AD FAA-2017-0451

We are adopting a new airworthiness directive (AD) for Stemme AG Model S10-VT gliders (type certificate previously held by Stemme GmbH & Co. KG). This AD results from 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 require actions to address the unsafe condition on these products.