Advanced French Fighters vs 1942/1943 contemporaries (9 Viewers)

[Elan Vital]

@ThomasP Interesting, I plotted the figures for the V-1710s compared to the late 12Ys, this is the result:

The V-1710s soundly outperform the 12Y-51 with small H-S supercharger (the 12Y-51 with S-P supercharger should do better), especially past the critical altitude.

However, the 12Y-45 and -49 engines with S-P supercharger actually outperform the 12Y-51 with H-S supercharger at altitude and get much closer performance to the V-1710s at high and very low altitudes relative to their limited baseline output. In fact, the 12Y-49 which has a S-C tuned for higher altitude gets very close performance to the Allisons past 5500m. An hypothetical 12Y-51 with 12Y-49-style S-P supercharger might accordingly have somewhat greater output at high altitudes than the Allisons.

This would suggest that the swirl throttle S-P supercharger is somewhat beneficial compared to the Allison supercharger, especially when tuned for higher critical altitudes. The French may want to push and assist the Americans to integrate swirl throttles into the Allison supercharger, in which case the V-1710 would achieve a very useful superiority margin compared to the 12Y series.

But in turn, this means that Allison-powered French fighters like the VG 32 and 50 should perform better than most other French fighters, except 12Y-51-powered VG 36es if the latter possess S-P superchargers at higher altitudes. There is the caveat that the Allison installation is alleged to be longer on the VGs, which might reduce drag if exploited like the 12Z "long noses". Weight is increased, but the reduced drag might cancel that out, leaving a large increase in power.

 

[Steamed_Banana]

I don't think that there is anything to be explained there. The charts posted by him are in agreement with the data posted at Peril's site and other creditable websites, as well as in the book 'Vee's for victory'. A few HP down or up at a few feet up or down is nothing to loose sleep about.

Well, here's the thing. In this chart, it's clear that power starts falling off sharply for the V-1710-33 at a higher altitude than it does for the V-1710-39.

This is also shown, to varying degrees, in multiple other charts and period sources I've seen.

I initially ignored this more or less along the lines of "a few HP down or up a few feet".

But combat reports and commentary by pilots also support this. So I've come to around to believing the historical sources, which seem to also be reflected in the engineering specs, although I still don't understand precisely why the -33 would have a higher critical altitude. It seems to.

A fighter that has a limited altitude performance is a worse fighter than another fighter that has no such problems, or these problems are less acute. Accolade of being "a more effective fighter for the longer time than the Hurricane" is a damning with a faint praise.

This is one of those declarations based on technical specs which modern enthusiasts like us are wont to indulge in. I've noticed that the operational history tends to tell what you might call a competing story.

In theory, a MiG 3 or a Hawker Hurricane had much better altitude performance than a P-40. The P-39 and P-51A were much faster. And yet P-40s had a much better combat record. Not just in one place - In the Middle East, in North Africa and Sicily and Italy, in the South Pacific, in China and Burma and India. For many years. Even in the Aleutians. Russia is the exception of course for the P-39, but for reasons we are still trying to figure out. Some people would rather dismiss the history, for me, it's always worth considering. It's the reality check for what we think we understand about the technical specifications.

And to be clear, the Hurricane did have better altitude performance. The P-39 was faster. But other things seemed to ultimately matter more on the battlefield. Range for one. Roll rate. Dive speed and acceleration. Tropical fittings. Maybe other things we don't yet fully understand. Ultimately, if you had a choice to defend your island or your desert army or your jungle air base with 50 Hurricanes or 50 P-39s or 50 P-40s, the choice was pretty obvious.

It's the same for the F4F, or the Ki-43, or the A6M, or the D3A. Or the Ki-48. Or the Hawk 75. Or the A-20. Any number of aircraft which did better in reality than expected based on their stats and how many guns they had or how many bombs they carried. And many that were the opposite. The Typhoon looks so good on paper, but in reality, it fell short, in spite of it's mighty engine and performance. The Ki-49 looked like a big upgrade over the Ki-48, but it was a disaster. Same for the SM 84 compared to the SM 79. It was faster, more heavily armed, had more armor, better fuel tank protection. But it did terribly in combat, so badly they went back to the S.79.

Operational histories have their limitations as well. There are reasons on the battlefield - leadership, training, illness, logistics, field conditions, weather, mistakes or genius of the enemy - which can obscure the technical factors. But the paradox is that part of the technical merits of any war machine include it's adaptability to the real world, the real opponents they face, the real conditions they had to operate in. Sometimes these are not the traits we are looking at closely enough.

And while there is a lot of such noise, over time and multiple Theaters, it evens out.

P-40 was a fighter in the late 1940 (with weak firepower and no protection), and then in 1941-43. Comparison should've been made vs. the types entering the service in the same time. Also, for something to be really of note, comparison should include the best competition available, too.

Well, I agree of course. I think P-40 came up (I think?) because the French had them on order. If the war would have gone on, they would have been using some of the Tomahawks that ended up going to the British in North Africa and the Middle East. And then maybe Kittyhawks. Along with Hurricanes and Spitfires and everything else that worked that they could get their hands on.

Once with full firepower and protection, P-40 was indeed too heavy & draggy for the feeble horsepower available.
The US types of note were all with far better engines; even with similar engines, the P-39 and P-51 were faster than the P-40.

And yet, compare the P-39 combat outcomes in the South Pacific, or the (indeed, much faster) P-51 in Burma. or the Spitfire Mk V in the South Pacific and Burma. Even the P-38 and F4U in the South Pacific through 1943. It's now pretty clear that their record was equivalent or slightly worse than the P-40 and F4F against A6M and Ki-43-II etc. The only real advantage of the P-38 and F4U for the first year was 1) range, which did matter, and 2) ability to escort or intercept bombers at 20,000+ ft, which mattered as well but not as much because most bomber sorties at that altitude couldn't really cause much harm. And the lower altitude rated fighters could still intercept enemy bombers at high altitude (they couldn't really escort US heavy bombers though).

The real combat history, when you look at the data from both sides, tells us a different story than we were told and came to believe in the previous era.

As above - timing is crucial.
French and British will need something amazing for the more temperate climate, if not cold climate, with vast majority of air combat happening above NW Europe.

That's true, but they also clearly need aircraft for the battlefield if we are talking about a war continuing on the borders of France and Germany.

 

[Steamed_Banana]

This would suggest that the swirl throttle S-P supercharger is somewhat beneficial compared to the Allison supercharger, especially when tuned for higher critical altitudes. The French may want to push and assist the Americans to integrate swirl throttles into the Allison supercharger, in which case the V-1710 would achieve a very useful superiority margin compared to the 12Y series.

Now that is an interesting idea!

But in turn, this means that Allison-powered French fighters like the VG 32 and 50 should perform better than most other French fighters, except 12Y-51-powered VG 36es if the latter possess S-P superchargers at higher altitudes. There is the caveat that the Allison installation is alleged to be longer on the VGs, which might reduce drag if exploited like the 12Z "long noses". Weight is increased, but the reduced drag might cancel that out, leaving a large increase in power.

I know they were looking at adapting both Merlin and Allison engines for French fighters, but I always wondered about the weight. Why would drag be reduced?

 

[Elan Vital]

I know they were looking at adapting both Merlin and Allison engines for French fighters, but I always wondered about the weight. Why would drag be reduced?

From what has been said on the 12Z fighters with the longer reductor and accordingly longer nose, the longer and finer nose contributed to reduced drag.

Specifically, Cuny and Danel included that as one of the aerodynamic improvements envisioned for the D520 series, reducing the 100 Cx by 0.10.

 

[tomo pauk]

Wrt. the different flavor of the P-40 and V-1710, as well as their suitability and abilities, not just for this thread: I don't think that I have anything more to add, without becoming repetitive and tedious for the other forumites.

 

[ThomasP]

Hey Steamed_Banana,

re

And I note here once again that the military rating for the V-1710-33 is at a higher altitude (13,200') than the -39 (12,000'), in both cases at 3,000 rpm, and in both cases engine power falls of quickly after that altitude in full throttle. To me that says there is an engine issue here as well as airframe weight.

Possibly this will help explain what tomo pauk & Shortround6 have been saying up-thread.

These are the same charts I posted up-thread, but with the the altitude and manifold pressure ratings for 3 different outputs for each engine - 1150, 1090, 1040 BHP - in order to show what the performance differences are between the V-1710-33 and -39. Assuming the supercharger uses the same impeller, and no changes are made other than the impeller speed ratio (ie 8.77 to 8.80) the higher impeller speed will provide a higher rated altitude. These values are from various charts, but I checked out the math as well and it comes out to within +/-1% BHP , 0.2"Hg MAP, and 200 ft altitude, relative to the actual charts.

NOTE that each of the BHP outputs for the -39 occur at higher altitude than for the -33.

V-1710-33

V-1710-39

Basically, what these marked-up charts show is that the V-1710-39 could use 1090 BHP at 13,400 ft - or 200 ft higher than the -33, while the maximum output for the -39 was 1150 BHP at 12,000 ft. The unmarked-up charts apply specifically to the engines as they were rated per the dates on the charts, but the -33 was later rated for 1150 BHP at 11,800 ft. I do not know exactly what the specific parameters were that resulted in the different ratings, but Allison tried various modifications during the careers of the engines, including such things as adding/removing backfire screens of varying design, different valves and valve timing, at least one attempt at a different intake manifold design, at least one early-war increase in coolant volume flow, etc. (There was another increased coolant flow change made in late-1944 in an attempt to allow reliable cooling at over 1425 BHP, but that obviously does not apply here.)

In addition, the "AN-9531" (found next to "FUEL" in the title block) is the designation for the testing procedure used to find the 'lean mixture octane performance number' of the contemporary 100 octane fuel grade used in the engine power rating process. In the case of the 1939 dated chart for the -33 it is definitely pre-100/120 grade fuel, while the -39 may have been rated on 100/120 (if my information is correct the USAAF did not settle on 100/120 until late-1940 at the earliest). Higher grade fuels would allow higher manifold pressures and/or higher impeller speeds, either/both of which would allow higher altitudes and/or higher power ratings.

Make sense?

 

[Shortround6]

I will add or correct that
Higher grade fuels would allow higher manifold pressures and/or higher impeller speeds,
is a bit confusing.
Higher grade fuel will allow at the gear ratio/impeller speed used, higher power at lower altitudes. Which is where the WEP high powers come in.
Using a different gear ratio, like the 9.60 gears in the -81, -99, -115 engines changes the slope of the max power line.
The 9.60 gears also need more power to drive the impeller at any given air flow. At 9000lbs per hour the 9.60 gears need around 30-35hp more. The 9.60 gears will flow more air at any given engine rpm ant that is were the 1125hp at 15,500 rating comes from with the higher gears. It needs a whole new chart.

either/both of which would allow higher altitudes and/or higher power ratings.
Higher grade fuel with the same gear ratio allows for more pressure/power below the critical altitude (throttle is fully open to get that particular power level) by allowing the throttle to be fully opened at the lower altitude without wrecking the engine but does nothing at higher altitudes.
Changing the gear ratio (or adding 2nd stage) with the better fuel will allow higher pressures and increase power at both low and high altitudes but at the cost of higher intake temperatures and supercharger drive costs.

The 7.48 gears in the -87 engine in the A-36 used about 50hp less for the same 9000lb air flow and that was one way to help get the 1325hp for take-off rating.
It also gave the 1500hp at 5400ft at 52in compared to the 1490hp at 4300f at 56in WEP rating of the -39. Problem was that it no longer made 1150hp at 11,700ft.

I hope I have not confused things further.

 

[Steamed_Banana]

Wrt. the different flavor of the P-40 and V-1710, as well as their suitability and abilities, not just for this thread: I don't think that I have anything more to add, without becoming repetitive and tedious for the other forumites.

Sorry to belabour it, I don't mean to take the fun out of the discussion. I'm just a stickler for correcting what I perceive (correctly or otherwise) some of these embedded tropes.

 

[Steamed_Banana]

Hey Steamed_Banana,

re


Possibly this will help explain what tomo pauk & Shortround6 have been saying up-thread.

These are the same charts I posted up-thread, but with the the altitude and manifold pressure ratings for 3 different outputs for each engine - 1150, 1090, 1040 BHP - in order to show what the performance differences are between the V-1710-33 and -39. Assuming the supercharger uses the same impeller, and no changes are made other than the impeller speed ratio (ie 8.77 to 8.80) the higher impeller speed will provide a higher rated altitude. These values are from various charts, but I checked out the math as well and it comes out to within +/-1% BHP , 0.2"Hg MAP, and 200 ft altitude, relative to the actual charts.

NOTE that each of the BHP outputs for the -39 occur at higher altitude than for the -33.

V-1710-33
View attachment 896339

V-1710-39
View attachment 896341

Basically, what these marked-up charts show is that the V-1710-39 could use 1090 BHP at 13,400 ft - or 200 ft higher than the -33, while the maximum output for the -39 was 1150 BHP at 12,000 ft. The unmarked-up charts apply specifically to the engines as they were rated per the dates on the charts, but the -33 was later rated for 1150 BHP at 11,800 ft. I do not know exactly what the specific parameters were that resulted in the different ratings, but Allison tried various modifications during the careers of the engines, including such things as adding/removing backfire screens of varying design, different valves and valve timing, at least one attempt at a different intake manifold design, at least one early-war increase in coolant volume flow, etc. (There was another increased coolant flow change made in late-1944 in an attempt to allow reliable cooling at over 1425 BHP, but that obviously does not apply here.)

In addition, the "AN-9531" (found next to "FUEL" in the title block) is the designation for the testing procedure used to find the 'lean mixture octane performance number' of the contemporary 100 octane fuel grade used in the engine power rating process. In the case of the 1939 dated chart for the -33 it is definitely pre-100/120 grade fuel, while the -39 may have been rated on 100/120 (if my information is correct the USAAF did not settle on 100/120 until late-1940 at the earliest). Higher grade fuels would allow higher manifold pressures and/or higher impeller speeds, either/both of which would allow higher altitudes and/or higher power ratings.

Make sense?

Yes it does make sense. Thank you for posting this.

And I concede that in terms of power output at altitude, it appears that V-1710-33 and -39 are indeed virtually identical. It seems the main difference here is indeed the weight of the two types, with one caveat.

In trying to reconcile this with what I read in the operational histories and pilot narratives, I still see a difference. Again this is due to the intersection of weight and power - plus the power settings stipulated in the manuals. Hawk 81 / Tomahawk types use a military power rating of 39.3" Hg for 1090 hp at 13,400', and is still making just a bit less than that (1040 hp) at 14,300' (and due to having a lower weight, that was apparently enough), whereas the early Hawk 87, P-40D and E, are hitting their military power limit of 42" at 12,000', and they need the extra HP because they are heavier. Effectively the Tomahawk type does indeed have a higher 'performance ceiling', as a combination of the stipulated boost settings with available engine power and weight limitations. And this, IMO, helps explain the pilot narratives that the Tomahawk was viable in combat up to around 18,000 ft whereas the Kittyhawk I and Ia were limited to below 13 - 15,000ft. This resulted in changes in the altitudes that missions were being flown at by the DAF between Tomahawk and early Kittyhawk types. It's also notable however that the military power rating for the Tomahawk is limited to five minutes in the manual, whereas the Kittyhawk is allowed 15 minutes at military power. The V-1710-33 was not quite as robust as the -39 or the -73, though this may have been a very conservative limit.

It would be interesting to see a performance comparison of a four gun P-40D with a six gun P-40E. Removing a pair of wing guns is something that came up several times in the history of the P-40 and was officially part of the factory configuration for the P-40L and some of the N marks (not just the N-1 through -5), with wing guns shipped separately. In the Operational History, during periods where they were flying a lot of air combat missions against numerically and technologically tough opponents, and especially intercepting bombers at higher altitudes, P-40 units would often remove a pair of the wing guns and sometimes some other things (oil cooler armor, sometimes one of the fuel tanks). When they were flying a lot of strafing and dive bombing missions they would put them back in. Four wing guns was plenty for almost any Axis fighter or bomber the Allies encountered during the war. It was also of course the armament for the P-51B and C, and the F4F-3, and then later the highly successful FM-2.

Regarding the modifications done the early to mid run V-1710. In later versions of the V-1710-39 and for the V-1710-73, Allison made some quite robust modifications, peened crank shaft, indium coatings on bearings, different heat treatment on crank case and etc. all of which were designed to enable it to endure higher boost settings and for longer periods. But this did not increase altitude performance at all, to the contrary, it made the P-40K in particular much more potent below 10,000 ft, with military power rating increased from 42" to 44.2" Hg (and given a 15 minute rating), but at 11,800', max continuous is 37.8 " Hg at 11,000', and 'official' WEP increased to 60" for 5 minutes. For the early P-40E it was 44" - 46" Hg in the manuals, though this seems to have been ignored by a lot of pilots.

Now here is a question more pertinent to the thread.

Does anyone have performance test reports, graphs or charts for the Dewoitine D.520, VG 33, MS 406, Bloch 152 or any other French WW2 fighter? I don't believe WWIIaircraftperformance ever had much on the French types, but it seems to be down again for me so I can't check. I've never been able to find any anywhere else.

 

[Steamed_Banana]

According to my sources, a pair of .50 caliber machine guns of the type used in the P-40D, plus 500 rounds of 0.5" ammunition ads up to 278 lbs. A little more maybe for ammunition boxes and possibly gun heaters. I believe the armor for the oil system was about 40 lbs.

 

[Shortround6]

According to my sources, a pair of .50 caliber machine guns of the type used in the P-40D, plus 500 rounds of 0.5" ammunition ads up to 278 lbs. A little more maybe for ammunition boxes and possibly gun heaters. I believe the armor for the oil system was about 40 lbs

There is a manual for the P-40D&E. on this web site.

P-40 Flight Manual

This is the flight manual for the P-40 Warhawk. The year issued has to be either mid 1943 or 1944 as there is mention made of the P-40N-25, which was introduced in the summer of 1943. The P-40N-20-CU introduced the V-1710-99 engine, which was simply an -81 powerplant with an automatic engine...

ww2aircraft.net

Post #2
The manual starts with the empty weight (with radio) of 5894lbs which is 220lbs(?) heavier than the P-40C. P-40E is about 90lbs heavier but this is without guns/ammo and other stuff.
Design gross weight for the P-490E is given as 7944lbs or about 440lbs heavier than a P-40C. Some P-40s could vary by over 100lbs light weight due to production variations.
The 7944lb weight includes 120 US gal of fuel, 120lbs of oil, 4 guns and 1000 rounds of ammo.
Numbers in the manual may not add up. misc gun equipment for two guns seems to be 28.5 lbs.

AHT shows about a 100lb weight gain for the wing group between the P-40C and P-40E and a 50lb gain in the landing gear (later P-40s got heavier landing gear until the P-40Ns)
Propeller may have gained around 40lbs (?) P-40K and later props may have gained around 35lbs.
Other changes seem to be small or production variation (?).
Once the US decided they wanted to put 900lbs of guns and gun equipment (or more, manual says up to 1870 rounds of .50 cal ammo for the P-40E) in the wings a "light weight" P-40 was toast. A P-40E with max fuel and ammo weighed 8845lbs. You can leave out fuel and guns and ammo but you are pretty much stuck with the heavier wing and landing gear and some other things.

 

[Shortround6]

Does anyone have performance test reports, graphs or charts for the Dewoitine D.520, VG 33, MS 406, Bloch 152 or any other French WW2 fighter? I don't believe WWIIaircraftperformance ever had much on the French types, but it seems to be down again for me so I can't check. I've never been able to find any anywhere else.

I am not sure if the British ever got any French fighters to test in England or maybe they did some tests at French airfields to see if a more extensive test was warranted.
There may be French tests in French language literature.

 

[Steamed_Banana]

I am not sure if the British ever got any French fighters to test in England or maybe they did some tests at French airfields to see if a more extensive test was warranted.
There may be French tests in French language literature.

There are for sure also German tests of most of them. Swiss as well of course at least for a couple of these. Finns probably too for the MS. 406.

Maybe some of our French friends in here have access to some of the French tests and / or know where to find them.

 

[Steamed_Banana]

There is a manual for the P-40D&E. on this web site.

P-40 Flight Manual

This is the flight manual for the P-40 Warhawk. The year issued has to be either mid 1943 or 1944 as there is mention made of the P-40N-25, which was introduced in the summer of 1943. The P-40N-20-CU introduced the V-1710-99 engine, which was simply an -81 powerplant with an automatic engine...

ww2aircraft.net

Post #2
The manual starts with the empty weight (with radio) of 5894lbs which is 220lbs(?) heavier than the P-40C. P-40E is about 90lbs heavier but this is without guns/ammo and other stuff.
Design gross weight for the P-490E is given as 7944lbs or about 440lbs heavier than a P-40C. Some P-40s could vary by over 100lbs light weight due to production variations.
The 7944lb weight includes 120 US gal of fuel, 120lbs of oil, 4 guns and 1000 rounds of ammo.
Numbers in the manual may not add up. misc gun equipment for two guns seems to be 28.5 lbs.

AHT shows about a 100lb weight gain for the wing group between the P-40C and P-40E and a 50lb gain in the landing gear (later P-40s got heavier landing gear until the P-40Ns)
Propeller may have gained around 40lbs (?) P-40K and later props may have gained around 35lbs.
Other changes seem to be small or production variation (?).
Once the US decided they wanted to put 900lbs of guns and gun equipment (or more, manual says up to 1870 rounds of .50 cal ammo for the P-40E) in the wings a "light weight" P-40 was toast. A P-40E with max fuel and ammo weighed 8845lbs. You can leave out fuel and guns and ammo but you are pretty much stuck with the heavier wing and landing gear and some other things.

The ~300-500 lbs they stripped out fairly routinely seem to have made a significant difference in performance. Notably IIRC you can see this in climb rates in some of the British or Australian tests, though WWIIaircraftperformance seems to be partially down for me again right now so I can't double check it. As I recall there was a dramatic change in rate of climb.

A lot of aircraft had this issue at various points, i.e. just under or slightly over the weight that the engine or airframe could handle (usually the former). It's pretty much the same between F4F-3 vs F4F-4. The -3 was still pretty zippy, difference in climb rate is 1,000 - 1,500 fpm. The difference was once again only about 400-500 lbs (depending how the -4 was loaded). The empty weight of the FM2 was also about 450 lbs lighter than the F4F-4, though it could be loaded more heavily with more fuel and external stores.

The P-40F did not have this problem due to having more available power to a much higher altitude (7-8,000 feet higher), though as the faster Bf 109 and FW variants appeared in the Med they started stripping them anyway to get better climb, speed, and turn performance at altitude. I don't believe they stripped P-40Fs in the Pacific and I'm not sure if they ever got any P-40Ls there. The need for range would have precluded removing fuel tanks in the Solomons IMO.