What was found
ON DESCENT THROUGH 15000 FA FRONT AND BACK OF THE PLANE SMELLED A STRONG DIRTY SOCK SMELL THAT PERSISTED UNTIL LANDING AND SLOWLY DISSIPATED AFTER, THEY SMELLED A CHEMICAL SMELL AS WELL AFTER OPENING CABIN. PER P TRAK RESULT, DEEMED APU CHANGE REGUIRED. REPLACED APU. (LP 8547444, 1783569 - AIRCRAFT WAS GROUNDED)