Lightweight fighter: how would've you done it?

[GregP]

Hello Tomo
how about something like Vickers F.5/34 Venom, 625hp Bristol Aquila, 8 7.7mm mgs, very manoeuvrable, 312mph at 16,250 ft, AUW 4,150lb wing area 146sq ft, span 32ft 2in, lenght 24ft 2in. Weak points were engine, unreliable and no other military users, so Bristol had not much interest to perfect it, a bit like RR Peregrine and because of its smallness not much growth potential.

Juha

Here's my drawing of the Venom. Not much detail because I didn't HAVE much detail. Altogether an overlooked effort that probably COULD have been very useful in a lot of situations that would normally be without air support.

 

[ThomasP]

Nice illustration!

 

[Admiral Beez]

Best lightweight fighter of WW2 has to be the A6M Zero.

 

[Ovod]

Best lightweight fighter of WW2 has to be the A6M Zero.

Indeed, followed by the Yak-3

 

[swampyankee]

The whole point of "lightweight" fighters is really "cheaper," not less massive. So, let's look at the costs in making an effective fighter aircraft (ineffective fighter aircraft are worthless....). One item is the pilot, where the costs are salary, training, and the potential costs of paying off widows and orphans. These are not going to be significantly different for any single-engine fighter, and they are important. Initial costs would include the engine, the cost of which likely increases less than linearly with power (a 2000 hp engine isn't likely to cost twice as much as a 1000 hp engine with the same altitude performance), instruments (cost is likely independent of weight for one engine), and radios (also independent of aircraft weight). Armament cost would depend on installation, and a lightweight fighter would have less armament, with fewer guns or individually less effective guns. Airframe costs savings would come in the forms of less material and (hopefully) less labor in manufacture. Running costs would be less, as there would be less fuel and oil used, but I don't see ground crews being much smaller if the same sortie rate is to be maintained. Overall, I think, a piston-engine LWF is largely an untenable idea because there wouldn't be the sort of savings in purchase and operation that some seem to have expected. On the other hand, the truly heavy weight single piston-engine fighter, like the Boeing XF8B, was also a flawed concept.


Of course, jets changed everything. Twin-engine piston-powered fighters had significant disadvantages in dynamic maneuverability when compared with single-engine piston-powered fighters that did not apply to jet aircraft, where two engines could be placed side-by-side (or one atop the other) in the fuselage, without the increases in roll inertia and wetted area intrinsic to twin-engine piston aircraft (except for edge cases, like the Do335).

 

[drgondog]

The whole point of "lightweight" fighters is really "cheaper," not less massive. So, let's look at the costs in making an effective fighter aircraft (ineffective fighter aircraft are worthless....). One item is the pilot, where the costs are salary, training, and the potential costs of paying off widows and orphans. These are not going to be significantly different for any single-engine fighter, and they are important. Initial costs would include the engine, the cost of which likely increases less than linearly with power (a 2000 hp engine isn't likely to cost twice as much as a 1000 hp engine with the same altitude performance), instruments (cost is likely independent of weight for one engine), and radios (also independent of aircraft weight). Armament cost would depend on installation, and a lightweight fighter would have less armament, with fewer guns or individually less effective guns. Airframe costs savings would come in the forms of less material and (hopefully) less labor in manufacture. Running costs would be less, as there would be less fuel and oil used, but I don't see ground crews being much smaller if the same sortie rate is to be maintained. Overall, I think, a piston-engine LWF is largely an untenable idea because there wouldn't be the sort of savings in purchase and operation that some seem to have expected. On the other hand, the truly heavy weight single piston-engine fighter, like the Boeing XF8B, was also a flawed concept.


Of course, jets changed everything. Twin-engine piston-powered fighters had significant disadvantages in dynamic maneuverability when compared with single-engine piston-powered fighters that did not apply to jet aircraft, where two engines could be placed side-by-side (or one atop the other) in the fuselage, without the increases in roll inertia and wetted area intrinsic to twin-engine piston aircraft (except for edge cases, like the Do335).

OTOH, while the XP-51F wasn't quite a LW, by the post definition for empty GW it Was a LW by standard of operational US fighters. It was seriously considered for 400+ unit purchase in Oct 1943. As a 4x20mm gunned Interceptor at 5490 GW empty It had 5500 fpm ROC at 67" and, according to Chilton, topped out at 7000+ and 491mph at half fuel load and 90"MP. AAF-MC didn't seemingly trust RAF standards for AoA and side loads - which is amusing because they bought the P-51H with exactly the same design standards, but it also had 55gal internal fuselage tank..

I'm pretty sure the P-51F and/or G didn't get a production contract is that it was clear that more internal fuel than 205 gal was going to be required - and zero possibility of installing a fuse tank in either the F or the G..... hence the H

 

[Shortround6]

Best lightweight fighter of WW2 has to be the A6M Zero.

Indeed, followed by the Yak-3

Mighty thin definition of "light weight fighter"
Going strictly by weight a MK I Spitfire was "lighter" than a Yak-3.

An A6M was certainly no cheaper or easier to make than other Japanese fighter plane of 1939-41.(Army Ki-44 prototypes excepted?)

 

[Just Schmidt]

This is not possible, as it requires both hindsight and realistic assessment of one's own capability vs. your opponent. I may be told other reasons why it can't be done, but then at least I've learned something.

Anyway with these reservations, I'd go to the Soviet union and make a dedicated light weight rammer. I'd take the basic I-16 design but go back to one of the early engines, the one that had the best power to weight ratio. I'm not near my books, so not entirely sure it dosn't weigh too much, but I guess it shouldn't.

Now I delete the flaps and the landing gear. The idea is to let the TB 3 lift them into the air, as was done in the version carrying its own escort fighters. With the redused weight and no requirement to take off or land, it should be possible to have a smaller wing. The easy road is just cutiing the span, but preferably a more extensively modified wing should be custom designed, benefitting from lighter structure also. When it comes to armament one mashine gun should be retained just to keep the Germans honest. It should be possible to cut down on the fuel load also. I will be generous and let the pilot keep the parachute. As we must have it ready in 40, it should be possible to have quite a few available in summer 41, whether modified old models or those with the new wing.

The two biggest problems are getting the TB 3's airborne in time, and that I'd be shot after presenting the idea, it obviously being defeatist. But there you have it, by the way this should show why I usually don't do this kind of thing.

 

[Shortround6]

I may be told other reasons why it can't be done, but then at least I've learned something.

I will try to keep my comments somewhat reasonable

. I'd take the basic I-16 design but go back to one of the early engines, the one that had the best power to weight ratio.

I-16s used two basic engines, the really old ones used the M-22 engine which was a licensed (British or French?) Bristol Jupiter engine.
The somewhat newer ones got M-25s were where licensed Wright Cyclone "F" engines. The M-62 and M-63 show up in the late teen versions and/or early 20s, These are either licience built later version Cyclones or "developed" from the M-25, probably with Wright help.
The M-22 has got crap for power. About 480hp and it is the size of the M-25/Cyclone. Only weighs around 830-850lbs.
The M-25 is only kind of crappy for power. depending on version it went from around 700hp to 775hp, a later version (1941) got 790hp. Weight was on the mid 900lb range.
The M-62 was a major jump in power, with about 1000hp max power, weights went 1150lbs for direct drive and 1250lbs for reduction gear engines.

Any I-16 has the streamlining of a barn door.

The easy road is just cutiing the span, but preferably a more extensively modified wing should be custom designed, benefitting from lighter structure also. When it comes to armament one mashine gun should be retained just to keep the Germans honest. It should be possible to cut down on the fuel load also. I will be generous and let the pilot keep the parachute.

Getting rid of the landing gear and flaps make the plane cheaper, it won't do much for speed. It also guarantees the plane is a one use aircraft. Once launched it will crash wither or not it even comes close to the enemy or not. I have no idea if that is good economics or not. A lot of regular fighter aircraft never shot down an enemy. But a lot of ramming attacks also failed.
Using TB3 carriers you do have to keep the TB3s outside the action. It is one thing to launch dive bombers from dozens of miles from the target. The ground target/s (bridges?) don't move. How far away from a bomber formation do the I-16 Ram aircraft have to be launched? or rather how far away can they be launched?
With even a He 111 flying 50-100% faster (cruising) than the TB-3s timing of the launch of the I-16s is going to be be critical. Launch from too far away and the Germans only have to drop bombs, turn and runaway for a long, long stern chase with the Russians loosing 100% of the attacking fighters. Then come back the next day to bomb the target.

 

[GregP]

The actual performance of the I-16 makes your statement about the streamlining false. It went 304 mph on an engine that, under the best circumstances, made about 1,100 hp but, more often, made less than 1,000 hp in service. The A6M Zero made just over 300 mph on 940 hp and was very light, to the point of being almost dangerous in combat when the punishment was incoming instead of outgoing. So, the I-16 doesn't come off too badly when compared to the early Zeros, at least in speed. That says something positive about it's aerodynamic shape, don't you think?

You don't start seeing better-performing airplanes until the HP gets over 1,200 or so, and the FM-2 goes to ,1350 - 1,425 hp to get it's sparkling performance. The standard F4F Wildcat was slower than the I-16, and it had 1,200 hp.

Just pointing out it wasn't a slouch, though it might LOOK like one.

 

[nuuumannn]

The whole point of "lightweight" fighters is really "cheaper," not less massive.

I agree to a point, but does one require the criteria of the other to constitute the definition of a "lightweight fighter"?

For example, the I-16's gross weight (according to Wikipedia via Istoriia konstruktskii samoletov v SSSR do 1938) is 4,279 lbs, it was intended for series production and service with the VVS as its frontline fighter - was it particularly cheap compared to its contemporaries in service at the same time it entered service in 1935? The CW-21 is definitely a lightweight fighter, it had a gross weight of 4,500 lbs (Curtiss Aircraft 1907-1947), but was it particularly cheap to manufacture, given it was all metal and is beautifully formed, requiring quite a bit of skill making compound curves in sheet metal structure?

The CAC Boomerang was a stop-gap fighter and was designed to use existing aircraft components, being based on the Wirraway and accumulated experience building that type, but by comparison was more than 3,000 lbs heavier at gross weight (according to Wiki via The Great Book of Fighters and The Commonwealth Boomerang) than the I-16 and CW-21. Another stop-gap type fighter to be built from non-strategic materials and a labour force used to working with wood (coach-builders, furniture makers etc) and the engine installation from a Beaufighter II, thereby offering cost savings in manufacture and time, the Miles M.20 was just over 50 pounds lighter than the Boomerang (The British Fighter since 1912, Miles Aircraft since 1925). By comparison, the Spitfire Mk.I was a thousand pounds lighter than the both of them (Supermarine Aircraft since 1914), but it's not a lightweight fighter, nor was it particularly cheap to build.

 

[nuuumannn]

Basically, what I'm trying to say is that if you want an affordable fighter, it might not necessarily be lightweight and if you want a lightweight fighter it might not necessarily be cheap to build. This of course depends on the criteria of each requirement for each fighter type and the reasons behind them.

 

[FLYBOYJ]

A few comments -

I don't believe the I-16 had streamlining issues, if anything for it's day I think it was quite streamlined.

If I recall Polikarpov conducted extensive aerodynamic research in the basic design of the I-16 to ensure it was fast and highly maneuverable. This combined with the construction methods of the day (1933/ 34) would result in a "very light" aircraft when compared to other fighter aircraft that would come along several years later, so by the late 30s the I-16 would be considered light weight when compared to such aircraft as the BF109, Spitfire and P-36. Aerodynamically it was advanced, construction and systems wise, it was about contemporary to the early 1930s. Compare with the I-15, P-26, CR32, PZL.11 and their weights, all developed around the same time.

 

[Ovod]

Mighty thin definition of "light weight fighter"
Going strictly by weight a MK I Spitfire was "lighter" than a Yak-3.

An A6M was certainly no cheaper or easier to make than other Japanese fighter plane of 1939-41.(Army Ki-44 prototypes excepted?)

I'm pretty sure a 1943 Yak 3 was considerably lighter than a 1939 Spitfire. The Yak was certainly a lightweight fighter compared to other new aircraft designs from the latter years of the war.

 

[don4331]

Anyway with these reservations, I'd go to the Soviet union and make a dedicated light weight rammer. I'd take the basic I-16 design but go back to one of the early engines, the one that had the best power to weight ratio. I'm not near my books, so not entirely sure it doesn't weigh too much, but I guess it shouldn't.

Now I delete the flaps and the landing gear. The idea is to let the TB 3 lift them into the air, as was done in the version carrying its own escort fighters. With the reduced weight and no requirement to take off or land, it should be possible to have a smaller wing. The easy road is just cutting the span, but preferably a more extensively modified wing should be custom designed, benefiting from lighter structure also. When it comes to armament one machine gun should be retained just to keep the Germans honest. It should be possible to cut down on the fuel load also. I will be generous and let the pilot keep the parachute. As we must have it ready in 40, it should be possible to have quite a few available in summer 41, whether modified old models or those with the new wing.

The two biggest problems are getting the TB 3's airborne in time, and that I'd be shot after presenting the idea, it obviously being defeatist. But there you have it, by the way this should show why I usually don't do this kind of thing.

I was thinking something similar, but not quite as radical.

Similarly, I planned to delete the landing gear - I was going to go with skid ala Me.163 (Spitfire has >6% of weight tied up in its landing gear) as I was planning to reuse the plane. I was thinking catapult for launch, but your use of bomber/cargo plane to lift to altitude might be better idea - it would save all the fuel fraction needed to climb to release altitude.

I was going with 3 synchronized HMG - one through propeller hub and other pair in wing roots. For engine, I was thinking small V-8 - somewhere around 450-500 cid e.g. As.401, boosted like the Schneider Cup engine. Cowling like de Havilland Albatross. Some mechanism to stop the 2 blade prop horizontal for landing. No radio, no IFF transmitter, you get your last minute instructions from the mother ship just be for you're cut loose; we'll talk again after you land.

Something like Fi-103R, but with ICE and guns as a fighter, not a suicide bomber.

 

[wlewisiii]

Every time I think of things like this, I ponder if the CW-21 could have been stressed for the R-2600 or R-2800. Arm it with 4 .50's, centerline bomb and underwing fuel drop tanks. That would add a 1000 lbs though (mostly the bigger engine) and still not have armor or self-sealing tanks.

 

[Shortround6]

The I-16 was about the same weight as many other fighters that entered service from 1932-35. Compare to even fixed landing monoplanes or even the Bf 109 with Jumo 210 engine.

In fact the Curtiss Hawk 75 (first flight April 1935) with the original Wright R-1670 Twin Whirlwind engine of 900hp was supposed to weigh 4,843lbs. Armament was a pair of .30 cal guns.

The Wright R-1670 Twin Whirlwind engine was such a dud that Curtiss fitted a P & W R-1535 (maybe because it was quick?) but since that didn't provide the desired performance Curtiss fitted a Wright R-1820 9 cylinder radial. And the race find an effective engine for the Hawk 75 was well under way

The I-16 doesn't become a "light weight fighter" except by default. Most of the other major countries had progressed to heavier fighter in the late 30s. The Russians themselves were trying to the stretch the I-16 though a number of projects like the I-180 (5,355lbs)


As far as the aerodynamics of the I-16 go, OK it wasn't a barn door. It was a brick.

Plane...............................wing area........................Percentage Wing area............................Fuselage length..........................Percentage Fuselage length.
I-16....................................156.........................................100%............................................................20 ft 1in..........................................100%
Buffalo.............................208..........................................1.33%..........................................................26 ft 4in...........................................1.30%
Hawk 75..........................236..........................................1.51%..........................................................28 ft 1 in..........................................1.40%
Martlet I..........................260...........................................1.66%.........................................................28 ft 7in ............................................1.42%

All planes powered by Wright R-1820s or Soviet versions. For all it's small size it didn't perform much different than the larger (very much larger?) and very much heavier American planes.
I have been saying that weight wasn't as important as some people think but take another look at the Marlet I. The size of the wing, the size of the fuselage AND the fact that the Martlet was almost 60% heavier. And that the Martlet was faster (313mph using 1000hp?) Granted it had a bit more power but the I-16 looks like it was dragging an anchor behind it.
And the Martlet I was not what springs to mind when we talk about sleek aircraft.

Note short cowl.

 

[GTX]

As a simple and quick-to-build "emergency fighter", I always liked the Miles M.20. It was available 1940 but was no lightweight. That said, it offered good performance for its day:

 

[tomo pauk]

As far as the aerodynamics of the I-16 go, OK it wasn't a barn door. It was a brick.

Plane...............................wing area........................Percentage Wing area............................Fuselage length..........................Percentage Fuselage length.
I-16....................................156.........................................100%............................................................20 ft 1in..........................................100%
Buffalo.............................208..........................................1.33%..........................................................26 ft 4in...........................................1.30%
Hawk 75..........................236..........................................1.51%..........................................................28 ft 1 in..........................................1.40%
Martlet I..........................260...........................................1.66%.........................................................28 ft 7in ............................................1.42%

All planes powered by Wright R-1820s or Soviet versions. For all it's small size it didn't perform much different than the larger (very much larger?) and very much heavier American planes.
I have been saying that weight wasn't as important as some people think but take another look at the Marlet I. The size of the wing, the size of the fuselage AND the fact that the Martlet was almost 60% heavier. And that the Martlet was faster (313mph using 1000hp?) Granted it had a bit more power but the I-16 looks like it was dragging an anchor behind it.
And the Martlet I was not what springs to mind when we talk about sleek aircraft.

Shavrov's bible gives for the I-16 Type 24, powered by M-63 engine (900-930 HP at ~14760 ft), 489 km/h as a best-case value. It could be down to 462 km/h for the same engine.
The I-16 (and MC.200?) probably needed an enclosed cockpit to gain another 10-15 mph?

The I-180 was a whole new aircraft, not just a warmed-up I-16.

 

[FLYBOYJ]

The I-16 was about the same weight as many other fighters that entered service from 1932-35. Compare to even fixed landing monoplanes or even the Bf 109 with Jumo 210 engine.

And those came about several years later. The very first -109 flew in 1935, about the first time early models of the I-16 were entering service. These -109s produced and entered service at least a year later.

Yes compare the I-16 weight (4279) with the P-26 (3,360 lb) the CR.32 (4,354 lb) the PZL.11 (3,968 lb) and then the -109 prototype (over 4000 pounds). All entering service, in service or being developed between 1932-1935.

The I-16 was probably the most advanced fighter being operated during the first half of the 1930s until such aircraft as the BF109B (1935) P-35 (1935) P-36 (1935) for examples, came along, and even when pitted against the BF 109B, the I-16 didn't do too badly, it wasn't until the -109C and subsequent was introduced when the I-16 was outclassed over Spain.

In fact the Curtiss Hawk 75 (first flight April 1935) with the original Wright R-1670 Twin Whirlwind engine of 900hp was supposed to weigh 4,843lbs. Armament was a pair of .30 cal guns.

And again, you're making a comparison with an aircraft that developed and flown several years after the I-16

The Wright R-1670 Twin Whirlwind engine was such a dud that Curtiss fitted a P & W R-1535 (maybe because it was quick?) but since that didn't provide the desired performance Curtiss fitted a Wright R-1820 9 cylinder radial. And the race find an effective engine for the Hawk 75 was well under way

The I-16 doesn't become a "light weight fighter" except by default. Most of the other major countries had progressed to heavier fighter in the late 30s. The Russians themselves were trying to the stretch the I-16 though a number of projects like the I-180 (5,355lbs)

Well it does if you're going to compare it with what you've shown (Buffalo, Hawk 75, Martlet)

Gross Weights

I-16 Type 24 - 4,279 lbs
P-36A - 5,650 lb
F4F-3 - 7,423 lb

and then for comparison

CW-21B 4,500 lbs!

All were developed 3 to 5 years AFTER the I-16 (TsKB-12 first flew late 1933)

As far as the aerodynamics of the I-16 go, OK it wasn't a barn door. It was a brick.

Plane...............................wing area........................Percentage Wing area............................Fuselage length..........................Percentage Fuselage length.
I-16....................................156.........................................100%............................................................20 ft 1in..........................................100%
Buffalo.............................208..........................................1.33%..........................................................26 ft 4in...........................................1.30%
Hawk 75..........................236..........................................1.51%..........................................................28 ft 1 in..........................................1.40%
Martlet I..........................260...........................................1.66%.........................................................28 ft 7in ............................................1.42%

All planes powered by Wright R-1820s or Soviet versions. For all it's small size it didn't perform much different than the larger (very much larger?) and very much heavier American planes.
I have been saying that weight wasn't as important as some people think but take another look at the Marlet I. The size of the wing, the size of the fuselage AND the fact that the Martlet was almost 60% heavier. And that the Martlet was faster (313mph using 1000hp?) Granted it had a bit more power but the I-16 looks like it was dragging an anchor behind it.
And the Martlet I was not what springs to mind when we talk about sleek aircraft.
View attachment 670491
Note short cowl.

And you're just showing wing area, as with weight, not a conclusive factor.

Plane...............................wing area........................wing loading
I-16....................................156.........................................27 lb/sq ft
Buffalo.............................208..........................................22 lb/sq ft without combat equipment/ 34.25 F2A-3
Hawk 75..........................236..........................................23.9
Martlet I..........................260..........................................28.59

No, the I-16 wasn't a brick either, but if we're talking mid/ late 1930s esthetics, like the Martlet, it was not a sleek aircraft but during its introduction and a few years afterwards, it was the most advanced fighter in word when compared to it's contemporaries developed during the same time period.