P-39 vs P-40

[tomo pauk]

Ok Tomo, you seem to be moving the bar a bit here, and I'm not sure precisely what you are getting at? You tell me why they (obviously quite on purpose) created low altitude fighters with low-altitude rated engines?

Or are you claiming that they didn't?

They certainly did, the low-altitude versions of Merlins are listed at the tables I've posted at post #170 here.
Low-altitude Merlins were created in order to improve performance down low. These come in handy once the threat emerged - Fw 190s armed with bombs, trying to make hit & run attacks against the targets in UK proper. Typhoon was barely available and beset with problems, Griffon was running late.
Low-alt Merlins were also used on 'hooked Spitfires' and Seafires, where improved low-alt power obviously improved take-off properties and enabled carrying more, as well (but not exclusively) on bomb-armed Spitfires.

Low-alt Spitfires usualy sported clipped wings, in effort to improve rate of roll. The Spitfires VIII and XI were produced in LF, F and HF versions, actual difference being the sub-type of 2-stage Merlin aboard. Usually the LF (L for low altitude) was with clipped wings, HF (H for hi-alt) was with extended wingtips; F was with standard wings.

 

[Schweik]

Well the Fw 190 Jabos were in full effect in Sicily and Italy by 1943 (and in fact were already being used in Tunisia in 42) so lets try not to forget that perpetually overlooked part of the war... though Ju 87 and Ju 88 and the other aircraft I mentioned were important there as well (much longer than in North West Europe).

As to how easy they were to kill, I am not certain about that, the survival rate of Ju 87s was perhaps surprisingly pretty good in North Africa, most of the casualties on both sides were fighters. Ju 88's were also pretty elusive though that seems to have been due more to high altitude performance generally (Hurricanes in particular had a hard time catching them over the Med). But I think extra speed and agility near sea level was particularly helpful for catching torpedo planes down low. 'Fritz' carrying bombers also seemed to be a significant threat that needed to be quickly neutralized especially during amphibious operations such as were repeatedly taking place in the Med in 1943.

I'm not convinced that the only reason LF spits and low altitude / cropped merlins were made was due to Fw 190s fighting over England or the Channel, but it's immaterial to the discussion really. My original point was simply that aircraft which performed well down low did have a role and were valuable. The "Bomber Mafia" and other generals may have only liked the high flying 4 engine bomber escorts but a lot of the fighting worldwide was done on the deck.

To reiterate my previous point destroying or protecting dive bombers, torpedo bombers, heavily laden (and thus relatively defenseless) fighter bombers and strafer / attack aircraft was the main mission of fighters in many if not most Theaters of WW2. Some units may have preferred to focus on racking up kill ratios against whatever the easiest targets were at any given moment, but this probably contributed to their defeat.

Four engine heavy bombers were only flying in the daylight under American auspices as far as I know, and the really long range (and thus, more damaging) raids didn't get going until near 1944. And while they no doubt affected the war, especially through attrition of the Luftwaffe and the Japanese air forces, I don't think you can say that they decided the outcome of the war. The crucial battles were fought earlier and they were Tactical battles, involving land armies or navies. And in those fights the lower flying fighters actually mattered more, most significantly on the Russian Front but also in the Med and Pacific.

S

 

[tomo pauk]

Well the Fw 190 Jabos were in full effect in Sicily and Italy by 1943 (and in fact were already being used in Tunisia in 42) so lets try not to forget that perpetually overlooked part of the war... though Ju 87 and Ju 88 and the other aircraft I mentioned were important there as well (much longer than in North West Europe).

The Jabo Fw 190s were operating very much in 1942 over the Channel.

As to how easy they were to kill, I am not certain about that, the survival rate of Ju 87s was perhaps surprisingly pretty good in North Africa, most of the casualties on both sides were fighters. Ju 88's were also pretty elusive though that seems to have been due more to high altitude performance generally (Hurricanes in particular had a hard time catching them over the Med). But I think extra speed and agility near sea level was particularly helpful for catching torpedo planes down low. 'Fritz' carrying bombers also seemed to be a significant threat that needed to be quickly neutralized especially during amphibious operations such as were repeatedly taking place in the Med in 1943.

For the n-th time - 'ordinary' Spitfires have had plenty of performance to catch any bomber fielded by Axis, whether a Ju 88 at 15000 ft or SM.79 at 500 ft. But for catching Jabo Fw 190s, Spitfires needed any help they can get, and low-alt Merlins gave them some 150 HP extra down low.
The Do 217s with Fritz X bombs were flying at medium altitudes.

I'm not convinced that the only reason LF spits and low altitude / cropped merlins were made was due to Fw 190s fighting over England or the Channel, but it's immaterial to the discussion really. My original point was simply that aircraft which performed well down low did have a role and were valuable. The "Bomber Mafia" and other generals may have only liked the high flying 4 engine bomber escorts but a lot of the fighting worldwide was done on the deck.

Have you actually read the post above, where the other users of low-alt Merlins are listed?
Low-level fighters did have a role, quirk being that hi-alt fighters were priority in at ETO and MTO, plus in Asia/PAcific. Once that priority is satisfied, the lo-alt fighters were made and pressed in service (or not, in Japanese case). Bomber mafia got many things wrong, however high flying escorts were needed to bring the 'daylight war' to German proper.
It was far easier to turn a hi-alt fighter into low-alt, than vice-versa.

To reiterate my previous point destroying or protecting dive bombers, torpedo bombers, heavily laden (and thus relatively defenseless) fighter bombers and strafer / attack aircraft was the main mission of fighters in many if not most Theaters of WW2. Some units may have preferred to focus on racking up kill ratios against whatever the easiest targets were at any given moment, but this probably contributed to their defeat.

Four engine heavy bombers were only flying in the daylight under American auspices as far as I know, and the really long range (and thus, more damaging) raids didn't get going until near 1944. And while they no doubt affected the war, especially through attrition of the Luftwaffe and the Japanese air forces, I don't think you can say that they decided the outcome of the war. The crucial battles were fought earlier and they were Tactical battles, involving land armies or navies. And in those fights the lower flying fighters actually mattered more, most significantly on the Russian Front but also in the Med and Pacific.
S

Outcome of war was not decided by P-40s either, that was decided by many sacrifices at Allied side and German mistakes - boy, did they made them. P-40 was not there to decide BoB, and it's influence in survival of Soviet Union in 1941-42 was minimal. 4-engined bombers flew against Germany most of 1943, wheather & losses .permitting. That they didn't achieved more was due to lack of suitable escort.
In Pacific both Allied and Japan were very much interested in hi-alt aerial warfare, and acted accordingly. USN predominatly used fighters with 2-stage engines, AAF wanted turboed engines ASAP, while Japanese engines have had better hi-alt capabilites than V-1710s as installed on P-40s.

 

[varsity07840]

My bad - I was thinking of Port Morseby, and apparently some other towns in Australia.

Aussie P-39 Airacobra – Emergency Defender

P-39 Airacobras in defence of Australia | The Australian War Memorial



All true. Part of what a fighter has to be is versatile. P-47s and Corsairs were never (originally) intended for ground attack and were in some respects unsuited, but the radial engines and heavy carrying capacity proved valuable in that role. Spits and 109s weren't really meant for bomber escort but they had to do it.

It's interesting to note that the "Emergency Defender" article mentions that the P-39 had poor altitude performance due to the lack of "an effective turbo-supercharger". The inference being that fighters with good altitude performance had turbo chargers when in fact most did not. There's a similar misunderstanding about stage speed vs. two stage engines. In some cases writers have claimed that the P-39 and P-40 did not have supercharging.

 

[wuzak]

Yes but lets be real the LF Spit Mk V, many regular Spit V, recon Spit IV and various others were using other specifically low altitude optimized Merlin engines like the Merlin 45, 45M, 50, 50M etc. some of which had cropped impellers specifically for low altitude power. For example Merlin 45M had a critical altitude of 2,750 ft (838 m) where it gave 1585 hp. Interestingly this is about the equivalent of the P-40K (which the English liked quite a bit) at normal / sanctioned WEP settings.

For your information, the Spitfire PR.IV (nee ID) was an unarmed high altitude long range reconnaissance aircraft. Fitting a low critical altitude engine would have been dumb. So they fitted the 45.

 

[Schweik]

Outcome of war was not decided by P-40s either, that was decided by many sacrifices at Allied side and German mistakes - boy, did they made them. P-40 was not there to decide BoB, and it's influence in survival of Soviet Union in 1941-42 was minimal. 4-engined bombers flew against Germany most of 1943, wheather & losses .permitting. That they didn't achieved more was due to lack of suitable escort.
In Pacific both Allied and Japan were very much interested in hi-alt aerial warfare, and acted accordingly. USN predominatly used fighters with 2-stage engines, AAF wanted turboed engines ASAP, while Japanese engines have had better hi-alt capabilites than V-1710s as installed on P-40s.

I never made such grandiose claims for the P-40. No single aircraft or any other piece of equipment decided the outcome of the war, not the P-51, not the Spitfire or the Sherman tank or the Aircraft Carrier. Not even the A-bomb.

But I will help you out - I will say that think the P-40 did play a significant and generally little known role in the crucial mid-war battles in all three Theaters you just mentioned

• Russia - particularly in the key battles at Moscow and Leningrad
• In the Med - where it was the main air superiority fighter until August 1942 at the earliest and maybe the most important Allied Tactical bomber as well)
• and the Pacific -where according to the local ground commander it played the "decisive role" in the critical battle of Milne Bay* and contributed significantly to the defense of Darwin and the fighting around New Guinea and in the Solomons.

• And finally in the CBI it clearly was the most important Allied fighter and significantly helped keep the Chinese in the war.

A bunch of other Allied fighters were equally important during 1942 - the Hurricane, Yak 1, LaGG-3, Wildcat, P-39, early P-38 and Spit V, but I think the P-40 was clearly a major part of many of the decisive battles during the turning point of the war - where victory or defeat in fact hinged on low altitude combat. Even at times where the fighting took place at higher altitudes in these Theaters, such as over Darwin, the aircraft proved versatile enough to remain effective.

And Northwest Europe wasn't the only important Theater in WW2.

S

* "After the war, the Australian Army commemorated the battle through the awarding of a battle honour titled "Milne Bay" to a number of the units that took part. The units chosen were the 9th, 25th, 61st, 2/9th, 2/10th and 2/12th Infantry Battalions.[170] The two RAAF fighter squadrons that had taken part in the fighting were also singled out for praise by the Australian commanders for their role in the battle. Rowell stated: "the action of 75 and 76 Squadrons RAAF on the first day was probably the decisive factor", a view Clowes endorsed in his own report.[171] "

 

[Schweik]

It's interesting to note that the "Emergency Defender" article mentions that the P-39 had poor altitude performance due to the lack of "an effective turbo-supercharger". The inference being that fighters with good altitude performance had turbo chargers when in fact most did not. There's a similar misunderstanding about stage speed vs. two stage engines. In some cases writers have claimed that the P-39 and P-40 did not have supercharging.

Again, I'm not an expert on Spitfires or Merlins, but I was going by the description of the Merlin 45 here as "A variant of the Merlin XX fitted with single-stage, single-speed supercharger for low altitude Spitfire use. First production Merlin 45 delivered 13 January 1941.[6] First of specialised engines for Spitfire Mk V variants and early Seafires. "

Spitfire PR Mk. IV was listed as one of the aircraft fitted with the engine. I think they did also require low altitude recon aircraft due to the limitations of cameras back then, certainly the Spit Mk IV's operating in the Med seemed to get shot down at low altitude more than once.

Are you saying that description is wrong?

 

[wuzak]

Ok Tomo, you seem to be moving the bar a bit here, and I'm not sure precisely what you are getting at? You tell me why they (obviously quite on purpose) created low altitude fighters with low-altitude rated engines?

Or are you claiming that they didn't?

They did, for the express purpose of fighting Fw 190 intruders over England. They were aircraft modified for the purpose, using modified engines.

The IX had started operational service in mid 1942, but its engine (Merlin 63) was high altitude rated. The LF.IX doesn't appear until 1944. The LF.IX used the Merlin 66, which was stronger, so could take more boost, and had different gearing so it had a lower critical altitude. At +18psi boost the 66 had a critical altitude of 5,250ft in low gear and 12,500ft in high gear.

Note that the Merlin 66 was built under licence by Packard as the 266 for British service and as the V-1650-7 for American service. The V-1650-7 saw use in the P-51B and P-51D, neither of which would be considered low altitude fighters.

The reason to go from the V-1650-3 (Merlin 63) to the lower critical altitude -7 was the increase in mid-altitude performance.

 

[Schweik]

They did, for the express purpose of fighting Fw 190 intruders over England. They were aircraft modified for the purpose, using modified engines.

I am really not sure what you or Tomo are driving at aside from "I'm right / you're wrong".

What I originally said that started this avalanche of posts, was that there was an actual purpose for low altitude fighters, and that they were made intentionally. I mentioned LF Spitfires as one example, the LF Mk V was in fact made with a variety of early low altitude rated Merlin engines of which I already mentioned several examples - Merlin 45 and 45M, 50 and 50M, and Tomo also pointed out the Merlin 32.

The Tempest and Typhoon were also low altitude fighters.

And almost all of the Soviet fighters were low altitude fighters -and no this was not done after they had already secured a sufficient number of high-altitude fighters. The one high altitude fighter they had, the MiG 3, they basically thought was useless because it performed badly down low, and they thought the P-47 was "not a fighter" to quote the evaluation verbatim.

The early Zeros by the way, did not have very high altitude performance ceilings either, nor did Hurricanes at least not in the Med (they were often unable to intercept high flying aircraft over Malta for example) nor quite a few other early and mid war fighters.

 

[tomo pauk]

Again, I'm not an expert on Spitfires or Merlins, but I was going by the description of the Merlin 45 here as "A variant of the Merlin XX fitted with single-stage, single-speed supercharger for low altitude Spitfire use. First production Merlin 45 delivered 13 January 1941.[6] First of specialised engines for Spitfire Mk V variants and early Seafires. "

Spitfire PR Mk. IV was listed as one of the aircraft fitted with the engine. I think they did also require low altitude recon aircraft due to the limitations of cameras back then, certainly the Spit Mk IV's operating in the Med seemed to get shot down at low altitude more than once.

Are you saying that description is wrong?

The description is wrong.

 

[Schweik]

The description is wrong.

Ok so did they or did they not put Merlin 45M into Spitfire LF Mk V fighters?

 

[wuzak]

Again, I'm not an expert on Spitfires or Merlins, but I was going by the description of the Merlin 45 here as "A variant of the Merlin XX fitted with single-stage, single-speed supercharger for low altitude Spitfire use. First production Merlin 45 delivered 13 January 1941.[6] First of specialised engines for Spitfire Mk V variants and early Seafires. "

Yes.

The supercharger was the same as the XX.

The XX had gear ratios of 8.15:1 (low gear) and 9.49:1 in high gear.

The 45 supercharger gear ratio was 9.09:1.

So while the 45 had a lower critical altitude than the XX in high gear, it still had a relatively high critical altitude for 1941.

Spitfire PR Mk. IV was listed as one of the aircraft fitted with the engine. I think they did also require low altitude recon aircraft due to the limitations of cameras back then, certainly the Spit Mk IV's operating in the Med seemed to get shot down at low altitude more than once.

The PR.IV carried the same cameras as the PR.IX and PR.XIX, so I doubt cameras were a problem.

Photo Reconnaissance Spitfires

Would need citation on the PR.IVs being shot down at low altitude.

 

[wuzak]

Ok so did they or did they not put Merlin 45M into Spitfire LF Mk V fighters?

The 45M is a modified 45, hence the M.

Your description was for the regular 45.

 

[varsity07840]

My bad - I was thinking of Port Morseby, and apparently some other towns in Australia.

Aussie P-39 Airacobra – Emergency Defender

P-39 Airacobras in defence of Australia | The Australian War Memorial



All true. Part of what a fighter has to be is versatile. P-47s and Corsairs were never (originally) intended for ground attack and were in some respects unsuited, but the radial engines and heavy carrying capacity proved valuable in that role. Spits and 109s weren't really meant for bomber escort but they had to do it.

It's interesting to note that the "Emergency Defender" article mentions that the P-39 had poor altitude performance due to the lack of "an effective turbo-charger". The inference being that fighters with good altitude performance were turbo-charged when in fact that's not the case. There is a similar confusion between two speed and two stage engines. Some writers have claimed that the P-39 and P-40 did not have superchargers.

 

[tomo pauk]

Ok so did they or did they not put Merlin 45M into Spitfire LF Mk V fighters?

They did.
I'm not sure how many times it needs to be said: Merlin 45 and 50 were 'normal' Merlins, all-altitude if you want. Merlin 45M and 50M were low-alt versions, used where low-alt performance was a paramount, offering up to 10% more power down lwo, while having less power at mediu and high altitudes than 'normal' versions.

 

[P-39 Expert]

But that isn't actually true. You didn't understand what you have been reading. Performance, especially climb, fell off starting at 12,000 ' and climb rate was no doubt very bad by 20,000', but that was not the ceiling. They routinely intercepted enemy bombers flying much higher than that. You should read this article which I posted previously, about the use of P-40s in the defense of Darwin. From March to September 1942, Japanese records confirm that novice P-40E pilots from the 49th FG were able to shoot down 12 "Betty" bombers flying at 27,000' in spite of a heavy escort of A6M2s so not only were they able to fly that high, they were fairly effective in combat (albeit with heavy losses of their own) .

Quote from the article:

"Darwin's 3.7-inch anti-aircraft artillery forced the G4Ms to ingress at high levels—generally between 25,000 to 27,000 feet. Such a high ingress altitude sorely tested the P-40E fighters as their Allison V-1710 engines suffered from an inadequate mechanically driven supercharger. The Allison, while rugged and reliable, lost considerable power at the higher altitudes, with the operational ceiling of the P-40E limited to around 27,000 to 28,000 feet."

In fact the only US fighters I'm aware of which were literally unable to attack high flying bombers during the war were P-39s / P-400s' over Guadalcanal and that was apparently due to a lack of suitable oxygen equipment. P-39s were also active at Darwin but I don't know of any stats on their use there, do you?

The Darwin campaign was an early experiment, efficiency got much better. AVG and later 23rd FG etc. were routinely shooting down high flying Japanese bombers all through the war with P-40E, K and later N with minimal and diminishing losses.

S

I have read those articles and there is no way possible on this earth that a P-40E ever intercepted ANYTHING at 27000'. It's absolute ceiling was 31000' and it's rate of climb at 27000' was 250fpm. It took a staggering 30+ minutes to climb to 27000' under test conditions (not combat). At 27000' it's top speed was 250mph. It couldn't intercept anything at that altitude.

The Bettys that they intercepted couldn't even get that high. The altitude figures in that article had to be a mistake or an exaggeration. Just my opinion.

 

[Schweik]

Yes. The supercharger was the same as the XX.

So while the 45 had a lower critical altitude than the XX in high gear, it still had a relatively high critical altitude for 1941.

Well I guess it depends on your definition of low altitude. The P-40F (also made in 1941) and L had a Merlin 28, essentially Merlin XX, and a critical altitude of about 20,000 ft. Which is considered low - certainly not high enough for escorting B-17s. According to this page Merlin 45 had 1,515 hp at 11,000 ft and 1,210 hp with +3 boost at 18,000 ft which sounds kind of similar. Is it wrong?

Would need citation on the PR.IVs being shot down at low altitude.

A while back I think I posted a bunch of data from Shores MAW Volume III in one of the air battles a Spit IV PR blundered into a dogfight between P-40s and Bf 109s and got shot down by the latter, I think it's in the p-40 vs. 109 thread which I believe you also posted to.

The 45M is a modified 45, hence the M. Your description was for the regular 45.

This is from the wiki:

List of Rolls-Royce Merlin variants - Wikipedia

Merlin 45M 1,230 hp (917 kW) at 3,000 rpm 1,585 hp (1,182 kW) at 3,000 rpm, +18 psi (124 kPa) boost, 2,750 ft (838 m) Spitfire LF Mk.V Version of Merlin 45 with "cropped" (smaller diameter) supercharger impeller allowing greater boost at low altitudes.

 

[Schweik]

They did.
I'm not sure how many times it needs to be said: Merlin 45 and 50 were 'normal' Merlins, all-altitude if you want. Merlin 45M and 50M were low-alt versions, used where low-alt performance was a paramount, offering up to 10% more power down lwo, while having less power at mediu and high altitudes than 'normal' versions.

So I don't know how many times I have to say this - there was a purpose and a need for low altitude fighters. And the Spit V LF was one example. It matters very little to me if that used a Merlin 45 or a 45M or a 50M or whatever. Point is it wasn't just for Seafires.

By the way Wiki also mentions that the "low altitude" merlin 32 was also used on the Spitfire PR Mk. XIII (with citation from The Spitfire Story. London: Jane's Publishing Company Ltd., 1982. ISBN 0-86720-624-1. pages 182 and 185)

 

[Schweik]

I have read those articles and there is no way possible on this earth that a P-40E ever intercepted ANYTHING at 27000'. It's absolute ceiling was 31000' and it's rate of climb at 27000' was 250fpm. It took a staggering 30+ minutes to climb to 27000' under test conditions (not combat). At 27000' it's top speed was 250mph. It couldn't intercept anything at that altitude.

The Bettys that they intercepted couldn't even get that high. The altitude figures in that article had to be a mistake or an exaggeration. Just my opinion.

I get that you don't understand it, but you probably just have to read a bit more on the subject to understand how it all worked. History doesn't have to make sense to you, you have to figure it out.

 

[Schweik]

It's interesting to note that the "Emergency Defender" article mentions that the P-39 had poor altitude performance due to the lack of "an effective turbo-charger". The inference being that fighters with good altitude performance were turbo-charged when in fact that's not the case. There is a similar confusion between two speed and two stage engines. Some writers have claimed that the P-39 and P-40 did not have superchargers.

yes I agree it's a common misconception and one of the things I often try to debunk.