NYC08LA201

A loss of engine power due to thermally-induced failure of a piston. Contributing to the accident was the sustained engine exposure to abnormally high operating temperatures and detonation, and the exceedance of the engine manufacturer's recommended overhaul interval by approximately 1,200 hours.

The pilot departed on a banner tow mission to the shoreline approximately 15 miles away. Approximately 6 miles prior to the shoreline, he noted a slight loss of altitude and added power to climb. He then noticed an increase in oil temperature and a decrease in oil pressure. He initially attempted to return to the departure airport, but could not maintain altitude. The pilot set up for a precautionary landing, but was unsuccessful when the engine lost power completely. The airplane struck trees while still airborne and came to rest in an open area. The Number 4 piston exhibited evidence of sustained exposure to abnormally high operating temperatures and detonation. A portion of the piston was thermally eroded from the head to below the oil scraper ring and the sidewall was penetrated in the eroded area. The operator monitored fleet fuel consumption very closely and encouraged the pilots to regularly lean the fuel mixtures. The engine had accumulated 3,200 hours since major overhaul, which was 1,200 hours beyond the manufacturer's recommended time of 2,000 hours.

HISTORY OF FLIGHT On May 31, 2008, about 1115 eastern daylight time, a Piper PA-18-135, N802DA, was substantially damaged when it impacted trees during a forced landing near Myrtle Beach, South Carolina. The certificated commercial pilot received minor injuries. The aerial banner tow flight was operated by SC Sky Signs under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. According to the pilot, he departed the operator's private grass airstrip in Conway, South Carolina, about 1058, and planned to fly to, and then along, the shoreline. The pilot leveled the airplane at an altitude of approximately 1,000 feet for the transit to the shoreline. Just after he informed the controller at the Myrtle Beach International Airport (MYR) air traffic control tower (ATCT) that he had crossed the extended centerline of MYR runway 36, the pilot noticed that his altitude had decreased to 900 feet. He applied power and climbed back to 1,000 feet. The pilot then observed the engine oil temperature increasing and felt the engine "losing power." He communicated with MYR ATCT and requested a 180-degree turn back to his home airport. When the pilot completed the turn, he noted that the oil pressure was falling, and that the oil temperature was continuing to increase. At this point the pilot knew that he could not get the airplane safely to either the departure airport or MYR, and that he would have to conduct an off-airport landing. He observed a street in a housing development that he thought would serve as a suitable landing site, and set up for a right traffic pattern. When the airplane was approximately 400 to 500 feet above the ground, the pilot spotted a clearing and released the banner that he was towing. The pilot then requested that MYR ATCT notify fire/rescue authorities that he was making a forced landing. At a position about "midfield downwind" for his selected landing site, the engine "quit," and the pilot realized that he did not have sufficient altitude to reach that site. He then selected and headed for a second landing site, and the wings impacted trees prior to the touchdown. PERSONNEL INFORMATION According to information provided by the pilot, he had approximately 840 total hours of flight experience, with approximately 120 hours in the accident airplane make and model. The pilot reported 126 hours of flight experience in the 90 days preceding the accident. His most recent flight review was conducted on February 28, 2008. His most recent second-class medical certificate was issued on April 1, 2008. AIRCRAFT INFORMATION According to Federal Aviation Administration (FAA) records, the airplane was manufactured in 1953. At that time, it was equipped with a Lycoming O-290 engine. At the time of the accident, the airplane was equipped with a Lycoming O-320 engine, but the most current airplane registration indicated that an O-290 engine was installed. A supplemental type certificate (STC SA00522SE) was commercially available to permit the installation of a Lycoming O-320 engine in the accident airplane make and model. The operator did not make any airframe, engine, or propeller logbooks available for the investigation. Examination of the airplane's airworthiness documents that were maintained by the FAA revealed that the documentation did not provide a continuous chronology of the engines installed in the airplane. No documentation of the incorporation of STC SA00522SE, or the replacement of the original O-290 engine with the O-320 engine, could be located. The earliest document that referenced a Lycoming O-320 engine was dated February 17, 1992. That document related to a modification to the pistons in the engine. The engine serial number on that document did not match the serial number of the accident engine. An additional document, dated May 25, 2005, also referenced an O-320 engine, but did not contain any engine serial numbers. That document referenced an inspection compliance with STC SA00522SE. METEOROLOGICAL INFORMATION The 1145 surface weather observation at MYR reported winds from 230 degrees at 11 knots, visibility 7 miles, clear skies, temperature 29 degrees Celsius (C), dew point 20 degrees C, and an altimeter setting of 30.06 inches of mercury. WRECKAGE AND IMPACT INFORMATION The operator's airstrip was located approximately 10 miles west-northwest of MYR, and the accident site was located approximately midway between MYR and the operator's airstrip. The airplane struck trees and came to rest in a flat area adjacent to a residential neighborhood. An FAA inspector conducted a preliminary examination of the airplane at the accident site. The left wing was partially separated from the fuselage, and the right wing exhibited leading edge crush damage. The fuselage was essentially intact, with some crumpling of the structure just aft of the left wing. The engine and propeller remained attached to the airplane. One propeller blade appeared intact and undamaged, and the other blade was bent aft approximately 50 degrees at the one-third span point. The landing gear was deformed upwards, and the empennage exhibited multiple impact damage sites. The airplane was transported to the operator's facility, and a subsequent engine examination was conducted under the supervision of the FAA. ADDITIONAL INFORMATION Engine Examination The engine was examined at the operator's facility by an FAA inspector, assisted by a mechanic employed by the operator. According to the mechanic, the engine had a total time in service of 5,457 hours, and had accumulated approximately 3,200 hours in service since the last overhaul. The engine manufacturer's recommended time between overhaul for the accident engine was 2,000 hours. The intake and exhaust systems were not installed on the engine at the time of the examination. The examination did not note any damage to the magnetos, ignition harnesses, spark plugs, accessory section, or crankcase. The fuel and induction systems were not examined. The camshaft exhibited "normal wear." The main bearings were not examined, the crankshaft exhibited minor scoring, the connecting rods were "ok,", and the connecting rod bearings exhibited scoring and pitting. The general condition of the lubrication system and sump was "ok." The oil screens were clean, with no metal found. The oil pump was "frozen" initially, but rotated freely on the second day of the examination. The No. 3 intake and exhaust valves "were leaking, but not due to any heat damage," and no other damage to the valve train was noted. The No. 4 cylinder, piston and rings were heat damaged, and the piston was sent to the National Transportation Safety Board for additional examination. No. 4 Piston The piston head was essentially intact, with a distinct coloration pattern. The juncture of the piston head and piston side was eroded along an arc approximately 1 1/4 inches long. The side of the piston below the arc exhibited significant erosion, scoring and metal transfer. The erosion extended from the piston head to below the oil scraper ring. All three piston rings were fractured, and partly eroded in the area. A triangular hole, approximately 1/2 inch by 1/4 inch, penetrated the piston wall adjacent to one wrist pin boss. The wrist pin exhibited bluing of its finish, and the piston interior was blackened. According to Lycoming, the coloration pattern on the head was typical of detonation, and the wrist pin bluing, as well as the blackening of the piston interior, were indications that the piston had been exposed to abnormally high operating temperatures. Fuel Mixture Guidance According to the current STC holder, the STC which installed the O-320 engine in the PA-18 (STC SA00522SE) did not contain any guidance or limitations concerning fuel mixture. The Piper-produced PA-18 equipped with a