Advanced French Fighters vs 1942/1943 contemporaries (2 Viewers)

[Elan Vital]

Turns out the archives I was looking for on 30mm MAT and 33mm APX aircraft autocannons were solely trials reports of their respective ammunition (with plans for the 30mm). The MAT appears to have been designed around a 1000 m/s muzzle velocity at less than 330 MPa of service pressure, with a 32/33 gram payload. The propellant charge is a maximum of 185 grams, for a 455g projectile.

What's notable is that the story of the 30mm MAT goes at least as far as June 1937.

 

[tomo pauk]

Turns out the archives I was looking for on 30mm MAT and 33mm APX aircraft autocannons were solely trials reports of their respective ammunition (with plans for the 30mm). The MAT appears to have been designed around a 1000 m/s muzzle velocity at less than 330 MPa of service pressure, with a 32/33 gram payload. The propellant charge is a maximum of 185 grams, for a 455g projectile.

Beast of a cannon - ballpark of the Mk 303, or the later M 53/59/70 that I served on.

 

[TM06]

Turns out the archives I was looking for on 30mm MAT and 33mm APX aircraft autocannons were solely trials reports of their respective ammunition (with plans for the 30mm). The MAT appears to have been designed around a 1000 m/s muzzle velocity at less than 330 MPa of service pressure, with a 32/33 gram payload. The propellant charge is a maximum of 185 grams, for a 455g projectile.

What's notable is that the story of the 30mm MAT goes at least as far as June 1937.

Beast of a cannon - ballpark of the Mk 303, or the later M 53/59/70 that I served on.

Raises the question of if aircraft like the D.520 and VG.33 would be able to handle that kind of power and recoil. Closest contemporary would be the NS-37 I think? And if memory serves, the Yak-9T could actually stall itself by firing its NS-37 for too long.

 

[tomo pauk]

Raises the question of if aircraft like the D.520 and VG.33 would be able to handle that kind of power and recoil. Closest contemporary would be the NS-37 I think? And if memory serves, the Yak-9T could actually stall itself by firing its NS-37 for too long.

With muzzle velocities in the ballpark, the recoil momentum is proportional to the shell weight. We have 735g or 760g for the Soviet gun, while 455 was stipulated for the French gun. IOW, a lot less of a recoil per shell fired for the French gun, so the French fighters should not have problems with the recoil. Especially if a decent muzzle brake is installed.

I don't believe that the long bursts of the NS-37 would've stalled the Soviet fighters.

 

[Shortround6]

I don't believe that the long bursts of the NS-37 would've stalled the Soviet fighters.

It might be possible.
A lot would depend on the speed and attitude (bank) of the aircraft to begin with.

I have not done the math but I am thinking about firing at low speed like around 300kph and with a fair amount of bank, like over 45 degrees.
Firing at 500kph and with somewhat level wings means you have to reduce the speed an awful lot.

Edit. Tomo, What held the 30mm AA gun vehicles you served on in place?
Chocks/wedges or vehicle brakes or???
The gun mount you used fired about 4 times faster than the soviet gun and should generate a lot more recoil. Granted it was lot heavier than a Yak 9T but one might think that if there was anything to this recoil thing the vehicle might have moved on slippery ground? Wet or frozen if the guns were lined up with the wheels.

 

[tomo pauk]

Edit. Tomo, What held the 30mm AA gun vehicles you served on in place?
Chocks/wedges or vehicle brakes or???
The gun mount you used fired about 4 times faster than the soviet gun and should generate a lot more recoil. Granted it was lot heavier than a Yak 9T but one might think that if there was anything to this recoil thing the vehicle might have moved on slippery ground? Wet or frozen if the guns were lined up with the wheels.

The 10 ton combat weight of the vehicle, ability to block the suspension, parking brake, and muzzle brakes. Gun itself being heavy also helped out, almost 280 kg empty each.
Note that firing on the move was also allowed (but at the slow speed), obviously without the parking brake and with suspension not being blocked. One can just guess how inaccurate the gun (without any means of stabilization) will be in this case.

Note that gun was dis-mountable/mountable by the crew, via the help of the onboard winch and the pair of sleds.

 

[Shortround6]

And the big question of the day is......................................

Did firing the guns in line with cab while moving slowly slow it down or when firing the guns over the rear end speed it up any

My guess is that the crew was bouncing around too much to notice.

 

[tomo pauk]

Did firing the guns in line with cab while moving slowly slow it down or when firing the guns over the rear end speed it up any

I was there just when the guns were firing while the vehicle was standing still, so I cannot comment on that.
IMO, it was too much of weight for the guns to seriously disturb either the direction or speed of the vehicle.

My guess is that the crew was bouncing around too much to notice.

Agreed pretty much.

 

[Shortround6]

I got little carried away but some people expect a single slow firing cannon to stop or significantly slow down a 400kph 3 ton aircraft with a "long" burst. Standard burst about 3 rounds?

I think you can find such stories about recoil causing the plane to stall going back to WW I

454gram projectile being fired at 150rpm. Any recorded instance of these stalling and crashing?

 

[bf109xxl]

I don't believe that the long bursts of the NS-37 would've stalled the Soviet fighters.

And in vain. The test reports for the LaGG-3 with Sh-37 explicitly state that the length of the burst should not exceed five shots, otherwise the airplane loses speed too much.
IIRC, similar statements can be found in the test reports of the Yak-9T and Il-2 with 37mm guns. But an even bigger problem was the instability when firing - it was possible to fire a burst of no more than 2-3 rounds more or less accurately.

 

[Steamed_Banana]

Forgive me if I missed this, I skimmed through all 23 pages of this very interesting discussion thread, but I didn't see any mention of the Doflug 3802.

This was a Swiss (Swiss branch of Dornier) made improved version of the MS 406 / 410.

Top speed was 391 mph, ceiling 30,000', first flight was in Sept 1944. It used a Saurer YS-2 (a local copy of the HS 12Y-51) producing 1,250 HP with a four-bladed constant speed propeller, and was armed with one 20mm and 4 30 caliber machine guns, or three 20mm cannon (one in the hub and one in each wing). A postwar further improvement called the D-3803 had a bubble canopy and an improved Saurer YS-3 engine making 1,430 HP and achieving 423 mph at 7,000 meters / 22,966 feet. This came out postwar when the US was giving away P-51 Mustangs to pretty much anybody for almost nothing, so it was hard to justify a domestic aircraft production and production was halted.

Only a dozen of these were made, but these were apparently flying with a Swiss squadron until 1956. Or anyway, assigned to that squadron. The significance of this to me is not so much whatever the Swiss aircraft did, but as a kind of proof of concept for both the airplane and the ultimate potential of the 12Y engine. Interestingly, while there isn't a Wikipedia page for this interesting aircraft,there is one for Sauer engine company, with a section about their airplane engines, here. Apparently the engine was also used on the kind of weird looking Swiss 'attack' plane, the EKW C-36

The Swiss apparently had a lot of trouble with the their license-built 12Y-51s, which suffered many bearing failures. From what I understand, they started working on the improved YS-2 in 1942, and by 1944 they had resolved the production / reliability problems with the 12Y-51s, and the new YS-2 had arrived. This seems to have been fairly reliable (though i say this admittedly on very thin evidence either way, just that the planes using it kept flying for a long time and I didn't see any mention of engine problems). I don't have any data on what this meant vis a vis weight of the engine etc. either, but the performance of each plane was fairly good relative to the power of the engine (391 mph with 1,250 hp and 423 mph with 1,430 hp). That's actually very good by WW2 fighter standards overall, I'd say.


So this tells us two things - that a very small Swiss company was able to make both the 12Y and the Morane 406/410 airframe into more viable versions. It took them two years to do this, so the big question is, how long would this have taken France if France had somehow survived for a while after 1940. Well, Switzerland is a sophisticated, highly advanced country with a strong armaments industry. But they didn't really have an aviation industry at all, and much of the country was still rural. Swiss population in 1941 was 4.2 million, about half living in cities. France had 42 million people in 1940, almost exactly ten times the population of Switzerland. They had an advanced (if at the time, somewhat chaotic) aviation industry which had been going strong since before WW1. French aviation indsutry was organized into 6 nationalized groups in 1940.

Hispano-Suiza was a well developed automobile, gun (autocannon) and aviation engine company. The French government owned a controlling share (51%) since 1937.

I think it's a cinch that an improved airframe could have been built. Something like the 3802 seems not only viable even in 1940, the VG-33 / 39 actually looks like a better aiframe, and was already in production just not in time to get into service. Forty of them were literally at aerodromes, another 160 were in the factories waiting on propellers and guns to be put in. These were using the 12Y-31 with 860 hp, and with that made 344 mph. The French built a proptotype of the VG-36 with a 12Y-45 producing 1,000 hp and flying. The VG 39 was supposed to use the 12Y-89 with 1,200 hp, which apparently also flew as a prototype making 388 mph. The final production version was supposed to be VG-39bis with the 12YZ-17, which I believe some folks think was vaporware, but was supposed to produce 1,600 hp.

Whether the 12Z was real within the timeframe of WW2 or not, it seems like something like the 12Y-51 with 1,250 hp was definitely possible. The Swiss were making them under license in 1941, albeit having trouble with the bearings. But with that engine it seems like the VG-39 would be approaching 390 mph, and thus at least possible it could have been a very viable fighter for say 1941. Nor was this the only option. The most potent engine fitted to the D.520 was the 12Y-49, producing 950 hp for takeoff only, I believe 910 after that. It managed 350 mph (allegedly). So if you could fit a 1,250 hp engine in a D.520 I think you might have another viable fighter on your hands. Unimproved 1940 vintage D.520s were actually still aquitting themselves fairly well as late as 1943.

I guess the real question is how quickly could Hispano-Suiza improve / debug their 12Y-51 or 89, or make the 12Z work. The 12Z was tested on both MS .410 and D.520 (as MS.450 and D.524). The postwar Hispano 12Z was apparently not very reliable either, but it's unlikely that it received the same kind of priority that it would have in wartime.

Bottom line is that it seems to me that a viable fighter could have been made. The engine is a question mark, and none of the Hispano versions had two speed or two stage engines. It's possible Merling engines could have been imported but that starts to feel a bit far-fetched. I could however envision a VG 39 or D.524 flying by some time in 1941 with a single speed but powerful Hispano 12Z, good armament with 3 x 20mm cannons, good rate of climb and overall agility as these planes seemed to have. I think that would be competitive.

 

[Shortround6]

The Swiss apparently had a lot of trouble with the their license-built 12Y-51s, which suffered many bearing failures. From what I understand, they started working on the improved YS-2 in 1942, and by 1944 they had resolved the production / reliability problems with the 12Y-51s, and the new YS-2 had arrived. This seems to have been fairly reliable (though i say this admittedly on very thin evidence either way, just that the planes using it kept flying for a long time and I didn't see any mention of engine problems). I don't have any data on what this meant vis a vis weight of the engine etc. either, but the performance of each plane was fairly good relative to the power of the engine (391 mph with 1,250 hp and 423 mph with 1,430 hp). That's actually very good by WW2 fighter standards overall, I'd say.

Well, it has been noted in several places that crankshaft in the YS-2 was about 30kg heavier than the Crankshaft in the H-S Y engine. And we have the fact that the YS-2 used four valve heads and not the 2 valve heads of the 12Y-51. According to some sources the YS-2 wound up gaining about 180kg total. or about 39% weight gain?
A lot more changes that a little "tweaking" and slapping a fuel injection set up on the engine.
You can do a lot with the H-S 12Y engine if throw away everything except the bore and stroke

The D-3802 is another case of it "it sorts of looks like a MS 406 if I squint hard". Granted a lot planes changed engines and radiators. The D-3802 changed the form of construction in the fuselage and tail and gained about 1 meter in length. When you stick a heavier, more powerful engine with a 4 bladed prop in the nose you often have to make the tail longer/bigger or both. Swiss may have squeezed in a trip to a wind tunnel?

The main problem for improved HS engines is that the basic engine had reached the end of the line. The bridge was out and the brakes had failed and the engineer was taking a nap.
The Post war Spanish 12Z-89 had gained about 145-150kg.
You could make a better 12Y engine, you just needed a lot testing and you needed to build a lot new tooling for the factory. Swiss were masters of machine tool production. They were also not building more than a few engines a month. French needed hundreds per month.

 

[ThomasP]

Do we have any info on what fuel grade the YS-2 and YS-3 engines were using in order to achieve their respective BHP? I have no idea what fuel grades the Swiss had access to.

 

[Shortround6]

Do we have any info on what fuel grade the YS-2 and YS-3 engines were using in order to achieve their respective BHP? I have no idea what fuel grades the Swiss had access to.

Nothing good. Various editions of Wilkson's from post war list different fuels. But Wilkson is not reliable. Or the sources he was using changed the fuel listed to what was available.
91/98 was common post war fuel replacing 91 octane and sometimes either 93 or 96 octane depending on country.
The YS-2 and YS-3 seem to have used fuels in the 90s. Maybe they got 100/130 later in life?
There was a YS-4 but I don't know if it went anywhere. Higher RPM and variable speed drive on the supercharger (plus new supercharger?) and that is listed as 100/130 fuel but who knows?

 

[Steamed_Banana]

Well, it has been noted in several places that crankshaft in the YS-2 was about 30kg heavier than the Crankshaft in the H-S Y engine. And we have the fact that the YS-2 used four valve heads and not the 2 valve heads of the 12Y-51. According to some sources the YS-2 wound up gaining about 180kg total. or about 39% weight gain?
A lot more changes that a little "tweaking" and slapping a fuel injection set up on the engine.
You can do a lot with the H-S 12Y engine if throw away everything except the bore and stroke

That is indeed significant, but the Swiss achieved it in 2 years, and for all their skill, there just aren't that many Swiss (and even fewer as a percentage of their industrial base, working on aircraft engines).

It seems like the 12Y varied a fair bit in weight, with early versions weighing around 415-440 kg. The 12Y-31 in the original MS.406 weighed 468 Kg, and the 12Y-51 which was the original basis for the YS-2, weighted 492 kg. So which of these are comparing the YS-2 with? I couldn't find the weight for the YS listed.

The 12Z was apparently a whole lot heavier than any 12Y, at 620kg according to the Wiki. That's 128 kg heavier than the 12Y-51. But the important bit is that the 12Z was already at least at a late enough of a stage to fly prototype aircraft with.

The D-3802 is another case of it "it sorts of looks like a MS 406 if I squint hard". Granted a lot planes changed engines and radiators. The D-3802 changed the form of construction in the fuselage and tail and gained about 1 meter in length. When you stick a heavier, more powerful engine with a 4 bladed prop in the nose you often have to make the tail longer/bigger or both. Swiss may have squeezed in a trip to a wind tunnel?

Lengthening aircraft wasn't all that unusual. They lengthened the P-40 by about a meter in 1942 which didn't slow production much and didn't seem to cause any problems - to the contrary. I agree the Doflug is definitely a good bit thinner and more streamlined than the MS 406, in addition to the different (improved) radiator system. And that is a bigger change. But I don't think the Swiss had to go to the wind tunnel because the French had already done this with their MS 450 (which looks a lot more like the Doflug 3802, as it was in fact the basis for the new airframe) and they also did the same with the prototype Dewoitine D.524 (using the 12Z-89ter rated at 1160 hp and making 382 mph) and the Arsenal VG.39bis using the 12Z-17 rated at 1300 hp, or 1500 hp at sea level - 'overboost' making 388 mph at the lower HP rating, apparently). So I think they were in fact ready to make all these changes quite swiftly, at least for prototypes. Getting them into production is another matter but more on that in a second.

The MS 450, as tested in 1939, made 348 mph using a 12Y-51 engine producing either 1,100 or 1050 hp (I got different numbers, higher power was probably due to boost).

The Doflug 3802 was not, in other words, really a Swiss invention at all, it was in fact a direct continuation of this branch of the Morane series, and was also known as the MS.540.

The French apparently had 100/130 fuel by the way, I don't know if that was coming from the British or what.

The main problem for improved HS engines is that the basic engine had reached the end of the line. The bridge was out and the brakes had failed and the engineer was taking a nap.
The Post war Spanish 12Z-89 had gained about 145-150kg.
You could make a better 12Y engine, you just needed a lot testing and you needed to build a lot new tooling for the factory. Swiss were masters of machine tool production. They were also not building more than a few engines a month. French needed hundreds per month.

France had a vastly larger and more developed aviation industry, population, much more resources in terms of raw materials, power etc., better available fuel etc.

There is still a thorny question of how long would it take the French to make the equivalent improvement the Swiss did with the YS-2 and YS-3 (apparently they also eventually made a YS-4 with a variable speed supercharger as well, though by that time we are getting into the turboprop era).

I'm tempted to assume that if the Swiss could do it in 2 years with 1/10th the population, and probably 1/20th the size and experience of their aviation industry, not to mention that France and Hispano-Suiza were already geared up and in the midst of exactly the kind of testing needed the French could do this in a few months. They did already have two versions of the 12Z in testing, the 12Z-89ter and the 12Z-17. But I know it's not that simple.

They did also do a test with the Arsenal VG-30 series, on the VG-31 with an Allison V-1710C-15 in 1939, which was apparently very successful, and that is a 633 kg engine. This was before the VG-33 ever flew.

The other question is how long would it take to get these into production. The VG-30 series flew first as an early prototype in 1938, the VG 33 flew in April 1939, and they got it into production rather swiftly about a year later, with 40 production models delivered by April 1940, and another 160 'near complete', out of the initial order of 1,000. Unfortunately that was too late of course.

But even as-is, without any engine improvements, but using the best available mark of the 12Y, the VG-33/39 looks fairly competitive. As does the D.520. And probably the MS.450 / 540 / Doflug 3802 as well, which would have been available within a few months.

One final comment on production. France, due to internal divisions etc., was very late to prepare adequately for WW2 and this was as true in the aviation industry as anywhere else. But by 1940, they had indeed gotten the message, and production problems were largely eliminated. Another promising late 30s design, the rather advanced LeO 451 twin engined bomber, (300 mph, 1800 mile range, 3,400 lb max bomb load) is a good example of this. The SNCASE plant produced 200 during the 45 days leading up to the armistice, which is a rate of 4-5 per day.

SNCASE was also one of the factories making the Dewoitine D.520

The Arsenal VG 30 series was also designed for rapid production, being made mostly of wood like a lot of Soviet fighters.

So given that they had a viable design to build, and production was already ramped up as it was with the Arsenal and the D.520, it was really just a matter of a few more months to deliver aircraft and let the pilots learn the new types, address minor teething issues, and develop some tactics, and they would have had a much stronger fighter force. Both of these (and the MS 540, arguably) had the potential to become much more formidable fighters and should have remained competitive with German types (again, arguably) through 1941.

Ultimately the question here does come down to engines. I don't really have any benchmark for how quickly HS could ramp up production, but the 12Y-51 and other later mark HS 12 engines were in demand and production was not keeping up, many of the unfinished VG 33 and D.520 were waiting for engines. So that is the big question, to me.

 

[Steamed_Banana]

So to continue the thought experiment here a bit, to it's logical conclusion...

If, let's say, France somehow survived the initial onslaught by whatever means you want to think of, and achieved a kind of stalemate for lets say six months,

you will have by then very competitive fighters, arguably, such as VG 39bis and D.524 and probably MS 540 too. MS 406 was actually a pretty agile fighter and did well for the Finns, it was just too slow. The 540, VG 39 and D.524 are all going to be in the 360-390 mph range, they are all agile with fairly low wing loading, climb pretty well, have armor and self sealing fuel tanks, have decent range, and good to very good armament. 20mm hub cannon is a lethal weapon for air to air combat. Later versions of these fighters also had two 20mm wing guns so that becomes heavy firepower indeed.

Arsenal VG 39 - 388 mph at 5800 m / 19k ', range 750 miles, armament 1 x 20mm 4 x 7.5mm machine guns, wing loading 36 lbs/sq ft (HS 12Y-51 Engine)
Arsenal VG 39bis - 418 mph* at 7000 m /22k ' (military power) 446 mph* (WEP), armament 3 x 20mm machine guns (HS 12Z-17 Engine)
Dewoitine D.524 - 382 mph* range 780 miles, wing loading 34 lbs / sq ft, armament 1 x 20mm and 4 x 7.5mm machine guns (HS 12Z-89ter Engine)
Morane MS 540 - 391 mph, range 400 miles, wing loading 19 lbs / sq ft, armament 1 x 20mm 4 x 7.5mm machine guns (YS-2 engine, Doflug 3802 numbers)

Climb rates for all three seem to be around 2800 fpm initial for the early / 1940 version (no improved engines) a bit over 3,000 fpm initial for the bigger engines.

And let's not forget the LeO 451 bomber (308 mph, 1800 mile range and 3400 lb max bomb load, and 20mm defensive gun in 1940), the Breguet 693 attack plane (300 mph, 840 mile range, 20mm cannon armed, in 1940), and Bloch MB 174 recon plane (330 mph, 290 mph cruise speed, 1000 mile range in 1940)**

We can also add to this a larger number of P-36 / Hawk 75 (the most successful fighter for the French during the actual Battle of France), probably early P-40 / Tomahawk type fighters, with improved Tomahawk and maybe P-40D / Kittyhawk type by maybe mid 1941, plus early Martlet / Wildcat fighters (Grumman G-36); A-20 Boston (340 mph), Martin 167 Maryland (300 mph, 1,200 lbs bombs and 1300 mile range) and Martin 187 Baltimore (300 mph, 2,000 lbs bombs,, 980 mile range) type fast bombers, SBD dive bombers (as we know, accurate but vulnerable), maybe even a few early P-38s. All of this gives them some Tactical and Operational striking power. The French may have had some other important US or British types on order that I forgot or wasn't aware of.

Plus the British will almost certainly be helping with their Spit Mk I and II, Hurricane Mk 1 and II, and eventually also Spit Mk V. Maybe a few Whirlwinds and Beaufighters. Probably night and maritime raids by their heavy / long range bombers.

Now the big weakness with these all fighters is that none of them had two speed or two stage (or turbo) superchargers. Even the P-38s, if any arrived, would be the pre-turbo types. So they are going to be limited at altitude. If the (extended) Battle of France is going to be a Battle of Britain redux, that would be a problem.

But I would argue that it wasn't going to be that, because it was also going to be a ground war. And (again, arguably) the greatest offensive strength for the Germans in the ground war was the Ju-87 dive bomber. The Ju 87 was key to their victories at Arras etc. So I think this would much more closely resemble the Desert War in North Africa. Only in this scenario (Battle of France late 1940 / and into 1941) the French here have much more competitive fighters. All of these fighters listed above could compete with the best German fighters of 1941, the Bf 109E and Bf 109F. The Bf 109s have two advantages here, climb rate and altitude capability. Meaning they will often be attacking from above. On the other hand, they'll be at a disadvantage in a dogfight. The British were able to compete with these successfully in North Africa, once they made some tactical adjustments, using mainly Kittyhawks Mk1 and Hurricane IIs, by mid 1942. Arguably a VG 39bis or Dewoitine 524 is a bit more competitive against a Bf 109F, though the French would need to be able to adjust their tactics successfully. They did for example have a good bit higher performance ceilings than an early Kittyhawk.

Which they apparently did already do in the actual Battle of France with their Hawk 75s.

The French fighters, or two of them, also have range more like the Kittyhawk did in North Africa, meaning they could escort some of their best available fast bombers on not just Tactical but also Operational strikes like against supplies, airfields, depots, railheads, bridges etc. etc. They could also use Kittyhawks, if they got any, as pretty effective dive bombers.

Then the next question mark for me comes in with the arrival of the Fw 190. Can any of these French fighters compete? Probably the Arsenal V.39bis can, but it's going to need a working HS 12Z engine. That's unclear both for "if" and "when".

I would say that in some scenario where they had a few more months, the French should have been able to neutralize the huge asset that the Ju-87 was for the Germans, much as it was neutralized in North Africa, and they would have been able to start hitting the Germans both in the battle and behind their lines, as was also done with success in the Desert War.

* These are estimated speeds, the others are tested speeds
** All three of these are the unimproved versions. All could and likely would have got more powerful engines by 1941.

 

[Steamed_Banana]

All three of those French fighter types can be up-gunned to 3 x 20mm Hispano cannons and with more ammunition, which would presumably happen within a few months. I think the French could have also put their 20mm cannon into P-36, P-40s, Martlet / Wildcats, etc. and maybe as defensive guns on some of the bombers too.

 

[Bretoal2]

All three of those French fighter types can be up-gunned to 3 x 20mm Hispano cannons and with more ammunition, which would presumably happen within a few months. I think the French could have also put their 20mm cannon into P-36, P-40s, Martlet / Wildcats, etc. and maybe as defensive guns on some of the bombers too.

It is so easy to rewrite history...

 

[Steamed_Banana]

It is so easy to rewrite history...

This is the "What If" subforum right? This is just a thought experiment, if it bugs you, maybe you can read another thread? Or is it better not to discuss anything? I was involved in another thread here about the realities of the actual operational history of various aircraft, and some people didn't like that either because maybe it was too harsh toward some cherished fantasies.

The three 20mm cannon on these French fighters however, is not a fantasy. That was the armament of the Swiss D.3802, and of the prototype VG 39bis.

Whether that could be done with a Martlet or a P-40 or not, I can't say, but the P-40D (the earliest Mark Kittyhawk I) did have provision for 20mm cannon originally. The limitation on the US use of the 20mm cannon seems to be due to the poor quality of the US made 20mm cannons, which were not very reliable. But the HS 404 was a pretty good cannon, albeit with it's own problems. It was good enough for use with a Spitfire and a Hurricane (among other aircraft) in wing mounts.

At any rate, I'm not saying it was very likely that such an adaptation would take place. Just that it was possible. All of this is purely speculative, so I don't see why it would be anything else but 'rewriting history'.

And to be clear, I don't see any way that the French could have delayed their defeat, given all the problems they had. Or that the Germans would have let them fully develop all their pre-War designs given that they lost. I'm just going through the possibilities here if they had somehow delayed their defeat by several months, per the OP. It's just a "What If", so take it for what it is.

 

[MiTasol]

It is so easy to rewrite history...

including to pretend that the HS404 cannon was fit for service so early in the war.