Accident Overview
On April 7, 2012, at about 2025 mountain daylight time, a Piper PA-28-181, registration N30997, made a forced landing in a field near Casper, Wyoming, following a loss of engine power. The flight was a cross-country trip under Title 14 Code of Federal Regulations Part 91, operated by a student pilot with one passenger; neither occupant was injured. The aircraft departed Riverton Regional Airport, Riverton, Wyoming, around 1930, destined for Mitchell Municipal Airport, Mitchell, South Dakota. Visual meteorological conditions prevailed, and no flight plan was filed.
Pilot Actions and Sequence of Events
The pilot reported that after reaching cruise altitude, the engine oil pressure decreased. He continued to monitor the gauge and noted no corresponding rise in oil temperature. He decided to divert to Casper. Shortly after, engine speed dropped with accompanying vibration. The engine progressively lost power and eventually stopped, with the propeller ceasing to rotate. The pilot was not in communication with air traffic control at the time of the power loss. He transmitted a mayday call on the guard frequency, which was heard by a United Airlines flight crew who relayed it to the FAA Salt Lake City ARTCC.
Landing and Post-Accident Inspection
The pilot landed in a field. The aircraft sustained substantial damage to the fuselage during the landing. An FAA inspector attended the site, noting oil present in the engine crankcase and fuel in both wing tanks.
Engine Examination
The engine, a Lycoming O-360-A4M (serial number L-24739-36A), was removed and examined. Disassembly revealed the oil filter element and screen clogged with shiny metallic debris. One of the number four piston pin plugs had disintegrated, with remnants in the pin cavity. The piston skirt walls had plug-shaped gouging extending into the oil scraper ring groove, and the oil scraper ring was severed in that area. Further disassembly indicated metallic particle contamination throughout internal surfaces, extruded connecting rod bearings at all four crankshaft rod journals, and radial grooves and scoring on piston pins.
Maintenance and Service Instructions
The engine had a factory overhaul completed on December 14, 1998, about 770 flight hours before the accident. Its most recent annual inspection was on June 15, 2011, at 2,710 total airframe hours. Lycoming Service Instruction 1492 (Revision D, March 20, 2009) covers piston pin plug wear inspections for applicable engines shipped after January 1, 1994. It requires compliance at each oil change, not exceeding 50 hours of operation. The instruction notes an increase in abnormally worn piston pin plugs in some units shipped after that date, detectable via oil filter inspection or spectrographic oil analysis. FAA regulations do not mandate compliance with manufacturer service instructions.
Oil Analysis Records
An oil and filter change occurred on January 26, 2012, 7.84 flight hours before the accident. The logbook entry stated the oil filter was cut open and inspected with no defects, but did not mention an oil analysis. Since overhaul, the filter was examined four times with negative results, and oil samples were taken twice for analysis. No analysis results were found in records. The owner, who bought the airplane in August 2009, stated he was unaware of any oil analysis. An inquiry to four major oil analysis labs found one record: an analysis from April 2008, at 518 flight hours since overhaul, showing an aluminum value of 2 ppm with a diagnosis of “All values appear normal.”
Regulatory Note
Per 14 CFR Part 61.89, a student pilot may not act as pilot-in-command of an aircraft carrying a passenger.