P40 Vs all other fighters in Europe

[tomo pauk]

But the Luftwaffe didn't have any 400 mph aircraft flying in the Med in 1942. With Trop filters their 109F and early G (toward the end of the year) were doing about 370-380 mph at their highest operating altitude

Any sources about the Bf 109F-4 and/or G-2 losing 30+- mph due to the installation of trop filters, while the P-40 seem to loose zero mph due to filter being installed?

As indicated on the charts I linked, the Tomahawk types were showing a higher critical altitude at military power.

The -33 have had greater critical altitude for the military power, it's military power being lower than on the -39 by about 100 HP. The V-1710-39 was making better power under ~13500 ft, and same power above ~13500 ft.

With the P-40, in all Theaters, they had to figure out how to contend with being attacked from above and carrying the day anyway. That is a very tall order, and it's the reason why the P-40 was considered so flawed. They worked out very specific tactics for this in the MTO, starting with just flying in pairs / figure 4 flights (which for some reason lagged in that Theater until around mid-1942) then flying in squadron formation and turning into the initial attacks as a unit (on the word of the squadron leader). And of course, using their escape maneuvers when they got into trouble.

One of procedures was to have Spitfires flying top cover. Or, as it was the case in the ETO, not to use P-40s at all.

 

[Schweik]

Tomo has covered just about all of the technical changes to the Allison engines.

Some of the pilots manuals don't quite line up with the Allison factory specifications. But some of the pilot manuals tend to get a little sloppy with ram and no ram altitudes
There were some refits with changes with the backfire screens, too. But the superchargers and gear ratios stayed the same. until the 9.60 gears came along.

I'm well aware of all the changes done to the Allisons. The actual altitude where WEP was available varied based on atmospheric conditions, temperature etc., but it was obviously not literally at Sea Level, I think that is just a euphemism for "as low as possible" as a general guideline. This specific engine flight chart from Dec 1942 shows that War Emergency power (57" Hg) on a P-40N is available up to 7500 feet. This is with a V-1710-81 or -99, according to the chart. This 1944 RAAF test showed WEP rating (also looks like 57" again) available to 9,200 ft, and still managing 50" at 13,500 ft. The chart also shows what a huge improvement in speed that meant compared to military power (285 mph vs. 315 mph at Sea level, 315 vs 355 mph at 9200 ft., 330 vs 350 mph at 14,000 ft)

But the main impeller when driven with a 8.80 (or 8.77) supercharger was only going to do so much and it didn't matter if you had the plain steel crankshaft, the shot peened crankshaft or the shot peened and nitrided crankshaft. The engine would hold up longer without breaking at low altitude but it was not going to make any more power at 12,000-15,000ft. (aside from changing out the backfire screens).

See the chart referenced above!

The 9.60 supercharger gears increased the temperature of the mixture and the higher temperature is what caused the caution in restricting the Pressure. An engine running 9.60 gears was always going to be operating closer to the detonation limits.

I would note that the WER were also what the engine should make no RAM (like climbing or coming out of a steep turn)

The P-40 also got lucky. How many threads do we have on things the Japanese could have done differently. (or what the Italians could have done differently)
If the Japanese had looked around and realized that the Ki-43 needed to be retired at the end of 1942 then a lot of the P-40 saga against the Japanese facing Ki-44s ( or Ki-44s with big wings) would have been way different.

This is an interesting line of speculation. There was a lot of higher potential all around, that was always impacted by field conditions, political and economic realities.

Another one of the big Tropes that always settles in over all the key early / early-mid war Allied fighter types: P-40, F4F, Yak-1 and 7, Hurricane, D.520, Spit I through V etc. is that as relatively new aircraft, they suffered teething problems and needed to be adapted to field conditions. Their pilots weren't well trained in many cases (USN being somewhat of an exception, maybe RAF in England too) and new tactics had to be developed to make them work.

P-40N does 378 mph in a test in Buffalo, but then in Australia or at Boscombe down, with bomb shackles, direction finder, rear view mirror, full load of ammunition and fuel, some rivets and metal plates not smoothed over, and maybe not the cleanest paint job, it makes 355 mph.

Obviously the Japanese had the same problems. But they start the war with very well trained pilots, and some field experience in getting their new aircraft ready for battle. Same with the Germans, who also add particularly sophisticated tactics.

Later, when the Japanese are struggling with making some of their new types work on remote islands in Tropical conditions, we sometimes give them a pass. Oh if only the Ki-61s and Ki-44s were running right etc. (let alone getting a new wing!). They had the same struggles the Allied Air Forces did. Various US and Australian P-40 squadrons did indeed face Ki-44s and they didn't exactly get slaughtered. (maybe NZ too I'm not sure). The 23rd FG even seem to have done alright against Ki-84s in one encounter in China that I know of.

Of course by then, the Japanese were suffering from declining pilot quality / training. But we don't really give this same pass to the Allies in 1941-42.

The P-40N (and the L) were both attempts to lighted the plane up when they realized they weren't going to get much in the way of increased power. But with the N the difference in performance wasn't great and the trade-offs limited the actual utility of the airplanes. There were thousands of P-40Ns built (over 1/2 the production run)and no more of the 400 were hotrods were built, if that many and a number of them were converted back to normal Ns, at least somewhat. The Japanese and Italians and to some the extent the Germans, were not able to come up with next generations fighters (or even good improvements to existing generation fighters) that would have knocked the P-40s out of the feild.

Yeah, but this again is veering out into speculation and 'What -IFs'. The US could have gotten jets or bearcats into the Theater earlier, or developed the P-40Q. What matters though really is what happened. P-40s (not Q) turned out to be more useful in 1944 than anyone would have thought in early 1942. That's partly because they were able to work out tactics and mechanical improvements and maintenance procedures so that 'not quite good enough' (ala early 1942) was turning into ('definitely good enough') by late 1942 and most of 1943, and was still 'just about good enough' in 1944. To the surprise of many then, and I would suspect, of many people today as well.

Getting your existing, or new and improved technology working up to spec in the wretched kind of environments you would find in Rabaul or Guadalcanal is part of the whole contest. And this is one of the interesting threads of the story of aviation in WW2, I think.

 

[FLYBOYJ]

P-40N does 378 mph in a test in Buffalo, but then in Australia or at Boscombe down, with bomb shackles, direction finder, rear view mirror, full load of ammunition and fuel, some rivets and metal plates not smoothed over, and maybe not the cleanest paint job, it makes 355 mph.

I get that some manufacturers did some minor mods to get their alleged "stock" products to perform better during factory tests, but please elaborate on your statement "rivets smoothed over," where is that coming from?

 

[Schweik]

Any sources about the Bf 109F-4 and/or G-2 losing 30+- mph due to the installation of trop filters, while the P-40 seem to loose zero mph due to filter being installed?

I think the P-40s did lose some speed due to tropical filters, just not as much. In one test I linked a P-40F had bomb shackles and still made 370 mph, but in other tests it's more like 350. One Boscombe Downe test shows ~340 mph with a Kittyhawk I (P-40D), other Australian tests a little later show 360 mph with a later P-40E. Bf 109 F performance was also down to the horsepower rating allowed etc., and the top speed regardless was at quite high altitude.

I gather figuring out what best performance for 109F and early G series was is also somewhat a work in progress, but on another thread in this forum, Greg P posted this German test of a 109F-2 indicating a top speed of 369 mph at 6km / 19,000 ft, and an F-4 at 388 mph at 8 km / 26,000 ft. I don't think that is with Tropical filters.

I see later in that thread someone noting that an F-4 was cleared for 394 mph at 22k ft in Feb 1942 (clean, i.e. with no Trop filter). A later test (from 1943) you posted says 635 km / hr (416 mph) but I'm not sure when that was achieved in the field, let alone with Tropical filters.

I don't know exactly how much speed the 109F or G-2 lost due to their Tropical filter, except that anecdotally the German pilots mentioned it was significant. The Spit V as we know, lost about 20-30 mph.

The -33 have had greater critical altitude for the military power, it's military power being lower than on the -39 by about 100 HP. The V-1710-39 was making better power under ~13500 ft, and same power above ~13500 ft.

Hmmm, I'll have to look at the charts again, maybe I misread it.

One of procedures was to have Spitfires flying top cover. Or, as it was the case in the ETO, not to use P-40s at all.

They would have done this more often, but the Spit V had very limited range, even more so with the Vokes filter. In the MTO it was only used for airfield defense and other missions very close to base. For attacking the German air bases they typically had to use older P-40s and Hurricanes escorted by newer (i.e. F/L or M) P-40s flying top cover. The Spitfires available in Theater were not even flying on most mission days for example during El Alamain, in Oct -Nov 1942 (about half the days, vs. almost every day for the P-40 units). I posted a long detailed breakdown of this in another thread on here a couple of years ago.

Spit Vs also didn't have super high altitude performance, compared to a Merlin P-40. Both the Spit and P-40 units had to contend with attacks from above by Luftwaffe units and had to use similar tactics. P-38s potentially could do better but they seem to have been dealing with various issues in the Med, and I'm not an expert on that type so I won't say more than that.

 

[Schweik]

I get that some manufacturers did some minor mods to get their alleged "stock" products to perform better during factory tests, but please elaborate on your statement "rivets smoothed over," where is that coming from?

My language wasn't super precise, but I assumed the meaning was clear- 'rivets smoothed over' isn't meant literally. What I mean is that the physical condition of the aircraft varying from relatively rough to relatively pristine, made a notable difference in speed.

In the official AVG memoir they mentioned that one of their Tomahawks tested at a top speed of 348 mph, and after they carefully went over it, stripped the paint off, repainted, sanded and the waxed it, and made several minor repairs to the body where there were seams or gaps in the plates (some filled with some kind of putty), including replacing some rivets and so on, they got the speed up to 359 mph. An 11 mph improvement. And I've read similar anecdotes from many other Theaters and types of aircraft.

I'm sure you know this much better than I do, but looking closely at warbirds today at airshows and museums, you can see seams between panels, or panels raised a bit one over the other, which are wider than you would normally have on a car. All of this causes drag, and these aircraft today, are (at least the flying ones) fairly pristine compared to some in the field in places like Port Morseby (let alone say, some rural field in Russia). Many aircraft would for example have patched bullet or flak holes on the wings or fuselage. Some had major parts from another aircraft bolted on.

 

[FLYBOYJ]

My language wasn't super precise, but I assumed the meaning was clear- 'rivets smoothed over' isn't meant literally. What I mean is that the physical condition of the aircraft varying from relatively rough to relatively pristine, made a notable difference in speed.

In the official AVG memoir they mentioned that one of their Tomahawks tested at a top speed of 348 mph, and after they carefully went over it, stripped the paint off, repainted, sanded and the waxed it, and made several minor repairs to the body where there were seams or gaps in the plates (some filled with some kind of putty), including replacing some rivets and so on, they got the speed up to 359 mph. An 11 mph improvement. And I've read similar anecdotes from many other Theaters and types of aircraft.

I'm sure you know this much better than I do, but looking closely at warbirds today at airshows and museums, you can see seams between panels, or panels raised a bit one over the other, which are wider than you would normally have on a car. All of this causes drag, and these aircraft today, are (at least the flying ones) fairly pristine compared to some in the field in places like Port Morseby (let alone say, some rural field in Russia). Many aircraft would for example have patched bullet or flak holes on the wings or fuselage. Some had major parts from another aircraft bolted on.

OK - because there have been some references to operators "grinding down" rivet heads to assist in getting more speed out of aircraft. This is something that is never done in normal maintenance operations as it destroys the strength of the rivet(s). The only means of removing material from a rivet is done with flush head rivets and a micro shaver. Sometimes you can have gapped heads on rivets that can be replaced helping the effort.

There have been many stories about surface improvements in the field in an attempt to get a few MPH out of an aircraft, but as stated, in a wartime scenario, this can only be done for so long as the pace of combat eclipses the time and need to maintain these mods.

 

[Schweik]

Yeah in general, I don't think they usually could maintain those kinds of high 'grooming' standards for warplanes. They would do things like that for a fighter (or bomber) being used for photo recon missions to get a little more speed out of it, or sometimes when a given aircraft was deemed as losing some performance they would give it a once over. Or more rarely, for a whole unit that was say, flying top cover against very fast opposing aircraft and really needed the edge.

Conversely, routinely used aircraft often had all kinds of issues. I've seen wartime photos where there are holes in aircraft that are apparently operational and haven't been filled in. It all depends on the circumstances.

Also I think people don't always realize, the pace of production for wartime materiel often meant that they didn't put the kind of finish on them that you would get in a civilian vehicle. You see this with tanks and armored vehicles too.

With aircraft, it's a balancing act. It needs to be made to withstand bullets and high G forces, and be 'clean' enough to fly without too much drag, but at the same time, many of them are going to be destroyed shortly after they reach their destination combat zone (some before they even get there). It's only the fact that they were made to be so tough that some of them are still flying today (with a lot of maintenance and rebuilding etc.)

 

[FLYBOYJ]

Yeah in general, I don't think they usually could maintain those kinds of high 'grooming' standards for warplanes. They would do things like that for a fighter (or bomber) being used for photo recon missions to get a little more speed out of it, or sometimes when a given aircraft was deemed as losing some performance they would give it a once over. Or more rarely, for a whole unit that was say, flying top cover against very fast opposing aircraft and really needed the edge.

Conversely, routinely used aircraft often had all kinds of issues. I've seen wartime photos where there are holes in aircraft that are apparently operational and haven't been filled in. It all depends on the circumstances.

Also I think people don't always realize, the pace of production for wartime materiel often meant that they didn't put the kind of finish on them that you would get in a civilian vehicle. You see this with tanks and armored vehicles too.

With aircraft, it's a balancing act. It needs to be made to withstand bullets and high G forces, and be 'clean' enough to fly without too much drag, but at the same time, many of them are going to be destroyed shortly after they reach their destination combat zone (some before they even get there). It's only the fact that they were made to be so tough that some of them are still flying today (with a lot of maintenance and rebuilding etc.)

Well aware of all this, I've been building and maintaining aircraft (to include warbirds) for over 40 years - with that said, you cannot compare aircraft finishes (especially combat aircraft) to what you have on an automobile (maybe corporate aircraft in today's world). Additionally during WW2 there were finish and "gap and mismatch" requirements on production aircraft. After construction, an aircraft was test flown (production test flight) and there was a tolerance of performance that was required to be achieved. If that didn't happen, the unit wasn't accepted.

The perfect example of this were some of the Corsairs built by Brewster.

Unable to meet demand, Vought licensed production to Brewster in November 1941 and to Goodyear Aircraft Corporation one month later. Brewster built 735 Corsairs, with 430 going to the Royal Navy's Fleet Air Arm.

Brewster as a company never reached its potential. Its reputation for poor quality carried over to the license-built Corsairs. Reports from pilots differed as to how well Brewster Corsairs compared to the Vought aircraft. None of the Brewster Corsairs went to front line combat units during the War.

The US Navy closed Brewster's production line at the end of June 1944 because the company was continually behind schedule building the much-needed Corsair, much of it due to labor unrest and strikes.

Brewster F3A Corsair

Dedicated to World War II Aviation

www.worldwariiaviation.org

 

[Schweik]

One thing the US firms seemed to excel at compared to many others, is standardization and interchangeability of parts. Apparently a lot of the Japanese and Russian aircraft basically had 'bespoke' parts, some of the earlier British planes too.

Brewster is a sad story, they seem to have both management and labor problems. It happens with firms all the time to this day. It was certainly becoming an issue with Curtis toward the end of the war and there are notes about production quality issues with later model P-40s in some of the tests on WWIIaircraftperformance, with a notably disgusted tone from the testing officers. I think this is another reason why they decided not to go with the further development of the P-40 like the P-40Q.

 

[wuzak]

The US could have gotten jets or bearcats into the Theater earlier, or developed the P-40Q. What matters though really is what happened. P-40s (not Q) turned out to be more useful in 1944 than anyone would have thought in early 1942.

Any aircraft is more useful than no aircraft.

 

[Schweik]

And an aircraft that flys, and shoots, is better than one sitting in the hangar. I think that's part of it. But there is also a notable difference between say, P-39* or Hurricane units in 1943 or 44 vs. P-40s, especially in any air combat against enemy fighters.

* Except in Russia!

 

[pbehn]

I get that some manufacturers did some minor mods to get their alleged "stock" products to perform better during factory tests, but please elaborate on your statement "rivets smoothed over," where is that coming from?

At least one manufacturer built in to their "stock product" a much higher level of smoothness and panel fit as standard which made the P-40 dog rough by comparison, I read about it in a book on a Bastard Stepchild so I am reluctant to give details.

 

[Schweik]

North American Avitaion?

 

[Schweik]

Thank God that German was working for us!

 

[pbehn]

Another one of the big Tropes that always settles in over all the key early / early-mid war Allied fighter types: P-40, F4F, Yak-1 and 7, Hurricane, D.520, Spit I through V etc. is that as relatively new aircraft, they suffered teething problems and needed to be adapted to field conditions. Their pilots weren't well trained in many cases (USN being somewhat of an exception, maybe RAF in England too) and new tactics had to be developed to make them work.

P-40N does 378 mph in a test in Buffalo, but then in Australia or at Boscombe down, with bomb shackles, direction finder, rear view mirror, full load of ammunition and fuel, some rivets and metal plates not smoothed over, and maybe not the cleanest paint job, it makes 355 mph.

This is the origin of an early strand in groundhoggery. The RAF were not interested in a stripped down, souped up, puttied and sanded aircrafts top speed, the performance figure is only useful in a post war discusssion forum. They were interested in how a combat aircraft performed in standard condition. They understood that armour, self sealing tanks, cannon, aerials etc cost speed and climb, but put up with it because that was what was needed on a war plane, which wasnt a Reno racer. Some manufacturers cried foul as if the client doesnt know what it wanted, others like Supermarine and NAA did what the client asked. When the USA entered the war, their aircraft all carried the "stuff" that the RAF had demanded so there is no doubt what was the correct approach.

 

[Schweik]

Right, and that certainly makes sense. Generally I think this is the wisest approach. Sometimes those Boscombe Downe tests erred on the conservative side a bit, as in using very low boost levels and high weight, especially for foreign planes. But I still think it's the wisest way to do the testing.

One other counterpoint is, quite often planes were eventually 'souped up' (used at higher boost ratings etc.), including Spitfires. The higher speed under 'best conditions' including sanding, higher boost and all the rest, gave them an idea of the potential of the airframe when certain changes were made... changes which might be out of reach at first but became attainable later. This was incorporated for example in the Spitfire when they put the bulletproof window inside, fared over the rearview mirror and so on. Sometimes small changes could be made to reduce drag and improve performance. With regard to the Merlin P-40, they made about a 20 mph difference by the field stripping and 'cleaning up' they did in the field in North Africa. And that did make a difference, apparently, or they wouldn't have been flying any of those aircraft with four guns.

And to this point, it's also worth monitoring how the performance is coping with the increasing amounts of 'stuff', because quite often there is a tipping point which occurs with a difference of just a couple of hundred pounds where performance falls off quite a bit. That is when it's time to re-evaluate either the design or how much gear you are trying to hang on it.

There is no doubt there was a wide range in actual performance under field conditions, vs the ideal performance under perfect conditions, and I wish that was a bit better covered and disseminated by the aviation literature and online resources. We tend to get kind of a random variation with some types showing 'ideal' performance numbers and / or speed with high boost, and others showing numbers based on field conditions + relatively low power. I think this is going to be the subject of another thread I want to start here one day (how to reform the basic 'stat block', including breaking down the different variants better)

When it comes to extreme cases, for example Russian early planes with very rough build quality and pilots flying with the canopy open or removed altogether because it was too difficult to open in an emergency, the speed difference might be as much as 50 mph or more off of the the theoretical baseline. Famous 'field mods' like extra gunpods on Stukas or Hurricanes also imposed a very harsh toll on top speed, though I don't know precisely how much because it's rarely published.

 

[Schweik]

I think the Australian tests are an interesting compliment to the Boscombe Down tests. They tested under field conditions where they were, and the results were often surprising.

 

[pbehn]

One other counterpoint is, quite often planes were eventually 'souped up' (used at higher boost ratings etc.), including Spitfires. The higher speed under 'best conditions' including sanding, higher boost and all the rest, gave them an idea of the potential of the airframe when certain changes were made... changes which might be out of reach at first but became attainable later. This was incorporated for example in the Spitfire when they put the bulletproof window inside, fared over the rearview mirror and so on. Sometimes small changes could be made to reduce drag and improve performance. With regard to the Merlin P-40, they made about a 20 mph difference by the field stripping and 'cleaning up' they did in the field in North Africa. And that did make a difference, apparently, or they wouldn't have been flying any of those aircraft with four guns.

There are many types of test. A product acceptance test is in the as delivered condition. Other tests to determine the effect of changes are a different story. The RAF and Supermarine conducted tests for all sorts of reasons, like producing a Spitfire with all flush rivets, covering them with split peas and progressively removing them to see how speed was affected. Flush riveting is more expensive and takes more time, so it was really an experiment in how many more Spitfires could be produced without badly affecting their performance. Testing at higher boost levels was done to verify the engine changes. If you randomly just use more boost than recommended in the field without the appropriate new engines and fuels you can quickly end up with no airforce.

 

[Schweik]

There are many types of test. A product acceptance test is in the as delivered condition. Other tests to determine the effect of changes are a different story. The RAF and Supermarine conducted tests for all sorts of reasons, like producing a Spitfire with all flush rivets, covering them with split peas and progressively removing them to see how speed was affected. Flush riveting is more expensive and takes more time, so it was really an experiment in how many more Spitfires could be produced without badly affecting their performance. Testing at higher boost levels was done to verify the engine changes. If you randomly just use more boost than recommended in the field without the appropriate new engines and fuels you can quickly end up with no airforce.

True, but you can (and did) also end up with no Air Force by flying according to the manual / SOP, and sometimes you had to push the envelope a bit. As many units in fact did. There was a sweet spot between manufacturers recommendations and the conditions in the field (and capability of the enemy!)

 

[FLYBOYJ]

True, but you can (and did) also end up with no Air Force by flying according to the manual / SOP, and sometimes you had to push the envelope a bit. As many units in fact did. There was a sweet spot between manufacturers recommendations and the conditions in the field (and capability of the enemy!)

And there was a guy called the Maintenance Officer who generally made that decision. At the same time a pilot could refuse to fly an aircraft if he deemed it unairworthy.