What was found
STRONG DIRTY SOCK SMELL ON DESCENT THROUGHOUT THE AIRCRAFT. GROUNDED - YES. FOUND OIL IN APU LOAD COMPRESSOR CASE DRAIN REF AMM 49-16-11-200-801 & FIM TASK 05-51- TASK 814. REMOVED AND REPLACED APU. REMOVED AND REPLACED RECIRCULATION AIR FILTERS. REF AMM 21-25-01. ACCOMPLISHED BURNOUT OF APU AND BOTH ENGINE PNEUMATIC DUCTS. REF AMM 21-00-01. NO FURTHER ODORS PRESENT AFTER ACCOMPLISHMENT OF FIM 21-00 TASK 806 REPAIR CONFIRMATION. AIRCRAFT RETURNED TO SERVICE.