Advanced French Fighters vs 1942/1943 contemporaries

[Shortround6]

Any reference on primary sources would be appreciated - for both statements ("some pilots preferred" and "12.7 penetrated better").
After reading many memoirs and interviews of Soviet fighter pilots, I got the impression that they were quite satisfied with the ShVAK, and only very rarely was there an opinion that it would be better to put another UB instead of the ShVAK, but the reason was not the worse penetration, but the ammunition. At the same time, many pilots stated that they rarely used the entire ammunition of the ShVAK in aerial combat.

There was a variety of ammunition for both guns, with different target effects. A pilot's impression could depend on the ammo his guns were loaded with.

But if we are comparing AP to AP for the two rounds the 20mm is going to come off worse. The 20mm is trying to blow a hole just under 2 1/2 times the size (area) and it has just under 2 times the energy of 12.7mm to do it. That is at the muzzle. The 20mm projectile in the ShVAK cannon is not the best. It is a little light for the bore size (sectional density) and doesn't have a very good shape, Most 20mm projectiles (anybody's) are not well shaped compared to the US and Soviet 12.7mm projectiles.

HE projectiles (anybody's) usually don't penetrate well, unless the fuse fails.
12.7mm US and Soviet projectiles were very seldom HE or even holding much incendiary material. Usually about 2 grams of material in the nose ahead of the AP core, useful for indicating impact.

I have no primary sources.
It does seem that some of figures used in old western books for velocities for the Soviet guns were a little off, or modern sources are down playing them for some reason.

It is a little hard to get around physics. Soviet 20mm ammo used projectiles of around 93-99 grams? Hispano's used about 127-130 grams ( there may be a bit more variation?) but at the same speeds the AP round (full bore, not using sub caliber tungsten penetrators) is going to penetrate about 25-30% more than the ShVAK round. There was/is no magic. People had been figuring out how to get through iron/steel plates since about 1860. By 1940 they had a pretty good idea of what worked in full bore ammunition for steel types and heat treatments. Doesn't mean some countries used the best option/s at times (British 2pdr).

There are accounts of British pilots not being happy with the early 20mm Hispano cannon due to lack of "penetration". In this case it was that the fuses detonated too early, on the skin of the aircraft and did not get inside where the crew/important stuff was. British had few/no 12.7mm guns and resorted to using inert/training rounds mixed into the belts/drums until the fuses were fixed/replaced. A 128 gram lump of steel could 'penetrate' quite a bit of aircraft structure if it didn't hit good armor or something like an engine.

 

[Shortround6]

I'm not entirely sure about the amount of filler the HE (HEF-T?) had, I was able to find some documents around the internet but my Swedish isn't good enough to make sense of them. The most I could glean was a cartridge weight of 42 grams and 1~2 grams of explosive filler seems like a reasonable estimate for that.

Some of the 'smaller' 12.7/13mm projectiles would hold 1-2 grams of explosive filler. If somebody had designed an HE bullet I would expect a bit more. Unfortunately for the Italians and Japanese they tended to put tracer elements on/in the back of the HE projectiles which took up space/volume and cut into the HE/incendiary payload.

Regardless, it is still a very powerful gun and the HE would likely help at tearing through wings or tails with a well-aimed burst.

It may not do what you think. There was an American pilot who's plane took several 20mm hits. One hit his port aileron and detonated in the aileron, damage was not as impressive as many would think. Not sure if it did much to aileron support spar. They recovered the back part of the shell from inside the aileron and the pilot had it bored out and ring made out of it, which tell use that it was NOT a mine shell and most likely a HET round that had around 5 grams of HE. Enough to burst the front of the shell but the rear ring of shell was pretty much intact. Perhaps the explosive was defective?

Personally, I'd go with 2 x 13.2 mm per wing for any fighter with less than 3 cannons.

Problem here is weight. Even the Belgian gun was as heavy as three 7.5mm machine guns. And the big MG ammo was about 5 times heavier, 200 rounds of 12.7/13.2 mm is as heavy as 1000 rounds of 7.5mm.
There is no sense to making a one 20mm and four 13.2mm fighter, you might as well just use the three 20mm guns.

Weight might be an issue, but if they could lighten the Hispanos (which seems highly likely due to the very light weight of the 405 - weight saving methods could likely be transferred over to the 404 or a hypothetical 406) it probably wouldn't be too heavy.

I have told you before how they lightened the 405 gun. They cut the hell out of the gun to take a much shorter shell.
British cut 8kg out of the 404 to make the MK V version. That included cutting 30cm off the barrel. You can cut all kinds of stuff if you are using a shorter, lower powered round.
Kind of like how you can lighted a rifle when you go from a 7.62X51 NATO to a 7.62X39 Soviet round.
Not sure if they even built the 405 gun.
And again, the only way to get light weight guns is to accept semi-disposable ones. Change the barrels and a few other parts and if they make it to 2,000-3,000 rounds fired then trash the gun and replace it. It won't be worth rebuilding.

 

[bf109xxl]

I am not understanding your first quote, C3 was a high octane fuel.

You are absolutely right - it is high-octane gasoline, but only when large amounts of TEL (5.5 ml/l) were added. "Real" high-octane gasoline had a higher ON of the hydrocarbon base, and the addition of TEL was just about 0.8-1 ml/l.

On par with US 100/130 grade, some test even state close to US 100/150 grade. Am I misunderstanding you?

C3 was comparable or even superior to US 100 octane gasoline only on rich mixtures.

I know of at least 3 Soviet oil fields that were used: Baku, Grozny and Ufimskoye.

What you labeled as "Ufimskoye" is actually called "Volga-Ural petroleum province", a huge area with many oil fields.

These are openly listed in aircraft engine manuals so they were used for aviation gasoline production.

Bashkir oil was much worse than Baku oil - it was much more complicated to produce aviation gasoline from it, about 80% of Soviet aviation gasoline was produced from Baku oil. I can cite sources, but they are in Russian, unlikely to be interesting to you. Even gasoline produced in Grozny was considered much worse than the one from Baku.

There is excellent information on the Luftwaffe's oil situation found in BaMA RL 2-VI 115 pages 2-3. If you wish to read on this subject in English, Calum Douglas wrote on this as well in his book The Secret Horsepower Race.

The German source does not clearly answer the question:

Der Flugkraftstoffbestand betrug bei Kriegsbeginn, also im September 1939, etwa
400.000 to.
Er erhöhte sich bis Ende 1940 durch Beute, hauptsächlich aus französischen Beständen, auf rund
600,000 to.
Diese Menge setzte sich zusammen aus:
Reinbenzin, also nichtethylisiertem Grundbenzin
A 3, Oktanzahl 80
B 4, Oktanzahl 87-89
C 3, Oktanzahl 100
Der für die Luftwaffe am meisten infrage kommende Flugkraftstoff war das B 4.

Thus, no specific information about what kind of gasoline was captured and what exactly it was used for was given. And further:

Mit Kriegsausbruch fielen die ausländischen Flugkraftstofflieferungen, bis auf die rumänischen Lieferungen, fort. Da Rumänien monatlich nur rund 6000–9000 to Flugkraftstoff lieferte, war die deutsche Luftwaffe grundsätzlich nur auf die heimische Erzeugung angewiesen.

There is even less information on this topic in the book by C. Douglas. However, I may have missed or forgotten something important, I would be grateful if you could remind me of the page number.
An unambiguous answer was found here:

The aviation fuel was particularly valuable to the Germans at this time. According to Ahrens this comprised 160,000 tons captured in France and 80,000 tons captured in Holland. All the operations of the Luftwaffe against Great Britain in the summer and winter of 1940 were made on this fuel. (A.D.I.(X) 399/1945.)

It was a bit odd to me because the results of the fuel analysis from the damaged German planes that landed in Britain didn't mention either French or Dutch gasoline, IIRC, and the physical and chemical properties of French gasoline were quite different as compared to the German one at close ON. Unfortunately memory sometimes fails, I'll have to go through the tables again - I'd be grateful if someone could tell me if there is any indication of French/Dutch origin of gasoline in the reports, so I don't waste my time if none is found.

Anyway, thanks for the references!

 

[Shortround6]

Bashkir oil was much worse than Baku oil - it was much more complicated to produce aviation gasoline from it, about 80% of Soviet aviation gasoline was produced from Baku oil. I

You may be well aware of it but the US oil varied considerably from east to west. East coast (Pennsylvania) was good for about 38-40 octane gas using WW I methods of refining.
West Coast oil could make about 70 octane gas with the WW I Methods, Texas/Oklahoma was somewhere in between, like 50-60?
Better refining methods changed things but it was always going to be easier/cheaper to use west coast or imported oil than east coast oil.

As you know there is a limit as to how much TEL can be used without increasing problems.


I have wondered if the German reluctance to use rich mixtures was due to trying to economize on fuel or if the injector systems wouldn't meter enough fuel or if the rich mixture didn't work as well with the fuel injection? The Fuel doesn't have much time to cool the mixture/absorb heat coming out of the direct injection nozzles? Or several reason put together?

 

[TM06]

Some of the 'smaller' 12.7/13mm projectiles would hold 1-2 grams of explosive filler. If somebody had designed an HE bullet I would expect a bit more.

How much more are we talking here? 5 grams? 10 grams? Half the bullet weight in filler?

There is no sense to making a one 20mm and four 13.2mm fighter, you might as well just use the three 20mm guns.

Perhaps there's a shortage in cannon production? Maybe the extra endurance of the 13.2's are more appealing? A five gun setup like that isn't entirely out of the picture, again look at some Italian designs. That's also the layout the SAAB 21 used as well, so it's at the very least worth considering.

I have told you before how they lightened the 405 gun. They cut the hell out of the gun to take a much shorter shell.
British cut 8kg out of the 404 to make the MK V version. That included cutting 30cm off the barrel. You can cut all kinds of stuff if you are using a shorter, lower powered round.
Kind of like how you can lighted a rifle when you go from a 7.62X51 NATO to a 7.62X39 Soviet round.
Not sure if they even built the 405 gun.
And again, the only way to get light weight guns is to accept semi-disposable ones. Change the barrels and a few other parts and if they make it to 2,000-3,000 rounds fired then trash the gun and replace it. It won't be worth rebuilding.

The example I used of the 405 is more about the potential to lighten the basic Hispano instead of the 405 itself. Although I do think the 405 could be a reasonable offensive gun, a lighter 404 or some derivative is more probable and would likely show up earlier than the British Mk V.

 

[bf109xxl]

Better refining methods changed things

I have already mentioned the technological backwardness of the Soviet oil refining industry. New refineries equipped with American machinery under the Lend-Lease program only started to be built in 1943 and began production after the war. The USSR attempted to create a "Second Baku" in the Volga-Ural region, but this resulted in a largely inefficient use of funds and lower production volumes. Bashkir oil contains a lot of sulfur and paraffins and requires more complex refining methods involving additional steps. The USSR did not have its own version of a catalytic cracking process similar to the Houdry process.

As you know there is a limit as to how much TEL can be used without increasing problems.

Soviet engines that ran on gasoline with a high TEL content regularly had problems with spark plug reliability.

I have wondered if the German reluctance to use rich mixtures was due to trying to economize on fuel or if the injector systems wouldn't meter enough fuel or if the rich mixture didn't work as well with the fuel injection? The Fuel doesn't have much time to cool the mixture/absorb heat coming out of the direct injection nozzles? Or several reason put together?

The Germans wanted to use rich mixtures, they knew about their advantages. The problem was the dilution of oil with gasoline - the fuel didn't evaporate fast enough. They tried to fix that - the C3 in 1940 and in 1943 were different. A detailed consideration of the problems with the German fuel can be found in the book "The Secret Horsepower Race: Western Fighter Engine Development" by C. Douglas:

The C3 fuel of 1943 would evaporate more completely at a lower temperature than the C3 used in 1940, specifically to cure the oil dilution which had ruined the effectiveness of the DB 601 N engine in 1940 and 1941. Only the German engineers knew this however, and so the British were left to guess:

 

[Shortround6]

How much more are we talking here? 5 grams? 10 grams? Half the bullet weight in filler?

Unless you do something really, really tricky with shell design and fabrication, like the German Mine shell, high velocity HE shells carried about 10% explosives to weight. Give or take a few percent.
Depends on the velocity range of the projectile and strength/quality of the steel. Lower velocity shells can use thinner walls with more volume for payload. Higher quality steel can allow for thinner walls.
However you can't quite scale a 20mm design down to 13mm exactly. The wall thickness has to stand up to the firing stresses or the shell may buckle while firing. There is also the problem of keeping the shell together in flight due to centrifugal force. A gun with a velocity of 800m/s and a 1 in 400mm twist is going to spin the bullet at 2000rps. Not 2000rpm but 2000rps which is 120,000rpm. You want the shells to reach the target and not disintegrate after leaving the muzzle. The wall thickness in greater in proportion than the 20mm or larger shell. Note that an 700m/s gun has less of a problem? There is also a problem with the fuses. The 13mm fuse can be a little smaller but not scaled exactly in proportion.
The US M23 incendiary bullet (no fuse) .50 cal bullet that was used for troop trials at the end of the war contained 5.8 grams of incendiary in a 32.4 gram bullet instead of the 43-46 gram projectiles. HE and Incendiary material are a lot less dense than steel or copper and light weight bullets are going to have rather different flight characteristics than the other projectiles (different aiming point). Basically you are going to max out at around 3 grams of filler for 13mm projectile.

A five gun setup like that isn't entirely out of the picture, again look at some Italian designs. That's also the layout the SAAB 21 used as well, so it's at the very least worth considering.

I would leave the SAAB 21 out of this. 239sq ft wing, empty weight 3250kg and loaded weight of 4150kg (clean?) and using a DB 605 engine that weighed 725kg (?).
Rather larger and heavier than the French fighters?
And look at the Italian fighters a little more closely. The 12.7mm guns are heavy but the ammo is about 70% as heavy as the French 13.2 mm per round.
The German cannon is lighter than it appears in most lists. It is ready to go at 42 kg, a 42kg Hispano V still needs a 6-8kg belt feeder or a heavy drum if you don't use the belt feed.
Italians were still doing pretty good.

The example I used of the 405 is more about the potential to lighten the basic Hispano instead of the 405 itself. Although I do think the 405 could be a reasonable offensive gun, a lighter 404 or some derivative is more probable and would likely show up earlier than the British Mk V.

Pointing out that while a lighter 404 was certainly possible, it could not be done without sacrificing something. Cutting 40cm off the barrel may not have affected velocity by much and may have helped speed up the rate of fire. Making some of the other moving parts lighter also speeded up the rate of fire. But it also made them less durable/reliable and it might have been a very good trade-off.

 

[bf109xxl]

But if we are comparing AP to AP for the two rounds the 20mm is going to come off worse. The 20mm is trying to blow a hole just under 2 1/2 times the size (area) and it has just under 2 times the energy of 12.7mm to do it. That is at the muzzle. The 20mm projectile in the ShVAK cannon is not the best. It is a little light for the bore size (sectional density) and doesn't have a very good shape, Most 20mm projectiles (anybody's) are not well shaped compared to the US and Soviet 12.7mm projectiles.

I discovered the book "Soviet Air Armament. Aircraft against tank." (2017) by Oleg Rastrenin, which for unknown reasons I have not familiarized with until now. There you can find a comparison of the BS (UBS) with the ShVAK. You are right - indeed in 1936 the 12.7-mm AP bullet of the BS had a higher armor penetration than the AP shell of the ShVAK (16 and 11 mm of homogeneous armor respectively). But already in 1940, new HE-Frag. and AP projectiles with a better performance (20 mm of homogeneous armor) were developed for the ShVAK, and in 1941 were put into mass production. The problem of the ShVAK was the non-optimal aerodynamic shape of the projectile and its irrational design. The projectile was too weak against armored targets and heavy bombers, but quite effective against most German combat aircraft.

PS. The book is interesting because it gives an insight into the situation with aircraft armament in the USSR before the war, as well as the negative role of B. Shpitalny (the chief-designer of ShVAK), who can be rightfully called an "evil genius" in the field of aircraft armament.

 

[TM06]

I would leave the SAAB 21 out of this. 239sq ft wing, empty weight 3250kg and loaded weight of 4150kg (clean?) and using a DB 605 engine that weighed 725kg (?).
Rather larger and heavier than the French fighters?

Fair enough, but there's two more roughly comparable designs that used the FN Browning; the FFVS J 22 and the Renard R.38. Both of these are light aircraft (2,800 kg take off for the J 22, 2,600 kg take off for the R.38) that are quite small and used four 13.2 mm FN Brownings in the wings. The J 22 had 250 rpg for a 1,000 round total, and although I can't seem to find exact numbers for the R.38's ammunition capacity anywhere it's, likely quite similar to the J 22.
The earlier - and lighter - Renard R.37 had 2 x 13.2 mm machine guns and 2 x 20 mm Hispano 404's in one of its possible armament layouts as well.
Their wingspans are comparable to the French fighters at 10 m (16m2​) and 11 m (20 m2​) respectively, and their weights are comparable to the French fighters.

 

[Shortround6]

Fair enough, but there's two more roughly comparable designs that used the FN Browning; the FFVS J 22 and the Renard R.38. Both of these are light aircraft (2,800 kg take off for the J 22, 2,600 kg take off for the R.38) that are quite small and used four 13.2 mm FN Brownings in the wings. The J 22 had 250 rpg for a 1,000 round total, and although I can't seem to find exact numbers for the R.38's ammunition capacity anywhere it's, likely quite similar to the J 22.

I wonder what they did not have. Wiki (for want of better source) says 2760kg for the J 22A (two 13.2mm and two 8mm) and 2835kg for the J 22B with four 13.2mm guns. Could have had different radios or ? but swapping the 8mm guns for the 13.2 and the ammo sounds close. 28kg for the gun change and around 35kg for the 13.2mm ammo covers most of the change in weight. Heavier mounts/brackets ?

The Renard series may have been good planes but they were prototypes. The heavier armaments were mostly on paper. Performance numbers are with the lighter armaments.

The earlier - and lighter - Renard R.37 had 2 x 13.2 mm machine guns and 2 x 20 mm Hispano 404's in one of its possible armament layouts as well.

As above, any performance numbers for the R.37 are with four 7.7mm machine guns. Quite possible the guns would fit in the wings. But sticking the armament of a late Spitfire XVIe in a plane powered by a GR-14N is not going to end well. Credit for ambition.

Their wingspans are comparable to the French fighters at 10 m (16m2) and 11 m (20 m2) respectively, and their weights are comparable to the French fighters.

Yes and no. The problem is not the span, it is the area. 20m2 is 25% Bigger than 16m2.

Now lets go back to the J 22 fighter. It was a remarkable achievement given what the Swedes had to work with. It was also late, Production starting in the summer/fall of 1943 or at least that is when service planes showed up. Swedes also made choices some other air forces may not have made. Again from Wiki so could be way off.
Never exceed speed 400mph/650kph ? bad translation?
Japanese A6M5 had a limit of 360kts...(414mph?) and the A6M5a with thicker wing skins had a dive speed limit of 400kts/ 460mph.
J 22 had a 6G load limit/10Gs ultimate.
Stall speed was 137kph/85mph in landing configuration. This was much more common in 1943-44 that in 1940-41.
Due to the P&W engine the climb was not that great. Not bad but not great, in fact it wasn't much different than a P-40B.

And the P-40B is great example of the weight of a fighter out running the power of the engine. P-40B could climb to just under 15,000ft in 5 minutes. Unfortunately that was running about 500lbs under normal gross weight. The P-40B had gained about 531lbs over the P-40 due to increased armament, 93lbs of armor, BP glass and rudimentary fuel tank protection.
Some of this was self inflicted as some people thought that increasing the ammo for the cowl .50 cal guns from 200rpg to 380rpg was a good idea. This was responsible for about 108-110lbs of weight increase alone. US cowl mount .50 cal guns were lucky to hit 500rpm when synchronized so they already had 24 seconds of firing time, at best rate of fire. Some guns barely beat 400rpm in British tests.
And then the P-40 began it's decent into madness. The P-40D with slightly improved engine was designed to hold 2460 rounds of .50 cal ammo (738lbs...335kg) of just ammo.
Granted they could put in a lot less but..........................The wing had to stressed/built to handle that load and the wing alone increased just about 100lbs over the weight of the wing in the P-40B/C. Don't know what else they beefed up to handle weight.

I don't know what the French or Belgians were planning of doing to fit in increased armament loads. But making major changes to the guns and ammo was going to need some work. The Cauldron C 760 was planned to have some rather strange amounts of ammunition.

started with 300rpg. Then 400rpg, then 500rpg and then 1000rpg. Some accounts claim 3 times that but somebody hasn't done the math. 3000rpg times 6 needs a sizable truck to deliver the ammo for one fighter. about 500kg not including the crates.
Maybe they should have worried about the pilot being able to past the nose instead of the ammo capacity?
A problem, although to lesser extent, with several of the French prototypes and the Renard series fighters. It can be solved, much like it was solved on the F4U Corsair, but it does cost a few KPH in speed.
I do give credit to the Renard engineers.

I don't know how well it worked but it is one of the better attempts to use exhaust thrust from a radial engine of the time and it may have been being used to draw cooling air through the cowl?
I have my doubts as to the small air inlet but they were working on it.

 

[TM06]

I wonder what they did not have. Wiki (for want of better source) says 2760kg for the J 22A (two 13.2mm and two 8mm) and 2835kg for the J 22B with four 13.2mm guns. Could have had different radios or ? but swapping the 8mm guns for the 13.2 and the ammo sounds close. 28kg for the gun change and around 35kg for the 13.2mm ammo covers most of the change in weight. Heavier mounts/brackets ?

As far as I know, nothing changed between the two models aside from the armament layout. The only variant that had significant differences was the S 22-1 (or S 22-3 depending on the source), which were reconnaissance aircraft that got changed back into fighters. So any excess weight outside of the guns and ammo would have to relate to the gun mounts.

Now lets go back to the J 22 fighter. It was a remarkable achievement given what the Swedes had to work with. It was also late, Production starting in the summer/fall of 1943 or at least that is when service planes showed up. Swedes also made choices some other air forces may not have made. Again from Wiki so could be way off.
Never exceed speed 400mph/650kph ? bad translation?
Japanese A6M5 had a limit of 360kts...(414mph?) and the A6M5a with thicker wing skins had a dive speed limit of 400kts/ 460mph.
J 22 had a 6G load limit/10Gs ultimate.
Stall speed was 137kph/85mph in landing configuration. This was much more common in 1943-44 that in 1940-41.
Due to the P&W engine the climb was not that great. Not bad but not great, in fact it wasn't much different than a P-40B.

The J 22 was an excellent plane...for when it was designed.
Comparing it to other 1940 fighters (Bf 109 E-3, Spitfire Mk IIa, F4F-3), it's a bit faster than the Bf 109 and Spitfire below 4,500 m but drops off above 5,000 m and becomes the slowest between the three above 6,000 m. However it completely beats the F4F-3 at all altitudes - something that's quite notable due to them being powered by the same engine. Climb rate is also interesting, it's equal to the Spitfire all the way up to 9,000 m while being well above the F4F-3 and Bf 109 E-3. But by the time it reached large scale production in 1943, it was hopelessly outclassed by its competition.
An old War Thunder suggestion put the Vne at 670 kph / 416 mph, but unfortunately the post has been lost to time and can't be accessed.
This website is very good for information about the J 22 including some very interesting pilot interviews, I'd recommend giving it a read.

 

[Shortround6]

As far as I know, nothing changed between the two models aside from the armament layout. The only variant that had significant differences was the S 22-1 (or S 22-3 depending on the source), which were reconnaissance aircraft that got changed back into fighters. So any excess weight outside of the guns and ammo would have to relate to the gun mounts.

The J 22 was an excellent plane...for when it was designed.
Comparing it to other 1940 fighters (Bf 109 E-3, Spitfire Mk IIa, F4F-3), it's a bit faster than the Bf 109 and Spitfire below 4,500 m but drops off above 5,000 m and becomes the slowest between the three above 6,000 m. However it completely beats the F4F-3 at all altitudes - something that's quite notable due to them being powered by the same engine. Climb rate is also interesting, it's equal to the Spitfire all the way up to 9,000 m while being well above the F4F-3 and Bf 109 E-3. But by the time it reached large scale production in 1943, it was hopelessly outclassed by its competition.
An old War Thunder suggestion put the Vne at 670 kph / 416 mph, but unfortunately the post has been lost to time and can't be accessed.
This website is very good for information about the J 22 including some very interesting pilot interviews, I'd recommend giving it a read.

Thank you, I had seen that website a number of years back, before we have to the wayback machine to access it.

Unfortunately the author doesn't understand how supercharged aircraft engines work and as a result his graphs are largely in error.

I will also note that the F4F-3 does NOT use the same engine, it uses an engine that used a two stage supercharger with 3 possible "speeds". Neutral, where the aux supercharger is not being spun by the engine and the level of boost is coming from the engine supercharger alone, low gear where the aux supercharger is clutched in and the aux supercharger is feeding the engine supercharger after the air goes through an intercooler and then high gear where the aux supercharger impeller is spun faster.

The only gain in performance from using 100 octane fuel was going to be at low altitudes. Much like the Merlin III did not make any additional power at altitudes over 16,250-17,000ft.
100 octane and 12lbs of boost offered 1310hp at 9,000ft, but the supercharger was maxed out at 9,000ft at 12lbs off boost and could not supply any more air and power fell to the standard 1030hp at 16,250ft regardless of fuel.
Same for the supercharger on the R-1830. The engine in the J 22 was a single speed supercharger that maxed out at 1200hp at 4900ft (yes, 4900ft) at 2700rpm when using 100 octane fuel. With 87 octane it was rated at 1050hp at 7700ft at 2700rpm. Any improvement in performance would be below 7700ft. Now if you over-revved the engine to 2800rpm you could get 1000hp at 11500ft but something wasn't working right. The engine was rated at 900hp at 12,000ft at 2550rpm max continuous.
It is also interesting to note that the R-1830 (100/130 octane) used in the Australian Beauforts used a two speed single stage supercharger. The same 7.15 gear for low gear that the engine in the J 22 used. 1200hp for take-off, 1200hp at 4900ft. However in high gear, 8.47 to 1. power was 1050hp at 2700rpm at 13,100ft.
Over-revving the engine increased the supercharger impeller speed from 19,305 to 20,020 while changing gears at 2700rpm increased the impeller speed 22,869.
It would not have mattered if you stuck 100/150 fuel in the J 22, performance much above 4900ft was not going to change because the supercharger could not supply more air than it was already doing with the lower grade fuel.

 

[Luft.4]

You are absolutely right - it is high-octane gasoline, but only when large amounts of TEL (5.5 ml/l) were added. "Real" high-octane gasoline had a higher ON of the hydrocarbon base, and the addition of TEL was just about 0.8-1 ml/l.

Not sure what you mean by "real" high octane? Base stock is always lower than the final ON number, for aviation fuel this usually starts in the low 70s. No matter which nationality you look at. The Allies 100/130 grade used 4 cc/IG of TEL, bumping this to 4.6 cc/IG in April 1944. 100/150 grade used 6 cc/IG. Their fuels were heavily doped with pure iso-octane, xylidine and aniline.
Any engine running on fuel with a high TEL content will suffer spark-plug issues, that is exactly why Allied 100/150 grade was recalled in the final months of the war. The Luftwaffe did not have that luxury in the final years, they ran their engines into the ground because they were desperate. Creative mixing/blending is what harmed B4 in late 1944/1945.

Thus, no specific information about what kind of gasoline was captured and what exactly it was used for was given.

I would appreciate if you provide a reference on the role of the captured fuel stocks for the aviation gasoline production in Germany. The topic is of great interest to me.

Apart from providing 2 sources which do answer the exact question you asked (what was the role/significance, not what kinds of ON aviation fuel did they capture), a third may be found in AIR48/86, p.26. The Luftwaffe could blend fuels, as they regularly did BTW, to get the final mix they needed. It is beyond a doubt that captured Allied aviation fuel stocks gave a lifeline to the Luftwaffe in the war's 1st half.
It is actually shocking how brazen they were in their conquest of Europe knowing how weak their fuel situation was for a continental-conflict. This gave way to a vicious cycle of using up vast reserves of fuel to attempt the capture/hold of fuel producing regions which repeatedly failed.

Ufimskoye oil field was taken directly out of a Soviet engine manual, I would trust they knew were it came from.

Just a friendly discussion,
Dan.

 

[TM06]

Getting back to the French, 1 x 20 mm + 4 x 13.2 mm for the Dewoitines and Arsenals is a layout that although inferior to 3 x 20 mm in terms of one-second-burst-mass has the advantage of endurance. A fighter with 120 cannon rounds and ~1,000 heavy-hitting HMG rounds can stay in a fight for longer than a fighter with 360 cannon rounds. 12 Seconds + 15 seconds of continuous firing (assuming an RPM of 1,000 for the 13.2's) versus just 12 seconds of continuous firing. The comparison is even more favourable for the 13.2's if you crank down their RPM to a more normal 800, which gives them a continuous firing time of 19 seconds.
Now if they could manage to fit 200 or so rounds into each Hispano belt then that's different, as you're going from 12 seconds of continous firing to 20 seconds of continuous firing (assuming an RPM of 600). But finding the space for that on the small French fighters might've been a challenge.

Regardless, are we all in agreement that the FN Browning would've been the best HMG choice for Vichy France in this scenario? Compared to the other options, it seems like the most realistic and reasonable option from my point of view.

 

[Shortround6]

Regardless, are we all in agreement that the FN Browning would've been the best HMG choice for Vichy France in this scenario? Compared to the other options, it seems like the most realistic and reasonable option from my point of view.

It would have been the best choice for the HMG.

But finding the space for that on the small French fighters might've been a challenge.

And this is part of the problem for the French fighters. For weight a single 20mm and four 13.2mm guns is about the same as six 12.7mm/.50 cal guns. And the US screwed up the P-40D/E and Wildcat with that weight armament. They also put in more protection than some other nations did. US self sealing tanks were among the best but they were heavy. P-40 and Wildcat also didn't have their engines improve as much as needed in 1942/43 to stay first rank.

French fighter design in late 1939 and 1940 was going the wrong way. They were going for small/light and quite possibly cheap while operational requirements were calling for increased weight (better protection and more firepower). Many nations were forced to accept longer take-off runs and higher landing speeds with heavier improvements to existing aircraft or new designs. New versions of old designs didn't handle quite as well as the originals. This is regardless of engine power (mostly).

French fighter fields in 1939/40 were terrible, hopefully they would have gotten better had France be able to stay in the war. I have no information on the French fighters but the Hawk 75s were having a very bad time even in the phony war. There are claims that one reason the Spitfires weren't sent to France was that the RAF looked and the fields figured they would loose to many planes taxing and landing.
French were trying to back armor in a number of their planes before they fell but bringing French fighters up to 1941/42 standards was going to hurt performance.
Now in late 1940 and into 1941 the French can fit the HS engines in the high 40s, they can fit the last of the G-R 14Ns to make up some of that but with their small wings they are in the same boat the Germans were in with the 109. The wing loading keeps going up.
There were some easy fixes to get a bit better performance out of the existing engines. Put two speed superchargers on the engines comes to mind like the Russians did. Buy some time while they sort out the GR 14R and the HS 12Y-51 and the HS 12Z what-evers.

The French fighters also have to fit into the French Air Force and not be viewed as stand alones. Soviets got away with low altitude fighters because the Germans let them. The battle in East turned into a tactical battle with the vast majority of strike missions on both sides being army support. The German bombers couldn't reach many of the Soviet factories and Soviets didn't have the command structure (and radar) to do a British defense system. Soviets didn't have enough bombers to attack the German rear areas except often enough to keep the from redeploying there AA guns. The higher altitude combat of even the BoB pretty much disappeared.
IN a France vs Germany battle going longer in 1940 and into 1941-42 (and later) there was going to be a lot more rear area bombing going on on both sides. It was part of their doctrine, with missions of 200-300 miles it was quite doable. But it means combat between the bombers and their escorts vs the interceptors in the high teens and low 20s with the fighters, like the BoB, heading for 30,000ft. Fighters with 150 sq ft wings are going to be found wanting. Maybe you don't need 230-260 sq ft wings but the French design trend needs to be reversed.

 

[TM06]

And this is part of the problem for the French fighters. For weight a single 20mm and four 13.2mm guns is about the same as six 12.7mm/.50 cal guns. And the US screwed up the P-40D/E and Wildcat with that weight armament. They also put in more protection than some other nations did. US self sealing tanks were among the best but they were heavy. P-40 and Wildcat also didn't have their engines improve as much as needed in 1942/43 to stay first rank.

French fighter design in late 1939 and 1940 was going the wrong way. They were going for small/light and quite possibly cheap while operational requirements were calling for increased weight (better protection and more firepower). Many nations were forced to accept longer take-off runs and higher landing speeds with heavier improvements to existing aircraft or new designs. New versions of old designs didn't handle quite as well as the originals. This is regardless of engine power (mostly).

French fighter fields in 1939/40 were terrible, hopefully they would have gotten better had France be able to stay in the war. I have no information on the French fighters but the Hawk 75s were having a very bad time even in the phony war. There are claims that one reason the Spitfires weren't sent to France was that the RAF looked and the fields figured they would loose to many planes taxing and landing.
French were trying to back armor in a number of their planes before they fell but bringing French fighters up to 1941/42 standards was going to hurt performance.
Now in late 1940 and into 1941 the French can fit the HS engines in the high 40s, they can fit the last of the G-R 14Ns to make up some of that but with their small wings they are in the same boat the Germans were in with the 109. The wing loading keeps going up.
There were some easy fixes to get a bit better performance out of the existing engines. Put two speed superchargers on the engines comes to mind like the Russians did. Buy some time while they sort out the GR 14R and the HS 12Y-51 and the HS 12Z what-evers.

The French fighters also have to fit into the French Air Force and not be viewed as stand alones. Soviets got away with low altitude fighters because the Germans let them. The battle in East turned into a tactical battle with the vast majority of strike missions on both sides being army support. The German bombers couldn't reach many of the Soviet factories and Soviets didn't have the command structure (and radar) to do a British defense system. Soviets didn't have enough bombers to attack the German rear areas except often enough to keep the from redeploying there AA guns. The higher altitude combat of even the BoB pretty much disappeared.
IN a France vs Germany battle going longer in 1940 and into 1941-42 (and later) there was going to be a lot more rear area bombing going on on both sides. It was part of their doctrine, with missions of 200-300 miles it was quite doable. But it means combat between the bombers and their escorts vs the interceptors in the high teens and low 20s with the fighters, like the BoB, heading for 30,000ft. Fighters with 150 sq ft wings are going to be found wanting. Maybe you don't need 230-260 sq ft wings but the French design trend needs to be reversed.

Looking at the SE.520Z, M.520T and M.B.157 shows promise, the designers did seem to be keen on fixing the problems caused by their small size and weights.
SE.520Z went up to 3,150 kg with a 16 m^2 wing, M.520T went up to 3,185 kg~3,337 kg with a 17.3 m^2 wing, M.B.157C1 went up to 3,250 kg with a 19.3 m^2 wing. The VG.39 is also noteworthy due to its 3,000 kg take-off weight but it was a bit behind on the wing design trend with only a 14 m^2 wing. The aircraft themselves are still small and light compared to their contemporaries but they're no longer in the light fighter headache zone.
And while the customer desires you mentioned prior are definitely a factor, the French Air Force seemed to be very loose with weight and wingspan, generally leaving it up to the companies as long as it met the performance + armament requirements - something that can be easily seen due to the varying sizes and weights of the aircraft made for the various C1 tenders.
The small light fighters were just a stop-gap solution, and both France and the designers seemed to recognize that.

 

[bf109xxl]

Not sure what you mean by "real" high octane? Base stock is always lower than the final ON number, for aviation fuel this usually starts in the low 70s.

If you need 1 ml/L TEL it means, you base has ON >=90. that is what i assume as "real high octane".

No matter which nationality you look at. The Allies 100/130 grade used 4 cc/IG of TEL, bumping this to 4.6 cc/IG in April 1944. 100/150 grade used 6 cc/IG. Their fuels were heavily doped with pure iso-octane, xylidine and aniline.

6 cc/IG ~ 1.32 ml/L << 5.5 ml/L

Any engine running on fuel with a high TEL content will suffer spark-plug issues, that is exactly why Allied 100/150 grade was recalled in the final months of the war.

5.5. >> 1.32. Different scale of the problem.

Apart from providing 2 sources which do answer the exact question you asked (what was the role/significance, not what kinds of ON aviation fuel did they capture),

The information on significance has no value if the use is not exactly specified. "Significant for Germany" may mean "used as truck fuel". Still I would appreciate an exact page number in the book by C.Douglas.

a third may be found in AIR48/86, p.26. The Luftwaffe could blend fuels, as they regularly did BTW, to get the final mix they needed. It is beyond a doubt that captured Allied aviation fuel stocks gave a lifeline to the Luftwaffe in the war's 1st half.

Thanks! I'll try to take a look.

It is actually shocking how brazen they were in their conquest of Europe knowing how weak their fuel situation was for a continental-conflict. This gave way to a vicious cycle of using up vast reserves of fuel to attempt the capture/hold of fuel producing regions which repeatedly failed.

The main problem with German aviation fuel supply at that time was TEL, not the hydrocarbon base. I agree with the rest. Unfortunately, a similar situation happens again nowadays.

Ufimskoye oil field was taken directly out of a Soviet engine manual, I would trust they knew were it came from.

The first and the most important oil field in Bashkiria during the war was Ishimbai (since 1932). Engine manual should not provide an exact information on oil field. "Ufimskoye" simply means "oil from Bashkiria".

Just a friendly discussion

The same from my side.

 

[Bretoal2]

The VG.39 is also noteworthy due to its 3,000 kg take-off weight but it was a bit behind on the wing design trend with only a 14 m^2 wing.

Yes, but the VG 30 series were initially planned with HS 12-X engine (690 hp) - just as the Potez 230.

A little known fact is that D520 variants were studied with GR-14M engines, and Renault 12R 00. Small fighters, you said ?

 

[Shortround6]

Looking at the SE.520Z, M.520T and M.B.157 shows promise, the designers did seem to be keen on fixing the problems caused by their small size and weights.
SE.520Z went up to 3,150 kg with a 16 m^2 wing, M.520T went up to 3,185 kg~3,337 kg with a 17.3 m^2 wing, M.B.157C1 went up to 3,250 kg with a 19.3 m^2 wing. The VG.39 is also noteworthy due to its 3,000 kg take-off weight but it was a bit behind on the wing design trend with only a 14 m^2 wing. The aircraft themselves are still small and light compared to their contemporaries but they're no longer in the light fighter headache zone.
And while the customer desires you mentioned prior are definitely a factor, the French Air Force seemed to be very loose with weight and wingspan, generally leaving it up to the companies as long as it met the performance + armament requirements - something that can be easily seen due to the varying sizes and weights of the aircraft made for the various C1 tenders.
The small light fighters were just a stop-gap solution, and both France and the designers seemed to recognize that.

The whole VG.30 series seems to have stayed with the 14m2 wing?
Disregarding the Caudron series we do have Dewoitine going to a small wing (13m2 ?) with the 551.

Air Forces generally did not specify either wing span or wing area, leaving designers to get on with it.
What Air forces did sometimes specify was wing loading or landing speed or field length (take-off/landing distance).
Once a plane was in production or even in widespread tooling up, weight gains sometimes blew right through some of those requirements. Germans accepted the 109E at hundreds of kg higher than the 109B-D. And stayed with that size wing, in part because of the number of factories tooled up to the make the 109.
The US P-39 is a classic case of outright lying, desperation and massive weight gain. Much is made of the lack of the turbo, a lot less is mentioned of the 3/4 of ton weight gain to turn the thing into a combat worthy fighter WHILE cutting the internal fuel capacity by about 200 liters. Needs must when the devil drives.
BTW According to some sources Bell had received a 2 million dollar check for "P-400s" from France in early April of 1940. This order was transferred to the British with the fall of France. The French, British and Americans were getting sucked into ordering planes of dubious utility when they arrived in combat trim.

Problem for the French is that some of the 1940-41 improvements to many fighters had to be applied regardless of the size of the plane. You can't use a smaller pilot armor back plate on a smaller wing fighter. The Pilots stay the same size. Same for BP glass. Same for radios. Even fuel protection is similar (mostly, P-39s and a few others had problems), if you are trying to protect 400 liters of fuel, give or take, you need a certain amount of protective material. Long/flat tanks require more than short, fat tanks. Same amount of protection becomes a higher burden on the small wing fighters than on larger wing fighters percentage wise.

3150kg for a SE.520Z is very close to the weight of a 109G-6. The 109G-6 was effective but it had issues. And the Germans were trapped by the wing size and the tooling of the factories.

MB-157 needs a further look, as built did it have the improvements most countries wanted in a 1941-43 aircraft?
How much of the performance was estimates?
The flight from Merignac to Orly in early 1943 needs closer examination. It is about 500km between the two places. At the sometimes given cruising speed of 400kph that should have taken about 1 1/4 hours. The claim is that the flight was made in 40 minutes less time than scheduled, which means either the scheduled flight speed was very, very slow or the MB-157 was averaging nearly 800kph.

 

[Bretoal2]

The flight from Merignac to Orly in early 1943 needs closer examination. It is about 500km between the two places. At the sometimes given cruising speed of 400kph that should have taken about 1 1/4 hours. The claim is that the flight was made in 40 minutes less time than scheduled, which means either the scheduled flight speed was very, very slow or the MB-157 was averaging nearly 800kph

This claim is a legend that was never confirmed. The Bloch 157 performances as published were engineers estimates, not real tests.

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Les derniers chasseurs Bloch, 157, 1010, 1011, 1040: entre mythe et mystères | SAM40

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