What was found
AFTER TAKEOFF FROM COF, THE FLIGHT CREW NOTICED A DROP IN THE HYDRAULIC QUANTITY AND THE OIL LOW LIGHT ILLUMINATED. THE FLIGHT CREW FOLLOWED COMPANY PROCEDURES AND RETURNED TO COF FOR AN UNEVENTFUL LANDING. MAINTENANCE INSPECTED THE AIRCRAFT AND LOCATED A DAMAGED O-RING ON THE LEFT HAND AILERON PACK FILTER BOWL CHIP PLUG. MAINTENANCE REPLACED THE O-RING AND PERFORMED A SUCCESSFUL OPERATIONAL CHECK IN ACCORDANCE WITH THE MAINTENANCE MANUAL. THE AIRCRAFT WAS RETURNED TO SERVICE.