How good a plane was the P-40, really?

[Wild_Bill_Kelso]

It looks like there is an antenna wire coming out of the port wing of this (Aussie?0 P-40N... is that what that is? Or is it like a vine in the foreground?

 

[Thumpalumpacus]

View attachment 765520

It looks like there is an antenna wire coming out of the port wing of this (Aussie?0 P-40N... is that what that is? Or is it like a vine in the foreground?

Grounding wire?

 

[Wild_Bill_Kelso]

That would make a lot of sense

 

[bf109xxl]

Let me help circle this back to relevance. Which is here is that you tried to argue from authority, as if you were the only person on the forum who understands statistics, which you were leveraging to insist that there is no observable correlation between combat outcomes and merits of a given fighter aircraft in WW2.

I never stated anything you ascribing me here. You have a rich imagination, but, please, find a better use for it. Please, do not extrapolate anything I write about you personally on the whole audience of the forum.

Which is patently, objectively, ridiculous.

Objectively, you have not demonstrated yet any arguments supporting your opinion.

I don't need to write a SQL query to tell me that, and I don't need a degree in statistics either. It is really just a coincidence that I wrote BI software (for highly demanding clients, and which was heavily scrutinized) for more than 20 years. I don't have the knowledge of a true statistician, but I certainly understand how sampling, survey methodology, and statistical quality assurance work.

I am pretty sure that you have only the most general knowledge of statistics and never dealt with statistical analysis more complex than the calculation of a standard deviation for normally distributed data taking into account your judgements.

None of that is really necessary to recognize that the combat outcomes of the Bloch 152 are dramatically worse than those of the D.520, and that is in turn, at least in large part, a reflection of problems with the aircraft type.

That's great! You find the simplest case of all possible, when the conditions are indeed comparable and the comparison is quite correct, and then bravely extrapolate it to all the other cases. Surely this is an excellent and very correct approach.

Do you base that on a statistical analysis of arguments or on your intuition, or are you just using it as a device to further what you see as your cause?

Your understanding of logic is as deep as your understanding of statistics.

Let me be clear and candid then. There are three issues at hand:

1) You came across in a previous discussion here as a fanatic adherent of outlier positions, including blanket disparagement of the Soviet air forces. It struck me as more ideological than "data driven" to use a corporate buzzword from the database world. Your handle is also a hint of a particular bent. People with various agendas show up on forums like this and I have learned from experience it's both pointless and boring to debate them. We had past exchanges which reinforced this view in your case. True to this type of forumite, in my experience, you do not seem to be receptive to, or even aware of points which refute your pre-concieved positions.

1.Your point of view is due to only one reason: you know too little about the Soviet Air Force. That is why you write all kinds of nonsense about them. When you are proven to mistake, you rush to google information that I know for a long time.
2. If you think it is pointless to debate, then don't debate. But for some reason you prefer to write long boring posts about how boring it is for you to debate.
3. First you should at least gain the required level of competence to judge if I have a preconceptions. So far, I've had no reason to suspect you of that.

2) The P-39, which you seem eager to discuss, was driven deep into the ground as a subject by another forumite with just such an agenda driven bent, in the not too distant past. To the extent that people here didn't even want to mention that aircraft type by name and were using euphemisms as a joke. Which ties into...

I wasn't going to discuss Cobra at all. I only made an obvious remark that it is often incorrect to judge an airplane by the outcome (which is difficult to estimate by itself).
The outcome is a convolution of many functions over time, and not always the parameters of these functions remain constant over time - e.g., pilot training, manufacturing quality, force ratio with the enemy, tactics, average degree of aircraft/engine wear, etc. Even the overclaim degree could vary.
Thus, the most reliable sources to draw conclusions on the airplane are the test reports (including front-line tests) and analysis of own losses.

3) ... the thread is about the P-40 and I don't want to heavily derail it. There is another pretty recent thread on the effectiveness of the Soviet Air Forces which you can chime in on if you want to expand upon your theories of general Soviet inferiority.

I never told about any kind of theory of general Soviet inferiority. You are arrogantly attributing your fantasies to me. My point was, that Stalin's regime was extremely ineffective and was responsible for additional losses suffered by the Soviets. Repressions in the army deprived Soviet officers of initiative and decision autonomy, repressions among engineers and scientists deprived the USSR of a large number of experienced specialists, whose absence negatively impacted the quality of Soviet aircraft (and not only aircraft). Erroneous production planning led to a lack of resources (in particular, for pilot training) resulting in huge losses at the front. A well-trained Soviet ace pilot was as good as a German "expert" or any Allied ace. But the problem was that young pilots had too little chance to gain sufficient experience because of the totally inadequate training system as well as principles of rotation/replenishment of air regiments.
And if I write about the shortcomings of the Soviet system or about the problems with Soviet weapons, it does not mean that I admire the German ones. It only means that I am trying to analyze more or less objectively the reasons for the inefficiency of one of the sides, namely the one that is of major interest to me.
I don't try to speculate about things I don't know well enough, but if I state something, I can always refer to a reliable source. You don't.

I admit that for these three reasons, I am not eager to wade into the weeds with you about these various issues, but if you want to revive the Soviet Air Force thread I will engage with you in there in detail. I think it is unlikely we will learn much from each other, but there are many other people on this forum with a wealth of knowledge of WW2, maybe we will both learn something from them.

Definitely, I cannot learn anything new about the Soviet Air Forces from you.

So you are suggesting that Ehrengardt is the only relevant source on the Normandie Niemen squadron, and that his conclusion that they chose the Yak fighter to appease the Soviets is the irrefutable truth, rather than a theory?

I suggested Ehrengardt just because he was the only one author known to me who used archival documents. I read the French memoires (not only de la Poype's one) as well as popular books on the topic. And I find Ehrengardt more reliable than anything else I read on the topic. I just asked you to cite any comparable source. You were not able to do it.

I have a day job today as an historical researcher, on a very different era. It has become abundantly clear to me from that vocation that both primary sources (like memoirs) and secondary or tertiary sources (like any postwar history, whether academic or popular) have their own unique challenges. Pilots do sometimes make mistakes in their writing, particularly in postwar literature like memoirs - we were recently discussing some of those of Pierre Clostermann, speaking of French aces. I admire Clostermann but he clearly did make some mistakes. However, taken in aggregate primary sources, including both wartime writing by pilots and post-war memoirs, are very useful. It just has to be checked alongside more prosaic primary data like unit histories.

I didn't ask you to discuss memoires. I only asked you about any alternative source based on documents. Then we can compare the reliability.

Postwar analysis and histories are also not free of mistakes, very much to the contrary, as anyone who has read them is well aware. This is particularly the case when it comes to the technical details of war, for which hard, easily quantifiable data can be elusive. I would say it is doubly so with postwar analysis of WW2, and in particular many 20th Century books on WW2 (like Ehrengardts) are full of postwar cliches, tropes, and legends, and are often missing data from both sides.

You've never heard about Ehrengardt before I mentioned him. What the hell are you ascribing any clichés, etc. to him for? Seems, that you never read any serious post-war analysis at all and recognize any popular book on the topic as "analysis". Otherwise I cannot explain this bullshit about "clichés". Even the Soviets were able to separate analysis from propaganda, they just did it confidentially - some of these materials used for high officer education in military academies were declassified in 1990s, they are objective enough.

That is why a new generation of authors have become so prominent in this field of study in recent years. They have used data from Axis sources to help us verify Allied claims, for example, and to flesh out the whole narrative.

In this particular case any comparative study was not necessary - French archival documents are quite enough to draw a conclusion.

I haven't read Ehrengardt's history so I don't want to make any assumptions about him. He might be a good historian and it may well be a good history. But I don't automatically take your word for this particular issue, nor do I believe he is the last word on the subject of that unit. In fact I know perfectly well to the contrary.

I'm not interested in your beliefs. I am only interested in reliable sources on the subject under discussion. You can't cite any of them.

Why would being Jewish have anything to do with communism necessarily? I have to admit that I don't know anything about Mirlesse personally.

Seems, that you don't know much about de la Poype personality as well.

I say de la Poype was about as far from a communist as you can get because he was an entepreneur and businessman,

When? In 1942? )))))) He was a 22 years old young pilot without any experience in plastics, car design, company management, etc. But surely, American and British officials had a magical crystal to look into the future.

and an avowed capitalist. He designed a car for Citroen and owned multiple factories making plastics, as well as resorts in the Caribbean.

He became a capitalist after the war. Not in 1942.

He was a remarkable guy, who went to Russia to fight the Germans out of patriotism, I believe.

You should read carefully before you write another nonsense. De la Poype was born on July, 28 1920. He was just a young pilot without any serious merits in 1942. Most French communists considered themselves patriots and played a very important role in the Resistance.

His father was killed in the Battle of France. That, and wanting to avenge the fall of France seem to have been his key motivation. He was flying for the RAF (and was wingman of Paddy Finucane for a while) but at a time (1941) when the front was somewhat static. He wanted to be at the tip of the spear.

"A guy at the tip of the spear cannot be a communist! I swear!" )))))

 

[Wild_Bill_Kelso]

I never stated anything you ascribing me here. You have a rich imagination, but, please, find a better use for it. Please, do not extrapolate anything I write about you personally on the whole audience of the
Objectively, you have not demonstrated yet any arguments supporting your opinion.
I am pretty sure that you have only the most general knowledge of statistics and never dealt with statistical analysis more complex than the calculation of a standard deviation for normally distributed data taking into account your judgements.
Your understanding of logic is as deep as your understanding of statistics.

For someone who doesn't like long-winded posts, and who claims to focus on statistical analysis and verifiable data, you seem to lean heavily into personal attacks, and make it very clear to any reader that you have a poor grasp of the difference between objective truth and your own subjective judgement. Not an unusual affliction, unfortunately, but one which would tend to make me very leery of trusting your statistics in a professional field.

Dripping with so much malice and obvious anger toward someone you don't know is not a reflection of cautious analysis or good judgement.

The statistical reports I wrote professionally had to be used on a daily basis by industry and by government / military agencies to make serious decisions, and were closely scrutinized by a variety of different professional organizations with heavy responsibilities and major financial interests, in this case in the movement of ships. Any errors were noticed immediately.

The data is by it's nature in measuring the real world, which means there are some limits to what can be known, but big decisions still have to be made on that basis. The data must be as accurate as possible and the presentation as clear (and transparent) as possible. This is a fairly close analogy to determining patterns in wartime, such as assessing combat outcomes, by leaders who had to make decisions such as which units to put in or take out of the line, which aircraft types to continue to use, which to discontinue, and which improvements and modifications needed to be done both to aircraft and training.

Not only is it possible to draw conclusions from wartime operational histories, it absolutely had to be done and was done over and over again.

I never told about any kind of theory of general Soviet inferiority. You are arrogantly attributing your fantasies to me. My point was, that Stalin's regime was extremely ineffective and was responsible for

You didn't "told about" it, you telegraphed it. Repeatedly.

Definitely, I cannot learn anything new about the Soviet Air Forces from you.

Sometimes when you reply to a post in a forum, it is not just to address the person you are responding to. I can already tell that you are not here to learn anything and am not trying to convince you of anything.

I suggested Ehrengardt just because he was the only one author known to me

I didn't ask you to discuss memoires. I only asked you about any alternative source based on documents. Then we can compare the reliability.

You mentioned one analysis known to you, I mentioned a memoir known to (and possessed by) me. And noted that I met the individual who wrote the memoir.

I'm not interested in your beliefs. I am only interested in reliable sources on the subject under discussion. You can't cite any of them.

Lol so I guess Bergstrom isn't a reliable source? And none of the Soviet statistics and pilot interviews are reliable?

You should read carefully before you write another nonsense. De la Poype was born on July, 28 1920. He was just a young pilot without any serious merits in 1942. Most French communists considered themselves patriots and played a very important role in the Resistance.

"A guy at the tip of the spear cannot be a communist! I swear!" )))))

You are claiming to have insight into this fellow, who you never met. Is this derived from some deep statistical analysis of his personal letters? Or your own predetermined belief?

There is another discussion thread currently active on this forum, which is specifically about the merits of the Soviet air forces which is what you are discussing here. Right now you are just derailing this thread which is about another subject - a specific aircraft type, the P-40. The other thread is here How good was the soviet air force?

 

[Wild_Bill_Kelso]

This came up in another thread but I thought it fit better here. This is from a competitive / dogfight test test conducted in Australia between a Spitfire V and a P-40E, both flown by experienced (I believe Ace) pilots, at various different altitudes. They gave the nod to the Spitfire "especially at higher altitude", but the superior speed, acceleration, diving ability and rolling capability of the P-40E gave it the edge in several of the engagements up to 16,000 ft. It is also highly significant that of the two, the P-40E was the one able to disengage at will, which is a key factor in air to WW2 air combat.

When reading the below also keep in mind that the P-40E had the lowest critical altitude and worst overall performance of all P-40 types, with a critical altitude at ~12,000 ft, compared to ~19,000 ft for a P-40F or ~17,000 for a P-40N.

I was trying to find the original online but could not track it down. Luckily I copied it to my own archive a while back. If the original can be tracked down it is really something that should be on WW2aircraftperformance.org in my opinion.

Anyway, here is the text of that test:

RAAF P-40 vs. Spitfire test
5. Results:
a) Spitfire had the greater rate of climb at all heights - the difference becoming greater as height increased above 13,000ft.

b) Spitfire is far more manoevrable at all heights.

c) Kittyhawk is faster in level speed from 0 to 16,000ft. Above 16,000ft Spitfire is faster and again the difference becomes greater as height increases. Estimated speed advantage of Kittyhawk up to 16,000ft: 0ft - 15mph; 12,000ft - 20 to 25mph; 16,000ft - 5 to 10mph.

d) Kittyhawk accelerates, both in dive and on increase of throttle on the level, far more quickly than the Spitfire.

6) Combat 1 - commenced at 13,000ft (equal height) and lasted for 5 to 7 minutes, in which time the fight was practically a stalemate. At the end of this period height was reduced to 4,000ft when the Kittyhawk pilots decided he had nothing to gain by staying and so broke off by diving away. Thus, in combat up to 16,000ft, the Kittyhawk has the distinct advantage in that the pilot can commence the fight and discontinue it at will. In such a combat the Kittyhawks tactics are to hit and run, and then come again.

7) Combat 2 - commenced at 20,000ft (equal height) and lasted less than 2 minutes. Spitfire quickly gained dominant position on the tail of the Kittyhawk and couldn't be shaken. Kittyhawk pilot broke off by diving away.

8) Combat 3 - Commenced at 16,000ft (height advantage to Kittyhawk) and lasted 14 minutes. Kittyhawk made repeated dive and zoom attacks with the Spitfire alternatively breaking hard to avoid and climbing for advantage where possible. Fight reduced to 9,000ft with neither pilot gaining a decisive advantage.

9) Combat 4 - Commence at 16,000ft (height advantage to Spitfire) and lasted 11 minutes. Spitfire pounced on Kittyhawk and attempted to gain a position on tail. Kittyhawk used speed advantage in first level flight and then shallow dive to gain separation and then climb for advantage. Spitfire countered by climbing hard. Gaining advantage Spitfire used climb and dive tactics to force the Kittyhawk to make repeated diving breaks to avoid. At 7,000ft Kittyhawk used superior roll rate to scissor behind the Spitfire, who countered with steep climb. Kittyhawk then used speed advantage to again gain separation and fight was broken off.

10) Visions - the vision in the Spitfire with the hood closed is better than the Kittyhawk, but it is a definite disadvantage that the hood cannot be opened at speeds above 160mph particularly when searching up-sun.

11) The flying characteristics of the Spitfire make it more suitable for Operations:

a) it is easier to fly.

b) Take-off run is much shorter and so could be operated from smaller landing grounds. Note – the Spitfire does not handle hard dirt strips as well as the Kittyhawk.

c) Mixture and boost are automatically controlled.

d) It is not necessary, as it is in the Kittyhawk, to alter rudder and elevator trims over great speed changes.

All these facts greatly reduce the pilot's problems and so increase his fighting efficiency. The report concluded by recommending that as the large Volkes air filter on the Spitfire cost 20-30mph in top speed, it should be removed in operational service - or at least an alternative found. Also mentioned was the effect of the Spitfires rough paint finish on performance but the general feeling of the report was that the Spitfire was perhaps the better fighter, especially at altitude."

 

[Thumpalumpacus]

 

[Wild_Bill_Kelso]

For context here - The Spitfire used in this test had the dreaded Vokes filter on, this was almost literally an anchor around the neck of the RAF fighters in all the Tropical Theaters - for a while. My understanding is that better systems were eventually developed, but I am not sure when these were implemented precisely.

Also the Spitfire Vwas using IIRC +12 lb boost (hopefully someone will find the document and link it, because I think it specifies) whereas it could use a higher boost in theory, up to +18 I believe. Someone can correct me or provide further details on that.

I believe that by the time of this test, the Australians had already increased the boost on the P-40s, so this P-40E was probably able to use it's maximum WEP boost (at to least "the legal" limit of 57" Hg) which would have given it additional performance boost up to about 8 or 9,000 ft. That may account for some of the speed advantage.

I think, however, the roll and dive advantages of the P-40 were not dependent on the boost settings, and this is mentioned in other Theaters. The disparity was considerably more pronounced with the much slower and draggier Hurricane. The combination of roll+dive was key to

It is also worth noting that the P-40 was more complex to use. It had a few options that not all other planes had, for example something like a 'dimmer switch' control that allowed the pilot to easily use partial flap settings during turns, and the availability of trim tabs including rudder trim. But it was more complex to fly.

Later model P-40s (K, F, L, M, N) did have automatic boost control, though this could be and was sometimes disabled to allow overboosting. By the time of this test a standard WEP setting of 57" or 56" Hg would be normal for most P-40 variants, and 60" for P-40K. The merlin-engined variants could also go up to +16 Lbs I believe.

P-40s were notoriously tricky to handle during a very high speed dive, requiring both a strong leg on the rudder pedal and rapid adjustments to trim, and also experienced torque swing on takeoff. Both of these problems were somewhat alleviated in the later models with a tail fin (early P-40K) and a 30" lengthening of the fuselage (later K and F, all L, M, and N)

 

[PAT303]

Did the Spit in the test have the Merlin 46 engine fitted? they were still running 2850rpm and 9 psi boost when the RAF 45-46 series Merlins were approved for 3000rpm and 16psi boost mid 1942, the Australian 46's finally got higher boost but only to 12 psi in Jan/Feb '43 when RAF MkV LF running Merlin 50 series engines had moved to 3000 rpm and 18 psi boost. RAF MkV LF's would monster a P40 and pretty much everything else at the altitudes that test was conducted at.

 

[Wild_Bill_Kelso]

I don't know, hopefully someone will find the original and post a link for us. I remembered 12 lb boost but I could be wrong.

I believe these were both combat versions, kitted out as they were being used at the time.

And unfortunately I don't know of a test with an LF, they certainly had some advantages, though the P-40 would still roll better at high speeds. And I could also ask for a test with a P-40K or L!

But alas this is the only one of this much detail that I know of.

 

[Wildcat]

I couldn't find the Spitfire Vs Kittyhawk trials but found these documents that you guys might find interesting.
View Digital Image - Spitfire Vs Hap (Plus some combat reports against various aircraft types)
View Digital Image - Comparison between Spitfire Vc and P-40E. Mainly about spitfire tropical filter.

 

[PAT303]

And unfortunately I don't know of a test with an LF, they certainly had some advantages, though the P-40 would still roll better at high speeds. And I could also ask for a test with a P-40K or L!

At the altitudes the test was done at a MkV LF would hold every advantage over the P40 the standard model had over it above 20,000ft, even FW190A pilot's had to bring their A game against all LF models from 1943 onwards, it was the butcher birds menace that caused their development.

 

[PAT303]

I couldn't find the Spitfire Vs Kittyhawk trials but found these documents that you guys might find interesting.
View Digital Image - Spitfire Vs Hap (Plus some combat reports against various aircraft types)
View Digital Image - Comparison between Spitfire Vc and P-40E. Mainly about spitfire tropical filter.

Brilliant find mate.

 

[Shortround6]

And unfortunately I don't know of a test with an LF, they certainly had some advantages, though the P-40 would still roll better at high speeds. And I could also ask for a test with a P-40K or L!

The results would not be much different.

engine..................................gear ratio..............take-off hp...............................hp/altitude/pressure..........................WEP
Allison V-1710-33...............8.77.............................1040........................................1090/13,200/38.9................................................
Allison V-1710-39...............8.80.............................1150........................................1150/11,700/44.6.......................1490/4300/56in
Allison V-1710-73...............8.80.............................1325........................................1150/12,000/42.0........................1580/2500/60in
Allison V-1710-81...............9.60.............................1200........................................1125/15,500/44.5.........................1410/9500/57in

There were a few minor tweaks to the superchargers in the first 3 engines and a change or two in manifolds and the backfire screens went away.
But all three engines were going to act much the same at any given altitude given pretty much the same boost. We know the -33s were over boosted but they never got an official rating. The -73 engine is not going to perform much different at 5000ft than the -39 engine using WEP. Both engines are running at the max airflow the supercharger can provide. At 5000ft the -73 engine can no longer provide the 1580hp power and will be closer to the 1490hp power level.
The -81 engine looses a bit of power down low but has more power in the 7000-12,000ft area, from 12,000ft and up you are probably within 5-6%.
data from manuals do not always agree.
changes in weight may make more difference than the difference in engines between some models of P-40.
Many P-40s flew at over designed weight in combat. Designed weight was for 120 US gallons of internal fuel.

 

[Wild_Bill_Kelso]

The results would not be much different.

For the K, it's debatable (see below). But you didn't show the figures for the F or L which have the Merlin engine.

engine..................................gear ratio..............take-off hp...............................hp/altitude/pressure..........................WEP
Allison V-1710-33...............8.77.............................1040........................................1090/13,200/38.9................................................

Sr6 and some others here will know this, but for those who don't, that is the engine for the P-40B /C / Tomahawk. Critical altitude is 2,000 feet higher than that for the P-40D/E, which may translate to about 18,000' as a max performance altitude. We don't have an official WEP rating though we know for example that AVG and some other units did overboost them. We just don't know a lot of details. But the Tomahawk type, which also had a better climb rate than the early Kittyhawk, may have actually done better in this test against the Spitfire V.

Allison V-1710-39...............8.80.............................1150........................................1150/11,700/44.6.......................1490/4300/56in

Sr6 knows this too, but for those who don't, this is the engine for the P-40D / Kittyhawk I and E / Kittyhawk Ia.
The thing is, you don't get that 1490 HP WEP rating unless they have increased the boost limitations, so we don't know for sure that they did. I think they probably did in the Australian test, but that isn't guaranteed (in a lot of the tests done at Boscombe Down in the UK they used much lower boost settings). When the Kittyhawk I and Ia first went into action in North Africa they used the early manual settings so didn't boost above 44" Hg, which means a maximum of about 1150 horsepower, and no extra speed down low. Once they started using the WEP rating (or overboosting considerably higher) these planes got an extra 340 horsepower available below around 8,000 feet (depending on atmospheric conditions).

This critical altitude of 11,700 feet provides the effective performance ceiling of 16,000 feet in the test.

Allison V-1710-73...............8.80.............................1325........................................1150/12,000/42.0........................1580/2500/60in

This is the engine for the P-40K / Kittyhawk III. This engine is considerably strengthened to endure higher boost, so WEP rating as you see above brings the horesepower up another 90 horsepower down low (below 5,000 ft). That, a slight increase of critical altitude, and an extended fuselage or tail fin (depending on which exact P-40K) which help the pilot cope with torque from the increased power, means that it's arguably just a bit better than the P-40E, I would agree with Sr6. It also has improved machine gun layout which helps prevent gun jams but that wouldn't be relevant for this test. Like the P-40E the P-40K can also be overboosted down at very low altitude (2,000') to close to 70"hg and therefore nearly 1700 hp (so that raises it further to 550 above the original horsepower of the P-40E) and due to the strengthened engine they can do so with a lower risk of blowing the engine, but I'm not sure if they would resort to that in the test since it's already faster than the Spit V at low altitude anyway (and boosting that high is always a risk).

Allison V-1710-81...............9.60.............................1200........................................1125/15,500/44.5.........................1410/9500/57in

This is the engine for the P-40M / Kittyhawk III*, and the P-40N / Kittyhawk IV. This engine cannot safely be overboosted as high as those on the P-40E or K, but it has a critical altitude which is 3,800 ft higher than the P-40E, which means that the fighter is still performing relatively well up to 19,800 feet. This means that the Spitfire would still be in trouble up to a higher altitude. I would say this version would be about 20% better than the P-40E based on a 20% higher critical altitude.

It also translated to being able to outrun Ki-43s and A6Ms at higher altitudes. The P-40M and N also both have the extended fuselage and the improved gun layout of the late P-40K.

* The British called both the P-40K and P-40M Kittyhawk III for some reason.

There were a few minor tweaks to the superchargers in the first 3 engines and a change or two in manifolds and the backfire screens went away.
But all three engines were going to act much the same at any given altitude given pretty much the same boost. We know the -33s were over boosted but they never got an official rating. The -73 engine is not going to perform much different at 5000ft than the -39 engine using WEP. Both engines are running at the max airflow the supercharger can provide. At 5000ft the -73 engine can no longer provide the 1580hp power and will be closer to the 1490hp power level.
The -81 engine looses a bit of power down low but has more power in the 7000-12,000ft area, from 12,000ft and up you are probably within 5-6%.
data from manuals do not always agree.
changes in weight may make more difference than the difference in engines between some models of P-40.
Many P-40s flew at over designed weight in combat. Designed weight was for 120 US gallons of internal fuel.

All true, however many P-40s were also flown stripped when they were being challenged by higher-flying aircraft, and could be as much as 800 lbs below design weight.

The ones you left off are the P-40F and P-40L:

Packard Merlin V-1650..... 2 speed** ........1240 ...............................1100 /19270/??..................1450/2 speed**/60"

** Low speed blower critical altitude is 12,800', high speed blower critical altitude is 18,100', but still making 1100 hp at 19,270' where it achieves top speed.

I don't know what the max boost setting is, so 60" is an estimate (British planes were boosted higher than that with the equivalent engine, i.e. Merlin XX, and the P-51B was boosted to 75" Hg with high octane fuel), but the P-40F and L had the two speed superchargers. Critical altitude in high gear is 18,100 feet, top speed according to a July 11, 1942 test (FS-M-19_1578-A) is 374 mph at 19,270 feet where it is still producing 1,100 hp. This aircraft has a top speed about 20-30 mph faster than a P-40E, and a peformance ceiling of about 22,000 feet, or about 8,000 feet higher than a P-40E. Effectively more if you have a stripped / P-40L type. So I think that would give the Spitfire a bit more trouble, certainly up to a 30% higher altitude.

That was the key difference, i.e the altitude, which made the P-40F and L still viable in North Africa and the Mediterranean long after the Allison engined variants had become too vulnerable to Bf 109G series and MC 202 / 205 for use in the air superiority / fighter escort etc. roles. This is why all five of the US fighter groups operating in the Theater used the Merlin engined variants, P-40F and P-40L.

 

[Wild_Bill_Kelso]

I'm sure you could find LF or other versions of the Spitfire V, using higher boost etc., which could do better against the P-40E, and be at least equal to it even at lower altitudes, though the Kittyhawk did still retain some advantages such as in dive and roll at higher speed, and a big performance boost at low altitude.

The P-40 F and L performed about as well as the Spitfire V in North Africa and Sicily etc., maybe a little better, except above 25,000 ft. The P-40F also had better range which is why they were used for long range escort (the lightened L which only had the 120 gal tanks, was about the same as a Spitfire). As you can see in the Darwin test, WW2 fighter combat has a tendency to move downward if the two aircraft stay engaged. The Luftwaffe and Regia Aeronautica found that if they didn't quickly disengage from Kittyhawks they got into trouble fast. This translated into an inability to impact the DAF bombers and fighter bombers as much as they needed to, and to an inability to protect their own bombers which also translated into problems on the ground.

The Spit VIII in the East, and Spit IX in the MTO were clearly superior to any version of the P-40, though both, especially the Spit IX, still had a somewhat limited range. This was mentioned by both Ki-43 pilots (and the RAF pilots themselves in Shores Bloody Shambles III).

 

[PAT303]

The Spitfire had one handicap verse's every other aircraft and that was the RAF's refusal to fit aux tanks, the fact that it was replaced by lesser aircraft that did have the fuel to get to the fight was mindboggling in my mind, as per the Darwin test the lower the the Spit went the worse they became because the merlin 46 was a purpose designed high altitude engine, low altitude, low boost, trop filter and overall poor condition made both the A6M and P40 look good in comparison.

 

[Wild_Bill_Kelso]

I have gone back and forth on this a few times, but I keep being told that they did in fact fit auxiliary tanks to the Spitfire, is that not the case? I mean, jettisonable and not 'slipper' tanks.

I wouldn't feel too bitter about the comparison to the P-40 and the Zero, they were both quite good fighters. As was the Spitfire, but it was designed to be an interceptor, not an escort fighter. P-40 doing better at lower altitude probably had at least as much to do with characteristics of the P-40 as of the Spit, which may not have had a Merlin 46. Not all Spitfire Mk Vs did. Until somebody has a link to the original test I don't know which engine it had.

 

[Shortround6]

The ones you left off are the P-40F and P-40L:

Packard Merlin V-1650..... 2 speed** ........1240 ...............................1100 /19270/??..................1450/2 speed**/60"

** Low speed blower critical altitude is 12,800', high speed blower critical altitude is 18,100', but still making 1100 hp at 19,270' where it achieves top speed.

I was trying to show the difference between the Allison engines, which was not that much. The -33 engine was good for 1040hp at at 14,300ft. The 1090hp at 13,200 is just a different way of rating the same engine. It does show the lack of progress with the Allison engine in the supercharger dept. The 1943 engine was good for 85 hp more 1,200ft higher than the 1940 engine. Unfortunately the P-40N-5 and later went about 1000lb heavier than the P-40B. The 200 P-40N-1s (the famous N strippers) were about 600lbs lighter when they left the factory. In service they often gained several hundred pounds back. For some weird reason/s the using squadrons wanted the ability to at least try to start the plane using the internal battery.
They kind of liked having more range than the P-39 and installed the forward fuel tank.

Once you get into that 12,000-16,000ft area there wasn't a lot to choose between the different Allisons. 5-6%? The -39 and -73 engines were even closer to the -33 than the -81 engine.

The big differences were down at 2500-9500ft and depended on what boost you could use. The 8.80 geared engines topped out at just under 5000ft and dropped over 300hp by the time they got to 11,500-12,000ft.

The "rated" altitude/s for the Merlin used in the P-40s was 1240hp/11,500ft (about 90hp more than the -39 engine at just about the same altitude) and 1120hp at 18,500ft. or the same power as the -81 engine 3000-3500ft higher. This was using 9lbs of boost (about 48in). In Dec 1942 they approved 61in of boost, unfortunately the pilots manuals have a misprint (at least early ones) and they copied the take-off power rating. Please note there is difference between the Merlin used in the P-40s and all the British 2 speed engines. The British engines used either 16lbs in low gear (62in?) and 14lbs in high gear (58in ?) or they used 18lbs in both gears in later versions of the engines. Please note that the 18lbs boost engines were rated at lower altitudes, if they flew at the same altitudes as the early engines they gave the same power.

Basically the F & L were the only hope the P-40s had of contesting the airspace above 15,000ft.

 

[Wild_Bill_Kelso]

I was trying to show the difference between the Allison engines, which was not that much. The -33 engine was good for 1040hp at at 14,300ft. The 1090hp at 13,200 is just a different way of rating the same engine. It does show the lack of progress with the Allison engine in the supercharger dept. The 1943 engine was good for 85 hp more 1,200ft higher than the 1940 engine. Unfortunately the P-40N-5 and later went about 1000lb heavier than the P-40B.

It also had considerably more horsepower...

The 200 P-40N-1s (the famous N strippers) were about 600lbs lighter when they left the factory. In service they often gained several hundred pounds back. For some weird reason/s the using squadrons wanted the ability to at least try to start the plane using the internal battery.

They kind of liked having more range than the P-39 and installed the forward fuel tank.

The 200 P-40N-1 were not the only N subvariants that came 'stripped' out of the factory, but much more importantly, the P-40N were generally configurable in the field to either light / "interceptor" configurations - 4 guns, less armor, sometimes less fuel... or heavy with a wide variety of extra gear ranging from FB missions with extra bomb and rocket racks, to higher altitude escort missions with extra radios and direction finders, and a variety of other configurations. Loaded weight for a P-40N could vary by 1,500 lbs not counting ordinance.

They made very similar series of changes in the field with P-40Fs, which is what the P-40L actually came to emulate, it just came out of the factory with the field modifications already done. Which were sometimes put back in place depending the type of missions they were flying.

Some of the lightening changes for the P-40N were unpopular, like the external starter, some were not even really noticed and certainly never reversed, the like the lighter aluminum vs. previously brass radiators. Not sure about the lighter wheel hubs.

I think you probably know all this already though.

Once you get into that 12,000-16,000ft area there wasn't a lot to choose between the different Allisons. 5-6%? The -39 and -73 engines were even closer to the -33 than the -81 engine.

The big differences were down at 2500-9500ft and depended on what boost you could use. The 8.80 geared engines topped out at just under 5000ft and dropped over 300hp by the time they got to 11,500-12,000ft.

The -81 engined P-40s had about 5,000 feet higher effective altitude. Just about 20,000 feet. This, in the lighter configuration, proved to be crucial for some units like the 80th FG which sometimes flew escort missions over 'The Hump' on the way into Burma.

The -39 and -73 engined P-40s, conversely, actually had a considerably lower critical altitude than the earlier Tomahawk types. As you can see in the numbers I posted above.

Again I don't think this is actually news to you because you yourself pointed the altitude advantage of the P-40M compared to the K in some other argument on here

The "rated" altitude/s for the Merlin used in the P-40s was 1240hp/11,500ft (about 90hp more than the -39 engine at just about the same altitude) and 1120hp at 18,500ft. or the same power as the -81 engine 3000-3500ft higher. This was using 9lbs of boost (about 48in). In Dec 1942 they approved 61in of boost, unfortunately the pilots manuals have a misprint (at least early ones) and they copied the take-off power rating.

Do you have a source for the official approval of 61" boost?

Please note there is difference between the Merlin used in the P-40s and all the British 2 speed engines. The British engines used either 16lbs in low gear (62in?) and 14lbs in high gear (58in ?) or they used 18lbs in both gears in later versions of the engines. Please note that the 18lbs boost engines were rated at lower altitudes, if they flew at the same altitudes as the early engines they gave the same power.

Basically the F & L were the only hope the P-40s had of contesting the airspace above 15,000ft.

I think F & L were clearly the best at "contesting the airspace" at higher altitudes, but that was about 22-23,000 feet.

The differences between the Allison types were as I listed in my post up above.