ERA14FA403

A total loss of engine power due to detonation/preignition damage of the No. 6 cylinder. Contributing to the accident was the pilot’s decision to continue flight after receiving an indication of an impending engine failure.

A friend of the commercial pilot reported that the purpose of the personal flight was to relocate the airplane to an airport about 19 miles northeast of the departure airport, where it could be stored in a hangar while the pilot was on an extended trip overseas. He added that the pilot attempted to complete the flight the day before the accident but that he was unable to start the airplane because the battery required servicing; the battery was serviced the morning of the accident. A lineman reported that, before the airplane departed on the day of the accident, he observed the pilot perform an extended engine run-up. He stated that typically the pilot would just "hop in and go." Radar data showed the airplane just after departure on a northerly heading climbing to about 1,600 ft mean sea level (msl). About 2 minutes after departure, the airplane turned west and descended to about 900 ft msl as it turned 360 degrees near the pilot's home. The airplane then resumed a northeasterly course and climbed to 2,400 ft msl, presumably toward the destination airport. About 9 minutes after departure, the airplane entered a descending right turn. The final radar targets showed the airplane about 1.25 nautical miles southeast of the accident site about 1,400 ft msl and on an approximate magnetic heading of 285 degrees. Postaccident examination of the airframe and flight controls revealed no anomalies. The propeller displayed signatures consistent with lack of engine power at the time of impact. Initial examination of the engine case revealed that it was breached in two locations, near the Nos. 2 and 4 cylinders, and that the Nos. 2, 3, and 4 connecting rods were fractured. Further examination of the engine revealed signatures consistent with preignition and/or detonation in the No. 6 cylinder, which had eroded the No. 6 cylinder piston face and subsequently allowed combustion gases to pressurize the engine crankcase. This likely caused the expulsion of oil from the engine via the breather tube and resulted in a lack of lubrication throughout the engine, consistent with the extreme thermal discoloration and mechanical damage observed in the engine's internal components. The cause of the preignition and/or detonation could not be determined. During the approximate 10-minute flight before the engine lost power, the pilot should have received several indications of an engine anomaly, including, but not limited to, a drop in oil pressure, a rise in oil temperature, a rise in cylinder head temperature, and engine roughness. However, the airplane's flight track after takeoff, including the low-level circling of the pilot's home and its continuation to the destination airport rather than returning to the departure airport, suggests that the pilot either did not observe these signs nor recognize them to be indicative of a serious engine problem or that he thought he would be able to complete the remaining short flight to the destination airport. Although it is uncertain when the anomalous engine indications might have begun, given the pilot's extended engine run-up, it is possible that they were observable as early as before takeoff. The fact that the pilot had attempted to complete the flight the previous day and had been unable to do so would likely have increased the pilot's desire to reach the destination airport and contributed to his unwillingness to cancel the flight, return to the departure airport, or conduct a precautionary off-airport landing before the engine failed. Although toxicological testing of the pilot's specimens detected pheniramine, diphenhydramine, and zolpidem, all of which can be sedating, the detected drug levels were well below therapeutic levels; therefore, it is unlikely that any of the medications or the combination of the medications impaired the pilot's ability to safely operate the airplane.

A detailed examination of the engine was conducted at the manufacturer's facility on August 26, 2014. The left magneto was separated from its mount, but remained attached to the engine by its ignition harness. Due to thermal damage to the distributor gear, the magneto drive shaft could not be rotated. The right magneto was destroyed. The sparkplugs were removed and displayed normal wear and sooting consistent with the post-crash fire. The #6 bottom spark plug was covered in oil and re-solidified splattered metal. The oil pump drive was intact. The oil pump cavity and gear teeth exhibited normal operating signatures. The oil pressure relief valve displayed corrosion, and the seat was covered with corrosion and debris. The oil cooler remained attached to the engine and exhibited no anomalies. The oil filter remained safety-wired in place on the oil filter adapter. No anomalies were observed. The oil sump drain plug was safety-wired. The aft right end of the oil sump was thermally damaged, exposing the inside of the sump. The sump was removed from the engine and thick, dark residual oil remained, along with fragments of connecting rod bolts, bearing metal, piston material, piston ring segments, and debris. The oil pick-up tube was undamaged, and the oil suction screen was free of obstruction. The cylinders were disassembled and examined. The #1, #3, and #5 cylinders, pistons, and intake and exhaust valve heads revealed signatures of normal wear. The #2 cylinder combustion chamber was coated with oil and debris. The valve heads exhibited normal operating signatures. The piston face displayed normal combustion deposits that were covered with oil, as well as two semi-circular impressions consistent with valve strikes. The piston skirt was fractured. The #4 cylinder combustion chamber contained oil and debris. The valve heads exhibited normal operating signatures, and the piston face exhibited no anomalies. The piston skirt was fractured and mechanically damaged. The #6 cylinder combustion chamber contained oil and debris. The cylinder head displayed re-solidified, splattered metal around the sparkplug holes, valves, and valve seats; a feature consistent with pre-ignition and/or detonation. The splattering was more prevalent on the bottom side of the cylinder. The top side of the piston face was also covered in the splattered metal, and the bottom side displayed deep pitting and erosion of the face. The piston skirt displayed signatures of thermal expansion, scoring, and material transfer. The crankshaft and counterweight assembly exhibited lubrication distress, thermal damage, and mechanical damage concentrated at the #2, #3, and #4 connecting rod journals. The crankshaft cluster gear was intact and exhibited normal operating signatures. The gear bolts were secure, and the gear teeth were undamaged. The crankshaft main bearing journals were intact and exhibited normal operating signatures. Both rear and forward sets of counterweight assemblies were intact and free to move on the hanger blades. All of the connecting rod journals exhibited thermal distress and scoring consistent with a lack of lubrication; the most damaged being the #2, #3, and #4 journals. The oil transfer collar was intact and undamaged, and the oil transfer plug was secure. The connecting rods exhibited significant thermal and mechanical damage, and the #2, #3, and #4 connecting rods were fractured at the journal end. Fragments of connecting rod cap exhibited thermal and mechanical damage. Fragments of connecting rod bolts and nuts exhibited mechanical damage and overload signatures. Fragments of the #2, #3, and #4 connecting rods displayed signatures consistent with lack of lubrication and thermal distress, and were found throughout the engine and in the oil sump. The remaining three intact connecting rod bearings exhibited signatures of lubrication distress and thermal smearing of the surface babbit, exposing the copper layer. The camshaft was thermally damaged, but otherwise displayed no anomalies. The crankcase displayed extensive thermal damage. The left side displayed holes above the #2 and #4 cylinder mounting pads. The crankcase interior displayed thermal damage toward the rear of the engine, with dark black sooting noted in the front of the engine. Mechanical damage was noted around the #3 and #5 cylinder bays. None of the main bearing support mating surfaces displayed any signs of fretting or bearing lock tab elongation. Soot, ash, and fractured engine components were found throughout the crankcase. On January 26, 2016, additional examination of the #6 cylinder was performed. The cylinder head was cut from the barrel, and re-solidified material was removed from the bottom spark plug hole to facilitate inspection of the spark plug helicoil. The helicoil did not display any anomalies. The Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25A), states, "Detonation is an uncontrolled, explosive ignition of the fuel/air mixture within the cylinder's combustion chamber. It causes excessive temperatures and pressures which, if not corrected, can quickly lead to a failure of the piston, cylinder, or valves. In less severe cases, detonation causes engine overheating, roughness, or loss of power." The handbook also states, "Preignition occurs when the fuel/air mixture ignites prior to the engine's normal ignition event. Premature burning is usually caused by a residual hot spot in the combustion chamber, often created by a small carbon deposit on a spark plug, a cracked spark plug insulator, or other damage to the cylinder that causes a part to heat sufficiently to ignite the fuel/air charge." The same publication, in Chapter 17, "Aeronautical Decision Making," describes several operational pitfalls or behavioral tendencies that pilots may encounter as they develop flight experience. One of these tendencies is "Get-there-it is;" defined as a disposition that "impairs pilot judgment through a fixation on the original goal or destination, combined with a disregard for any alternative course of action." The initial impact point (IIP) was identified as a tree about 80 feet in height, located at 30 degrees, 55.542 minutes north latitude, 86 degrees, 26.103 minutes west longitude, about halfway between CEW and 0J4. The wreckage path extended on a heading of about 310 degrees, with the outboard portion of the right wing located in a tree about 90 feet past the initial impact point. The outboard portion of the left wing came to rest near the base of the tree. A ground scar containing the propeller, which had separated from the engine at the propeller flange, was located about 110 feet beyond the IIP. The main wreckage came to rest upright on a heading of about 145 degrees about 125 feet past the IIP, and consisted of the fuselage, empennage, and the inboard portions of the wings. The fuselage was completely consumed by post-impact fire. Control continuity was established from the ruddervators and trim tabs to the cabin area, and aileron control cable continuity was established from the cabin area to the left and right bellcranks. The engine came to rest upright and displayed significant thermal damage. The three-bladed propeller was separated from the engine at the flange and located about 5 feet forward of the engine. The propeller blades exhibited no leading edge gouging, chordwise scratching, or s-bending. The crankshaft displayed multiple cracks aft of the propeller flange. Two breaches of the engine case were observed near the #2 and #4 cylinders. Visual examination revealed that the #2 and #4 connecting rods were fractured. The 1453 automated weather observation at CEW included winds from 300 degrees at 5 knots, 10 miles visibility, scattered clouds at 7,000 feet and 8,500 feet, temperature 37 degrees C, dew point 22 degrees C, and an altimeter setting of 29.95 inches of mercury. The pilot held a commercial pilot certificate with ratings for airplane single