Language of Aircrew and related certificates

Julian Scarfe • 20 May 2019
in community General Aviation

A colleague tells me that the UK CAA has rejected an application for the renewal of an instrument rating on his UK-issued Part-FCL licence because the course completion certificate comes from a German ATO and the certificate (not sure if he's referring to the course completion certificate or the ATO's approval) is in the German language.

Do all certificates under the Aircrew Regulation have to be in the English language, and if not, what are the roles and responsibilities between the authorities when they are not?