FAA has issued airworthiness directive 2021-12-02 for certain De Havilland Aircraft of Canada DHC-8-400s, requiring, depending on airplane configuration, removing the fasteners on the nacelle A-frame side brace sub-assemblies, doing an eddy current inspection for cracking, cold-working the holes, installing oversize fasteners, re-identifying the reworked side brace fitting and A-frame, and repair if necessary, effective July 20, 2021.