Advanced French Fighters vs 1942/1943 contemporaries

[Shortround6]

The problem is that a lot of this is based on estimates or even estimates based on estimates.
Not blaming the French only here.

Curtiss XP-46 first flew Feb 15th 1941, about 8 months after France fell. 2nd prototype with much of the military gear installed was slower than a P-40E that used the same engine despite using about 10% smaller wing, a flush fitting landing gear with full doors and a "better" radiator. It was 55mph slower than the estimates. Curtiss never built a new fighter that equaled the estimates.

The NC.600 and Potez 670 yes, however the Br.700 (and the 697) and the MB.17x all used the 14N, with the R.40 using 12Y engines and the R.41 using 12Z engines. Cross-examining their performance with the Bf 110 C's performance shows quite solid results on the French side.
The NC.600 and Potez 670 (+671) were slower but climbed better while being lighter.

NC 600, wing about 92% the size of a Whirlwind wing. Has a two man crew with a 20mm cannon in a power mounting for the gunner. Has two 680-700hp engines. Supposed to be 23mph slower than a Whirlwind while having engines about 80% as powerful at altitude. Must have the drag of the protruding gun barrels on the Whirlwind.
NC 600 did not have fuel protection or armor or BP glass.

The Potez 670 was pretty much a Potez 630 with the G-H engines swapped for H-S 14AB engines (26.1 liters/1593 cu in another two row radial with no center bearing.
Also lacking protection. Same engines that were used in the Br 691 and were replaced by G-R 14Ms of slightly lower power but greater reliability.
The BR 700 was never completed and is based off of the Br 697 (one built) which is an up engined Br 691. Details are a bit lacking in easily accessed sites/sources.
The MB 170 series was a decent airplane except it had little way forward, It was about the size of a Bf 110 and had about the same power as a mid 1940 Bf 110.

Granted a fighter version could have used a small nose. You have two choices for engines, the G-R 14N or a American R-1830.

The MB.175 was roughly the same in terms of performance but lacked a strong forward armament - something that could be fixed relatively easily.
The Br.697 almost entirely outclasses it with heavier armament, higher top speed and better climb rate, and the Br.700 was expected to be even faster and climb better.
The CAPRA R.40 and R.41 are easily the most standout of these choices, with much higher projected top speeds and climb rates along with strong armaments.

Most addressed above. The Capra R.40 is next to vaporware, Drawings and a mock up.
A plane with a wing about the size of Typhoon, Two HS12Y engines, two man crew, one power turret and a range of over 800 miles on internal fuel. 2 20mm guns, 11 7.5 mg with huge amounts of ammo, Armor for crew and fuel tanks and can average almost 3000fpm climb to 4000 meters using H-S 12Y-51 engines

yes I believe in Unicorns farting rainbows.

 

[Bretoal2]

Heck, I would like to see a squadron of Se.100s landing on a rough airfield
Take bets on how many survive.

The production SE100 was to receive a conventional landing gear.

And PE Mercier had already modified his drawings for 14R cowlings, and Hercules too....

 

[TM06]

The BR 700 was never completed and is based off of the Br 697 (one built) which is an up engined Br 691. Details are a bit lacking in easily accessed sites/sources.

An old suggestion on the War Thunder forum for the Br.697 that I found listed these as sources:
- Les ailes de gloires 1, Les avions d'assaut 690 à 695, Patrick MARCHAND, Junko TAKAMORI
- édition Indochine
- Nowa Technika Wojskowa 2000 Nr-02
- Vers les sommets BREGUET 1919-1939 by Gérard HARTMANN
- Le Fanatique de l'aviation édition Larivière n° 193 & 194
- L'aviation selon Drix: Le Bréguet 690, un avion d'assaut à fort potentiel pour la reconnaissance, meilleur que le très bon Potez 637. (Révisé le 24 / 12 / 2020)
- https://fr.wikipedia.org/wiki/Gnome_et_Rhône_14N
- samolotypolskie.pl - Breguet 690

There's also this source from the former test pilot claiming 650 km/h at 13,200 feet, which is an oddity and might refer to the Br.700 instead since that was supposed to be faster. Take it with a metric tonne of salt.
Icare | 1970-03-01 | Gallica

 

[Shortround6]

I am sorry but I tried
L'aviation selon Drix: Le Bréguet 690, un avion d'assaut à fort potentiel pour la reconnaissance, meilleur que le très bon Potez 637. (Révisé le 24 / 12 / 2020)
in English and it seems to rather fan flavored.

The fore fuselage allowed a more interesting place for an observer.

Are we talking about the same plane? What kind of fore fuselage are you going to have to put on it to have room for an observer.
Lets remember that the engines pictured are 950mm in diameter without the cowls, the BR 690 series are really small airplanes.
The Potez 63.11 that the author of the article complains about used this for nose.

Use the same engines. Observer had enough (more than enough?) room to do his duties. Now graft that onto the BR 693. Or even a bit smaller.
Speculation about using H-S 12X engines instead of the G-R radials is interesting but not helpful regards to actual performance.
One Breguet 690 airframe did have a pair of G-R 14N engines crammed into it. The already mentioned BR 697. Engines were 1290mm in diameter and almost 200kg heavier, each.

I thank you for the link to the French page for the G-R 14N engine which provides a bit more information about the development of the engine. Also reinforces the lack of alternatives, like the H-S radials.

 

[TM06]

I am sorry but I tried
L'aviation selon Drix: Le Bréguet 690, un avion d'assaut à fort potentiel pour la reconnaissance, meilleur que le très bon Potez 637. (Révisé le 24 / 12 / 2020)
in English and it seems to rather fan flavored.

The fore fuselage allowed a more interesting place for an observer.
View attachment 780094



Are we talking about the same plane? What kind of fore fuselage are you going to have to put on it to have room for an observer.
Lets remember that the engines pictured are 950mm in diameter without the cowls, the BR 690 series are really small airplanes.
The Potez 63.11 that the author of the article complains about used this for nose.
View attachment 780095
Use the same engines. Observer had enough (more than enough?) room to do his duties. Now graft that onto the BR 693. Or even a bit smaller.
Speculation about using H-S 12X engines instead of the G-R radials is interesting but not helpful regards to actual performance.
One Breguet 690 airframe did have a pair of G-R 14N engines crammed into it. The already mentioned BR 697. Engines were 1290mm in diameter and almost 200kg heavier, each.

I thank you for the link to the French page for the G-R 14N engine which provides a bit more information about the development of the engine. Also reinforces the lack of alternatives, like the H-S radials.

Yeah that one was highly suspicious to me as well, but I felt I should link all of the sources on that forum post just in case I was missing something.
Regardless, I think the Br.697 would be the strongest candidate for a standard twin-engined fighter / fighter-bomber. Solid speed (570 km/h), a fantastic climb rate for its time (13 m/s), good firepower (4x20 mm Hispano 404's with 90 round drums), based on an existing and already proven airframe (Br.693). A proper rival to the Bf 110.

 

[Bretoal2]

I thank you for the link to the French page for the G-R 14N engine which provides a bit more information about the development of the engine. Also reinforces the lack of alternatives, like the H-S radials.

Thanks, I wrote most of this text.

You may read about HS radials :

Hispano-Suiza 14AB — Wikipédia

fr.wikipedia.org

Hispano-Suiza 14AA — Wikipédia

fr.wikipedia.org

and understand how and why these engines were a failure.

 

[TM06]

Someone brought another theoretical situation to my attention regarding this topic recently. Rather than France not falling in 1940, everything happens normally. France falls, Vichy Regime is put in place, Battle of Britain happens, Hitler turns his attention eastwards, etc.
However, Germany does not place the embargo on France that prevents them from improving their equipment. For historical purposes, let's say that Italy and Japan talk Germany out of it due to them having vested interests in French equipment (Italy used D.520's and Japan wanted SOMUA S.40's). While the ramifications of this are minuscule on the macro scale of the war, they are huge for the micro scale within France.
This gives us a good amount more options in this theoretical; chiefly the Jumo 213 made under Arsenal as the 12H (Post-war designation I think, but Arsenal built Jumo 213's during the war). It also allows them to properly develop the 12Y, 12Z and 14R with little in the way of obstructions. The SE.520Z and VG.39Bis get mass-produced without interference from Germany.
Given how France used a plethora of MG 151/20's post-war for various things, it also opens up the option of those instead of the Hispano 404's should the need arise.

 

[Shortround6]

French had a fetish about small aircraft.
This leads to problems and a lot what if wishful thinking.
The French had one single engine fighter airframe that had any hope of holding a Jumo 213 engine. That was the Bloch 157.
Sticking a 2100lb engine in anything smaller wasn't going to work. Not even sure if it would work in the Bloch 157.
This is like sticking a Chrysler hemi in an MG. It may go fast for a short time in a straight line.

The in-production or soon to be in production French fighters make 109s look big. French went for speed by shrinking wings. Maybe not a bad choice if you are using H-S 12Y engines. Not good choice when you want to use the 12Y-51 and 12Z engines.
The existing French fighters had little or no protection (back of seat plates?). Most did not have much over the average in fuel capacity (D.520 had more than average but could not fight with full tanks) and fitting thirsty engines was going to make the problem worse.

The obstruction involved in the 12Y and 12Z was that the basic engine had outlived it's design limits. There is no magic wand.
The solution, as shown by the Soviets and the Swiss, was to increase the weight of the engine by several hundred pounds.
Which basically means not using much of the existing machinery/tooling to make it and tooling up to make the fuel injection systems in addition to the other changes needed.
This only makes sense for large scale production, not a few dozen or 100 aircraft for Italy.

France, in 1940, may have planned to get 100 octane fuel. France under German control, was not going to get 100 octane fuel.

Japanese can ask for whatever French tanks, artillery, aircraft, engines or anything else. After about mid 1941 they aren't going to get it.
How many Somua S. 40's can you fit on a submarine?
Japanese would have loved the Arsenal VG-33, wing loading like the KI-44 but no butterfly flaps and no leading edge slats like the 109 (or many Soviet fighters).
And that is with 12Y-31 engine.

Basically we are looking at designs for aircraft that didn't even exist on paper in 1940-41 to get useful aircraft in 1943 out of the French.

 

[bf109xxl]

The solution, as shown by the Soviets and the Swiss, was to increase the weight of the engine by several hundred pounds.

Neither the M-107 nor the AM-42 were decisive for the Soviet air power; moreover, they rather detracted from the deployment of the M-71. The war could only be won with the M-105PF2 and AM-38F of about the same weight as their predecessors at the beginning of the war.
Both the Yak-9U and the Il-10 were rather troublesome aircraft with highly disputable value.

 

[TM06]

The French had one single engine fighter airframe that had any hope of holding a Jumo 213 engine. That was the Bloch 157.
Sticking a 2100lb engine in anything smaller wasn't going to work. Not even sure if it would work in the Bloch 157.
This is like sticking a Chrysler hemi in an MG. It may go fast for a short time in a straight line.

There was the VG.60 that had its planning started in 1940, which was initially planned to use the 12Y-51 but swapped to the 213E post-war before its cancellation. With the timeline here, it's possible to have that by 1943 or maybe 1944. The wing armament would likely be different though, not exactly going to get M2 .50's in Vichy France (Perhaps two more cannons instead or maybe MG 131's).

The in-production or soon to be in production French fighters make 109s look big. French went for speed by shrinking wings. Maybe not a bad choice if you are using H-S 12Y engines. Not good choice when you want to use the 12Y-51 and 12Z engines.
The existing French fighters had little or no protection (back of seat plates?).

I'm not finding any wing-related problems to the 12Z-engined planes, the largest concern I could find was the relative unreliability of the engine. They did have plans to strengthen the wings on the D.520 and Arsenal likely would've buffed up the wings as well.
As for armour, they aren't exactly alone on this front. It seems to be more of a general trait of the 1936~1940 single-engined aircraft in Europe to be lightly armoured. Bf 109E / early F, He 112B, Yak-1, Yak-7, LaGG-3, MiG-3, G.50, C.200, C.202, Re.2001, all lacked any meaningful armour. Britain was the exception to its European counterparts, having an actually proper armour layout for both the Hurricane and Spitfire.

How many Somua S. 40's can you fit on a submarine?

Likely quite a few, the base SOMUA S.35 was a pretty small tank (19 tonnes, 5.3mx2.12mx2.62m) and the S.40 wasn't much different - keeping its original width and only being ~400 kg heavier. Hell, you could probably fit a good amount on a large cargo / transport plane.

 

[Shortround6]

Neither the M-107 nor the AM-42 were decisive for the Soviet air power; moreover, they rather detracted from the deployment of the M-71. The war could only be won with the M-105PF2 and AM-38F of about the same weight as their predecessors at the beginning of the war.

And the M-105PF2 was several hundred pounds heavier than the H-S 12Y. Now if you want an even somewhat reliable 1500-1600hp engine (12Z) you have to go other couple hundred pounds.
People want the 1942-43 French aircraft to perform like they had the prototype engines and no increase in weight.

 

[Shortround6]

Likely quite a few, the base SOMUA S.35 was a pretty small tank (19 tonnes, 5.3mx2.12mx2.62m) and the S.40 wasn't much different - keeping its original width and only being ~400 kg heavier. Hell, you could probably fit a good amount on a large cargo / transport plane.

ROFLMAO.
Time travel?
C-5A in WW II?
Let us assume, for arguments sake, you could strip a Somua S.35 down to 15 tons/30,000lbs.

Empty weight........................... 60,252 lb
Max overload............................94,799 lb
Stripped S.35.............................30,000lbs
Difference.....................................4,547lbs
You get to divide that 4,547lb between crew, engine oil, fuel and perhaps radios and guns/ammo.
Lots of luck flying to Japan.
BTW the loaded Me 323 carried 196 imp gallons of fuel for each engine in the wing tanks. Range was 430-465 miles depending on exact model.

A lot of this 1942/43 French stuff seems to based on similar thinking.

There was the VG.60 that had its planning started in 1940, which was initially planned to use the 12Y-51 but swapped to the 213E post-war before its cancellation. With the timeline here, it's possible to have that by 1943 or maybe 1944

I'm not finding any wing-related problems to the 12Z-engined planes, the largest concern I could find was the relative unreliability of the engine. They did have plans to strengthen the wings on the D.520 and Arsenal likely would've buffed up the wings as well.

Ok, no problem taking a fighter with a 150 sq ft wing (empty weight 4519lbs) and yanking the 492kg (1082lb) engine and replacing it with a 920kg (2024lb) engine. Which will not require a heavier propeller, more oil or a larger radiator and more coolant despite making 60% more power. Clever people these Frenchmen.
Yes you can beef up the wing structure (at zero increase in weight?) and increase the load capacity of the landing gear (at zero weight increase?)
Now what happens to wing loading, take-off speed, stalling speed/landing speed and distances with a 16% increase in wing loading what with all the weightless improvements?

BUT WAIT, there is more, order right now (operators are standing by) and we will throw in improved armaments at no additional weight!

BUT WAIT, there is more, order right now (operators are still standing by) and we will throw in improved pilot and fuel tank protection to meet 1943 standards at no additional weight!!!

Yes you can make the wing bigger but then the speed figures don't look so good.
Only the MB 157 of all the French single seat fighters had a wing larger than 17.3 sq m. and that was the MB 155. Next step was the size of a Bf 109 wing.
You can use fighters with a high wing loading, but you need large runways.

Better French aircraft in 1942-43 proponents are throwing in everything short of Ginsu knives and Veg-O-Matics ( I am showing my age).

The French could make better aircraft in 1942-43 but only by starting over in 1940.

 

[TM06]

ROFLMAO.
Time travel?
C-5A in WW II?
Let us assume, for arguments sake, you could strip a Somua S.35 down to 15 tons/30,000lbs.

Empty weight........................... 60,252 lb
Max overload............................94,799 lb
Stripped S.35.............................30,000lbs
Difference.....................................4,547lbs
You get to divide that 4,547lb between crew, engine oil, fuel and perhaps radios and guns/ammo.
Lots of luck flying to Japan.
BTW the loaded Me 323 carried 196 imp gallons of fuel for each engine in the wing tanks. Range was 430-465 miles depending on exact model.

Didn't know any of that, guess my perception of "light" is a bit muddled there as a fan of heavy armoured vehicles. I suppose something like the M22 Locust would be more around the weight class required for that kind of transport. My point about the submarines still stands though.

Ok, no problem taking a fighter with a 150 sq ft wing (empty weight 4519lbs) and yanking the 492kg (1082lb) engine and replacing it with a 920kg (2024lb) engine. Which will not require a heavier propeller, more oil or a larger radiator and more coolant despite making 60% more power. Clever people these Frenchmen.
Yes you can beef up the wing structure (at zero increase in weight?) and increase the load capacity of the landing gear (at zero weight increase?)
Now what happens to wing loading, take-off speed, stalling speed/landing speed and distances with a 16% increase in wing loading what with all the weightless improvements?

There definitely were changes like the ones you described.
For the 12Z Dewoitines, they fitted a larger, more efficient 3.17 m Ratier 3-bladed propeller. The longer nose designed to hold the 12Z had larger radiators and increased water coolant along with redesigned exhaust pipes.
And the weight did increase as a result of this, according to Danel and Cuny the SE.520Z had a take-off weight of 2,780 kg / 6,128 lbs and a maximum take-off weight of 3,178 kg / 7,006 lbs. The M.520T - which had more in common with the D.55x than the D.520 - had a total weight of 3,337 kg / 7,356 lbs.
There's an excellent post on the old War Thunder forums by an old acquaintance of mine named Lucky_B that has a lot of information on the D.520 family, and Is my go-to for many things relating to said aircraft.
You can find their write-up of the D.55x series here, and their overview of the D.520 family here.

 

[Shortround6]

I suppose something like the M22 Locust would be more around the weight class required for that kind of transport.

Slung under a C-54. Turret went inside. Yes the Hamilcar glider could hold one but that is not long distance proposition.

The Japanese had thousands of little tanks with 37mm guns already.
And the Japanese already had a tank that was better than the Somua.

the 57mm gun was only good for HE and very light armor but at least in had a 2 man turret.
Spring of 1942 they stuck a high velocity 47mm gun in the turret. They built over 2000 of these combined.

My point about the submarines still stands though

A few dozen Somua tanks wouldn't have changed a thing. Especially bringing them in 2-3 tanks at time by submarine from France.
You don't cut holes in pressure hulls for cargo holds.
You can put large cannisters on the deck but that has problems. Too many buoyant canisters and you no longer have a submarine.
Keeping the Somua's exposed to sea water for a few month is probably not a good idea. Major overhaul needed upon delivery.
Some of the large Japanese subs could hold 2-3 landing craft or a couple of tracked landing craft.

This could be sealed up, at least for short periods of time. Ocean voyage halfway round the world maybe another story. Also note the even this 10 year old sub was about twice the displacement of any German WW II sub.


Just about any WW II fighter increased in weight if it was kept in production and modified. Runways did get longer. But many times the increases in weight were not compensated by the increased power as far as climb went.
Now for comparison.
SE. 520Z take off weight 6128lbs equals 35.6lbs per sq ft and if we multiply that by 232 sq ft we get about 8260lbs for a P-40.
The post war D. 520T if it really had a 172sq ft wing and weighed 7356lbs would equal a P-40 at a weight of 9,922lbs.
P-40s could and did take off with weights like that. Very large ferry tanks or very large bomb loads. They also needed huge runways.
That is a real problem with small wing fighters, they don't have a lot of room to grow.
You can use power to get a heavy plane off the ground. You can use trick flaps to get them back down but things get dicey and while a plane may go fast, maneuvering like a P-40 with three 500lb bombs underneath is not what most pilots want to do.
The French only bought one of these for trials but 12 more supposed to have been on order.

C.A.O. 200. Modified it is supposed to have hit 342mph, Version with 12Y-51 was estimated at 380mph.
Wing was only 143 sq ft. Leading edge slats were linked to the flaps and opened automatically when flaps deployed a certain amount. Early version was 5500lbs.
Hurricane had almost twice the wing area. Hurricane was slow and was never going to be fast but it could get into and out of small areas and if you had a medium airfield you could hang that pair of 500lbs bombs under it. It would also hold four 20mm cannon. Part was because of the Merlin, part was because the big wing, which slowed it down, gave plenty of lift to carry larger loads.
None of the H-S powered fighters were going to be much good as multi-role aircraft.
And the small twin engine tactical French aircraft were a sick joke.

 

[TM06]

-Somua talk-

The line about the S.40 was more of a throwaway statement to help create a scenario, it just popped into my head as I remembered that Japan was interested in them. While I love a good discussion about underrated tanks, that was not the purpose of my claim.

None of the H-S powered fighters were going to be much good as multi-role aircraft.

To be fair, they don't really need to be multi-role aircraft, they can just be fighters. The MB.157 would be the most likely candidate for that role, and the VB.10 was able to fit 2 x 500 kg bombs under its wings. The 12Z fighters could be the 109 of France and the MB.157 could be the 190 of France (ignore the existence of the NC.900).

 

[bf109xxl]

Time travel?

Well, okay, you need to double the size. Or quadruple it, what's the difference? But it's a good idea, isn't it?
PS. Just kidding.

 

[yulzari]

View attachment 780783
Slung under a C-54. Turret went inside. Yes the Hamilcar glider could hold one but that is not long distance proposition.
View attachment 780784
The Japanese had thousands of little tanks with 37mm guns already.
And the Japanese already had a tank that was better than the Somua.
View attachment 780785
the 57mm gun was only good for HE and very light armor but at least in had a 2 man turret.
Spring of 1942 they stuck a high velocity 47mm gun in the turret. They built over 2000 of these combined.

A few dozen Somua tanks wouldn't have changed a thing. Especially bringing them in 2-3 tanks at time by submarine from France.
You don't cut holes in pressure hulls for cargo holds.
You can put large cannisters on the deck but that has problems. Too many buoyant canisters and you no longer have a submarine.
Keeping the Somua's exposed to sea water for a few month is probably not a good idea. Major overhaul needed upon delivery.
Some of the large Japanese subs could hold 2-3 landing craft or a couple of tracked landing craft.
View attachment 780786
This could be sealed up, at least for short periods of time. Ocean voyage halfway round the world maybe another story. Also note the even this 10 year old sub was about twice the displacement of any German WW II sub.


Just about any WW II fighter increased in weight if it was kept in production and modified. Runways did get longer. But many times the increases in weight were not compensated by the increased power as far as climb went.
Now for comparison.
SE. 520Z take off weight 6128lbs equals 35.6lbs per sq ft and if we multiply that by 232 sq ft we get about 8260lbs for a P-40.
The post war D. 520T if it really had a 172sq ft wing and weighed 7356lbs would equal a P-40 at a weight of 9,922lbs.
P-40s could and did take off with weights like that. Very large ferry tanks or very large bomb loads. They also needed huge runways.
That is a real problem with small wing fighters, they don't have a lot of room to grow.
You can use power to get a heavy plane off the ground. You can use trick flaps to get them back down but things get dicey and while a plane may go fast, maneuvering like a P-40 with three 500lb bombs underneath is not what most pilots want to do.
The French only bought one of these for trials but 12 more supposed to have been on order.
View attachment 780787
C.A.O. 200. Modified it is supposed to have hit 342mph, Version with 12Y-51 was estimated at 380mph.
Wing was only 143 sq ft. Leading edge slats were linked to the flaps and opened automatically when flaps deployed a certain amount. Early version was 5500lbs.
Hurricane had almost twice the wing area. Hurricane was slow and was never going to be fast but it could get into and out of small areas and if you had a medium airfield you could hang that pair of 500lbs bombs under it. It would also hold four 20mm cannon. Part was because of the Merlin, part was because the big wing, which slowed it down, gave plenty of lift to carry larger loads.
None of the H-S powered fighters were going to be much good as multi-role aircraft.
And the small twin engine tactical French aircraft were a sick joke.

Getting in and out of small airfields can determine what you use rather than the performance in the air. It was the small fields which caused the RAF to take Gladiators with them in the BoF. and allowed Gladiators to be based in Plymouth during the BoB.

 

[Shortround6]

To be fair, they don't really need to be multi-role aircraft, they can just be fighters. The MB.157 would be the most likely candidate for that role, and the VB.10 was able to fit 2 x 500 kg bombs under its wings. The 12Z fighters could be the 109 of France and the MB.157 could be the 190 of France

Maybe the MB 157 shows up (squadron service, more than one squadron) in 1943.
The VB.10 was pretty much vaporware. The problem with most unconventional aircraft was the details. The "simple, just stick two normal engines here and here" was often not so simple.
Things like shafting, couplings, and trying to get propellers to play well together often sucked up an inordinate amount of time/effort. By the time this mechanical stuff was sorted out, more conventional engines/propellers were offering more power/thrust than the unconventional solution/s. Sometimes they had to bet on both horses but with history the conventional stuff almost always won.

The Hispano V-12s were always behind the DB601 in timing. The French were trying to get the 12Y-51 into production in May/June of 1940. Prototypes were flown, 1000hp at 3260meters. Germans were using, in squadron service, in late 1939 and early 1940 DB engines that could make 1000hp at 3700-4100 meters. I am using the 30 minute rating for the Germans. July 1940 saw one Group of 109s (3 squadrons of 12 planes each) equipped with DB 601Ns. About 500 in service by Jan 1941 1050PS at 4850meters for the 30 minute rating, most were in service with Bf 110s.
109F-2 with DB 601Ns were supposed to good for 373mph. The French need more than 12Y-51 engines. They need some sort of 12Z engine. Now what kind of 12Z engine are they going to get in 1941? One with carbs or fuel injection? one with a max rpm of 2600? of something other? What kind of supercharger? What kind of reliability?

By March of 1941 37 Do 217s had been built, many of them with BMW 801 engines. The G-R 14R may have been close to the BMW 801 engine but it was running late, not counting the
invasion.

Maybe another thread but the French tactical aircraft (mostly very small, light twins) sucked. Granted a lot of other nations early tactical aircraft sucked. Some of those countries could draft their single engine fighters to do tactical aircraft (strike) duties. The French have a hard time with that option/path.

 

[TM06]

They need some sort of 12Z engine. Now what kind of 12Z engine are they going to get in 1941? One with carbs or fuel injection? one with a max rpm of 2600? of something other? What kind of supercharger? What kind of reliability?

From what I could glean about the 12Z, the 12ZTer - the version intended for mass production - had fuel injection, while the 12Z-01 and 12ZBis had carburettors.
Documents on the pre-war 12Z are scarce, but the 12Z-17 ran on 2,400 rpm nominally, 2,650 rpm for take-off and 2,700 rpm for short-term emergency power (not WEP, basically over-rev and overboost). The numbers for the 12ZTer would likely be similar, as the 12ZTer could be built to the same standard as the 12Z-17. Those engines were designated as 12Z-M apparently.

As for the supercharger, the Szydlowsky-Planiol single-speed supercharger is the most likely given that they were already taking steps to introduce it for the 12Y-51 and 12Z. However the 12Z-1 (different than the initial 12Z-01 prototype) planned for the production models of the SE.520Z was fitted with a two-speed Hispano-Suiza No.3bis supercharger - with its counterpart the 12Z-11 being fitted with a two-speed Szydlowsky-Planiol supercharger. I think that the Szydlowsky-Planiol supercharger would likely be the main choice for most if not all versions of the engine from a military standpoint, most of the things I've read about the HS superchargers are not positive. However I should note that Wikipedia lists a variant called the 12Z-B that was fitted with a two-stage intercooled supercharger made by the Spanish division of HS in 1944.

Reliability is a tough call. Post-war reports of the 12Z note its unreliability, but I theorise that this is likely due to them not being able to fix those problems as a result of the ban on the engine. One of the major things I learned while being taught about racing engines is that no engine starts off reliable, they become reliable through development, and I imagine this would also ring true for aircraft engines. They wouldn't be bulletproof or anything, but I could foresee a relatively average reliability figure for the engine had its development not been cut short.

 

[Shortround6]

The Problem with the H-S engine is that was trying to up date a late 20s engine.
Throwing a supercharger on an existing engine may not have been the best way to improve power in the long term.
Even in 1933-34-35 the Soviets were down grading the H-S engines to about 750hp in the interests of longevity.
And that was after they got H-S to make some improvements. Having a test engine crankshaft fail at hour 11 of a 100 hour test was not a good sign.
The Supercharged engine will certainly make more power. How long it lasts is the other question.

The Swiss had quite a bit of trouble with their 12Y-51s at 2500rpm which prompted them to develop their YS series. Crankshaft gained about 30kg among other things.

Who had what prototype is one thing. Ability to build a hundred engines a month (or 1000 or 5000) is something else.
Many engine companies bought in (outside suppliers) things like ignition components, carburetors and fuel injectors and other "stuff".
Not saying the French could not get there but switching from carbs to fuel injection was a major undertaking. A lot more fine tolerance machining.
Swiss in 1947 were using injectors that operated at 2850psi at the cylinders.

RR designed the two piece cylinder blocks. Packard got them into production first because they didn't have any production tooling for the old blocks.
RR in England to wait to change the tooling until either demand dropped or new factory came on line give them some slack to allow change over.
IN the US fuel injection of the German style (direct injection into the cylinders) or even injectors for each cylinder right in front of the intake valves didn't happen on production engines until the Wright engines in later B-29s to control mixture problems and engine fires.
Swiping a few fuel injection systems from crashed German planes for testing/prototypes is one thing. Building hundreds per month may take a while.

there seem to have been license problems (?) with the Szydlowsky-Planiol supercharger. Or manufacturing/cost? Several models of H-S engines seem to swap back and forth.
The Szydlowsky-Planiol supercharger never caught on in the US.
I believe the Fairchild company tried to use it on their Ranger V-12 engine for use in Bell P-77 light fighter. Like a lot of other Bell Projects what was promised fell short of what they could deliver. The two P-77s that flew were never fitted the "special" Ranger V-12s with the Szydlowsky-Planiol superchargers although they were advertised post war and were supposed to have been fitted or proposed for the NA AT-6E.
The Szydlowsky-Planiol superchargers may well have worked better than the H-S superchargers. I am not sure they worked as claimed/advertised.
That or nobody wanted to pay for the licenses in Britain of the US.