CEN10LA482

The pilot reported that the engine experienced an abrupt loss of engine power while turning onto the final approach leg of the traffic pattern. His attempts to restore engine power were unsuccessful and he elected to ditch the airplane near a ferry dock. The airplane came to rest in about 22 feet of water, approximately 50 yards from the shoreline. A postaccident examination and operational test run of the engine did not reveal any anomalies consistent with a complete loss of engine power. The examination did reveal a section of missing material from the edge of the No. 6 cylinder exhaust valve and irregular combustion deposits on the face of the valve. Both signatures are consistent with an exhaust leak and a corresponding partial loss of engine power. During the test run, the engine started normally and without hesitation. The engine was unable to produce rated power due to an exhaust leak.

On August 13, 2010, about 1142 eastern daylight time, a Cessna T210M, N14AW, piloted by a private pilot, was substantially damaged during a forced landing following a loss of engine power. The airplane was on approach to Runway 3 at Put-in-Bay Airport (3W2), Put-in-Bay, Ohio, when the engine lost power. The pilot subsequently ditched into Lake Erie about 1/4 mile southwest of the runway, near the Miller Ferry dock. The personal flight was being conducted under 14 Code of Federal Regulations Part 91 without a flight plan. Visual meteorological conditions prevailed. The pilot and two passengers successfully evacuated the airplane without injury. The third passenger reported minor injuries. The flight departed from Canton-Plymouth-Mettetal Airport (1D2), Plymouth, Michigan, about 1105. The intended destination was 3W2. The pilot reported that he had initially entered the traffic pattern for runway 3 at 1D2. However, due to conflicts with other traffic, he elected to extend the base leg and continue in the pattern in order let the other traffic get organized. The remainder of the second traffic pattern for runway 3 was "uneventful" until he the engine "went silent" as he rolled out on final approach. The pilot noted that the engine lost power without "missing, stumbling or hesitating" and there seemed to be no signs of a mechanical problem. The propeller continued to windmill. His attempts to restore engine power were unsuccessful. The pilot subsequently ditched the airplane near a ferry dock on the south end of South Bass Island. The pilot and three passengers were rescued by a ferry boat. The airplane came to rest in about 22 feet of water, approximately 50 yards from the shoreline. It was recovered about 2000 that evening. The airframe had sustained substantial damage to the fuselage and empennage. The accident engine was a Teledyne Continental Motors TSIO-520-R9, serial number 294483-R. It was manufactured in July 2003 and installed on the accident airplane in April 2004. The recording tachometer indicated 4,674.9 hours at that time. According to the engine log, a "top overhaul" was completed on December 14, 2008, at 5,720.0 hours, which included overhaul of the cylinders and installation of new after market (non-OEM) intake and exhaust valves. An annual inspection had been completed on November 12, 2009, at 5,864.0 hours. The most recent maintenance consisted of an oil change and was completed on April 12, 2010. The engine time associated with that oil change was 5,910.0 hours. The pilot's logbook indicated a total flight time of 14.0 hours in the accident airplane between April 13, 2010, and the day of the accident. A post accident examination and operational test run of the engine did not reveal any anomalies consistent with a complete loss of engine power. A borescope examination of the #6 cylinder noted a section of missing material from the edge of the exhaust valve. The exhaust valve face exhibited an irregular combustion deposit patternand the exterior of the cylinder was discolored in the area of the exhaust valve. These conditions are consistent with a leak at the exhaust valve during operation. Neither magneto produced a spark when operated on a test bench. Further examination revealed corroded carbon brush and contact point components on both units consistent with exposure to water. No other anomalies were observed. The oil filter element was removed; no contamination was observed. A new oil filter and operational magnetos were installed on the engine for a test run. The engine was not disassembled prior to the test run. The engine started normally and without hesitation. At full throttle, the engine operated at 2,250 rpm and 36.2 inches of mercury manifold pressure. The engine is rated for 2,700 rpm at 36.5 inches manifold pressure. A leak at the fuel control unit was observed during the test run. On disassembly, the o-rings sealing the unit did not return to their normal shape, but remained deformed. No other anomalies were observed with respect to the fuel control unit. According to the manufacturer, the component label appeared to pre-date the engine and the safety wire lead seal appeared consistent with a prior field overhaul of the unit. The pilot stated that the original fuel control unit had been replaced about two years prior to the accident. He did not recall noticing any sign of a fuel leak during operation of the airplane. The pilot reported he departed with approximately 16 gallons of fuel in both the left and right main tanks. Average fuel consumption for the accident airplane was about 15.2 gallons per hour, according to the pilot.