NTSB Factual Report

On June 14, 2001, about 1037 eastern daylight time, a Cessna 210L, N2117S, registered to Flyte Air Corporation, experienced a loss of engine power and was ditched near Key West, Florida. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed for the 14 CFR Part 91 personal flight. The airplane was substantially damaged and there were no reported injuries for the commercial-rated pilot or three passengers; one passenger sustained minor injuries. The flight originated about 1026 from the Key West International Airport, Key West, Florida.

The pilot stated that she performed a preflight inspection of the airplane; no discrepancies were noted and the oil capacity was 9 quarts. She did not report any discrepancies associated with the engine either during engine start, taxi, or during the engine run-up before departure, and the passengers were briefed about the use of life jackets and the aircraft's doors before the flight departed. The flight was cleared for takeoff and she later reported that the engine ran normal through the first power reduction and up to 1,500 feet mean sea level. She stated that the flight was cleared to an intersection and shortly after, she heard a loud sound and the cylinder head temperature, exhaust gas temperature, and rpm indications immediately went from normal to zero. The propeller continued to rotate but the oil pressure was zero. She turned towards the airport, declared "mayday", and established best glide airspeed. The main doors were opened in preparation for the ditching and she advised the passengers to brace. The airplane was ditched and all occupants escaped and were picked up by a nearby boat.

The airplane was recovered and the engine was examined by NTSB, FAA, and a representative of the engine manufacturer. The propeller/crankshaft assembly could be rotated by hand though not through 360 degrees; binding was noted and there was no continuity to the accessory case. The oil sump was drained and found to contain oil and salt water; a sufficient quantity of oil was recovered from the engine. Following removal of the oil sump, pieces of metal were found in the bottom of the sump (see photographs 2 and 3); the pieces were retained for further examination. The oil filter was found safety wired and after removal and disassembly; the filter element was found to contain non-ferrous and ferrous material (see photographs 4 and 5). Examination of the oil pump housing and gears revealed no damage. Torque check of all thru-bolts was accomplished which revealed that all but Nos. 2 top, 3 bottom and top, and 6 bottom and top were greater than 640 inch pounds. Additionally, a connecting rod bolt for the No. 2 cylinder connecting rod was fractured near the bolt head; the broken piece was found embedded in the interior portion of the crankcase near the cylinder opening. The nut of the other connecting rod bolt of the No. 2 cylinder connecting rod was chiseled off to allow separation of both crankcase halves. Separation of both crankcase halves revealed that the crankshaft was fractured at crankshaft cheek No. 3 (see photograph 6); the aft portion of the fractured crankshaft was misaligned with the longitudinal axis of the engine. There was no bearing in the No. 2 main bearing position, and the No. 1 main bearing half in the right crankcase was shifted aft approximately 3/16 inch; a grove was noted in the No. 1 main bearing saddle of the left crankcase half indicating aft movement of the bearing. Both crankcase halves, the two pieces of the crankshaft, the No. 2 cylinder connecting rod and fractured bolt, and the pieces of metal found in the oil sump were retained for further examination by the National Transportation Safety Board (NTSB), Materials Laboratory, located in Washington, DC.

According to the NTSB Materials Laboratory Factual Report, the fractured connecting rod bolt of the No. 2 cylinder contained features consistent with a bending shear separation. The pieces of metal found in the oil sump were determined to be the No. 2 main bearing and were mostly the steel backing with very little of the bearing material remaining. The undamaged fracture features of the bearing were consistent with overstress separation. With respect to the crankshaft halves, the report states in part, "...all of the cylinder mounting surfaces were discolored with brown to black deposits and contained various amount of wear and fretting damage." The report also states that, "Both types of deposits were consistent with corrosion and fretting products from iron and aluminum alloys." Additionally, "Polishing was apparent around all of the through bolt holes particularly on the left side at the bolts for the # 2 main bearing (#2 cylinder) where a slight lip was felt at the edge of the polished region. The #2 main bearing through bolts serve as two forward attachments for the #2 cylinder and two aft attachments for the #3 cylinder." The mating case surfaces of the No. 1 main bearing boss exhibited light fretting; light polishing was evident on the mating faces of the No. 2 main bearing boss, and also on the mating faces of the Nos. 1 and 2 cam bearing bosses. The saddle area of the No. 2 main bearing was reported to be "...severely damaged with large rolled edges formed at the forward and rear edges...." With respect to the crankshaft, the fracture surface of the forward part of the fractured pieces exhibited fracture features typical of fatigue progression. The report further states that the fatigue, "initiated at multiple locations on the surface along a 0.2 inch length of the journal radius...." A copy of the report is an attachment to this report.

Review of the maintenance records revealed that the engine was rebuilt by Teledyne Continental Motors, on August 23, 1988, and installed in the airplane on October 1, 1988. An entry dated November 25, 1994, indicates that all cylinders were installed on the engine after being overhauled; the engine had accumulated a total time of approximately 986 hours at that time since major overhaul. Between October 1, 1988, and November 25, 1994, oil samples for analysis were taken 10 times; the oil analysis reports were not located in the maintenance records and were not available from the facility that performed the analysis. A statement from the insurance adjuster detailing his search for the oil analysis reports and from the facility that performed the oil analysis are attachments to this report. There was no record of the repair and/or replacement of the Nos. 2 or 3 cylinders between the time the overhauled cylinders were installed in 1994, and the last entry in the logbook which was dated March 6, 2001. At the time of the accident, the engine had accumulated approximately 548 hours since the overhauled cylinders were installed. A copy of the engine logbook is an attachment to this report.

Review of the overhaul manual for the accident series engine, dated January 1992, revealed that the tightening torque value for the thru-bolts is listed as 640-660 inch pounds. An excerpt from the manual is an attachment to this report.

The airplane minus the retained engine components was released to David E. Gourgues, Liability Specialist with Universal Loss Management, Inc., on July 18, 2001. The retained engine components were also released to David E. Gourgues, on February 22, 2002.

NTSB Probable Cause

The improper installation of the cylinders by other maintenance personnel for failure to assure that the cylinders were properly torqued resulting in fatigue crack in the crankshaft, and crankshaft failure. A finding in the investigation was fretting of both crankcase halves at several areas.