What was found
AIRCRAFT RETURNED TO PLATFORM DUE TO SMOKE DETECTORS ALARMS OF AFT LAVATORIES WERE ACTIVATED BEFORE TAKE-OFF. DURING MAINTENANCE INSPECTION, IT WAS DETECTED OIL CONTAMINATION IN DUCTS OF COOLING TURBINE, WATER SEPARATOR AND PRIMARY AND SECONDARY HEAT EXCHANGERS OF LT AIR CONDITIONED SYSTEM. TURBINE COOLING, WATER SEPARATOR AND HEAT EXCHANGERS WERE REPLACED IAW M/M 21-51-01, 21-20-02, 21-51-02 AND 21-51-03 RESPECTIVELY, TESTED ALL CORRECT IAW M/M 21-00-00. AS A PRECAUTIONARY ACTION, LT SMOKE DETECTOR WAS REPLACED IAW AVAS MRB 26-14-00-01 TESTED ALL CORRECT.