On Feb. 17, Continental released Mandatory Service Bulleting MSB23-01A regarding a possible error in the assembly of crankshaft counterweights in certain Continental engines with less than 200 operating hours. It is possible one or more counterweight retaining rings were not properly seated in the crankshaft counterweight groove. This condition could allow the counterweight to depart from the crankshaft during engine operation resulting in catastrophic engine damage. Approximately 2,000 crankshaft assemblies may be affected.

The MSB requires crankshafts to be inspected for proper counterweight installation. For affected engines with less than 200 operating hours, inspection should take place immediately. If necessary, an additional five flight hours is acceptable to move to a maintenance facility with minimum essential crew. Compliance time begins upon receipt of the Service Bulletin. For engines with more than 200 operating hours, no action is required.

The engines and crankshaft assemblies affected are identified in the MSB by the by serial number in Appendix 1 (engines) and Appendix 2 (crankshaft assemblies sold as replacement parts). Only the engine or crankshaft assembly serial numbers listed in the two tables are subject to inspection. Inspection is not required on engines and crankshaft assemblies not included in the two tables. 

The PDF of the complete Mandatory Service Bulletin (MSB) is available to download here.