XPLM_API XPLMNavRef XPLMFindLastNavAidOfType( XPLMNavType inType);
This routine returns the ref of the last navaid of the given type in the database or XPLM_NAV_NOT_FOUND if there are no navaids of that type in the database. You must pass exactly one nav aid type to this routine.
WARNING: due to a bug in the SDK, when fix loading is disabled in the rendering settings screen, calling this routine with fixes returns a bogus nav aid. Using this nav aid can crash x-plane.