Accident Summary
On December 31, 2023, at about 1315 central standard time, a Cirrus SR22T, registration N773GB, sustained substantial damage during a forced landing in a corn field near Davenport, Iowa. The pilot and passenger were not injured. The flight was a personal operation under Title 14 Code of Federal Regulations Part 91.
The pilot reported that while descending to land at Davenport Municipal Airport (DVN), the engine began to run rough. The No. 5 cylinder indicated a lower temperature than other cylinders, and oil pressure was decreasing. An abrupt engine noise and power loss occurred, accompanied by smoke from the engine cowling and oil splattering on the windscreen. Total engine power was lost, and the pilot executed a forced landing. During the landing, the landing gear collapsed and both wings incurred substantial damage.
Postaccident Examination
Examination of the engine revealed a fracture of the No. 5 cylinder in the area near the exhaust rocker arm. This led to separation of a portion of the cylinder head casting and rocker arm assembly. Other engine components, including the No. 3 and No. 4 cylinder connecting rods, showed evidence of failure consistent with lack of lubrication.
The aircraft was powered by a Continental Aerospace Technologies (CAT) model TSI0550K1B engine. The failed cylinder head, part number 658595, was subject to Airworthiness Directive (AD) 2020-16-11, which required compliance with CAT Mandatory Service Bulletin (MSB) 18-08. Maintenance records indicated that the cylinder had been removed, repaired, and reinstalled on February 26, 2021, with compliance noted to AD 2020-16-11. At that time, MSB18-08 revision B was current. The remaining five cylinders were not subject to the AD.
Examination of Cylinders
The broken cylinder from the accident aircraft, along with two cylinders from other aircraft that had experienced similar fractures, were examined by the NTSB Materials Laboratory. All three showed evidence of attempts to comply with MSB18-08. The MSB required cylinders to be inspected and modified to remove casting flash or sharp radius edge conditions.
For the accident cylinder, material removal and blending was observed in the area specified by the MSB, extending approximately 0.15 inches underneath the ear and 0.12 inches deep into the rocker box footing. The MSB specified that blending should extend about 0.25 inches under the ear.
On the second cylinder, blending did not reach the internal edge on the underside of the ear. A sharp outer edge remained, extending about 0.06 inches from the corner.
The third cylinder showed rounding of the outer edge consistent with filing, blending extending up to 0.24 inches under the ear and 0.10 inches deep. This cylinder had a fracture but the rocker box ear had not fully separated.
All three cylinders exhibited fracture surface features consistent with high-cycle fatigue, with origins in the area identified in MSB18-08 for blending.