The Yakovlev Yak-4 (Service names Yak-4, BB-22bis (Blizhnij Bombardirovschik, russian ближний бомбардировщик, "short-range bomber")) was a Sovietlight bomber used during World War II. It was developed from the Ya-22/Yak-2.
Design and development
The Yak-4 was an improved version of the Yak-2 with more powerful Klimov M-105 engines and a number of other changes that were made to try to rectify the problems of the Yak-2. Two additional fuel tanks were added in the outer wings to bring the total capacity up to 180 litres (40 imp gal; 48 US gal) and the gunner's canopy was bulged to give him more room to use his 7.62 mm (0.300 in) ShKAS machine gun. The upper fuselage was redesigned to improve the gunner's field of fire and the oil coolers were relocated from the sides of the engine nacelles to the 'chin' position to improve their performance.