At the last annual we mistakenly thought the metal tube fiberglassed over the rudder control rod was covering up some hidden damage. It was only after removing the tube we discovered it was in fact an approved modification. Oops!! To cut a very long story short we were unable to source replacement tubing to Airbus specification and a new rod had to be fabricated. Not all Bölkow 207’s have this modification, I think later parts didn’t need strengthening.