The Yakovlev Yak-1 

U.S.S.R.
U.S.S.R.

side view front view under view

The Yak-1 was the first member of a large family of succesful aircraft during World War 2. From the beginning, there were no compromises to the design, just rigorous demands to meet.
Before the design on the Yak-1 started, Alexander Yakovlev and his design Bureau had been working on light transports and trainers. However, Yakovlev wanted to build a front-line fighter. He received permission to work out a design for a 'frontal-fighter', a fighter that was to gain air superiority over the front line and that could withstand the rigors of a forward (and mostly primitive) airstrip.
yakovlev based his desing on three starting points, The Klimov M-106 Vee engine rated at 1,350 hp (1.007 kW), concentration of light armament in the forward fuselage, and a simple structure to ensure easy maintenance in the field. The use of stressed skin in combination with a light-alloy structure was considered as well, but decided against. The risks of adopting such a structure might outweigh the known advantages of retaining the bureau’s traditional type of mixed structure that made maximum effective use of known and readily available materials that imposed no major weight penalty and resulted in a structure that was also easy to repair.
Initially, the design was called Ya-26, a modern design with a mixed structure of a welded steel tube fuselage covered with a secondary light alloy structure. This second structure was covered with sheet metal of light alloys over the front part, and plywood over the rear part. The tail unit was a light alloy structure covered with fabric, and the wing was a plywood-covered wooden unit out of one piece. It was dihedraled, and tapered in thickness and chord. The ailerons, which were of the Frise-type, covered almost the full span, and were made of fabric-covered light alloy construction. Inboard there were a pair of Shrenk flaps that were powered pneumatically, and were made of light alloy. Finally, a cockpit was installed above the wing, with a rear-sliding section, and the landing gear was a wide track, inward retracting, pneumatic system.
In the meantime the prototype was renamed I-26, and the first flight was performed in January 1940. This aircraft was powered by 1 × Klimov M-105P Vee, rated at 1,050 hp (783 kW), driving a three-bladed variable pitch VISh-61 propeller. Armament consisted of 1 × 20 mm ShVAK fixed forward-firing cannon in a moteur-cannon installation, 120 rounds. Additionally 2 × 0.3 inch (7,62 mm) ShKAS fixed forward-firing in the upper nose, 500 rounds each, were installed as well. Alternatively to the 20 mm ShVAK cannon a 0.50 inch (12,7 mm) Beresin UBS gun, 250 rounds, could be installed.
Later prototypes were altered, as can be expected, and featured a separate duct for the oil cooler under the engine, air inlets for the carburetor in the wing leading edges, ejector exhaust stubs, increased chord of the fin, a fixed tailwheel, and a revised cockpit/rear turtledeck combination. This design, originally known as the Ya-26, was renamed Yak-1 and placed into production.

Version list:

Further pictures:

Yakovlev Yak-1 on an airfield
Yakovlev Yak-1 on an airfield

Another Yakovlev Yak-1 on an airfield. Note the different cockpit of an older model
Another Yakovlev Yak-1 on an airfield. Note the different cockpit of an older model

 

Technical data on the Yakovlev Yak-1
Powerplant 1 × Klimov M-105P Vee, rated at 1050 hp (782.76 kW) Role during war
  • Air superiority Fighter
  • Fighter
Length 27 ft 9.875 inch Height 8 ft 8 inch
Empty weight 5174 lb Operational weight 6276 lb max
Wing Span 32 ft 9.67 inch Wing Aspect ratio 5.83
Wing Area 184.61 sq ft Service ceiling 32810 ft
Maximum speed 373 mph at 9845 ft Cruising speed 149 mph at optimum altitude
Initial climb rate Climb to 16,405 ft in 5 min 24 sec Range 435 miles max
Fuel capacity internal 90 Imp gal (108 US gal) Fuel capacity external -
Machine guns
  • 2 × 0.3 inch ShKAS fixed forward-firing in the upper nose, 500 rounds each
Cannons
  • 1 × 20 mm ShVAK fixed forward-firing in a moteur-cannon installation, 120 rounds
Bomb load Up to 441 lb of disposable stores carried on two underwing hardpoints, rated at 220 lb each. General disposables load consisted of:
  • 2 × 220 lb FAB-100 bombs
Torpedoes/rockets Alternatively to bombs:
  • 6 × 3.2 inch RS-82 air-to-surface rockets
Crew 1 Naval or ground based Ground
First flight (prototype) Januari 1940 Operational Service Late 1940 - 1945
Manufacturer Yakovlev Design Bureau Number produced about 8.720 total, unknown this version
Metric system
Length 8.48 m Height 2.64 m
Empty weight 2347 kg Operational weight 2847 kg max
Wing Span 10 m Wing Aspect ratio 5.83
Wing Area 17.15 m² Service ceiling 10000 m
Maximum speed 600 km/h at 3001 m Cruising speed 240 km/h at optimum altitude
Initial climb rate Climb to 5000 m in 5 min 24 sec Range 700 km max
Fuel capacity internal 408 liters Fuel capacity external -
Machine guns
  • 2 × 7,62 mm ShKAS fixed forward-firing in the upper nose, 500 rounds each
Cannons
  • 1 × 20 mm ShVAK fixed forward-firing in a moteur-cannon installation, 120 rounds
Bomb load Up to 200 kg of disposable stores carried on two underwing hardpoints, rated at 100 kg each. General disposables load consisted of:
  • 2 × 100 kg FAB-100 bombs
Torpedoes/rockets Alternatively to bombs:
  • 6 × 82 mm RS-82 air-to-surface rockets

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Yakovlev Yak-1 
Yakovlev Ya-26 This was one of the original names of the prototype, later designated I-26.
Redesignated aircraft
Yakovlev I-26 This designation was given to the prototype of the Yak-1 family of aircraft, as well as the initial designation of the Yak-1 production series (described below). The I-26 was Alexander Yakovlev's first attempt to design and build a fighter. Yakovlev received permission to design a frontal fighter, a fighter that would be able to gain and maintain air superiority over the front and battle field, and could withstand the rigours of primitive forward airstrips and field maintenance. Work on the design and first prototype started in May 1939, and 8 months later with the workforce of only about 45 engineers and 150 workers the prototype was ready.
The prototype flew for the first time on January 13, 1940, equipped with skis for it's landing gear. Initially it was planned to power the I-26with the Klimov M-106, but this engine was still in development. Instead, the first prototype was powered by 1 × Klimov M-105P, a radial engine with a hollow drive shaft to enable the planned 20 mm cannon to be installed in the nose without the need for synchronisation equipment. 2 pairs of 0.3inch (7,62 mm) guns were installed in the upper and lower nose.
The first flight was succesfull, able to perform a steep climb and attain a very good speed. Because of the quick rise of the oil temperature the testpilot, Yulian Piontkovsky, decided to keep the flight short. Further testing revealed good figures, and some problems as well. The engine was changed 5 times, and the propellor even more often. The oil temperature problem seemed incurable in the beginning, and the landing gear was prone to jamming while retracting. Problems with the latter, the landing gear, also probably caused the type's first fatal accident, killing the test pilot on April 27 1940.
In the meantime a second prototype was build. This aircraft had an improved structure, and with a new location for the oil radiator. The radiator was placed below the engine in stead of between the cylinders of the engine. This machine also dropped two fo the four machine guns, apparently because the weight of the additional guns disturbed the balance/center of gravity. Although structure was strenghtened at som epoints, the aircraft's strength was still considered to be inadequate. This resulted in 'g' load limitations, and thus the second prototype took 24 seconds to turn a full circle.
State trials (which it failed by the way) showed that the second prototype had a max level speed of 304 mph (490 km/h) at sea level and 363 mph (585 km/h) at an altitude of 15,750 ft (4.800 m). The service ceiling stood at 33,500 ft (10.200 m), and time to climb to 16,400 ft (5.000 m) was about 6 minutes. All these results were measured with an typical take-off weight of 5,952 lb (2.700 kg)
Finally, the third prototype passed the state trials, in which it attained a speed of 394 mph (635 km/h) in a dive. The 'g' limitations were removed, resulting in a faster turn of 20 to 21 seconds. Weight had alreade rissen due to strenghtening, but was expected to rise more because in the prototypes no radio and electric equipment was installed.
Number built: 3
Yakovlev Yak-1 This version was the first production version. As such it still suffered from some of the deficiencies that were noted in the prototypes, but not yet solved on the production lines. Good examples of changes during the first production runs are the improved carburetor air inlet design, different main landing gear fairings, and the different fairing of the rear cockpit.
Number built: unknown out of approximately 8.720
Yakovlev Yak-1B The latter Yak-1 production models had a different fairing of the rear cockpit. This however did little to improve rearward vision. The solution was found by a front-line unit that removed the plywood rear decking, and cut down the rear fuselage slightly. There they installed a molded rear canopy made of Plexiglas. This change was soon incorporated into the production lines, resulting in the Yak-1B designation.
Most of the technical specifications and performance figures are identical to the Yak-1, but some were different: power was delivered by 1 × M-105PA Vee engine. Empty weight was 5,386 lb (2.443 kg), max take-off weight was 6,407 lb (2.906 kg). Max level speed peaked at 364 mph (585 km/h) at an altitude of 12,465 ft (3.800 m), and 322 mph (518 km/h) at sea level. Range was 426 miles (685 km), and climb to 16,405 ft (5.000 m) was performed in 6 min 30 seconds.
Number built: unknown out of approximately 8.720
Yakovlev Yak-1M This version was introduced into production at the same time as the Yak-1 and Yak-1B. Of the Yak-1B it inherited the cut down rear fuselage/canopy installation. Power was delivered by 1 × Klimov M-105PF Vee, rated at 1,260 hp (940 kW). This engine drove a three-blade VISh-105SV propeller of the constant-speed type. Structural changes were made to reduce weight, and internal fuel capacity was increased and better protected by using self sealing tanks. The tailwheel could be retracted, and the pilot had better armor protection.
This version was also reasonably similar to the Yak-1, but differed in the following areas: Armament consisted of 1 × 20 mm ShVAK cannon, 1 × 0.50 inch (12,7 mm) UBS gun, or alternatively 2 × 0.50 inch (12,7 mm) UBS guns. Empty weight was 4,848 lb (2.199 kg), max take-off weight was 5,864 lb (2.660 kg). Max level speed was 404 mph (650 km/h) at 14,765 ft (4.500 m) declining to 354 mph (570 km/h) at sea level. Range was 559 miles (900 km), and climb to 16,405 ft (5.000 m) was performed in 4 min 6 sec. Service ceiling was 35,435 ft (10.800 m)
Number built: unknown out of approximately 8.720
Yakovlev Yak-1 M106 Early in 1941 plans evolved to use the Klimov M-106 Vee for the Yak-1. This engine was expected to deliver some 1,350 hp (1.007 kW) at take-off and 6,500 ft (2.000 m), and 1,250 hp (932 kW) at 13,000 ft (4.000 m). This engine was later uprated by installing a one-speed supercharger. The use of the supercharger pushed the output of the engine to about 1,450 hp (1.081 kW) above an altitude of 13.000 ft (4.000 m). The M-106 had several advantages over the M-105PF, but had the same empty weight.
To take advantage of the new engine, a new airframe was built based on the Yak-1's airframe. The wings however had metal spars (as opposed to wooden ones), and the empennage was of all-metal construction. In the outer wing sections 2 fuel tanks were installed, each with a capacity of 88 Imp gal (106 US gal, 400 liters). In the wing center section two oil coolers were installed. The engine cowling, armament and equipment were identical to that of the Yak-1.
The tests showed promissing results: max level speed of 391 mph (630 km/h) at 11,200 ft (3.400 m), declining to 342 mph (551 km/h) at sea level. In the climb, 16,400 ft (5.000 m) was reached in 4 min 30 sec.
The downside of the new engine was that it was prone to overheating, it suffered from vibratuions, leaking oil, smoke trails and detonations. While testing an Klimov M-106 on a standard Yak-1 airframe speed decreased, and climb time was increased by more than a minute.
Some aircraft were built notwithstanding the shortcomings of the (clearly underdeveloped) M-106. Not al of these were flight-tested, and were retrofitted with a Klimov M-105PF
Number built: 47
Yakovlev Yak-7V Redesignation of the UTI-26
Redesignated aircraft
Yakovlev UTI-26 This version was the 2-seat trainer of the Yak-1 family. UTI stands for Uchebno-trenirovochny Istrebitel (training fighter). The design for this aircraft was submitted together with the design for the Yak-1 (or I-26). Since Yakovlev already had great experience designing trainers, it was expected that this would minimise risks, maximise quality, and increase production ease because of the similarity to the I-26. The new aircraft indeed resembled the I-26 strongly, the main difference being a tandem canopy for pupil and instructor under a single canopy, and the dual controls. To offset the different center of gravity because of the cockpit, the wings were placed a little further aft.
Testing revealed that the new trainer still had some shortcomings, mainly related to the main landing gear: the locks were unsafe, the wheels were too weak for take-off, the aircraft possessed a small anti-nose-over angle prohibiting the use of brakes while landing. This rendered the use of the UTI-26 unsafe for young inexperienced pilots. Since the I-26 was already chosen to become the advanced transitional trainer for the I-26, I-200 (MiG-1/MiG-3) and I-301 (LaGG-3) it was decided to continue with production and development.
The second prototype therefor was heavily modified with respect to the main landing gear, and to other areas as well like the tailplane, structural changes to increase the nose-over angle, and center of gravity. This resulted in a pleasant and forgiving trainer.
Number built: unknown out of approximately 8.720
Yakovlev UTI-1 Redesignation of the UTI-26
Redesignated aircraft
Yakovlev UTI-27 Redesignation of the UTI-26
Redesignated aircraft

Operational remarks:

The Yak-1 was just in time to be reasonably available when Operation Barbarossa, the German attack on the Soviet Union, commenced. Soon after the attack, most fighters were modified to perform in the fighter-bomber role, fitted with two hardpoints rated at 200 lb (100 kg) each. This enabled the fighter to carry either 2 × 200 lb (100 kg) FAB-100 bombs, or 6 × 3.2 inch (82 mm) RS-82 air-to-surface rockets.
As a pure fighter, it was handled with respect from the Luftwaffe pilots, who assessed the aircraft as 'probably the best fighter in the Soviet arsenal' at the time of Operation Barbarossa. It had a good climb rate and maneuverability, but lacked performance in the high altitudes, gratefully exploited by the Luftwaffe pilots.
The Yak-1 was also the main fighter in defence of moscow. Some 133 aircraft were defending the city, 1 in 6 of all defending fighters. Yet only 9 were unserviceable, which shows that it was easy to maintain even under harsh conditions. Another story tells of the durability of the fighter: the first kill over the Moscow area was scored by a Yak-1; when in pursuit of a Luftwaffe reconnaissance aircraft the guns of the pursuer seized, and the Soviet pilot then rammed the Luftwaffe aircraft, safely landing afterward.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 5/27/02