In 1943, Yakovlev designed the Yak-1M which was a smaller and lighter version of the Yak-1. A second Yak-1M prototype was constructed later that year, differing from the first aircraft in plywood instead of fabric covering of the rear fuselage, mastless radio antenna, reflector gunsight and improved armor and engine cooling. The chief test pilot for the project Piotr Mikhailovich Stefanovskiy was so impressed with the new aircraft that he recommended that it should completely replace 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 theYak-3 entered service in 1944, later than the Yak-9 in spite of the lower designation number. A total of 4,848 aircraft were produced.

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.

Operational history - Source: Wikipedia
Lighter and smaller than Yak-9 but powered by the same engine, Yak-3 was a very agile dogfighter and a forgiving, easy-to-handle aircraft loved by both rookie and veteran pilots. Early combat experience found it to be superior to all Luftwaffe fighters at altitudes below 5,000 m (16,400 ft). It could roll with the Focke-Wulf Fw 190 and its turn rate was far superior; a full circle in 18.6 seconds. The two biggest drawbacks of the aircraft were its short range and the tendency of the glued-on plywood covering the top of the wings to tear away under high-G loads. The pneumatic system for actuating landing gear, flaps and brakes, typical for all Yakovlev fighters of the time was also less reliable than the hydraulic or electrical systems, but it was preferred due to significant weight savings. The first 197 Yak-3 were armed with a single 20 mm ShVAK cannon and one 12.7 mm UBS machine gun, with subsequent aircraft receiving a second UBS for a weight of fire of 2.72 kg (6.0 lb) per second using high-explosive ammunition.

Variants - Source: Wikipedia
Yak-3 - main production version

Yak-3 (VK-107A) - Klimov VK-107A engine with 1,230 kW (1,650 hp) and 2x 20 mm Berezin B-20 cannons with 120 rounds of ammunition each. After several mixed-construction prototypes, 48 all-metal production aircraft were built in 1945-1946. In spite of excellent performance (720 km/h (447 mph) at 5,750 m (18,860 ft)), VK-107 was prone to overheating and it was decided to leave the engine for the better-suited Yak-9.

Yak-3 (VK-108) - Yak-3 (VK-107A) modified with VK-108 engine with 1,380 kW (1,850 hp), and armed a single 23 mm Nudelman-Suranov NS-23 cannon with 60 rounds of ammunition. The aircraft reached 745 km/h (463 mph) at 6,290 m (20,630 ft) in testing but suffered from significant engine overheating. Another Yak-3 with 2x 20 mm Berezin B-20 cannons was also fitted with the engine with similar results.

Yak-3K - tank destroyer with a 45 mm Nudelman-Suranov NS-45 cannon, only a few built because Yak-9K was a better match for the weapon

Yak-3P - produced from April 1945 until mid-1946, armed with 3x 20 mm Berezin B-20 cannons with 120 rounds for the middle cannon and 130 rounds for each of the side weapons. The three-cannon armament with full ammunition load was actually 11 kg (24 lb) lighter than that of a standard Yak-3, and the one-second burst mass of 3.52 kg (7.74 lb) was greater than that of most contemporary fighters. Starting in August 1945, all Yak-3 were produced in the Yak-3P configuration with a total of 596 built.

Yak-3PD - high-altitude interceptor with Klimov VK-105PD engine and a single 23 mm Nudelman-Suranov NS-23 cannon with 60 rounds of ammunition, reached 13,300 m (43,625 ft) in testing but did not enter production due to unreliability of the engine.

Yak-3RD (Yak-3D) - experimental aircraft with an auxiliary Glushko RD-1 liquid-fuel rocket engine with 2,9 kN (650 lbf) of thrust in the modified tail, armed with a single 23 mm Nudelman-Suranov NS-23 cannon with 60 rounds of ammunition. On May 11, 1945, the aircraft reached 782 km/h (485 mph) at 7,800 m (25,585 ft). During the August 16 test flight, the aircraft crashed for unknown reasons, killing the test pilot V.L. Rastorguev. Like all mixed powerplant aircraft of the time, the project was abandoned in favor of turbojet engines.

Yak-3T - tank destroyer version armed with 1x 37 mm Nudelman N-37 cannon with 25 rounds and 2x 20 mm Berezin B-20S cannons with 100 rounds each. Cockpit was moved 0.4 m (1 ft 4 in) back to compensate for the heavier nose. Engine modifications required to accept the weapons resulted in serious overheating problems which were never fixed and the aircraft did not advance beyond the prototype stage.

Yak-3T-57 - single Yak-3T with a 57 mm OKB-16-57 cannon

Yak-3TK - powered by a VK-107A engine, and fitted with an exhaust turbocharger.

Yak-3U - Yak-3 fitted with Shvetsov ASh-82FN radial engine with 1,380 kW (1,850 hp) in an attempt to increase performance while avoiding the overheating problems of VK-107 and VK-108. Wingspan increased by 20 cm (8 in), wings moved 22 cm (9 in) forward, cockpit raised by 8 cm (3 in). Armament of 2x 20 mm Berezin B-20 cannons with 120 rounds per gun. The prototype reached 682 km/h (424 mph) at 6,000 m (19,680 ft) and while successful did not enter production because it was completed after the war.

Yak-3UTI - two-seat conversion trainer based on Yak-3U powered by Shvetsov ASh-21 radial piston engine. The aircraft became the prototype for the Yak-11.