N754AP

On July 14, 2017, about 1948 mountain daylight time, a Cirrus Design Corp SR22 airplane, N754AP, sustained substantial damage when it was involved in an accident near Ogden, Utah. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, he was established on the final approach, about 7 miles from Ogden-Hinckley Airport, Ogden, Utah, when he heard a loud bang then felt a shudder from the engine. Subsequently, the engine’s oil pressure decreased to zero and the engine shut down. At this point, having lost altitude and believing that he was too low to deploy the airplane’s parachute, the pilot initiated a forced landing to a nearby open field. During the landing sequence, the airplane’s left wing impacted two fence posts, resulting in substantial damage to the wing.

Postaccident review of the airplane’s flight data (downloaded from the its primary flight and multifunction displays) revealed that, after leveling off at 12,900 ft, the airplane cruised at that altitude until 1925:00, when it started to descend. At 1942:48, The exhaust gas temperature (EGT) values for all the 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 range of the sensor input. At 1943:00, the rpm, manifold pressure, oil pressure, and fuel flow values all temporarily increased and, 1 second later, these values decreased. At 1943:06, the oil pressure began to rapidly decrease. At 1943:30, the oil pressure indicated 0 psi and did not recover before the landing in the field.

Examination of the engine revealed no noticeable impact damage, but a large hole in the top of the crankcase between the Nos. 3 and 5 cylinders was observed. All engine accessories were attached to the engine. The oil sump was intact, and a large amount of metallic material had collected within the sump. The oil pickup screen had a large amount of metallic material on the screen. The oil pump was removed and examined, and no anomalies were noted. The oil filter remained securely attached and was undamaged. Removal of the oil filter found its internal pleats were contaminated with metallic material. Examination of the oil cooler found no anomalies.

During removal of the cylinders, it was noted that the No. 4 cylinder’s exhaust valve head was separated from the valve stem and was located within the engine. The valve head sustained extensive damage consistent with repeated impact in the combustion chamber. Metallurgy examination of the valve head and stem revealed that they met hardness requirements. Several cracks were also observed on the outer edge of the valve stem; however, the valve body’s condition before the crack formation could not be determined due to the condition of the valve head and stem. Further examination revealed that the internal portion of the No. 4 cylinder sustained mechanical damage and the piston was destroyed from the valve head separation.

The disassembly of the engine crankcase uncovered all the bearing supports. Examination of the supports revealed no signs of fretting or bearing shift. The Nos. 1, 2, and 3 bearings were intact, undamaged, and exhibited normal operating and lubrication signatures. The Nos. 4 and 5 bearings exhibited damage consistent with lubrication distress. The crankshaft displayed thermal damage signatures around the Nos. 5 and 6 connecting rod journals and the No. 4 main journal that were consistent with lubrication distress.