Wing shapes of Russian fighters
- Thread starter spicmart
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special ed
1st Lieutenant
- 6,602
- May 13, 2018
Stalin said so.
GregP
Major
I'm going to guess they knew they didn't have a great high-altitude engine and wanted to maximize their low-to-medium altitude fighters. The typical Soviet triangular wing makes a good rolling platform and the lower aspect ratio and area concentrated closer to the centerline makes for a good dogfighting platform in the lower altitude region if not bungled by mistakes. The I-185 wasn't quite so triangularly pronounced, but was nontheless similarly tapered, too.
One thing about the Soviet system that stood out was that failure did not generally have a good result for the entity who failed. It was sometimes fatal, literally. When the first triangular wing platform came out and was successful, the rest of the designers likely copied the concept, thinking it would give a better probabiliity of not failing. Even the early Yakovlev jets had the same wing and same fuselage. The next breakout platform was the MiG-15 and there were several jets with the same basic layout.
I can think of the La-15, IL-40/42, IL-102, La-168, La-176, La-190, MiG-17, MiG-19, Su-15, and Yak-25 with siumilar wing layouts to the MiG-15, which was a highly successful design if ever there was one. 17,300 or so built in several countries.
The Soviet Union had decades of designers copying successful designs to help ensure they wouldn't be sent to the gulag or killed if their design failed to meet spec. It was likely a very good thing for Soviet designers of aircraft, ships, electronics, and guns when Stalin passed away.
One thing about the Soviet system that stood out was that failure did not generally have a good result for the entity who failed. It was sometimes fatal, literally. When the first triangular wing platform came out and was successful, the rest of the designers likely copied the concept, thinking it would give a better probabiliity of not failing. Even the early Yakovlev jets had the same wing and same fuselage. The next breakout platform was the MiG-15 and there were several jets with the same basic layout.
I can think of the La-15, IL-40/42, IL-102, La-168, La-176, La-190, MiG-17, MiG-19, Su-15, and Yak-25 with siumilar wing layouts to the MiG-15, which was a highly successful design if ever there was one. 17,300 or so built in several countries.
The Soviet Union had decades of designers copying successful designs to help ensure they wouldn't be sent to the gulag or killed if their design failed to meet spec. It was likely a very good thing for Soviet designers of aircraft, ships, electronics, and guns when Stalin passed away.
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What fighters are you talking about?
By the time of beginning the design of the first Soviet jet fighters (T-3, E-4) with triangular wings, Stalin had already passed away. However, it is possible that the designers still remembered his instructions...Only one thing can be said: this has nothing to do with Soviet reality, which cannot be reduced to primitive schemes.
- Thread starter
- #7
Especially the Lavochkin and Yakovlev fighters, but also MiG and Polikarpov and others to a lesser extent.
I had read somewhere the most aerodynamic wing was believed ro be elliptical in shape. I don't remember why. It was also very expensive to build and most designers of the time felt the cost did not justify the performance improvement. I have assumed the Soviet designers were trying to get some of the elliptical wing shape benefits while avoiding most of the construction cost penalties. I don't have anything to support that though and it could be all wrong.
Piston-engined fighters? Or jets?
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It's a common result in aerodynamics that for a given span, an elliptical spanload distribution provides the minimum induced drag. (but that doesn't necessarily mean that the wing planform itself needs to be elliptical).
Some recent research based on an old paper by Prandtl suggests a slightly different distribution might be even better. See post at What's Wrong with Flying Wings?
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Most likely WWII aircraft, such as the MiG-1, MiG-3, Tu-2, Ar-2, Pe-2, Su-2, LaGG-3, Yak-3, Yak-7, Po-185, etc. etc. etc.
1. This wing shape is called trapezoidal with rounded wingtips. This is the term used both in Soviet documents and in technical literature.
2. Practically any wing shape of a single-engine monoplane fighter from World War II can be approximated either by a trapezoid or a combination of two trapezoids—even the elliptical wing of the Spitfire.
3. The ratio of the trapezoid bases may vary, as well as the shape of the rounded tips, but I see no fundamental difference between Soviet, German, and British fighters, as well as US Army Air Forces fighters—see the picture. I was too lazy to include Italian and French ones as well. US naval fighters are somewhat different.
4. The use of a tapered wing was probably motivated by a desire to reduce the moment of inertia. In general, when trying to understand the logic of Soviet engineers, the starting point should be that they tried to simplify the manufacturing technology as much as possible, and the possibilities for optimization based on wind tunnel tests were limited.
2. Practically any wing shape of a single-engine monoplane fighter from World War II can be approximated either by a trapezoid or a combination of two trapezoids—even the elliptical wing of the Spitfire.
3. The ratio of the trapezoid bases may vary, as well as the shape of the rounded tips, but I see no fundamental difference between Soviet, German, and British fighters, as well as US Army Air Forces fighters—see the picture. I was too lazy to include Italian and French ones as well. US naval fighters are somewhat different.
4. The use of a tapered wing was probably motivated by a desire to reduce the moment of inertia. In general, when trying to understand the logic of Soviet engineers, the starting point should be that they tried to simplify the manufacturing technology as much as possible, and the possibilities for optimization based on wind tunnel tests were limited.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
A Trapezoidal platform does not include Elliptical.
The Soviets tended to use a "Tapered" planform, which is not part of the Elliptical grouping.
The Spitfire, P-47 and He280 used a form of an Elliptical planform.
The Soviets tended to use a "Tapered" planform, which is not part of the Elliptical grouping.
The Spitfire, P-47 and He280 used a form of an Elliptical planform.
I surmise that in the case of the jets the planform was recommended by TsAGI. They had the mission and the resources to test planforms in that turbulent development era of the 40s and 50s. There are aircraft of different sizes and mission which have similar wings. I different classes over time. So, |MiG-15, La-15, Yak 25 stretching it to Tu-16 and -95. MiG-19 and Su-7, and that MiG which was a -21 with a -19 wing. Then the tailed delta types. MiG-21 to M-50 via Su-9 and -15
In 1943, a wind tunnel (T-106) was launched in the USSR, which allowed the study of aerodynamics at high subsonic speeds, but until 1945, swept wings were practically not studied. And all of the TsAGI's recommendations for the first Soviet aircraft with swept wings (35°) were, as far as I understand, mainly a creative interpretation of German experience. But I am not ready to produce a detailed analysis of where exactly German experience was used and where their own developments were used.
During the war, TsAGI worked under the strict control of the People's Commissariat for Aviation Industry - they were primarily responsible for making recommendations for improving production aircraft. And TsAGI's recommendations were not always well-founded - for example, according to TsAGI's recommendations, the wing loading for a fighter should not exceed 170 kg/m2, but Polikarpov had already built the I-185 with a load of more than 200 kg/m2, which surpassed all fighters created in accordance with TsAGI's recommendations! In general, TsAGI's capabilities were also quite limited, although Chaplygin managed, in an amazing way, to protect his staff from Stalin's repressions.
By the way, in Soviet publications, I came across statements (with justification) that a trapezoidal wing with a certain base ratio is practically equivalent in its properties to an elliptical wing with the same aerodynamic profile - in terms of pressure distribution, stall characteristics, etc. In other words, an elliptical wing offers only a couple of percent advantage over a trapezoidal wing like this, while the latter has incomparably simpler manufacturing technology. In the USSR, mass production of elliptical wings was hardly realistic, but the Brits could afford to spend resources for the sake of a couple of percent advantage in performance.
wrathofatlantis
Airman
- 75
- Oct 2, 2023
The Spitfire was not a tight turner but did prove able to maintain speed in turns, so the radius was wide (well over 1000 ft in all models) but the 360 turn rate was still high (around 20 to 22 seconds).
Unfortunately, in the actual reality of combat it turned out that it was radius (and thus the lowest speed) that allowed a steady leading aim... ("turn fighting is a race where the slowest wins" was the period saying) The gentle stall could not compensate enough by allowing the Spitfire to go faster and briefly take rumbling wings snapshots at smaller German circles... ("shooting across the circle" as Spitfire pilots commonly called this tactic, which was fairly unique to the Spitfire). The 20 mms did allow the occasional success this way, but it was not typical. The Spit was excellent in high speed hit and run type tactics, and the Russians noted this when they they used it. (Though hit and Run required a non-turning unaware target most of the time, which was getting scarcer by 1944, given the improving radios... But the Soviets were still stuck with a system where only the leader could transmit: Rall: "It was like fighting an apparatus: You took out the tip of the V and rest milled about in confusion.")
Until the later Marks XIVs, Spit pilots often mention the lack of "penetration" of their wings as they dive: Yet the ultimate dive speed on the Mk IX and later models was quite high.
If you look at the above posted wing drawings, you will see a big difference in wing leading edge sweep between the La-5 and Yak (6th and 7th from top at left): Aside the La-5 wing slats, I think the big difference in sweep explains why the Yak was flown at full power during turns (a rare notion in later WWII combat: Erich Brunotte mentions never going outside 0.9 ATA or 1.2 ATA on his 190D-9, on a max of 1.9 ATA, or 50 to 60% of max power during 1945 combat. He occasionally did so for straight lines "we rarely used high power", which implies combat for him meant turning constantly) while the La-5 was widely known for actually lowering power during turns (as mentioned by fin ace Karhila), despite the seven steps throttle...
It is well known that squeezed air accelerates, and my theory is that air squeezed between the wing and the prop accelerates the wing top air during low speed turns (through a dogleg that appears below a certain speed), increasing lift without increasing drag (not a violation of physics if you understand the difference between force and energy). The Yaks may have had too much leading edge sweep to "trap" the air, hence the constant high power setting which was a standard procedure for these types.
The P-40 had perfectly straight leading edges and was quite heavy, yet despite a very low power to weight ratio it was measured to turn 360s in 19 seconds; better than any later P-51 ever did... The La-5 was also known for its low speed turns, but not the Yak: Despite a similar looking triangular taper plan view of their wings, the difference in actual leading edge sweep angle is quite large between the Yak and La-5, and possibly explains this La-5 down-throttled turn preference beyond just the La-5 slats.
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