N764CT

On June 19, 2018, about 1200 mountain standard time, a Cirrus SR22, N764CT, was destroyed when it was involved in an accident near Aguila, Arizona. The pilot was seriously injured, and the passenger received minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

According to the pilot, at approximately the halfway point of his cross-country flight, the oil temperature increased past the highest limit on the oil gauge. The oil pressure then dropped to between 14 and 16 pounds per square inch (psi), and the airplane began to shudder “violently.”

The pilot turned the airplane toward the closest airport, about 40 miles away. While en route, the engine speed increased to over 5,000 rpm then dropped to almost 0 rpm. The pilot reported he was having a difficult time maintaining an altitude of 6,500 ft mean sea level and knew he would not be able to clear a nearby mountain range. As he looked for an area to make an emergency landing, the engine “completely seized.” The pilot reported the cabin then filled with smoke and oil covered the windshield. He deployed the airplane’s parachute system, and the airplane landed about 5 seconds later in a ravine. After landing, the airplane was consumed by fire.

An initial examination of the engine revealed the No. 2 connecting rod had punctured the top aft section of the crankcase. The rusted crankshaft was visible through the hole, as were the remains of the separated No. 2 connecting rod. The spark plugs were removed, and heavy erosion was observed on the electrodes; the insulators were fractured and missing significant portions. Borescope examination of the cylinders revealed signatures consistent with elevated temperatures on the pistons. The No. 5 piston was eroded around the outer circumference and there was a hole present with a portion of the top piston ring visible. Additionally, examination of the exhaust system revealed re-solidified melted metal particles, consistent with the postaccident fire.

The engine was completely disassembled for further examination. This examination revealed the Nos. 2, and 5 pistons experienced a pre-ignition/detonation event that partially eroded the pistons and resulted in oil starvation of the engine. The cause of the pre-ignition/detonation event could not be determined. Due to the severe fire damage, many of the engine components could not be tested, including the magnetos.

According to the engine maintenance records, a magneto-to-engine timing check was conducted many times, with the most recent check before the accident dated July 27, 2012; an annual inspection was performed May 9, 2018, at a total time of 1,955.4 hours with no anomalies noted. However, the required 500-hour inspection of the magnetos was not indicated in the maintenance records since their last comprehensive inspection in 2011. The magnetos had accumulated 1,284.1 hours since 2011.