Advanced French Fighters vs 1942/1943 contemporaries

[TM06]

300-400 kg? That was probably the weight of the whole wing?
Small wing of the D.550, that also had no support for the tanks and weapons, was lighter by 140 kg than the bigger wing of the D.520 that supported also the tanks and firepower.

The weight of the entire aircraft itself was 300~400 kg lighter than the D.520. Again, I'm unsure on the specific distribution of that weight.
Marcel Doret (test pilot of Dewoitine) wrote an article in French about the aircraft, with the statement that "The D.520 was a Percheron while the D.550 was a thoroughbred."
They're a bit hard to read but here's that article.

 

[tomo pauk]

The weight of the entire aircraft itself was 300~400 kg lighter than the D.520. Again, I'm unsure on the specific distribution of that weight.

Sorry, my bad here
300-400 kg lighter than the D.520 was probably attainable, eg. already having 230 L of fuel less is some 170 kg less.

 

[Bretoal2]

Sorry, my bad here
300-400 kg lighter than the D.520 was probably attainable, eg. already having 230 L of fuel less is some 170 kg less.

You may read this (and other pages from the site)

https://replicair.fr/avions/dewoitine-d551/dewoitine-histoire/

 

[tomo pauk]

You may read this (and other pages from the site)

https://replicair.fr/avions/dewoitine-d551/dewoitine-histoire/

I've already linked to that page earlier

 

[Shortround6]

The Yak-3 used a ~575 kg VK-105PF3 engine making about 1,200~1,300 horsepower nominally, the D.551 used a ~490 kg Hispano 12Y-51 making ~1,100 horsepower nominally, the former being a derivative of the base design of the latter, both of which are noted for relative unreliability.

What matters is the power at altitude. The H-S 12Y-51 rated at 1000hp at 3260 meters. The VK-105 engines were good for about 1050hp at 4000 meters and could hit a bit over 1200hp at a little over 2000 meters, this is the later versions. The -51's 1100hp was take off, it had a single speed supercharger.

The base Yak-3 used an armament layout of 1 x 20 mm cannon and 2 x 12.7 mm heavy machine guns, the D.551 used an armament layout of 1 x 20 mm cannon and 6 x 7.5 mm machine guns which are similar in terms of burst mass (1 12.7 machine gun was worth 3 rifle calibre machine guns according to US testing).

Americans were not testing Soviet or French machine guns. Different rates of fire and different bullet weights. The vast majority of Yak-3s carried about 75kg worth of guns ,the light 20mm weighed about the same as the 12.7mm gun, some carried less. A single 20mm H-S weighs about 60kg, not including either drum or belt feed unit.

Your apprehension towards the 12Z is understandable given that its life was cut short due to the circumstances around it, however I should note again that the VK-107 engine is highly similar to the 12Z engine, meaning it can be used for comparison.

Soviets didn't get the VK-107 to run properly until after the war. They also stopped production twice immediately after the war (Sept- Dec 1945 and April-Oct) 1946 to sort out problems. Some planes got the engines during the war, actual service use was limited. VK-107 also went about 765-770kg.

In fact, the Hispano 12B proved that in this very thread by being capable of 1,750 hp at 4,000 m/8,100 m. This is purely speculation on my part, but had France been allowed to continue developing its engines and aircraft, I could see the 12B or an engine like it seeing service in 1944~1945 as the war delayed France's engine development by about 4~5 years.
They probably still wouldn't be the most reliable engines out there, but every engine has its flaws.

Post war development is rather problematic. For everybody. Smaller budgets but more widespread knowledge of what others did and better access to raw materials.
There were several 12B engines. The one that offered 1750hp at 8,1000 meters was a rather complicated turbo charger set up. It not only was the 1st stage in the turbo supercharger set up it also used the exhaust gas energy to power fans that force air through the engine coolant radiators and then mixed the hot from the radiators, a bit of cool air (by pass?) into a duct surrounding the exhaust gases. The whole thing (including radiators?) went under 500kg over the weight of the bare engine. 1948-51 was a period of trying to get better fuel economy and Wright was working on Turbo compound engines (a little earlier than the French) and Napier went of the deep end ( or had failed to make shore after the Sabre) and disappeared into the Nomad depths.

Didn't get around to this last time, but that's not exactly a fair description of the D.55x series.
While yes, the D.550 was a speed-record plane, it was based on the airframe of the D.520 - a dedicated fighter aircraft. If anything, the D.55x series is a return to form and the D.550 is the odd-one-out.

Problem is that some of the performance estimates seem to based off the D.550 with it's 116ft sq ft wing, low canopy and few other "tweaks" that need to changed, (higher canopy?).
Quoted power used in the D.550 is all over the place. From 860hp to 1300hp depending on source. Sources can't even agree on which engine was used or what, if anything, was done to the engine. British were NOT using a "stock" Merlin in the "Speed Spitfire" and the Germans sure weren't using stock DB601s in the Heinkel 100 or Me 209 record setters.

Where did the D 551 wing wind up in size?
140 sq ft?

What was an actual service D. 551 actually going to weigh?
Were they really going to keep the retractable tail skid (not wheel).

Does anybody really know what the fuel capacity was?
Still trying to figure out how an engine that has an FTH of 3260 meters lets an airplane have a max speed at 6000 meters. Greatest use of RAM ever seen?

French had a real thing for small wings and small airplanes. Granted they had low powered engines, problem is it is harder to "grow". Field performance is also a problem.
Allisons and Merlins could grow with better fuel, they had the Strength to handle the higher loads. The Hispano V-12 wasn't strong enough to grow easily.

 

[tomo pauk]

Quoted power used in the D.550 is all over the place. From 860hp to 1300hp depending on source. Sources can't even agree on which engine was used or what, if anything, was done to the engine.

My understanding, reading the French book about the D.520, is that the original engine was the legacy 12Ycrs type of 900 HP. In such form, the 1st flight tests were made in summer of 1939.
Engine change was planned, with the 12Y-51 taking the place, but German records with 2000+ HP engines made that not making sense, so the 12Y-89 of 1200 HP 'on the bench' ('en banc'; future 12Z prototype?) was installed, and the 1st flight was on October 23rd 1939. Max speeds were, per book, 677 km/h at 6000m with cooling flap open, and 695 km/h at 5750m with cooling flap closed. Same source says 702 km/h was attained at 6000m in November 22nd.
Boost figures were above 800 mm Hg from SL to 5750m (with ram); max boost 835 mm Hg.

Does anybody really know what the fuel capacity was?

400 (410?) liters.

 

[bf109xxl]

The Yak-3P used the Berezin B-20 20 cannon which was enough lighter that 3 of them weighed about the same as two ShVAK cannon. But those cannon didn't show up until 1944 in small numbers, a lot more later. In fact most Yak-3s used the B-20 cannon which saved about 17kg over the ShVAK cannon and about 35kg over the Hispano gun.

Production of the Yak-3P began in April 1945 in addition to production of the Yak-3. The production of the Yak-3 was fully switched to the Yak-3P in August 1945, 596 were built. The vast majority of Yak-3s were produced with one ShVAK and 1-2 UBS (197 with a single UBS, 4004 with two UBSs). Indeed, the B-20 was just a conversion of the UB for the ShVAK cartridge, the gun was not reliable enough, as the tests on the La-7 in the fall of 1945 showed.

The Yak-3 used a ~575 kg VK-105PF3

600-620 kg VK-105PF-2

used on the Yak-3M

The airplane with this designation did not exist. The Yak-3 VK-107A existed in different variants, the prototypes had significant shortcomings, and only the all-metal version was built in homeopathic quantities.

to the VK-107B

The engine with this designation did not exist even as a project.

 

[bf109xxl]

The VK-105 engines were good for about 1050hp at 4000 meters and could hit a bit over 1200hp at a little over 2000 meters, this is the later versions.

Just as an illustration:

 

[TM06]

Edited and removed due to mistakes

 

[MikeMeech]

I'm well aware of this. In the direct comparison I made between the D.551 and the Yak-3, I chose that base armament layout for the Yak-3;
The base Yak-3 used an armament layout of 1 x 20 mm cannon and 2 x 12.7 mm heavy machine guns, the D.551 used an armament layout of 1 x 20 mm cannon and 6 x 7.5 mm machine guns which are similar in terms of burst mass (1 12.7 machine gun was worth 3 rifle calibre machine guns according to US testing).

I don't know where you're getting that information from because the VK-108 engine definitely did exist. One was fitted to a modified Yak-3, something I remember very clearly due to it dethroning my beloved I-225 as the fastest Soviet prop fighter. I've linked the Images of that aircraft below, with the most easily recognizable differences between it and the VK-107 model being the heat-resistant panels behind the exhaust stacks.

Hi
As bf109xxl mentioned no VK-107B (maybe typo for VK-107R?). But there were a limited number of VK-108, as per 'Russian Piston Aero Engines' by Vladimir Kotelnikov:

Mike

 

[TM06]

Hi
As bf109xxl mentioned no VK-107B (maybe typo for VK-107R?). But there were a limited number of VK-108, as per 'Russian Piston Aero Engines' by Vladimir Kotelnikov:
View attachment 779696
View attachment 779697
View attachment 779698
Mike

Ah. It appears I'm blind. My mistake. It's very early in the morning here and my sleep-deprived brain mistook the B for an 8.
I read before that the VK-107B was the designation for the variant with water injection, but I might also be wrong there too.

 

[bf109xxl]

I'm well aware of this.

It was a reply to another forum participant (Shortround6), not to you. Please be more attentive.

 

[TM06]

It was a reply to another forum participant (Shortround6), not to you. Please be more attentive.

Another sleep-deprived mistake, my bad.

 

[Bretoal2]

Another sleep-deprived mistake, my bad.

Hope your sleep-deprived eyes saw (page 143 from Kotelnikov) that side views of VK 107 in Yak-3 and I-320 show SEVEN exhaust pipes....

 

[Shortround6]

Getting back to the French in 1939-40 and what they could have done in 1942-3 and how it relates to the Soviet engine experience.
The Russian VK-107 projected started in 1940 as shown by MikeMeech. The M-106 project started in 1938. Soviet engine development had several trials and tribulations during WW II.
The a large part of the whole story of the M-100 to M-105 series was the constant Soviet work to get the Hispano engine to make power and be more reliable/longer lived than original French engines. Original contract dates to late 1933. The original contract called for the French to keep the Soviets informed of all changes made/introduced to the French engines up until March 1938. Not sure if this was followed or not.
The Soviet M-103 engines show the first real departures from the French Hispanos. M-103 project stared in 1936 and the first production engines were built in May of 1938.
Soviet production on the M-100 lasted into 1940, Production of the M-103 lasted until 1942.
Now the M-103 gained about 25-30kg depending on exact models. It seems to have gained about 50rpm (?). It also, in the 2nd version, had the bore reduced from 150mm to 148mm to make the cylinders stronger. Other modifications are listed but details are not given. You will find statements like "Strengthen crankshaft" repeated a number of times in Kotelnikov's book but I have no idea what the changes were. Beefed up webs? different heat treatment? different steel alloy?
The M-103 was rated at 1000hp (take-off?) and 950hp (960?) at 4000 meters which is in the area of the French -36 to -41 engines. Soviets might be a little ahead.

Now in 1938, 39 and 40 the French are working on the -45 to -49 engines with the Szydlowsky-Planiol (SP) supercharger with higher altitude but no real increase in power (low 900s)
and they are just getting the -50/51 engines into production in the spring of 1940. The French now have 1100hp for take-off and 1000hp at 3260 meters for a 492kg engine.

The Soviet M-104 engine of 1939 (232 built, all in 1939) was rated at 1100hp for take-off, 1050hp at altitude and weight had gone to 550kg with it's two speed supercharger.
Quite possible the Szydlowsky-Planiol was a better set up. The Soviet M-103 and M-104 used 6.6 compression ratio compared the French 7.0 in the majority of their engines.

Now we get into the real departures. The M-105 project started in 1937 with the goal of of 1100hp T-O/1050hp at altitude for a weight of 510 kg. Production starts at the end of 1939 but there a problems. By the time things are sorted out the weight has gone to 570kg and it is mid to late 1940. This would be the M-105N in the chart above. France has already fallen.
The Soviets are using 2700rpm and a two speed supercharger.
The -51 Hispano is the engine the Swiss licensed and it took them about 2 years (?) to get the thing up to the standards that the Swiss wanted. It is also the reason that the Swiss designed the YS-2 engine. Maybe they wanted fewer engine failures/crashes?
Swiss went from a 520kg engine to a 685 kg engine to get another 100rpm (2600rpm) and to get 1300hp for take-off and 1410hp at 4800meters. Single speed supercharger.
They were using Direct fuel injection, 4 valve heads, slightly higher boost, and much heavier crankshaft, possibly a bit lower compression. The YS-2 doesn't show up until 1944 or later.

Granted the soviets had problems with engine development in 1941-42 but they didn't get the M-107 sorted out until after the war ended. They never got the M-106 sorted out and/or thought it wasn't worth the trouble (small gain in power?)
Expected the 12Z to show up, sorted out and in sizable production in 1942-43 seems a stretch. The Hispano Paris area factories were about 200 miles from the German border and if the Germans make much progress and/or take Belgium they are around 130-140 miles from the border, adjust as necessary.
Hispano was setting up or had set up a factory in Tarbes (about 35-40 miles from the Spanish border and was working on setting up an under ground factory in Jonzac, about 40-50 miles north of Bordeaux, There was a least one train load of tools and parts sent from Paris to other place/s (Tarbes and Barcelona) right at the end. Tarbes was were development of the 12Z was located after the French surrender. Or at least French development.
Post war development assessment is also hard to judge. Birkigt had escaped to Spain for the duration of the war and When he returned to France full time he ran into some unhelpful politicians/officials. One insisted he work on 22 different projects at once. Birkigt retired and moved to Switzerland These changes in head designer/s did not help 12Z development.
The 12Z Ter was supposed to have reached 1300hp at 4000meters with an H-S compresser in using fuel injection.

British factories could be and were bombed. But the likelihood of invasion, over running was pretty unlikely. How much disruption moving the H-S Paris factories would have meant?
As far as building RR or Bristol engines in France? Lets remember that Packard was looking at the Merlin engine in July/Aug of 1940, Contract sighed in Sept 1940. Packard had plant that was building large cars and 41 liter PT boat engines and had a skilled work force. Packard built 45 Merlins in 1941, 26 of them in Dec.
Factory, work force and machine tools would come from where for French production of British designs?

The French would not be stuck in 1940 but some of the French plans were somewhat on the Grandiose side.

 

[bf109xxl]

Other modifications are listed but details are not given.

Try to read original sources:

 

[bf109xxl]

the soviets had problems with engine development in 1941-42

And what happened afterwards? The VK-107 was never brought up to the required condition, the ASh-82 achieved acceptable reliability only in 1945, high-altitude piston engines never reached the serial production, but the Soviets got lucky with the transition to jet engines - they suddenly got access to German and British technology.

 

[Bretoal2]

Getting back to the French in 1939-40 and what they could have done in 1942-3 and how it relates to the Soviet engine experience.
The Russian VK-107 projected started in 1940 as shown by MikeMeech. The M-106 project started in 1938. Soviet engine development had several trials and tribulations during WW II.
The a large part of the whole story of the M-100 to M-105 series was the constant Soviet work to get the Hispano engine to make power and be more reliable/longer lived than original French engines. Original contract dates to late 1933. The original contract called for the French to keep the Soviets informed of all changes made/introduced to the French engines up until March 1938. Not sure if this was followed or not.
The Soviet M-103 engines show the first real departures from the French Hispanos. M-103 project stared in 1936 and the first production engines were built in May of 1938.
Soviet production on the M-100 lasted into 1940, Production of the M-103 lasted until 1942.
Now the M-103 gained about 25-30kg depending on exact models. It seems to have gained about 50rpm (?). It also, in the 2nd version, had the bore reduced from 150mm to 148mm to make the cylinders stronger. Other modifications are listed but details are not given. You will find statements like "Strengthen crankshaft" repeated a number of times in Kotelnikov's book but I have no idea what the changes were. Beefed up webs? different heat treatment? different steel alloy?
The M-103 was rated at 1000hp (take-off?) and 950hp (960?) at 4000 meters which is in the area of the French -36 to -41 engines. Soviets might be a little ahead.

Now in 1938, 39 and 40 the French are working on the -45 to -49 engines with the Szydlowsky-Planiol (SP) supercharger with higher altitude but no real increase in power (low 900s)
and they are just getting the -50/51 engines into production in the spring of 1940. The French now have 1100hp for take-off and 1000hp at 3260 meters for a 492kg engine.

The Soviet M-104 engine of 1939 (232 built, all in 1939) was rated at 1100hp for take-off, 1050hp at altitude and weight had gone to 550kg with it's two speed supercharger.
Quite possible the Szydlowsky-Planiol was a better set up. The Soviet M-103 and M-104 used 6.6 compression ratio compared the French 7.0 in the majority of their engines.

Now we get into the real departures. The M-105 project started in 1937 with the goal of of 1100hp T-O/1050hp at altitude for a weight of 510 kg. Production starts at the end of 1939 but there a problems. By the time things are sorted out the weight has gone to 570kg and it is mid to late 1940. This would be the M-105N in the chart above. France has already fallen.
The Soviets are using 2700rpm and a two speed supercharger.
The -51 Hispano is the engine the Swiss licensed and it took them about 2 years (?) to get the thing up to the standards that the Swiss wanted. It is also the reason that the Swiss designed the YS-2 engine. Maybe they wanted fewer engine failures/crashes?
Swiss went from a 520kg engine to a 685 kg engine to get another 100rpm (2600rpm) and to get 1300hp for take-off and 1410hp at 4800meters. Single speed supercharger.
They were using Direct fuel injection, 4 valve heads, slightly higher boost, and much heavier crankshaft, possibly a bit lower compression. The YS-2 doesn't show up until 1944 or later.

Granted the soviets had problems with engine development in 1941-42 but they didn't get the M-107 sorted out until after the war ended. They never got the M-106 sorted out and/or thought it wasn't worth the trouble (small gain in power?)
Expected the 12Z to show up, sorted out and in sizable production in 1942-43 seems a stretch. The Hispano Paris area factories were about 200 miles from the German border and if the Germans make much progress and/or take Belgium they are around 130-140 miles from the border, adjust as necessary.
Hispano was setting up or had set up a factory in Tarbes (about 35-40 miles from the Spanish border and was working on setting up an under ground factory in Jonzac, about 40-50 miles north of Bordeaux, There was a least one train load of tools and parts sent from Paris to other place/s (Tarbes and Barcelona) right at the end. Tarbes was were development of the 12Z was located after the French surrender. Or at least French development.
Post war development assessment is also hard to judge. Birkigt had escaped to Spain for the duration of the war and When he returned to France full time he ran into some unhelpful politicians/officials. One insisted he work on 22 different projects at once. Birkigt retired and moved to Switzerland These changes in head designer/s did not help 12Z development.
The 12Z Ter was supposed to have reached 1300hp at 4000meters with an H-S compresser in using fuel injection.

British factories could be and were bombed. But the likelihood of invasion, over running was pretty unlikely. How much disruption moving the H-S Paris factories would have meant?
As far as building RR or Bristol engines in France? Lets remember that Packard was looking at the Merlin engine in July/Aug of 1940, Contract sighed in Sept 1940. Packard had plant that was building large cars and 41 liter PT boat engines and had a skilled work force. Packard built 45 Merlins in 1941, 26 of them in Dec.
Factory, work force and machine tools would come from where for French production of British designs?

The French would not be stuck in 1940 but some of the French plans were somewhat on the Grandiose side.

About Marc Birkigt, an essential moment in his career took place at the time of the massive nationalizations of the aeronautical industry by the French Front Populaire (end of 1936). Having understood that Hispano-Suiza could not be nationalized, the government imposed the entry of Robert Blum (son of politician Leon Blum) as technical director of Hispano. From then on, Marc Birgikt lost interest in engines and left the management of the company to his son Louis Birkigt, who until then had only worked on the Hispano-Suiza 14AA and 14AB radial engines, which were a failure .

In 1938, the patents for "differential sweeping", which the VK-107 shamelessly copied, were filed by Louis Birkigt. These followed work carried out by Hispano on 6-stroke (six-stroke) engines in which the best sweeping, scavenging and internal cooling was sought.

An attempt to get State control in the capital of Gnome-Rhône at the same time was also a failure.

Certainly, nationalizations caused a "gap" of several years in aeronautical progress, but the policy followed in the aftermath of the 1929 crisis had done nothing to contribute to the modernization of the factories, in particular because of small orders scattered between various manufacturers, which did not encourage them to invest for large series. This caused a form of crisis in tools, the purchases of which (often US or UK) were long neglected by manufacturers due to the delusional policy of the French government.

When France finally became aware of the danger, that is to say in the summer of 1938, it was suddenly realized that the client-state had ruined the industrial-state (Emile Dewoitine : 'L'Etat-client a ruiné l'Etat-patron"). It was then necessary to make up for a delay of several years both in the fields of design and industrialization. Efforts to redress the situation, and in particular to decentralize both the engine and aircraft industries, made a lot of sense. Simply, they were too late !

As for the M-103, VK-105 and VK-107 (and others), we have their manuals here :

Manuals for various Russian and Lend-Lease engines

Manuals for : - Mikulin M-17F M-34RNA, RNB and NB AM-38 and AM-38F AM-42 - Kilmov M-100 M-100A M-100, M-100A, M-103 (2 parts) 12Y-31, M-103A and M-105 (finnish, 2 parts) M-105PA, RA, PF and RF VK-107-A and VK-108 - Shvetsov M-11 M-11 D, L and K ASh-62IR in two parts ASh-82FN - Allison...

ww2aircraft.net

in which we see that the crankshafts of these engines had been extensively modified : large balancing masses, and it seems to me, larger bearings diameter.

 

[Shortround6]

Granted the soviets had problems with engine development in 1941-42

And what happened afterwards? The VK-107 was never brought up to the required condition, the ASh-82 achieved acceptable reliability only in 1945, high-altitude piston engines never reached the serial production, but the Soviets got lucky with the transition to jet engines - they suddenly got access to German and British technology.

I personally am just cutting them some slack in 1941-42 due to the invasion/evacuations/increasing production, etc. slowing down actual development. Maybe it did did and maybe it didn't. But even being generous the Soviets had much of 1943, all of 1944, and most of 1945 to sort out the VK-107. They didn't. Claiming the French could do it in less time in 1940-41 42 seems rather hopeful. Soviets were willing to add substantial weight to the engine to get it to work. French claim to have increased the weight much less. French had super alloys or super heat treating? They were willing to build 50 hour or less (much less?) engines?

I will also note that 100/130 fuel is not magic. The engine has to be strong enough to take the higher pressures in cylinder and had the cooling flow to dissipate the extra heat. It can help but don't expect the changes that RR got with the Merlin and Griffon.

 

[bf109xxl]

But even being generous the Soviets had much of 1943, all of 1944, and most of 1945 to sort out the VK-107.

Then what's left? One controversial achievement in the form of the AM-42? The major problems of the Soviet engine development were a severe lack of experienced engineers and the principle of "quantity over quality". Soviet engine designers were not willing to increase weight, but they were forced to do it because other solutions required too much time from the point of view of the Soviet leadership.

Other modifications are listed but details are not given. You will find statements like "Strengthen crankshaft" repeated a number of times in Kotelnikov's book but I have no idea what the changes were. Beefed up webs? different heat treatment? different steel alloy?

In this reference book you will find a detailed description of the differences for each model from the previous one. The whole book (a pdf file converted from djvu-source) is available here.