NTSB Factual Report

HISTORY OF FLIGHT

On April 7, 2012, about 2025 mountain daylight time, a Piper PA-28-181, N30997, landed in a field following a loss of engine power near Casper, Wyoming. The pilot was operating the airplane under the provisions of Title 14 Code of Federal Regulations Part 91. The student pilot and passenger were not injured. The cross-country flight departed Riverton Regional Airport, Riverton, Wyoming, about 1930, with a planned destination of Mitchell Municipal Airport, Mitchell, South Dakota. Visual meteorological conditions prevailed, and no flight plan had been filed.

The pilot reported that after reaching cruise altitude he observed a decrease in engine oil pressure. He continued to monitor the pressure indicator, and did not see a corresponding increase in oil temperature. He began to divert the airplane to Casper, and a few minutes later the engine speed began to decrease, with an accompanying engine vibration. He continued the diversion as the engine progressively began to lose power. The engine eventually lost all power, and the propeller stopped rotating.

The pilot was not in communication with any air traffic control facility at the time of the power loss, and subsequently transmitted a mayday call on the guard frequency. This transmission was heard by a United Airlines flight crew, who relayed the information to the Federal Aviation Administration (FAA) Salt Lake City Air Route Traffic Control Center (ARTCC).

The pilot subsequently landed in a field, and the airplane sustained substantial damage to the fuselage during the landing sequence. An FAA inspector responded to the accident site, and reported oil was still present within the engine crankcase, with fuel present in both wing tanks.

AIRPLANE INFORMATION

The airplane was equipped with a four-cylinder, normally aspirated Lycoming O-360-A4M engine, serial number L-24739-36A. Maintenance records revealed that the engine had undergone a factory overhaul, which was completed on December 14, 1998, about 770 flight hours prior to the accident. The most recent annual inspection was accomplished on June 15, 2011, at a total airframe time of 2,710 flight hours.

TESTS AND RESEARCH

Engine Exam

The engine was removed from the airframe, and examined at the engine overhaul facilities of Central Cylinder, Omaha, Nebraska, in the presence of an FAA inspector.

Disassembly revealed that the oil filter element and screen were clogged with shiny metallic debris. One of the number four piston pin plugs had disintegrated, with its remnants remaining within the pin cavity and plug area. The associated piston skirt walls exhibited plug-shaped gouging damage, which extended into the oil scraper piston ring groove. Additionally, the oil scraper ring was severed in the gouged area.

Further engine disassembly revealed metallic particle contamination throughout the engine's internal surfaces. The connecting rod bearings had become extruded at all four locations on the crankshaft rod journals, and the piston pins sustained radial grooves and scoring.

Lycoming Service Instruction

Lycoming Service Instruction 1492, originally issued on December 30, 1998, and updated to revision D on March 20, 2009, documented piston pin plug wear inspections. The service instruction is applicable to all Lycoming new or factory rebuilt, or factory overhauled engines shipped from Lycoming after January 1, 1994, and all engines (except O-235 models) which have had a Lycoming Cylinder Kit installed after January 1, 1994. Compliance is required at the next oil change/oil filter replacement, not to exceed 50 hours of engine operation.

According to the instruction, an increase in incidents of abnormally worn piston pin plugs had occurred in some units shipped after January 1, 1994. The letter goes on to state that evidence of such wear can be detected by use of an oil filter content inspection, or spectrographic oil analysis.

FAA regulations do not require compliance with manufacturer’s service instructions.

Oil and Filter Analysis

Examination of the airplane's maintenance records revealed that an engine oil and filter change was performed on January 26, 2012, 7.84 flight hours prior to the accident. The logbook entry stated, “Drained oil. Removed oil filter, cut open and inspected. No defects noted.” The entry did not indicate that an oil analysis had been performed.

According to the maintenance records, since overhaul, the oil filter element had been examined four times with negative results, and oil samples were removed twice for analysis. No records were located indicating the results of the oil analysis, and the owner, who purchased the airplane in August 2009, stated that he was unaware of an oil analysis ever being performed. The NTSB investigator-in-charge requested records from four of the major oil analysis laboratories. Only one laboratory had records of the engine being subject to an oil analysis, which occurred in April 2008. According to that report, the engine had accrued 518 total flight hours at that time. The results indicated an aluminum value of 2 parts per million, with diagnostic recommendations of “All values appear normal.”

ADDITIONAL INFORMATION

According to 14 Code of Federal Regulations, Part 61.89, a student pilot may not act as pilot-in-command of an aircraft that is carrying a passenger.

NTSB Probable Cause

A total loss of engine power during cruise flight due to a failed piston pin plug, which resulted in engine oil contamination and subsequent oil starvation. Contributing to the loss of power was the failure of maintenance personnel to identify contaminants produced by the failing plug during the last oil filter inspection.