With nearly 17,000 Yak-9s produced, the Yak-9 defined the Yakovlev fighter. Initially, the Yak-9 retained the razor-back cockpit of the Yak-1 and Yak-7. The fighter proved easily modified for a number of combat roles including: low altitude, light tactical fighter, fighter-bomber, long-range escort, and high altitude reconnaissance. Modifications included a variety of armament choices, different engines, and two or four fuel tanks. The aircraft variant used depended on the mission.
Early Yak-9s suffered a variety of production deficiencies including wing warping, and skin pealing due to breaches in bonding techniques and materials. This problem occasionally led to loss of the aircraft and/or pilot.
The Yak-9 first flew on 6 July, 1942, with production beginning in October 1942. These aircraft went to reserve regiments and training centers under the supreme command reserve. They first saw combat in the second half of December 1942.
The Yak-9D, long range fighter, saw an increase in fuel tanks from two to four located in the wings between the wing spars. More than 3,000 Yak-9Ds were built from March 1943 to June 1946, and first saw combat on 12 July, 1943, in the Orel area during the Soviet counter-offensive in the Kursk bulge. Although slower than enemy fighters, the Yak-9D held an advantage over the Fw 190A-4 and the Bf 109G-6 in horizontal maneuverability.
Closely following the Yak-9D came the Yak-9T, tank buster. Built between March 1943 and June 1945, this aircraft earned high praise from the pilots who flew it. Initially it carried a 37 mm cannon firing through the propeller boss. Engineers moved the cockpit of the production model aft because the weight of the cannon affected the machine’s center of gravity. The longer nose did not affect visibility on landing. The aircraft carried only thirty to thirty-two rounds for the 37 mm so pilots limited a burst to one to three rounds. Later variants carried a 45 mm cannon.
Thirty-five Yak-9Ts were used for combat evaluation during the battle of the Kursk Salient from 5 July to 6 August, 1943. Assigned to the 16th Air Army, these machines broke up bomber formations and then destroyed the bombers individually. Pilots flying the Focke Wulf 190, itself equipped with a formidable armament, avoided head on attacks with Yak-9Ts. Production of the Yak-9T ran from March 1943 to June 1945 and totaled 2,748 machines.
Yak-9s replaced Yak-1s, Yak-7s, LaGG-3s, and Polikarpov as production allowed. By mid-1944 the Yak-9 outnumbered all other fighters in the Soviet Air Force inventory.
Source: Yakovlev Fighters of World War Two, Yefim Gordon, Sergey Komissarov, and Dmitriy Komissarov, Hikoki Publications, Manchester, England, 2015