Mandatory Service Bulletin Released for Crankshaft Counterweights

  • Update: March 15, 2023

    On March 15, 2023, the Federal Administration (FAA) issued AD 2023-05-16 that supersedes the previously released AD 2023-04-08. Effective upon publication, the new ruling document, AD 2023-05-16 includes additional engine models (IO-470-A, -C, -F, and -LO; and TSIO-360-F and -FB) and notes that the limitations in the special flight permit paragraph, specifying that “no metal contamination in the oil filter” did not account for trace metal particles that can be found in newer engines after engine break-in is performed.

    To view the most recent AD 2023-05-16 that supersedes AD 2023-04-08 and takes precedence over MSB23-01, click here.

    Released: February 23, 2023

    The Federal Aviation Administration (FAA) issued an Airworthiness Directive (AD 2023-04-08) on February 23, 2023, related to the Mandatory Service Bulletin (MSB23-01). Please be aware that AD 2023-04-08 takes precedence over MSB23-01 making the AD the governing document and rule for this issue.

    Continental recently identified a potential safety of flight issue for aircraft equipped with Continental 360, 470, 520, 550 series engines and replacement crankshaft assemblies. As the parts manufacturer, Continental reported this to the authorities and released an MSB on February 13, 2023. MSB23-01 preemptively advises that an inspection should be performed to confirm that the crankshaft counterweight retaining ring was properly installed in new and rebuilt engines assembled between June 1, 2021, and February 7, 2023. This advice also applies to replacement crankshaft assemblies manufactured between June 1, 2021, through February 7, 2023. To further clarify, the MSB stated that Continental engines with over 200 hours may continue normal flight operations; however, this is no longer valid after the release of the AD. The AD takes precedence over the MSB and now requires an inspection of all affected engines and crankshaft assemblies listed in the MSB.

    Continental Crankshaft Installation

    This page provides answers to some of the most asked questions regarding the MSB23-01 for crankshaft assemblies. Should you have additional questions, please review the full MSB or contact the Continental MSB Support Team.

    This information is subject to change. Always refer to the most recent AD and MSB. 

    Contact the MSB Support Team


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