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When a plane is flown as a 415-C, the type certificate under which it is "certificated" is A-718. When the plane was born as a 415-D, 415-CD, or later, OR is an earlier serial number converted according to the requirements in A-787, then the type certificate under which it is certificated is A-787. When the conversion is done, there are specific things you have to do, including changing the aircraft's data plate (Crossing out the letter C or CD and stamping the letter D). Certainly a log book entry is required.
