I have seen some Shorts Skyvan aircraft advertised or described as being version Skyvan "3-300" or "3A-300".
Since the only certified Skyvan versions are 3-100 and 3-200, what is a 3-300? Are they some sort of uncertified modification?
Also, what is a Skyvan "3-400"? Is this a de-militarised 3M-400? Again, this does not appear to be a certified version, how is it allowed to fly?