Accident Details
On January 2, 2020, at about 1015 eastern standard time, a Cirrus Design Corp. SR-22, registration N323SR, was substantially damaged in an accident near Kenansville, North Carolina. The commercial pilot and passenger were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot Report
The pilot reported that the departure and en route phase were normal for about 3.5 hours. While cruising at 6,500 ft mean sea level, approximately 50 nautical miles from Curtis L Brown Jr. Field Airport (EYF), Elizabethtown, North Carolina, three events occurred nearly simultaneously. The pilot heard a “pop,” then the autopilot disconnect aural alert sounded, and the airplane began decelerating. The engine was not producing forward thrust, although the propeller continued to rotate. Engine instruments indicated 1,600 RPM and exhaust gas temperature (EGT) readings of 0°F, with no other red indications. Adjusting the throttle and switching the fuel tank selector had no effect. The pilot maintained 88 knots indicated airspeed during descent. At about 2,000 ft msl, while approaching an open field, the pilot activated the Cirrus Airframe Parachute System (CAPS). After deployment, the airplane descended near vertically and struck trees, becoming partially suspended in branches. The right wing impacted terrain, and the fuselage and wings sustained substantial damage.
Data Analysis
The National Transportation Safety Board (NTSB) Vehicle Recorders Division downloaded data from the primary and multi-function displays. The data were largely consistent with the pilot’s report. Flight and engine parameters were normal until a rapid drop in EGT and oil pressure occurred in the final minutes of data. Fuel flow remained consistent, cylinder head temperatures were normal, and engine RPM slowly decreased to about 1,500 after the EGT drop.
Engine Examination
Examination of the engine revealed minor impact damage. When rotated by hand, the No. 1 and 2 cylinder intake and exhaust valves moved normally, while the remaining four cylinders showed no valve movement. Partial disassembly allowed hand rotation of the engine; the camshaft gear rotated normally with no observable wear on gear teeth. Further disassembly revealed a fractured camshaft (part number 654084, revision P). The NTSB Materials Laboratory examined the camshaft and found it had fractured between lobes associated with the No. 2 and 3 cylinders, intersecting oil transfer holes. The fracture plane was angled, consistent with fatigue under torsion loading. Forensic examination showed smooth fracture features with curving crack arrest lines emanating from origins at the corner of an oil transfer hole. Fatigue features were observed around most of the fracture surface. A portion of the fracture had post-fracture rub damage. The camshaft exterior had a dimpled appearance from shot-peening. The oil transfer hole corner was deformed inward, forming a burr, with dimple features on the burr consistent with peening deformation. Another oil transfer hole (between lobes for No. 4 and 5 cylinders) also displayed a burr but no crack. Cuts to that hole revealed an elongated texture consistent with surface deformation from burr formation.
Maintenance History
Maintenance records showed the engine was newly manufactured by Continental on July 15, 2017, and installed on the airplane by Cornerstone Aviation on August 5, 2017. The airplane underwent annual/100-hour and Cirrus Progressive inspection protocols from installation, with the most recent inspection completed on September 22, 2019. Review of endorsements from July 2017 through that inspection revealed no work involving major engine disassembly. The engine had accumulated 707 total hours.
Reference to Previous Incident
A review of NTSB accident report ERA11LA130 (January 27, 2011) involving a Cirrus SR22 with a Continental Motors IO-550-N engine and camshaft part number 654084, revision D, revealed a similar in-flight camshaft fracture. The NTSB Materials Laboratory found that fracture due to fatigue occurred at the most aft oil transfer hole. The engine had been overhauled about 393 hours prior, during which the original camshaft was replaced with a “repaired” camshaft. It was not determined whether any fatigue cracks were of detectable size at installation.