What was found
IND - FLT 1528 - AFTER TAKEOFF, THE PASSENGER CABIN HAD A STRONG ODOR COMING FROM THE AIR CONDITIONING PACKS. THE SMOKE DETECTORS IN THE LAVATORIES CAME ON BUT THERE WAS NO VISIBLE SMOKE. THE CREW DECIDED TO RETURN TO THE FIELD. THE AIRCRAFT LANDED WITHOUT INCIDENT. MAINTENANCE PLACED THE PAU AND MEL, REPLACED THE WATER SEPARATOR COALESCER BAGS. RAN BOTH ENGINES WITH PACKS OPERATING, ALL CHECKED NORMAL. (M)