Why was P-36 so successful in the battle of France?

[Wild_Bill_Kelso]

Where does it have that figure? For what its worth the manual has 665 km/h (413 mph).

Says it in the Wiki twice (shrug)

 

[Wild_Bill_Kelso]

I am rather suspicious of dive speeds from the 30s and first couple of years into the 40s. Didn't Curtiss claim over 700mph for the P-40 at one time?
At any rate the Curtiss certainly did do over 500mph in testing. Many of the manuals tell the pilots not to exceed 485mph, may have been changed later.
A lot of planes were tested at higher speeds than they were approved for in the manuals. The manual was supposed to keep the pilots out of trouble if they were flying with the CG not exactly centered or something else not quite right.

The P-40s did 520 mph in dives, but the manuals started out at 460, then 480, then 485, then I think maybe they got up to 500.

No matter how strong the aircraft is, very high speed dives are quite dangerous. In the P-40 getting over 400 mph also meant using a lot of rudder trim and / or having a very strong leg. Less experienced pilots should beware, you don't want to go into a spin at 450+ mph. Going down at 500 mph you get close to the ground very quickly and pull out always takes some time (and space).

There is always some gap between the recommended limits in the manual (and in training) and what the more experienced combat pilots (or company test pilots) figured out they could do in an emergency in the field.

I don't have any real primary source or even good secondary literature on the Hispano or D.520, but the Wiki on the D.520 says the plane was twitchy in general but handled well at high speed.

 

[Wild_Bill_Kelso]

Some of these things are certainly possible. How worth while they are I don't know.

Another thing that has soured me on the HS is that I have a number of books in Wilkinson's series "Aircraft Engines of the World" 1941- 1963.
Specifically the 1941, 1944 (2nd edition, after that it became an annual) 1946, 1947, 1948, 1949 and 1953 and a few later ones. The war time editions are somewhat pricier.
They are not primary sources and especially the war time editions have a lot of errors depending on the country. some are due to censor ship and others were just there wasn't that much stuff available.
But in regards to some of the French engines (not just H-S) in the 1941 book some of the performance claims are pretty much unbelievable. And in the post war books they seldom go down and they also don't go up much even with the fuel supposedly changed.
The French HS 12Z engines in the post war books are the lightest in weight, use the best fuel and make up to 1800hp for take-off (or a repeated typo?)
Now this wonder engine in 1947 was rated at only using 7.7lbs of boost (45.3in) for take off (100/130 fuel) at 2800rpm using a 2 speed supercharger.
The Spanish HS 12Z-89 (again the type 89 is actually the H-S engine type number for the family, not an individual engine model number.) is about 20kg heavier but since they don't use the same fuel injector pumps and don't use the same magnetos I am not going to read much into that. What I will read into it is that the Spanish engine only makes 1300hp for take off at the same rpm at slightly more boost, 8.6lbs (47.2in) while using 92 octane fuel using a single speed supercharger. The Spanish engine uses the P-S supercharger, the French doesn't say. the chances of getting anywhere near 1800hp out of the prewar H-S supercharger was about zero.
peak power of the Spanish engine in the 1947 edition is 1400hp at 2800rom at 14,800ft (4500meters) boost is not give but may be same as the take-off level of boost?

going back to the French engine and it's two speed supercharger we not only have the rather unbelievable take-off power we are told that the low gear was good for 1600hp at 2800rpm at 8,200ft, maybe it would and maybe it wouldn't. High gear is were things get truly unbelievable 1320hp at 28000rpm at 26,200ft (8000meters) and a "normal" rating of 1250hp at 2600rpm at 24,600ft. boost not given.

Please reread that last part. It is a single stage engine. Some pages earlier in the book we have a RR Griffon 74 with a two stage supercharger with intercooler. It was rated at 1420hp at 2600rpm at 20,500ft (6200 meters) The Griffon weighs about 700lbs more. A Griffon 88 (with counter rotating prop shaft and different supercharger gears) is rated at 1365hp at 2600rpm at 26,500ft (8100 meters.) Now "Normal" power is the max continues power not full military power or WEP or what ever. This single stage Hispano engine nearly matches the Griffon and beats two stage Merlins at high altitude. Something is not right. The 1946 book has a few less power ratings for the French H-S engine and the 1947 page is marked revised. The Saurer engines change in each book, The 1946 book lists the Swiss 12Y-51, the 1947 book lists the Saurer YS-2 with 4 valve heads and fuel injection and the 1948 book lists the Saurer YS-4 with variable supercharger, an extra 200rpm (2800) over the YS-2 and is rated on 100/130 fuel. It is rated at 1600hp for take-off at 2800rpm using 8.6lbs of boost.

Now we don't know if there are different size valves, (or cams or ports) we do know there are several different (more than 2) superchargers between the engines, and different fuel injection systems. So I don't expect things to be identical.

The very earliest 12Zs used carburetors in early development.

This sounds like reason to be mad at a specific book or some books, not necessarily a reason to be mad at the HS engine. There is all kinds of incorrect information about all kinds of stuff floating around right?

 

[Wild_Bill_Kelso]

An article on the development of the S-35

The Best French Pre-War Tank

A blog about World War II era archive documents, primarily dealing with armoured warfare.

www.tankarchives.ca

An article on the development of the S-40 and beyond.

Don't Leave Well Enough Alone

A blog about World War II era archive documents, primarily dealing with armoured warfare.

www.tankarchives.ca

These are great thanks

 

[Wild_Bill_Kelso]

Farman was making their 2-stage S/C by mid-1930s, so at least the plausibility is there.
A 2-speed S/C on itself is not an improvement by default, the fighters were just fine if the S/C used was any good. Hispano's S/C was not a good one,

I gather they tried different gear ratios with the HS, but a two speed S/C that provided decent power at a higher altitude would make a fighter like D.520 or VG.33 more effective against a Bf 109, conferring a better top speed and better performance for the higher altitude air superiority role rather than conceding the high ground to the Bosche.

S-P supercharger was a good one, and it circumvented the need for additional low-speed gear by employing the blades that lowered the losses at low altitudes.

Which supercharger are you referring to here, I lost track?

Russian M-105 indeed had a 2-speed S/C, still it was a 'worse' engine than the 1-speed supercharged Merlin 3 or V-1710-39, let alone the Merlin 45 or V-1710-81.

Yeah I was a little surprised to learn that the M-105 had a two speed S/C, as it seemed to perform at the usual low altitude range bands (below 15k ft)

 

[tomo pauk]

I gather they tried different gear ratios with the HS, but a two speed S/C that provided decent power at a higher altitude would make a fighter like D.520 or VG.33 more effective against a Bf 109, conferring a better top speed and better performance for the higher altitude air superiority role rather than conceding the high ground to the Bosche.

Engine on the D.520 (the HS 12Y-45) was already with a better S/C than what the VG.33 had (the HS 12Y-31). The -31 was even worse in altitude power than the older Ydrs and Ycrs models. These and the -31 were already using the high ratio for the S/C. The low-level engines (Ydrs2, Yfrs2, -26) have had the rated altitude at 900-1250m, thus making a bit better power down low.
Per L'Aeronautique from late 1938 - comparison between what appears to by the -31 (with H-S supercharger) and -45 (with S-P supercharger); dashed lines are power, full lines are boost; advantage of ~150 HP at 5000 m for the -45 is can be seen, as well as better low-alt power:



The D.520 was already a good match for the Bf 109E, unfortunately most of other things in the French military were not a match for the German military.

Which supercharger are you referring to here, I lost track?

Szydlowsky-Planiol - last names of the two gentlemen that designed it. They established the company 'Turbomeca' in mid 1938. Their S/C was also used on the HS 12Z.
Americans tested their S/C that was dameged, and the repaired to their (American) best knowledge.

 

[Wild_Bill_Kelso]

Thank you for that, very interesting!

But I thought the VG 33 (and up to -39 etc.) was tested with various engines, surely if they had 3 more months they would have put in a -45 or a -51 right? Didn't the D.520 get various (gradually improved) engines?

I agree the D.520 is a pretty good match vs. the earlier Bf 109D and E but it still has to concede the high ground due to altitude performance limitations. A two speed s/c seems like it could even the playing field quite well.

 

[Wild_Bill_Kelso]

The interesting thing about France in 1940 is that they seemed to have shifted, too late, from a dreamlike state with antiquated (and for aircraft, wonderfully ugly) designs, toward suddenly much better, world class (and quite pretty) designs... but they were a step behind the tempo and got caught before their shield was up.

I do think air power was decisive for the Germans in the Battle of France. And I also think, if they had time to swap out another eight or ten squadrons of Morraine 406s and Bloch 152s for P-36, D.520, VG.33 and maybe some P-40s and Wildcats, not to mention all the various locally and foreign made light bombers, they could have put up a much better fight. Plus, in a few more months, maybe the British can commit some Spitfires.

As it is, unless I'm reading the wrong numbers, as it was during the Battle of France, the French and British seem to have actually put a dent in the Luftwaffe with 1400 lost, is that right?

If so, it seems to compare with 1700 aircraft lost in the BoB (I am also getting this from a quick google search so correct me if I'm wrong)

If you double the number of capable fighters to shoot down those Stukas, and add some fast bombers (Bréguet 693, LeO 45, Marylands, Bostons) which can strike German airfields, and maybe ditch some of the failed designs (possibly Bloch 150 series, Potez 630) it doesn't seem inconceivable to me that you destroy another 500+ German planes. Where is the tipping point?

 

[tomo pauk]

But I thought the VG 33 (and up to -39 etc.) was tested with various engines, surely if they had 3 more months they would have put in a -45 or a -51 right? Didn't the D.520 get various (gradually improved) engines?

There was also the -49 engine in the works, that - at least it is how I understand it - have had the supercharger gearing with a higher step-up ratio, gaining a bit at higher altitudes while sacrificing the low-alt power.
power graph
It is very much possible that D.520 as-is never received the -49 engine (bar the test-beds and prototypes).

I agree the D.520 is a pretty good match vs. the earlier Bf 109D and E but it still has to concede the high ground due to altitude performance limitations. A two speed s/c seems like it could even the playing field quite well.

Disagree wrt. last sentence.
Two-speed S/C is not a panacea. Merlin III (1-speed S/C) was a better altitude engine than the DB 601A (infinite number of S/C speeds) or the M-105 (2-speed S/C).

French AF needed in 1940:
- leadership
- aggressive doctrine
- radar-assisted air defence network
- many hundreds of light and heavy AA guns to defend the air bases
- a proper fighter instead of the MS.406
- 1000 decent fighter aircraft
And last but not least: all Hurricanes and Spitfires the RAF has to be deployed in France, supported by a radar-assisted AD network.

 

[Greyman]

Sorry, but 700 mph is extremely outlandish.

700 mph TAS = Mach 0.92 at Sea Level, or Mach 1.01 at 20,000 ft

What happens when I mix up knots and mph back and forth in an online converter ...

 

[Wild_Bill_Kelso]

There was also the -49 engine in the works, that - at least it is how I understand it - have had the supercharger gearing with a higher step-up ratio, gaining a bit at higher altitudes while sacrificing the low-alt power.
power graph
It is very much possible that D.520 as-is never received the -49 engine (bar the test-beds and prototypes).

The high ground is important...

Disagree wrt. last sentence.
Two-speed S/C is not a panacea. Merlin III (1-speed S/C) was a better altitude engine than the DB 601A (infinite number of S/C speeds) or the M-105 (2-speed S/C).

Fair point

French AF needed in 1940:
- leadership
- aggressive doctrine
- radar-assisted air defence network
- many hundreds of light and heavy AA guns to defend the air bases
- a proper fighter instead of the MS.406
- 1000 decent fighter aircraft
And last but not least: all Hurricanes and Spitfires the RAF has to be deployed in France, supported by a radar-assisted AD network.

I agree with all that, and especially AA guns and radar which are probably not going to arrive in time regardless. But of that list "1,000 decent fighter aircraft" seems like it may have been in reach. And some good light bombers which would help as well.

Ultimately, I don't see France winning because the leadership and other bureaucratic / logistical / ideological problems, but I suspect they might have put a bigger dent in the German war machine and changed the subsequent outcome of the war in unpredictable ways.

 

[tomo pauk]

I agree the D.520 is a pretty good match vs. the earlier Bf 109D and E but it still has to concede the high ground due to altitude performance limitations.

The Bf 109D was well behind the curve by Spring of 1940. Better than MS.406 (not some feat - doh), but worse than Hurricane I or Hawk the French had, let alone the D.520.
The 109E have had ~50% more engine power than the 109D, and better firepower.

 

[Wild_Bill_Kelso]

109D wasn't Frontline fighter by BOF though right? Recon?

 

[Greg Boeser]

There were still a few Staffeln during the Sitzkrieg.
The Bf 109D had the same armament as the Bf 109E-1.

 

[elbmc1969]

French AF needed in 1940:
- a proper fighter instead of the MS.406

Simply upgrading all of the MS.406 to the MS.410 standard would have made a huge difference. Proper ejector exhausts for high speed thrust and a fixed radiator with a duct long enough to smooth the airflow. There were other changes, but those two alone were huge.

The MS.406 flew very nicely and did just fine against the Bf109D.

 

[Greg Boeser]

And would have kicked the Ar 68's butt!

 

[tomo pauk]

Simply upgrading all of the MS.406 to the MS.410 standard would have made a huge difference. Proper ejector exhausts for high speed thrust and a fixed radiator with a duct long enough to smooth the airflow. There were other changes, but those two alone were huge.

How good was the MS.410?

The MS.406 flew very nicely and did just fine against the Bf109D.

That's a damning with a faint praise

 

[Wild_Bill_Kelso]

I talked to a pilot at an air show who said he flew an MS 406 for a while at another airshow, and he said it was very nimble. The issue was basically streamlining & various protrusions, strange stuff like the radiator etc

 

[Wild_Bill_Kelso]

I think the 410 was about 20-30 mph faster

 

[Shortround6]

Some of these things are certainly possible. How worth while they are I don't know.

This sounds like reason to be mad at a specific book or some books, not necessarily a reason to be mad at the HS engine. There is all kinds of incorrect information about all kinds of stuff floating around right?

Basically the French H-S Z engine was vastly overrated and was overrated for a number of years, I would guess in an attempt to the sell the engine. Sales were few and/or late.
I don't have the 1950-51-52 editions of the series of books referred to. Perhaps the downgrading happen during those years.
The 1953 book has been referred to in one of the linked threads. But it doesn't follow normal specifications.

See: HS.12Z-17 Engine

Like being rated at 1300hp at 2650rpm for take-off using 3.3lbs of boost.
Now this does make sense for a single speed supercharger that is set up for high altitude.

However the other 3 performance ratings
Military.........................1500hp/2700rpm/21,000ft boost not given.
Normal..........................1500hp/2400rpm/20,700ft boost not given.
Cruising.........................820hp/1950rpm/20,000ft boost not given.

show a very likely misprint as looking by the chart kindly provided by Bretoal2 back in 2020 we can expand the listings to.

Take-off ((Decollage)............................ ........................1300hp/2650rpm/36.6in (930mm)+3.3lbs
Military ( Surpuissance momentanee)....................1500hp/2700rpm/21,000ft boost 1050mm
Normal (Regime nominal)...........................................1150hp/2400rpm/20,700ft boost 850mm
Cruising (Croissiere economique)...............................820hp/1950rpm/20,000ft boost 650mm.

What we really don't know is what kind of supercharger the 1950s engine was using becasue it doesn't seem to be the same as late 40s engine or the same as the Spanish or Swiss or Russian engines were using.

We also don't know why the 1950s engine was down rated to 2700rpm instead of 2800rpm. We can speculate that it was to give greater engine life. But we also need to figure out what engine life was to begin with.

What I don't like about the H-S engine post WW II is that some of the published figures were obviously wrong and/or depended on "magic" superchargers.
Superchargers did vary tremendously between the mid 1930s and the late 1940s but the H-S superchargers would have far exceeded any other supercharger in efficiency.
What is the displacement of the engine?
What is the RPM engine?
What is manifold pressure?
From that you can make an estimate (in part based on what other engines are doing).
A particular engine may be operating at a lower level.
A particular engine may beat out out any other.
But for a particular engine to beat out it's competition by a huge margin and/or make the claimed power at a much lower manifold pressure (less total airflow) something is wrong.