1937-1945: smallest, but still practical fighters?

tomo pauk

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... that are made on technology that actually existed back then. An obvious disclaimer: these will not be the best, all-singing all-dancing aircraft.

Engine is pretty much the heart of a fighter aircraft, let alone back then, however the engines chosen will be these of 'tier B', ie. not the best available. So no Merlin, no DB or Jumo 30+L V12s, no newly fanged and heavy 1500+ HP 14 cyl, let alone 18 cyl radials etc. Engines available should be no more powerful than (power at rated altitude, talk about 12000-15000 ft back then):
- for 1937-39: radials of under 850 HP, other under 750 HP
- for 1940-42: radials of under 1000 HP, other under 900 HP
- for 1943-45: radials of under 1300 HP, other under 1200 HP

Usage of turboes, 2-stage S/Cs or water-alcohol injection allowed for the fighters after 1942 (if any of that can fit on a small fighter, and if these things were actually done in the respective countries).
Initial armament is nimimal: 4 LMGs, or 2 HMGs, or a 20mm cannon + 1 LMG. Later it can grow a bit, again while keeping the size and weight in mind. No great ranges or endurances are expected, no big bombs or numerous rockets either (so it basically fits much more European expectations than those of Japan, for example).
Land-based fighters, retractable U/C.
The small fighter of 1937 should allow for a seamless engine upgrade for 1940, while the small fighter designed for 1940 should do the same for 1943. The 1937, 1940 and 1943 are the years of actual service use, so the design process needs to start a few years erarlier. If 'our' country has no suitable ebngine, feel free to licence produce other people's engines. Captured engines are fine, so is the captured weaponry.
Cancel other aircraft to move ahead with the small fighter design and production.

Possible initial engine candidates are the Kestrel, Jumo 210, HS 12X, Twin Wasp Jr, Mercury, Fiat AS.33 and A.74, I-F Delta etc.
 
British: a monoplane (doh) powered by the Mercury engine, sorta the Fokker D.XXI with retractable U/C. In Finland, retractable U/C gained in average ~25 km/h (see details). Or, Gloster going immediately with the F.5/34-lookalike.
(similar fighter would've been a ticket to Poland, too)
 
I've always liked the Ambrosini 207/403 as some of the most practical lightweight fighters that had decent performance, didn't appear to have major issues, and used non strategic materials. I don't think anything stops these being built earlier than historical from a technology perspective.

From a wider perspective about the historical lightweight fighters, then I think it's probably necessary to have around 700-900hp as a minimum. None of the ones with smaller 500hp class engines really worked out.
 
The French Arsenal VG.30 prototype powered by an Hispano-Suiza 12Xcrs would seem to fit in here (ideally fitted with the more rearward radiator bath from the VG.31).
 
I've always liked the Ambrosini 207/403 as some of the most practical lightweight fighters that had decent performance, didn't appear to have major issues, and used non strategic materials. I don't think anything stops these being built earlier than historical from a technology perspective.
Agreed 100%.
Here is the data sheet for the prototype for the 207.

207.jpg

Seems like that it was good for 575 km/h on 750 HP - pretty zippy IMO.
Ironically enough, the same fighter was feasible for the British, just that their engine would've been the 745 HP later RR Kestrel model.

From a wider perspective about the historical lightweight fighters, then I think it's probably necessary to have around 700-900hp as a minimum. None of the ones with smaller 500hp class engines really worked out.

Again agreed. The 500 HP level of power was behind the curve already past 1935-ish.
 
During the period between both World Wars, the size and weight of the fighters was progressively augmented in parallel with the increasing power of the available engines. Against that general trend, there was a minority of aeronautical designers defending the small sized fighters, known as 'Jockey Fighters' at that time. This type of airplanes, if well designed, could generally compete in performance with the conventional fighters, using a less powerful engine, with an important save in fuel, manpower and strategic materials. They were also easier to maintain and store and their reduced size and weight helped to increase agility in combat, making more difficult to be seen by the rear gunners in the bombers, or by the pilots in the escort fighters, and their destruction required a higher consumption of ammunition.

At the beginning of World War II, the conventional fighters used to have 10 to 12 m of wingspan, operational weight of 2,500 to 3,500 kg and a maximum speed of 450 to 500 km/h. The light fighters of the time could be divided in two categories:

‘Jockey Fighters’, with less than 10 m. wingspan, maximum weight of 1,800 to 2,500 kg and the same speed than the conventional fighters.

‘Midget Fighters’, with less than 10 m wingspan, maximum weight of 600 to 1,800 kg and maximum speed of 350 to 400 km/h.
 
Potez 230​

The Potez 230 inherited the most advanced elliptical wing of the time, built with an integral torque box, from its ancestor, Les Mureaux 190 light fighter, developed during the 30s. The philosophy of design of the Potez 230 was based on the specification Chasseur Monoplace C1 (June 3, 1937), calling for one high-performance small airplane that could use some technical elements left aside by first line fighters.

Thus, the surplus of Hispano-Suiza H.S.12 Xcrs engines, H.S.9 cannons and MAC 34A machine guns coming from the obsolete Dewoitine D.510 fighters could go back to combat without overloading the French war production of H.S.12 Y-45, H.S.404 and MAC 34 M39, intended for the Dewoitine D.520. Would the new equipment be available in enough quantity, it would also had been used by the Potez 230 as it was compatible to both of them.

A prototype was built in the Potez C.A.M.S. factory of Sartrouville in 1939. During a series of tests performed in the Villacoublay test centre in March 1940, it reached the speed of 560 km/h being equipped with an H.S.12 Xcrs of just 680 hp (the Dewoitine D.520 reached 525 km/h and the Bf 109 E-1, 575 km/h with much more powerful engines). It was expected that the Potez 230 could fly at 622 km/h after the installation of one of the new H.S.12 Y-45 of 910 hp but it was captured by German forces in June and translated to a technical research centre of the Luftwaffe to study the wing construction system.

Technical data

Engine: one 680 hp Hispano-Suiza H.S.12 Xcrs twelve-cylinder ‘Vee’ liquid-cooled, driving a three-bladed Ratier airscrew with pneumatic variable-pitch. Armament: one 20 mm engine-mounted H.S.9 cannon and four 7.5 mm. MAC 34A machine guns mounted under the wings. Wingspan: 8.74 m, length: 7.57 m, height: 2.18 m, wing area: 10.97 sq.m, maximum weight: 1,800 kg, maximum speed: 560 kph.
 

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Roussel R.30​

The Roussel R.30 was conceived as a private venture ‘Jockey Fighter’ in answer to the Programme technique A.23 (12 January 1937) that required a light fighter able to fly at 520 km/h. Construction of the prototype began at Courbevoie, flying for the first time equipped with a 690 hp Gnôme-Rhône 14 M7 engine in April 1939.

In August 1939 it was transferred to the Centre d’Essais du Matériel Aérien (C.E.M.A.) for official trials, as a result of which it was recommended to install a more powerful engine to better use its excellent flying performances. During the Battle of France, the airplane was armed with two 20 mm Oerlikon FFS cannons mounted in the wings and some tests were performed for the installation of a bomb rack under the fuselage.

In combat, the R.30 could have destroyed any Luftwaffe bomber thanks to its high fire power of 2 Kg/sec, 2.8 times that of the Bf 109 E-1. In ground attack mode it would have had more possibilities to survive the Flak than the unfortunate Breguet 693 of the GBA 54 due to its high speed and small size. The only prototype was destroyed in Bordeaux-Mérignac airbase during a He111 bomb raid.

Technical data

Engine: one 690 hp Gnôme-Rhône 14 M7 of fourteen-cylinder, air-cooled radial driving a Ratier 1527 airscrew with electrically adjusted pitch. Armament: two 20 mm Oerlikon FFS cannons and one 250 kg G.P. bomb. Wingspan: 7.75 m, length: 6.15 m, height: 2.10 m, wing surface: 10 sq.m, maximum weight: 1,766 kg, maximum speed: 520 kph at 6,000 m.
 

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Bloch M.B.700​

The Bloch M.B.700 was also designed as an answer to the Programme technique A.23. This small interceptor differentiated from the Roussel in that it was built from wood. This fact made its mass production easier as it did not require strategic materials that could be used for the Dewoitine D.520 conventional fighter. Outwardly, it looked like an 83% scaled down version of the conventional fighter Bloch M.B.152. The main advantage of the M.B.700 reduced size was that while equipped with an engine with 75% the power of an M.B.152, it flew 80 kph faster, still carrying the same armament, and was a more difficult target in dog-fight.

In 1939 a prototype was built in the Blériot-Aéronautique of Suresnes, flying for the first time by mid-April 1940. During the flight tests made on 13 May, it reached a maximum speed of just 380 kph, instead of the expected 580 km/h. As a consequence, the Mercier engine cowling and clear canopy were modified, and external plates were installed in the main undercarriage.

The airplane was destroyed shortly afterwards by the German troops in Buc airfield. There was a plan for a shipboard variant named M.B. 720 with tail hook and the armament reduced to four MAC 1934 M 39 machine guns.

Technical data

Engine: one 700 hp Gnôme-Rhône 14 M6 fourteen-cylinder, air-cooled radial engine driving a Gnôme Rhône variable-pitch airscrew. Armament: two 20 mm Hispano-Suiza H.S. 404 cannons and two 7.5 mm MAC 1934 M39 belt-feed machine guns mounted in the wings. Wingspan: 8.9 m, length: 7.34 m, height: 3.4 m, wing surface: 12.4 sq.m, maximum weight: 2,000 kg, maximum speed: 550 kph.
 

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Caudron C.R. 714​

On 12 July 1934 the Service Technique de l’Aéronautique laid down the Programme Technique de Chasseur Léger C.1, a specification for a light weight interceptor with a maximum speed of 400 kph and armed with four machine guns. The original specification was amended in August 22 dividing it in two categories: one for aircraft powered by 800-1,000 hp engines, armed with a cannon and two machine guns, and another for 450-500 hp engines and two cannons. On 17 December 1934 the maximum speed rose to 450 kph and on 16 November 1935 to 500 kph. The winner of the first category was the Morane-Saulnier M.S.405, winning the production of the 860 hp Hispano-Suiza H.S.12 Y engines.

In the second category were competing small manufacturers and designers of racer airplanes experienced in obtaining the maximum speed with minimum power, often using self-made engines. The success achieved by the Caudron racers, encourage designer Marcel Riffard to build the C.710 and C.713 prototypes, two wooden, cannon-armed, light fighters capable of flying to 455-470 kph powered by a 450 hp Renault 12 R.01 engine. On December 1937 l’Armée de l’Air dismissed its serial construction in favor of the Arsenal VG 30, much faster and with better climb rate.

On November 1938, to meet the requirements of Plan V, l’Armée de l’Air ordered the production of 200 units of the C.R. 714 model, an aerodynamically improved version, with a 450 hp Renault 12 R.03, twelve-cylinder, air-cooled, inverted-Vee engine and four MAC 1934 M39 machine guns. The order was later reduced to only 20 aircraft when all the spruce stocks were assigned to the massive construction program of the Arsenal VG 33.

On January 1940 the C.R. 714 were handed over to l’Armée de l’Air who used them as advanced trainers at l’École de Chasse et d’Instruction Polonaise. The G.C. I/145 was formed during the Battle of France with M.S. 406 and C.R. 714 fighters piloted by Poles who claimed the destruction of four Bf 109 and four Do 17. The formula was perfectioned with the C.R. 760 and C.R. 770 prototypes, powered by 730-800 hp engines and armed with six MAC, but both were destroyed to prevent their capture by the Germans.
 

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C.A.P.R.A. R.300​

The midget fighters usually are a good defensive solution when a country feels threatened and needs to quickly increase its production of combat airplanes. The C.A.P.R.A. R.R.20 was a small racer airplane designed by Roger Robert in 1938 to compete in the Coupe Deutsch 1939 race. After the declaration of war the project was modified to be used as a fighter-trainer under the name R.30 or as the R.300 Midget Fighter.

Entirely built in metal, the R.30 would be powered by a 360 hp Bèarn 6C-1, six-cylinder in-line air-cooled engine, with which it was expected to reach 539 kph maximum speed and 9,500 m service ceiling. The wings, spanning 7.5 m with sq.m surface, would serve as housing for the hyper- sustentation system, the Messier landing gear and the armament, possibly two MAC 34A machine guns for the R.300 version. Not a single unit was built.
 

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Payen Fighters​

Between 1932 and 1942, Nicolas Payen designed a series of wooden canard-delta airplanes with a radical tandem-wing configuration.

In 1933 he built the Pa 100 Flèche Volante with small wings called machutes and a 67 degree swept delta tailplane, to compete in the 3rd Coupe Deutsch. The machutes had mobile wingtips which acted as ailerons and electrically-operated metallic flaps. The landing gear consisted of one centreline main leg, retracting backwards, and two outrigger auxiliary wheels retracting into the tailplane.

The engine should have been one 180 hp Regnier R6, six-cylinder straight air-cooled, driving a fixed pitch wooden airscrew. But it was not possible to get one in time to participate in the competition and Payen had to adapt his project to the only engine available: one 380 hp Gnôme-Rhône 7Kd Titan Major seven-cylinder radial air-cooled, weighting 270 Kg, totally unsuited for a racing aircraft. It was necessary to install a fixed undercarriage in more advanced position, to compensate the extra weight, and a tail skid. The wingtips ailerons were also changed by others, safer and of conventional type.

The refurbished plane was named Pa 101 Avion-Flèche, had 4.26 m wingspan, 5.75 m length, 2.2 m height, 6.86 sq.m wing surface, 750 kg maximum weight and one estimated maximum speed of 400 kph. It flew for the first time on 17 April 1935, being damaged in an accident just eight days later.

The Pa 101 airframe served as the basis for a new racer project, called Pa 110 CD (Coupe Deutsch). Designed in 1935, it differed from the previous model by its conventional landing gear, retracting backwards into the fuselage sides. It was hoped that it might be able to fly at 490 kph powered by one 200-240 hp Hirth 508D, eight-cylinder inverted-Vee, air-cooled engine, but the project was cancelled due to lack of funding.

When the Spanish Civil War began, the Republican Government had great difficulties in acquiring combat airplanes abroad, due to the international blockade. In the summer of 1936 Nicolas Payen offered the Spanish communists to build the Pa 110 C.1, the military version of the racer, through the Luxembourgian banker Rosenthal.

The power system designed for the fighter was made up of two 220 hp Renault 6Q-01, six-cylinder straight air-cooled engines installed in tandem face-to-face. Both engines were connected to the contra-rotating propellers power shaft by means of a Cotal-Baudot gearbox that allowed to electrically disconnect any of the engines by means of a clutch.

It was going to have an armament of two 7.5 mm Darne machine guns installed under the machutes and one 20 mm H.S. 9 cannon, firing through the propellers hub, but the French Government had banned its export to Spain and had to be replaced by one 23 mm Danish Madsen cannon. The Pa 110 C.1 would have an estimated maximum speed of 460 kph, flying with one engine, and 550 kph with both engines. The estimated range was of 850 km.

The arrival of the Soviet fighters Polikarpov to Spain in October meant the cancellation of the project, which was redesigned as Pa 112 C.1 to adapt it to the Chasseur Monoplace C.1 specification published by the Ministère de l'Air on 3 June 1937.

The Renault 6Q were replaced by two 200-205 hp Salmson 9ND nine-cylinder radial air-cooled (surplus) engines commonly used by the Bloch M.B.81 of the l’Armée de l’Air and by the Besson B. 411 of the l’Aéronavale. Proposed armament was either a 20 mm H.S. 9 or an Oerlikon FFS cannon and two 7.5 mm MAC 34 M39 belt-feed machine guns installed in the interior of the machutes, or two MAC 34A drum-feed installed under the machutes.

A mock-up using the airframe of the Pa 101 was built in 1938. After being examined by technicians of the l’Armée de l’Air, the project was rejected at the beginning of 1939, because of the great complexity of the power system. Payen offered to build the Pa 300 instead, a fighter capable to surpass the 520 kph of the Programme Technique A23 if they provided him with an H.S.12 Y-45 engine. But the military, who had done most of his career flying in biplanes, found the flèche aerodynamic solution to be too radical and preferred to build the Arsenal VG 33.

To fight these prejudices, Payen built the technological demonstrator Pa 22/2 Fléchair, which was captured by the Germans in 1940 while performing aerodynamic tests in the O.N.E.R.A. wind-tunnel of Chalais-Meudon. Under the new administration, the prototype was modified with the installation of a 180 hp Regnier R6B-01 engine and a new open cockpit with the windscreen of one Arsenal VG 33. It made his first flight on 18 October 1941 and was destroyed during an Allied bombing in April 1944.

The Phoney War ended with the invasion of Belgium and the Netherlands and the German attack against France, using 860 fighters Bf 109E, three-hundred-and-fifty Bf 110, 1,120 medium bombers, 342 dive bombers and 591 reconnaissance airplanes.

L'Armée de l'Air had only thirty-seven Bloch M.B.151, ninety-three Bloch M.B.152, ninety-eight Curtiss H.75A, two-hundred-and-seventy-eight Morane-Saulnier M.S.406 and sixty-seven Potez 631 fighters bons de guerre, supported by thirty Gloster Gladiators and forty-eight Hurricanes British fighters. During the Battle of France 1,279 German, 872 French and 944 British airplanes were destroyed by different causes.

One of the main reasons for the success of the Blitzkrieg against the French and British Armies, in May 1940, was the aerial superiority obtained when the Messerschmitt Bf 109 E-3 entered service with the Luftwaffe. It happened at the right time, when the main French fighter Morane-Saulnier M.S.406 was replaced by the second generation fighters Dewoitine D.520 and Arsenal VG 33. During the Phoney War, l’Armée de l’Air tried to fill the gap with the Bloch M.B.152 and Curtiss H.75A fighters, helped by the British Hawker Hurricane Mk.I. But the Messerschmitt would prove superior.

This seems to be the origin of the commonly accepted paradigm about the assumed inferiority of the French technology. It is not common knowledge that France already had operational naval radar in 1934. And that, at the beginning of June 1940, the antiaircraft artillery defending Paris was controlled by the most advanced radar in the world, able to operate in wavelengths from 80 to 16 cm against the 3.5 to 1.5 m of the British or the 2.4 m to 53 cm of the German radar.

The French scientists were also ahead of their German equivalents in the field of nuclear fission. By early 1940, the CNRS controlled the highest reserve in the world of uranium (8 tons coming from the Belgian Congo) and 200 kg of heavy water from the Norwegian enterprise Norsk Hydro.

The French tanks of 1940 had better armour and armament than the Germans. The Marine Française (the French combat fleet) was superior to the Kriegsmarine in firepower with the Béarn carrier and six squadrons of Loire Nieuport L.N.401/411 dive bombers that technically surpassed the German Ju 87.

The destructiveness of the air-to-air weapons installed in the French fighters was slightly higher that their German equivalents, although the quality of the aiming devices OPL 31, RX 39 and GH 38 used by l’Armée de l’Air was somehow inferior to the Zeiss Revi C/12 reflector gunsight of the Luftwaffe. The following text compares the armament used by the French and German fighters during the Battle of France
 

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Seems like that it was good for 575 km/h on 750 HP - pretty zippy IMO.
Ironically enough, the same fighter was feasible for the British, just that their engine would've been the 745 HP later RR Kestrel model.
I think that having an air cooled inline that works might also be another part of this in order to minimise mass - every extra kg (e.g. radiator) means extra wing area and drag etc. Using one of the smaller liquid cooled inlines might not be quite as small, but provides greater choice e.g. Kestrel, Peregrine, Asso XI
 
I think that having an air cooled inline that works might also be another part of this in order to minimise mass - every extra kg (e.g. radiator) means extra wing area and drag etc. Using one of the smaller liquid cooled inlines might not be quite as small, but provides greater choice e.g. Kestrel, Peregrine, Asso XI

Seems like only the Isotta-Fraschini was making the enough powerful air-cooled inlines.

British have it the best - their Kestrel is a very good engine year by year, and indeed it can be replaced by Peregrine by 1940. My preference is that the British fighter is designed either by De Havilland or by Percival - both people were known for the sleek aircraft of the better part of the 1930s, so even if the engine is not the best, the resulting fighter will perform well. Percival had no mass production abilities, so someone else will need to make the fighters.
The fighter should be in the ballpark with the SAI.207 performance-wise already by 1937.

For the Germans - a spin-off from the He 100 design (sans the fancy cooing), powered by the Jumo 210 for the starters. Kill the He 112 development and meager production so this can start rolling.
 
Hi Tomo,

Engines available should be no more powerful than (power at rated altitude, talk about 12000-15000 ft back then):
- for 1937-39: radials of under 850 HP, other under 750 HP
- for 1940-42: radials of under 1000 HP, other under 900 HP
- for 1943-45: radials of under 1300 HP, other under 1200 HP

Well, that means your 1940 - 42 fighter is more or less equivalent to a Me 109 C-3 (that's the Jumo 210 variant with 2 MG FF wing guns).

The problem with using unproven fighters like the Ambrosini as a benchmark is that it's doubtful that they would still be as light or as low-drag by the time they're fully equipped and robust enough for operational service.

Now obviously, one might reduce the drag of the Me 109 C a bit, but in my opinion, even the step up to the Me 109 F airframe wasn't really transformative - low single digit percentage drag reduction, I'd say.

And you haven't stated what you're trying to achieve with the small fighter - if one needs to produce a higher-quality product than fighters were historically to achieve acceptable performance (competitive with the standard-quality fighter with a standard engine), then you might end up with a just-as-expensive, but less capable small fighter.

To provide an example in which an air force actually considered down-scaling a fighter by reducing the armament from 2 cannon plus 2 rifle-calibre machine guns to just 2 rifle calibre machine guns only: Jiro Horikoshi states that during the design of the A6M, the question came up whether the smaller fighter was a better solution, considering that the Japanese Navy's requirements were near-impossible to fulfill. The conclusion was, giving up armament wasn't worth it, even though it would have been quite beneficial for the design's weight budget.

The "small fighter" sounds a bit like a piston Volksjäger project to me! ;-)

Regards,

Henning (HoHun)
 
Well, that means your 1940 - 42 fighter is more or less equivalent to a Me 109 C-3 (that's the Jumo 210 variant with 2 MG FF wing guns).


Now obviously, one might reduce the drag of the Me 109 C a bit, but in my opinion, even the step up to the Me 109 F airframe wasn't really transformative - low single digit percentage drag reduction, I'd say.

No, I'd avoid the Bf 109A-D base, since He 100 will offer a much less draggier solution.
The 109F base is great, OTOH.

The problem with using unproven fighters like the Ambrosini as a benchmark is that it's doubtful that they would still be as light or as low-drag by the time they're fully equipped and robust enough for operational service.

Robustness rarely adds drag, and it seldom increses the size - one of the apparent advantages of the Ambrosinis was their small size. 'Fully equipped' Ambrosini still has just two HMGs for 1937-40, that on itself is a pretty low-drag stuff, while still on par with what the Italian fighters carried in the day.

And you haven't stated what you're trying to achieve with the small fighter - if one needs to produce a higher-quality product than fighters were historically to achieve acceptable performance (competitive with the standard-quality fighter with a standard engine), then you might end up with a just-as-expensive, but less capable small fighter.

Big airforces, like the RAF, AdA, RA or LW were burning the midnight oil to bulk up their strength to the untold hundreds of fighters in the second half of 1930s. Much better to do it with an Ambrosini-like fighter than with Gladiator, MS 406, a biplane or the He 112, while the only realistically available imported fighters - these from the USA - were either sub-par, or very expensive, or unavailable (or a combination of the above).

Small airforces, dozens of them, will have a hard time to get the latest and bestest fighters from the big players, while the small fighters should've been easier to get exported, and the licence for the domestic production granted. Most of the smaller countries that still had an airforce were without the domestic aircraft-making industry anyway.

Using a second tier engine and the smaller and lighter airframe will drive the cost down, not up.

To provide an example in which an air force actually considered down-scaling a fighter by reducing the armament from 2 cannon plus 2 rifle-calibre machine guns to just 2 rifle calibre machine guns only: Jiro Horikoshi states that during the design of the A6M, the question came up whether the smaller fighter was a better solution, considering that the Japanese Navy's requirements were near-impossible to fulfill. The conclusion was, giving up armament wasn't worth it, even though it would have been quite beneficial for the design's weight budget.

Hirokoshi was fully capable of installing two cannons on a small fighter. But, naval fighters came with their own sets of issues, and this is for the land-based machines.
BTW - the Ki-27 with a retractable U/C, another pair of LMGs and a Sakae 11 would've looked par.
 
Hi Tomo,

Robustness rarely adds drag, and it seldom increses the size - one of the apparent advantages of the Ambrosinis was their small size. 'Fully equipped' Ambrosini still has just two HMGs for 1937-40, that on itself is a pretty low-drag stuff, while still on par with what the Italian fighters carried in the day.

Well, here's the Me 109 C-3 weight sheet:

c3-15.jpg

Even cannon-armed, it's lighter than the Ambrosini, at 2168 kg vs. 2275 kg, despite having a 16.4 m^2 wing to the Ambrosini's 13.9 m^2 wing.

However, my point was not that you should choose the Me 109 C-3 as your 1940 - 42 fighter - my point is that you're going to end up with Me 109 C-3 style capabilities for your 1940 - 42 fighter.

Making an aircraft like the Me 109 C-3, but 100 km/h faster on the same engine ... well, climb rate and power loading will be hardly affected by that, even if you manage to pull it off, and the resultant aircraft will still be slow by 1941 standards.

And I'm just using the mid-war period to illustrate how much performance one sacrifices by using small engines, the same considerations apply to the other periods as well.

Regards,

Henning (HoHun)
 
Even cannon-armed, it's lighter than the Ambrosini, at 2168 kg vs. 2275 kg, despite having a 16.4 m^2 wing to the Ambrosini's 13.9 m^2 wing.
Thank you for the data.

However, my point was not that you should choose the Me 109 C-3 as your 1940 - 42 fighter - my point is that you're going to end up with Me 109 C-3 style capabilities for your 1940 - 42 fighter.
Making an aircraft like the Me 109 C-3, but 100 km/h faster on the same engine ... well, climb rate and power loading will be hardly affected by that, even if you manage to pull it off, and the resultant aircraft will still be slow by 1941 standards.

Please see above - for 1940-42, the V12 engine can be up to 900 HP (and radial up to 1000 HP) at the rated altitude.

And I'm just using the mid-war period to illustrate how much performance one sacrifices by using small engines, the same considerations apply to the other periods as well.

Using the small-ish engine does not make the task easy.
However, a topic that says 'make the fighter around the best current engine' would've not be so interesting ;)
 
French have had a number of interesting fighter projects in the works, unfortunately these were either too late, or were not proceeded with. Ironically, only the lest powerful of them, the C.714, was manufactured in some extent.
On the other end of the scale was probably the VG.33, that was supposed to do 550-560 km/h with 860 HP at the meager rated altitude.

Potez 230 was very diminutive, with the wing of just under 11 sqm and the take off weight of 1800 kg. Powered by the 690 HP engine, it was supposed to do 560 km/h.

The D.550, if made earlier and powered by the small engine like the HS 12X was, might've morphed into a fighter. It was also very small and light in the historical racing trim, and with the bigger 12Y engine.

The D.551 was another too late to matter, yet an interesting fighter. Size-wise it was between the D.520 (itself not being a big fighter) and the D.550, or very similar to the VG.33. Under the rules for this thread, for 1940-42 it would've been interesting even with the yesterday's 12Ys. Obviously, France will need to survive for this to materialize :)
 
Hi Tomo,

Please see above - for 1940-42, the V12 engine can be up to 900 HP (and radial up to 1000 HP) at the rated altitude.

That's still worse than the Emil's DB 601 A-1 at climb power.

I'd say most types were at about 2 kg/HP in 1942, so with a 900 HP engine, you'd have a weight budget of just 1800 kg.

(I would guess the radial engine's extra drag is greater than 100 HP at top speed, and it is probably harder to achieve a competitive top speed than to achieve a competitive power loading, though the radial engine might be lighter, so the increased weight budget of 2000 kg for the thus-engined fighter would be easier to meet, but you'd end up with an even slower fighter.)

Still, the question is, what do you leave out to meet that budget? Crew, fuel, guns and weapons are about 500 kg you can't do without. The Me 109 C-3 has 173 kg "additional equipment", probably stuff like gunsight, oxygen equipment, radio etc., and that doesn't even include armour yet which you can't do without in 1940 either.

So there's 1505 kg empty weight. About 500 kg of this would be a 900 HP engine, so say you've got a 1000 kg airframe, of which you'd have to eliminate at least 350 kg to make the weight target.

Constraint diagrams are a useful concept to size an aircraft for the requirements:

View: https://www.youtube.com/watch?v=hOeojIca-zg&t=509s


However, that obviously needs well-defined requirements ;-)

Regards,

Henning (HoHun)
 
That's still worse than the Emil's DB 601 A-1 at climb power.
Not everyone can get an Emil. Same if someone want's to buy just the DB 601. Heck, even the Germans were unable to get the DB 601s for all their needs and wishes.
See the Italians - Reggianne reverted to the radial engines past the 2001 and before the 2005. The Fiat G.50V remained just as a prototype. Finnish AF - they fought the best part of continuation war with MS 406s, Hurricanes and Fokkers. Similar situation to the Hungarians and Romanians.
All of these countries were supposed to be fighting against the same/similar enemy that LW had to deal with, but trying to do that with fighters that were obsolete in one or another way will be an uphill battle.

(I would guess the radial engine's extra drag is greater than 100 HP at top speed, and it is probably harder to achieve a competitive top speed than to achieve a competitive power loading, though the radial engine might be lighter, so the increased weight budget of 2000 kg for the thus-engined fighter would be easier to meet, but you'd end up with an even slower fighter.)

See, I've told you that this is not an easy task :)
Making a well-streamlined radial engine installation would've helped a lot. Talk what Nakajima did with the Ki-27, and not what the Italians were doing with the MC.200 and G.50?
The target to meet will be probably the FFVS J.22 and the Ki-44, as far as the small streamlined radial-engined fighters go?

Still, the question is, what do you leave out to meet that budget? Crew, fuel, guns and weapons are about 500 kg you can't do without. The Me 109 C-3 has 173 kg "additional equipment", probably stuff like gunsight, oxygen equipment, radio etc., and that doesn't even include armour yet which you can't do without in 1940 either.

For 1940, Germans can install the Avia-made HS 12Y engines. Widens the elbow room a lot wrt. the installed equipment.
See here the He 100 with the front end of the Avia monoplane fighters (obviously, the surface cooling from the He 100 is long gone):

100class.jpg

(see here the same A/C done in plastic)
 
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Hi Tomo,

Not everyone can get an Emil.

It's more like Cäsar with a very slightly upgraded engine, and it's just the benchmark for what you're probably going to end up with. The RAF's Cäsar might be a Martin-Baker MB2, but the performance isn't going to be much different.

All of these countries were supposed to be fighting against the same/similar enemy that LW had to deal with, but trying to do that with fighters that were obsolete in one or another way will be an uphill battle.

Well, it's a bit like you're designing a fighter to be obsolete upon introduction.

See here the He 100 with the front end of the Avia monoplane fighters (obviously, the surface cooling from the He 100 is long gone):

Maybe the surface cooling should stay, you'll need every advantage you can get. Being faster might reduce your exposure to enemy fire for a better end result than being a bit more resilient to enemy fire, but getting hit more. It's worth noting that the condensation coolers are not under pressure like steam engine boilers, so coolant will be lost at a relatively slow rate only. A small short-range fighter will probably fighting over or near friendly territory anyway, so it should normally be able to land with a few hits before the engine overheats. It might not survive a long hunt, but as it will be fighting superior enemy types, it would most likely not survive a long hunt anyway as the enemy fighter would simply keep inflicting hits even to a small fighter with a conventional radiator.

Regards,

Henning (HoHun)
 
It's more like Cäsar with a very slightly upgraded engine, and it's just the benchmark for what you're probably going to end up with. The RAF's Cäsar might be a Martin-Baker MB2, but the performance isn't going to be much different.
Seems like we disagree.

Well, it's a bit like you're designing a fighter to be obsolete upon introduction.
A lot of people were doing a much better job historically, both wrt. designing and introducing the fighters that were obsolete upon introduction.
I've at least suggested going with the fighters of modern shape (cantilever monoplanes with retractable U/C, closed canopy), that was not achieved with many fighters designed in the second half of the 1930s.
 
Hi Tomo,

Seems like we disagree.

You haven't yet stated which kind of performance you'd expect, so I'll have to take your word for it :)

I've at least suggested going with the fighters of modern shape (cantilever monoplanes with retractable U/C, closed canopy), that was not achieved with many fighters designed in the second half of the 1930s.

Well, I-16 vs. Me 109 at the Eastern Front might be a good approximation for a small fighter vs. full-size fighter match, even if the Rata might still have had an open canopy (though it had originally been designed with a closed one).

Approximate specifications of the 1939 I-16 Type 24: 900 to 1100 HP, 1900 kg, 15 m^2 wing, 462 km/h @ 4700 m

Regards,

Henning (HoHun)
 
SAI 207
 

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Post-2
 

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SAI 403
 

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You haven't yet stated which kind of performance you'd expect

750 HP with a V12 and a small-stature fighter should make an easy push well beyond 500 km/h ( still a more conservative turn of speed than for the SAI 207). With a 900 HP V12, between 550 and 600 km/h.

Approximate specifications of the 1939 I-16 Type 24: 900 to 1100 HP, 1900 kg, 15 m^2 wing, 462 km/h @ 4700 m
I-16 have had a few strikes against him. The chosen engine is a barn-door 9 cyl type, indeed the cockpit canopy is not what it should've been, and, for 1941, it is still 100 HP short with 900 HP available instead of 1000 allowed. The Ki-27 was a tad faster, despite having a fixed U/C and an engine that was making 12-15% less HP.

See the J.22 as a small fighter done good - a 14 cyl engine will produce less drag, engine power is better, and so is the cockpit. It was supposed to be faster than that I-16 by 100 km/h.
Or the 1st Zeroes; granted, these were neither small not very light when compared with the really light fighters, but were still usefully fast even with 950 HP - talk more than 50 km/h faster than that I-16.
 
SAI 107
 

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VEF Irbitis I-16
 

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Romanian Jockey fighters
 

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Weiss Manfred WM 23
 

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Lazarov Light Fighters
 

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By the time of the Munich Crisis, it was unclear to the British authorities if the production of the new monoplane Hawker Hurricane and Supermarine Spitfire fighters could be accelerated sufficiently to equip the 123 Squadrons that the Fighter Command required for the defence of the British Islands.

In October 1938, F.G. Miles, designer of the Miles Master advanced trainer, proposed the construction of a single-seat fighter that could supplement the Hurricanes and Spitfires already in production, without competing with them for the Merlin engines or in the use of strategic materials. The project, called Miles M.20/1 'Munich Fighter', could be built entirely of wood/plywood using the retractable landing gear and several parts of the Miles Master trainer.

It would be propelled by one 885 hp liquid-cooled V-12 Rolls-Royce Peregrine engine, driving a two-bladed airscrew and would be armed with two 20 mm Hispano-Suiza H.S. 404 cannons. A wooden mock-up was built at the end of 1938, but no orders were placed because production of the Peregrine was reserved for the Westland Whirlwind twin engine fighter.

Miles persisted with the M.20/2 project, adapted to the Specification F.19/40, calling for a fighter armed with eight 0.303 in Browning Mk.II machine guns and propelled by one 1,300 hp Rolls-Royce Merlin XX 'power egg' interchangeable with the Bristol Beaufighter and the Avro Lancaster airplanes. The M.20/2 had a fixed landing gear, thus removing the need of hydraulic circuits and enabling the construction in fourth the time than a Hurricane and tenth time than a Spitfire. During the flying tests carried out on 14 September 1940, the prototype AX 834 showed a top speed exceeding that of the Hurricane Mk.I and manoeuvrability equivalent to that of the Spitfire Mk.I. The stabilization of the German offensive and the increase in production of the conventional fighters rendered it mass production worthless and the project was left aside in April 1941.

The projected fighter Percival P.33 AB, based on the aerodynamic configuration of the Mew Gull racer that competed for the Merlin XX engine, was also cancelled. It would have been a 556 kph fighter armed with four Brownings, with 12.24 m wingspan, 9.2 m overall length and 2,848 kg maximum weight.

During the critical days of 1940 the 'Panic Effect' boosted numerous interim solutions to increase the number of fighters available: A.A. Bage, the Percival chief designer, proposed to build a version of the Mew Gull armed with two 0.303 in Vickers Mk.II machine guns. The projected light fighter, called Percival P.32 AA, would have 7.62 m wingspan, 6.57 m overall length and 1,087 kg maximum weight. But it was rejected in favour of the Miles M.24, the single-seat version of the Miles Master, armed with eight Brownings, capable of flying at 370 kph and with handling characteristics similar to those of the Hurricane.
 

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- The Sokół emergency fighter programme



After the Third Reich annexation of Sudetenland, the Polish Air Force was pressing for 170 per cent reserves of fighters, facilitating the reactivation of the Sokół project, which had been dismissed a year earlier in favour of the P.Z.L. P.50.



At the beginning of 1939 the Polish Department of Aeronautics issued the Sokół specification, calling for a light-weight single seat fighter powered by one 660-730 hp Gnôme-Rhône 14M-05 Mars double-row radial engine, armed with four 7.7mm KM Wz36 SG machine guns and equipped with a Walter Iskra R/T device and full oxygen installation.



The P.Z.L. firm proposed two Sokół versions, with all-metal construction, semi-monocoque fuselage structure and P.Z.L. two-blade, adjustable pitch airscrew: the P.45/I with fixed undercarriage and the P.45/II with retractable undercarriage. Both versions used structural solutions based on the P.Z.L.19 Challenge tourer wings, spanning 12.14 m, with 10.3 aspect ratio and 14.3 sq.m surface. Each wing panel housed one 175 litres fuel tank and one flap. A third flap was located in the belly fuselage. The estimated maximum speed of the P.45/II was 520 kph and the gross weight 1,940 kg. The construction of the P.45/I had still not concluded in September 1939.



The design proposed by the firm R.W.D. was very similar to the Fokker D.XXI and used the same construction system, with all-wood wings, spanning 10.5 m without flaps to simplify production. The fuselage, with welded Chrome-Molybdenum tubular structure, had a coating of light metal sheets in the front section and fabric in the rest.

The Letov three-blade fixed-pitch airscrew foreseen for the original design, should be replaced by another model after the invasion of Czechoslovakia. This version of the Sokół, called R.W.D. 25, would have an estimated maximum speed of 450 kph and a gross weight of 1,800 kg. The construction of the prototype, started in July 1939, could not be completed.



The Design Number 42, proposed by the firm P.W.S. early in 1939, would be totally built of wood/plywood, with inwards retractable landing gear, 9 m wingspan and 16 sq.m wing area.

It should be armed with two machine guns in the wings and two more in the nose. Its estimated maximum speed would be 520 kph and its gross weight of 1,900 kg.



P.Z.L. P.50 Jastrzab



Designed at the end of 1936 as a successor to the P.Z.L. P.11, the P.50 was a small monoplane with an elliptical wing and appearance like that of the American Seversky P-35.



The original specification required a highly manoeuvrable interceptor for the close defence of specific targets, propelled by an 840 hp Bristol Mercury VIII air-cooled radial engine and armed with four 7.7 mm machine guns: two WZ.36 G in the nose and two WZ.36 SG in the external wing panels.



The manufacture of 300 aircraft, under the denomination P.50A Jastrzab I, started in 1938. Delivery of the first 50 machines was expected by September 1939. The Aviation Command planned an expansion programme that was to end in 1941, with 15 squadrons equipped with P.50 A to and a reserve of 150 aircraft. The manufacture under licence of the Mercury VIII began in the P.Z.L-W.P.I aero-engine plant at Warsaw-Okeçie.



The prototype P.50/I was completed in September 1938. It was a fully metallic plane, with 2,500 kg gross weight, equipped with one Hamilton/P.Z.L. three-blade variable-pitch airscrew. The wings, spanning 9.7 m, housed the Dowty retractable undercarriage, flaps and Handley-Page automatic slots.



During its first flight in February 1939, it showed instability at low-speed and tail flutter in dive. The prototype was under-powered, with low rate of climb and the top speed was only 430 kph. The test pilots reported that their flight characteristics were inferior to those of the Seversky EP-1.



In August the P.50/I managed to fly at 500 kph thanks to the amendments to the carburettor air intake, tail unit and wing/fuselage fillets. In April the General Zając cancelled the production programme and ordered using the Mercury VIII available in the P.Z.L. P.11g Kobuz emergency fighters.



The basic Jastrzab airframe was adapted for many more powerful engines, like the indigenous 1,200 hp P.Z.L. Waran, lengthening the fuselage up to 8.2 m. Attempts were made to obtain either 1,050 hp Pratt & Whitney Twin Wasp, 1,400 hp Gnôme-Rhône 14N 50, 1,145 hp Bristol Taurus III and 1,375 hp Bristol Hercules radial engines.



The new aircraft, called P.50B, would have been a strike-fighter armed with two 20 mm Wz.38D cannons in the wing roots and two 7.7 mm Wz.36 G machine guns in the nose and would be able to carry one 300 kg bomb or one detachable fuel tank under the fuselage.

The airframe was completed in the spring of 1939, but the Gnôme-Rhône 14N 21 engine acquired in France was not available on time.



The construction of other more advanced versions in 1940-41 had been foreseen:



P.Z.L. P.53A Jastrzab II with Waran or Bristol Hercules engines and P.Z.L./Hamilton-Standard propeller.

P.Z.L. P.53B, with Gnôme-Rhône 14N 51.

P.Z.L. P.56A Kania, with Hispano-Suiza H.S.12Y-31 or Allison V-1710-23 in-line engines.

P.Z.L. P.56B with one 1,600 hp Hispano-Suiza H.S.12Z.



P.Z.L. P.55

In October 1938 the design team of the firm Dewoitine, under the leadership of Robert Castello, began working on a version of the D.520 fighter, capable of flying at 700 kph.



The wind tunnel tests carried out in March 1939 in Toulouse-Banlève with a 1/8 model, proved that at least 650 kph could be reached, using a 900 hp Hispano-Suiza H.S.12Y crs engine driving one Ratier airscrew of 3m diameter, and exceed 700 kph with the new 1,200-1,400 hp H.S.12Z.



The performances of the new French ‘V’ engines attracted the attention of the Polish Department of Aeronautics that started contacts with the French Government to acquire a license for manufacture of the H.S.12Y-51 and H.S.12Z for the future Kania fighters. The designer Jerzy Dąbrowski was also interested, to propel his P.Z.L. P.55, a new fighter based on the Challenge tourer P.Z.L. P.26, with 11.25 m wingspan and 3,250 kg gross weight, sometimes described in the literature as P.62 or Dąbrowski Fighter.



In early summer 1939 the wind tunnel test showed the aerodynamic superiority of the P.55 (660 kph) against the Kania and the Aviation Command favoured its production. It would have been built entirely of metal, with laminar-flow wings provided with Handley-Page slots, flaps and outboard retractable landing gear. One semi-retractable radiator was designed, inspired by the Prestone cooling system used by French Morane-Saulnier 406 fighters.



The planned armament consisted of a 20 mm H.S.404 cannon or an indigenous Wz.38C, firing through the propeller hub, and six 7.92 mm Wz.36 SG machine guns mounted in the wings. The pilot would be protected by an armoured windshield and steel plates, the cockpit was heated and equipped with oxygen and Walter Iskra R/T device.



As an alternative to the French engine, the Polish Government tried to acquire the manufacturing licence for the American Allison V-1710-23. A future P.55 equipped with Allison could not use the cannon and should be reinforced with two Wz.36G (synchronized) machine guns in the nose. The prototype was expected to fly for the first time in the summer of 1940.



Bibliography
Books

Glass, A., Polskie Konstrukcje Lotnicze 1893-1939, WKZ, Warszawa 1976.

Cynk, J., Polish Aircraft 1893-1939, Putnam 1971.

Koniarek, J., Polish Air Force 1939-1945, Squadron/Signal Publications 1994.

Liss,W., The P.Z.L. P.11, Profile Publications Nº75.

Green, W., Warplanes of the Second World War, Fighters, Volume Three, MacDonald 1961.

Sołtyk, T., Polska Mysl Technierna w Lotnicze, WKŁ, Warszawa 1983.

Duleba, L., Samoloty RWD, WKŁ, Warszawa 1980.

Krzyzan, M., Miedzynarodowe Turniieje Lotnicze, WKŁ, Warszawa 1988.

Cynk, J., Siły Lotnicze Polski i Niemiec, WKŁ, Warszawa 1989.

Morgała, A., Samoloty Wojskowe, Polsce 1924-1939, Bellona, Warszawa 2003.

Malak, E., Prototypy Samolotow Bojowych, Polska 1936-1939, WUW, Wrocław, 1990.



Publications

Davis C., “P.Z.L. P.50 Jastrzab“, Aero Plans, August 1988.

Cynk, B., “P.Z.L. P.50 Jastrzab“, Air Pictorial, December 1962.

Dobrzelecki, M., “First Kills Over Poland”, SAFO, vol.15 nº3, July 1991.

Dobrzelecki, M., “The Polish Air Force in September 1939”, SAFO, vol.13 nº4, October 1989.

Kowalski, T., “4 Pulk Lotniczy”, SAFO, vol.3 nº1, March 1978.

Musialkowski, P., “The Pulawski Fighters”, SAFO, July 1989.

Dildy, D., “Jadenastka”, SAFO, vol.15 nº1, June 1991.

Cynk, J., “Blitzkrieg”, Airpower, June 1983.

Cynk, J., “Les intercepteurs P.Z.L. P.7 et P.11”, Le Fana de l’Aviation, nº 72 to 77.
 

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Hi Tomo,

See the J.22 as a small fighter done good - a 14 cyl engine will produce less drag, engine power is better, and so is the cockpit. It was supposed to be faster than that I-16 by 100 km/h.

I've just had a look at the Swedish Wikipedia, which has some quite detailed data, and it shows a "Stridshastighet" of just 420 km/h @ sea level and 510 km/h at 4000 m. I believe that translates to "combat speed", and thus is probably achieved at 900 HP @ 2550 rpm, for which the table gives a (static full throttle) altitude of 3658 m (12000 ft).


Weight and wing area are basically the same as the Emil's, performance and armament are worse.

Fine as a fighter trainer, but does it make sense to take a low-performance "small fighter" like that (not that it's really any smaller than a Me 109) up against an Fw 190A, a Spitfire IX, or a P-38E in 1942?

Regards,

Henning (HoHun)
 

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