NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The pilot reported that the accident flight was his second skydiving flight of the morning and that the airplane was performing “normally” as it had during the first flight. During climbout, he noted that the engine cylinder head temperatures were in the “normal” range. When the airplane reached about 4,000 ft mean sea level, the engine experienced a total loss of power, and, about 1 minute later, the propeller stopped windmilling. The pilot conducted an off-airport landing to a nearby highway. During the landing roll, and to avoid impacting vehicles on the highway, the pilot guided the airplane onto the median, and the wings and horizontal stabilizer impacted several road signs, which resulted in substantial damage to the airplane.Disassembly and examination of the engine revealed that the crankshaft was fractured near the No. 2 main bearing. The No. 2 main bearing saddle mating surface exhibited extensive fretting, and the areas adjacent to the No. 2 bearing on the inside of the engine case exhibited rotational scoring, indicating that bearing movement had occurred before the crankshaft failure and that insufficient torque had been applied to the cylinder through bolts. Review of the maintenance logbooks revealed that, 19 days before the accident, a mechanic replaced the No. 2 cylinder. It is likely that the mechanic applied insufficient torque to the through bolts after replacing the No. 2 cylinder, which allowed the bearings to move and led to the eventual failure of the crankshaft.