LIVERMORE, CA, USA
N9ND
ZIVKO AERONAUTICS EDGE 540
The pilot said he was in normal cruise flight when the 200-hour since new Lycoming AEIO-540 engine began to over speed. The pilot said a roughness, which progressively worsened, was associated with the onset of the over speed event. He stated that he was unsuccessful in regaining control of the engine and initiated a power-off forced landing to a clear area next to a highway. The aircraft touched down in soft, muddy soil and the landing gear was torn out of the structure. Cracks were found across the rear of the engine case between the Nos. 5 and 6 cylinders. Disassembly of the engine revealed that one of the two counterweight rollers had become dislodged from the corresponding counterweight crankshaft lug bore and precipitated a catastrophic internal failure of the No. 6 connecting rod. Detailed examination of the separated counterweight crankshaft lug bore revealed rotational scoring around the inside diameter of the hole, while the roller bushing was broken in two pieces and displayed rotational scoring marks around the outside diameter. The designed bushing to bore clearance provides for an interference fit. The problematic lug bore was measured for circularity, position, and diameter with respect to design specifications. The lug bore was found outside of acceptable tolerances in all areas. According to Textron Lycoming and the FAA, a small number of crankshafts by serial number where produced with the lug bore(s) misreamed to an out of round condition during that stage of the manufacturing process. The accident crankshaft by serial number was outside of the believed problem range.
On February 18, 1999, at 1640 hours Pacific standard time, an experimental Zivko Aeronautics Edge 540 airplane, N9ND, landed in soft, muddy terrain near Livermore, California, following a loss of engine power. The aircraft sustained substantial damage to the landing gear mounting structure and one wing during the landing. The commercial pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed at the time. No flight plan was filed for the cross-country personal flight, which originated at Tracy, California, on the day of the accident, at 1620, with a destination of San Carlos, California. The flight was operated under 14 CFR Part 91 of the Federal Aviation Regulations by Norman Dewitt Air Shows, LLC, of Atherton, California. The pilot was interviewed by telephone the day after the accident. He reported that he was in normal cruise flight when the Lycoming AEIO-540 engine began to over speed. The pilot said a roughness, which progressively worsened, was associated with the onset of the over speed event. He stated that he was unsuccessful in regaining control of the engine and initiated a power-off forced landing to a clear area next to a highway. The aircraft touched down in soft, muddy soil and the landing gear was torn out of the structure. Initial external examination of the engine by a Federal Aviation Administration (FAA) airworthiness inspector disclosed cracks across the rear of the engine case between the Nos. 5 and 6 cylinders. Review of the maintenance records disclosed that the engine was assembled from new parts by an engine overhaul facility on January 19, 1998, and had accrued a total of 200 hours. The engine was partially disassembled for examination on March 4, 1999, under the supervision of an FAA airworthiness inspector. The Nos. 5 and 6 cylinders were removed and the No. 6 connecting rod was found fractured at the beam near the crankshaft journal end. The rod end remained attached at the journal. One of the crankshaft counterweights (No. 1) was found partially dislodged from the crankshaft lug, with the counterweight scored on the outer circumference. Heavy scoring and impact marks were noted on the rear side of the No. 5 cylinder skirt and piston, and, on the case spine. The camshaft exhibited impact marks and was separated at a point corresponding to the rotational arc of the No. 6 connecting rod. Further disassembly revealed that one of the two counterweight rollers had become dislodged from the corresponding counterweight crankshaft lug bore. The roller, fragments of one retaining washer, and the bushing were found in the sump. The roller retaining washer snap ring remained in its groove in the counterweight. The opposing washer and snap ring remained in place on the counterweight. The No. 2 counterweight remained attached to its crankshaft lug, with all snap rings, washers, rollers, and bushings intact. No heat distress signatures were observed to any internal component on further disassembly of the engine. Lubricants were present throughout. Detailed examination of the separated counterweight crankshaft lug bore revealed rotational scoring around the inside diameter of the hole, and the peripheral edges had displaced material raised along the edges which was sharp to the touch. The roller bushing was broken in two pieces and displayed rotational scoring marks around the outside diameter. The fractures were located about 270 degrees apart. According to Textron Lycoming, the designed bushing to bore clearance provides for an interference fit. The crankshaft and all counterweight components were sent to Textron Lycoming for detailed measurement of the lug bores under the direct supervision of FAA inspectors from the Harrisburg, Pennsylvania, Flight Standards District Office. The measurement process was to determine the circularity, position, and diameter of the problematic lug bore with respect to design specifications. The detailed table of resulting measurements is appended to this file; however, the lug bore was found outside of acceptable tolerances in all areas. Subsequent discussions with Textron Lycoming and the FAA representative disclosed that they were aware of a small number of crankshafts by serial number where the lug bore(s) were misreamed to an out of round condition during that stage of the manufacturing process. The accident crankshaft by serial number was outside of the believed problem range.
The manufacturer's inadequate quality control procedures, which allowed an improperly manufactured crankshaft to be shipped, resulting in the separation of one counterweight from the crankshaft lug and the subsequent catastrophic internal failure of the engine.
Source: NTSB Aviation Accident Database
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