N2175K

On September 29, 2015, about 1100 central daylight time, a Piper PA-28RT-201T, N2175K, operated by a private individual, was substantially damaged during a forced landing to a field, following a total loss of engine power during cruise flight near Dawson Springs, Kentucky. The private pilot was seriously injured. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the planned flight to Owensboro Airport (OWB), Owensboro, Kentucky. The flight originated from Foley Municipal Airport (5R4), Foley, Alabama, about 0730.The pilot reported that while in cruise flight at 7,000 feet mean sea level (msl), he heard a loud bang and the engine began to run rough. He declared an emergency to air traffic control (ATC); after which, another bang was heard and the engine lost all power. Additionally, pieces of the engine exited the cowling and oil flowed onto the windscreen. With the assistance of ATC, the pilot attempted to divert to runway 36 at Tradewater Airport (8M7), Dawson Springs, Kentucky; however, after descending through a cloud layer at 1,800 feet msl, the pilot could not locate the turf runway and elected to perform a forced landing to a field.

Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed that it came to rest upright against a small tree, in a field about 1 mile west of 8M7. The inspector observed damage to both wings and the fuselage. The airplane was equipped with a Continental Motors TSIO-360 engine. A hole was observed in the top rear of the engine crankcase, near the No. 2 cylinder. Subsequent teardown examination of the engine revealed that a rear crankshaft counterweight had separated and the adjacent (No. 2) connecting rod also separated at the connecting rod bolts. Metallurgical examination of the counterweight revealed fatigue cracking with an origin at the counterweight aft blade surface near a bushing hole. Marks on the bushing hole were consistent with loose bushing movement over a period of time.

Review of maintenance records and information provided by the pilot revealed that the engine had been operated for about 80 hours since its most recent annual inspection, which was completed on November 4, 2014. At that time, the engine had accumulated 1,049 hours since its last overhaul, which was completed on January 4, 1997. Continental Motors service bulletin M93-4 provided information about crankshaft counterweights at overhaul and included:

"…Removing and replacing bushings with makeshift tools can result in damage to the crankshaft and counterweights. A special tool for removing and replacing the bushings is supplied…WARNING…Improper installation of the bushings, retaining plates or retaining rings will cause engine failure…" In addition, Continental Motors also published a service information letter (SIL) that provided information regarding time limits between major overhauls. For the make and model engine, the SIL recommended 1,800 hours of operation or 12 years, which ever occurred first.

Madisonville Regional Airport (2I0), Madisonville, Kentucky, was located about 16 miles northeast of the accident site. The recorded weather at 2I0, at 1055, was: wind from 100 degrees at 4 knots; visibility 5 miles in light rain; scattered clouds at 1,900 feet; broken ceiling at 3,700 feet; overcast ceiling at 4,400 feet; temperature 22 degrees C; dew point 22 degrees C; altimeter 29.90 inches Hg.