What was found
(CAN) ON TAKEOFF ENGINE AUTO-FEATHERED, AND LOAD OF RETARDANT WAS JETTISONED. AIRCRAFT RETURNEDTO AIRPORT WITH THREE ENGINES OPERATIVE. INSPECTIONS COMPLETED - I.E. NOSE CASE REMOVED AND CHIPPED TEETH FOUND ON COUNTER BALANCE DRIVE GEARS AND THE SUPPORT BEARING WAS FOUND CRACKED. ENGINE WAS RE-ASSEMBLED FOR THREE ENGINE FERRY. NOSE CASE WAS AGAIN REMOVED TO DETERMINE EXTENT OF DAMAGE. DAMAGE FOUND INDICATED A MASTER ROD BEARING FAILURE WHICH RESULTED IN THE MASTER ROD COMING LOOSE AND DAMAGING THE REAR CYLINDERS. SERVICEABLE ENGINE INSTALLED AND AIRCRAFT DISPATCHED FOR FIRE FIGHTING.