Source: http://s362974870.onlinehome.us/forums/air/index.php?showtopic=263859&pid=2503073&st=0entry2503073
About the DB-3: http://en.wikipedia.org/wiki/Ilyushin_DB-3
About the Il-4 : http://en.wikipedia.org/wiki/Ilyushin_Il-4
Xuntong homepage: http://www.xtmodel.com.cn/a/English/
V.P.