Cottonwood, AZ, USA
N8327N
Beech V35A
During initial takeoff climb, the pilot heard a "loud bang" from the engine, followed by a smell of fuel in the cockpit, a loss of fuel pressure, and a substantial engine vibration. During an attempt to return to the airport, the engine lost power, and the pilot initiated a forced landing. During the landing, the airplane impacted a cattle gate and came to rest on its nose. Examination of the engine revealed that the #1 lower connecting rod bolt was fractured at the bolt's dowel section, which corresponded with the connecting rod and rod cap split line. According to the engine manufacturer's metallurgist, the fracture initiated at the outer diameter of the bolt's dowel section, and the fracture progressed in fatigue until the bolt fractured as a result overstress. The bolt's dowel section exhibited fretting damage at the fracture origin. At the time of the accident, the engine had accumulated 9.64 hours since the annual inspection, and 195.84 hours since major overhaul.
On June 20, 2002, at 0650 mountain standard time, a Beech V35A, single-engine airplane, N8327N, was substantially damaged during a forced landing following a loss of engine power during the initial takeoff climb from Cottonwood Municipal Airport, Cottonwood, Arizona. The airplane was registered to and operated by the pilot. The private pilot and his passenger were not injured. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The cross-country flight originated from Cottonwood Municipal Airport at the time of the accident and was destined for Glendale Municipal Airport, Glendale, Arizona. According to the 3,500-hour pilot, during the initial takeoff climb while climbing through 1,200 feet agl, he heard a "loud bang" from the engine, followed by a smell of fuel in the cockpit, a loss of fuel pressure, and a substantial engine vibration. During an attempt to return to the airport, the engine lost power. After realizing that he was not going to be able to return to the airport, the pilot executed forced landing to a rural road. During the landing, the airplane impacted a cattle gate and came to rest on its nose. During the impact with the gate, the left wing spar bent aft. The airplane was recovered for further examination. A review of the airplane's maintenance records revealed that the 285-horsepower Teledyne Continental Motors (TCM) IO-520-BA (10) engine, serial number 241517R, underwent its most recent annual inspection on April, 3, 2002, at a total time of 1,633.90 hours. A major overhaul was completed on the engine on May 13, 1999, at a total time of 1,447.71 hours. At the time of the accident, the engine had accumulated 9.64 hours since the annual inspection, and 195.84 hours since major overhaul. On July 24, 2002, at the facilities of Air Transport Inc., Phoenix, Arizona, under the supervision of an FAA inspector, the airframe and engine were examined. According to the TCM representative who participated in the examination, an attempt to run the engine on the airframe was unsuccessful. The #6 cylinder valve cover was removed, the engine was then rotated by hand, and it was determined that engine continuity could not established to the six cylinders. An engine teardown was started by the TCM representative; however, the teardown was suspended when the #1 rod cap was found separated from the #1 connecting rod. The engine was then crated and shipped to TCM for further examination. On September, 17, 2002, at the TCM facility near Mobile, Alabama, under the supervision of the NTSB investigator-in-charge, the engine teardown was completed. The teardown revealed that the #1 lower connecting rod bolt, Superior Air Parts part number SA629340, was fractured at the bolt's dowel section, which corresponded with the connecting rod and rod cap split line. The bolt's fracture surfaces were examined by a TCM metallurgist under a Scanning Electron Microscope (SEM). According to the TCM metallurgist, the fracture initiated at the outer diameter of the bolt's dowel section, and the fracture progressed in fatigue until the bolt fractured as a result overstress. The bolt's dowel section exhibited fretting damage at the fracture origin. The #2, #3, #4, #5, and #6 upper and lower connecting rod bolts were checked for tightening torque, break-a-way torque, and the bolt lengths were measured as installed on the crankshaft and then removed. The various checks performed on the bolts did not revealed any evidence of improper installation during the engine's major overhaul. A review of the major overhaul work order revealed that new connecting rod bolts (p/n: SA629340) were installed at overhaul. In addition to the fractured connecting rod bolt, the teardown revealed that the camshaft was fractured forward of the #2 exhaust lobe, and forward of the #1 exhaust lobe. The camshaft fracture surfaces were examined by the TCM metallurgist. The TCM metallurgist stated that the fractures were the result of overstress due to impact with the failed #1 connecting rod.
The loss of engine power as a result of the failure of the #1 lower connecting rod bolt due to fatigue.
Source: NTSB Aviation Accident Database
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