What was found
(CAN) ENGINE OIL WAS DETECTED COMING THROUGH THE UPPER AFT RT INTERIOR PANEL AND GRAVITY LEAKAGE DOWN TO THE AIRCRAFT FLOOR. CONDITION ONLY EXISTED UNDER STEEP RT TURNS OF THE HELICOPTER. A/C RETURNED TO BASE AND UPON INVESTIGATION OF THIS SITUATION IT WAS DETERMINED THAT THE RUBBER OIL SEAL FROM THE ENGINE OIL FILLER SUPPORT TO ENGINE OIL TANK DEVELOPED A HOLE UNDER THE CLAMP AT THE TANK LOCATION. OIL TANK IS LOCATED AT THE UPPER RT (AFT FACING FORWARD) OF THE HELICOPTER. THAT EXPLAINED THE AREA OF LEAKAGE IN QUESTION. NEW SEAL WAS INSTALLED ANDTHE AIRCRAFT WAS GROUND RUN AND FLOWN WITH NO FURTHER LEAKAGE. DEFECT ENTRY WAS COMPLETED AS PER COMPANY MCM AND UNDER CARS 605.06 AND RECTIFIED PRIOR TO NEXT FLIGHT.