like the new placement of the oil radiator, from the chin to the wing roots (one of the visual differences with the Yak-1, -7, -9). A second Yak-1M (originally meant as a "backup") prototype was constructed later that year, differing from the first aircraft in that it had plywood instead of fabric covering of the rear fuselage, mastless radio antenna, reflector gunsight and improved armour and engine cooling. After the VK-105PF2 engine received a boost from a manifold pressure of 1050 mmHg to 1100 mmHg, additional tests were needed to determine how it impacted the flight characteristics of the Yak-3. State trials revealed that this boost reduced the time needed to reach by 0.1 seconds, the takeoff run by , altitude gain in a combat loop by , and speed below by . The chief test pilot for the project Petr Mikhailovich Stefanovskiy was so impressed with the new aircraft that he recommended that it should completely replace the Yak-1 and Yak-7 with only the Yak-9 retained in production for further work with the Klimov VK-107 engine. The new fighter, designated the Yak-3, entered service in 1944, later than the Yak-9 despite the lower designation number, and by mid-1946 4,848 had been built. The designation Yak-3 was also used for other Yakovlev projects – a proposed but never built, heavy twin-engine fighter and the Yakovlev Yak-7A. The first 197 Yak-3 were lightly armed with a single motornaya pushka-mount ShVAK cannon and one UBS synchronized machine gun, with subsequent aircraft receiving a second UBS for a weight of fire of per second using high-explosive ammunition. All armament was installed close to the axis of the aircraft with a cannon mounted in the engine "vee" firing through the propeller boss, synchronised machine guns in the fuselage, helping accuracy and leaving wings unloaded. Operational history Lighter and smaller than the Yak-9 but powered by the same engine, the Yak-3 was a forgiving, easy-to-handle aircraft loved by both novice and experienced pilots. It was robust, easy to maintain and a highly successful dog-fighter. It was used mostly as a tactical fighter, flying low over battlefields and engaging in dogfights below . The new aircraft began to reach frontline units during summer 1944. Yak-3 service tests were conducted by 91st IAP of the 2nd Air Army, commanded by Lt Colonel Kovalyov, in June–July 1944. The regiment had the task of gaining air superiority. During 431