Yakovlev OKB created 22 modifications of the Yak-9, of which 15 saw mass production. The most notable of these include:
Yak-9 – First production version, Klimov M-105PF engine with 880 kW (1,180 hp), 1 × 20 mm (0.79 in) ShVAK cannon with 120 rounds and 1 × 12.7 mm (0.50 in) UBS machine gun with 200 rounds.
Yak-9 (M-106) – Prototype with Klimov M-106-1SK engine with 1,007 kW (1,350 hp), did not advance to production because of problems with the engine.
Yak-9T – Yak-9 armed with a 37 mm (1.5 in) Nudelman-Suranov NS-37 cannon with 30 rounds instead of the 20 mm (0.79 in) ShVAK, cockpit moved 0.4 m (16 in) back to compensate for the heavier nose.
Initially poor quality control led to multiple oil and coolant leaks from cannon recoil.
It was a problem only during the prototype tests)Recoil and limited supply of ammunition required accurate aiming and two-three round bursts.
Yak-9T was widely used against enemy shipping on the Black Sea and against tanks (the cannon could penetrate up to 30 mm (1.2 in) armour from 500 m (1,600 ft), but was also successful against aircraft with a single cannon hit usually sufficient to tear apart the target.
Virage (constant altitude and velocity turn) time: 18–19 seconds. 2748 were produced.
Yak-9K – Yak-9T modified with a 45 mm NS-45 cannon with 29 rounds and a distinctive muzzle brake to deal with the massive recoil.
Firing the cannon at speeds below 350 km/h (220 mph) caused dramatic loss of control and tossed the pilot back and forth in the cockpit; however, accurate shooting was possible at higher speeds and in 2–3 round bursts.
The recoil also caused numerous oil and coolant leaks.
The heavy cannon installation degraded performance, even more so at high altitudes, sufficiently to relegating the Yak-9K to be used as a heavy fighter and resulting in the need for a fighter escort of Yak-3s.
The Yak-9K saw only limited use due to unreliability of the NS-45, airframe performance issues caused by both the NS-45 and larger fuel tanks used on the Yak-9K, as well as a reduction of bombers used by the Germans.
Yak-9D – Long-range version of Yak-9, fuel capacity increased from 440 to 650 L (120 to 170 US gal) to giving a maximum range of 1,400 km (870 mi).
Combat usefulness at full range was limited by lack of radio navigation equipment, and a number of aircraft were used as short-range fighters with fuel carried only in inner wing tanks.
Circle time: 19–20 sec. Weight of fire: 2 kg/s (4.4 lb/s).
Yak-9TD – Yak-9D with NS-37 cannon and provision for 4 × 50 kg (110 lb) FAB-50 bombs under the wings.
Yak-9B – Fighter-bomber version of Yak-9D (factory designation Yak-9L) with four vertical tube bomb bays aft of the cockpit with capacity for up to 4 × 100 kg (220 lb) FAB-100 bombs or 4 PTAB cassettes with 32 × 1.5 kg (3.3 lb) bomblets each, although normally only 200 kg (440 lb) of weapons were carried in the front bomb bays.
Poor handling with a full bomb and fuel load and lack of special aiming equipment limited combat usefulness.
Yak-9DD – Yak-9D and Yak-9T modified to further increase the range, fuel capacity increased to 845 L (223 US gal) giving a maximum range of 2,285 km (1,420 mi), radio navigation equipment for night and poor weather flying.
Yak-9DD were used primarily to escort Petlyakov Pe-2 and Tupolev Tu-2 bombers although they proved less than ideal for this role due to insufficient speed advantage over the bombers.
In 1944, several Yak-9DD were used to escort B-17 Flying Fortress and B-24 Liberator bombers attacking targets in Romania using the Ukraine-Romania-Italy routes.
Yak-9M – Yak-9D with the cockpit moved 0.4 m (1 ft 4 in) to the rear like on Yak-9T, numerous fixes and improvements based on experience with previous versions.
Yak-9M PVO – Yak-9M with slightly reduced fuel capacity, Klimov VK-105PF2 engine with 925 kW (1,240 hp), and radio and navigational equipment for night and adverse weather flying for PVO Strany.
Yak-9 MPVO – Single-seat night fighter aircraft, equipped with a searchlight and an RPK-10 radio compass.
Yak-9S – Yak-9M with Klimov VK-105PF engine, new propeller, and armament consisting of 1 × 23 mm (0.91 in) Nudelman-Suranov NS-23 cannon with 60 rounds, and 2 × 20 mm (0.79 in) Berezin B-20 cannons with 120 rounds.
Did not enter production due to poor performance compared to Yak-3 and Yak-9U.
Yak-9P – This aircraft was the last and the most advanced version of the Yak-9 fighter, which became the pinnacle of development among A. S. Yakovlev’s piston-engined fighters.
The Yak-9P (Product P) that appeared in 1946 was a modification of the Yak-9U fighter of composite construction. Unlike its predecessor, it had all-metal wings with elliptical tips.
By this time, the manufacture of high-strength aluminium alloys was established in the Soviet Union, simplifying aircraft operation and increasing aircraft service life.
Yak-9PD – High-altitude interceptor (unrelated to the two other Yak-9P above) with Klimov M-105PD engine designed specifically to intercept Luftwaffe Junkers Ju 86P high-altitude reconnaissance aircraft overflying Moscow in 1942–1943.
Initially poor performance due to unreliable engine dramatically improved with adoption of Klimov M-106PV with water injection, with the aircraft reaching 13,500 m (44,300 ft) during testing.
Armament reduced to the ShVAK cannon only to save weight.
Yak-9T with Klimov VK-105PF2 engine and numerous aerodynamic and structural improvements introduced on Yak-3.
Main visual difference from Yak-9T was in the oil coolers in the wing roots like on Yak-3 and in plywood covering of the fuselage instead of fabric.
Visually differed from Yak-3 only by main landing gear covers.
Armament increased to 1 × 23 mm (0.91 in) VYa with 60 rounds and 2 × 12.7 mm (0.50 in) UBSs with 170 rpg.
The VYa cannon could be replaced by a ShVAK, B-20, or NS-37, the latter requiring removal of the starboard UBS machine gun.
Did not enter production because the VYa cannon was considered unsatisfactory and because the one cannon, one machine gun armament seen on previous models offered a significant increase in range.
Yak-9U (VK-107) – The definitive Yak-9 variant, Yak-9U (VK-105) equipped with the new Klimov VK-107A engine with 1,230 kW (1,650 hp), and the 20 mm (0.79 in) ShVAK with 120 rounds replacing the VYa. Weight of fire: 2.72 kg/s (6.0 lb/s).
Early test flights in 1943 indicated that the only comparable Soviet fighter was Polikarpov 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 (430 mph) at 5,600 m (18,400 ft) was faster than any other production fighter aircraft in the world at the time, other than the P-51B that could reach up to 710 km/h (441 mph) on military power.
Early problems with overheating were fixed by enlarging the radiators and production aircraft had further improved aerodynamics.
Turning ability to complete a circle: 23 sec, best Soviet fighter at altitude.
Yak-9UV – Two-seat trainer version of Yak-9U (VK-107), armament reduced to a single Berezin B-20 cannon with 100 rounds.
Did not enter production due to introduction of jet aircraft.
Yak-9UT – Yak-9U (VK-107) armed with 1 × 37 mm (1.5 in) Nudelman N-37 cannon with 30 rounds and 2 x 20 mm (0.79 in) Berezin B-20 cannons with 120 rpg, giving a total one-second burst mass of 6 kg (13 lb). Similarly to the Yak-9TK, it could be converted to replace the N-37 with a 20 mm (0.79 in) B-20, 23 mm (0.91 in) NS-23, or 45 mm (1.8 in) N-45.
Production aircraft carried NS-23 instead of the N-37 cannon as the default armament.
Yak-9-57 – The Yak-9-57 was a one-off conversion of a Yak-9UT armed with a 57 mm cannon.
The large calibre cannon did not protrude out from the spinner cone like the Yak-9-37/45 models.
Yak-9V – Two-seat trainer version of Yak-9M and Yak-9T, Klimov VK-105PF2 engine, armament reduced to 1 × 20 mm (0.79 in) ShVAK with 90 rounds.
Modern replicas – In the early 1990s, Yakovlev started limited production for the warbird market of Yak-9 and Yak-3 replica aircraft using original World War II equipment and Allison V-1710 engines.
These modern-built replicas using the Allison engines, have counter clockwise-rotation props, unlike the originals which strictly used clockwise-rotation Soviet V12 powerplants.