Advanced French Fighters vs 1942/1943 contemporaries

[TM06]

French license Allison V-1710s.
Stuff them in the D.520s. Maybe lengthen the tail a bit.

While I definitely like the idea of an Allison-engined D.520, why not choose the Merlin? It's much closer in proximity which eases logistics, and the Merlin is a much better engine IMO. Also doesn't put the French aircraft into the low altitude trap the early Allison aircraft fell into.

Beg for Spitfire IXs in 1942/43.

Shouldn't the theoretical Allison-engined D.520's be roughly comparable to the Spit IX? The basic D.520 was equal to the Bf 109 E-4 and Spitfire Mk I, and the 520Z showed solid performance that would likely get even better with a superior engine. Britain also probably has their hands full trying to make enough IX's for themselves around this point, so not having to export those would ease their heavy burden.

Basically the French were trying to flog a pair of dead/dying horses with the H-S and G-N engines and were trying to save themselves by hitching smaller carts to them to keep up with the neighbors. Unless the French can pull off a Swiss YS-2 type conversion by 1942 just give the H-S engines a decent funeral.

It's not infeasible that they could. Both Swiss and Russian engineers seemed to reach the same conclusion for the HS engines, and HS reached the same conclusion as well with the 12B - described as much more conventional and strongly built (and heavier than the other two by about 150 kg). If HS still have the ability to actually develop the engine, they would likely reach the same conclusion faster. Hell, they might even be able to get it done by 1941 if all goes well.

 

[tomo pauk]

French license Allison V-1710s and Wright R-2600s and scrap the domestic stuff.

Merlin is a superior engine in all aspects - timing, being debugged, and making better power.
I'm not sure how come the R-2600 became a fighter engine after 10-15 years of convincing us that it is bad in that role.

 

[Bretoal2]

and the 520Z showed solid performance

The D 520 Z showed nothing, all values were estimates and D 520 Z never flew.

 

[TM06]

The D 520 Z showed nothing, all values were estimates and D 520 Z never flew.

Eh, semantics. It was extremely close to flying. But even with a conservative estimate, it'd still be around the level of the IX. The 520 was a very good plane for when it was made, it just never had the time to mature into what it could've been. Looking at the various projects based around it (SE.520Z, M.520T, D.55x) can give an idea of what it could've become.

 

[Shortround6]

While I definitely like the idea of an Allison-engined D.520, why not choose the Merlin? It's much closer in proximity which eases logistics, and the Merlin is a much better engine IMO. Also doesn't put the French aircraft into the low altitude trap the early Allison aircraft fell into.

You have to decide in the Spring of 1940 at the latest. The logistics problem is minor. France is going to have to import machine tools from the US in any case. Packard signed the deal in Sept 1940 but talks had been going on since July aft the Ford talks stopped. Packard was looking at the sample engine and drawings for weeks before the deal was signed. Packard was supposed to build 800 engines per month. They built 42 engines total in 1941 and didn't hit the 800 engines a month goal until July 1942. They hit 702 in June and 602 in May. That is sort of the time line, Packard and the US and England were all lucky in that the 2 speed Merlin was the engine selected. A few months earlier and it might have been the single speed Merlin XII?
French do get domestic production of Allisons for all the P-40s and P-322 Lightnings they ordered

The Low altitude Allison was offering 1090hp at 4000meters.
The H-S Y-45 was offering 920hp at 4200 meters and that is with P-S supercharger.
The Troublesome H-S Y-51 was offering 1000hp at 3250 meters.
Yes the Allison was heavier, but at least it worked.

Problem the early Allison had was the 7000lb plus engines they stuffed into. An empty P-40B weighs within a couple hundred pounds of a loaded D.520.

Shouldn't the theoretical Allison-engined D.520's be roughly comparable to the Spit IX?

Why? Did the British even know how the Merlin 60 was going to turn out?
French need to plan for something like the Spitfire II (Merlin XII) or Spitfire V (Merlin 45).
We cannot expect magic. A Merlin 60/61 in a D.520 is putting 1000 liters in a 500liter bottle. You need not only the supercharger, you need bigger radiators, you need the intercooler/s and you need a bigger prop.

The basic D.520 was equal to the Bf 109 E-4 and Spitfire Mk I, and the 520Z showed solid performance that would likely get even better with a superior engine. Britain also probably has their hands full trying to make enough IX's for themselves around this point, so not having to export those would ease their heavy burden.

The D.520 was equal or close to the 109E-4, the Spitfire I not so much and in July/Aug the standard (thing to measure against) was the Spitfire II with Merlin XII engine.
It doesn't matter what the 520Z was promised to do if the engine would not deliver (stay running).

Merlin is a superior engine in all aspects - timing, being debugged, and making better power.
I'm not sure how come the R-2600 became a fighter engine after 10-15 years of convincing us that it is bad in that role.

You are right, the Merlin was better. Now is France going to get the "deal" or is the US given the deals France is already getting from the US and fact that France needs to buy the tooling from the US anyway. Britain was buying a lot of the machine tools from the US for British shadow factories anyway. The whole P-322 fiasco was the French and British wanting interchangeable engines with the P-40 Tomahawk.

The R-2600 was not a good fighter engine, it was what France had a chance of buying/making.
Mediocre engine beats bad engine (G-R) or expensive, hard to make engine (Hercules) or engine that is not quite there yet (R-2800). France has to get through the last half of 1940 and all of 1941 before worrying about 1942-43.

The R-2600 has a chance of fitting in a MB-157 airframe. A two stage R-2800 in a MB-157 airframe, has two chances and slim was on the noon train to Dover.
Yes France can come up with new airframes. Service use in 1943? FW 190 first flew in June 1939. Maybe the French don't make some of the mistake that Fw did?

 

[TM06]

Why? Did the British even know how the Merlin 60 was going to turn out?
French need to plan for something like the Spitfire II (Merlin XII) or Spitfire V (Merlin 45).
We cannot expect magic. A Merlin 60/61 in a D.520 is putting 1000 liters in a 500liter bottle. You need not only the supercharger, you need bigger radiators, you need the intercooler/s and you need a bigger prop.

It doesn't matter what the 520Z was promised to do if the engine would not deliver (stay running).

When I say 520Z in this context, I don't mean the actual aircraft fitted with the 12Z engine. What I mean is that fitting a Merlin 60 or V-1710F into a D.520 would likely result in something that would look similar to the D.520Z - larger wings, longer nose, extended tail structure, radiator and intercooler arrangements, and a larger propeller.
Let's call this hypothetical Merlin or V-1710 D.520 the D.520AM for Allison/Merlin to avoid confusion.

 

[Shortround6]

When I say 520Z in this context, I only mean in form rather than being fitted with the 12Z engine. Fitting a Merlin 60 or V-1710F into a D.520 would likely result in something that would look similar to the D.520Z - larger wings, longer nose, extended tail structure, radiator and intercooler arrangements, and a larger propeller.

They were planning on using the Allison in a few of their planes in 1940, not sure if they got an Allison into the country or managed a test flight.

The Problem with the Merlin 60 is that you have to rebuild the whole airplane. Do you have the time and engineering capacity?

The Spitfire and Mustang were big enough to hold the engine and the extra bits (Mustang took a spice down the middle of the fuselage, Spitfire hung everything under the wing) and didn't need bigger wings or much more than larger vertical fins. Adding 4 blade props kept them about the same diameter. When you start with a plane that is only about 70% as big (wing area) you need to do a lot more than just cram the engine in. Just in the engine, cooling system and propeller the P-51 gained almost 800 lbs, this does not include oil system or other little bits and pieces, not counting fuel system as that depends on airframe.

I have been harping on the small French airframes from the beginning, here is where it bites them.

You can scale up the airframes but that often means little in common except for appearance with the older version. Also means that you use up a lot of the increase power hauling the bigger airframe around. Spitfire and P-40s were actually pretty darn good, the P-51 was in a class by itself. Those 1940s Tomahawks did about 345-350mph with their 1040 hp engines with their big wings and extra 1000lbs compared to the 109E. They had problems climbing but as far as speed went (low drag) they were better than average. The P-40Bs were supposed to do 330+ mph at 15,000ft using 920hp (2600rpm).
The D.520 is operating behind the curve.
Using the D 551 trick of cutting off a large part of the wing isn't going to work.

 

[TM06]

They were planning on using the Allison in a few of their planes in 1940, not sure if they got an Allison into the country or managed a test flight.

To my knowledge, they didn't get any Allisons into a working D.520 prototype. There was a project started for it designated D.522, but that was abandoned due to the armistice.
They did however get a Merlin into a functioning D.520 prototype in the form of the D.521 which was fitted with a Merlin III. As far as I know there was very little in the way of airframe modifications beyond the removal of the 20 mm motorcannon. It had superior performance to the D.520 but it was extremely difficult to control, with test pilot Marcel Doret calling it "too dangerous" to fly.

 

[Bretoal2]

To my knowledge, they didn't get any Allisons into a working D.520 prototype. There was a project started for it designated D.522, but that was abandoned due to the armistice.
They did however get a Merlin into a functioning D.520 prototype in the form of the D.521 which was fitted with a Merlin III. As far as I know there was very little in the way of airframe modifications beyond the removal of the 20 mm motorcannon. It had superior performance to the D.520 but it was extremely difficult to control, with test pilot Marcel Doret calling it "too dangerous" to fly.

Dangerous to fly because 12 Y turned clockwise and Merlin anti-clockwise.... while the D 520 airframe, equipped with an asymmetric tail fin to counter torque, had not been modified in the D 521 !

 

[ThomasP]

Probably CoG issues combined with either a too-short moment arm to the tail, or too small a rudder and/or elevators for effective control. If that is the case they should have been able to solve them given a bit of time.

 

[ThomasP]

Whoops! Bretoal2 posted same time I posted. Mine was a guess. Presumably Bretoal2's is based on actual knowledge of the airframe layout.

 

[Bretoal2]

Whoops! Bretoal2 posted same time I posted. Mine was a guess. Presumably Bretoal2's is based on actual knowledge of the airframe layout.

Not presumably, but certainly.

I am a technical historian, not a fortune teller.

 

[Shortround6]

The term "dangerous to fly" doesn't actually tell us much.
Griffon powered Spitfires were dangerous to fly, for pilots had flown Merlin powered Spitfires and for the same reason, their props spun in different directions.

But "dangerous to fly" can also mean too far forward center of gravity, too far aft center of gravity.
Or control response is too quick leading to further and further swings of direction (in any direction) or too little control response.

And we haven't even gotten into really trying to land the plane

 

[Bretoal2]

The term "dangerous to fly" doesn't actually tell us much.
Griffon powered Spitfires were dangerous to fly, for pilots had flown Merlin powered Spitfires and for the same reason, their props spun in different directions.

But "dangerous to fly" can also mean too far forward center of gravity, too far aft center of gravity.
Or control response is too quick leading to further and further swings of direction (in any direction) or too little control response.

And we haven't even gotten into really trying to land the plane

The problem with the Spit Griffons was reflexes of their pilots, not the behavior of the plane.

In the case of D521, the asymmetric vertical fin turned in the wrong way increased torque instead of reducing it.

And Doret was the victim of a mishap during the D521 tests : as the Merlin consumed much more than the Hispano, he ran out of fuel while making a "borderline" landing.

 

[Shortround6]

I thank you for your input, because without it, we don't know what ""dangerous to fly" means.
Which means we don't know what the remedial course of action is.
Different training?
Change the vertical fin?

for other planes move 100-200lbs of weight around,
or change the area of the controls or change the linkage/leverage.

Throw it out and start over?

 

[TM06]

I mean if the problem was the vertical fin turning the wrong way, it's a presumably easy fix to make it turn the other way, no?

 

[Bretoal2]

I thank you for your input, because without it, we don't know what ""dangerous to fly" means.
Which means we don't know what the remedial course of action is.
Different training?
Change the vertical fin?

for other planes move 100-200lbs of weight around,
or change the area of the controls or change the linkage/leverage.

Throw it out and start over?

Obviously the only solution was to reverse ("mirror") the vertical surfaces.

But some time was necessary to do this... and France had not it before june, 25.

 

[Bretoal2]

I mean if the problem was the vertical fin turning the wrong way, it's a presumably easy fix to make it turn the other way, no?

Vertical surface of the D 520 had an asymetrical profile. To "reverse" this profile, it was necessary to rebuilt entirely it !

 

[TM06]

Vertical surface of the D 520 had an asymetrical profile. To "reverse" this profile, it was necessary to rebuilt entirely it !

That certainly is a problem for a France that's running on borrowed time, but not infeasible for a France that can fight to 1941.

 

[tomo pauk]

The Low altitude Allison was offering 1090hp at 4000meters.
The H-S Y-45 was offering 920hp at 4200 meters and that is with P-S supercharger.
The Troublesome H-S Y-51 was offering 1000hp at 3250 meters.
Yes the Allison was heavier, but at least it worked.

In 1940, there was no low altitude V-1710. If we're playing the finger pointing game, the V-1710 was a troublesome engine from the late 1940 to mid 1941, troublesome enough to be down-rated by some 10%. Thus being no better than the HS 12Y-49, while being heavier and without the motor cannon option .
French will be hard pressed in 1941, and Merlin is the engine that can level the playing field vs. the Bf 109F and Fw 190.

Why? Did the British even know how the Merlin 60 was going to turn out?
French need to plan for something like the Spitfire II (Merlin XII) or Spitfire V (Merlin 45).
We cannot expect magic. A Merlin 60/61 in a D.520 is putting 1000 liters in a 500liter bottle. You need not only the supercharger, you need bigger radiators, you need the intercooler/s and you need a bigger prop.

Thinking about the Merlin 60 series in 1940 will indeed require a far better crystal ball than the shops were selling back then
Luckily, the French fighters, like the D.520 or the VG 30 series were small, light and well streamlined, so even the Merlin XII will turn them into the performers, talk Bf 109F or MC.202 RoC and turn of speed.

You are right, the Merlin was better. Now is France going to get the "deal" or is the US given the deals France is already getting from the US and fact that France needs to buy the tooling from the US anyway. Britain was buying a lot of the machine tools from the US for British shadow factories anyway. The whole P-322 fiasco was the French and British wanting interchangeable engines with the P-40 Tomahawk.

If any country will be getting the deal in 1940 with France surviving, that should be France, no?
Hard cash spent on the US machine tools is best used in making a competitive engine, not the engine that is behind the Europe's best.

The R-2600 was not a good fighter engine, it was what France had a chance of buying/making.
Mediocre engine beats bad engine (G-R) or expensive, hard to make engine (Hercules) or engine that is not quite there yet (R-2800). France has to get through the last half of 1940 and all of 1941 before worrying about 1942-43.

Let's not clam together the words 'buying' and 'making'.
French can buy the R-2600 already in 1940; French making the R-2600 will be a thing for 1942 if everything goes flawless? Yes, someone will also need to redraw the drawings from the US to European perspective (not needed on the British engines), as well as making the measurements in metric.

The R-2600 has a chance of fitting in a MB-157 airframe. A two stage R-2800 in a MB-157 airframe, has two chances and slim was on the noon train to Dover.
Yes France can come up with new airframes. Service use in 1943? FW 190 first flew in June 1939. Maybe the French don't make some of the mistake that Fw did?

I'm not sure what is that Fw's mistake you've mentioned.

You can scale up the airframes but that often means little in common except for appearance with the older version. Also means that you use up a lot of the increase power hauling the bigger airframe around. Spitfire and P-40s were actually pretty darn good, the P-51 was in a class by itself. Those 1940s Tomahawks did about 345-350mph with their 1040 hp engines with their big wings and extra 1000lbs compared to the 109E. They had problems climbing but as far as speed went (low drag) they were better than average. The P-40Bs were supposed to do 330+ mph at 15,000ft using 920hp (2600rpm).
The D.520 is operating behind the curve.
Using the D 551 trick of cutting off a large part of the wing isn't going to work.

Small airframes on these fighters are a feature, not a bug. D.520 with similar power as the P-40 with the de-rated V-1710 was good for another 20 mph, and will climb much better since it was lighter. Small size and good streamlining means that fighter will still be good even with yesterday's engine.

Using the 109E as a speed benchmark is a red herring, since the 109E was as streamlined as a brick. Other fighters in 1940-41 with the same engine were either of the same size and faster, or were bigger and with similar speed (apart the Hurricane). Or, the aircraft of the similar size and with 10-20% less power were as fast as the Emil.