The Yakovlev Yak-11, NATO codename ?Moose?, was developed from the Yak-3 fighter as a two-seat intermediate and advanced trainer. It first flew in 1945 and entered production the following year. By the time production ended, Yakovlev had built almost 4,000, and several hundred were also built under licence by LET of Poland and Czechoslovakia?s Strojviny Privni Petiletsky. Licence-built aircraft were designated C-11 AND G-BTUB is actually a C-11 built in 1956 at Czechoslovakia?s LET factory. After service with the Czech air force, it was sold to Egypt and served with the Egyptian air force before being struck off charge. en, rebuilt the Shnetsov Ash-21 engine.