READING, PA, USA
N6715U
Mooney M20-C
Shortly after takeoff, the pilot experienced a loss of engine power, and performed a forced landing. Examination of the engine revealed a 1-inch by 6-inch hole, in the engine crankcase adjacent to the number two cylinder, and a fractured number two cylinder connecting rod. Additionally, the crankshaft installed in the engine, required the installation of sludge tubes in the crank-pins. Examination of the crankshaft revealed that the sludge tubes had not been installed. According to a representative of the engine manufacturer, the crankshaft installed in the engine was not approved for use in that model engine. Additionally, the absence of the crankshaft sludge tubes would not allow pressure oil to reach the connecting rod bearings and the connecting rod bearings would only receive splash, vapor and centrifugal force oil. The engine had been operated for about 940 hours since it was overhauled on April 16, 1990 and there were no logbook entries which indicated the crankshaft had been removed or replaced since the overhaul.
On December 11, 1999, about 0815 Eastern Standard Time, a Mooney M20-C, N6715U, was substantially damaged during a forced landing shortly after takeoff from the Reading Regional/Carl A Spaatz Field, Reading, Pennsylvania. The certificated commercial pilot and one passenger were not injured. A second passenger sustained minor injuries. Visual meteorological conditions prevailed and no flight plan had been filed for the personal flight conducted under 14 CFR Part 91. According to the pilot, he performed a preflight inspection of the airplane and noted there were 8 quarts of oil in the engine. After a normal engine run-up, the airplane departed. The airplane had turned crosswind, and was about 1,000 feet agl (above ground level), when the engine began to run "real rough." The pilot then heard a loud noise, which was followed by a total loss of engine power. Additionally, oil was splattered on the windshield, and the pilot observed some smoke in the cockpit. The pilot performed a forced landing to a beach adjacent to a lake. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed a 1-inch by 6-inch hole, in the engine crankcase adjacent to the number two cylinder. The engine was retained for further examination. Examination of the engine performed at Textron Lycoming, Williamsport, Pennsylvania, under the supervision of an FAA inspector revealed a fractured number two cylinder connecting rod. The top and bottom left half of the engine crankcase was broken away in-line with the separated number two cylinder connecting rod. Additionally, the crankshaft, part number 74250, installed in the engine, required the installation of sludge tubes in the crank-pins. Examination of the crankshaft revealed that the sludge tubes had not been installed. The fractured portions of the number two cylinder were forwarded to the Safety Board's Materials Laboratory, Washington, DC, for examination. Examination of the fractured number two connecting rod by a Safety Board metallurgist revealed that the connecting rod fractured through both arms in the areas located at a distance of about 1 1/8 inches from the rod cap joint. Additionally, the bearing surface of the rod contained evidence of heat discoloration. Large portions of both fracture faces had a smooth and silky appearance, and contained crack arrest positions indicative of fatigue cracking. The fatigue origins of both fractures were damaged after the separation, and could not be determined. According to a representative of the engine manufacturer, the engine was certified with a crankshaft, part number 74966, which did not utilize sludge tubes, and only crankshafts which did not require sludge tubes were approved for use in the accident engine. Additionally, the absence of the crankshaft sludge tubes would not allow pressure oil to reach the connecting rod bearings and the connecting rod bearings would only receive splash, vapor, and centrifugal force oil. Textron Lycoming Service Instruction No. SI-1113A, discussed the discontinuance of crankshafts manufactured with sludge tubes. The service instruction stated in part: "This service instruction must not be interpreted to imply that sludge tubes may be omitted during assembly of crankshafts designed to use them; these crankshafts must be assembled with sludge tubes. Engine failure will result if sludge tubes are omitted from crankshafts designed to use them...." Review of the airplane's maintenance records revealed the engine was overhauled by Penn Yan Aero Service, Inc., Penn Yan, New York, on April 16, 1990. There were no logbook entries which indicated the crankshaft had been removed or replaced since the engine was overhauled. The engine had been operated for about 940 hours since the overhaul.
The failure of the number two connecting rod after an improper overhaul by maintenance personnel.
Source: NTSB Aviation Accident Database
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