A Convair CV-440, operated by Dodita Air Cargo, departed San Juan on an early morning VFR flight to Sint Maarten, carrying a cargo of perishable food. After leveling off at 5,500 feet msl, the crew noticed that the right engine cylinder head temperature and oil temperature was about 10 degrees above normal. Shortly after, both pilots noticed a sharp decrease in the right engine brake mean effective pressure followed by vibration in the engine. A fire started around the front lower cylinders. The captain feathered the right engine propeller, pulled the Emergency handle and fired the main and reserve fire extinguishing bottles. The fire however had extended to the whole front of the engine cylinders. The burning engine fell off the plane’s wing and the crew prepared for a ditching. The co-pilot handed a life jacket to the pilot and then put his on. The pilot placed his life preserver to the side and did not put it on. While descending the co-pilot opened his side window, but the pilot did not. At 300 feet, and still on a westerly heading, the co-pilot recalled that the airplane’s indicated airspeed was around 135 to 140 knots, and the right wing leading edge was on fire and was melting. After hitting the water surface the cockpit section also contacted the water and sank for a short time. The cockpit surfaced once and the water was above both pilot’s shoulders. One of the wings and the cockpit separated and the airplane sank into 1,000 feet of water. The co-pilot was rescued by a Coast Guard helicopter. The captain was declared missing and had not been found after a full day of searching. PROBABLE CAUSE: “The in-flight fire on the number two engine, for undetermined reasons.”