 Approximately one hour later , Hiryū 's second attack wave , consisting of ten B5Ns and six escorting A6Ms , arrived over the Yorktown ; the repair efforts had been so effective that the Japanese pilots assumed that Yorktown must be a different , undamaged carrier . They attacked , crippling Yorktown with two torpedoes ; she lost all power and developed a 23 @-@ degree list to port . Five torpedo bombers and two fighters were shot down in this attack . 
