P-39 vs P-40 (1 Viewer)

[P-39 Expert]

I think most of us will agree:

1. The P-40E was just too heavy to have good (or any) high altitude performance due to excessive weight. And there was no way to effectively cure this situation. Low, medium and high altitude being arbitrarily defined as under 10000' is low, 10-20000' is medium and over 20000' is high altitude. And not much combat at all was done over 8000 meters or 26500'.
2. Any engine should not be overboosted in ANY situation unless absolutely necessary for survival, they didn't call it WAR EMERGENCY POWER (and limit to 5 min) for nothing.
3. There were very few "low altitude" fighter planes manufactured as such. Air forces needed planes that could fight at all altitudes. As the war progressed and planes got engines with higher altitude capabilities the (normally older) lower altitude planes were relegated to lower altitude duty such as ground attack and escort of medium bombers/transports that flew under 15000'.
4. The P-40E did reasonably well in combat, but were normally employed in secondary theaters against lesser fighters past their prime. P-40Es didn't escort B-17s at 25000'.

The P-40 was not optimal but did yeoman's duty at a time when we had nothing else.

 

[Schweik]

I think most of us will agree:

Lol

1. The P-40E was just too heavy to have good (or any) high altitude performance due to excessive weight.

Considering that it was lighter than a P-51 I think this is demonstrably incorrect.

2. Any engine should not be overboosted in ANY situation unless absolutely necessary for survival, they didn't call it WAR EMERGENCY POWER (and limit to 5 min) for nothing.

Again, incorrect. The issue here is that what was originally considered WAR EMERGENCY POWER as you so exuberantly put it later became normal military power settings, usually as the result of such settings being tested in combat. These were in turn routinely used in P-40s for example for climbing to altitude, and for extended periods exceeding 15 minutes. We know that the original WEP setting for the P-40E as established by Allison was overly conservative at 45" Hg. We also know that this was later officially remanded to 56" Hg and then to 60" Hg, per Allison Aircraft corporation memos.

Aside from the Allison memo already posted in this thread twice (once by myself and once by another poster) I call your attention to this Air Force memo about the Allison Engined P-51. It reports that in British service, Mustangs using the same Allison engine that the P-40E had (V-1710-39) reported that they were able to run 20 minutes at 72" Hg without hurting the engine and averaging 1500 hours between failures. This had become their routine tactic when disengaging from daytime intruder raids over occupied France and Holland. The official rating of 45" was quickly left behind as it was a mistake, in fact it later became the new military power setting for Kittyhawks. Quoting directly from Brigadier General Charles F. Born:

"This aircraft is powered with the Allison 1710-39 engine having a rated power of 1150 H.P. at 3000 R.P.M. and 44" Hg. at 12,000 ft. The engine was originally equipped with an automatic boost control limiting the manifold pressure at the lower altitudes to 44". The British remove this so as to get the vastly increased performance at lower altitudes thru the judicious use of over-boost.

In view of the British operation and the fact that we have an approved war emergency rating on the 1710-39 engine of 56", it is suggested that immediate steps be taken to remove the automatic boost controls from our P-51 airplanes in this theatre* and that the instrument dials be marked with the proper lights. The British have operated at full throttle at sea level (72" Hg) for as much as 20 min. at a time without hurting the engines. According to them, the Allison is averaging 1500 hours between bearing failures as compared to 500 to 600 hours for the Merlin. The Allison, they have found, will drag them home even with the bearing ruined. "

* RAF and RAAF squadrons were removing automatic boost controls from Kittyhawks in 1942 for the same reason.

The only real debate here is how soon did they figure this out and how widely was it spread, did it require special (British) fuel etc.

3. There were very few "low altitude" fighter planes manufactured as such. Air forces needed planes that could fight at all altitudes. As the war progressed and planes got engines with higher altitude capabilities the (normally older) lower altitude planes were relegated to lower altitude duty such as ground attack and escort of medium bombers/transports that flew under 15000'.

Disagree as I have already pointed out in depth.

4. The P-40E did reasonably well in combat, but were normally employed in secondary theaters against lesser fighters past their prime. P-40Es didn't escort B-17s at 25000'.

Again, demonstrably incorrect. This seems to be another persistent myth related to the Med theater which we have alreeady discussed this at length in this forum. The Mediterranean and North African Theaters had recieved the best available German fighters as soon as they were available precisely because of problems older / lesser fighters (Bf 109E and Bf 110, MC 200 etc.) had dealing with earlier Tomahawk type P-40s. By Dec 1941 Bf 109F2s were on site, then Bf109F4s as soon as they were available, and by the time the Americans had arrived to join the fighting in Tunisia, Bf109G2 and G4, and then increasingly G6 (which were probably not as good as F4s actually but they were the newest)

If necessary I can post the TO&E of the Axis forces in the Med but I believe I already did post them in another thread here for some month, I believe Oct 1942, I'll see if I can find it.

Same for the Russian front which again, we debated here at length previously. The Germans were putting their best fighters into action in Russia and had converted over to the F2s and F4s by the time the Kittyhawks were in action.

And in the Pacific of course the Japanese were using their best aircraft - the latest A6M and Ki-43 variants, Ki-61 and Ki-44. In Burma, in another old thread on here someone posted data about successful engagements between P-40s and Ki-84s and some other late war Japanese fighters.

The P-40 was not optimal but did yeoman's duty at a time when we had nothing else.

Can't disagree though it's a vague and rather meaningless cliche. You could say the same about basically every fighter - though they did have other options (like the P-39 and the Hurricane) but the P-40 turned out to be the most useful.

S

 

[Schweik]

Here is an anecdote I had previously posted to another thread, which refers to overboosting in P-40F or L models, which according to the pilot enabled him to keep up with and then outrun Bf 109s he was facing. This is all directly from P-40 Aces of the Med (Osprey), page 16:

Another 64th FS [57th FG] pilot taking part in the 9 October mission was 1Lt George D Mobbs, who had a much rougher time of it. He recorded this description in his diary:

'We got mixed up and got to the landing ground ahead of the bombers, but went in to strafe anyway. That is, most of us did. I was on the outside, and just as we started to go down, for or five '109s started to attack me. I turned into them and got a short burst at one, but it was a 90 -degree deflection shot. Three of them kept attacking me, and I kept evading them, and occasionally getting a shot. Meanwhile, the rest of our aeroplanes had gon in to strafe and then flown out to sea, but I couldn't join them because the three German fighters kept on attacking me.

I was running the engine at 55 to 65 inches of mercury and 3,000 rpm, so I could pretty well stay with them. They would keep alternating the attacks between them. After a few minutes I got on one of their tails and was overtaking him. I didn't open fire until i was about 100 yards from im. I gave him a squirt and nothing happened. I moved over a little and changed my sighting, and on about the third burst his aeroplane burst into flames and fell off to one side. i was going to watch him go down so i would have a chance of getting credit for one destroyed, but one of the other jokers attacked so i was busy evading him. However, I spotted the first one moments later a few hundred feet below me, still spiraling down, but I never got another look at him after that.

I was still in a hole. The other two kept attacking, one after the other. Later, I got a few shots at one from directly behind and slightly above as we were diving. I could see the aeroplane jerk each time I pulled the trigger but saw no debris or fire from it., and I was driven away by the other one. attacking. I must have hit the Jerry, because I never saw him again.

Now I just had one to worry about, but on his next attack I finished my ammunition. He kept following and attacking, but with just him to worry about, I was making pretty good time back toward our lines. On another attack we met head-on, and I didn't think he fired his guns. I didn't see them, anyway, and i was already out of ammunition.

We were down pretty low by then - 1000 ft - and the German ack-ack had opened up at me. But I was going so fast that they were shooting behind me. I had everything forward. I was running awfully hard, and the ack ack was getting pretty close to the Jerry behind me. It was kind of amusing, becuase it looked as if I was going to make it back if my engine didn't quit. We were so low that I could see the ack-ack gun emplacements below.'

In fact the engine in 1Lt Mobbs' P-40F did hold together and the Bf 109 gave up the chase. The American returned safely to base, where he was awarded one Bf 109 probably destroyed for the mission. Four days later, Mobbs recorded his first of four confirmed victories during a scrap with 20 Bf 109s over El Alamein. "

I checked this incident in Shores MAW. From the previous anecdote, I concluded the following:

1. Based on the German records, Lt. Mobbs 'damaged' claim may have been a victory after all. Possibly making him an Ace since he had 4 confirmed later in his tour. Its hard to say for sure but Germans lost three fighters in that area at the same time - the victories may have been from RAF Kittyhawks. The other LW loss was later and in a different area.
2. This is a clear example of overboosting to 55" - 65" Hg. You can certainly understand why.
3. It sounds like he was alternating from 55" to 65", both settings would be considered WEP, and the fight appears to have lasted much more than 5 minutes though it doesn't indicate precisely how long it actually was.
4. He was able to hold his own fighting three Bf 109s from the elite JG 27 unit, possibly shoot at least one of them down and then outrun another.
5. From all this I conclude that using overboost, P-40F could outrun Bf 109F-4 (Trop) at low altitude
6. I also conclude P-40F was at least an even match with the Bf 109F-4 (Trop) at low altitude, maybe a little better.
7. German overclaiming is notable in both incidents and by a wider margin than Allied claims. 4-1 LW vs 2-1 for DAF on Oct 9, and 2-1 LW vs 4/3 DAF on Oct 13.

It is also possible that he was actually fighting MC 202s or that he made it all up. But considering that his victory 4 days later over another bf 109F-4 it seems to be legitimate and backed up by German records I doubt it.

 

[Schweik]

I found the posts where I previously broke down all the activity for a specific month of combat in the Med, Oct 1942.

The combat numbers showing claims vs. actual losses for the month can be found here
The TO &E for both sides and more data for the month can be found here

Summary of the latter is as follows:

DAF Fighters
(This is theoretical strength not counting aircraft down for maintenance / damaged etc.)
336 fighters (155 front line fighters - including 48 Spit Vs and 107 merlin engined P-40s, 194 older fighters - Hurricanes and older P-40s, plus 32 fighter bomber only Hurricane IID)

Axis Fighters
Axis Fighters
(German Data for August 1942 per Shores - this is supposed to be real on-hand air strength)
Axis 515 fighters (307 front line Bf 109 and MC 202, 150 biplanes and 12 bf 109E Jabos, 46 Bf 110). Most of the heavy lifting though was being done by about 100 Bf 109s.

This includes specifically 76 Bf 109F-4 (plus ~ 12 in III./JG 53 and a few more in the Jabo Staffl) and 210 Macchi MC. 202

JG 2 (Fw 190A-3 and A_4) arrived on 16 November with a further 24 fighters.

So I think this shows that Axis Air Forces in the Theater were neither outnumbered nor using second rate fighters, hopefully helping to debunk that particular persistent myth.

S

 

[Shortround6]

The P-40D had a production run of 583 aircraft, 23 went to the US, 560 went to the RAF. Only the first 20 sent to the RAF had 4 guns, I think all of the American ones did. However some were used in the field (in North Africa) with four guns and some with six.

SO total production of 4 gun P-40D/Es was 43 planes and over half never saw combat? Like I said, the 4 gun P-40D is a moot point.
Except if you can find performance data for it to show any difference from the 6 gun P-40D/E. For the D the planned ammo went to 1000 rounds for 4 guns vs 1410 rounds for the six guns so the weight savings wasn't quite what you might think. They also made provision to hold up to 2460 rounds for the 4 guns so the planned max weights actually don't wind up very far apart. designed gross weight for a D being 7944lbs while a E was supposed to go 8011.5lbs, max gross was 8777.5 for the D and 8845lb for the E.
This is from the "Operation and Flight Instructions Handbook" of 1941. Designed gross weight was with 120 US gallons of fuel.

You are making a ton of assumptions here as to what I meant, why not just ask before you go off on a tangent? It gets weary spelling every single thing out and my posts are too long as it is but if I don't cover every possible nuance of what I mean I get this sort of thing.

To clarify: I was just referring to over-revving the engines (reported by the Russians) and overboosting the engines. I believe this is what Australian P-40 double ace Bobby GIbbes meant when he said "later when we got our Kittyhawks running properly - were getting better performance - they were a better aeroplane."

I have to make assumptions when you use such vague terms as "tinkering". Over Revving and over boosting are NOT tinkering. They are abusing the engines and will shorten engine life and increase breakdowns. Going to 3200rpm instead of 3000rpm increases the stress on the reciprocating and rotating parts by about 13.7% since the increase in stress is proportional to the square of the speed. Over boosting is more liner. The factories were well aware of the increased forces involved.

I have tried to show that due to the changes in the engines and due to changes in the fuel the allowable boost could be increased over time (experience) to higher levels.
If you want to believe that such high pressures could have been used form the start regardless of fuel availability then nothing I can say will make any difference.

We have been over this before. They took out fuel, fuel tanks, a pair of guns, and some armor that you don't think existed.

Actually from what I understand they sometimes took off with two guns and less than half fuel. Not just with P-40s they did it with Hurricanes too. I'm just repeating what the sources say they did./QUOTE]

Not filling tanks is quite understandable. Especially since they were never intended to be fully filled in the first place ( rear tank behind pilot held 62.5 gallons when full. design gross weight called for only 37 gallons in that tank). yanking a fuel tank is quite a bit tricker even if those rubber self sealing tanks were heavy. I am sure any mechanic in the squadron who was worth anything at all could open up the hatches/panels and disconnect the tank and drop it out. The problem was with fuel management and balance (Center of gravity)
The forward wing tank held 32 gallons and was called the reserve tank. It was also the tank used for starting, warming up and take-off, this was because the fuel system was designed to return any excess fuel from the carburetor to this fuel tank in flight rather than venting it overboard. Once take-off to a safe height (for switching fuel tanks ) was achieved the fuel tank selector was changed to a different tank and this tank was not used again until the other tanks were exhausted. IF this tank is pulled in field (and this was the tank taken out by the factory on the P-40N-1) you need to replumb the fuel system to allow the overflow fuel to go to another tank, you also need to install a 2nd fuel feed point in the the other tank which will drain from a higher point than the existing fuel feed point to sue as the "standard" fuel feed while the old fuel feed now acts as the 'reserve'.
The main tank (rear wing tank) of 51/52 gallons capacity is the most likely candidate for this. Shorter fuel lines and closer to the center of gravity. Taking out the main tank leaves you with little fuel unless the rear tank is full and flying with the rear tank full and the middle tank empty or missing might be skating a bit close to the edge for safe flight. Please not the P-36/Hawk 75 had roughly the same (or more) total fuel capacity but it's normal gross weight was figured with only 105 gallons. None of it the rear tank. The P-40F changed the order and or amounts of fuel used from the tanks in order leave several hundred pounds of fuel in the rear tank as long as possible to balance the heavier Merlin engine.

The factory could and did move certain other parts around to help balance the plane out when they made major changes.

as far as the armor goes, maybe they did take out a plate and maybe they didn't. The P-40D/E is listed as having 108.5lbs of armor. I don't know if this includes the B/P glass or not (it did on the P-40C) but even if it doesn't there sure isn't a great deal of weight to take out if you leave the armor behind the pilot in place. Yanking 20-30lbs of amour out of a 8000lb airplane is more phycology for the pilot than actual improvement in performance.

Charts for the P-40E show a climb to 5000ft of 4.8 minutes at 44.6in/3000rpm and 8100lbs (clean) and cutting the weight to 7500lbs cuts the time to 4.4 minutes. after 5 minutes the chart drops the power to 2600rpm and 38.5 in. If cutting 600lbs out of the plane improves the climb by around 10% then taking out out a 30-40lb piece of armor is going to have little or no measurable effect.

I know we have had this debate before too and you side with the manufacturers, I'm not pitting one against the other in this comment, I'm just pointing out that the

The issue was usually that the engines (in every country) took longer than expected by the aircraft designers to achieve the promised power output and the airframe inevitably had to carry more weight in fuel, ordinance, radios, batteries, fire suppression gear, armor and self sealing fuel tanks and other "unexpected" things which quickly put the plane over the tipping point. Manufacturers also had to do a fair amount of fine tuning which took a while to get the best speed out of a new airframe, and they were often struggling to reach performance benchmarks while trying to meet demands for extra gear.

And then they were often stripped of extra things in the field by resourceful crews and the pilots themselves responding to battlefield conditions. Sometime that happens faster with a foreign aircraft. That is what the Finns did with the Buffalo and it's what the Russians and RAF and Australians did with the P-40. By the time Americans were engaged in the Med they followed suit.

It is not a question of siding with the manufactures, it is that your perception of history is a bit skewed. In 1938 very few governments were requiring heavy armament, or armor, or self sealing fuel tanks. By the summer of 1940 many of them were, By 1942 even the Japanese were beginning to fit such things. For the British, Americans, Germans and Russians any plane that started design work after 1940/41 had all of those things in the initial requirement and the plane was sized accordingly and the engine selected from those deemed appropriate (some times due to production considerations or perceived role) . Planes designed before 1938-40 and were kept in production had to have all those things added. It was Not a question of the plane designers designing a "light" version of the aircraft that lacked operational equipment to suit the engines at hand and planning to go back and redo everything when more powerful engines did become available.
Some plane makers over promised in order to get contracts (Bell comes to mind pretty quickly). The P-39 was going to need an extra heaping helping of power from an engine made of helium to meet it's promised performance numbers (they flat out lied).
For the British the Spitfire started to enter squadron service at the end of 1938. The 20 mm Hispano cannon was about 1 1/2 years away from going into large production. The Merlin III engine was NOT going to give any more power without changing from the 87 octane fuel to the 100 octane. and so it goes, please show an aircraft program that supports your contention. Allison did muck up the initial fitting of 9.60 gears that could have given P-40M/N performance at altitude in the Spring of 1942 but hat is well after the P-40D/E was ordered.

And the Finns did next to nothing to the Buffaloes they got. The 239 model was the export version of the F2A-1 and they never had self sealing tanks or armor or some of the other stuff you list, so the Finns, smart and tough as they were, could NOT take out stuff that wasn't there.

For fighter vs. fighter combat incidentally I do think four .50 cal guns were enough, which is why it was standard for a while for P-40F pilots to remove two guns during the heaviest fighting in Tunisia -

And here again we see the use of the retrospectoscope. Because by the time of Tunisia the .50 cal Browning had existed in it's fast firing form for around two years vs the prototype or trails versions (if you are lucky) that existed in the spring/summer of 1940. 60 rounds per second from 6 of the old guns at best. 48-56 rounds per second from four of the new guns.
In 1940 the US had no incendiary ammunition available although they were working on it. By late 1942 it was general issue (20% or better?)
I am not sure when the US changed the velocity of the ammo from around 2500fps to over 2800fps but the British were buying the slower stuff from several US sources in 1940. The new stuff was approved but there is a big difference between approved/starting production and being available for use in remote parts of the world.

 

[Schweik]

I care.
Typhoon was well able to compete with Fw 190 at 15000-20000 ft as it was the case for 5000-7000 ft, while P-40 was not capable on taking on Fw 190s at 15000-20000 ft.

Lol Ok I'll start another thread to compare P-40 to Typhoon, I think I will be vindicated though I don't know the operational numbers for the Typhoon.

Which is the better low level fighter, P-40F or Typhoon?

2-stage engines don't require any rare materials above what it was usualy used on engines' superchargers. Soviets experimented with hi-alt fightes already in 1930s, adding turboes at I-16 for example, while in ww2 they were designing 2-stage supercharged versions of VK-105 (overheated alot, so they later added ADI; still produced in penney packets only), as well as with intercooled AM-37. Plus turbocharged MiG fighter prototypes, all of whose were to fight high flying German recons and bombers.

I think here is part of the nexus of our actual disagreement. Of course the Soviets would want to have the capability to make high altitude fighters, just in case they needed it, and as I already pointed out before, they were given Spitfire Mk IX in 1943 so they undoubtedly could have reverse engineered two stage superchargers if they had felt it was a high priority. But I think it's clear that they didn't need it. The MiG-3 had good high altitude performance but was very disliked because of it's poor showing down low where all the real fighting was. Sure shooting down Ju 86s and higher flying medium bombers (which did do some serious damage early in the war) was good to have, but the main emphasis of the VVS was on coverage of ground operations at the front.

The cost of two stage engines in terms of materials may seem negligable from a Western perspective but Soviet aircraft design emphasized the use of as few as possible metals and any strategic materials including aluminum (which is why so much of so many of their fighters were made of birch plywood). Two stage engine means two impellers, possibly a whole second supercharger, plus an intercooler. That also undoubtedly increases maintenance costs. These things mattered to the Soviets - they would have done it anyway if they thought they needed a lot of high altitude fighters, but they clearly did not. There was routinely a cloud ceiling at 5,000 feet or less, and all the fighting that mattered centered around the tanks and Tactical ground targets. To wit...

The La5FN managed to barely emulate Fw 190A1 and Bf 109F-4 performance 2 years later, dito for Yak 3. Fighters that were useless at 28000 ft probably can't be considered when talking about best fighters, ditto for fighters that are inable to fly 400-500-600 miles away, fight well, and return the said amount of miles. All while having half of firepower of many Western or Japanese fighters

Well this is a German or Western oriented point of view that is a bit of an outlier - I think most WW2 aviation experts recognize that the Yak-3 was one of the superlative fighters of the war. The La 5FN was certainly considered such by the Soviets themselves, the Germans claimed not to think much of it, but I believe in terms of performance where it mattered, both aircraft outperformed their contemporaneous opposition to a sufficient extent that German aircraft casualty rates jumped up substantially in coincidence with their arrival. Of course the reasons would be debated - was it because of more aircraft or better aircraft or both? I would say the latter since numbers didn't make the difference when the Soviet pilots were flying I-16s and LaGG-3s. Soviet supply and maintenance situation did improve of course, while the German situation declined, but I don't think that is enough to explain it.

The bottom line is would a P-51 have been better for the Russian Front? I would say definitely not. The Spitfire wasn't either, clearly or they would have used it there instead of in PVO units. And arguably the best high altitude fighter they had, the P-47, was considered unsuitable for combat even for PVO.

S

 

[Schweik]

SO total production of 4 gun P-40D/Es was 43 planes and over half never saw combat? Like I said, the 4 gun P-40D is a moot point.

You need to fix one of the quote tags on the second part of your post.

 

[KiwiBiggles]

The La5FN managed to barely emulate Fw 190A1 and Bf 109F-4 performance 2 years later

1941 performance in 1943? Undergunned by European standards? Sounds like the F6F to me.

 

[Schweik]

I think it's much more just a difference in air combat philosophy. And incidentally, this is yet another reason why the Soviets liked the P-39. Take the wing guns off (as they did) and you have a fighter armed just like a mid-war Soviet fighter - armament in the nose, with a punch.

Soviet fighters were armed a lot like Marseilles era Bf 109s - relatively few guns all in the nose, for precision.

Is it better to shoot 1,000 .303 rounds from medium distance, or 700 12.7mm rounds to kill a target from far away or 15 cannon shells from right up close? Both approaches have their advantages, but the Soviets clearly liked the latter better for a variety of reasons and it did work.

 

[Shortround6]

The cost of two stage engines in terms of materials may seem negligable from a Western perspective but Soviet aircraft design emphasized the use of as few as possible metals and any strategic materials including aluminum (which is why so much of so many of their fighters were made of birch plywood). Two stage engine means two impellers, possibly a whole second supercharger, plus an intercooler.

2 stages means two superchargers, you can put both superchargers in the same basic "housing" or case but each impeller needs it's own diffuser and you need ducting/pipes so that the first supercharger dischargers into the intake of the second super supercharger.

Well this is a German or Western oriented point of view that is a bit of an outlier - I think most WW2 aviation experts recognize that the Yak-3 was one of the superlative fighters of the war. The La 5FN was certainly considered such by the Soviets themselves, the Germans claimed not to think much of it, but I believe in terms of performance where it mattered, both aircraft outperformed their contemporaneous opposition to a sufficient extent that German aircraft casualty rates jumped up substantially in coincidence with their arrival.

Or an honest appraisal?

The Yak 3 doesn't show up until until around D-Day. If you have a bunch of people saying the P-51 didn't show up until all the heavy work was done where does that leave the Yak-3?
It is pretty much a one trick pony. If what you need is a short range low endurance dogfighter at under 12,000ft or so , then yeah, it is a pretty good fighter, if you need to do anything else then you are are out of luck. By low endurance I mean short combat persistence. You are out of ammo after about 13 seconds for the `12.7mm machine guns and the 20mm runs dry just before that. Not bad for 1941/42 but this is 1944.
Russian 20mm cannon is not one of the wars finest. The gun itself wasn't too bad but the ammo was low powered, firing a light projectile of limited explosive power.

It goes back to what the Russians were actually able to build, not what they wanted. With a Klimov VK-105PF engine you have to make some very definite choices as to what you want the fighter to do. Attempts to use higher powered engines (the VK-106 and VK -107) showed no results until after the war. Post war the availability of the much lighter Berezin B-20 cannon did increase the fire power even though it shortened the firing time.

Russian views of the aircraft they used are no less biased that western views. Praising Western lend lease equipment too highly could get you a very, very long winter vacation.
Two synchronized ShVak cannon on the LA-5 were hardly world class armament either, at least with 200rpg you didn't run out of ammo as fast as the Yak 3.
Needing 2-3 aircraft to get the same amount of guns/ammo into the air as the Western planes is hardly brillant planning, even if it is good design given the available engines and fuel.

 

[Schweik]

One other thing I forgot to add - 56" Hg on the V-1710 -39 in the P-40E apparently means 1,470 hp at sea level. I don't know what the critical altitude is from there but that is pretty good performance down low, a big jump from 1,150 and more than enough I would say to compensate for the weight of the airframe. Seeing as how they were routinely able to run at 72" (and 1780 hp) for 20 minutes, I would say it's a safe bet (though I do not have any direct proof) that they could run at 56" for at least that long and almost certainly did. But it still doesn't help at 15,000' let alone 25,000'.

P-40 pilots also mentioned using WEP for routinely climbing up to altitude, so it clearly wasn't that "extreme". I'll try to track down that quote and post it later.

Shortrun, I find it a little hard to read your post 225 due to the quote tag but I get the gist of your argument, and I acknowledge - we don't know precisely when, or where they started using higher power settings on P-40s. We do know they were using them in Australia and the Middle East by Dec 1942 but by then the P-40E is almost done as a frontline fighter. So this is the main thing left to find out about this whole issue IMO.

You seem to emphasize that field units wouldn't know how to handle all the necessary changes needed to get the better performance without wrecking engines or screwing up C.O.G. / balance and so on. I grant you that certainly the average high school educated mechanics probably did not have anywhere near the capabilities of Curtiss Inc engineers. What they did have was intense motivation since when the P-40E was introduced to combat in early 1942 it really had to hit the ground running as Allied air units in Java and the Philippines, in Moscow and Leningrad, in Egypt and Libya were under heavy enemy pressure and were basically getting slaughtered with their entire armies in existential crisis, and all Allied aircraft types suffering immense casualties. So presumably some of them found the expertise they needed somewhere and figured a lot of things out in very short order.

We know that various Allied Air forces stabilized a catastrophically bad situation in the early months of 1942 in large part using P-40s - specifically P-40D and E in that critical period (as well as Wildcats, Yak 1s, Hurricanes etc.), and we know at some point changes to engine operation and lightening of the aircraft were both part of the solution they found - along with new training and tactics and all kinds of other things.

Then P-40Ks that showed up in combat zones in mid 1942 were basically factory improved souped up P-40Es and they helped a lot - appparently in particular in Russia where several of the top P40 aces flew this specific subtype, as well as in the CBI and in the Pacific where you also see many Aces flying P-40Ks.

We also know specifically when it came to the Merlin engine P-40s the factory was catching up with the young mechanics at the front in modifying the P-40L to match the field modifications of the P-40F (which did, incidentally include removing the front wing fuel tanks). I agree removing 30 lbs of armor would not make a significant difference alone. But removing two .50 cal guns, 600 rounds of ammunition (P-40L loadout was 201 rounds per gun instead of 240-312 per gun, with six guns, of the factory issue P-40F), two rubber lined fuel tanks, and bomb shackles, and one of the radios, and some fuel, and thirty pounds of armor did make a difference as it apparently decreased the loaded weight down to 8020 lbs, which is a drop of 460 lbs from the standard loaded weight on the (six gun) P-40F.

S

 

[Schweik]

2 stages means two superchargers, you can put both superchargers in the same basic "housing" or case but each impeller needs it's own diffuser and you need ducting/pipes so that the first supercharger dischargers into the intake of the second super supercharger.

Gotcha, yeah that makes sense.

Or an honest appraisal?

The Yak 3 doesn't show up until until around D-Day. If you have a bunch of people saying the P-51 didn't show up until all the heavy work was done where does that leave the Yak-3?
It is pretty much a one trick pony. If what you need is a short range low endurance dogfighter at under 12,000ft or so , then yeah, it is a pretty good fighter, if you need to do anything else then you are are out of luck. By low endurance I mean short combat persistence. You are out of ammo after about 13 seconds for the `12.7mm machine guns and the 20mm runs dry just before that. Not bad for 1941/42 but this is 1944.
Russian 20mm cannon is not one of the wars finest. The gun itself wasn't too bad but the ammo was low powered, firing a light projectile of limited explosive power.

It goes back to what the Russians were actually able to build, not what they wanted. With a Klimov VK-105PF engine you have to make some very definite choices as to what you want the fighter to do. Attempts to use higher powered engines (the VK-106 and VK -107) showed no results until after the war. Post war the availability of the much lighter Berezin B-20 cannon did increase the fire power even though it shortened the firing time.

Russian views of the aircraft they used are no less biased that western views. Praising Western lend lease equipment too highly could get you a very, very long winter vacation.
Two synchronized ShVak cannon on the LA-5 were hardly world class armament either, at least with 200rpg you didn't run out of ammo as fast as the Yak 3.
Needing 2-3 aircraft to get the same amount of guns/ammo into the air as the Western planes is hardly brillant planning, even if it is good design given the available engines and fuel.

I can't really disagree with any of this. I guess what Tomo and I are arguing about at this point is whether generalist aircraft are always better than specialized aircraft or not. My answer would be "it depends."

For the Soviets I would say that specialized aircraft were what they wanted and I think they were correct. You are also correct that they were facing some severe limitations to their inline engines which is the reason emphasis started shifting somewhat to the radial engined La 5 / 7 / 9 series. And I agree the Yak 3 came out late, so did the Tempest and the Fw 190D. The La 5 series and Yak 9 undoubtedly mattered more to the Russian war effort, as probably even the P-39 - I mentioned the Yak 3 because it was so clearly (or so I thought) excellent.

Whether by accident or as was the case sometimes, on purpose, some aircraft - quite a few if you include the Soviet fighters, really ended up being specialized while others were more generally suitable to almost any Theater. The P-51 was the best generalized fighter the Allies had, arguably, in 1944, but for some purposes a Spitfire (basically a specialist interceptor) was better, for others a Yak 3 was (in my opinion) obviously better even though it was a specialized low altitude air superiority fighter.

The relevance was that while versatility was a big part of what was good about the P-40, it was also a specialist for low altitude (early marks) and medium altitude (later versions). And that was Ok because for several major Theaters of great importance to the overall war effort, down low was where the action was.

S

 

[Schweik]

I should also add, I think just comparing simple measurements like top speed (which is inevitably at higher altitude since that is where aircraft flew fastest) or number of guns as some kind of indication of effectiveness is extremely misleading. A MiG 3 was 30 mph faster than a Yak-1b but the latter was much more valuable to the Russian war effort and a pilot flying the Yak had a much better chance of survival. Hurricane IIC was much more heavily armed than a Yak-1 but the latter was a much better fighter. Similarly a Bf 110 had a lot more guns than a Yak 3 but most likely was in big trouble in a fight with one regardless.

The Soviets had their biases just like the West did, but I don't think they were necessarily wrong in terms of aircraft design for their own Theater of war.

 

[Greyman]

"I was running the engine at 55 to 65 inches of mercury and 3,000 rpm ..."

I think this is equivalent to the normal +12 to +16 lb boost that the Merlin XX series used for combat power.

One other thing I forgot to add - 56" Hg on the V-1710 -39 in the P-40E apparently means 1,470 hp at sea level. I don't know what the critical altitude is from there but that is pretty good performance down low ...

I have 1,550 hp up to 4000 feet, which probably translates to a critical altitude of about 7,000 feet.

 

[Schweik]

I think this is equivalent to the normal +12 to +16 lb boost that the Merlin XX series used for combat power.

According to my source it's rated at 1,300 hp with 54" Hg for takeoff, and 61" for WEP. Do you have some online source for those numbers? Is there a table somewhere converting lbs boost to inches of Hg? I'm still getting up to speed on the Merlin engines.

I have 1,550 hp up to 4000 feet, which probably translates to a critical altitude of about 7,000 feet.

Critical altitude at that level of boost? I think critical altitude for the engine overall was ~12,000 ft.

 

[Shortround6]

I should also add, I think just comparing simple measurements like top speed (which is inevitably at higher altitude since that is where aircraft flew fastest) or number of guns as some kind of indication of effectiveness is extremely misleading. A MiG 3 was 30 mph faster than a Yak-1b but the latter was much more valuable to the Russian war effort and a pilot flying the Yak had a much better chance of survival. Hurricane IIC was much more heavily armed than a Yak-1 but the latter was a much better fighter. Similarly a Bf 110 had a lot more guns than a Yak 3 but most likely was in big trouble in a fight with one regardless.

The Soviets had their biases just like the West did, but I don't think they were necessarily wrong in terms of aircraft design for their own Theater of war.

WW II was a period of very fast development in aircraft of all types. What was a perfectly good fighter (even if not great) in one year was a deathtrap two years later in some cases.
By picking and choosing either fighter types or models of certain fighters you can come to some rather strange conclusions or prove a point if not looked at too closely.
The Mig 3 was in service well over a year before the Yak-1B, being in actual fact the most modern fighter available in large numbers when the Germans attacked in in the summer of 1941. Neither the Yak 1 or Lagg-1/3 being available in numbers in operational units as opposed to numbers built/still in depot.
The Mig 3 paid for it's high altitude performance by having light armament. The AM-35 engine would not take a gun through the prop hub so all three machine guns were synchronized.
The Am-35 engine was a big beast and weighed around 550lbs more than the KV-105 engines used in the Yaks and Lagg-3. It weighed several hundred pounds more than any Merlin or DB605 engine and 400-500lbs more than an Allison or Merlin 45 or DB 601. With only 188 sq ft of wing something had to go to accommodate that big engine.

The KV-105PF engine used in the Yak-1b (and indeed most of the later Yaks) was a late 1942 development/adaptation. Of the 3,474 Yak-1s built in 1942 according to one source, 959 were the version with the KV-105PF engine.
On the 5th of Dec 1941, just before the Russian counter attack near Moscow there were only 83 Yak-1s serving in VVS combat units and of those only 47 were operational. The Yak was being built in very large numbers at this time and numbers increased by hundreds per month.

You might want to reconsider using the Hurricane IIC as a bench mark as it was in production in the early Fall of 1941, It would also come close to it's "book" numbers unlike many of the early Russian aircraft. "improved" Yak-1s of late 1941 using the M-105PA engine and fitted with such refinements as a radio were good for about 347mph at at 15,750ft (4800 meters) and took 6.8 minutes to reach 5,000 meters (16,400) which is about 1 minute more than the earlier, even more spartan Yak 1s. Hurricanes tended not cover their own windscreens/canopies with oil for the engine or prop reduction gear, a major fault of the early M-105 engines.

After a 1/2 year in service an assessment concluded that the Yak 1 had a great many defects, but they were not as a dangerous as the defects in the Mig-3 nor impair flying as much as the ones in the Lagg-3
The functioning of the landing gear was unsatisfactory, being not smooth and prone to sticking in intermediate positions and not fully retract. It also tended to fold up on landing.
Many pilots considered the armament too light and it often seized during firing, heat in the cockpit the already mentioned oiling of the windscreen and canopy made flying difficult.
Standard armament for the Yak-1s in the early part of the war was either one 20mm gun and two 7.62mm machine guns or one 20mm and one 12.7mm machine gun.

If I was tasked with shooting down german twin bombers in 1941 there is little doubt that the Hurricane II would be the better choice even if it wasn't as good against 109Fs.
But then only a small percentage of the Russian Mig 3s, Lagg-3s and Yak 1s stood much chance against the 109F.

While the advent of the 105PF engine improved things not everything was not a bouquet of roses, trying to upgrade existing planes didn't go well. They tried increasing the boost on M-105P or PA engines with a few modifications done in the field, however the increase power levels were more than the cooling systems could handle. In hot weather with the radiator intake closed for max speed the engine overheated within 2 minutes at the higher boost ratings. A boosted climb was also impossible without one or more periods of level flight to cool off the engine. Leaking oil also tneded ot clog up the radiator and oil cooler causing further cooling problems. They tried reducing the rpm while keeping the increased boost but any performance advantage was lost. The final PF engines used stronger wrist pins in the pistons, stronger engine blocks, bigger carburetor jets and the aircraft were fitted with a larger oil cooler. cooling was still critical.

Timing is everything and while the YAK series was finally developed into a good serviceable aircraft the early ones had a bunch of problems that affected their combat performance.
Even in mid 1942 the quality of Russian optical guns sights was such that the pilots requested a return to the ring and bead sight system, which was granted. .

What makes a good fighter is certainly more than just top speed or the number of guns but all fighters were far from equal in their subsystems and reliability.
IN regards to gun power Wiki says that a Yak 1 with a single 20mm and a single 12.7mm mg could put out 4lbs of projectiles per second. A Hurricane II C could put out about 11.4 pounds in one second.
The Hurricane would run out of ammo faster

 

[Shortround6]

According to my source it's rated at 1,300 hp with 54" Hg for takeoff, and 61" for WEP. Do you have some online source for those numbers? Is there a table somewhere converting lbs boost to inches of Hg? I'm still getting up to speed on the Merlin engines.

Greg has posted a conversion chart that covers all systems of measurement. however a rough and ready conversion is to take the number in inches (say 54) and subtract 30 ( standard air pressure is 29.92in at 59 degreeF) giving 24 and then divide by 2 to get 12 pounds of boost (boost is the amount over standard air pressure). it can be a little off but should put you close enough.

Critical altitude at that level of boost? I think critical altitude for the engine overall was ~12,000 ft.

any engine is going to have multiple "critical altitudes" depending on the allowable boost limits. Critical altitude was originally the altitude for a single speed supercharger that the throttle could be fully opened without wrecking the engine. Merlin III being a case in point, at 16,250 ft the supercharger would give 6lbs (or close 1/4lb?) with the throttle fully opened and no assist from the high pressure air in the intake duct due to forward speed.
Below 16,250 ft the the throttle had to be closed to prevent overboosting the engine and causing detonation with the 87 octane fuel in service.
A Spitfire has a higher FTH ( Full throttle height) than either a Hurricane or Defiant, which used the same engine in level flight because it's higher speed creates a higher pressure in the intake duct leading to the carb and supercharger.
With the introduction of 100 octane fuel ( actually 100/115-120) the Merlin III was allowed to use 12lbs of boost and the throttle could be fully opened at 9,000ft for 1310hp.
Now please note that as the plane goes lower the throttle has to be progressively closed, wither by the pilot or by an automatic pressure control device/system and this partial blockage of the intake introduces losses. The extra churning of the air ( the impeller is fixed in speed to the crankshaft speed here) also heats up the air more and introduces losses (and dangers ) of it's own.
Throwing caution (and engine longevity) to the winds the Merlin III in the Sea Hurricane (often launched from catapults on a one way trip) was allowed to use 16lbs of boost and had a FTH of 5500ft and made 1440hp at that height.

So what was the FTH or critical height of the Merlin III?
A Spitfire doing 350mph or so could maintain the 6lb boost figure to about 18,000ft instead of the 16,250 of the test house figures just to confuse things and a Hurricane would a bit lower.

A Merlin XX or Packard V-1650-1 is going to have a different critical height for each supercharger gear.
In low gear for 9lbs boost (48 in) it was 11500ft for 1240hp with no assist from RAM and in high gear it was 18,500ft for 1120hp with no RAM. extra 120 hp at the lower altitude at same rpm and manifold pressure is due to less power going to the supercharger, the cooler (denser) intake mixture.
Yes it is rated at 1300hp for take-off at 12lbs (54in) but that is with the throttle part closed.

Please note that the Merlin XX used a different less restrictive and more efficient supercharger inlet than the Merlin III which makes direct comparison difficult.

 

[Schweik]

WW II was a period of very fast development in aircraft of all types. What was a perfectly good fighter (even if not great) in one year was a deathtrap two years later in some cases.
By picking and choosing either fighter types or models of certain fighters you can come to some rather strange conclusions or prove a point if not looked at too closely.
What makes a good fighter is certainly more than just top speed or the number of guns but all fighters were far from equal in their subsystems and reliability.
IN regards to gun power Wiki says that a Yak 1 with a single 20mm and a single 12.7mm mg could put out 4lbs of projectiles per second. A Hurricane II C could put out about 11.4 pounds in one second.
The Hurricane would run out of ammo faster

All very interesting but aside from the weight of the MiG-3 engine (interesting!) none of that is new to me. All the Russian fighters had serious production problems early on, they had to move nearly all the factories for one thing, some of those fighters were being made under the open sky. Ramping up to production was a nightmare even without the German Army and He-111s bombing...

For the record, I mentioned Yak-1B specifically rather than just Yak-1 because I was able to look up the speed for it very quickly (wikipedia) in order to make the point, which in case you forgot was that being fast alone wasn't guarantee of being a better fighter. The -1B may have been later than the MiG but the Yak-1 wasn't, they were contemporanous in fact the MiG-3 came out a bit later.

If you are really trying to suggest that a Hurricane IIC was better in Russia than the Yak-1 I think you are wrong, and you have a lot of Russians to argue with!

Seemingly every Russian who flew the Hurricane on the Russian Front hated it and it had a miserable record in Russia. No doubt it played it's role early on when they had little more than I-16s and I-153s and a few LaGG to play with, but there is no doubt in my mind that a Yak-1 was a better fighter for low altitude combat than any Hurricane.

As for many guns vs. few guns - almost every German pilot who flew them said the Bf109F was the best of the messers but it also had some of the lightest armament. Much, much less than a Hurri IIC, but does anyone argue for the latter in a dogfight?

 

[michael rauls]

I think the Warhawk is a really under-appreciated fighter. When one considers the design dates back to 1935( the warhawk is still a hawk even after a new type of engine just as much as a fw 190d is still a fw 190 even with a new type of engine or a Mustang is still a Mustang etc.) and that it remained in front line service in all theaters and reasonably effective right up until the end of the war is, I think, truly remarkable. Not" 2nd string" or " noteworthy because its all we had in numbers at the time of our entry into the war"or any of the other disparaging characterizations we often read about it.
Was it as good as designs that came into existence 7 or 8 years later( which was a lifetime considering the accelerated pace of development at the time)? No of course not. But then again the p51 was not as good as a F86 either.

 

[wuzak]

I think the Warhawk is a really under-appreciated fighter.

I dunno. All this effort on behalf of the P-40 has me starting to think it is overrated.

When one considers the design dates back to 1935( the warhawk is still a hawk even after a new type of engine just as much as a fw 190d is still a fw 190 even with a new type of engine or a Mustang is still a Mustang etc.) and that it remained in front line service in all theaters and reasonably effective right up until the end of the war is, I think, truly remarkable. Not" 2nd string" or " noteworthy because its all we had in numbers at the time of our entry into the war"

The P-40 never served in front line units in the ETO, certainly not throughout the war.

P-36s served in the Battle of France, but not after that in the ETO.

Was it as good as designs that came into existence 7 or 8 years later( which was a lifetime considering the accelerated pace of development at the time)?

The Spitfire was a very near contemporary of the P-36 (first flight less than a year later) and it also served to the end of the war.

And, generally speaking, it didn't seem that the P-40 was ever rated as highly as the Spitfire.