The Yakovlev UT-2 was a trainer aircraft used by the Soviet Air Force from 1937 until the 1950s. It was the standard Soviet trainer during World War II.
To improve handling and stability, a new UT-2M (modernized) variant was developed in 1941 and put into production. The shape of wings was totally new, with a swept leading edge instead of a straight one (the wing's trailing edge was now straight), and the tailfin was larger.
In total, 7,243 UT-2 and -2Ms were produced in five factories between 1937 and 1946. Despite all improvements, the handling and flight characteristics of the UT-2 were never excellent.
Info: Wikipedia
http://en.wikipedia.org/wiki/Yakovlev_UT-2
Profile: Wings Palette
http://wp.scn.ru/en/