Cirrus Design Corp SR22T N927CS incident near Bellevue, Washington

Probable cause

A total loss of engine power due to a fatigue fracture of the crankshaft.

NTSB analysis

The flight crew reported that shortly after leveling off, the engine rpm surged a few times, followed by the sound of a loud bang and subsequent total loss of engine power. Unable to restart the engine, they successfully deployed the Cirrus Airframe Parachute System (CAPS) and descended under the parachute into a wooded wetland area adjacent to a residential neighborhood.

Examination of the engine revealed that the crankshaft was fractured between the No. 2 main bearing journal (M2) and the No. 3 connecting rod (C3) journal. Fretting was observed on the parting surface of the No. 2 main bearing saddle. The No. 2 main bearing saddle remained in place and was deformed, consistent with a rotating main bearing. Damage to the interior engine case was observed throughout. The crankshaft near the M2 journal and the No. 3 connecting rod journal was fracture separated.

Metallurgical examination of the crankshaft fracture revealed fatigue cracking that initiated at multiple sites along the radius of the web with the C3 journal. As this crack propagated aftward, a second smaller fatigue crack began along the radius of the aft M2 bearing. It is likely that as the crack continued to grow in depth, it allowed the remainder of the crankshaft to fracture from overstress and subsequent failure. The postfracture damage was due to the fractured surfaces of the crankshaft, between the C3 and M2, that continued to make contact with each other during the accident sequence. Due to the damage to the M2 bearing, the No. 2 main bearing saddle, and the fracture surface of the crankshaft on the M2 bearing side, it could not be determined if bearing slippage was the initiating event. The fatigue fracture of the crankshaft likely led to the total loss of engine power.

Text from the NTSB. Open the NTSB docket for WPR24FA103 for the full record.