YAK-7

Jakovlev Jak-7 (ven. Яковлев Як-7) oli neuvostoliittolainen, toisen maailmansodan aikainen yksimoottorinen hävittäjälentokone.

Jak-7 suunniteltiin kaksipaikkaiseksi jatkokoulutuskoneeksi. Uuden koneen perustana oli Jakovlev Jak-1:n prototyyppi I-26. Tämän UTI-26-koneen prototyyppi lensi ensilentonsa 4. heinäkuuta 1940. UTI-26-koneessa oli kaksi ohjaamoa peräkkäin ja näiden välinen kommunikointijärjestelmä sekä yksi 7,62 mm ShKAS -konekivääri. Siipiä oli siirretty taaksepäin tasapainon vuoksi.

Ensimmäisissä Jak-7UTI-malleissa oli sisäänvedettävä laskuteline. Osa alkuperäisistä sarjatuotantokoneista oli kaksipaikkaisia Jak-7V-koneita (V - "Vyvozoni", tutustuminen). Tässä oli kiinteä laskuteline. Kaksipaikkaisesta harjoituskoneesta kehitettiin nopea versio matkustajan kuljettamiseen, Se sai tunnuksen Jak-7K ("Kurjerski" eli kuriiri).

Jak-7:ta kehitti eteenpäin K. A. Sinelštšikovin ryhmä, joka oli määrätty suunnitteluryhmästä valvomaan koneiden valmistusta. Sinelštšikov kehitti koneesta aseistetun mallin 20 mm ShVAK -tykillä ja kahdella 7,62 mm ShKAS -konekiväärillä. Takaohjaamo säilytettiin mahdollisia kuriiritehtäviä tai lisäpolttoainetta varten. 

Kone sai tyyppimerkinnän Yak-7/M-105P käyttämänsä Klimov M-105PA-moottorin mukaan. Jakovlev suhtautui epäillen uuteen koneeseen, mutta tehdastesteissä kone osoittautui paremmaksi kuin Jak-1. Osasyynä olivat koulutusmalliin tehdyt muutokset, kuten suuremmilla pyörillä ja paremmilla jarruilla varustettu laskuteline ja parempi korkeusperäsin.

Puolustuskomitea määräsi elokuussa 1941 koneen sarjavalmistukseen tehtaissa N°301 ja N°153, mutta tehdas 301 oli evakuoitava Novosibirskiin. Näin vuonna 1941 saatiin valmistettua vain 60 konetta.

Alkuvuodesta 1942 valmistettu kone sai tyyppimerkinnäkseen Jak-7A. Aseistuksena oli kaksi 7,62 mm ShKAS-konekivääriä ja yksi 20 mm ShVAK-tykki. Kone pystyi kuljettamaan kuusi RS-82 -rakettia tai kaksi FAB 100 kg -pommia. Lentäjät pitivät koneen raskaasta aseistuksesta ja ohjattavuudesta.

Eniten valmistettu oli Jak-7B, jonka valmistus alkoi toukokuussa 1942 ja jatkui joulukuuhun 1943. Tässä mallissa ShKAS:t korvattiin raskailla 12,7 Berezin UB -konekivääreillä. Kesään 1942 mennessä sen voimanlähteeksi saatiin parannettu Klimov M-105PF -moottori (1 180 hp).

Heinäkuussa 1942 koelennettiin Jak-7D-versio (D - Dalnyi eli pitkänmatkan versio). Kehitystyön tuloksena valmistui Jak-7DI ("Dalnyi Istrebitel") joka sai nimen Jak-9.

Jak-7 koneita valmistettiin 6 399 kappaletta vuoden 1943 alkuun mennessä. Näistä yli 5 000 oli tyyppiä Jak-7B.
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The Soviet Yakovlev Yak-7 was developed from the earlier Yak-1 fighter, initially as a trainer but converted into a fighter. As both a fighter and later reverting to its original training role, the Yak-7 proved to be a capable aircraft and was well liked by air crews. The Yak-7 was simpler, tougher and generally better than the Yak-1.

In 1939, Alexander Yakovlev designed a tandem-seat advanced trainer, originally designated "I-27" and then "UTI-26", offered along with the original I-26 proposal that became the Yak-1. The "UTI" (Uchebno Trenirovochnyi Istrebitel, translated as: Training Fighter) was intended to give pilots-in-training experience on a high-performance aircraft before transitioning to a fighter. 

Crew: 1
Length: 8.48 m (27 ft 10 in)
Wingspan: 10 m (32 ft 10 in)
Wing area: 17.15 m2 (184.6 sq ft)
Empty weight: 2,450 kg (5,401 lb)
Gross weight: 2,935 kg (6,471 lb)
Powerplant: 1 × M-105PA V-12 liquid-cooled piston engine, 780 kW (1,050 hp) at rated altitude
Maximum speed: 495 km/h (308 mph; 267 kn) at sea level
571 km/h (355 mph; 308 kn) at 5,000 m (16,000 ft)
Range: 643 km (400 mi; 347 nmi)
Service ceiling: 9,500 m (31,168 ft)
Rate of climb: 12 m/s (2,400 ft/min)
Time to altitude: 5,000 m (16,000 ft) in 6.4 minutes
Wing loading: 172.6 kg/m2 (35.4 lb/sq ft)
Power/mass: 0.26 kW/kg (0.16 hp/lb)
Take-off run: 410 m (1,350 ft)
Landing run: 610 m (2,000 ft)
Sustained turn time: 21 - 22 seconds
Armament: 1 × 20 mm ShVAK cannon +2 × 7.62 mm (0.300 in) ShKAS mg.
 Later models like the "B", used 2 x 12.7mm Berezin_UB guns.

With development work started in 1940, the UTI-26 differed from its predecessor in its larger span wing being placed farther back for balance as well as having two cockpits with dual controls and a rudimentary communication system. It was armed with a single 7.62 mm (0.30 in) ShKAS machine gun in the cowling, mainly for use in training, but Yakovlev envisioned a multi-purpose aircraft that could also undertake courier and light transport duties at the front.

The first production aircraft known as Yak-7UTIs retained a retractable main landing gear, but beginning in the summer of 1941, a fixed landing gear variant, the Yak-7V (Vyvozoni for Familiarization) was substituted. The factory reasoned that production would be simplified and that reduced performance would not be detrimental for a trainer. Yak-7UTIs and Yak-7Vs were also equipped with skis for winter operations.

A factory team from N° 301, headed by K.A. Sinelshchikov, was detached from the Yakovlev OKB to supervise production of Yak-7UTI. One of these aircraft (serial number 04-11) was fitted with an armored backrest plate over the rear position, self-sealing fuel tanks which filled with inert gas as they emptied, three "RO" rocket launchers under each wing for as many RS-82 rockets, an axial 20 mm (0.79 in) ShVAK cannon firing through the propeller spinner, with 120 rounds, and two 7.62 mm ShKAS machine guns under the cowling, each with 750 rounds.

The rear cockpit position was retained, allowing it to accommodate a second seat (without controls) for fast courier and transport duties or a fuel tank for extended range. The additional space could also house bombs or other gear. The engine was an M-105P and the model was designated Yak-7/M-105P.

Sinelshchikov did not inform Yakovlev about the conversion and when he learned about it, Yakovlev remained sceptical of the need for the changes. After brief factory trials, the aircraft turned out to be better than the single-seat Yak-1, thanks to the modifications already applied to the UTI as well as revised undercarriage with bigger tires and wheels, more efficient brakes and revised elevators, among other changes. Yakovlev submitted the Yak-7 to the authorities who approved it immediately. The firing tests at the scientific trials Polygon for aircraft armament (NIPAV) were a success and the armament was found to have no effect on the flight characteristics or the general performances of the new fighter. The aircraft's stability as a firing platform was judged far better than that of the Yak-1, the Lavochkin-Gorbunov-Gudkov LaGG-3 and Mikoyan-Gurevich MiG-3.

The GKO and the NKAP issued decrees in August 1941 for the Yak-7 to be produced by Factories N°301 and N°153, but the Factory 301 had to be evacuated to Novosibirsk where it merged with N° 153. So, just 62 aircraft were produced in 1941: 51 in September–October by Factory N° 301 and 11 by N°153 in December.[3] Test pilot A.N. Lazarev noted the good flight characteristics, how easy it was to get out of a spin, how well it behaved when diving, characteristics that he considered safer than those of the Yak-1. But the Yak-7 showed some defects: the M-105P engine piping, the landing gear locking system, the tires and the tail wheel were identified. The Yak-7 was introduced into the production line and the first batch of 60 reached operational squadrons by the end of 1941.

Another important variant was the Yak-7/M-105PA. On this model, the two ShKAS on the cowling had been replaced by two 12.7 mm (0.50 in) UBS machine guns with 400 rounds (260 for the left and 160 for the right). It was powered by an M-105PA engine with an axial ShVAK cannon with 120 rounds. Oil and glycol radiators had been widened and refined and slightly tilted downward. The insulation of the airframe was improved, tail wheel was totally retractable; joints and skin were more carefully made; panels on engine cowling fitted better; the propeller reduction gear worked better; an electro-pneumatic reloading system was installed; canopy frame was reinforced. The Yak-7B made 27 tests flights in January and February 1942. 

The reports noted that while the aircraft "was not inferior to the LaGG-3 and MiG-3 and to foreign fighters in service in the USSR", it was more stable and had better flight characteristics. Subsequently, the GKO authorised production at Factory N°153 in place of the Yak-7A, from April 1942 and 261 machines were built until July. After 20 May, the aircraft were equipped with a 68 l (18 US gal) tank behind the pilot’s seat, but the pilots that used the Yak-7 on Stalingrad and on the Kuban removed it as it was not protected and affected the flight characteristics. 

Generally, the Yak-7B pleased its pilots. They reported that it was easy to fly at all altitudes, stable and easy to maintain and although it did not climb as quickly as a Messerschmitt Bf 109, it was as manoeuvrable and fast, except in the vertical plane. But defects were also noted: there was too much drag from the radiators, the canopy glass was of bad quality; the pilot was not protected enough, taking-off and landing distances were too long and, above all, it was underpowered.

Yakovlev suggested Klimov, the engine builder, some modifications that resulted in the M-105PF which was 130 hp (97 kW) more powerful. With this modified engine, the Yak-7B top speed was of 599 km/h (372 mph), it climbed much faster up to 5,000 m (16,404 ft) and it was more manoeuvrable both in the horizontal and the vertical planes. But because the rear tank was removed, its range was reduced and the CG was moved too forward, while M-105 defects (glycol and oil overheating, oil leaks etc.) persisted.

Among the engine and armament options was the Yak-7-37 fitted with a 37 mm (1.457 in) MPSh-37 cannon, (MPSh - motornaya pushka Shpital'novo - engine mounted Shpital'nyy cannon), mounted between the engine cylinder blocks, firing through the propeller spinner.

The Yak-7 proved to be an effective close support fighter although the first two-seaters were considered nose-heavy, consequently, the factory introduced a rear cockpit fuel tank. Pilots complained about the fuel tank's vulnerability since it was unarmored, and it was usually removed in the field. There were constant changes to the design based on combat observations including a definitive single-seat variant, the Yak-7B, which was produced in large numbers.

After the war, some Yak-7V trainers were provided to the Poles and a single Yak-7V was delivered to the Hungarians for familiarization with the Yak-9 fighter.

After trials in April–May 1942, a small batch of 22 Yak-7-37s was authorised, all of which were issued to the 42nd IAP at the North-Western front, where they proved highly successful both in air-to-air combat and ground attack.