Aviation of World War II
In late 1942 service experience of the Yak-7 led to the call for increased fighter range. Thus a Yak-7B was modified with the provision for only one UBS machine gun and the addition of metal wing spars. Extended capacity fuel tanks were fitted into the larger volume of the inner wing. Furthermore, the rear fuselage fairing was removed and the aircraft was fitted with a bubble-top canopy (as per the Yak-1 В fighter). Named Yak-7DI, the aircraft had a cruising range of about 1,310 km using the M-105Pf engine (as compared with the Yak-7B's mere 900 km). The new aircraft entered serial production under designation "Yak-9" at Plant #153 in Novosibirsk.
The first serial Yak-9s were powered with the M105Pf liquid cooled engine and VISh-61P controllable propeller. They differed externally from the prototype in having the one-piece main landing gear (MLG) doors, convex cockpit canopy, moved slightly forward, conventional exhaust pipes placed between upper and lower plates, convex shape oil cooler, rectangular supercharger wing-root air intake, a mechanical gun sight and double-wire aerial. The Yak-9 possessed two fuel tanks with a total capacity of 320 kg and 26-30 kg oil tank. There were no bomb racks beneath the wing. The armament comprised 20 mm ShVAK canon with 120 shells and 12,7 UBS machine gun with 200 shells. Having a maximum takeoff weight about 2875 kg, the Yak-9 could attain a maximum speed of 602 km/h at 4,300 m altitude. Production Yak-9s were initially allocated to units taking part in the Battle of Stalingrad in late December 1942. A total of 459 Yak-9s were produced by the Siberian Plants # 166 and # 153.
In 1942 the aerodynamic performance of the Yak-9 was improved by fitting the M-106 engine but it did not result in serial production due to the M-106's unreliability.
The introduction of additional fuel tanks and larger oil tank was intended as an improvement to the aircraft's flight range characteristics. The Yak-9D powered with M-105PF engine, featured four 650L common volume fuel tanks and 48 kg oil tank. Having the same armament as the Yak-9 had, the Yak-9D showed flight radius of 1,360 km and maximum takeoff weight of 3,117 kg. However, usually because of weak radio equipment performance, the aircraft were not used with full fuel tanks. The long range capability was employed for bomber escort missions only. A total of 3058 Yak-9Ds were produced from March 1943 till June 1946.
The Yak-9P featured the second 20 mm ShVAK cannon in place of UBS machine gun. The second cannon had as ammunition 165 shells. Having been rolled out in March 1943 it went to the Air Force Research Institute for evaluation from March 17, 1943 until April 8, 1943. Powered by the M-105 PF engine, the aircraft was equal to Yak-9's flight performance, however it did not see serial production because of aiming difficulties.
The Yak-9 TK powered with same engine could be fitted with different types of cannon while in service. The aircraft's design enabled the installation of 23 mm VYa-23, 37 mm NS-37 or 45 mm HS-45 canon. This experimental «transporter» was tested at Air Force Research Institute in October 1943, but it was not adopted for serial production.
In the winter of 1943/4 the Yakovlev design bureau decided to greatly improve the aircraft's fire power by installing the 45mm HS-45 cannon, with the intention of creating the ultimate Yak-9. The cannon featured barrel brake and had ammunition of shells. Furthermore the aircraft was fitted with a bullet-proof windscreen and AFT armored glass. But the VK-105PF engine was not powerful enough for a take off weight of 3,028 kg. Compared to the earlier Yak-9s, the new fighter's speed was 27-40 km/h lower. The rate of climb dropped too. A total of 53 Yak-9K's was produced in April-June 1944. Soviet pilots enjoyed flying the new aircraft but the Yak-9K was only used during the final period of the war in the hands of skilled pilots, who had previously flown the Yak-9T.
The introduction of the M-105PD engine with E-100V supercharger was intended as an improvement for the aircraft's high altitude characteristics. Yakovlev received an order for five Yak-9PD's on 12 November 1942. They were allocated to the 12th Guard Fighter Wing for evaluation trials which were disappointing. Armed with 20mm ShVAK canon (120 shells) aircraft had a maximum ceiling of 11,650 m. The improved M-105 PD powered Yak-9 was also unsuccessful on its trials at the Flight Research Institute on 3 August - 18 October, 1943. The maximum altitude was only 12,500 m. The M-105PD engine was eventually replaced by the M-106 PV. It enabled the aircraft to show a service ceiling of 13,000 m on 15-18 September 1943. But very high engines temperatures precluded the aircraft serving from in Red Army Air Force. In 1944 the Yak-9U was created. It climbed to altitudes of 12,800 т and even 13,500 m. Powered by the M-106 PV engine with a methanol/water injection system, new ignition system and VISh-105 TL lightened propeller, the aircraft reached a speed of 620 km/h at 10,500 m. It took 25 min to reach 11,000 m altitude. The Yak-9U was armed with Sha-20 M super light canon (60 shells), it featured a 50% reduction in fuel capacity and the removal of some structural features , e.g. split flaps. The Yak-9U flew until the end of the war without gaining any significant combat experience.
The Yak-9R variant had a camera and mechanically controlled shutter in the lower fuselage. The control unit was placed in the starboard side of the cockpit. The Yak-9R short-range version was produced by serial plants or modified in the field. Built at Plant #166 in Omsk in 1943, the first aircraft was evaluated from 21 September until 10 October 1943. (The pilot was A.Prochakov, the engineer was G.Sedov). Equipped with the AFA-IM camera, the aircraft's flight performance was equal to that of the conventional Yak-9. The operational altitude varied from 300 m to 3000 m.
Produced at Plant # 166 in Omsk, the Yak-9R long range version was created using the Yak-9D as a basis. The aircraft carried the AFA-3S/50 camera. A maximum range of 1400 km was provided by 480 kg of fuel in four tanks.
There were some long-range Yak-9Rs that did not carry UBS machine gun. These featured radio navigation equipment. Military trials undertaken showed the Yak-9R was more effective than the Pe-2 over targets with strong air defences. A total of 35 aircraft powered with VK-105PF engines had been produced by 13 August, 1943.
From 18 December, 1944 until 20 February, 1945 the Yak-9B version was evaluated by the! 30th Fighter Division, the trials proving unsuccessful. Nevertheless a military experimental series of 109 aircraft was produced. The fighter-bombers were allocated to this division, named «The small theater - to the Front!» A rebuilt rear fuselage compartment enabled the Yak-9B to carry a 400 kg bomb behind the cockpit. Takeoff weight was increased to 3,356 kg with a bombload of 200 kg. Bomb release could be achieved at dive angles of less than 45°. A 400 kg bomb load could not be released in this way and thus this bombing method was not used often. Furthermore, aircraft loaded with 400 kg bombs could not achieve sufficient longitudinal stability.
Only the experimental Yak-9K (VIP version) created at Plant #153 in July 1944 was evaluated by test pilot A. Pashkevitch. The aircraft incorporated the Yak-9DD's fuel system. The Official State evaluations were not undertaken.
The Yak-9V (trainer) was rebuilt from the Yak-9T and the Yak-9M in serial production. The aircraft featured two cockpits with a common canopy and 20mm ShVAK canon with 90 shells. Instrument equipment was quite advanced. Testing was undertaken at the Air Force Research Institute by V. Ivanov from 10 April 1945 to17 April 1945. A total of 493 Yak-9Vs was produced.
The Yak-9 was not the best Soviet fighter but, due chiefly to its ruggedness, stability, simplicity and cheapness of production, 16,769 aircraft were delivered between 1942 and 1948, the largest number of one single design built for service in armed forces of the USSR.
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