Aviation Photo #7081659 Yakovlev Yak-9U - Russia - Air Force

Yak-9U was equipped with the new 1,650 hp VK-107A engine. Early test flights in 1943 indicated that the only comparable Soviet fighter was the I-185 prototype which was more difficult to fly and less agile due to higher weight. The prototype's top speed of 700 km/h at 5,600 m was faster than any other production fighter aircraft in the world at the time, other than the P-51B. Early problems with overheating were fixed by enlarging the radiators and production aircraft had further improved aerodynamics.