Accident Narrative
On July 14, 2017, at about 1948 mountain daylight time, a Cirrus Design Corp SR22 airplane, registration N754AP, sustained substantial damage during a forced landing in a field near Ogden, Utah. The pilot, the sole occupant, was not injured. The flight was operated as a personal flight under Title 14 Code of Federal Regulations Part 91.
According to the pilot, while established on final approach approximately 7 miles from Ogden-Hinckley Airport, he heard a loud bang followed by an engine shudder. The oil pressure then dropped to zero and the engine shut down. Believing he had lost too much altitude to deploy the airplane’s parachute, the pilot initiated a forced landing to a nearby open field. During the landing, the left wing impacted two fence posts, resulting in substantial damage to the wing.
Postaccident Data Review
Flight data downloaded from the airplane’s primary flight and multifunction displays were reviewed. The data showed that after leveling off at 12,900 ft, the airplane cruised at that altitude until 1925:00, when it began to descend. At 1942:48, the exhaust gas temperature (EGT) values for all cylinders began to decrease rapidly. Between 1943:00 and 1944:00, the EGT values for the No. 2, 4, and 6 cylinders dropped below the valid sensor input range. At 1943:00, the rpm, manifold pressure, oil pressure, and fuel flow all temporarily increased; 1 second later, these values decreased. At 1943:06, oil pressure began to decrease rapidly, reaching 0 psi at 1943:30, and did not recover before the landing.
Engine Examination
Postaccident examination of the engine revealed a large hole in the top of the crankcase between the No. 3 and 5 cylinders. All engine accessories remained attached. The oil sump was intact and contained a large amount of metallic material. The oil pickup screen was similarly contaminated. The oil pump and oil cooler showed no anomalies. The oil filter was undamaged but its internal pleats were contaminated with metallic material.
During cylinder removal, the No. 4 cylinder’s exhaust valve head was found separated from its stem, located within the engine. The valve head exhibited extensive damage consistent with repeated impact in the combustion chamber. Metallurgical examination showed the valve head and stem met hardness requirements, and several cracks were observed on the outer edge of the valve stem, though the valve body’s condition before crack formation could not be determined. The internal portion of the No. 4 cylinder sustained mechanical damage, and the piston was destroyed due to the valve head separation.
Disassembly of the crankcase revealed bearing supports with no fretting or bearing shift. The No. 1, 2, and 3 bearings were intact and undamaged with normal lubrication signatures. The No. 4 and 5 bearings showed damage consistent with lubrication distress. The crankshaft exhibited thermal damage around the No. 5 and 6 connecting rod journals and the No. 4 main journal, also consistent with lubrication distress.