Because of the debate over variants that is raging in certain threads, I think it is appropriate to post a thread about what exactly IS a variant of a plane.
Not all nationalities treat vairants the same way. In some countries, a plane might recieve major design changes yet be calassified as the same plane. Conversely, in a different country, two identical planes might be classified as "variants" of each other.
What it boils down to is that whether a plane is a "vairant" or a new model seems to depend on what country and which brance of service the plane in question is in. There doesn't seem to be any set pattern.
The U.S. Army seems to use production contracts (as well as airframe changes) as a basis for classifying planes. Hence, the P-51B and P-51C are indentical planes, yet are considered variants. Early and late model P-47D's are quite different but are the "same" plane because they were under the same contract. The U.S. navy takes it one steop further; it applies a totally different designation to a plane made by another company. As a result, some "variants" appear, on paper, to be totally different planes--like the F4F and the FM2.
Germany, on the other hand, seems to have had a classification system based upon engine and intended role of the plane. Hence, the Bf-109F and Bf-109G are variants, although the only major difference is the engine. Likewise, the FW-190A and FW-190F are almost the same plane, but are intended for different roles.
The UK is even more haphazard. Take the Spitfire, for example. Between the Mk. 5 and the Mk. 9, the only major difference was an engine change. Yet many Spitfire 9's had different engine versions than others, without recieving a new mark number.
Personally, I think whether a plane is a "variant" or not seems to depend more on political factors than on the plane itself.
J_A_B
