According to the pilot, he departed for a flight to his home base airport. While the Ercoupe 415-D was climbing through 200 feet above ground level, the engine began to run roughly. While he was attempting to turn back toward the airport in Beaver Falls, Pa., the engine experienced a total loss of power. He subsequently made an emergency landing in a nearby field.
A post-accident examination of the engine revealed that the No. 3 cylinder exhaust valve was stuck in the “open” position and that the Nos. 2 and 4 cylinder spark plugs were carbon fouled.
Although an engine manufacturer service bulletin (SB) stated that 100LL was an acceptable alternative fuel, it also indicated that “the amount of tetraethyl lead in these higher grade fuels has increased the lead build up and fouling of spark plugs.”
The SB noted that, when this type of fuel is used, “exhaust valve sticking could result from lead salt accumulation in the lubricating oil,” and it recommended that “regular 50 hour oil changes be implemented to reduce such accumulation.”
The SB also recommended that the spark plugs be rotated every 50 hours of operation and cleaned and rotated every 100 hours.
A review of the engine maintenance logbooks revealed that the airplane’s most recent annual inspection was completed about 60 hours before the accident. No record was found indicating that the oil was changed after the annual inspection.
Based on the condition of the exhaust valve and the spark plugs and the maintenance records, it is likely that the pilot did not follow the SB-recommended procedures, which resulted in the engine carbon buildup and the exhaust valve being stuck open.
The NTSB determined the probable cause as the owner/pilot’s failure to follow engine manufacturer recommendations for engine oil changes and spark plug cleaning and rotating when operating the airplane with 100LL, which resulted in carbon buildup in the engine and the total loss of engine power due to the No. 3 cylinder exhaust valve being stuck open.
NTSB Identification: ERA13LA406
This August 2013 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.