NTSB Factual Report

On September 30, 2016, about 1430 central daylight time, a Cessna 177RG, N1528H, sustained substantial damage during a forced landing following a loss of engine power near Cloquet, Minnesota. The pilot was not injured. The airplane sustained damage to the aft fuselage. The airplane was registered to Aero Environmental Consulting, LLC and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The local flight originated from the Cook Municipal Airport (CQM), Cook, Minnesota, about 1300 and was destined for the Field of Dreams Airport (04W), near Hinckley, Minnesota.

The pilot reported that while in cruise flight he detected a slight ticking sound coming from the engine. He checked the oil pressure gauge and noted that the oil pressure indication was just below the green arc but still above the critical red line that indicated minimum oil pressure. The pilot elected to divert to the Cloquet/Carlton County Airport (COQ), Cloquet, Minnesota, in order to check the engine. As the airplane approached COQ, the engine noise became louder, and the oil pressure continued to drop. When the airplane was about 5 miles from COQ the oil pressure had dropped below the red line, and the engine was "knocking" loudly. About 3 miles from COQ, the engine stopped and the propeller did not windmill. The pilot attempted to glide the airplane to COQ, but had insufficient altitude and landed in a field short of the approach end of runway 17 at COQ. He reported that the landing was smooth, but on roll-out the airplane entered a roadside ditch resulting in damage to the airplane structure.

The airplane was powered by a Lycoming IO-360-A1B6D engine, serial number L-18530-51A. The engine was rated to produce 200 horsepower. An examination of the engine was conducted by National Transportation Safety Board and Federal Aviation Administration Investigators. The engine was removed from the airplane and a partial teardown examination completed. There was a fracture in the engine case above the no. 4 cylinder with a portion of the no. 4 connecting rod visible. There was also a crack in the accessory portion of the case behind the no. 4 cylinder. The engine contained about 5.5 quarts of oil. The rocker covers were removed and no anomalies were noted with regard to the rocker arms, valve springs, valve spring keepers, or push rod ends. The rear accessories and accessory case were removed and gear train continuity was confirmed. The no. 1, 3, and 4 cylinders were removed from the engine. The no.2 cylinder could not be fully removed due to damage to the cylinder skirt that prevented the piston from exiting the bottom of the cylinder. The no.4 connecting rod remained attached to the piston. The large end of the connecting rod had fractured adjacent to the rod cap bolt holes. Portions of the connecting rod and rod cap were found within the oil sump. The large end of the connecting rod exhibited discoloration consistent with heat distress. The no. 1 cylinder, piston, and connecting rod remained intact; however, the connecting rod could not be rotated on the crank shaft. The no.1 connecting rod bearing could be seen extruding from between the connecting rod and crankshaft cheek which indicated that failure of that bearing was imminent. The no.3 cylinder, piston, and connecting rod were intact. The no.2 cylinder, piston, and connecting rod were intact. The no.3 bearing was examined and showed signatures consistent with a lack of lubrication. The engine's oil pressure relief valve was disassembled and no anomalies were noted. The oil screen was plugged with debris, but the examination was unable to determine if the debris in the screen was secondary to the engine failure. The oil pump was disassembled and examined with no anomalies found. Examination of the remainder of the oil system did not reveal any anomalies.

A review of the airplane's maintenance records showed that the most recent annual inspection was completed on January 27, 2016. On that same date, a 100-hour inspection of the engine was completed at a recording tachometer reading of 4,250.8 hours. The engine had accumulated 1,320.56 hours since it most recent overhaul at the time of the inspection. The records further indicated that the most recent overhaul was completed on April 26, 1993, and the engine was installed on the accident airplane on June 4, 1993. During the postaccident engine examination the recording tachometer read 4,278.4 hours, indicating that it had accumulated 27.6 hours since the annual/100-hour inspection. A subsequent maintenance entry indicated that the engine oil and filter were changed on April 19, 2016, at a recording tachometer reading of 4,259.22 hours.

Lycoming Service Instruction 1009AT stated: "Engine deterioration in the form of corrosion (rust) and the drying out and hardening of composition materials such as gaskets, seals, flexible hoses and fuel pump diaphragms can occur if an engine is out of service for an extended period of time. Due to the loss of a protective oil film after an extended period of inactivity, abnormal wear on soft metal bearing surfaces can occur during engine start. Therefore, all engines that do not accumulate the hourly period of time between overhauls specified in this publication are recommended to be overhauled in the twelfth year." The publication listed a recommended time between overhaul for the accident engine as 2,000 hours.

NTSB Probable Cause

A lack of lubrication in the engine for reasons that could not be determined based on the available information, which resulted in a failure of the No. 4 connecting rod and a subsequent total loss of engine power.