Accident Sequence
The accident airplane experienced a loss of engine power while cruising at flight level 190 (19,000 feet) under visual meteorological conditions with clear skies and unrestricted visibility. The pilot reported the power loss about 16 minutes before impact and requested clearance to the nearest airport. Air traffic control (ATC) issued vectors to the Southwest Michigan Regional Airport (BEH).
Approximately 10 minutes before the accident, the airplane was positioned about 1.3 nautical miles north of BEH at an altitude of 13,500 feet. The pilot chose to follow ATC vectors rather than circle down over the airport. ATC provided vectors for runway 27 at BEH.
Witnesses reported seeing the airplane "spiraling down and crashing into the ground." The wreckage came to rest on the extended centerline of runway 27, approximately 1.12 nautical miles from the runway threshold. The distribution of the wreckage was consistent with a stall/spin accident.
Flight Data
Radar data showed that about four minutes before the accident, the airplane was on a 9.5 nautical mile final approach at 6,700 feet. Between 9.5 and 5.3 nautical miles, airspeed fluctuated between 119 and 155 knots, and the descent rate varied from 1,550 to 2,600 feet per minute. From 5.3 nautical miles to the last radar return at 1.5 nautical miles, airspeed dropped from 155 to 78 knots.
According to the Pilot Operating Handbook (POH), the accident airplane should be flown at best glide speed (92 knots) after a loss of engine power. Maintaining best glide speed during engine-out descents results in an average engine-out descent rate of 700 feet per minute.
Engine Examination
An engine teardown inspection revealed that the crankshaft (part number 13F27738, serial number V537920968) was fractured at the number five crankpin journal. Visual examination showed a fatigue-type fracture through the cheek aft of the number five crankpin journal. The exact cause of the crankshaft failure could not be determined due to mechanical damage at the fatigue initiation point.
The fracture features were consistent with 14 previous failures of the same part number. The engine manufacturer determined that those failures were most likely due to overheating of the steel during the forging process.