Advanced French Fighters vs 1942/1943 contemporaries

[Shortround6]

I'm not entirely sure how the power-weight ratio works for aircraft, but would it be fine to use lower powered engines if they're significantly lighter? Certain Japanese fighters were made with this in mind, the Ki-44 in particular was an excellent aircraft utilizing the same design principal. If so, then they likely wouldn't need to push past around 1,750 on the 14R while maintaining its light weight.

Not sure how we transitioned from power to weight of the engines to power to weight of the aircraft. Not the same thing.

High powered aircraft engines were pushing the technology boundaries of engine design and materials in the late 30s and during the 40s. There were times when aircraft engines running on gasoline beat the power to weight numbers of Formula 1 engines running on exotic fuel blends (large amounts of Methanol) and did it at 3-5000 meters, not sea level AND displayed much better reliability.

Unfortunately for the French their engines needed total redesigns even after the war and some of their numbers don't seem to line up well with their contemporaries.

Very few (if any) air cooled engines were pushed to higher power levels while maintaining light weight. Engine in the Ki-44 gained 90 kg between the Ki-44-1 and Ki-44 II.
Used cylinders the same diameter as the G-R 14s but shortened the stroke from 165mm to 160mm. Displacement dropped from 38.7 liters to 37.5 liters.

 

[TM06]

Not sure how we transitioned from power to weight of the engines to power to weight of the aircraft. Not the same thing.

High powered aircraft engines were pushing the technology boundaries of engine design and materials in the late 30s and during the 40s. There were times when aircraft engines running on gasoline beat the power to weight numbers of Formula 1 engines running on exotic fuel blends (large amounts of Methanol) and did it at 3-5000 meters, not sea level AND displayed much better reliability.

Unfortunately for the French their engines needed total redesigns even after the war and some of their numbers don't seem to line up well with their contemporaries.

Very few (if any) air cooled engines were pushed to higher power levels while maintaining light weight. Engine in the Ki-44 gained 90 kg between the Ki-44-1 and Ki-44 II.
Used cylinders the same diameter as the G-R 14s but shortened the stroke from 165mm to 160mm. Displacement dropped from 38.7 liters to 37.5 liters.

The weight question was moreso about if the engines would really need to develop as much power as their contemporaries as long as both the engine and the aircraft themselves are light within reason (AKA not one of those light fighters). Something more or less like the Yak-3 as an example, since that was quite rapid despite its low power.
Would the 12Z and the 14R need to push past the 1,300~1,400 hp and 1,600~1,700 hp marks respectively given the light weight of both the engines themselves and the aircraft they were intended for? Cutting down on the required power might also allow them to focus on reliability.

 

[Shortround6]

The weight question was moreso about if the engines would really need to develop as much power as their contemporaries as long as both the engine and the aircraft themselves are light within reason (AKA not one of those light fighters). Something more or less like the Yak-3 as an example, since that was quite rapid despite its low power.
Would the 12Z and the 14R need to push past the 1,300~1,400 hp and 1,600~1,700 hp marks respectively given the light weight of both the engines themselves and the aircraft they were intended for? Cutting down on the required power might also allow them to focus on reliability.

A lot depends on what you want the planes to actually do.

The Japanese and Russian aircraft were not as well protected as British/German/US fighters. Not all self-sealing tanks offered equal protection and be careful of the phrase "protected tanks" as that was 'achieved' in several ways. Sometimes it was duralumin sheeting (light-thin armor), heavy rubber bags, sheet metal tanks that purged every so often with exhaust gas to reduce fire risk (did nothing for leaks).
The Yak-3 it trotted out in the light weight fighter crowd all the time. How long did it take to show UP? What could it do when it got there (it was fast). What couldn't it do? It did well against the 109s/190s over the eastern front in the 2nf half of 1944, at low altitudes. It was never fitted with bombs or rockets. Armament depended on light guns and somewhat limited ammo capacity (20mm was hard hitting while the ammo lasted, 9 sec) It didn't fly quite as well as the bigger Yaks and they all had issues, like weak/unreliable landing gear but HEY! the landing gear was light! They also had primitive instrumentation and not very good radios......................but the instrument panel and radio were light! Seeing a pattern here?
Light, ill equipped fighters can do a good job in certain roles IF you have other aircraft to perform the other roles. Higher altitude combat, longer range combat, bomber interception, ground support.

The Ki-44 had light armament most of the time. It could carry a pair of 100kg bombs (or 130 liter drop tanks).

Now, do the French need to push past the 1300-1400hp mark to deal with the heavy 109s?
Let's remember that the Germans had gone from about 1100hp in the middle of 1940 to about 1400hp (if things worked right) in the fall of 1942. Depending on 1300-1400hp engines in 1943 and later and light weight construction depends a bit too much on knowing what happened.

The French are forced into light weight fighters because of their engine as it is. They were trapped in mid to late 30s and there is no way out without some unknown design popping up or building Allison's/Merlin's in France which was not going to happen unless much of France stayed Free in 1940. It wasn't going to happen under a Vichy or Vichy like arrangement.

As far as engines go, a lot things happen behind the scenes. Allison got very lucky several times and not so lucky a few times.
Allison found a new way of casting crankcases/cylinder blocks (developed by a husband-wife team of artist/sculptors, not by Allison) that allowed for stronger parts and more precision (less machining after casting) and might have even saved a few pounds. Allison didn't invent nitriding but when they nitrided their crankshafts they gained a huge amount in fatigue resistance. The two together allowed Allison engines to stand up to a large amount of abuse (war emergency power). On the other hand, in late 1941 Allison was trying to make engines with higher supercharger gears to add several thousand feet of altitude to the engines. But the way the Allison is designed the supercharger gears can only be so wide to fit in the housing which is cast into the crankcase (then covered with the auxiliary back plate) and the increase power needed to drive the supercharger faster stripped the gears in a short period of time. It took almost a year to get the block castings and auxiliary back plate cover sorted out to accept the wider gears.
The Allison was strong enough to hand 1400-1500hp at WEP running on 100/130 fuel which greatly reduced the need to fit a two speed supercharger (using the original supercharger) however that was not the fuel the engine was designed to run on. Allison then dropped the ball on the two mechanical stage engines.

 

[tomo pauk]

The Yak-3 it trotted out in the light weight fighter crowd all the time. How long did it take to show UP? What could it do when it got there (it was fast). What couldn't it do? It did well against the 109s/190s over the eastern front in the 2nf half of 1944, at low altitudes. It was never fitted with bombs or rockets. Armament depended on light guns and somewhat limited ammo capacity (20mm was hard hitting while the ammo lasted, 9 sec) It didn't fly quite as well as the bigger Yaks and they all had issues, like weak/unreliable landing gear but HEY! the landing gear was light! They also had primitive instrumentation and not very good radios......................but the instrument panel and radio were light! Seeing a pattern here?
Light, ill equipped fighters can do a good job in certain roles IF you have other aircraft to perform the other roles. Higher altitude combat, longer range combat, bomber interception, ground support.

Yak 3 was a way to make a lemonade, since the most likely available engine was a lemon - in 1944, it was no better than the Merlin III of 1939 (assuming both engines use the fuel of same octane/PN). Basically, Yak-3 have had the worst V12 of all V12s in 1944, and it was still a reasonably good fighter.
Firepower was no worse than what the P-51B had, that still was bagging the Fw 190s and Bf 110s.
'Accusing' a fighter that was not that good in carrying bombs or rockets misses the point of an A/C being a fighter.

French, assuming that they brace through 1940 and 41 in a reasonable shape, can have the fighter that equals the Yak-3 (as well as the German or Italian opposition) in performance by 1941, or by 1942 to be conservative.

Now, do the French need to push past the 1300-1400hp mark to deal with the heavy 109s?
Let's remember that the Germans had gone from about 1100hp in the middle of 1940 to about 1400hp (if things worked right) in the fall of 1942. Depending on 1300-1400hp engines in 1943 and later and light weight construction depends a bit too much on knowing what happened.

The Allison was strong enough to hand 1400-1500hp at WEP running on 100/130 fuel which greatly reduced the need to fit a two speed supercharger (using the original supercharger) however that was not the fuel the engine was designed to run on.

Has the altitude where the engine was making it's power became irrelevant as a metric?
A 2-speed S/C, that has the 2nd gear running faster than the original type, was a necessity for the V-1710 between 1941 and 1943.

Allison then dropped the ball on the two mechanical stage engines.

Before that, they also dropped the ball on the 1-stage mechanical superchargers - a much greater sin, since it affected the air battles during the (many times dark) 1942 year.

 

[bf109xxl]

In general I agree with tomo pauk , just to add a little bit about the Yak-3.

The Japanese and Russian aircraft were not as well protected as British/German/US fighters.

Actually, the Soviets themselves assumed that Japanese fighters were much worse protected than the Soviet ones. At least, the inert gas pressurization system on Soviet planes appeared in the late 30s, as well as the self-sealing coating of fuel tanks. The Ki-44 got an armored pilot's seat back and protected fuel tanks near the end of production.

The Yak-3 it trotted out in the light weight fighter crowd all the time. How long did it take to show UP? What could it do when it got there (it was fast). What couldn't it do? It did well against the 109s/190s over the eastern front in the 2nf half of 1944, at low altitudes. It was never fitted with bombs or rockets. Armament depended on light guns and somewhat limited ammo capacity (20mm was hard hitting while the ammo lasted, 9 sec) It didn't fly quite as well as the bigger Yaks and they all had issues, like weak/unreliable landing gear but HEY! the landing gear was light! They also had primitive instrumentation and not very good radios......................but the instrument panel and radio were light! Seeing a pattern here?
Light, ill equipped fighters can do a good job in certain roles IF you have other aircraft to perform the other roles. Higher altitude combat, longer range combat, bomber interception, ground support.

The main problem of Yak-3 was small combat range, pilot was protected by armored seat back, fuel tanks had self-sealing coating (main tanks - only at the bottom) and inert gas pressurization system (I won't evaluate the effectiveness of fuel system protection, but previous Yak models had problems with it). Yes, I agree - lack of armored windscreen, plywood skin, etc., all this was not up to the level of Western fighters, but due to good flight performance Yak-3 losses were relatively low compared to other Soviet fighters within the same time period. The Soviet radio equipment (RSI-4 kit ~13 kg) weighed about the same as the Allies one (e.g. SCR-695), but with much worse performance. By the way, the Yak-3 had one of the most advanced instrumentation for Soviet fighters. None of the Yak-3 pilots complained about the firepower, they found it quite adequate.
Perhaps the French would be satisfied with the Yak-3's range...

 

[Shortround6]

Yak 3 was a way to make a lemonade, since the most likely available engine was a lemon - in 1944, it was no better than the Merlin III of 1939 (assuming both engines use the fuel of same octane/PN). Basically, Yak-3 have had the worst V12 of all V12s in 1944, and it was still a reasonably good fighter.
Firepower was no worse than what the P-51B had, that still was bagging the Fw 190s and Bf 110s.
'Accusing' a fighter that was not that good in carrying bombs or rockets misses the point of an A/C being a fighter.

1. Not sure about the Merlin III being better or worse. It may very well have been better. does anybody have any information on the Yak-3s engine running on better fuel?
2. Firepower vs the P-51 is as good as long as the 20mm gun is firing, which it will stop doing in about half the time it takes for the outer guns on the P-51B to stop.
3. For being a "pure" fighter you are right. Russians had 'provisions' for hanging 6 rockets or a pair of 100kg bombs on most of their other fighters, or sometimes two 50kg and two 25kg bombs? By the time the Yak-3 showed up it could be a 'specialist". Can the French fighters of 1942-43 be specialists or do they need to have the capability (even if not used much) to do more?

French, assuming that they brace through 1940 and 41 in a reasonable shape, can have the fighter that equals the Yak-3 (as well as the German or Italian opposition) in performance by 1941, or by 1942 to be conservative.

This assumes the Hispano 12?? actually works as advertised. The M-106 did not. The H-S 12Y-51 did not work as advertised for the Swiss for several years.

Has the altitude where the engine was making it's power became irrelevant as a metric?
A 2-speed S/C, that has the 2nd gear running faster than the original type, was a necessity for the V-1710 between 1941 and 1943.

1. it depends on what the metric is showing. In the case of the Allison it shows that the basic engine will survive making the desired power, the problem was getting the supercharger to deliver the needed air at high altitudes. No need to redesign the crankcase and crankshaft (and other bits).
2. It did need a new supercharger by 1943, Even the 9.6 gears were not enough to save the day.

Before that, they also dropped the ball on the 1-stage mechanical superchargers - a much greater sin, since it affected the air battles during the (many times dark) 1942 year.

The strength of the engine and 100/130 fuel papered over the low altitude performance in 1942. The American problem was not really the Allison engine, it was the sometimes extra 1 ton of weight the American fighters were lugging around. Stick a Soviet M-105PF engine in a P-40K and figure out what happens

 

[Shortround6]

By the way, the Yak-3 had one of the most advanced instrumentation for Soviet fighters.

Talk about damning with faint praise
Now since the soviets built in numerous batches and things changed from one batch to another I may be guilty of using a bad source.
But no gyroscopic instruments (?), Blind flying done on primary instruments?
Compared to an early I-16 which had no fuel gauge the Yak-3 might be considered well equipped.
Most US fighters carried multiple radios. They didn't change frequency (channel) on the radio itself. The Selector in the cockpit changed the transmitter and receiver themselves to the 'new' (preselected) frequency. I may not be wording that right. The US radio rack sometimes had 3 receivers and two transmitters (?) and the selector changed to a new/different set.

None of the Yak-3 pilots complained about the firepower, they found it quite adequate.

What did they have to compare it to

Now the problem for the similar weight light French fighter is that the 20mm Hispano cannon weighs around 18kg more than the 20mm ShVAK cannon. The 20mm Hispano ammo weighs more. The French have no 12.7mm gun ( and the US gun is about 4kg heavier than the Soviet one) so the default is multiple 7.5mm guns. (6 or more?)
One 20mm HS cannon weighs as much as 7 of the 7.5mm machine guns. 500rpg for 6 guns is around 81 kg of ammo.

A lot of people seem to want the benefits of the Yak-3 performance/light weight. How many want to pay the cost?

 

[tomo pauk]

1. Not sure about the Merlin III being better or worse. It may very well have been better. does anybody have any information on the Yak-3s engine running on better fuel?
2. Firepower vs the P-51 is as good as long as the 20mm gun is firing, which it will stop doing in about half the time it takes for the outer guns on the P-51B to stop.
3. For being a "pure" fighter you are right. Russians had 'provisions' for hanging 6 rockets or a pair of 100kg bombs on most of their other fighters, or sometimes two 50kg and two 25kg bombs? By the time the Yak-3 showed up it could be a 'specialist". Can the French fighters of 1942-43 be specialists or do they need to have the capability (even if not used much) to do more?

1. Merlin III was good for 1300 HP on the very early 100 oct fuel. Seems like the 105-PF2 needed mods vs. the 105PF in order to make the 1300 HP power; Soviet hi-oct fuel being in the ball park with the 'legacy' 100 oct fuel? On these kind of fuels, Merlin III was also making a bit better power at every altitude we choose, bar under 1 km, and without accounting for the even higher overboost for the FAA Merlin IIIs.
2. Nobody was touting that Yak-3 or it's other European counterparts were good for multi-hour 1500 mile missions over the enemy land.
3. P-40s the French were buying will do just fine as fighter bombers (when that idea dawns on the French, talk mid-1941?), so will the UK-produced fighters, like Hurricane. Trying to came out with the all-dancing all-singing fighters might be a recipe for a failure
French have the MB fighters to try in that role after all, should they feel the urge.

This assumes the Hispano 12?? actually works as advertised. The M-106 did not. The H-S 12Y-51 did not work as advertised for the Swiss for several years.

The HS 12Z might not be making 1600 HP at 6 km in 1942-43, but it might be making 1300-1400 at 5 km.

1. it depends on what the metric is showing. In the case of the Allison it shows that the basic engine will survive making the desired power, the problem was getting the supercharger to deliver the needed air at high altitudes. No need to redesign the crankcase and crankshaft (and other bits).
2. It did need a new supercharger by 1943, Even the 9.6 gears were not enough to save the day.

The 'altitude power' metric is showing how good was the engine ABC at the higher altitudes when compared with the competing engine XYZ or RPQ. Per that metric, V-1710 was not as good as the German competition (typically DB 601/605), or the British competition (Merlin); comparison vs. the BMW 801 or Griffon is ever worse for the V-1710. Even for the altitudes of 5-6 km, let alone for 8+ km
Unfortunately, the V-1710 badly needed the improvement of the S/C already before the time of Pearl Harbor attack.

The strength of the engine and 100/130 fuel papered over the low altitude performance in 1942. The American problem was not really the Allison engine, it was the sometimes extra 1 ton of weight the American fighters were lugging around. Stick a Soviet M-105PF engine in a P-40K and figure out what happens

Suggesting that the 6th/7th best V12 ( forgetting for the momet the radials that were making better altitude power than the V-1710) is installed in the place of the 4th/5th best V12 does not do any favors to the P-40.
As for about lugging a lot more stuff around - engine should do it's part, too. See how much the P-40F was better performer than the P-40E, and the F was powered by the engine that was not that great anymore.

 

[bf109xxl]

But no gyroscopic instruments (?), Blind flying done on primary instruments?
Compared to an early I-16 which had no fuel gauge the Yak-3 might be considered well equipped.

I did not compare the quality of the instruments, I just pointed out that the Yak-3 was not lightened at the expense of the instruments. And a hypothetical lightweight French fighter could be equipped with quite adequately. A fighter with a typical flight time of about 45-50 minutes does not require the same set of equipment, as for twice as heavy escort fighter with a flight time of several hours.

Most US fighters carried multiple radios. They didn't change frequency (channel) on the radio itself. The Selector in the cockpit changed the transmitter and receiver themselves to the 'new' (preselected) frequency. I may not be wording that right. The US radio rack sometimes had 3 receivers and two transmitters (?) and the selector changed to a new/different set.

The same concerns the radio equipment: I pointed out that the weight of the Soviet equipment was approximately equal to the weight of the American one (undoubtedly of much higher quality), which most likely would be installed on a hypothetical "French Yak-3", even two stations for different frequency bands are quite possible - 12-13 kg a not so crucial.

What did they have to compare it to

And why compare if the pilots found it quite sufficient?

Now the problem for the similar weight light French fighter is that the 20mm Hispano cannon weighs around 18kg more than the 20mm ShVAK cannon. The 20mm Hispano ammo weighs more. The French have no 12.7mm gun ( and the US gun is about 4kg heavier than the Soviet one) so the default is multiple 7.5mm guns. (6 or more?)
One 20mm HS cannon weighs as much as 7 of the 7.5mm machine guns. 500rpg for 6 guns is around 81 kg of ammo.

A lot of people seem to want the benefits of the Yak-3 performance/light weight. How many want to pay the cost?

The French could save weight (80-100 kg, I believe) by using metal as structural material for the wing and skin. And voila - they could install heavier cannon and machine guns. I find it very probable that the "Yak-3 way" was the most preferable for the French. The only question is the combat range. If we assume that the French will not be engaged in escorting heavy bombers, and operate at heights typical for German bombers (4-5 km, as on the Eastern Front), then the "French Yak-3" would be quite adequate.

 

[Luft.4]

In general I agree with tomo pauk , just to add a little bit about the Yak-3.

Actually, the Soviets themselves assumed that Japanese fighters were much worse protected than the Soviet ones. At least, the inert gas pressurization system on Soviet planes appeared in the late 30s, as well as the self-sealing coating of fuel tanks. The Ki-44 got an armored pilot's seat back and protected fuel tanks near the end of production.

The main problem of Yak-3 was small combat range, pilot was protected by armored seat back, fuel tanks had self-sealing coating (main tanks - only at the bottom) and inert gas pressurization system (I won't evaluate the effectiveness of fuel system protection, but previous Yak models had problems with it). Yes, I agree - lack of armored windscreen, plywood skin, etc., all this was not up to the level of Western fighters, but due to good flight performance Yak-3 losses were relatively low compared to other Soviet fighters within the same time period. The Soviet radio equipment (RSI-4 kit ~13 kg) weighed about the same as the Allies one (e.g. SCR-695), but with much worse performance. By the way, the Yak-3 had one of the most advanced instrumentation for Soviet fighters. None of the Yak-3 pilots complained about the firepower, they found it quite adequate.
Perhaps the French would be satisfied with the Yak-3's range...

Where was the plywood skin present on the Yak-3?

 

[bf109xxl]

Soviet hi-oct fuel being in the ball park with the 'legacy' 100 oct fuel?

What is "'legacy' 100 oct fuel"?
Soviet oil refining technologies were rather backward, based on Western developments of the mid-1920s: catalytic cracking was practically not used, synthesis of high-octane components just started during the war and its scale was insufficient. ON of Soviet gasoline without addition of TEL and iso-octane was at best 74 (B-74), already B-78 was a mixture of gasoline B-70 with iso-octane.

 

[tomo pauk]

What is "'legacy' 100 oct fuel"?

The early 100 oct fuel, that was not as 'good' as the 100/130 grade used from 1942 on. Rich rating going to 115-120 IIRC.

 

[Luft.4]

What is "'legacy' 100 oct fuel"?
Soviet oil refining technologies were rather backward, based on Western developments of the mid-1920s: catalytic cracking was practically not used, synthesis of high-octane components just started during the war and its scale was insufficient. ON of Soviet gasoline without addition of TEL and iso-octane was at best 74 (B-74), already B-78 was a mixture of gasoline B-70 with iso-octane.

Soviet front line aircraft used 3B-78 or 4B-74 with a MON ~95. This is backed up by the flight manuals of the Soviet aircraft too (see attached):
Imported Allied fuels were B95 or B100. Luftwaffe fuel bases (both for B4 and C3) were only sightly better and had a MON of just under 80 before TEL was added.

 

[bf109xxl]

Where was the plywood skin present on the Yak-3?

Wing, tail section of the fuselage (2mm plywood).

Source:

 

[Luft.4]

Wing, tail section of the fuselage (2mm plywood).
View attachment 785153
Source:
View attachment 785154

Thanks! its on page 115-116.

 

[bf109xxl]

Soviet front line aircraft used 3B-78 or 4B-74 with a MON ~95. This is backed up by the flight manuals of the Soviet aircraft too (see attached):
Imported Allied fuels were B95 or B100. Luftwaffe fuel bases (both for B4 and C3) were only sightly better and had a MON of just under 80 before TEL was added.

The quality of aviation gasoline is determined by a hydrocarbon base with a much lower octane rating. The number before "B" means milliliters of TEL per kg.

"Slightly better" than gasoline made from one of the highest quality crude oils - the highest praise for German engineers who were able to achieve such quality using frankly shitty raw materials.

 

[Luft.4]

The quality of aviation gasoline is determined by a hydrocarbon base with a much lower octane rating. The number before "B" means milliliters of TEL per kg.
View attachment 785156

"Slightly better" than gasoline made from one of the highest quality crude oils - the highest praise for German engineers who were able to achieve such quality using frankly shitty raw materials.

The Luftwaffe produced high octane gasoline with no hope of utilizing its full potential as their engines could not take full advantage of the power for various reasons. This is especially true for the 1942/1943 time frame. I am doubtful whether Soviet crude was of the highest quality, however each nation did the best they could to get maximum performance our of their engines.
The fact that the Luftwaffe could sufficiently fuel it's aircraft, even as early as 1941, is somewhat of a miracle in part thanks to captured fuel stocks in the 1940/1941 time frame. The process of coal to gasoline picked up by 1943 but there was never enough.
All the best,
Dan.

 

[bf109xxl]

The Luftwaffe produced high octane gasoline with no hope of utilizing its full potential as their engines could not take full advantage of the power for various reasons.

German industry did not produce _high_ octane gasoline. C3 was widely used.

This is especially true for the 1942/1943 time frame. I am doubtful whether Soviet crude was of the highest quality, however each nation did the best they could to get maximum performance our of their engines.

I was talking about the Baku crude oil only (now it is Azeri Light). IIRC, the quality of Caucasian crude oil (Grozny) was also high. Only these products were used for aviation gasoline production in the USSR because their refinement to the acceptable quality does not require advanced technologies like catalytic cracking. Crude oil from Volga region contains much more sulfur and required more complicated technologies.

The fact that the Luftwaffe could sufficiently fuel it's aircraft, even as early as 1941, is somewhat of a miracle in part thanks to captured fuel stocks in the 1940/1941 time frame. The process of coal to gasoline picked up by 1943 but there was never enough.

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.

 

[Luft.4]

I am not understanding your first quote, C3 was a high octane fuel. On par with US 100/130 grade, some test even state close to US 100/150 grade. Am I misunderstanding you?
I know of at least 3 Soviet oil fields that were used: Baku, Grozny and Ufimskoye. These are openly listed in aircraft engine manuals so they were used for aviation gasoline production.
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.
All the best,
Dan.

 

[tomo pauk]

There is excellent information on the Luftwaffe's oil situation found in BaMA RL 2-VI 115 pages 2-3.

Thank you for this.
The search engine accepts "RL 2-VI/115" in the search field, FWIW.