Incident Overview
On March 5, 2024, at approximately 1704 Pacific standard time, a Cirrus SR-22T, registration N927CS, sustained minor damage during an incident near Bellevue, Washington. The flight instructor and the pilot receiving instruction were not injured. The airplane was being operated as a Title 14 Code of Federal Regulations Part 91 instructional flight.
According to the flight instructor and the pilot receiving instruction, after takeoff from runway 34 at Renton Municipal Airport, the airplane leveled off at about 2,500 feet mean sea level (msl). A few minutes later, the engine rpm surged several times, followed by a loud bang and a subsequent total loss of engine power. Unable to restart the engine, they deployed the Cirrus Airframe Parachute System (CAPS), and the airplane descended under parachute into a wooded wetland area adjacent to a residential neighborhood.
Wreckage and Site Information
Examination of the incident site revealed that the airplane impacted terrain approximately 4 miles northeast of the departure end of runway 34. The airplane came to rest upright in an approximate 10° nose-low attitude on a heading of about 066° magnetic at an elevation of about 417 feet msl.
Examination of the recovered wreckage revealed damage to the nose landing gear fairing. Both wings and flaps were removed by recovery personnel. The engine remained attached to the fuselage via the engine mount. All six cylinders and all engine accessories remained attached. All fuel and oil lines appeared attached to their respective fittings. No evidence of any mechanical damage was observed to the engine crankcase. Throttle and mixture control continuity was established from the cockpit controls to the fuel servo and moved its available length when actuated by hand.
Engine Examination
Review of the airframe and engine logbooks revealed that the engine, a Continental Motors TSIO-550-K1B, was overhauled in November 2019 and installed on the airframe in April 2020. At the time of the incident, the engine had accumulated about 680 hours since major overhaul.
The engine was shipped to Continental Motors Inc. facilities for further examination. Subsequent examination revealed that all six cylinders remained attached to the engine crankcase; no external visible damage was observed. The engine was placed on a rotating engine stand and disassembled. Fretting was observed on the parting surface of the No. 2 main bearing saddle. Damage to the No. 3 and No. 4 cylinder barrel skirts was observed. The No. 2 main bearing (M2) saddle remained in place and was deformed, consistent with a rotating main bearing. The engine was further disassembled to access the crankshaft and rotating mass. Damage to the interior crankcase was observed throughout. The crankshaft near the M2 journal and the No. 3 connecting rod journal was fracture separated.
The crankshaft was sent to the NTSB Materials Laboratory in Washington, DC, for examination. The examination of the fracture surface revealed characteristics consistent with fatigue cracking that initiated at multiple locations along the radius of the web within the C3 journal. As this crack propagated rearward, a second smaller fatigue crack initiated along the radius of the aft M2 bearing. Review of maintenance records did not reveal any recent maintenance performed on the crankshaft.