WPR19LA070

The pilot reported that, during cruise flight, the engine began to run rough and he attempted to troubleshoot; shortly thereafter, oil pressure decreased to 0 and the engine began to vibrate before it lost all power. The pilot performed a forced landing, during which the airplane struck a ditch and nosed over, substantially damaging the left wing. Examination of the engine revealed that the crankshaft was fractured in fatigue aft of the No. 3 connecting rod journal, adjacent to the counterweights. Both counterweights were in place and remained attached to the crankshaft. Detailed examination of the fractured crankshaft revealed some non-conformances in the geometric tolerances of several crankcase attributes, and polishing was observed on the crankcase saddle bore landings; however, none were deemed severe enough to cause the crankshaft to fail in the time and manner in which it occurred. The cause of the crankshaft failure could not be determined based on the available information.

On January 19, 2019, about 1400 mountain standard time, an experimental, amateur-built CCX-2000 airplane, N57FX, was substantially damaged when it was involved in an accident near Roll, Arizona. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, during cruise flight at an altitude of about 1,000 ft above ground level, the engine began to run rough. The pilot reduced engine power, enrichened the mixture, and turned on the emergency fuel pump and backup ignition, resulting in no change in the engine performance. Shortly thereafter, oil pressure decreased to 0 and the engine began to vibrate before it lost all power. The pilot initiated an off-airport landing to a nearby clearing. During the landing roll, the airplane struck a ditch and nosed over. Examination of the airplane by the pilot revealed that the airplane sustained structure damage to the left wing. Postaccident examination of the recovered airframe and engine revealed that the engine was seized, and manual rotation via the crankshaft flange was not possible. The cylinders, overhead components, and accessories were in place and no external damage was noted. The oil sump, associated oil lines, and filter were in place and no leaks or damage were noted. The oil filler cap and fill tube were intact, and no anomalies were noted. The oil dipstick showed about 7 quarts. The engine was disassembled and all pistons and associated piston pins, connecting rods, rod-end caps, and bearings were in place and remained attached to the crankshaft. The No. 4 connecting rod was seized to the crankshaft. The remaining connecting rods moved freely about their respective journals. Mechanical scoring and striations were noted on the skirt area of all four pistons. The associated pistons rings remained in place. Normal combustion deposits were noted on all four piston faces. The camshaft was in place and nominal damage was observed to the shaft and lobes. A significant amount of metallic debris was noted throughout the engine, oil filter, oil sump and finger screen. The crankshaft (serial number TA06B000322) was fractured aft of the No. 3 connecting rod journal, adjacent to the counterweights. Both counterweights were in place and remined attached to the crankshaft. The crankshaft, crankcase, main bearings, and cylinder Nos. 3 and 4 connecting rod assemblies were sent to the National Transportation Safety Board Materials Laboratory for further examination. A Senior Materials Engineer examined the submitted components. The examination revealed that the crankshaft was fractured at the aft end of the No. 3 connecting rod bearing journal at the transition radius to the counterweight assembly, as seen in Figure 1. Figure 1: View of the crankshaft. The fracture surface was examined using a stereo binocular microscope and the fracture was observed to be comparatively flat with radial lines and curved crack progression marksthat were consistent with fatigue crack progression. Figure 2: View of the aft section of crankshaft fracture area. The journal surface at the fracture origin was examined for any notable features, but none were found. Other areas around the origin exhibited rubbing and deformation consistent with damage after the separation of the crankshaft into two pieces occurred. The main bearing and connecting rod bearing journal diameters were measured and found to be within the required limits on the engineering drawing. The crankcase halves flatness of the parting line, diameter and roundness of the main bearing saddle bores in the bolted and torqued condition, along with the concentricity of the saddle bore were measured. The flatness of the right and left halves was 0.00018 inch and 0.00169 inch, respectively. The left half exceeded the requirement of 0.0010 inch on the manufacturer’s drawing. The bore diameters measured within the manufacturer’s limits. The roundness for bores Nos. 1 and 2 were found within limits; however, bore No. 3 exceeded the limit of 0.0010 inch. The bearing shells were sent to their manufacturer for further examination. The shells were inspected visually and dimensionally. The middle bearings did show more wear than normal, but nothing was observed that would prevent the two bearings from operating normally. Review of airframe and engine records revealed that assembly of the engine was completed on November 17, 2017. At the time of the accident, the engine had accumulated 77.3 hours total time since new.