Yak 1 and Yak 7

Discussion in 'Aviation' started by claidemore, Feb 6, 2008.

  1. claidemore

    claidemore Member

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    Thought I would write up a little article on the Soviet Unions best fighters up till 1943 the Yak 1 and Yak 7.

    There is always confusion about the model designation of the Yaks, the misconception being that the Yak 1 came out first, followed by the Yak 7, Yak 9, and finally the Yak 3. This is sometimes construed as a mixed up designation system. But actually the Yak 1 and Yak 7 were separate though very similar developments at the same time from the same design bureau , with the Yak 1 evolving into the Yak 3 and the Yak 7 UTI trainer evolving into the Yak 7 fighter, and eventually into the Yak 9. Hope that clears it up!
    The Yak 1 started production in 1940, even before testing on the prototypes was completed. 400 Yak 1’s with the 1020 hp Klimov M105P engine had been delivered to the VVS before June 1941. During initial testing of the Yak in 1940, it was discovered that I-16 pilots could transfer to the Yak 1 without any special training, something that proved very useful as the Luftwaffe decimated the I-16 units.

    Yak 1 fighter specs 1941
    Combat weight of 2930 kgs
    Wing loading of 171 kg/m2
    472 kmh @ sea level
    563 kmh @ 5000 meters
    Climb to 5000m in 6 minutes
    Turn time reported to be 19 seconds
    1- 20 mm ShVAK cannon and two 7.62 mm ShKAS mg. (comparable to Bf 109 F4 and G2 armament)

    In 1942 improvements were made, weight reduced , more powerful engines M-105PA (1100hp) and M-105PF (1210hp) engines, all round vision canopy, 2 x 7.62 mg replaced by one 12.7 mm UBS mg. This version is unofficially called the Yak 1b.
    Combat weight 2883 kg
    512 kmh @sea level
    585 kmh @ 4000 meters.
    Climb to 5000m in 5.4 minutes

    The Yak7 UTI was designed at the same time as the Yak 1 and was intended (and used) as a high performance two seat trainer for pilots who would fly all three new high performance fighters in the Soviet inventory, Yak 1, LaGG 3 and Mig 3. Pilots started training on U2 biplanes, then UT-2 monoplanes, finishing off with the Yak7 UTI. (Osoaviakim, the soviet ‘air cadets’ actually had 100,000 pilots with basic flight training in early 1941)

    With a shortage of front line fighters, consideration was given to converting the Yak 7 trainer to a fighter. Tests were conducted and in January 1942 production of the Yak7A started. This plane had identical armament to the Yak 1. This was supplanted by the Yak7B in April, 1942. These types saw initial combat in the Kuban and at Stalingrad.
    Yak 7B stats: (M105 PA engine)
    Combat weight 3042 kg
    500kmh@ sea level
    580 kmh @ 4800 meters
    1 x 20mm ShVAK and 2 x 12.7mm UBS mg (other variations in armament existed)

    This compares very favorably to the Yak 1. Being 159 kg heavier that the Yak1b, pilots reported the Yak 7 to be slightly less maneuverable, and to ‘feel’ heavier.

    As far as it’s performance against the Messerschmitt, it was faster than the Emil variants, which saw less and less use on the main fronts, though they were being used as Jabos at least until Stalingrad and even later in the north.
    The main fighters they faced were of course 109F and 109G.
    The 109 F4 is reported as doing 526 kmh @ sea level and 614 kmh at 4000 meters, with weight nearly identical to the Yak1b. Engine in the F4 was 1350 hp. Climb to 5k was a bit less than 5 minutes. Wing loading on the F models was only slightly higher than the Yak, 181 kg/m2 compared to 171.
    The 109 G2 is listed as doing 525 kmh @sea level and 602 kmh @ 4000 meters. Wing loading is 195.8 kg/m2 . The DB605 engine was rated @1310hp with initial limitations in 1942, rising to 1475hp by spring of 1943. Climb performance in the G2 is about 1 minute faster to 5000 meters, depending on which source/test you use for comparison. Bf 109 G6 speeds were comparable to the G2, ([email protected], 620@ 6.5k) but at a higher wing loading of 209.6 kg/m2.

    Basically the Yaks were ‘almost as good’ as the Messers they faced. They were 10-30 kmh slower depending on altitude, and didn’t climb quite as fast. They were commonly perceived as being more maneuverable, but on paper, it would appear that the F models had the advantage. The heavier Gustavs would have conceded some maneuverability to the Yak as the G models increase in horsepower was offset by weight increases, while the Yaks weight stayed the same or decreased as it got more powerful engines.
    The 109 was always better in the dive than the Yak.

    One area where the Yak seemed to equal the 109 was in the combat turn, ie a climbing turn to gain better position. It gained the same amount of altitude in this maneuver. The Yak also had comparable thrust / weight ratios, so it was a close match in acceleration.

    The French Normandie Niemen regiment flew Yak1b fighters in the spring of 1943 and their leading scorer considered the Yak1b to be a much better plane than the Spitfire MkII and MkV which he had flown.

    The strengths of the Yak were that it was easy to fly, instilled confidence in its pilots, had a wide stable undercarriage, and was cheap and simple to produce. Firepower was adequate,(barely) and performance was good though not superior. One advantage not often noted, is that it was designed for cold weather operation, having systems to dilute oil, and with winter variants supplied with insulated tubing and special insulated plugs and blankets. During the winters of 1941 and 1942 this allowed them to fly more sorties than the Luftwaffe, giving them temporary air superiority over Moscow and Stalingrad at crucial times. From 1943 on the Yaks were increasing used in the close escort role, a tactical doctrine not favored by most air forces, but one the Soviets used successfully.

    About 33,000 Yaks were made (some sources say 36,000), putting it second behind the IL2 as most produced war plane.

    Two sources used in this article:
    Russian Aviation Museum
    Kurfurst - Your resource on Messerschmitt Bf 109 performance
     
  2. timshatz

    timshatz Active Member

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    Good post. Good read. Thanks for posting.
     
  3. Vincenzo

    Vincenzo Active Member

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  4. claidemore

    claidemore Member

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    Two tests show sea level speeds of 523 and 526 and at 4k alt they indicate speeds of 611 and 614. One remark by the author of the site shows speeds of 537 at sea level and 670 @6.2k alt. The theory is that there is some difference in reported speeds due to compressability not being considered in one test. Remarkable oversight from a meticulous testing facility. I'm just taking the results at face value.
    The 1942 chart on the bottom of the page shows 523 and 611 speeds, I used the slightly higher figures from the 1941 chart in my article.

    There are other sources which claim different speeds for the Yaks as well.
     
  5. Graeme

    Graeme Well-Known Member

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    Informative post Claidemore. Thanks.

    This family 'Yak Tree' may also help clear up the designation sequence...

    [​IMG]
     
  6. claidemore

    claidemore Member

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    A picture really is worth a 1000 words! :D
     
  7. Konigstiger205

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    Interesting stuff...I didn't knew that the Yak development was so...tangled up...
     
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