CEN10LA306

While on a cross-country flight, the airplane experienced a total loss of engine power when the No. 2 cylinder, piston, and connecting rod separated from the engine. The pilot reported that the airplane had insufficient altitude to reach the nearest airport, and a forced landing was made into an agricultural field. A postaccident metallurgical examination revealed multiple fatigue fractures of the attachment fasteners used to secure the No. 2 cylinder to the crankcase. The observed fatigue was the result of an insufficient fastener preload. The engine had accumulated 519 hours since the last major overhaul. Review of the engine logbook established that there were no maintenance actions completed to the No. 2 cylinder, piston, or connecting rod since the last overhaul. Therefore, the insufficient fastener preload was likely due to improper overhaul practices during the last engine overhaul.

On June 7, 2010, at 1034 eastern daylight time, a Cessna 177RG airplane, N2016Q, was substantially damaged during a forced landing near Marietta, Ohio. The commercial pilot was not injured. The airplane was registered to and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 while on an instrument flight plan. Day visual meteorological conditions prevailed. The personal flight departed from Indianapolis Metropolitan Airport near Indianapolis, Indiana, at 0845, destined for Williamsburg-Jamestown Airport near Williamsburg, Virginia. The pilot reported that while en route at 7,000 feet mean sea level (msl) he noticed a faint smell of engine oil that was followed by a slight roughness in engine operation. However, at that time, all of the engine gauges were indicating within their normal operating ranges. About two minutes later, an audible “thud” was heard from the engine compartment and the left engine cowl was suddenly dislodged and torn from its adjacent structure. The airplane’s left windscreen and left fuselage window were subsequently obscured by engine oil. The pilot elected to secure the engine because it was operating very roughly and was only producing limited power. After the engine was shut-down, he established best-glide airspeed and declared an emergency with the air traffic controller. The air traffic controller subsequently provided radar vectors to the nearest airport, Mid-Ohio Valley Regional Airport, near Parkersburg, West Virginia. The pilot reported that when the airplane had descended to 3,000 feet msl it became apparent that there was not enough altitude to reach the airport. He decided to restart the engine in an attempt to extend his glide with any available engine power. The engine ran very roughly for a few minutes before it experienced a complete loss of engine power while descending through approximately 2,500 feet msl. After the final loss of engine power, the airplane still did not have enough altitude to reach the intended airport. The pilot then performed an intentional wheels-up landing into a field of tomatoes and soybeans. The airplane’s lower fuselage structure and left stabilator were damaged during the forced landing. A postaccident examination conducted by Federal Aviation Administration (FAA) inspectors established that the No. 2 cylinder, piston, and connecting rod had separated from the engine. The entire No. 2 cylinder was located within the engine cowling. The corresponding No. 2 piston, connecting rod, and rod cap departed the airplane during flight, but were subsequently recovered. The engine was disassembled under the supervision of FAA inspectors and revealed internal component damage consistent with a lack of oil lubrication throughout the engine due to the separation of the No. 2 cylinder. The engine's No. 2 cylinder, piston, connecting rod, rod cap, rod bolts, crankcase through-bolts, and two crankcase threaded studs were sent to the NationalTransportation Safety Board's (NTSB) Materials Laboratory Division for metallurgical examination. The NTSB lab examination established that both crankcase through-bolts had fractured on the No. 2 cylinder side. The upper through-bolt was fractured immediately adjacent to the threaded region. The lower through-bolt was fractured about midway through the threaded region. Additional magnified optical examinations of the through-bolt fractures revealed ratchet and arrest markings indicative of fatigue propagation from multiple origins. No damage or corrosion was noted in the fatigue origin areas. The enlarged dowel section areas, located midspan of both through-bolts, exhibited fretting and scoring consistent with relative movement between the crankcase halves. Examination of the crankcase threaded studs revealed fracture features consistent with fatigue propagation. Additionally, a portion of crankcase exhibited fretting between the studs indicative of relative motion between the cylinder and the crankcase. Examination of the fractured rod bolt revealed extreme stretching and necking deformation consistent with overstress separation at elevated temperatures. The engine, a Lycoming model IO-360-A1B6D, serial number L-11301-51A, had accumulated 519.1 hours since its last major overhaul, which was completed on May 16, 2006, at 5,963 hours total time. A postaccident review of the engine maintenance information found no maintenance actions were completed to the No. 2 cylinder, piston, or connecting rod since the last overhaul. The last annual inspection was completed on July 1, 2009, at which time the engine had accumulated 441.9 hours since the last overhaul. The last recorded engine maintenance, completed on March 21, 2010, consisted of an engine oil and filter change. At 1053, the automated surface observing system at the Mid-Ohio Valley Regional Airport, located about 3.6 miles east of the accident site, reported the following weather conditions: wind 270 degrees at 4 knots; visibility 10 miles; few clouds at 3,000 feet above ground level (agl), scattered clouds at 3,700 feet, and a broken ceiling at 5,000 feet agl; temperature 19 degrees Celsius; dew point 13 degrees Celsius; altimeter setting 30.02 inches of mercury.