Accident Overview
On September 6, 2013, at approximately 1754 eastern daylight time, an ERCO Ercoupe 415-D, registration N3940H, was substantially damaged during a forced landing near Beaver County Airport (BVI) in Beaver Falls, Pennsylvania. The airline transport pilot and passenger were not injured. The aircraft was operated as a personal flight under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight was originating at BVI and destined for North Central West Virginia Airport (CKB) in Clarksburg, West Virginia.
Pilot Actions
The pilot reported that he had flown into BVI earlier that day without incident and conducted a preflight inspection before the return flight, noting no anomalies. After takeoff, while climbing through 200 feet above ground level, the engine began to run rough. The pilot attempted to turn back toward the airport, but halfway through a 180-degree turn, a total loss of engine power occurred. Unable to maintain altitude, the pilot executed a forced landing to a field, resulting in substantial damage to both wings.
Aircraft Examination
A Federal Aviation Administration (FAA) inspector examined the engine assembly and found no anomalies in the induction, carburetor, or fuel systems. The aircraft was equipped with a Continental C75 series 75-horsepower engine, which had flown approximately 60 hours since its last inspection. The engine logbooks were not available for review by the NTSB. During the examination, approximately 18 gallons of blue fluid, similar in color to 100LL aviation fuel, were found in the header tank.
Engine Findings
Further examination revealed that the number 3 exhaust valve was stuck in the open position, and an engine run was not performed. No internal engine damage was noted as a result of the stuck valve. The valve train was intact, and hand rotation of the crankshaft achieved valve train continuity and compression on cylinders 1, 2, and 4. Examination of the magnetos showed spark on all ignition leads. The top and bottom spark plugs were removed; the plugs from cylinders 2 and 4 were carbon fouled, while the others exhibited normal wear signatures. The number 3 cylinder was removed, and an excessive amount of coking was noted on the mid-span of the bore of the valve guide. The engine oil was free of debris and at the operational level.
Fuel and Maintenance Considerations
A review of the Continental Motors safety bulletin (SB) M77-3 indicated that 100LL fuel, while acceptable, could increase lead buildup and fouling of spark plugs, as well as lead to exhaust valve sticking due to lead salt accumulation in the lubricating oil. The bulletin recommended regular 50-hour oil changes to reduce such accumulation, but no record of 50-hour oil changes was noted in the engine logbook. Additionally, spark plugs should be rotated every 50 hours and cleaned or rotated every 100 hours. A review of an FAA chart titled "Conditions Favoring Carb Ice Formation" suggested that at the ambient temperature and dew point, serious icing at glide power was probable at the time of the accident.