AD 2017-10-11 Airworthiness Directives; Stemme AG Gliders

This AD applies to Stemme AG Model S10-VT gliders (type certificate previously held by Stemme GmbH & Co. KG), all serial numbers, that are: (1) Equipped with a front gearbox, part number (P/N) 11AG, with a serial number listed in table 1 to paragraph (c) of this AD; and (2) are certificated in any category. Table 1 to Paragraph (c) of This AD—Affected P/N 11AG (Front Gearbox) S/Ns     80058/0814 80059/0915 80060/0915 80061/1115 80062/1215 80063/0116 80064/0416 80065/0616 80066/0716 80067/0916 80068/1016 80069/0117 80070/0217 80071/0217 Note 1 to paragraph (c) of this AD: Page 2 of Stemme AG Service Bulletin No. P062-980010, dated April 21, 2017, provides a pictorial of where the serial number of the affected gearboxes are located.

Unless already done, do the following actions. (1) Before further flight after June 15, 2017 (the effective date of this AD), replace the front gearbox following a method approved specifically for this AD by the FAA, Small Airplane Directorate. Contact the FAA using the information in paragraph (g)(1) of this AD to obtain FAA-approved repair instructions approved specifically for compliance with this AD and incorporate those instructions. Note 2 to paragraph (f)(1) of this AD: At the issue date of this AD, no design solution is available to restore the airworthiness of the respective type design to a level corresponding to its approved type design specifications. (2) As of June 15, 2017 (the effective date of this AD), do not install a front gear box listed in paragraph (c) of this AD.

The following provisions also apply to this AD: (1) Alternative Methods of Compliance (AMOCs): The Manager, Standards Office, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. Send information to ATTN: Jim Rutherford, Aerospace Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106; telephone: (816) 329-4165; fax: (816) 329-4090; email: jim.rutherford@faa.gov. Before using any approved AMOC on any glider to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO. (2) Airworthy Product: For any requirement in this AD to obtain corrective actions from a manufacturer or other source, use these actions if they are FAA-approved. Corrective actions are considered FAA-approved if they are approved by the State of Design Authority (or their delegated agent). You are required to assure the product is airworthy before it is returned to service.

This AD was prompted by mandatory continuing airworthiness information (MCAI) issued by the aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as certain propeller front transmission gear wheels having insufficient material strength because of improper heat treatment during manufacturing. We are issuing this AD to prevent failure of the propeller front transmission gear wheels. This failure could cause loss of power between the engine and the propeller, which could result in reduced control.

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