Unfortunately my Russian is limited to the knowledge of cyrillic alphabet and to very few words. IIRC, the book of Yefimov/Gordon "Soviet Combat Aircraft" did have quite a lot about the I-16 but the "type 6" was not mentioned - IIRC, they jumped from the type 5 directly to the type 10. The type 5/6 question seems a confusing matter. What I have found from the web gives contradictory and confusing info about "tip 6" (for example the powerplant is mentioned to be "M-25A" with 730 hp or "M-25B" with 750 hp).
About the existence of "type 6" I found this source from the web claiming that about 700 were built and some of these saw action in Spanish Civil War and in China:
http://www.ctrl-c.liu.se/misc/ram/i-16-t6.html
Some model kit manufacturers have made "type 6" kits: A-model, Novo, Hasegawa.
So the "type 6" exists in the mind of many people interested in I-16 and is often used in various sources nowadays, but how long it has been around?
From various sources I have read the claim that "type 6" exists only in the literature and has been used by some researchers and authors of books to make a difference between the original type 5 and its later modifications. If such authority as Maslov does not mention such spesification as "tip 6" he must have a good reason to ignore it.
So I guess that when the "type 6" planes were manufactured they were actually labelled as "type 5" in serial production numbers. Thus back in late 1930īs the Soviets did not know and use such spesification as "type 6"...
Thus the "type 6" is a artificial creation or myth which is actually more misleading than clarifying for those interested in the history of I-16. It would be interesting to know who first used the "type 6" spesification and is the original source of its existence.
The Chinese seem to have considered the modification of type 5 as a new separate model of I-16 - labelling the modified type 5 as "I-16II" between the the "I-16I" (early type 5) and the "I-16III" (type 10 and later types). However I find it hard to believe that the Chinese would be responsible of the creation of the "type 6" spesification which is so often used in (Western) literature and web sources.