AD FAA-2013-0220

We are superseding an existing airworthiness directive (AD) for all Slingsby Sailplanes Ltd. Models Dart T.51, Dart T.51/17, and Dart T.51/17R sailplanes equipped with aluminum alloy spar booms. This AD results from mandatory continuing airworthiness information (MCAI) issued by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as an incident of glue joint failure on a starboard wing caused by water entering the area of the airbrake box that resulted in delamination and corrosion in the area of the aluminum alloy spar booms and the wing attach fittings. We are issuing this AD to require actions to address the unsafe condition on these products.