|Alan Methven, e-mail, 31.01.2009 12:13|
I think this aircraft was a development of the Itskovich KAI-1 4-passenger transport, which was designed at the Kazan Aviation Institute. UPB stands for 'Transition bomber trainer' and this was a 3-seater armed with a rear firing machine gun & carrying 160kg of bombs. First flew 11th May 1935 by B.N. Kudrin.