Caledonia, MI, USA
N4632A
CESSNA P210N
The pilot and certified flight instructor were in a holding pattern during an instrument proficiency check when they heard a bang from the airplane's engine area. They initiated a forced landing and the airplane impacted terrain at the base of a hill. Fuel leaked and a ground fire ensued, resulting in substantial damage to the left wing. No airframe preimpact anomalies were observed on-scene. An engine teardown inspection revealed a separation of the crankshaft No. 3 short cheek consistent with fatigue. Additionally, the No. 2 lower through-bolt had the lowest torque value of all bolts and incorrect hardware was used on that through-bolt. Fretting was observed on the mating surfaces of the main bearing supports near the No. 2 through-bolt and its bearing had spun out of its support. Engine logbook entries indicated a mechanic replaced cylinders that would have required the removal and installation of hardware on the No. 2 through-bolt, approximately 19 months prior to the accident.
On September 6, 2010, about 0845 eastern daylight time, a Cessna P210N, N4632A, operated by Centurion Aviation LLC and piloted by a commercial pilot with a certificated flight instructor (CFI) on board, sustained substantial damage when it impacted terrain during a forced landing following an in-flight loss of engine power while maneuvering near Caledonia, Michigan. A post-impact ground fire occurred. The instructional flight was operating under 14 Code of Federal Regulations Part 91 without a flight plan. Visual meteorological conditions prevailed at the time of the accident. Both the CFI and the commercial pilot reported no injuries. The local flight departed from the Gerald R. Ford International Airport (GRR), near Grand Rapids, Michigan, about 0800. The pilot reported that the purpose of the flight was to conduct an instrument proficiency check (IPC). The pilot stated that the airplane was fueled to full prior to departure. He indicated that during the IPC he was cleared by GRR air traffic controllers to climb to 4,000 feet above mean sea level and hold as published over a GRR navigational aid. The pilot said that while he was starting the hold’s outbound leg, he heard “a large bang from the engine area.” The pilot removed his view limiting devices and turned north toward GRR. The CFI advised GRR air traffic controllers that the flight had a problem and were returning to GRR. The pilot and CFI realized the airplane had no engine power and they agreed “to do an off field landing.” The pilot set up for an approach to an alfalfa field. The pilot stated that the terrain was rolling and the airplane impacted terrain at the base of a hill in the field where its nose gear separated. The airplane “careened sideways” into a corn field and came to rest in the corn field. Fuel leaked out of the left wing’s tip tanks and ignited. The pilot turned the airplane’s fuel selector to off. The CFI opened the emergency door and both pilots exited. The fire was extinguished by the local fire department. According to the pilot, the total elapsed time from the "engine loss to crashing was less than 2 minutes.” N4632A, a Cessna P210N, Centurion, serial number P21000810, was a six-place, single engine, full cantilever high-wing, all-metal airplane of semimonocoque construction. The wings were constructed with integral fuel tanks. The airplane was powered by a six-cylinder, horizontally opposed, turbocharged, air-cooled, fuel injected, Teledyne Continental TSIO-520-RCAF engine with serial number 517924. According to airplane logbook excerpts, the engine's number three and five cylinders were replaced on April 17, 2006, and its number one and two cylinders were replaced on February 18, 2007. According to the pilot's accident report, the airplane's last annual inspection was completed on September 3, 2009, and the airplane had accumulated 4,342 hours of total time at that inspection. At 0853, the recorded weather at GRR was: Wind 180 degrees at 11 knots, 10 statute miles visibility, sky condition broken 12, 000 feet, temperature 18 degrees C, dew point 12 degrees C, altimeter 29.93 inches of mercury. Federal Aviation Administration inspectors examined the wreckage on-scene. No airframe pre-impact anomalies were observed. The airplane’s engine was shipped to the engine manufacturer for a teardown inspection. The crankshaft exhibited a separation of its number three short cheek. The number two lower through-bolt torque was the lowest of all through-bolts found during the engine disassembly. A nut, specified to be used on a cylinder stud, was found installed on that through-bolt. Fretting was observed on the mating surfaces of the main bearing supports near that through-bolt and its bearing had also spun out of its support. The crankshaft separation exhibited beach and ratchet marks. An engine manufacturer metallurgist confirmed that the separation was consistent with fatigue.
A loss of engine power as a result of a fatigue failure of the crankshaft due to the loss of engine case through-bolt torque. Contributing to the accident was a mechanic's use of incorrect hardware.
Source: NTSB Aviation Accident Database
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