"Stretch or not strech" of aircraft designs (1 Viewer)

[Shortround6]

I believe Ivan1GFP is close to the truth.
The engines in most P-39s the Russians had gave as much or more power at 4000 meters and under than the M-105 engines in the Yaks and Lagg-3s. The build quality was better on the P-39 (as much of difference between the paper specs of the P-39 and the aluminum ones the difference between the paper specs of the Russian aircraft and the aluminium/wood ones was often greater.)
Most Russian fighters were poorly armed by western standards. I say this because while there are certainly numbers of Russian fighters that were at least adequately armed (faint praise intended) a batch of several hundred planes is a mere handful in Russian terms.
Range of missions tended to short on the Russian front so short range was not as big a problem. The low alittidues of the vast amjority of combat meant the P-39s poor perfroamce at 15,000ft (or 20,000ft for later ones) and above was not a problem.

AS an exercise try to substitute any Russian fighter for an Allied fighter in other theaters at the same time. Lagg-3s or Yak-1s in New Guinea/Australia or Guadalcanal ??Or cross channel operations in NW Europe?

 

[P-39 Expert]

Hello P-39 Expert,

Let's accept for a moment that there are no issues with an engine swap and no additional cooling requirements for the higher powered engine (which I believe to be unlikely).
How much performance improvement do you believe would result from adding 300 HP at 22,400 feet?
The P-39N with the V-1710-85 was tested at
398.5 MPH @ 9700 feet and
389.5 MPH @ 16100 feet.

Would it even break 400 MPH at altitude?
Would the performance level be more suited to a typical ETO fighter from 1942?
The armament of a single big 37mm and a couple synchronized .50 cal would still be less than adequate.

- Ivan.

Not really an engine swap, same Allison just 8.1 internal supercharger gears. Second stage was just an add-on. Like the P-63 just move the coolant tank from behind the engine to the front, then put the second stage where the coolant tank was. Shouldn't need more cooling, same horsepower (1325/1150) as the -73 in the P-39D-2/K/L, the -95 just made it's 1150hp at 22400' instead of 12000'.
I don't know exactly what performance improvement the two stage P-39 would have. Probably a little better than the P-63 since it would have been 1000# lighter and have 35sqft less wing for the same HP. Climb should have been outstanding.
The P-39N had 100HP more at altitude than the P-39K and was 20mph faster. 300 extra HP at an even higher altitude 22400' would have made quite a difference, certainly more than 400mph. Probably a little better than a P-63A.
A P-39N was already about the same performance as the 109 and 190. A bit slower at altitude but better climb, turn and endurance. Add another 300HP at higher altitude and performance improves drastically.
The 37mm and two .50s was plenty. One hit from the cannon and goodby opponent. Just my opinions.

 

[Schweik]

Not lying, but perhaps overly optimistic as to how many enemy aircraft that they did shoot down?

Yet somehow more 'overly optimistic' than everyone else. For some reason we ignore huge rates of overclaiming by say, the Germans in these contexts.... which is odd

 

[Schweik]

I believe Ivan1GFP is close to the truth.
The engines in most P-39s the Russians had gave as much or more power at 4000 meters and under than the M-105 engines in the Yaks and Lagg-3s. The build quality was better on the P-39 (as much of difference between the paper specs of the P-39 and the aluminum ones the difference between the paper specs of the Russian aircraft and the aluminium/wood ones was often greater.)
Most Russian fighters were poorly armed by western standards. I say this because while there are certainly numbers of Russian fighters that were at least adequately armed (faint praise intended) a batch of several hundred planes is a mere handful in Russian terms.
Range of missions tended to short on the Russian front so short range was not as big a problem. The low alittidues of the vast amjority of combat meant the P-39s poor perfroamce at 15,000ft (or 20,000ft for later ones) and above was not a problem.

AS an exercise try to substitute any Russian fighter for an Allied fighter in other theaters at the same time. Lagg-3s or Yak-1s in New Guinea/Australia or Guadalcanal ??Or cross channel operations in NW Europe?

I think way too much emphasis tends to be put on NW Europe in WW2. During the Battles of France and Britain it was very important. Then fighting settled down quite a bit, barring brief but bloody flareups like Dieppe, all the way until June of 1944. The direction of the war had changed by then.

A lot of the fighting in the Med, the Pacific, and the CBI was done at quite low altitude. This is why aircraft like the A6M2 and Ki-43-I which did not have good high altitude capabilities performed quite well.

Imagine say a Yak-9T available in Burma instead of a Hurricane. Yak -9T is armed with a 37mm NS-37 nose gun and a 12.7mm mg,. More than adequate to destroy any Japanese aircraft. It is 50 kph faster and far more agile than a Hurricane. I think it might have been a good swap.

 

[Schweik]

Hello Schweik,

I believe that part of the explanation here is the relative performance of the P-39 in each theatre.
On the Eastern Front, the P-39 was flying near ground level where its performance was at its peak.

As I mentioned previously, much of the fighting in the Pacific, the CBI and the MTO was at low altitude. Fighters have to follow the bombers, and only a few A/O were based around high flying medium bombers (eg Darwin), in most of these Theaters most of the damage was being done by medium bombers flying at medium altitude, or dive bombers / fighter bombers fighting down to the deck. So in other words, the altitude limitations of the P-39 were not as crucial as alluded. It's also worth pointing out that the P-40 performed well in MTO, Pacific and CBI Theaters, so why couldn't the P-39 with the same engine? The only real difference in raw numbers was range.

I'm suggesting there were also other differences which are a bit harder to quantify.

The Soviets deleted the wing guns, reduced the fuel load, and seriously overboosted the engines without regard to the limitations in the manual. At low altitude, there was enough supercharger to give some extra boost.

Anglo-American and ANZAC pilots did the same thing with their fighters in places like the Pacific and MTO... do you have any evidence the Soviets did more of these weight saving measures than anyone else?

The single 37 mm cannon and pair of cowl mounted .50 cal didn't bother them because that was pretty close to what other Soviet fighters used. 1 MG and 1 cannon was not an unusual armament for their late fighters.

I already pointed this out. 1 37mm and 2 nose mounted HMG was actually quite good armament unless you are trying to shoot down B-17s.

Also, for the most part, Soviet fighters were not particularly fast, so the speed of a late model P-39 would have been very comparable.

Both the P-39 and say, Yak 1B or Yak 9 were quite fast for their era, assuming they were performing to spec. Faster than say, an A6M2, a Hurricane or an MC 200.

On the Western Front, the battles are much higher and start off about where the P-39 runs out of steam.
The P-39 was also relatively slow at altitude, especially by the standards in the West.

Again, only if you are talking about the English Channel where the focus of fighting was gone for most of 1941-1944

In the case of the Spitfire, I believe the "real" length of the airframe never really changed. The distance from firewall to rudder hinge line was the same for all versions. The overall length changed because the engine dimensions forward of the firewall changed and the rudder aft of the hinge line changed.

I'm referring to the length from the propeller blade to the rudder tip. Which is I think the significant part.

In the case of the P-40 Hawk 87 series, the short tail aircraft had an offset fin that was straightened on the long tail aircraft. Part of the problem with offset surfaces is that they are really only balanced for a certain speed range. There isn't enough aerodynamic force below the speed and there is too much above the speed and both conditions need to be trimmed out to fly straight and level without control inputs.

- Ivan.

Part of the issue with the P-40 was that it was routinely able to dive at speeds up to 500 mph and more, most aircraft didn't have to contend with controlling an aircraft going that fast (certainly I don't know of any Soviet planes which could). Lengthening the tail on the P-40 seemed to fix the torque problems substantially, although you did still have to use trim somewhat.

 

[Schweik]

A couple of other thoughts.

My comment that the flight characteristics of the P-39 may have been more manageable to Soviet pilots due to their familiarity with less than stable aircraft (and other things like the nose guns etc.) was not meant to explain the entire mystery. The single most significant factor was probably the careful and extensive 4 month workup the Soviets did with the P-39 before sending it into combat which was more than with any other Lend Lease aircraft. The full explanation though defies complete understanding to date as far as I'm concerned. The combat performance of the P-39 in US and "Western" Allied hands was abysmal, in Soviet hands, excellent. There was apparently one P-39 Ace in USAAF, in the Soviet Union there were dozens, including several of their top scoring pilots. The Soviets preferred it over the Hurricane, the Kittyhawk, the Spitfire, the P-47, and most their own fighters up to 1944.

Another possible factor which has been mentioned before is climate - P-39s may not have performed as well in high humidity, hot tropical environments. However that doesn't completely explain it either because though people tend to forget, Russia, Ukraine etc. do have Summer and in fact Summer there can be quite hot.

As for the armament of Soviet fighters, as I have mentioned before the weapon loadout of most mid war Soviet Yakovlev or Lavochkin series fighter aircraft was comparable to that of the contemporaneous Bf 109F which was considered the best 109 version by German pilots themselves, and were generally superior to the Ki-43 which was apparently the most successful Japanese fighter in terms of victory scores. Nor was a Spitfire with two wing mounted 20mm cannon carrying 60 rounds and badly prone to stoppages / jams necessarily vastly superior to a single hub mounted 20mm cannon with 120 rounds in a Yak-9.

You don't need 3 or 4 x 20mm cannon, or 6 or 8 x 12.7mm MG unless you are shooting down big four engine bombers or super heavily armored attack planes. The Germans up-gunned their fighters (at the detriment of maneuverability) to contend with B-17s, B-24s, and Il2-Sturmoviks. The Germans themselves on the other hand did not have any bombers as difficult to shoot down as a B-17 or a Sturmovik, so the Soviets didn't need such an arsenal on their fighters

That is also why it was not so unusual to have a 4 x gun armament on many American fighters in the early to mid-war. The F4F-3, the P-51B, the Kittyhawk I, (and later 'stripped' Kittyhawks) all fought with just 4 guns and did so quite effectively. Hurricanes were also on numerous occasions stripped down to two (20mm) guns in the field.

Six guns or 4 x 20mm are convenient for strafing and it certainly doesn't hurt to have extra guns and extra ammunition for overkill, but the Soviet system did not emphasize a 'spray and pray' approach to gunnery- their pilots were trained to close to point blank range and kill with just a few rounds. Much like Hans Joachim Mariselle did with his Bf 109F. We know this was effective in Soviet use because there are enough well documented incidents in which Soviet Aces shot down multiple German planes - whose wrecked carcasses were recovered by ground troops or even Soviet ground crews operating near their airbases- to demonstrate it was possible to destroy several fighters on a single sortie in a fighter that carried little more than 100 rounds of ammunition.

 

[Shortround6]

I think way too much emphasis tends to be put on NW Europe in WW2. During the Battles of France and Britain it was very important. Then fighting settled down quite a bit, barring brief but bloody flareups like Dieppe, all the way until June of 1944. The direction of the war had changed by then.

A lot of the fighting in the Med, the Pacific, and the CBI was done at quite low altitude. This is why aircraft like the A6M2 and Ki-43-I which did not have good high altitude capabilities performed quite well.

Imagine say a Yak-9T available in Burma instead of a Hurricane. Yak -9T is armed with a 37mm NS-37 nose gun and a 12.7mm mg,. More than adequate to destroy any Japanese aircraft. It is 50 kph faster and far more agile than a Hurricane. I think it might have been a good swap.

There was a fair amount of cross channel flying being done in NW europe even if it didn't really amount to much in terms of effectiveness or notable battles. The whole lean into France thing. It may have been a poor strategy or tactic but it was being done and it did affect fighter development and for the British, fighter deployment. Better fighters kept at home.
The altitude ability of the A6M2 and Ki-43-I was not bad due to the power to weight ratio and low wing loading. That is not bad for their time.
If you have several planes with engines giving similar power at similar altitudes and using similar sized wings the 6000lb planes are going to perform better at higher altitudes than 7500-8000lb planes. Once the Japanese changed to improved engines with 2 speed superchargers their altitude performance got better. Of course some of the improved engine power was sucked up by better protection on the Ki-43 II and improved armament and slightly heavier construction on later A6Ms.

Not sure how good the Yak 9T would have been. The 37 is great IF you can hit with it but since the ammo for it (and the single) 12.7 are ,limited and since even a MK I Hurricane could destroy most Japanese aircraft the Yak doesn't actually bring much.

 

[Schweik]

There was a fair amount of cross channel flying being done in NW europe even if it didn't really amount to much in terms of effectiveness or notable battles. The whole lean into France thing. It may have been a poor strategy or tactic but it was being done and it did affect fighter development and for the British, fighter deployment. Better fighters kept at home.

I never said that no fighting was happening there, but the important battles from 1941-1944 were actually in other parts of the world. It's certainly understandable that the British would keep their best fighters at home given the horrors and near catastrophe of the BoB, but that doesn't change the fact that the hardest and most intense fighting during that time was happening in places like Guadalcanal, El Alamein, and Stalingrad, not over La Havre.

So when people discuss aircraft and routinely dismiss planes, including basically all the Soviet fighters, because they didn't fight well at 25,000' and therefore would have been rubbish in Northwest Europe, I would say they are missing the mark. The notion of swapping Soviet fighters with say, Spitfires or P-40s in some other Theater is also flawed because whereas many Anglo-American aircraft (both fighters and bombers) were effectively generalist war machines, meant to operate in a wide variety of environments, the Soviet fighters, certainly by 1942, were specifically tailored specialists for fighting in their environment, i.e. on the Russian Front. That was one of the differences in their whole approach to warfare. Which didn't make them worse it was just different.

So let me turn your question on it's head - what American or British army in 1942/43 could have defeated the German Army faced by the Soviets at Stalingrad or Kursk?

It's kind of like how most Americans think the P-51D was the most important and best fighter of WW2. I do think it was an excellent fighter, and did more damage to the enemy than all other American fighters probably, but it didn't even appear in the skies until after the hardest batles had already been fought and won by the Allies and the momentum of the war had permanently turned against the Axis. The P-51D was involved in a massive and glorious mopping up operation, albeit with some intense flare ups of combat which equaled those of the more pivotal parts of the war - they just didn't threaten the actual outcome of the war in anywhere near the same way.

The altitude ability of the A6M2 and Ki-43-I was not bad due to the power to weight ratio and low wing loading. That is not bad for their time.

Not bad is certainly a subjective term, but they certainly did not perform well at 25,000'

If you have several planes with engines giving similar power at similar altitudes and using similar sized wings the 6000lb planes are going to perform better at higher altitudes than 7500-8000lb planes. Once the Japanese changed to improved engines with 2 speed superchargers their altitude performance got better. Of course some of the improved engine power was sucked up by better protection on the Ki-43 II and improved armament and slightly heavier construction on later A6Ms.

A6M5's also had armor, more and heavier guns and more ammunition.

Not sure how good the Yak 9T would have been. The 37 is great IF you can hit with it but since the ammo for it (and the single) 12.7 are ,limited and since even a MK I Hurricane could destroy most Japanese aircraft the Yak doesn't actually bring much.

Yak-9T brings 50 kph faster speed and substantially greater agility. The 37mm gun makes it at least the equivalent of the Hurricane (whose ammunition is also limited)

 

[michael rauls]

Not sure if this is true but I've read several different places that the p39s the Soviets got all were equipped with 20mm not 37mm cannon as is commonly thought.

 

[Schweik]

No that is not true. They had some with 20mm but most of the ones they got had the 37mm gun which they liked.

 

[michael rauls]

No that is not true. They had some with 20mm but most of the ones they got had the 37mm gun which they liked.

Thanks for clearing that up. It's amazing how many articles get written stating things as fact that are not. Sometimes it's difficult to figure out what's true and what's isn't.

 

[Schweik]

I was unclear myself for a long time. There are still some good articles on lend-lease website though they seem to have moved location and are a bit harder to find now.

This is a good one about early P-39s in Soviet use

Early Versions of Airacobra Aircraft in Soviet Aviation. Part 1 – Lend-Lease
Early Versions of Airacobra Aircraft in Soviet Aviation. Part 2 – Lend-Lease

an interview with a Soviet pilot who flew P-39s

Interview with Alekseev Dmitrii Dmitrievich – Lend-Lease

 

[Schweik]

Sometimes it's difficult to figure out what's true and what's isn't.

Almost every book written about fighters in the 20th Century (see Bill Gunston et al) claimed that the soviets used P-39s almost exclusively for tank busting. As if one can run up 63 air to air victories as an afterthought in between strafing tanks. It was only after Soviet sources became available after ~ 1991 that we were reminded by the Russians that almost no AP ammunition was ever sent to Russia for the Oldsmobile 37mm gun and that the Soviets mostly flew them on air superiority missions.

Such a huge variation between the just about universally accepted assumption and the actual facts should give us pause, and is worth thinking about in the context of many other supposedly long proven historical facts. It is by no means a unique case!

 

[Shortround6]

The Russian aircraft were not tailored for the eastern front. Not in the sense that they were really what the Russians wanted/desired.
They were what the Russians were able to build and they did the best the could with what they had a available and they were rather realistic about what could and could not be done with engines, fuel and guns they had available.
The Russians would have loved to build fighters using the more powerful M-106 engine and they would have loved even more to use the M-107 engine but both engines (prototypes built before the german invasion) simply could not be brought up to service reliability during the war forcing the continued use of the M-105 engine. Given the limited power and altitude capabilities of the M-105 the Russians "Tailored" their aircraft for performance by restricting the number of guns and the amount of ammo. Manufacturing ability also entered into it as a 12.7mm gun could be built with fewer man hours than the fast firing Rusian 7.62 gun. The 7.62 was an excellent gun on paper and in service but required too much effort to manufacture and service.
You can find small batches of aircraft that were manufactured during the war with these later model engines but in some cases they were rebuilt with M-105s before being issued for service. The Russians did get better V-12s into service post war.

The Russians tended to like heavy armament if they could get it without sacrificeing too much else. The late model LA fighters went from 2 20mm guns to 3 guns when a new lighter weight gun was developed. The Russians wanted 3 or 4 cannon, they just knew their aircraft could not carry them without an unacceptable loss of performance.

The Russian 20mm cannon was a rather pedestrian gun. Since the cartridge was basically a necked up 12.7mm machine gun case (not exactly the same one that saw wide spread service) it was in the lower 1/2 of 20mm cartridges in regards to power. The gun itself was on the light side and not particularly durable but it was rather easy to make and reliable. However it should not be a surprise that the Russians were looking at alternatives to it. Like the larger calibers, the late war lighter 20mm allowing more guns to be fitted, the 23mm guns, especially the short 23mm cartridge guns that showed up immediately post war ( development started during the war) so the Russians were persuing multiple avenues of improved gun performance.

 

[P-39 Expert]

I believe Ivan1GFP is close to the truth.
The engines in most P-39s the Russians had gave as much or more power at 4000 meters and under than the M-105 engines in the Yaks and Lagg-3s. The build quality was better on the P-39 (as much of difference between the paper specs of the P-39 and the aluminum ones the difference between the paper specs of the Russian aircraft and the aluminium/wood ones was often greater.)
Most Russian fighters were poorly armed by western standards. I say this because while there are certainly numbers of Russian fighters that were at least adequately armed (faint praise intended) a batch of several hundred planes is a mere handful in Russian terms.
Range of missions tended to short on the Russian front so short range was not as big a problem. The low alittidues of the vast amjority of combat meant the P-39s poor perfroamce at 15,000ft (or 20,000ft for later ones) and above was not a problem.

AS an exercise try to substitute any Russian fighter for an Allied fighter in other theaters at the same time. Lagg-3s or Yak-1s in New Guinea/Australia or Guadalcanal ??Or cross channel operations in NW Europe?

I agree mostly with you and Ivan.

Analyzing the P-39 has always been difficult because detailed performance information on the later N and Q models wasn't available until 2012 as far as I know.
Helps to analyze by timeline as well as theater. As with most planes performance increased over time.

In early '41 the first production P-39s were the C model without armor/self sealing tanks and the P-400 for the British that grossed an astonishing 7850# clean. It could not compete with the comtemporary SpitfireV that weighed 6500#. Astonishing, eh? The comtemporary C model weighed 7075# and would have weighed the same after the self sealing tanks and a reasonable amount of armor (140# vs 245# for the P-400) had been added because the new tanks reduced fuel by 300# and the nose .30s weren't needed. But nothing was done to the 20 C models except to use them as trainers/pilot familiarization.
First combat was defending Port Moresby, NG. AAF was not really up to speed yet, losing 17 planes just ferrying them from Australia. May '42 saw two squadrons defending Moresby against mostly G4M Betty bomber attacks escorted by Zeros from Lae. Ineffective radar and coastwatchers meant the two squadrons had to fly standing patrols to intercept the bombers who came in at 18000-22000' with escort above. The early P-39D/F/K/L had a theoretical 40mph speed advantage over the early Zeros at all altitudes but could not climb above 20000' (at 1000 feet per minute) with the now ever present drop tank. Virtually all Zero attacks came from above so these P-39s were at a severe disadvantage. In hindsight the wing guns/nose armor should have been deleted as soon as the AAF realized that virtually all missions would carry drop tanks. Had this been done the lighter P-39s would climb over 23000' at normal power with drop tank and in clean condition (combat) would outclimb contemporary Zeros at all altitudes. Bell issued weight saving instructions in May but who knows if that information ever got to the front. Moresby was saved by the Coral Sea battle and the Australians pushing the Japanese back, but the green pilots in the overwweight P-39s held their own.
Then in February came Guadalcanal and the famous P-400s (like a P-39D-1) who couldn't climb above 12000' because they had no oxygen as their British oxygen system was different than the Navy's and there was no time to wait. But all you hear is they couldn't climb above 12000'. No F4F Wildcat would outclimb any P-39 (with oxygen) at any altitude up to 25000', but you never hear that from the Navy/Marines, and Guadalcanal was largely their show.

On to North Africa in late '42 and a few squadrons of early P-39s and P-400s struggled along overweight as usual so their work was limited to mostly ground attack.
By now the (late '42) early P-38s were coming into combat finally and with all their inherent problems. The P-47 would be in combat in England in May. The AAFs turbocharged fighters were finally coming online and the P-39 (and P-40) would move into second line duty. Their only purpose was to hold the line until the turbocharged P-38 and P-47 could get into action. Except the P-39 could have dome much better all this time by just removing some items thus reducing their weight. Almost criminal to send those men into combat equipped that way.

But now in November/December '42 Allison has finally widened the V-1710 supercharger gears so they would take the 9.6 gears and the P-39N is coming out the door. The extra 100HP above critical altitude resulted in improved speed and great climb, the only planes that would climb with the N in early '43 were the Me109G and of course the SpitfireIX which would outclimb anything. The N would definitely outclimb the early Lightnings and Thunderbolts. But by now the P-39 (and P-40) were relegated to training and lend lease to the Soviets. The N and Q were the main types sent to the USSR in spring '43 and they were the same plane after removal of the wing guns and the IFF radios. Even lighter than the already well performing N the Airacobra went on to glory in the east. Oh well.

 

[michael rauls]

I agree mostly with you and Ivan.

Analyzing the P-39 has always been difficult because detailed performance information on the later N and Q models wasn't available until 2012 as far as I know.
Helps to analyze by timeline as well as theater. As with most planes performance increased over time.

In early '41 the first production P-39s were the C model without armor/self sealing tanks and the P-400 for the British that grossed an astonishing 7850# clean. It could not compete with the comtemporary SpitfireV that weighed 6500#. Astonishing, eh? The comtemporary C model weighed 7075# and would have weighed the same after the self sealing tanks and a reasonable amount of armor (140# vs 245# for the P-400) had been added because the new tanks reduced fuel by 300# and the nose .30s weren't needed. But nothing was done to the 20 C models except to use them as trainers/pilot familiarization.
First combat was defending Port Moresby, NG. AAF was not really up to speed yet, losing 17 planes just ferrying them from Australia. May '42 saw two squadrons defending Moresby against mostly G4M Betty bomber attacks escorted by Zeros from Lae. Ineffective radar and coastwatchers meant the two squadrons had to fly standing patrols to intercept the bombers who came in at 18000-22000' with escort above. The early P-39D/F/K/L had a theoretical 40mph speed advantage over the early Zeros at all altitudes but could not climb above 20000' (at 1000 feet per minute) with the now ever present drop tank. Virtually all Zero attacks came from above so these P-39s were at a severe disadvantage. In hindsight the wing guns/nose armor should have been deleted as soon as the AAF realized that virtually all missions would carry drop tanks. Had this been done the lighter P-39s would climb over 23000' at normal power with drop tank and in clean condition (combat) would outclimb contemporary Zeros at all altitudes. Bell issued weight saving instructions in May but who knows if that information ever got to the front. Moresby was saved by the Coral Sea battle and the Australians pushing the Japanese back, but the green pilots in the overwweight P-39s held their own.
Then in February came Guadalcanal and the famous P-400s (like a P-39D-1) who couldn't climb above 12000' because they had no oxygen as their British oxygen system was different than the Navy's and there was no time to wait. But all you hear is they couldn't climb above 12000'. No F4F Wildcat would outclimb any P-39 (with oxygen) at any altitude up to 25000', but you never hear that from the Navy/Marines, and Guadalcanal was largely their show.

On to North Africa in late '42 and a few squadrons of early P-39s and P-400s struggled along overweight as usual so their work was limited to mostly ground attack.
By now the (late '42) early P-38s were coming into combat finally and with all their inherent problems. The P-47 would be in combat in England in May. The AAFs turbocharged fighters were finally coming online and the P-39 (and P-40) would move into second line duty. Their only purpose was to hold the line until the turbocharged P-38 and P-47 could get into action. Except the P-39 could have dome much better all this time by just removing some items thus reducing their weight. Almost criminal to send those men into combat equipped that way.

But now in November/December '42 Allison has finally widened the V-1710 supercharger gears so they would take the 9.6 gears and the P-39N is coming out the door. The extra 100HP above critical altitude resulted in improved speed and great climb, the only planes that would climb with the N in early '43 were the Me109G and of course the SpitfireIX which would outclimb anything. The N would definitely outclimb the early Lightnings and Thunderbolts. But by now the P-39 (and P-40) were relegated to training and lend lease to the Soviets. The N and Q were the main types sent to the USSR in spring '43 and they were the same plane after removal of the wing guns and the IFF radios. Even lighter than the already well performing N the Airacobra went on to glory in the east. Oh well.

Very interesting but are you sure the p39 outclimbs the p38, any p38. In americas 100,000 there is a chart( ive seen it and similar charts elsewhere) that shows i believe the p38G with the best climb of 4200 ft per min. and the other variants weren't far behind.
Didn't think anything except maybe the late Bf109 Gs could climb with a p38.

 

[Ivan1GFP]

Not really an engine swap, same Allison just 8.1 internal supercharger gears. Second stage was just an add-on. Like the P-63 just move the coolant tank from behind the engine to the front, then put the second stage where the coolant tank was.

Hello P-39 Expert,

Just out of curiosity, WHERE in front of the engine do you see space to move the coolant tank?
The attached schematic of a P-39K shows the internals to be a pretty tight fit.

I don't know exactly what performance improvement the two stage P-39 would have. Probably a little better than the P-63 since it would have been 1000# lighter and have 35sqft less wing for the same HP. Climb should have been outstanding.
The P-39N had 100HP more at altitude than the P-39K and was 20mph faster. 300 extra HP at an even higher altitude 22400' would have made quite a difference, certainly more than 400mph. Probably a little better than a P-63A.

One has to wonder if a simple engine swap would result in a better aircraft than the P-63, then why Bell even spent the effort to build the P-63. The numbers aren't quite that easy because there is still the difference in airfoils, but as a quick calculation, my numbers aren't disagreeing with yours.

A P-39N was already about the same performance as the 109 and 190. A bit slower at altitude but better climb, turn and endurance. Add another 300HP at higher altitude and performance improves drastically.
The 37mm and two .50s was plenty. One hit from the cannon and goodby opponent. Just my opinions.

Same performance depends on WHICH version of the 109 or 190 you are trying to compare. One of the issues with the Airacobra was that its roll rate was never particularly good which is somewhat surprising considering the size of the aircraft.
The 37 mm cannon was very powerful, but ballistics were lousy, it had a low cyclic rate and it had very little ammunition. It probably would work very well against a non-maneuvering target which was its intended target but may not be so effective against another fighter.

Anglo-American and ANZAC pilots did the same thing with their fighters in places like the Pacific and MTO... do you have any evidence the Soviets did more of these weight saving measures than anyone else?

Hello Schweik,

From what I have been able to find, there is very little mention of loading OVER 200 rounds per .50 cal cowl gun except in one flight test and in the Russian manual on the P-39. Other reports mentioning ammunition loads have stated 200 rounds as a full load.
I believe the reduction in fuel capacity in the late model Airacobra was at the request of the Soviets and not of anyone else though there is also mention that fuel capacity can be restored if needed.

I already pointed this out. 1 37mm and 2 nose mounted HMG was actually quite good armament unless you are trying to shoot down B-17s.

I believe the 37 mm would have been more useful against a big target such as a B-17 than in pulling a deflection shot against another fighter. It gets even worse when you consider that the ballistics of the cannon is so different from the two cowl guns that if one is one target, the other won't be.

Both the P-39 and say, Yak 1B or Yak 9 were quite fast for their era, assuming they were performing to spec. Faster than say, an A6M2, a Hurricane or an MC 200.

The problem with this statement is what "for their era" means. A Hurricane or Macchi C.200 wasn't really a competitive fighter past about 1940-1941 at the latest. The faster than a A6M2 is a probably but by how much. Combat reports suggest that the Airacobra's speed advantage in combat was VERY small.
In various places, the opposition was pretty low tech (Think Italian biplanes and Ki 27) and fighters that were not suitable for front line service elsewhere could still do the job well enough. That is probably why aircraft such as the P-40, Hurricane and even Gladiator were used effectively for a while. That does not mean that they were really up to standards.

I'm referring to the length from the propeller blade to the rudder tip. Which is I think the significant part.

This is a bit of a circular argument to state that an aircraft needed to be lengthened to compensate for increased power when the only part that was lengthened was the larger engine to give increased power....

Part of the issue with the P-40 was that it was routinely able to dive at speeds up to 500 mph and more, most aircraft didn't have to contend with controlling an aircraft going that fast (certainly I don't know of any Soviet planes which could). Lengthening the tail on the P-40 seemed to fix the torque problems substantially, although you did still have to use trim somewhat.

P-40N manual states maximum diving speed is 496 MPH IAS.
It also states that the aircraft will yaw to the right when diving. This suggests that the typical trim / offsets even on the P-40N are such that above a certain speed, aerodynamic effects will still cause a pull to the right and below that speed, there will be a pull to the left.
In comparison, this is not an extraordinarily high diving speed. I believe the Ki 84 manual lists 475 MPH IAS which isn't far off.

- Ivan.

 

[Schweik]

The Russian aircraft were not tailored for the eastern front. Not in the sense that they were really what the Russians wanted/desired.
They were what the Russians were able to build and they did the best the could with what they had a available and they were rather realistic about what could and could not be done with engines, fuel and guns they had available.

I disagree. I don't think you understand the Soviet war fighting mentality.

The Russians would have loved to build fighters using the more powerful M-106 engine and they would have loved even more to use the M-107 engine but both engines (prototypes built before the german invasion) simply could not be brought up to service reliability during the war forcing the continued use of the M-105 engine. Given the limited power and altitude capabilities of the M-105 the Russians "Tailored" their aircraft for performance by restricting the number of guns and the amount of ammo.

As previously discussed in this thread, development of advanced features in aircraft - including and especially more powerful and effective engines - are often a tradeoff between production of existing models with new more advanced capabilities. The Soviets concentrated on huge numbers - there were over 30,000 Yak fighters produced during the war, under extremely difficult conditions (for example factories in the open air) during the early years of the war. They did not have a safe place to do long term R&D so they did only enough of that to keep up with enemy capabilities, which they did.

The Yak 1 & 7 could handle the Bf 109E, the Yak 1B and 7B could contend with the Bf 109F and early G models. The Yak 9 and La 5 could handle the Fw 190 and later G models. But only at low altitude, only at short range. They did not need to defeat them at higher altitudes or at long range, only over the front so the Soviets did not put much effort into high altitude or long range capabilities until late in the war. All they needed was sufficient performance to protect Sturmoviks and Pe-2s and shoot down Ju 87s and Ju 88's, usually within sight of the tanks and troops on the ground.

Manufacturing ability also entered into it as a 12.7mm gun could be built with fewer man hours than the fast firing Rusian 7.62 gun. The 7.62 was an excellent gun on paper and in service but required too much effort to manufacture and service. ... The Russians tended to like heavy armament if they could get it without sacrificeing too much else. The late model LA fighters went from 2 20mm guns to 3 guns when a new lighter weight gun was developed. The Russians wanted 3 or 4 cannon, they just knew their aircraft could not carry them without an unacceptable loss of performance.

The Soviet ShKas was an excellent 7.62mm machine gun, significantly better (more destructive / more throw weight) than any Anglo-American guns with up to three times the rate of fire, but it's still a .30 caliber weapon. The Soviets preferred the 12.7mm gun mainly due to heavier hitting power and better armor penetration. They made something like 150,000 ShKas machine guns so I don't think production was actually the issue.

The Russian 20mm cannon was a rather pedestrian gun. Since the cartridge was basically a necked up 12.7mm machine gun case (not exactly the same one that saw wide spread service) it was in the lower 1/2 of 20mm cartridges in regards to power. The gun itself was on the light side and not particularly durable but it was rather easy to make and reliable. However it should not be a surprise that the Russians were looking at alternatives to it. Like the larger calibers, the late war lighter 20mm allowing more guns to be fitted, the 23mm guns, especially the short 23mm cartridge guns that showed up immediately post war ( development started during the war) so the Russians were persuing multiple avenues of improved gun performance.

You have often disparaged the ShVak 20mm but we know that while the Hispano-Suiza 20mm on the Spitfire and Hurricane (etc.) was more powerful it was also heavier and had serious issues with stoppages / jams particularly in the early to mid-war so it wasn't perfect either.

New capabilities with larger and more efficient guns (the ultra light Berezin B-20 and the more powerful VYa-23 or Nudelman Rikhter NR-23mm cannons) only when more difficult to destroy targets presented themselves, i.e. greater armor penetration was needed against both ground targets (heavier tanks i.e. Panther and Tiger etc.) and more heavily armored fighter bombers such as the Fw 190 and HS 129. But for most of the war the single 20mm was sufficient.

The point being was that the Soviet wartime design philosophy was based on the idea of "exactly enough", vs. the American mentality of "overkill". Both had their merits, both were tailored to the economic and Strategic realities faced by each nation. The Americans had a safe production base and more than sufficient supply / logistics. The Soviets had to move their factories over the Ural mountains and rebuild them in remote villages and forlorn Central Asian outposts. They did not have excess capabilities to spare but wanted to get as many machines into action as possible, of just good enough quality to impose steady attrition on the Germans and win battles when sufficient forces were concentrated.

Obviously there is a fine line - they could have stuck with I-15's, I-16's and LaGG-3s and made 2 or 3 times as many fighters, but they knew that would have been unsustainable in terms of losses. As it was they took horrific losses, but they did respond to realities on the Front by tailoring their aircraft to battlefield lessons, producing the ones which worked the best and continuously improving them. Again not the same way as in Anglo-American armies but with much more experimentation and incremental changes, with far more diverse variants actually seeing combat. This way cost them lives no doubt but it also meant their 'meritocratic' process produced the aircraft they actually needed. In the first year of the war they learned a great deal what worked and what didn't (the hard way), and by 1942 their designs were sound. The biggest problem with their aircraft was not with design in fact at all but with production quality, and that was beginning to clear up by the end of 1942.

It's the same with Soviet tanks and everything else they did.

 

[Ivan1GFP]

 

[Schweik]

Hello Schweik,

From what I have been able to find, there is very little mention of loading OVER 200 rounds per .50 cal cowl gun except in one flight test and in the Russian manual on the P-39. Other reports mentioning ammunition loads have stated 200 rounds as a full load.
I believe the reduction in fuel capacity in the late model Airacobra was at the request of the Soviets and not of anyone else though there is also mention that fuel capacity can be restored if needed.

I don't know anything about ammunition loadouts except that I know they tinkered with both guns and ammunition carried in the field generally speaking, including removing guns and adding or removing ammunition. With fuel I know for a fact that it was also routine for point defense (going back to Java in early 1942) to load aircraft with less than the normal fuel load before combat, mainly to increase rate of climb. This was done with Hurricanes, Buffaloes and P-40's. It was also done in New Guinea, in the MTO (including even with Spitfires) etc. It's a rather obvious expedient.

I believe the 37 mm would have been more useful against a big target such as a B-17 than in pulling a deflection shot against another fighter. It gets even worse when you consider that the ballistics of the cannon is so different from the two cowl guns that if one is one target, the other won't be.

And yet, Soviet pilots reported that they liked the 37mm gun and they did not necessarily use deflection shots. They tried to hit with the first round or two (as the gun often, especially in the early days, jammed after 2 or 3 rounds anyway) and from very short range. They also liked it for the intimidation factor in face to face encounters, which the Germans learned to avoid against the P-39. I assume you already know this but if you really need me to I can pull down a book and transcribe some Soviet pilot accounts.

The problem with this statement is what "for their era" means. A Hurricane or Macchi C.200 wasn't really a competitive fighter past about 1940-1941 at the latest. The faster than a A6M2 is a probably but by how much. Combat reports suggest that the Airacobra's speed advantage in combat was VERY small.
In various places, the opposition was pretty low tech (Think Italian biplanes and Ki 27) and fighters that were not suitable for front line service elsewhere could still do the job well enough. That is probably why aircraft such as the P-40, Hurricane and even Gladiator were used effectively for a while. That does not mean that they were really up to standards.

Amusing invocation of an old cliche. As I have already pointed out, P-40's were still being used with considerable success on the front lines in not just Russia but also in Italy and throughout the CBI as late as 1944, whereas Gladiators were retired by then and Hurricanes were getting slaughtered wherever they were still used (mostly in the CBI). So bunching them together is absurd.

The late model P-39 on paper has speed considerably better than a P-40 though - P-39N could make just below 400 mph at 57" H (and at 10,000 ft), more than 20 mph faster than the P-40N and comparable to contemporaneous Bf 109s and Fw 190s at those altitudes. It also had an excellent rate of climb at that altitude. With the removal of the wing guns and other field mods, perhaps the Soviets actually achieved the rated performance.

http://www.wwiiaircraftperformance.org/P-39/P-39N_level-speeds.jpg

P-40N manual states maximum diving speed is 496 MPH IAS.
It also states that the aircraft will yaw to the right when diving. This suggests that the typical trim / offsets even on the P-40N are such that above a certain speed, aerodynamic effects will still cause a pull to the right and below that speed, there will be a pull to the left.

I have already pointed out several times, and I know you read it, that the number 1 Curtiss test pilot Herbert O. Fisher routinely dove the thousands of P-40s he did acceptance flights on at over 500 mph TAS. Here is the exact quote to refresh your memory:

"The standard procedure for an acceptance flight was a one-hour check of all major systems. Fisher had a specialty, he would take an aircraft up to "20,000, strain the engine upward, then go inverted, throttle full forward, and nose it over, losing 10,000 feet or more at 500mph+. He knew it was almost impossible to tear a P-40 apart in a dive, which was a HUGE advantage over the Zero. He knew the operating parameters of that airplane and almost every rivet."

In comparison, this is not an extraordinarily high diving speed. I believe the Ki 84 manual lists 475 MPH IAS which isn't far off.

No the Ki 84 is quite fast too, but it's a very late war plane that didn't get into combat until for example fairly long after the introduction of Me 262 jets. My point however isn't that diving at 500 mph was unique - it certainly wasn't, but that the trim problems faced were mostly in those high speed dives and the P-40 which was in action from 1941 through 1945 was one of the first to routinely have to contend with control at such speeds. As you are no doubt aware many other aircraft such as the P-38 and P-47 faced compressibility problems in high speed dives and almost all the Soviet fighters had much lower dive speed limitations due to the way they were constructed.