A Radial Engined Fighter for the Australians to build (and maybe the Chinese and Indians)

[Wild_Bill_Kelso]

Trying to get back toward the vicinity of the original idea, (not that I mind the thread drift), as you say the wildcat doing 320 or 330 mph up around 18 or 20,000 ft was actually quite useful for example in the Solomons.

Early P-40 can fly that high (and is pretty lethal down under 10k) but it's really floundering at 20,000 feet. And takes forever to get there.

To get around dealing with the Kittyhawks, the Japanese would sometimes send in their twin engined bombers to attack from near their service ceiling. 49th FG eventually worked out tactics to intercept them at Darwin, but due to the poor altitude performance of P-40E, they took a fair number of losses there, fighting at 25 or 26,000 ft.

Spitfire 5 had much better performance at that altitude but a fairly low flight endurance. If the Australians had another plane like a Wildcat that had decent altitude performance and reasonable range, it. could have been useful I think. And that could be either a hypothetical Ozhawk 3 or a Wildcat 3.

Of course a low altitude fighter could be useful too, as the Kittyhawk was. I'm just saying there could have been a niche for something that could fight up there in the thinner air. They did of course get p38s and corsairs in theater, those are still coming in pretty slow for a while.

 

[MiTasol]

Allisons V-1710-33, -39 and -73 were basically capable to produce same power. They have same supercharger impeller diameter, same compression ratio, same rpm.

That is true but it is only part of the truth. And a very very small part at that.

You are totally ignoring the octane ratings and many other factors that are related to developing power and how those factors affect the engine structurally and operationally. Higher octane fuel runs hotter and produces higher pressures in the cylinder. As such the compression ratio is just one significant feature - what happens after that compression is obtained and the spark plug fires is a whole different ball game. The higher temperatures and pressures from higher octane often also require better pistons and rods etc, valves and valve seats and a number of other changes. Because the valves are running hotter the valve stem expands more so that reduces the clearance between the valve stem and valve guide which can cause valves to jam so that mean the internal diameter of the valve guide must be changed. And that is just the tip of the iceberg I had to learn nearly 60 years ago

Throughout the production life of the V-1710 (and every other engine) service experience shows design assumptions that were incorrect, either by mistake or because the spec said that the engine would only need to run on 87 octane because that was the best available at the time. Fuel improved massively throughout the engines life and that make the engine core capable of developing more power than the various components are capable of absorbing without failure.

As a result the engine is modified and one of the reasons they went to the short nose was the long nose gearbox could not take the power the -39 engine produced under combat conditions and higher octane fuel. Likewise the crank case, crank shaft, cylinder blocks and many other major structural components were replaced on later model engines. The crank case on the -33 and -39 are totally different. On the -73 the crankcase and many other parts are different again. The are technically interchangeable but in practice not because the mounting pads are totally different so you cannot fit a -39 crankcase to a Tomahawk or vice versa without modifying the engine mounts. And that is just one very basic example.

Think of the fuel as bullets. Early armour plate was thin as it was only needing to survive 30 cal or similar ammo. Then along comes a higher octane (say the 50 cal) and that armour (engine structure) must be made stronger. Then along comes even higher octane (lets call that the 20mm) and once again the armour (engine structure) must again be upgraded. And that is without getting into the different types of ammo (ball, SAP, AP, etc) which all require more changes. In the case of the engine it may be a vibration issue or that changing a specific component (the Allison went through four major bearing configurations by early 43) will increase the time between overhauls and reliability in the field.

 

[Shortround6]

We are talking about a few different things here.

For the V-1710 we are talking about IF the engine can produce a certain amount of power at a certain altitude which is pretty much dependent on air flow, how much air the engine and supercharger can flow though the engine. This can change with the supercharger gear ratio.
Wither the engine can survive that level of power for more than a few minutes or even seconds is a different thing. And that gets split into two areas.
1, Does the fuel have a knock rating (octane/performance number) that will allow operation at the level of boost without the fuel detonating in the cylinders before/during the normal ignition period.
2, Does the engine have enough mechanical strength to stand up to the loads imposed on it by the higher pressure in the cylinders without parts breaking.

we will disregard cooling for now.

Farky was correct in his statement. The Chart I linked to shows the V-1710-33 engine was capable of making just over 1700hp at sea level with no RAM.

This does not mean it was a good idea. Allison got in a lot of trouble after that chart was made. Allison wanted to "rate" the engine at 1040hp and there is a lot of charts/tables showing the 1040hp rating. The Army wanted to rate it at 1090hp at a slightly lower altitude. The US wanted the engine to last for 150 hours on it's type test (most other countries were happy to test engine for 100 hours) and it took four tries and a change in the engine mount on the test stand to get the engine to get through the 150 test. However by this time several hundred engines had been built and installed in P-40s. Allison had to take 277 (?) of the US engines (they never took back any of the early British ones) and rebuild them with new parts.
However, this only gets things to about the 1940/41 stage. Allison introduced a new crankshaft (the 3rd one) around Dec of 1941, this was well into the -39 production run.
It was this crankshaft and the experience with it that let Allison engineers decide to rate the -73 engine at 1325hp for take-off in the summer of 1942.

For the Allison there was a 4 crankshaft that was used later on the P-38s (P-38s went through the same series of crankshafts) and on the engines in the P-63. that 27lbs of counter weights and on some engines was allowed to run at 3200rpm.

What the engine with put up with for 5 minutes or even for repeated 5 minute intervals is different than what it would put up with for the "military" rating but those are lower ratings than what the engine will actually make at high boost even if the fuel allows it.

fuel is a different post.

 

[Wild_Bill_Kelso]

All of this to me means that tomahawks, which we're mostly used by the British and the Soviets, (plus that 100 used by the AVG and a few at Pearl Harbor) we're probably not in most cases being run at 1400 horsepower let alone 1700. If they were pushed that hard in an emergency, the pilot was playing Russian roulette with the engine. Kittyhawks however, clearly we're being run at the higher horsepower settings probably 1400 or so, sometimes more, by mid 1942 in the Middle East and maybe earlier in the Pacific. Interestingly in both the Middle East and the Pacific it seems that it was Australian units that were key in figuring out what the new limits really were. Although Russian pilots notably Golodnikov, also mentioned increasing RPM.

And I think this evolution of increased power with the Allison is not all that unusual with other military engines in use during the same periods.

 

[Wild_Bill_Kelso]

But I guess it happened a little more slowly with the r1830

 

[tomo pauk]

All of this to me means that tomahawks, which we're mostly used by the British and the Soviets, (plus that 100 used by the AVG and a few at Pearl Harbor) we're probably not in most cases being run at 1400 horsepower let alone 1700. If they were pushed that hard in an emergency, the pilot was playing Russian roulette with the engine. Kittyhawks however, clearly we're being run at the higher horsepower settings probably 1400 or so, sometimes more, by mid 1942 in the Middle East and maybe earlier in the Pacific. Interestingly in both the Middle East and the Pacific it seems that it was Australian units that were key in figuring out what the new limits really were. Although Russian pilots notably Golodnikov, also mentioned increasing RPM.

And I think this evolution of increased power with the Allison is not all that unusual with other military engines in use during the same periods.

(my bold)
I'd say that evolution of increased power with the V-1710 is/was unusual when compared with other military engines. It started with barely above 1000 HP in 1940 (service engines), jumped to almost 1600 HP in 1942, and to 1850 HP in 1944 with water/alcohol injection on P-63s. The turboed V-1710s were also there with 150 grade fuel. Apart from the Merlin, I can't think of any engine that made such a jump in 4 years.
Yes, the DB 601/605 made a similar % jump if we lump the 601 and 605 together, although it took them some 12-15-18 months more.

Access to better fuel was a crucial factor, granted.

 

[Shortround6]

Shifting over to the fuel area you will find a marked difference in the rate of increase in power between liquid cooled engines and air cooled engines. This is a generalization but bear with me.
This is both fuel related and engine construction related.
Air cooled engines were much closer to overheating when running at high power. There wasn't much room to increase boost without sending the engine into the red zone.
On an radial air cooled engine each cylinder had to supply it's own strength to hold the cylinder to the crankcase. Number and size of bolts and/or studs. On a liquid cooled engine each cylinder was part of a block. The load/s could be shared, at least somewhat, through the adjacent cylinders.

On a lot of radials each increase in power was accompanied by both changes in the size and pitch of the cooling fins and changes in construction. For the Wright Cyclone they were on the 4th crankcase and crankshaft after breaking the 1000hp barrier to get to 1300-1350hp. each jump from 1000hp to 1100hp to 1200hp to 1300hp required a new crankcase and crankshaft. And each step required major changes in the size/number of the cooling fins.

You could have poured 100/130 fuel into the fuel tank and turned the boost screw but if you turned the screw very far you were either going to melt holes in the pistons or launch cylinder heads/cylinders right out through the cowl.
The unseen cost of pouring in the super fuel and tweaking the boost screw is that the supercharger takes more power to drive and it heats the intake charge more and this heats up the engine more. It passes right through the engine. make the intake mixture 100 degrees hotter and the cylinder temperature will wind up 100 degrees hotter (not counting the increase heat of combustion) and the exhaust gas temperatures will be 100 degrees hotter.

On either engine if you change the gear ratio of the supercharger you can get the engine to flow more air and make more power by burning more fuel. But things start getting tough.
The heat load you are dealing with is not directly related to the power to the crankshaft. The heat load includes the internal friction of the engines, the power to run the supercharger and power to run pumps/accessories. The power to run the supercharger is big variable but in order to get a 20% increase in power to the prop you may have to make 30% more power inside the cylinders which means you have to cool the engine with 30% more air or water. Made up number for illustration.

more later.

 

[Farky]

You're forgetting that most of the hawk 81s used in combat we're not used by the us but rather by Commonwealth and Soviet units. Some of which were still flying them as late as 1943 (one SAAF unit at least)

I am not forgeting that. Some Hawks 81 were indeed in combat units at the end of 1942, but not in USAAF service. Establishment of War Emergency Rating was in jurisdiction of USAAF Material Command, they really didn't care about some SAAF squadron in Africa flying last combat Tomahawks in theater (soon to be replaced by Kittyhawks anyway, in January 1943) or few airplanes somewhere in Soviet Union.

I agree that the wildcat was not faster, but it was probably more useful against certain kinds of bombing raids. And I think the hypothetical two-speed hawk 75 probably would be as well definitely a two stage

...
I think it would be better for intercepting high flying bombers, or for escorting say b17s or B24s. In that Theater I think it would be at least as good probably better than an Aircobra and probably easier to maintain

...
Depending on exactly what the performance at altitude would be I think it could have been better than Kittyhawk I or Ia

I don't know, I am still not convinced that two-speed Hawk 75 would be any better than P-40 or P-39. We know how good can Hawk 75 with two speed supercharger be, Mohawk IV (ex Hawk 75A-4 for France) was Hawk 75 with two-speed superchargered Wright Cyclone. They were of course fighting in CBI and be able to hold their own against Oscars, in low-ish altitude. It was airplane with rather poor performance for year 1942, barely average fighter even for CBI. They were lucky they faced Oscar, another barely average performer. They were not used as high altitude interceptors, performance in altitude was just weak. We are talking about maximum speed around 320 mph @ 15 000 ft, slightly better performer than Boomerang at least but that's about it.

Also worth mentioning that p40d and e and equivalent were in service a lot longer with Commonwealth and Soviet Union than US. Some were heavily used by Commonwealth & then sent to Soviets.. Some more re-engined with V 1710-73, including (I think) some RAAF

Not really, just as example from SWP - 49th FG was stuck with old P-40Es until July 1943, RAAF retired them from frontline service in September same year. Anyway, point being?

Part of our problem with this discussion is the fact that the speed at altitude is often being left out. The F4F-4s could do about 320mph at just over 20,000ft. British Data card for the Wildcat V says 332mph at 21,000ft. With 1000-1050hp on tap at 20,000ft or so it didn't do too badly over 20,000ft. The problem was they were bog slow at lower altitudes. 292mph at 3,250 ft and 313mph at 13,000ft.
So against a P-40K or earlier the Wildcat could be superior at some where around 20,000ft and up. It was not superior at lower altitudes.

I am just saying that P-40E was faster or just as fast as Wildcat in high altitude. You can easily find data where P-40E is faster than 320 mph or even 330 mph at 20 000 ft. It of course depends which version of Wildcat we are comparing to Kittyhawk, F4F-3 was performing better than F4F-4. I can agree that F4F-3 was better in 25 000 ft or higher than P-40E, F4F-4 not so much. I mean just compare data from RAAF Kittyhawk test (A29-129) with data for Wildcats, you will see that Kittyhawk wasn't really performing bad in high altitude, certainly not worse than F4F-4, at least on paper.

Without 1943 knowledge of radial engine cowlings there is no hope of a P-36 coming close to a P-40 in performance.

I absolutely agree.

Trying to get back toward the vicinity of the original idea, (not that I mind the thread drift), as you say the wildcat doing 320 or 330 mph up around 18 or 20,000 ft was actually quite useful for example in the Solomons.

Early P-40 can fly that high (and is pretty lethal down under 10k) but it's really floundering at 20,000 feet. And takes forever to get there.

Wildcat did a great job in the Solomons, it was combination of good warning system and adequate performance for the task. P-40E was never deployed there and I think that they will be adequate too. Like i wrote, fighters on Cactus got luxury of really early warning against raids, something that wasn't available in Darwin for example, not in 1942.

Early P-40 (E model) was faster or just as fast as F4F-3 or F4F-4 in 20 000 ft, even at 25 000 ft. It takes P-40E about 60 seconds longer to reach 20 000 ft in comparison with F4F-3, F4F-4 is in this altitude even later than P-40E. Same scenario is repeated if we are talking about 25 000 ft. Granted, if you go even higher Wildcat is becoming better than P-40E and got better ceiling (important in Solomons for example).

That is true but it is only part of the truth. And a very very small part at that.

...

I didn't just wrote: "Allisons V-1710-33, -39 and -73 were basically capable to produce same power. They have same supercharger impeller diameter, same compression ratio, same rpm." but also "Now, I am not saying that V-1710-33 was capable to withstand same "abuse" as V-1710-39/-73. It probably wasn't (and some sources sugest that), but I do not believe that it was impossible to have much higher power as WER in V-1710-33. However we will never know."

I agree with your reaction ( well, not with the part that I am ignoring something), I should wrote that "Allisons V-1710-33, -39 and -73 were theoretically capable to produce same power.", that would be better. And even that is technically not true, V-1710-39/-73 should be little bit more powerful than -33 because they got slightly "faster" impeler (Blower gear ratio 8.80:1 vs 8.77:1). I am fully aware that this is much more complicated issue and at least structural limitations of V-1710-33 were for sure lower than in V-1710-39. However all I am saying is that I do not believe that V-1710-33 was hard "caped" at less than 1100 bhp maximum safe power by whatever reason, on the other hand I just don't know. Just as you don't know either where was that critical line for eventual War Emergency Rating for V-1710-33. Theory is nice, but without real live testing we will never know, that is my point.

We can debate little details of course, fuel is very interesting theme for example, but I think this thread got derailed enough.

All of this to me means that tomahawks, which we're mostly used by the British and the Soviets, (plus that 100 used by the AVG and a few at Pearl Harbor) we're probably not in most cases being run at 1400 horsepower let alone 1700. If they were pushed that hard in an emergency, the pilot was playing Russian roulette with the engine. Kittyhawks however, clearly we're being run at the higher horsepower settings probably 1400 or so, sometimes more, by mid 1942 in the Middle East and maybe earlier in the Pacific. Interestingly in both the Middle East and the Pacific it seems that it was Australian units that were key in figuring out what the new limits really were. Although Russian pilots notably Golodnikov, also mentioned increasing RPM.

And I think this evolution of increased power with the Allison is not all that unusual with other military engines in use during the same periods.

You don't know, just because nobody knowes. In theory V-1710-39/-73 was also not supposed to withstand much more than 56/60 inHg @ 3000 rpm and yet pilots were pushing these Allisons well beyond that. Again, I am not saying that V-1710-33 was able to withstand let's say 1400 bhp without critical failure and it is logical that it was not as capable in this regard as later Allisons series E/F so I agree with your post. I don't even remember why are we talking about such things to be honest.

 

[tomo pauk]

Air cooled engines were much closer to overheating when running at high power. There wasn't much room to increase boost without sending the engine into the red zone.

The air cooled types benefited a lot if the water-alcohol injection was added. And doubly so if the fuel was not with high octane rating. Japanese engines picked up 20-30% extra HP via w-a injection.

 

[Wild_Bill_Kelso]

Was that to cool the engine or to concentrate the fuel mixture? What about an intercooler?

 

[tomo pauk]

Was that to cool the engine or to concentrate the fuel mixture? What about an intercooler?

Intercooler is pretty much impossible to quickly retrofit on an 1-stage-supercharged radial.
Advantage of ADI (anti-detonant injection) was twofold - it lowered the mixture temperature so more of it (mixture) could be packed in the cylinders, and acted as an internal coolant, being better in that regard than the overly-rich mixture.

 

[Wild_Bill_Kelso]

Thanks never fully understood that

 

[Shortround6]

The air cooled types benefited a lot if the water-alcohol injection was added. And doubly so if the fuel was not with high octane rating. Japanese engines picked up 20-30% extra HP via w-a injection.

This is true however few American or British radial engines used water Injection.
The Wright R-1820 didn't use it until you got to the "H" series engines, the 1300-1350 and up engines that first start being delivered in Oct 1942, Water injection showed up later. They never tried to use water in the G200 series engines.
I don't think Wright used water on any other engine until postwar? or perhaps on the last B-29s?
Pratt used water on the R-2800 (but only two stage engines until the end of the war) but not on any R-1830s or R-2000s.
Water was used on the Post war R-2800 engines in commercial service for take-off.
Bristol didn't use water until post war?

The Germans used water on the BMW 323 9 cylinder radial.
The Germans used MW/50 on a number of liquid cooled engines.

 

[Shortround6]

In theory V-1710-39/-73 was also not supposed to withstand much more than 56/60 inHg @ 3000 rpm and yet pilots were pushing these Allisons well beyond that. Again, I am not saying that V-1710-33 was able to withstand let's say 1400 bhp without critical failure

The problem here for everybody concerned was that the WER rating was a rating that was established by a test procedure.
In order for an engine to get a WER rating the test engine on a test stand HAD to survive 7 1/2 hours at the the rated power level in 5 minute bursts alternated with 5 minute cool down periods. If the engine broke they tried again at a lower power level.
The US was not interested in what power level they could get for a 1/2 an hour or even for 2-3 hours running before the engine broke.
WER ratings were NOT done by stories saying that squadron so and so used 66in and squadron X saying they used 68 in and the US Material command saying "sounds good, we will try 60in for safety and see how it goes."

The V-1710-33 was a real "time bomb" because it may have used two different crankshafts and two different crankcases. The American engines were all rebuilt to use the 2nd type of parts, British got a mix? Throw that in with a reduction gear known not to stand up to the power that the engine could make if over boosted a lot and Pilots that over boosted -33 engines were taking real chances.
A weird thing about the reduction gear problem was that the gears themselves often didn't fail but that the reduction gears caused a stress in the crankshaft behind the front main bearing and the crankshaft failed there.
Another problem was that the crankshafts were not having critical failures while over boosting or even immediately after over boosting (or at least not all of the time). There was a fatigue problem and the crankshaft often failed one or two flights after the engine had been over boosted.
Trying to put 2 and 2 together and figure out that Sgt Bob had an engine failure 1-3 hours after Sgt Jones had over boosted the engine took a bit of work.
There is one story of Greg Boyington when flying with Flying Tigers trying to land his P-40 and doing a go round and over boosting the engine in process. He claims he doesn't know how much boost was reached for a few seconds but it was enough to blow the glass out of the gauge. He got the plane down and later that day another pilot took off with the plane and the engine crapped out right after take off and the plane ended up in rice paddy. The plane was recovered to be used as spare parts.
Again being a fatigue issue with the crankshaft what an engine survived during it's 1st 50 hours may have been a disaster if the engine was treated that way in it's 3rd 50hours period.
The -33 engines were being used with a suggested max life of 200 hours before being pulled for overhaul. They often didn't make it in service ((often due to other maintenance issues) with the Flying Tigers and one Tiger pilot claims they never over boosted the engines in service.

The main difference (or only difference?) between a -33/39 crankshaft and -71 crankshaft was that while the -33/39 crankshaft was shot peened (at least the later ones?) the -71 engine crankshafts were both shot peened and nitrided. They were interchangeable in the engine blocks.
There is a chart in "Vees for Victory" that shows what the first 3 crankshafts could do at certain stress levels over millions of cycles to failure. The crank in the -71 could last forever at a stress level the old crank would not survive for a short period of time. In the long term the nitrided crankshaft would operate at a stress level about 33% higher than the shot peened crankshaft would.

 

[Wild_Bill_Kelso]

I think you mean - 73. There was also some changes to the crank case and to the bearings right?

 

[Shortround6]

I think you mean - 73. There was also some changes to the crank case and to the bearings right?

Thank you.

There is room for confusion when reading some of this stuff as they often don't identify when change overs occurred.
One part of the text will say that a change was made in a certain month (like new engine block) but not say which engines were affected.

The part about the nitrided crankshaft says it was introduced in early 1942.
The foot note attached to it says that when the V-3420-9 engine was rebuilt in the spring of 1942 it was equipped with two of the nitrided crankshafts (in addition to two of the new engine blocks) and upon completion of the type test this qualified the crankshafts for general V-1710 and V-3420 use.

So when did they introduce them on the production line and in which engines? We assume they got them in -73 engines but we don't know how many, if any, -39 engines got them (or P-39 engines) .

An earlier paragraph is really confusing as it details the improvements made in the "Antioch" process block casting compared to the Alcoa block casting and says what an improvement it made to the V-1710E/F versions compared to the C series engines. Then it goes on to describe that one of the first engines to use the "Antioch" process was the V-3420-9 engine that was rebuilt from Alcoa blocks and passed it's 150 hour test in the spring of 1942. Well.....................in the spring of 1942 there were an awful lot of P-39s and P-40s built with E & F engines that don't appear to use the "Antioch" process unless they have the dates screwed up.

The P-40K was initially ordered on Oct 30th 1941. I have no idea what engine was specified at this point. In May of 1942 the first P-40K (42-45722) was completed about the middle of May 1942 with a -73 engine. The first P-40Ks showed up in Palestine in Aug 1942?

 

[Wild_Bill_Kelso]

Lot of the K seem to end up in China and South Pacific and Russia. They seem to have had a big impact. Aot of Aces flew them, some of the highest scoring P 40 pilots in all three Theaters.

 

[Wild_Bill_Kelso]

Robert Scott's (second) "Old exterminator" was a P-40k. Nikolai Kuznetzov (20+ victory ace, double HSU) got most of his victims on a P-40k. Bobby Gibbes flew one for a while, Robert De Haven got most of his 10 kills with the P 40 onaa K

 

[Wild_Bill_Kelso]

I don't know, I am still not convinced that two-speed Hawk 75 would be any better than P-40 or P-39. We know how good can Hawk 75 with two speed supercharger be, Mohawk IV (ex Hawk 75A-4 for France) was Hawk 75 with two-speed superchargered Wright Cyclone. They were of course fighting in CBI and be able to hold their own against Oscars, in low-ish altitude. It was airplane with rather poor performance for year 1942, barely average fighter even for CBI. They were lucky they faced Oscar, another barely average performer. They were not used as high altitude interceptors, performance in altitude was just weak. We are talking about maximum speed around 320 mph @ 15 000 ft, slightly better performer than Boomerang at least but that's about it.

Interesting. To me that may explain why the Mohawk did pretty well in India.

I'd also say the Oscar, though not a fast plane, was a damn good fighter and for an Allied type to hold it's own with a Ki-43 is a positive sign.

Not really, just as example from SWP - 49th FG was stuck with old P-40Es until July 1943, RAAF retired them from frontline service in September same year. Anyway, point being?

Are you sure about that timeline? I thought they got K and maybe some M earlier than that

I am just saying that P-40E was faster or just as fast as Wildcat in high altitude. You can easily find data where P-40E is faster than 320 mph or even 330 mph at 20 000 ft. It of course depends which version of Wildcat we are comparing to Kittyhawk, F4F-3 was performing better than F4F-4. I can agree that F4F-3 was better in 25 000 ft or higher than P-40E, F4F-4 not so much. I mean just compare data from RAAF Kittyhawk test (A29-129) with data for Wildcats, you will see that Kittyhawk wasn't really performing bad in high altitude, certainly not worse than F4F-4, at least on paper.

Right, Kittyhawk was faster, for sure, than a Wildcat. But top speed doesn't tell the whole story. At 20,000 feet, per this test, a Kittyhawk I was making 655 hp and rate of climb is 880 fpm. At 25,000 ft, it was making 555 hp and the ROC is down to 480 fpm. It's a good indication that the drag was fairly low that it it could still make 300+ mph at 20,000 ft. But it was very sluggish. This is something Shortround6 has brought up a few times. Turns would make them lose altitude more quickly than normal, (and stall). Based on how pilots described it, it's not really capable of combat at 25,000 ft plus, probably not at 20,000 either, or anything over about 15,000 ft.

Unlike what SR6 was saying, I don't think this is applicable at 12-15,000 ft, but it did definitely seem to be the case at 20k or higher.

This is why 49th FG developed specific tactics for attacking IJN air strikes at that altitude. Some press alleged that P-40s were always used this way, per Chennault, but they really usually weren't, they would mix it up but just using energy fighting tactics against the Japanese as much as possible, and dive away when they got in trouble. But over Darwin, fighting at the absolute limit of their performance ceiling, it was literally one pass, split S and dive away, then zoom and climb back up. Because they were just anemic at that altitude.

I don't have the precise HP available to a Wildcat at 20,000 or 25,000 ft but I think it was a bit more.

You don't know, just because nobody knowes. In theory V-1710-39/-73 was also not supposed to withstand much more than 56/60 inHg @ 3000 rpm and yet pilots were pushing these Allisons well beyond that. Again, I am not saying that V-1710-33 was able to withstand let's say 1400 bhp without critical failure and it is logical that it was not as capable in this regard as later Allisons series E/F so I agree with your post. I don't even remember why are we talking about such things to be honest.

Well, it's context for comparison with an "Ozhawk". And it sounds like a two speed supercharged version of a Hawk was actually available. I'd love to see some more specific performance stats on it.

 

[Geoffrey Sinclair]

F4F performance, USN figures,

Model		F4F-3	F4F-4 / FM-1	F4F-7
Date	Date	14-Aug-42	1-Jul-43	15-Aug-42
Loading Condition	Mission	Fighter	Fighter	Photo
Gross Weight	Pounds	7,556	7,975	10,328
Empty Weight	Pounds	5,381	5,895	5,456
Fixed Guns	Number/Type	4 x 0.50 inch	6 x 0.50 inch (F4F) / 4 x 0.50 inch (FM)
Fixed Guns Ammunition	Rounds	1,800	1,440 (F4F) / 1,720 (FM)
Engine Rating Take-Off	BHP /RPM	1,200 / 2,900	1,200 / 2,900	1,200 / 2,900
Engine Rating Normal	BHP/RPM/Feet	1,100 / 2,550 / 0-2,500	1,100 / 2,550 / 0-3,300	1,100 / 2,550 / 0-2,500
Engine Rating Normal	BHP/RPM/Feet	n/a	1,080 / 2,550 / 3,800
Engine Rating Normal	BHP/RPM/Feet	1,050 / 2,550 / 12,000	1,090 / 2,550 / 11,300	1,050 / 2,550 / 12,000
Engine Rating Normal	BHP/RPM/Feet	n/a	1,030 / 2,550 / 13,000
Engine Rating Normal	BHP/RPM/Feet	1,000 / 2,550 / 19,000	1,040 / 2,550 / 18,400	1,000 / 2,550 / 19,000
Engine Rating Military	BHP/RPM/Feet	1,200 / 2,700 / 0-1,800	1,200 / 2,700 / 0-1,800	1,200 / 2,700 / 1,800
Engine Rating Military	BHP/RPM/Feet	n/a	1,135 / 2,700 / 3,400
Engine Rating Military	BHP/RPM/Feet	1,150 / 2,700 / 11,500	1,150 / 2,700 / 11,500	1,150 / 2,700 / 11,500
Engine Rating Military	BHP/RPM/Feet	n/a	1,030 / 2,550-2.700 / 15,000
Engine Rating Military	BHP/RPM/Feet	1,000 / 2,550 / 19,000	1,040 / 2,550 / 18,400	1,000 / 2,550 / 19,000

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Model	Model	F4F-3	F4F-3	F4F-4 / FM-1	F4F-4 / FM-1	F4F-7	F4F-7
Engine Rating	For Performance	Military	Normal	Military	Normal	Military	Normal
VM Sea Level	MPH	290​	280​	284​	274​	282​	273​
VM	MPH/Feet	295/1,800	288/2,500	n/a	n/a	288/1,800	280/2,500
VM	MPH/Feet	294/3,100	287/4,200	n/a	n/a	283/3,100	278/4,200
VM	MPH/Feet	316/11,500	310/12,000	n/a	n/a	307/11,500	299/12,000
VM	MPH/Feet	311/15,100	307/13,300	n/a	n/a	298/15,100	292/13,300
VM	MPH/Feet	323/19,000	323/19,000	n/a	n/a	309/19,000	309/19,000
VM (Critical Altitude)	MPH/Feet	329/21,100	329/21,100	320/18,800	320/18,800	310/19,400	310/19,400
Time to 10,000 feet	Minutes	4.6​	4.9​	n/a	5.6​	6.5​	7.2​
Time to 20,000 feet	Minutes	10.3​	10.6​	n/a	12.4​	16.4​	17.2​
Service Ceiling	Feet	36,400​	36,400​	34,000​	34,000​	26,900​	26,900​

F4F-3 Notes IFF Equipment carried. S.S. Cells not removed for ferry (only rear tank fuel tight without cell, gain in capacity 3 gallons). Reissued from original date
F4F-4/FM-1 Notes Model FM-1 has 4x0.50 inch guns and 1,720 rounds ammunition, with gross weight 75 pounds greater than F4F-1. The performance is based on the F4F-4 weights. Contract changes through "R" and Service Changes through #82 are incorporated. Performance based in flight tests.
F4F-7 Notes IFF Equipment carried. Engine take-off rating is for 5 minutes.

RAF figures,

Grumman Martlet I, fixed wings.
Engine Make	Cyclone G-205A
Horse Power	1,000​
Power At Height (feet)	13,500​
Armament Forward Wings	4x0.50"
Rounds Per Machine Gun	300​
Weight Tare (pounds)	4,967​
Normal Weight (pounds)	6,835​
Service Ceiling (Feet)	32,000​
Maximum Speed (m.p.h)	310​
Max Speed Height (Feet)	14,500​

To the P-40
600 P-40K-1 (LL model) accepted May to September 1942 and 700 P-40K-5 to K-15 accepted August to December 1942
K-1: 336 US, 191 Britain, 73 USSR
K-5 to -15: 215 US, 148 Britain, 241 USSR, 44 Australia, 30 Brazil, 22 New Zealand.

RAAF P-40
1st allocation was 143 P-40E/E-1, 14 lost at sea, numbers made up by "borrowing" 33 P-40 from USAAF
2nd allocation was 163 P-40K, M, N (44 K-10 and -15, 96M-1, -5 and -10 , 23 N-1) 4K and 2 M lost at sea, 4 M arrived damaged beyond repair.
3rd allocation was 202 P-40N
Special allocation was 60 P-40N, following External Affairs Minister H.V. Evatt visit to US (originally 128 but cut to 60)
4th allocation was 261 P-40N, 2 arrived damaged beyond repair.

The 1942 P-40E/E-1 imports ended in September, then 117 P-40 imports January to April 1943, then a 7 week gap to 13 imports in June, 35 in July, another 233 imported August to December 1943.

The 4 P-40M damaged beyond repair en route were offloaded in Wellington New Zealand in March 1943, after a survey of the aircraft the decision was taken to ship them to Australia for salvage, they arrived in August and were scrapped but for some reason 2 of them were first given RAAF serials, the other 2 were not. The ones with RAAF serials are recorded in the orders and imports data, the other two are not. The result is a pair of P-40M with serials in the P-40E/K range (to A29-205), arriving well after the other P-40M whose serials begin A29-300.

One P-40N-1 from the 2nd allocation exchanged for a USAAF P-40N-5
22 P-40N-20 from the 3rd/Evatt allocations exchanged for 22 Dutch order P-40N-20

As of end 1942 the RAAF was trying to maintain 3 P-40 squadrons with 101 P-40E/E-1 given 58 P-40 losses and 3 awaiting write off, as of end June 1943 a total of 292 P-40 had arrived, of which 75 had been lost, 7 were awaiting write off and 14 being erected (including the 13 June arrivals) to maintain 5 P-40 squadrons. When it comes to allocation of the P-40E, K, M and N through 1943 numbers 75, 76, 77 sqns formed in 1942 were the front line units, then in 1943,

78 sqn formed July, not in front line until November
80 sqn formed in September, not in front line until February 1944
82 sqn, formed in June, not in front line until August 1944.
84 sqn, transitioned to P-40 from Boomerang in September/October 1943, based at Horn Island, North Queensland.
86 sqn, formed March 1943, front line July 1943, southern Dutch New Guinea.

The ADF serials page given an idea of dates with squadrons.