Sten SMG aircraft: productionized aircraft part 1, the reality

[Shortround6]

But they did not have those engines to spare. They were the there to keep the trainers in the air. The production lines were turned over to Merlin's long before. Put the Kestrels in (needed for training) Masters single seaters then you turn off the 1940 tap of newly trained pilots which was the real RAF log jam at that time. That was the whole reason for the vast investment in the Empire training scheme that paid off handsomely thereafter. Even Miles realised the finite supply of Kestrels and flew the first Mercury powered Master in 1939.

You have an 'emergency', not enough fighters at the moment and facing a German Sea invasion. What happens in 1941 is not the 1st emergency. It might very well be the 2nd
Turns out that Merlin production was enough, whatever raids that aimed at the RR factories only did slight damage, unlike raids on Supermarine and Shorts. Trying to come up with a plan after the bombs land on a factory is too late. Germans managed to hit Supermarine about 2 months (?) after Castle Bromwich came on line which took up some of the slack while the Supermarine factory was dispersed. Germans managed not to hit Hawker and Gloster or at least not badly (?) and Curtiss aircraft were beginning to be unloaded at the docks. (they were not ready to use). There were a lot of moving parts.

But the essence of "emergency fighters" or "cheap" fighters (usually not the same thing) is to use engines that are not first line engines so you are not splitting up your 1st line engine production more than it already is. Likewise using wooden construction so not compete with existing aluminum allocations. Sometimes "cheap" just meant making things to a smaller scale so the planes used less raw materials. By using a smaller, lighter weight structure the designers hoped to use a smaller, lighter weight engine. This never worked out quite as well as hoped.
TANSTAAFL.

 

[eagledad]

SR

Would the Ki-100 fit the bill for an emergency and effective fighter? IIRC, there were airframes without engines, and an engine that was not being used by Japanese front line Army fighters. Certainly, the debut of the Ki-100 surprised Allied intelligence units. I am not aware of any TAIC manual pages.

Eagledad

 

[Shortround6]

It might, depends on the definition.
However double check the engine. while it was not in wide spread use in the Army planes (it was used in the Ki-46 III) it was in used in a number of navy planes.
It was also planed to use it to replace the Sakae engine in some planes.

 

[eagledad]

It might, depends on the definition.
However double check the engine. while it was not in wide spread use in the Army planes (it was used in the Ki-46 III) it was in used in a number of navy planes.
It was also planed to use it to replace the Sakae engine in some planes.

SR

Thank you. It appears the engine used for the Ki-100 was used on more Japanese aircraft than I remebered. So, while the airframes were engineless, the engines used on the Ki-100 would have not been available for other aircraft that were currently (Ki-46) or planned (A6M) for production.

Eagledad

 

[BarnOwlLover]

There were also some "productionized" Ki-84s, the Ki-106 that was mostly wood, the Ki-113 that used some steel components, and the lightweight Ki-116 with a Mitsubishi Ha-112 engine. Also the Ta-152 used some steel parts in its construction.

 

[Shortround6]

Steel can be used for some parts, But generally steel is heavier than Aluminum.
The use of alternative materials in Ki-84 saga actual illustrates this quite well, Look up the increased weight of Ki-106 and Ki-113.
And figure out the change in performance of the Ki-116. Light weight only goes so far when you have 77% of the power at 20,000ft.

Having lower performing fighters vs no fighters is a plus, but trying to adapt existing designs is often not the best way to get to the desired goals.
Or you have to lower the goals (less fuel for less range/endurance, less armament which makes the plane less effective).

 

[Wild_Bill_Kelso]

I'm thinking the simplest was the Vickers Venom. It did NOT make production, but was extremely simple and robust. Likely SHOULD have made it into production.

Straight, untapered wing, easy fabrication, lots of "easy to make and repair" type features. A low-wing monoplane single-seat, single-engined, eight-gun fighter aircraft. It was fast and manoeuvrable but its Bristol Aquila radial engine was underpowered. Together with other designs built to the same specification, which included the Bristol Type 146, Gloster F.5/34, and Martin-Baker MB 2, it was rejected by the Air Ministry and only one Venom was built.

View attachment 732539

Hard to imagine an easier-to-make, easier-to-repair aircraft.

So, naturally, they didn't build it!

Wow, that is awesome! Every time I think I've seen all the WW2 military aircraft, another design shows up that I'd never heard of... I really like the look of this one too.

 

[Shortround6]

Wow, that is awesome! Every time I think I've seen all the WW2 military aircraft, another design shows up that I'd never heard of... I really like the look of this one too.

It had no future. Some what is said about it is a bit dubious, not going to say impossible but dubious.
It was 'supposed' to have flown with full armament starting at it's first flight.
Trouble is no known photograph shows guns, gun hatches, cartridge ejection slots. Like

Maybe they took the guns out and covered up the openings? Then you get stuff like this "The compact radial engine gave the Venom a better rate of roll and turn than its long nosed water-cooled competitors but it was soon clear the potential power from the Merlin was greater than was likely to be available from the Aquila in the near future, with only limited development of this engine being undertaken, while no other engines were available suitable for fitting in such a small airframe."

Hmmm.
1650 cu in vs 950 cu in engine.
Potential power was all too clear.

 

[Wild_Bill_Kelso]

A long nose P-40 was about 30mph faster than a P-36. we can argue about effectiveness.

The "simple" idea sounds good for about 3 seconds. Then reality kicks in. Much like the light weight/cheap fighter theory.
Lets break a few things down.
Landing gear, once you use retracting landing gear the parts numbers are not that much different. A larger fighter will use bigger, heavier parts but it doesn't use more of them, Like twin hydraulic struts for each wheel. So landing gear maintenance is roughly the same. Russians tried to use pneumatic retraction but they had more failures, including landing gear collapsing while parked. Brake maintenance?
Radios, unless you do away with the radios or try to use a single channel you have mostly the same maintenance issues aside form access (hatches) issues.
Instrument panels. Unless you leave out instruments (some I-16s didn't have fuel gauge, Pilot depended on his wrist watch and the sound of the engine) most planes are going to need pretty much the same maintenance.
Armament, again, unless you leave out guns (four .303s vs eight .303s) there is not a much savings there. OK Hurricane only had 3 doors to expose 4 guns vs the 4 doors on the Spitifre per wing but you have to pull all the guns out, break them down, clean them, reassemble and reinstall. total time saved by the better door arrangement??

engines? V-12 or 9 cylinder or 14 cylinder or 18 cylinder?
French tried a few planes with 700hp 14 cylinder radials, spark plug and valve adjustment were going to take pretty much the same time as a 900-1200h 14 cylinder radial. time it takes to open and close the cowl vs the time it takes to do the plug change and valve check/adjustment?

Some planes were designed for better access or fewer parts. But a lot of airframes were designed to go for several hundred hours without taking the basic airframe apart.
Repair battle or crash damage is a bit different than normal maintenance.

And if you sacrifice combat effectiveness for ease of maintenance/repair you may wind up doing a lot more repair

I think the "light fighter" concept was very tricky to implement successfully, partly because of the reason you cite here (can't reduce size or weight of a lot of militarily necessary kit, like radios) and partly due to difficulties with the smaller engines. That in turn, was in large part because most of the development effort, money, and time was applied toward the larger more powerful engines. Also partly it was because most of these designs were not very seriously pursued by the firms which built them.

But we do see some examples which were very or at least partly successful. And there are some reasons why this is not such a bad idea from a design perspective. Thinking seriously about reducing weight, cost of production, and improving the ease of maintenance does turn out to be quite important. Weight is the enemy of aircraft design, and this was doubly true for WW2 military aircraft.

Wasn't the F-16 initially a "light fighter"? During WW2, as noted already in the part of the thread I read so far (up to this post) the Soviet fighters including Yak-1 / 7 / 9, LaGG-3 and La 5 were initially at least, basically light fighter concepts. They had many challenges making them work, but ultimately these designs were successful. And based on the ubiquitous Hispano 12Y engine that I know you dislike, but which seemed to be a pretty effective and important piece of kit during the war, just like the Hispano 20mm gun was (in spite of it's flaws).

The Mosquito was also initially a 'light' design though of course it used Merlin engines. The Westland Whirlwind, which we have discussed here many times previously, used the little Peregrine engines that got discontinued, but it was quite a good fighter and strafer with a great deal of longevity as a design, as a 1940 design still proving useful without any real upgrades well into 1942.

I'll even go to a somewhat outlier position here and note that the CW-21 was an (arguably) effective design which could have proven useful as a point defense fighter. It had rather mediocre outcomes in the Pacific but that was mainly because of the general tactical situation. You could also argue (though this too is maybe a stretch I admit) that some of the later war high tech super weapons of the Germans, like the He 162 "Salamander" jet fighter and the Me 163 "Komet" rocket fighter, were at least somewhat successful and relatively simple point-defense designs, even though they relied on sophisticated concepts.

 

[Wild_Bill_Kelso]

It had no future. Some what is said about it is a bit dubious, not going to say impossible but dubious.
It was 'supposed' to have flown with full armament starting at it's first flight.
Trouble is no known photograph shows guns, gun hatches, cartridge ejection slots. Like
View attachment 739865
Maybe they took the guns out and covered up the openings? Then you get stuff like this "The compact radial engine gave the Venom a better rate of roll and turn than its long nosed water-cooled competitors but it was soon clear the potential power from the Merlin was greater than was likely to be available from the Aquila in the near future, with only limited development of this engine being undertaken, while no other engines were available suitable for fitting in such a small airframe."

Hmmm.
1650 cu in vs 950 cu in engine.
Potential power was all too clear.

Yeah I noticed the photo showed no guns, although those might be two ejector ports on the wings.

I suspect something like that could have been useful in the Pacific if it had even say, four .303 guns... if it made the speed claimed in the Wiki.

 

[Shortround6]

Quite a lot here

I think the "light fighter" concept was very tricky to implement successfully, partly because of the reason you cite here (can't reduce size or weight of a lot of militarily necessary kit, like radios) and partly due to difficulties with the smaller engines. That in turn, was in large part because most of the development effort, money, and time was applied toward the larger more powerful engines. Also partly it was because most of these designs were not very seriously pursued by the firms which built them.

There are number of reasons for the problems with designing the light fighter and their engines. P & W had the R-1535 14 cylinder radial which the US Navy rather liked during the 1930s. However nobody else liked it. 14 Cylinders was too expensive for commercial operators to buy/maintain when they could get the same (or more?) power from 9 cylinder engines. Army didn't by any either. P & W saw the handwriting on the wall and canceled further development. Which contributed to the end of the Grumman F5F. But that required two engines, more on that later. P & W only had so much design staff to go around. And they went off in several different directions including a trip to sleeve valve land which sucked up a lot of time money for very little return. With war looming a change of management not only stopped sleeve valves and all liquid cooled engines but also the R-2180 14cylinder radial, which should have been low risk. Just use 14 R-2800 cylinders instead of 18. But the aircraft designers decided to go big or go home. Or to stick with the R-1830 engine.
A lot of this was marketing and the economics of building engines in large quantities. Unfortunately in the middle of the 1930s many companies were scrabbling for each and every sale and tried offering too great a variety of different products trying to keep the doors open one more year (or one more month) and R & D was not quite what it could have been.
However even a glance at the R-1830 and R-2800 show the difference.
engine......................................R-1830..............................R-2800
Take-off...................................1200hp.............................1850hp
Military power hi.................1050hp/13,100ft .........1500hp/14,000ft
Weight.......................................1460lbs..........................2300lb
Now the R-1830 was after 5-6 years of development and the R-2800 was the first production model made. And for a twin (bomber or transport) you had 28 cylinders compared to 36.
If you tried for tri motor you had the power but you had a lot more maintenance. Yes they are not light fighters but help show why some companies were not interested in developing light fighter engine.
The CW-21 used R-1820 engines that were actually one or two generations behind what CW was capable of building. I have never seen the explanation of that. I don't know if they didn't have the production capability, R-1820s at the time were being built with 3 different crankcases and with different cylinders. I don't know if the airframe wasn't strong enough to handle the higher power?

But we do see some examples which were very or at least partly successful. And there are some reasons why this is not such a bad idea from a design perspective. Thinking seriously about reducing weight, cost of production, and improving the ease of maintenance does turn out to be quite important. Weight is the enemy of aircraft design, and this was doubly true for WW2 military aircraft.

We also have to be very careful about comparing things from different times or the same time in different countries. things changed a lot in just a few years. All of those things were very important but building planes that could not actually do the job was not good. Unfortunately sometimes both expected engine power and expected aircraft weight tended to be optimistic. Sometimes wildly so.

Wasn't the F-16 initially a "light fighter"? During WW2, as noted already in the part of the thread I read so far (up to this post) the Soviet fighters including Yak-1 / 7 / 9, LaGG-3 and La 5 were initially at least, basically light fighter concepts. They had many challenges making them work, but ultimately these designs were successful. And based on the ubiquitous Hispano 12Y engine that I know you dislike, but which seemed to be a pretty effective and important piece of kit during the war, just like the Hispano 20mm gun was (in spite of it's flaws).

There have been several attempts to reduce the size of the fighters in the jet age, sometimes successful, sometimes not so successful. And a lot of time electronics advanced more rapidly that the airframes and engines so what started as a daylight only fighter changed into an all weather fighter as electronics got smaller, lighter, smarter.
Also be very careful with jet engines. The engine in an early (but not real early) F-16 was actually about 150lbs lighter than the engines in the early F4 Phantom but gave almost 40% more power. There were a few attempts to make light fighters in the 1950s as jet engine technology made huge changes. In fact the engine in the early F-16 was within about 100lbs of the J-47-33 engine used in the last F-86 Sabre jets. Those kinds of changes opened up all kinds of possibilities. But they also require time machines to compare designs.

As far as the Soviet piston engines fighters go, I guess it really depends on the definition of a light fighter.
Yak-1..............................6382lbs normal load
Yak-7B...........................6719lb
Yak-9D..........................6871lb
Lagg-3.........................6834lb (?)
LA-5..............................7098lb
Spitfire Vb Trop........6695lb
P-40B............................7352lb
D. 520...........................5900lb
MC 202........................6460lb (max)
109G-6.........................6940lb

The Soviet fighters were only light in comparison to American fighters or British Typhoon. They were pretty much standard on the world stage of 1940-42.
The Soviet failure to develop the follow-ons to the M-105 engine greatly hindered the development of Soviet fighter aircraft.

The Mosquito was also initially a 'light' design though of course it used Merlin engines. The Westland Whirlwind, which we have discussed here many times previously, used the little Peregrine engines that got discontinued, but it was quite a good fighter and strafer with a great deal of longevity as a design, as a 1940 design still proving useful without any real upgrades well into 1942.

The Whirlwind is kind of a special case, it was wasn't really a light "Twin" in the sense that a P-38 was a twin. It was much more an 1800hp fighter that used two engines than a fighter that used a single 1800-2000hp engine. Basically the same guns and range as an Early Typhoon or Tornado. Used two 12s vs a single 24. P-38 used twin 1100hp engines to start but they stuck in enough fuel to have twice the endurance of a single seat/single engine fighter.

I'll even go to a somewhat outlier position here and note that the CW-21 was an (arguably) effective design which could have proven useful as a point defense fighter. It had rather mediocre outcomes in the Pacific but that was mainly because of the general tactical situation. You could also argue (though this too is maybe a stretch I admit) that some of the later war high tech super weapons of the Germans, like the He 162 "Salamander" jet fighter and the Me 163 "Komet" rocket fighter, were at least somewhat successful and relatively simple point-defense designs, even though they relied on sophisticated concepts.

Well the two Germans were Nickle rockets and were more akin to human guided AA missiles than actual fighters. If the bombers didn't fly pretty much over the right city they could not intercept even a few score of miles away.

The CW-21B helps illustrate the problem.
The engine was rated at 1000hp for take-off, however there were not military ratings for that engine. Max continuous was 850hp at 6,000ft and 750hp at 15,100ft.
Fuel was a max of 120 gal but was probably at 5000lbs weight for take-off, Normal gross was 4500lbs and so a lot fuel disappears. The famous climb was also subject to question
The 4,500fpm to start seems to have petered out to 3280fpm or worse. 4 minutes to 13,200ft.
as the armament seems to have been, shall we say, flexible? it was designed to hold two .50s and two .30s but there is no evidence that any were so fitted.
Claims are made for one .50 and one .30. One was tested with four .303s and some records say that the 21-Bs were delivered with two .30s.

the useful load for a 4500 gross weight was 1118lbs, If you stick in a pair of .50s with 200rpg you have about 250lbs for guns/ammo, the standard 200lbs for pilot, a bit over 50lbs for oil, and just about 100 US gallons for fuel. Oh, you want a radio? You want the extra two .30s, any other extras? like oxygen, a flare gun?
Even four small Brownings and 350rpg is just over 200lbs.

You want the engine from a Buffalo MK I? add around 160lbs. Swap the engine from a F2A-3? add another 40lbs, may need a bigger prop than the standard 9 footer. Buffalo's used either a 10'1" or a 10'3in depending make/model.

And if you decide you want armor or any fuel tank protection, even a CO2 bottle?

That is the problem with light weight fighters, you have less capability.
The P-40B had a 1737lb useful load to divide up between guns/ammo, oil/fuel (120 US gallons), pilot, armor, and equipment.

P-40Bs didn't have drop tanks or bombs as built.

 

[GrauGeist]

The La-5 was developed from the LaGG-3/LaGG-1, the latter two being developed with "non-strategic" materials (laminated wood), but were underpowered and dangerous to fly.

Stalin was displeased with Lavochkin, who successfully mated the front end of a Su-2 to a LaGG-3, thus redeeming himself with Uncle Joe.
There was no weight saving/compact fighter intention, just an attempt to bring the LaGG-3's performance up to a standard that would match the Bf109/Fw190.

Of course, the prospect of catching the "Stalin Flu" was a great motivator, too...

 

[Wild_Bill_Kelso]

Quite a lot here

There are number of reasons for the problems with designing the light fighter and their engines. P & W had the R-1535 14 cylinder radial which the US Navy rather liked during the 1930s. However nobody else liked it. 14 Cylinders was too expensive for commercial operators to buy/maintain when they could get the same (or more?) power from 9 cylinder engines. Army didn't by any either. P & W saw the handwriting on the wall and canceled further development. Which contributed to the end of the Grumman F5F. But that required two engines, more on that later. P & W only had so much design staff to go around. And they went off in several different directions including a trip to sleeve valve land which sucked up a lot of time money for very little return. With war looming a change of management not only stopped sleeve valves and all liquid cooled engines but also the R-2180 14cylinder radial, which should have been low risk. Just use 14 R-2800 cylinders instead of 18. But the aircraft designers decided to go big or go home. Or to stick with the R-1830 engine.
A lot of this was marketing and the economics of building engines in large quantities. Unfortunately in the middle of the 1930s many companies were scrabbling for each and every sale and tried offering too great a variety of different products trying to keep the doors open one more year (or one more month) and R & D was not quite what it could have been.
However even a glance at the R-1830 and R-2800 show the difference.
engine......................................R-1830..............................R-2800
Take-off...................................1200hp.............................1850hp
Military power hi.................1050hp/13,100ft .........1500hp/14,000ft
Weight.......................................1460lbs..........................2300lb
Now the R-1830 was after 5-6 years of development and the R-2800 was the first production model made. And for a twin (bomber or transport) you had 28 cylinders compared to 36.
If you tried for tri motor you had the power but you had a lot more maintenance. Yes they are not light fighters but help show why some companies were not interested in developing light fighter engine.
The CW-21 used R-1820 engines that were actually one or two generations behind what CW was capable of building. I have never seen the explanation of that. I don't know if they didn't have the production capability, R-1820s at the time were being built with 3 different crankcases and with different cylinders. I don't know if the airframe wasn't strong enough to handle the higher power?

We also have to be very careful about comparing things from different times or the same time in different countries. things changed a lot in just a few years. All of those things were very important but building planes that could not actually do the job was not good. Unfortunately sometimes both expected engine power and expected aircraft weight tended to be optimistic. Sometimes wildly so.

There have been several attempts to reduce the size of the fighters in the jet age, sometimes successful, sometimes not so successful. And a lot of time electronics advanced more rapidly that the airframes and engines so what started as a daylight only fighter changed into an all weather fighter as electronics got smaller, lighter, smarter.
Also be very careful with jet engines. The engine in an early (but not real early) F-16 was actually about 150lbs lighter than the engines in the early F4 Phantom but gave almost 40% more power. There were a few attempts to make light fighters in the 1950s as jet engine technology made huge changes. In fact the engine in the early F-16 was within about 100lbs of the J-47-33 engine used in the last F-86 Sabre jets. Those kinds of changes opened up all kinds of possibilities. But they also require time machines to compare designs.

As far as the Soviet piston engines fighters go, I guess it really depends on the definition of a light fighter.
Yak-1..............................6382lbs normal load
Yak-7B...........................6719lb
Yak-9D..........................6871lb
Lagg-3.........................6834lb (?)
LA-5..............................7098lb
Spitfire Vb Trop........6695lb
P-40B............................7352lb
D. 520...........................5900lb
MC 202........................6460lb (max)
109G-6.........................6940lb

The Soviet fighters were only light in comparison to American fighters or British Typhoon. They were pretty much standard on the world stage of 1940-42.
The Soviet failure to develop the follow-ons to the M-105 engine greatly hindered the development of Soviet fighter aircraft.


The Whirlwind is kind of a special case, it was wasn't really a light "Twin" in the sense that a P-38 was a twin. It was much more an 1800hp fighter that used two engines than a fighter that used a single 1800-2000hp engine. Basically the same guns and range as an Early Typhoon or Tornado. Used two 12s vs a single 24. P-38 used twin 1100hp engines to start but they stuck in enough fuel to have twice the endurance of a single seat/single engine fighter.

Well the two Germans were Nickle rockets and were more akin to human guided AA missiles than actual fighters. If the bombers didn't fly pretty much over the right city they could not intercept even a few score of miles away.

The CW-21B helps illustrate the problem.
The engine was rated at 1000hp for take-off, however there were not military ratings for that engine. Max continuous was 850hp at 6,000ft and 750hp at 15,100ft.
Fuel was a max of 120 gal but was probably at 5000lbs weight for take-off, Normal gross was 4500lbs and so a lot fuel disappears. The famous climb was also subject to question
The 4,500fpm to start seems to have petered out to 3280fpm or worse. 4 minutes to 13,200ft.
as the armament seems to have been, shall we say, flexible? it was designed to hold two .50s and two .30s but there is no evidence that any were so fitted.
Claims are made for one .50 and one .30. One was tested with four .303s and some records say that the 21-Bs were delivered with two .30s.

the useful load for a 4500 gross weight was 1118lbs, If you stick in a pair of .50s with 200rpg you have about 250lbs for guns/ammo, the standard 200lbs for pilot, a bit over 50lbs for oil, and just about 100 US gallons for fuel. Oh, you want a radio? You want the extra two .30s, any other extras? like oxygen, a flare gun?
Even four small Brownings and 350rpg is just over 200lbs.

You want the engine from a Buffalo MK I? add around 160lbs. Swap the engine from a F2A-3? add another 40lbs, may need a bigger prop than the standard 9 footer. Buffalo's used either a 10'1" or a 10'3in depending make/model.

And if you decide you want armor or any fuel tank protection, even a CO2 bottle?

That is the problem with light weight fighters, you have less capability.
The P-40B had a 1737lb useful load to divide up between guns/ammo, oil/fuel (120 US gallons), pilot, armor, and equipment.

P-40Bs didn't have drop tanks or bombs as built.

You make several good points and I confused the issue a bit by using the term 'lightweight'. I'm really talking about the broader idea in the OP i.e. "Sten" which can mean lightweight but also means simple and / or cheap, but effective. The "lightweight" idea is only part of it.

I think the CW -21 and Whirlwind were actually lightweight fighters, IMO, but I'll come back to those.

The Soviet fighters were not quite that light, I could quibble on some of your numbers but you are right they were not a whole lot lighter than a Spitfire. But they were simple, they were cheap. They were quite small. No-frills, typically carrying one to three guns, only one of which was a cannon.

But unlike most of the Lend Lease aircraft sent to Russia by England and the US, they could operate just fine in the winter, worked well in awful field conditions, ran fine on Soviet low octane gasoline, didn't seem to require clean oil, and so forth.

As for the issues with the LaGG-3, I think those are actually a bit exaggerated. To be honest, I think we got Uncle Joe's propaganda version of this story. I've read a lot about it, and the conclusion I came to is that most of the problems with the LaGG-3 were not really design issues so much as manufacturing issues. There were design problems too, and it was a little too heavy for the relatively small 12-Y derived engine - especially in the earliest versions with a lot of guns. But the thing is, all of the early Soviet fighters had this problem, and by far the manufacturing issues were the biggest part of it. Most of the design issues with the LaGG-3 were fixed or substantially improved. The last blocks of them were pretty good.

All of the early models of the 'new' Soviet fighters had problems like - wheel wells that would come open in flight, the canopy release which was considered so unreliable that many pilots flew without them (losing what, 50 to 80 mph in speed?) they had problems with special birch plywood on the wings and fuselages delaminating. Guns jammed or even caught fire. There were electrical shorts that kept the radios from working, bad paint that ate holes into fueslages and disintegrated the cloth cover on the control surfaces, they had gaps and holes in the fuselage that air came through (many were described as 'whistling' in flight). Parts were also not interchangable between aircraft from different factories, or sometimes between aircraft from the same factory.

Most of these issues were at least to some extent also problems with a lot of British and American planes too, in the very early days. They were just fairly quickly ironed out. The Soviets took a little longer to sort it all out because they had to move all their factories and some assembly lines were outdoors, even in the winter! But these same problems occurred with the Yak fighters as well. I think Stalin just liked Yakovlev better.

But circling back to the Sten Gun idea. These planes really were "Sten Guns". Eventually they worked out the worst of the problem, I think a lot of them were sorted out by the end of 1942. Just as the Soviets were fixing or finding improved approaches to a whole lot of other issues.

These little planes had short range, just a few guns but concentrated in the nose and trained to shoot from close range so it didn't matter so much. These Soviet fighters could operate in conditions that the Germans and most of the Western supplied fighters could not (or not as well, or with more difficulty). They were simple, and didn't have all the features that German or British planes had. But they had enough to do their job. They had little valves built in for all fluids so they could be drained when it got down to 60 below. That kind of thing had to be added to P-39s or Bf 109s. They didn't have as many instruments or nice features as some of the Western aircraft, but they had enough.

As for the CW-21. it's a light point defense fighter. It's made for defending the airfield it's flying out of, and whatever is in the immediate vicinity like the factory or the port it's right next to. It doesn't need a dinghy or a whole lot of fuel, a flare gun, or a radio. Maybe oxygen but it probably is going to be a short flight so not that much. It didn't have self sealing tanks but neither did Hawk 75s / Mohawks and they did fairly well with those.

Whirlwind is somewhat unique but I'd say is a light fighter - for a twin. Let's put it this way, it was a more viable 'heavy fighter' than most other aircraft that were designed for that role, precisely because it was so small. But it still had unique capabilities that a Hurricane, or a Typhoon didn't have. It had better range! That is why I was saying a while back it would have been very helpful to have in North Africa.


Ultimately as we know, the biggest impediment to speed in WW2 fighters was drag, more so than weight. "Lightweight" fighter designs were often heavier than originally intended, but if they were made smaller that often translated to faster. It wasn't until much later in the war that larger aircraft, usually with a bit bigger engines, were able to fly as fast.

 

[Shortround6]

The Soviet fighters were not quite that light, I could quibble on some of your numbers but you are right they were not a whole lot lighter than a Spitfire. But they were simple, they were cheap. They were quite small. No-frills, typically carrying one to three guns, only one of which was a cannon.

I actually had trouble picking numbers for the Soviet fighters so quibble away, I had 8 numbers to choose from just on the Yak-1 from 6,078lb to 6,468lb depending year, engine and armament. Spitfires were both largish and light, at least they had a big wing . The D 520, Bf 109 and MC 202 were about the same size as Soviet fighters, I am not going to argue about 10 sq ft or so. French were using a single cannon and 4 LMGs, Germans were using a single cannon and two LMGs until 1942. (Not counting the 190 here). So the Soviet fighters were not really lighter armed than many other fighters (Italian and Japanese Army were worse in the early years).

These little planes had short range, just a few guns but concentrated in the nose and trained to shoot from close range so it didn't matter so much. These Soviet fighters could operate in conditions that the Germans and most of the Western supplied fighters could not (or not as well, or with more difficulty). They were simple, and didn't have all the features that German or British planes had. But they had enough to do their job.

Soviet pilots were barley trained to fly, they were "told" to get close, gunnery training completed
However the Soviet planes could not do what some of the German or British (or American or Japanese or other) fighters could. They often did not have instruments that allowed for "blind flying" like flying through clouds. Or being able to navigate long distances, their long Yaks had extra equipment fitted.
The Soviet fighters had enough equipment to their job on the Eastern front under the conditions they were operating in with acceptable operational losses (to the soviets). Does not mean they were good solution for anybody else. Soviet fighters in the Pacific? Poor range, poor navigation, poor performance at high altitudes and not talking turbo-charger land here either.
The Soviets had some real problems, they were somewhat stuck with the M-105 engine. They had made prototypes of both the M-106 and M-107 engines before the Germans had invaded and were hoping to get them into production and solve the power problem with the higher powered engines, but they both took more development that originally thought and forced the quickey modification of the M-105PF engine, lower the supercharger gears, run it harder and accept less engine life. Not what they want, it was what they could do to stop the invasion. Necessity did not make it a virtue. Same with the armament. They wanted more/bigger guns. They tried putting in more in originals or at times during production but the increased weight lowered performance more than they would accept. There were other problems at times. The LA-5 worked, but only just. Soviets were also having trouble building enough guns, but the LA-5 also had a weight problem. The LA-5 only got 3 guns when they came up with a new, lighter gun than the standard one. They also had to reduce the number of rounds per gun. Yes it worked, but the two 20mm in cowl was not what they wanted, it was what they had to accept.
Soviets didn't have to shoot down large 4 engine bombers, they didn't have to fly long distance, they didn't have to fly over water (German and British lost pilots getting lost over the Channel) mostly. They often never flew over 12,000ft (sort of the dividing line for oxygen). They did what worked for them, it didn't mean they actually liked it as they knew that if conditions changed they were stuck.

 

[yulzari]

Bill is right that we have drifted from the 'Sten' OP to 'lightweight fighter' as the subject.

Consider the Sten. It was not a lightweight machine carbine. It was lighter than many but as a consequence rather than by doctrine. It was production optimised to use dispersed subcontractors and not (other than barrel rifling) impinging upon the existing firearms manufacturing capacity. It used a typical machine carbine ammunition and magazine. Nothing was in a reduced power form. One could have made it as a 'lightweight' with .32acp instead of 9x19mm Parabellum and based it around a fully automatic pistol with a shoulder stock but the model was full size but quick and cheap to use semi skilled and unskilled labour.

That would seem to be the model for a fighter to fit the OP. Such as the Miles proposal to use surplus RR Kestrels in a single seater Miles Master.

 

[GrauGeist]

The Soviets were toying with "lightweight" fighter concepts like most other nations, but like the other lightweight fighters, went nowhere.

There was the Polikarpov I-17 and one other (who's name escapes me at the moment) that had an evaporative cooling system.

 

[Frog]

Bill is right that we have drifted from the 'Sten' OP to 'lightweight fighter' as the subject.

Consider the Sten. It was not a lightweight machine carbine. It was lighter than many but as a consequence rather than by doctrine. It was production optimised to use dispersed subcontractors and not (other than barrel rifling) impinging upon the existing firearms manufacturing capacity. It used a typical machine carbine ammunition and magazine. Nothing was in a reduced power form. One could have made it as a 'lightweight' with .32acp instead of 9x19mm Parabellum and based it around a fully automatic pistol with a shoulder stock but the model was full size but quick and cheap to use semi skilled and unskilled labour.

That would seem to be the model for a fighter to fit the OP. Such as the Miles proposal to use surplus RR Kestrels in a single seater Miles Master.

Plain to the bone as it is, the Sten has a luxury that its MP 40 opponent lacks : a fire selector.

 

[Wild_Bill_Kelso]

I actually had trouble picking numbers for the Soviet fighters so quibble away, I had 8 numbers to choose from just on the Yak-1 from 6,078lb to 6,468lb depending year, engine and armament.

Yes in fact it's worse than that because aircraft of the same exact type and subtype coming from the same factory could vary by as much as 200 lbs incredibly, at least in the early days. And one factory may be making a Yak-1 that weighs 6,200 lbs while another one nearby makes them (of exactly the same sub-type) at 6,500 lbs and it's not clear why.

Spitfires were both largish and light, at least they had a big wing .

Spitfire has a pretty big wing but I would say it's quite a small plane. This was part of the reason for it's long lasting success, IMO. It's noticeably small compared to most later war planes on my model shelf behind me.

The D 520, Bf 109 and MC 202 were about the same size as Soviet fighters, I am not going to argue about 10 sq ft or so. French were using a single cannon and 4 LMGs,

I think the D.520 is also a quite small aircraft. I'm not sure about the degree of complexity or expense, but it's small and that was a big help (and for the same reason as the Soviet fighters, because it had more or less the same engine)

Germans were using a single cannon and two LMGs until 1942. (Not counting the 190 here). So the Soviet fighters were not really lighter armed than many other fighters (Italian and Japanese Army were worse in the early years).

The Bf 109 was a special case, and there was a moment where they went for light, particularly with the 109F2. But let's not forget the Bf 110 and Fw 190 were also German fighters...

Soviet pilots were barley trained to fly, they were "told" to get close, gunnery training completed

Well, an extremely rapid and insufficient level of fighter training was not at all unusual for any of the Allies in WW2. Fighter pilots in North Africa, Burma, Malaya, Java, Australia, New Guinea, Guadalcanal etc. were often quite poorly trained, and had almost no gunnery training specifically. The US Navy was a major exception to that.

However the Soviet planes could not do what some of the German or British (or American or Japanese or other) fighters could. They often did not have instruments that allowed for "blind flying" like flying through clouds. Or being able to navigate long distances, their long Yaks had extra equipment fitted.

And here is where it gets interesting for me, and where the idea of the thread OP dovetails pretty well...

The Soviet fighters had enough equipment to their job on the Eastern front under the conditions they were operating in with acceptable operational losses (to the soviets). Does not mean they were good solution for anybody else. Soviet fighters in the Pacific? Poor range, poor navigation, poor performance at high altitudes and not talking turbo-charger land here either.

I agree! But this is (to me) the genius of the Soviet design philosophy. Or the philosophy applied toward the adaptation of their ~1941 era designs. They did not have the big engines, and the fighting on the Russian front was heavily, heavily focused on tactical warfare. Perhaps more than anywhere else. Both the Soviets and the Germans took advantage of this, but the Soviets arguably adapted to it much more thoroughly.

You are right that they didn't have long range and most of their fighters lacked high altitude capabilities. The few that did (like MiG 3) were not good for lower altitudes. But they didn't need that. Per the "Sten" idea, they were adapted for that frontal aviation role, fighting close to their airfields, at low altitudes. Fast enough, and agile enough to hold their own with German fighters, heavily armed enough (that hub mounted 20mm was fairly accurate and powerful, and the Soviet guns were pretty good in general as you know better than I) to gradually wrest control from the Germans and allow their tactical strike aircraft to start taking an increasing toll on the German ground forces, albeit at great cost (especially for the not so much 'Sten' IL-2s).

I say this is what made it work. They had small engines, so small planes. Especially early on they lacked metals like aluminum, so they worked out how to make effective fighters out of (mostly) wood. They had a shortage of guns, and their planes couldn't take much weight anyway, so they concentrated firepower in the nose and taught their pilots to shoot from close, and not to focus on high deflection angles etc.

They did not have planes that had the range to fight in the Pacific, or range and high altitude capabilities to escort bombers from Britain, but why would they want that? Maybe later it's nice in case they want to join the war against Japan. But to save their lives from the Germans they has to focus on the #1 job at hand.

The Soviets had some real problems, they were somewhat stuck with the M-105 engine. They had made prototypes of both the M-106 and M-107 engines before the Germans had invaded and were hoping to get them into production and solve the power problem with the higher powered engines, but they both took more development that originally thought and forced the quickey modification of the M-105PF engine, lower the supercharger gears, run it harder and accept less engine life. Not what they want, it was what they could do to stop the invasion. Necessity did not make it a virtue. Same with the armament. They wanted more/bigger guns. They tried putting in more in originals or at times during production but the increased weight lowered performance more than they would accept.

Everyone wanted more / bigger guns. Sometimes this ended up causing problems as weight and drag mounted. This is, in part, why the Hurricane II was obsolete and being phased out as a fighter, at the same time that the Yak-1B, La 5, and Yak-9 were just starting to hit their stride. The P-40 could fight in Russia or in New Guinea or in North Africa, but for Russia it was not as good as a Yak-9.

There were other problems at times. The LA-5 worked, but only just. Soviets were also having trouble building enough guns, but the LA-5 also had a weight problem. The LA-5 only got 3 guns when they came up with a new, lighter gun than the standard one. They also had to reduce the number of rounds per gun. Yes it worked, but the two 20mm in cowl was not what they wanted, it was what they had to accept.

I think two 20mm guns in the cowl was pretty good. The Soviets were certainly very pleased with the La 5.

Soviets didn't have to shoot down large 4 engine bombers, they didn't have to fly long distance, they didn't have to fly over water (German and British lost pilots getting lost over the Channel) mostly. They often never flew over 12,000ft (sort of the dividing line for oxygen). They did what worked for them, it didn't mean they actually liked it as they knew that if conditions changed they were stuck.

I agree... they didn't need to shoot down four engine bombers. The Germans didn't make any substantial use of them, nor did their Italian or Balkan allies. So why add that capability, especially in the early years? They started thinking about it toward the end of the war only because it started to look like they might get into conflict with the Americans. To me, this is actually a demonstration of their strength.

I think one of the biggest problems with military aircraft design is the tendency to overbuild, to add too much gear, too many guns etc. The Sten approach was kind of like a solvent to that bloat, and for the Russians, it became a virtue out of necessity, IMO.

 

[Wild_Bill_Kelso]

The thing with a lot of the 'lightweight' fighters (which were also often 'Sten' designs) that was a problem, was they applied that same 'solvent' but did it hastily and without very serious consideration, a little too much as an afterthought. Such as for example with the Caudron 714 or the CW 21, or the D.XXI. If they had taken these projects a little bit more seriously they may have been more successful, though it's also likely that the way the Soviets were forced to do it - over time, may have been the surest path to getting it right. Eventually.

 

[z42]

One could argue that the Soviet fighters weren't really Sten fighters. To qualify a fighter as a Sten fighter the nation in question should be able to produce better fighters, but for one reason or other chooses to build a 'Sten' fighter in order to produce large numbers of cheap fighters. So something e.g. like the Miles M.20 or such.

But the Soviet fighters? Sure, they were Sten designs compared to what the UK and US were fielding in Western Europe. But they were the best the were capable of building, considering the limitations they had in engine power (and as mentioned, suited to their requirements wrt range and altitude performance). For a Soviet Sten design, what about e.g. continuing to produce the I-16 into the early 40'ies (wikipedia says production ended only in 1942)?