an ▁R - 2 8 0 0 - 5 3 ▁engine ▁with ▁contra - rot ating ▁prop ellers . ▁The ▁aircraft ' s ▁flying ▁characteristics ▁were ▁found ▁to ▁be ▁generally ▁satisf actory . ▁The ▁first ▁flight ▁of ▁the ▁XP - 6 0 E ▁with ▁the ▁four - bl aded ▁prop eller ▁was ▁delayed ▁until ▁ 2 6 ▁May ▁ 1 9 4 3 ▁after ▁it ▁was ▁found ▁that ▁due ▁to ▁its ▁l ighter ▁weight , ▁the ▁engine ▁installation ▁had ▁to ▁be ▁moved ▁ 1 0 ▁inches ▁forward ▁compared ▁to ▁the ▁XP - 6 0 C . ▁ ▁In ▁April ▁ 1 9 4 3 , ▁the ▁US ▁Army ▁Air ▁Forces ▁decided ▁to ▁conduct ▁an ▁evaluation ▁of ▁the ▁various ▁f ighter ▁aircraft ▁in ▁development ▁and ▁use , ▁in ▁order ▁to ▁eliminate ▁the ▁least ▁des irable ▁models . ▁Curt iss ▁was ▁requested ▁to ▁have ▁the ▁XP - 6 0 E ▁particip ate . ▁As ▁the ▁XP - 6 0 E ▁was ▁not ▁available , ▁the ▁company ▁hurried ly