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

[GTX]

The reality was that when Lawrie Wackett returned from his tour and decided that the Commonwealth Aircraft Corporation was going to build an American designed trainer, which became the Wirraway, there was not universal approval within the more Britophile facets of the government. For Australia to put a non-British fighter into production before the war is stretching things a little. The Wirraway had to happen before the industry had the confidence to take on something more advanced, but if it were a fighter that the CAC was going to build, the Hurricane stands a better chance than most other types.

The Australian technical mission to Europe and the United States to evaluate modern aircraft types and select a type suitable to Australia's defence needs and within Australia's capabilities to build was extremely critical of British designs/manufacturing techniques IIRC.

 

[nuuumannn]

The Australian technical mission to Europe and the United States to evaluate modern aircraft types and select a type suitable to Australia's defence needs and within Australia's capabilities to build was extremely critical of British designs/manufacturing techniques IIRC.

Yup, I've read the same... In the mid 1930s, the RAAF ordered Hawker Demons, structurally there's not that much difference between them and the Hurricane, except, obviously the centre section and engine, but the techniques in their construction were the same. Even the octagonal main spar lengths with ribs fitted were of the same design between the aircraft. Of all the designs proposed here, the Hurricane would have been the easiest to have mass manufactured because the design had a foot in the biplane structural camp of the time. The Wirraway fuselage design was also steel tube with the rear section fabric covered, mated to an all-metal centre section; the design characteristics were very similar.

 

[GTX]

But arguably the trainer capability of the Wirraway was even more useful than a single seat fighter

 

[Wild_Bill_Kelso]

I would think the easiest to produce would be the Curtiss P-36. I'd like to see how that design would have developed further under CAC's lead into the 1940s. A bubble-canopied Hawk with a dual-stage supercharged R-1830 engine and streamlined undercarriage and low wing surfaces would have been something to see, perhaps appearing from some angles like the Caproni F.5.

View attachment 666659
View attachment 666661

I love that Caproni F5. I always wondered why Curtiss never replaced that weird Boeing landing gear on the various later models of P-40. Seems like an easy way to reduce a bunch of drag and probably some weight. The various changes you propose for the P-36 would be ... ambitious! But who knows, Aussies are creative and resourceful. I bet they could have done something with it. The question really is how quickly. From what I gather, they had at least one legit German engineer working on the Boomerang, Fred David. Maybe if they had trusted the guy a little more quickly (he was a Jew after all so probably didn't love Hitler) maybe he could have done some more creative work for them.

If nothing else, this thread is a fun way to look at some of those promising 'might have been' early WW2 fighters that (at least in some of these cases) probably had some real merit but never really got a chance to show their true design potential.

By the way, IMO a P-36 with two HMG in the nose plus armor and SS tanks is probably going to work fairly well against Japanese bombers. I mean if Ki-43s could shoot down American & British planes with typically less than that...

 

[Wild_Bill_Kelso]

I think the problem here is that you refuse to see anything that contradicts your point of view, Bill. In fact, this twisting of my statement is an example of that. I was specifically referring to the P-40E versus the Hurricane IIc, which, if you'd read it properly, you'd know. So, let's look at what's on offer, shall we?

Peter Bowers in Curtiss Aircraft 1907-1947 (Putnam, 1987) offers a maximum speed for the P-40E (based on Curtiss supplied figures) at 334 mph at 15,000 ft.

Yeah but he's wrong. I can find some book somewhere that says just about anything.

Here is the USAAC Dec 1 1941 - P-40E at 7,952 lbs, 361.7 mph at 15,000 feet, 3000 RPM "wide open throttle"

Australian test, Sept 1942 (8626 lbs + with belly tank sway braces) P-40E at "military power" (44" HG) 348 mph at 3,000 RPM 12,300 ft

Even this Bosombe down test (June 1943) of a Kittyhawk Ia (P-40E) at "takeoff power" (42" HG) at 8,220 lbs, it made 344 mph at 13,800 ft.

The other tests at Boscome Down were done at takeoff power (42" Hg) or lower and / or low RPM and I don't think the Hurricane of any mark was making 340 mph at military or takeoff power.

But according to the manual, and the Specific Engine chart for the P-40E, the maximum (War emergency) power was 56" Hg (producing 1470 hp) and even military power was 44" Hg. At that power the P-40E was topping out considerably over 350 mph.

Now you can say that you prefer one set of figures, and I prefer another, but the tests you are quoting for the higher speeds for the Hurricanes are at higher boost pressures. For example, this Sept 1941 test a Hurricane Mk II managed to struggle to 330 mph at 18,900 ft, but only by using 50.2" Hg.

In this test, a Hurricane II just barely managed to get over 340 mph but using +16 lb boost and only at Sea level. At altitude it was below 330 mph,.

According to this summary, while a IIA was able to reach 342 mph at +16 lb boost (and presumably the good fuel), the type the IIC was only making 327 mph even with +12 lb boost and the IIC "Trop" which was the one actually in combat, couldn't make more than 301 mph. That is what they were actually doing in the field.

By the way, using the same (Merlin XX) engine, according to this Sept 1942 British Air Commission test, the Kittyhawk II managed 370 mph at 20400 ft.

But the reason I draw the conclusions I have (just like many other people), is because of the operational histories and pilot testimonies. RAF, RAAF, USAAF etc. concluded that the Hurricane was much slower, and in fact too slow for use as a fighter in the Middle East, which was why it was replaced in multiple squadrons by the P-40 in 1941 and 1942. The Hurricane IIB and IIC still active in the Theater were relegated to use as fighter-bombers by the RAF. There were also many field tests. For example This (around here) pretty famous contest between an RAAF P-40E and a Spitfire VC found that the P-40 was considerably faster below 16,000 ft. The specific quote is 15mph to 25 mph faster depending on the altitude I don't believe I have ever heard any pilot claim that any mark of Hurricane was faster than any mark of Spitfire, nor for that matter am I aware of any pilot describing the Hurricane.

The slower speed of the Spitfire in this case was due to the Vokes filter, specific type of engine and relatively low (IIRC +9) boost being used, but I guarantee it was still faster than a Hurricane and so was the P-40E

Frank Mason in Hawker Aircraft since 1920 (Putnam, 1991) offers a maximum speed for the Hurricane IIc as 336 mph without a corresponding altitude, but Owen Thetford in Royal Air Force Aircraft since 1918 (Putnam, 1987) offers the Hurricane IIc's maximum speed as 339 mph @22,000 ft, which is a significantly higher altitude at which it achieves its maximum as well, and given that the Hurricane IIc was lighter than the P-40E, you can guarantee it's gonna get to altitude faster (you can find this data by looking instead of presuming). Thetford doesn't offer speed for the Kittyhawk I or Ia, which was equivalent to the P-40E.

Now, let's look at easier accessible source material, like Wikipedia, which tells us that the P-40E's maximum speed is 334 mph at 15,000 ft (the same as above since the source is the same) and for the Hurricane IIc is 340 mph @ 21,000 ft, from Jane's Fighting Aircraft of World War Two.

Curtiss P-40 Warhawk - Wikipedia

en.wikipedia.org

Hawker Hurricane - Wikipedia

en.wikipedia.org

So, get your facts right.

Carry on now...

I have my facts strait. Wikipedia is usually wrong mate.

 

[Wild_Bill_Kelso]

Basically Australia, had they taken the P-36 route, would have been stuck making some sort of P-36 clone.
If they started earlier than the Boomerang they might have gotten them into service about the same time.
The airframe was more complex than the Boomerang airframe. How much stuff/parts were borrowed from the Wirraway I don't know or if it was just basic construction. But the people in Australia thought the Boomerang was going to be their best bet to get something into production.
Now maybe if they had started 6 months to year earlier they might have been able to get the P-36 into production.
Problem is that some people don't want to settle for a P-36. Or a P-36 with different guns or with a different bombload or a bit better protection.
They want to use the R-1830 engine, which was a logical choice, but then use a non standard installation that the P-36 only used in prototype form. And they want to use a number of other "improvements" to get a significantly better P-36. Which is going to add development time. Which Australia doesn't have.
My point is that even with the P-36 airframe and using the standard R-1830 engines we know what most of the changes are going to be. We know what Changing the guns to Tomahawk standard is going to cost or changing to four .50 cal guns or several other combinations. We know what improved fuel tank protection is going to cost. We know what protection on the P-40 level is going to cost and so on down the line. Cost meaning weight so we can estimate the weight of changes pretty darn well.
If somebody wants to propose turbo charged P-36s with six .50s flying over Darwin we can actually estimate the weight pretty well. It is going to be very close to the weight of the P-40 with some allowance for the different engines. It is the thinking that if they start with a P-36 they will get a lighter, more maneuverable airplane or have some other advantage that bothers me.
Radial engine installations did get better over time. But they didn't get better in the time Australia needs.
P&W did make a much better installation than the one used in the F4F but they didn't get it done until the end of 1942 or early 1943 and fully sorted out. Which is a bit late for Australia, it was even late for the US. An R-1830 powered P-40 that could do 370mph at over 20,000ft might have been very interesting but it wasn't going to show up until late 1943. At which point what are you going to do with it?

For Australia any " improvement" to the P-36 like changes to landing gear or changing to a bubble canopy or trying to engineer a better engine installation is going to delay the project.

I also wonder about the worth of some of the improvements. The P-40 landing gear was not ideal but was it really that bad? It certainly looks clunky but a Tomahawk with a 1040hp engine was only a few mph off the speed of a Spitfire MK II. at 15,000ft. The Spit went faster higher up but the Merlin gave more power higher up. I am just trying to figure out the drag. Playing with the landing gear on a P-36/P-40 when the P-40 wing/landing/fuselage is already as good or slightly better than a Spitfire seems to be pretty far down on the list.
Much like everybody "knew" that if they put full wheel covers on the Spitfire it would go faster but there was always something else that needed doing first.

I think you are making one big mistake here though in your summary. You are assuming that everybody wants the super radical upgraded P-36 right out the gate, at the same time an early Boomerang might be available.

What seems more plausible to me, is they start with a garden variety Battle of France style P-36. If the British were still using these in combat in Burma in 1944 it's a cinch they are going to be useful in early 1942. So start there - this is the Ozhawk Mk I. Its used as an interceptor, to protect the more remote bases, and as an advanced trainer. Then as production continues, improved features are added. If a slightly more powerful R-1830 is available in mid 1942, then you can do protected fuel tanks, maybe a couple extra guns or heavier guns. The plane becomes more useful - Ozhawk Mk II. You get a two speed 1830? Better still - Ozhawk MK III. If you have a P-36 still making around the same horsepower, but it can do it at 20,000 ft, and still fighting more or less like a Mohawk did for the British, now you have something fairly useful to add to the mix, especially considering the shortage of combat aircraft in the front line.

By the way, if you can produce as much power as a Tomahawk / P-40B/C, it should still be plenty maneuverable because a Tomahawk certainly was. It wouldn't be quite as fast with a radial engine but it could still roll and dive like a P-40 or a Hawk.

I think at this point our Ozhawk Mk III is at least as useful as a Boomerang.

And then if a two stage 1830 which can fit in a P-36 is avalable in late 1942 or 1943, maybe they try to make a new Ozhawk MK IV that may or may not be a little faster than a Mk down low , but it can perform at 25,000 ft. and for sure it's going to go faster up that high. Now the Aussies have a bird they can fight Zeros and Oscars with.

By now it's 1944 and you make an Ozhawk Mk V with the improvements we know to do with streamlining, exhaust, different landing gear etc. maybe then you are thinking about the plane you were talking about above, or maybe they look at the numbers and just buy some Spitfire Mk VIII or Corsairs.

 

[Wild_Bill_Kelso]

A lot depends on when certain decision were made.
And like a number of other aircraft, changes were made during the process.
The Beaufighter for example was supposed to be a minimum change to a lot of things from Beaufort. A lot was kept but not as much as they originally thought?
At certain points in time, which may have changed a just a few months later?, the R-1830 looked like the best bet for getting a 1100-1200hp engine into production in Australia the quickest. Once you start working on that what project happens 3-4 months later when somebody askes about building Merlins? Is somebody going to give you enough "stuff" to get Merlin production going sooner that the R-1830 production or will it just delay things by 3-4 months or do you have to rip out some of what you already have done and start over?

Australia was tiring to build all kinds of stuff and the aircraft programs did not exist in a vacuum. Australia had a rifle factory but no source for light (or heavy) machine guns.
They came up with the Charlton LMG
View attachment 667031
Not a great solution but beats the heck out of nothing.

I believe the Chalrton was actually a New Zealand design. I wonder how many Ozhawks (Kiwihawks?) they could make in Christchurch?

 

[ThomasP]

Hey Wild_Bill_Kelso,

re "In this test, a Hurricane II just barely managed to get over 340 mph but using +16 lb boost and only at Sea level. At altitude it was below 330 mph,"

This does not contradict the gist of what you have been saying, but I thought I should point that you are misreading the Hurricane IIC chart in the test you linked to. The line starting at ~340 mph at SL is actually the line showing the climb rate.

The Vmax at +16 lb boost in Low gear is about 307 mph at ~10,000 ft. The Vmax of 327 mph at 20,500 ft in High gear is at +9 lb boost.

 

[Wild_Bill_Kelso]

Hey Wild_Bill_Kelso,

re "In this test, a Hurricane II just barely managed to get over 340 mph but using +16 lb boost and only at Sea level. At altitude it was below 330 mph,"

This does not contradict the gist of what you have been saying, but I thought I should point that you are misreading the Hurricane IIC chart in the test you linked to. The line starting at ~340 mph at SL is actually the line showing the climb rate.

The Vmax at +16 lb boost in Low gear is about 307 mph at ~10,000 ft. The Vmax of 327 mph at 20,500 ft in High gear is at +9 lb boost.

Ah, thanks my bad

 

[Wild_Bill_Kelso]

I should have realized that was way too fast. Actually even 307 mph at Sea Level is pretty good.

 

[Geoffrey Sinclair]

The Hawker Hurricane by Francis K Mason,
IIA absolute ceiling 36,300 feet, time to 15,000 feet 6.2 minutes, top speed 342 mph at 17,500 feet
IIB absolute ceiling 36,000 feet, time to 15,000 feet 5.5 minutes, top speed 330 mph at 17,800 feet.
IIC absolute ceiling 35,600 feet, time to 15,000 feet 5.7 minutes, top speed 329 mph at 17,500 feet.

Somehow the IIA climb figure looks wrong.

AVIA 46/114 Hawker Hurricane biography for the official history, performance figures
IIA, all up weight 6,900 pounds, take off run to clear 50 feet 400 yards, ceiling 36,800 feet, time to 15,000 feet 5.7 minutes, top speed 336 mph at 21,000 feet.
IIB, all up weight 7,200 pounds, take off run to clear 50 feet 420 yards, ceiling 36,600 feet, time to 15,000 feet 6.0 minutes, top speed 335 mph at 21,000 feet.
IIC, all up weight 7,450 pounds, take off run to clear 50 feet 460 yards, ceiling 36,000 feet, time to 15,000 feet 6.3 minutes, top speed 332 mph at 21,000 feet.

Performance Tables of British Service Aircraft, Air Publication 1746,
IIA Weight 7,014 pounds, take off run to clear 50 feet 420 yards, service ceiling 36,600 feet, time to 15,000 feet 5.9 minutes, top speed 335 mph at 21,000 feet.
IIA Weight 7,544 pounds, take off run to clear 50 feet 450 yards, service ceiling 35,800 feet, time to 15,000 feet 6.4 minutes, top speed 332 mph at 21,000 feet.

Tomahawk Weight 7,224 pounds, take off run to clear 50 feet 570 yards, service ceiling 31,000 feet, time to 15,000 feet 7 minutes, top speed 345 mph at 16,000 feet.

Dean, America's Hundred Thousand, Military Power, P-40 6,800 pounds 365 mph at 15,000 feet, P-40E 8,400 pounds 360 mp at 15,000 feet, P-40N 8,400 pounds 345 mph at 15,000 feet.

The American Fighter, Angelucci and Bowers,
P-40 357 mph at 15,000 feet,
P-40B 352 mph at 15,000 feet,
P-40C 345 mph at 15,000 feet,
P-40D 350 mph at 15,000 feet,
P-40E 366 mph at 15,000 feet,
P-40K 370 mph at 20,000 feet,
P-40M 360 mph at 20,000 feet,
P-40N 343 mph at 15,000 feet,

Australian official history,

Aircraft	Range	max speed mph/feet	serv. Ceil. Ft.	Guns	Remarks
TOMAHAWK
P-40, P-40B & P-40C	890​	340 at 15,000	30,000​	2 x .50-in & 4 x .30-in	P-40C had self-sealing petrol tanks
KITTYHAWK
I & Ia (P-40D & P-40E)	800​	350 at 15,000	30,600​	4 x .50-in (I) or 6 x .50-in (Ia)	Also fighter-bomber (max . 620 lb).
I & Ia (P-40D & P-40E)	470​	n/a	n/a	n/a	Range with 500-lb bomb
Mks II & III	1,190​	346 at 5,000	30,000​	4 or 6 x .50-in	Also fighter-bombers. P-40 F & L (II) and M & N (III) Mk II max. load 600 lb ; Mk III max. load 1,000 lb .
Mk IV	1,210​	352 at 11,000	32,500​	6 x .50-in	Also fighter-bomber (max. load 1,000 lb). P-40M
WARHAWK
P-40N	1,550​	343 at 15,000	38,200​	6 x .5-in	American original of Kittyhawk III Also fighter-bomber (max . 1,500 lb)
TOMAHAWK
P-40B & P-40C	890​	345 at 16,000	31,000​	4 x .30-in or 2 x .50-in & 2 x .30-in or 2 x .50-in & 2 x .303-in	P-40C had self-sealing petrol tank

Australian Archives A2671 397, performance of P-40E-1 A29-129 ex 41-36079, approximate stop speeds, climb and time to height sea level 280 mph, 1,850 feet/minute

5,000 feet 300 mph, 1,850 feet/minute, 2,7 minutes
10,000 feet 320 mph, 1,850 feet/minute, 5.4 minutes
15,000 feet 315 mph, 1,400 feet/minute, 8.7 minutes
20,000 feet 310 mph, 1,000 feet/minute, 13.0 minutes
25,000 feet 295 mph, 550 feet/minute, 19.0 minutes
30,000 feet 275 mph, 150 feet/minute, 35.0 minutes
Service Ceiling 30,500 feet.

Australian Archives MP287/1 1552/1 Turbo Boomerang, report of 16 April 1943, rated altitude 28,000 feet, climb performance severely restricted by available propellers, recommendation is a 4 blade 11 foot 50 spline propellers, similar to P-51B. Performance at full combat trim with guns and camouflage, turbo Boomerang / standard Boomerang, top speeds

Sea level 269 / 275 mph
15,000 feet 311 / 305
28,200 feet 348 / 276
rate of climb
2,150 / 2,450
1,640 / 1,760
1,180 / 380

CA14A (Turbo) Boomerang performance based on 1,300 HP level speed and 1,150 HP rated climb.

Predicted performance with turbo R-2000 and 4 bladed propeller, top speeds 286 mph sea level, 372 at 27,000 feet, rate of climb sea level 2,100, at 30,000 feet 1,770.

In setting up Australian aircraft production in the mid 1930's the brief was for modern aircraft, things like stressed skin, enclosed cockpit, retractable undercarriage, variable pitch propeller, no suitable British design was proven at the time. The Australian Archives have copies of letters from the time stating the failure to buy British means the letter writer was never going to vote for the government again. In 1943 the decision was the P-51D. The Boomerang was the one design that could stay all local, no need to reply on overseas supply, something that was nowhere near guaranteed in 1942, and be around in 1942. If the decision was to build a fighter in Australia in 1939 it would have been the Spitfire, proven enough and state of art, same in 1940, at least until mid year, from then and in 1941 quite possibly the P-51 given the CAC North American links and the performance reports, since the chances of obtaining much support from Britain was low. As of 1939/1940 the which is better radial or inline debate was in favour of inlines for fighters, it would take the Fw190 for the RAF and therefore the RAAF to change its mind.

The time between the decision to go and the first deliveries would be around 2 years based on the times taken for the Wirraway, Beaufort and Mustang, longer if Australia builds the initial batch of engines.

 

[FLYBOYJ]

I always wondered why Curtiss never replaced that weird Boeing landing gear on the various later models of P-40. Seems like an easy way to reduce a bunch of drag and probably some weight.

Both the P-36 and P-40 had a similar system. To say a different configuration is saving weight is a guess and what are you comparing it to?

 

[Shortround6]

Both the P-36 and P-40 had a similar system. To say it's saving weight is a guess and what are you comparing it to?

Boeing was still using pretty much the same system on the XF8B in 1945. It may have been the same system that was used on the Skyraider.

What some people don't seem to realize on the P-36/P-40 was, that the front of the landing gear was attached to the forward spar and the landing gear leg went under the 2nd spar, not through it.

If you start cutting holes in the spars you have to redo all the stress calculations on the wing and probably beef up a few of the local areas.

Now if you want to hinge the lading gear so it folds inward like a P-51 you may have to take out the forward fuel tank so the wheels have somewhere to go.
Now since the wheel wells are empty you can stick fuel tanks on the wing roots but since that is in back of the center of gravity you have to...............................

It can be done. Is what you are going to gain worth the trouble.

Also take a look at the wheel covers on the P-36 and the lack of wheel covers on the P-40. They had a pretty good idea of what the wheel covers or lack of wheel covers was costing them in drag.

I keep trying to point it out that the early P-40 was very close in speed to the early Spitfires at just under 15,000ft and using very similar power. The Tomahawks were faster than the 109Es while being larger and heavier.
You can do better than the P-40 but it wasn't the brick aerodynamically that some people think it was.

Curtiss also managed to totally screw up the XP-46

It had the more streamlined landing gear, it had a smaller wing, it had a smaller fuselage, it didn't have the chin radiator.
It was slower than a P-40E using the same engine.

 

[FLYBOYJ]

My A&P school had a hydraulic training rig and the MLG portion of the trainer was this type of system. Since all the data plates were removed, we were never certain what type of aircraft it was from but it was rumored it was from a P-40. From what I remember I seen no recognizable weight difference in this type of landing gear when compared to other contemporaries.

Found this earlier today.

 

[Wild_Bill_Kelso]

The Hawker Hurricane by Francis K Mason,
IIA absolute ceiling 36,300 feet, time to 15,000 feet 6.2 minutes, top speed 342 mph at 17,500 feet
IIB absolute ceiling 36,000 feet, time to 15,000 feet 5.5 minutes, top speed 330 mph at 17,800 feet.
IIC absolute ceiling 35,600 feet, time to 15,000 feet 5.7 minutes, top speed 329 mph at 17,500 feet.

Somehow the IIA climb figure looks wrong.

AVIA 46/114 Hawker Hurricane biography for the official history, performance figures
IIA, all up weight 6,900 pounds, take off run to clear 50 feet 400 yards, ceiling 36,800 feet, time to 15,000 feet 5.7 minutes, top speed 336 mph at 21,000 feet.
IIB, all up weight 7,200 pounds, take off run to clear 50 feet 420 yards, ceiling 36,600 feet, time to 15,000 feet 6.0 minutes, top speed 335 mph at 21,000 feet.
IIC, all up weight 7,450 pounds, take off run to clear 50 feet 460 yards, ceiling 36,000 feet, time to 15,000 feet 6.3 minutes, top speed 332 mph at 21,000 feet.

Performance Tables of British Service Aircraft, Air Publication 1746,
IIA Weight 7,014 pounds, take off run to clear 50 feet 420 yards, service ceiling 36,600 feet, time to 15,000 feet 5.9 minutes, top speed 335 mph at 21,000 feet.
IIA Weight 7,544 pounds, take off run to clear 50 feet 450 yards, service ceiling 35,800 feet, time to 15,000 feet 6.4 minutes, top speed 332 mph at 21,000 feet.

Tomahawk Weight 7,224 pounds, take off run to clear 50 feet 570 yards, service ceiling 31,000 feet, time to 15,000 feet 7 minutes, top speed 345 mph at 16,000 feet.

Dean, America's Hundred Thousand, Military Power, P-40 6,800 pounds 365 mph at 15,000 feet, P-40E 8,400 pounds 360 mp at 15,000 feet, P-40N 8,400 pounds 345 mph at 15,000 feet.

The American Fighter, Angelucci and Bowers,
P-40 357 mph at 15,000 feet,
P-40B 352 mph at 15,000 feet,
P-40C 345 mph at 15,000 feet,
P-40D 350 mph at 15,000 feet,
P-40E 366 mph at 15,000 feet,
P-40K 370 mph at 20,000 feet,
P-40M 360 mph at 20,000 feet,
P-40N 343 mph at 15,000 feet,

Australian official history,

Aircraft	Range	max speed mph/feet	serv. Ceil. Ft.	Guns	Remarks
TOMAHAWK
P-40, P-40B & P-40C	890​	340 at 15,000	30,000​	2 x .50-in & 4 x .30-in	P-40C had self-sealing petrol tanks
KITTYHAWK
I & Ia (P-40D & P-40E)	800​	350 at 15,000	30,600​	4 x .50-in (I) or 6 x .50-in (Ia)	Also fighter-bomber (max . 620 lb).
I & Ia (P-40D & P-40E)	470​	n/a	n/a	n/a	Range with 500-lb bomb
Mks II & III	1,190​	346 at 5,000	30,000​	4 or 6 x .50-in	Also fighter-bombers. P-40 F & L (II) and M & N (III) Mk II max. load 600 lb ; Mk III max. load 1,000 lb .
Mk IV	1,210​	352 at 11,000	32,500​	6 x .50-in	Also fighter-bomber (max. load 1,000 lb). P-40M
WARHAWK
P-40N	1,550​	343 at 15,000	38,200​	6 x .5-in	American original of Kittyhawk III Also fighter-bomber (max . 1,500 lb)
TOMAHAWK
P-40B & P-40C	890​	345 at 16,000	31,000​	4 x .30-in or 2 x .50-in & 2 x .30-in or 2 x .50-in & 2 x .303-in	P-40C had self-sealing petrol tank

Australian Archives A2671 397, performance of P-40E-1 A29-129 ex 41-36079, approximate stop speeds, climb and time to height sea level 280 mph, 1,850 feet/minute

You seem to have Toamahwk in there twice with slightly different numbers. As others have already noted elsewhere in the thread, P-40 performance numbers are all over the place, often low-balled due to testing at low power, high weight and strange altitude bands. For sure the Mk II and III numbers are wrong - they used different engines and hit their top speed at different altitudes. The Mk II (P-40F/L) made between 365 and 374 mph in various tests. The Mk III which could be a low altitude P-40K or a medium altitude P-40M had various speeds but always above 350 mph.

The Mk IV (P-40N) also came in very different configurations, but in the light / interceptor version (4 guns) it made ~380 mph.

For all the P-40s (as with most fighters, probably) the top speed, climb rate, and range are all different depending on the precise configuration and the boost settings used. Many tests for whatever reason were done at high weights and low boost settings, maybe to figure out a 'worst case scenario'. For example this

5,000 feet 300 mph, 1,850 feet/minute, 2,7 minutes
10,000 feet 320 mph, 1,850 feet/minute, 5.4 minutes
15,000 feet 315 mph, 1,400 feet/minute, 8.7 minutes
20,000 feet 310 mph, 1,000 feet/minute, 13.0 minutes
25,000 feet 295 mph, 550 feet/minute, 19.0 minutes
30,000 feet 275 mph, 150 feet/minute, 35.0 minutes
Service Ceiling 30,500 feet.

...is for sure reflecting a 'heavy' laden aircraft flown at low boost, probably continuous rated power, maybe with a belly tank?. The other very thorough Australian test I posted a couple of posts back shows far better performance, starting at 300 mph at Sea level and going up to 348 mph at 12,300. And this is a heavily laden plane at (8600 lbs) and flying at only military power (44" Hg). It also started climbing with 2000 fpm which rate continued until 9,500 ft. (this was at only 39" Hg power setting). The fact that the ROC remained the same up to that height is a good indicator more power was available.

This aircraft was configured for long range with 123 gallons (891 lbs) of internal fuel, six guns with full ammo, sway braces, and another 50 lbs of extra "desert equipment" and tools. The whole test was to evaluate an external fuel tank (not, I think, the normal one) so they were not trying for combat speeds. But it is a very detailed test.

http://www.wwiiaircraftperformance.org/P-40/P-40E_A29-129.pdf

All those quotes for high speed (~330 mph etc.) as I showed upthread for the Hurricane are at +12 lb or +16 lb boost. I believe +12 lbs boost is roughly 54" Hg, and +16 is about 63" Hg. So on a P-40 +12 lbs would be War Emergency Power or Rating, while 63' would be overboost. So I think when we compare the two aircraft we should compare like with like. I don't know what's going on Wikipedia but it's fairly typical for various agendas to be pursued.

This also highlights another major difference between the P-40 and the Hurricane. Because the P-40 (depending on exact configuration) had between 50% -100% better range than the Hurricane, and thus more likely to be assigned to fly escort missions or fighter sweeps, by the time it was engaged in combat they were usually lighter. P-40 was operated (at takeoff) pretty close to the tipping point in terms of weight. About 300-400 lbs less (such as after takeoff, climbing to altitude and flying out to a target) would mean significantly increased performance in terms of rate of climb, acceleration and top speed.

 

[Wild_Bill_Kelso]

My A&P school had a hydraulic training rig and the MLG portion of the trainer was this type of system. Since all the data plates were removed, we were never certain what type of aircraft it was from but it was rumored it was from a P-40. From what I remember I seen no recognizable weight difference in this type of landing gear when compared to other contemporaries.

Found this earlier today.

Well that is interesting, it seemed to me the rotating mechanism would take up extra weight though I admit that was a guess, but for sure the protrusion on the front of the wing and the open / uncovered wheel well added significant drag, probably worth 5-10 mph based on other tests I've seen.

 

[Wild_Bill_Kelso]

One of the biggest problems for the Hurricane was that Vokes filter I think. The 'Trop' version seems to max out at about 300 mph. They had better luck with the filter for the P-40 partly because the intake was on top of the engine.

 

[FLYBOYJ]

Well that is interesting, it seemed to me the rotating mechanism would take up extra weight though I admit that was a guess, but for sure the protrusion on the front of the wing and the open / uncovered wheel well added significant drag, probably worth 5-10 mph based on other tests I've seen.

Having worked around many different landing gears I'd say no more weight than a larger retract piston and hinges within the wheel well, let alone larger hydraulic hoses or lines. I think this system was simple and compact. If anything I think it would weigh less.

Now as far as the fairings around the MLG - that's debatable as well. I worked on L29s and there were wing pylons for fuel tanks. When we removed those we only picked up about 10 mph IIRC and they were obviously a lot more "draggier" than the fairings on the P-40.

 

[Wild_Bill_Kelso]

View attachment 667168
Boeing was still using pretty much the same system on the XF8B in 1945. It may have been the same system that was used on the Skyraider.

What some people don't seem to realize on the P-36/P-40 was, that the front of the landing gear was attached to the forward spar and the landing gear leg went under the 2nd spar, not through it.
View attachment 667169
If you start cutting holes in the spars you have to redo all the stress calculations on the wing and probably beef up a few of the local areas.

Now if you want to hinge the lading gear so it folds inward like a P-51 you may have to take out the forward fuel tank so the wheels have somewhere to go.
Now since the wheel wells are empty you can stick fuel tanks on the wing roots but since that is in back of the center of gravity you have to...............................

It can be done. Is what you are going to gain worth the trouble.

Also take a look at the wheel covers on the P-36 and the lack of wheel covers on the P-40. They had a pretty good idea of what the wheel covers or lack of wheel covers was costing them in drag.

I keep trying to point it out that the early P-40 was very close in speed to the early Spitfires at just under 15,000ft and using very similar power. The Tomahawks were faster than the 109Es while being larger and heavier.
You can do better than the P-40 but it wasn't the brick aerodynamically that some people think it was.

Curtiss also managed to totally screw up the XP-46
View attachment 667170
It had the more streamlined landing gear, it had a smaller wing, it had a smaller fuselage, it didn't have the chin radiator.
It was slower than a P-40E using the same engine.

Just because Curtiss screwed up the P-46 design doesn't mean the Aussies would have made the same mistakes. They had a few good engineers of their own and also that German guy. To me the above just proves that the more conventional landing gear (with fully covered wheels) was certainly possible.

And I'm not saying the P-40 was a flying brick either, by any means, but it certainly could be improved. In terms of drag, there is a lot of difference between these two P-40s

Getting back to the "Ozhawk" - while I agree it wouldn't be as fast as a Tomahawk or a Kittyhawk, I think the potential of a two speed or a two stage engine R-1830 could bring some very welcome capability to the Allied forces in the Pacific in particular, assuming (and this is of course, a big if) they could get it working soon enough. When did they have them in Beauforts exactly? This would probably be useful for Burma too given the need to fly over the Himalayas. P-40 ended up working out well but with the exception of the Merlin-engined F and L, (which were always in short supply), the was basically limited as a capable fighter to somewhere between 12-18000 ft. And that was a major and unwelcome limitation that irritated USAAF commanders (and is basically the reason for the bad postwar reputation of the P-40).

An Ozhawk with a two speed supercharger might be a little slow, but if it's still producing say 1,100 hp at 20,000 ft, before 1943, that could fit into a niche that the Allies did not have very well covered except by the P-38 and Corsair which were in small numbers and still dealing with teething problems. A Ozhawk with a two stage R-1830 could of course be even better.

Conversely, with the availability of higher octane fuel, an "Ozhawk' with a low altitude but extra 'peppy' 1350 hp R-1830-65 like the FM-2 could make for a very nice interceptor and low altitude fighter I think.

 

[Wild_Bill_Kelso]

Having worked around many different landing gears I'd say no more weight than a larger retract piston and hinges within the wheel well, let alone larger hydraulic hoses or lines. I think this system was simple and compact. If anything I think it would weigh less.

Now as far as the fairings around the MLG - that's debatable as well. I worked on L29s and there were wing pylons for fuel tanks. When we removed those we only picked up about 10 mph IIRC and they were obviously a lot more "draggier" than the fairings on the P-40.

View attachment 667202

I think they have some actual studies or estimates on the open wheel well issue, for the Spitfire and a couple other planes (Wildcat?) I'm not sure where to find those though.

Drag is hard to calculate but small things (radio masts for example) seem to sometimes make a big difference.