Accident Sequence
On September 1, 2019, at approximately 1520 central daylight time, a Cirrus Design Corporation SR22, registration N878SR, was substantially damaged during an accident near Foley, Alabama. The pilot and three passengers were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight. According to the pilot, he completed the preflight inspection, engine run-up, and before-takeoff checks without anomalies. About 10 minutes after departure, while climbing to cruise altitude, he felt the engine buffet and then noted a loss in engine rpm. He turned the airplane back toward the airport, after which the engine lost total power and the propeller stopped rotating. He declared an emergency to air traffic control and moved the throttle to idle then full forward, but the engine did not respond. The airplane owner, seated in the front left seat, activated the airframe parachute system when the airplane reached 1,200 ft above ground level. The airplane descended via parachute and touched down upright in a field.
Wreckage Examination
Examination of the wreckage revealed that the fuselage aft of the firewall exhibited buckling and cracking, and the bottom portion of the rudder exhibited a crack about 7-8 inches in length. A borescope examination of the engine's cylinders showed valve strikes on each piston face. The propeller governor screen contained no metal, and the engine accessory drive gear for the governor would not rotate during crankshaft rotation. Upon removal of the alternator, there was no evidence of camshaft rotation when the propeller was rotated manually. The oil filter was removed and opened; metal particles were found inside the filter element.
Engine Component Findings
The engine was removed from the airframe and sent to the manufacturer's facility for further examination. Metal particles were found in the oil sump after removal. The camshaft was removed from the engine crankcase. The camshaft was intact; however, several of the camshaft gear (part number 631845) teeth were smeared or missing. Detailed metallurgical examination of the camshaft gear teeth revealed that the first three fractured teeth, located about 180 degrees from the timing mark, exhibited evidence of fatigue failure. The fracture faces of gear teeth 4 through 11 exhibited severe mechanical damage that obliterated the fracture features.
Service Bulletin History
On August 9, 2005, the engine manufacturer issued service bulletin (SB05-8), later superseded by SB05-8A in August 2009 (the revision in effect when the accident airplane's engine was overhauled in 2015), to introduce an improved camshaft gear nominally 0.060 inches wider than previous configurations. The bulletin recommended incorporation at the next engine overhaul or whenever replacement was required. In November 2009, a revised service bulletin (SB 97-6B) identified the camshaft gear as a mandatory replacement item at overhaul. In March 2017, the manufacturer elevated SB05-8B to a Category 1 mandatory service bulletin (MSB05-8B), calling for replacement within 100 hours of operation, at next overhaul (not to exceed 12 years), or whenever accessible. In July 2017, it was downgraded to Category 2 critical service bulletin CSB05-8C, recommending annual or 100-hour inspection of camshaft gears until replacement. A subsequent revision, CSB05-8D, was issued in August 2018.
Maintenance History
The airplane was manufactured in 2007 with a Continental Motors IO-550-N engine. According to Continental Motors, the original engine was equipped with the improved thicker camshaft gear per SB05-8, and the crankcase was modified with a clearance cut. In October 2015, the engine was replaced with an overhauled engine from RAM Aircraft (overhauled September 2015). The logbook entry stated the camshaft gear was inspected in accordance with "RAM Gear Inspection Specification No. 1818, Rev. L" but did not include the part number or note replacement. In April 2017, RAM distributed a service letter indicating MSB05-8B did not apply if an alternate means of compliance was referenced; the accident airplane's logbook contained such an entry. No logbook entries after the overhaul noted inspection per CSB05-8C or CSB05-8D. The most recent annual inspection, on August 29, 2019, was performed by a maintenance facility that was unfamiliar with the airplane. The facility owner stated they researched the airplane's history but did not believe CSB05-8D applied because the airplane was manufactured after the service bulletin was issued, despite the engine replacement with an older refurbished engine. In April 2020, the FAA issued Special Airworthiness Information Bulletin NE-20-05 recommending inspections of previously-manufactured camshaft gears in accordance with CSB05-8D until installation of the improved gear.