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

FLYBOYJ said:

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?

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Actually the P-36 and P-40 had exactly the same system and the vast majority of parts on the early P-40s up to and including the E model are identical. The N-5 and later had different wheels and axles to reduce weight and the attachments to the wing changed but I cannot remember at what model. The outer oleo tube also changed, twice from memory.

MiTasol said:

Actually the P-36 and P-40 had exactly the same system and the vast majority of parts on the early P-40s up to and including the E model are identical. The N-5 and later had different wheels and axles to reduce weight and the attachments to the wing changed but I cannot remember at what model. The outer oleo tube also changed, twice from memory.

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?? I didn't understand that question. I was referring to a more conventional type of landing gear like what you had on a P-51 (or most mid- to late-war fighters) maybe a simpler and / or lighter mechanism and fully closing wheel doors. I know not all 'convential' landing gear had fully covered wheel wells of course. I believe the (Boeing designed) one on the Hawk and P-40 was draggier than 'conventional' landing gear.

Wild_Bill_Kelso said:

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.

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I was under the impression that landing gear came from Don Berlin who designed the P-40 - why do you say it was a Boeing design?

I very much doubt it would reduce weight. You will shave a few grams/ounces off by removing the rotating mechanism but not a large amount of weight. You are going to add a bucket load of weight to the wing structure in order to put back the structural rigidity of having the skins and spars in the high stress areas run full distance without the larger holes the fully enclosed landing gear takes, even after you remove the P-36/40 landing gear fairings.
If you mount the gear forward of the front spar like on a P-51 you will need to move the engine forward and that is not practical for CG and other reasons. If you go behind the spar you lose the forward fuel tanks so would need to somehow fit tanks outboard of the gear and inboard of the guns and they would be smaller. Or you could fit tanks where the wheels fit on the P-36/40 but they would also be small and be aft of the CG. You could fit them both locations but then the pilot has 6 fuel tanks to manage - 2 forward, two wheelwell, normal rear and fuselage - and that is increasing the pilot workload and introducing system complexity as well as the weight of all the small tanks and plumbing.

MiTasol said:

I was under the impression that landing gear came from Don Berlin who designed the P-40 - why do you say it was a Boeing design?

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I don't remember all the details, but Shortround6 mentions it in this thread P36/P40 landing gear, top speed and weight penalty

MiTasol said:

I very much doubt it would reduce weight. You will shave a few grams/ounces off by removing the rotating mechanism but not a large amount of weight. You are going to add a bucket load of weight to the wing structure in order to put back the structural rigidity of having the skins and spars in the high stress areas run full distance without the larger holes the fully enclosed landing gear takes, even after you remove the P-36/40 landing gear fairings.
If you mount the gear forward of the front spar like on a P-51 you will need to move the engine forward and that is not practical for CG and other reasons. If you go behind the spar you lose the forward fuel tanks so would need to somehow fit tanks outboard of the gear and inboard of the guns and they would be smaller. Or you could fit tanks where the wheels fit on the P-36/40 but they would also be small and be aft of the CG. You could fit them both locations but then the pilot has 6 fuel tanks to manage - 2 forward, two wheelwell, normal rear and fuselage - and that is increasing the pilot workload and introducing system complexity as well as the weight of all the small tanks and plumbing.

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Yeah you have some good points there, P-51 was probably a bad example because of where the wheel goes. How about... (looking at some models behind me) landing gear like on the Macchi 202? Or the Dewoitine D.520? or the P-47? I'm sure there would be some challenges involved, but I'm also sure there was a way to do it (I mean, I know there was since they did it on the P-46). I dont' see why fully covered gear door would require a much larger hole ?

Wild_Bill_Kelso said:

Well your performance stats certainly would be misleading to say the least comparing a Tomahaw with a P-40D, when in fact it was a P-40F.

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Man, a lot wasted ink because I could not find quickly a picture of a long nose P-40 and P-40D.
I used a picture of a long nose a P-40 and P-40F and noted most of the major differences between the P-40D and the P-40F in the picture.

Apparently not good enough.

The stats are for a P-40B and for P-40D

If you can't get past the picture too bad.

Wild_Bill_Kelso said:

I don't remember all the details, but Shortround6 mentions it in this thread P36/P40 landing gear, top speed and weight penalty



Yeah you have some good points there, P-51 was probably a bad example because of where the wheel goes. How about... (looking at some models behind me) landing gear like on the Macchi 202? Or the Dewoitine D.520? or the P-47? I'm sure there would be some challenges involved, but I'm also sure there was a way to do it (I mean, I know there was since they did it on the P-46). I dont' see why fully covered gear door would require a much larger hole ?

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The Douglas Skyraider had a reward retracting landing gear as well. As mentioned earlier, designers and aerodynamicists had to come together to look at aerodynamic efficiency vs. a practicable internal system. Sometimes a fairing or bulge in the slipstream will not affect the desired performance result.


Photo from wiki

Shortround6 said:

Man, a lot wasted ink because I could not find quickly a picture of a long nose P-40 and P-40D.
I used a picture of a long nose a P-40 and P-40F and noted most of the major differences between the P-40D and the P-40F in the picture.

Apparently not good enough.

The stats are for a P-40B and for P-40D

If you can't get past the picture too bad.

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I posted a C vs. an F, noting there was a significant difference between the two types. You posted all kinds of stats for a B vs. a D, I would say misleadingly claiming that there was no difference in drag between them based on the speeds. To me that is misleading.

Yes they got about the same speed in your example, but the D is ~500 lbs heavier than the C and needed to be (and in combat typically was) at a higher power setting, as I believe you basically said the same thing in another earlier post in this thread. Weight does also matter for speed, if not as much as drag goes. I posted other P-40D/E tests where they made 360+ and 355 mph which does seem to indicate they were faster than a Tomahawk.

MiTasol said:

I was under the impression that landing gear came from Don Berlin who designed the P-40 - why do you say it was a Boeing design?

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It may have Boeing that had the patent on the gear system that rotated the landing gear system as the landing gear leg retracted.
Grumman F6F and Chance Vought used the basic configuration but I don't know about the patent. they don't use the gears ? I don't know what Boeing plane actually used the system in 1930s, if any, or if it was just something a Boeing engineer came up with. with.

The ones on the Corsair though don't have the bulge on the front and the landing gear doors fully close. Every little bit of drag!

Wild_Bill_Kelso said:

The ones on the Corsair though don't have the bulge on the front and the landing gear doors fully close. Every little bit of drag!

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And look at the design of the inboard wing, it's thickness and what was inside.

Wild_Bill_Kelso said:

You posted all kinds of stats for a C vs. a D, I would say misleadingly claiming that there was no difference in drag between them based on the speeds. To me that is misleading.

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If you have two planes flying at the same speed or within a few mph at the same altitude (air density) while using the same power that means they must have the same drag.

It really is that simple.

A higher drag P-40 while flying at the same altitude using the same power (actually thrust about 80% efficient propeller + Exhaust thrust= total thrust ) would have to go slower than a low drag P-40 at the same altitude and thrust.

Now we might be able to argue about a better prop having better efficiency or we may be able to argue about one plane getting more exhaust thrust which is almost never counted but is some cases the exhaust thrust can be around 10% of of the total thrust.

We could also argue about which plane had higher induced drag and which one had higher parasitic drag but when we are looking at the different P-40s that gets a lot simpler than comparing to a Spitfire. Since the P-40s use the same wing then the only difference in induced drag is the angle of incidence of the wing (higher wing loading).
Since the P-40D is quite a bit heaver than the P-40B we may be able to assume that the P-40D is trading a little bit of parasitic drag to compensate for the higher induced drag.
But the total drag is the same.

we could argue about the accuracy of the test.

But as given:

The two planes display very similar drag over a range of different power levels.

You could try comparing to Spitfire II or V at 15,000 which was using more power (3000rpm and 9lbs of boost=48in)

Any other altitude it doesn't work as well unless you find the the power figures.
Or rather I should say you have to compare all the planes at the same altitude with the correct power figures.
The air at 20,000ft is about 85% as thick as the at 15,000ft so the plane at 20.000 is going to have less drag.
If you are doing this comparison do not mix up speeds at different altitudes and using different amounts of power.

In a test of of a Hawker Hurricane II with a Merlin XX engine they figured the exhaust horsepower (not thrust) at 15,000ft was 86.5hp while at 20,000ft using the same manifold pressure the exhaust horsepower was 113.0 mostly due to the exhaust gas exiting the nozzles about 300fps faster at 20,000ft than at 15,000ft due to the thinner air.

Just pointing out that changing altitude can start bringing in a bunch of small changes.

Wild_Bill_Kelso said:

but the D is ~500 lbs heavier than the C and needed to be (and in combat typically was) at a higher power setting

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at 15,000ft at just about 350mph both planes had the same power setting.
The -39engine at the P-40D/E was allowed to use more boost at lower altitudes (like around 12,000ft) but at 15,000ft it could not deliver any more air (power) than the -33 engine in the older P-40s.

Shortround6 said:

at 15,000ft at just about 350mph both planes had the same power setting.
The -39engine at the P-40D/E was allowed to use more boost at lower altitudes (like around 12,000ft) but at 15,000ft it could not deliver any more air (power) than the -33 engine in the older P-40s.

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Yes, but in those two reports you linked, one of those two planes (the P-40B) was tested a 6835 lbs, the other (P-40D) was tested at 7740 lbs, 905 lbs heavier! So I would expect the D to be slower at the same HP, RPM, and altitude. I know weight doesn't matter as much as drag in determining speed, but 900 lbs is not a trivial difference.

Most of the Boscombe down etc. tests on early Kittyhawks, and most of the Australian test were done at much higher weights, as much as 900 lbs heavier still, 8400-8800 lbs or more.

Of course we know other things effect speed at different altitudes, atmospheric conditions, temperature etc. From reading many of these tests they apparently 'correct' the results based on some formula. That makes it all the more confusing.

Wild_Bill_Kelso said:

Any of these seem like they could have been feasible?

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This. Proposal to purchase of Japanese aircraft for RAAF in 1939/40

Wild_Bill_Kelso said:

. I know weight doesn't matter as much as drag in determining speed, but 900 lbs is not a trivial difference.

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We have been conditioned to think that weight is more important than it was as far as speed goes.

that is pure weight with no impact at all on the exterior of the airplane. That rarely happens.

The change of 900lbs was not trivial, it just showed up in different ways. Like it affected to the climb rate of even that lightweight P-40D to point that the P-40B climbed 1900ft higher than the P-40D did in the same 5 minutes. and that is with the extra 60hp the -39 engine had. With with that slow down the American's had after 5 minutes the P-40B was just over 2 minutes faster to 20,000ft or to look at in the worst light, the P-40D took 25% longer to get to 20,000ft. Then you can throw in every thing else that weight hurts, including turn and acceleration.
The P-40C is supposed to have lost around 7mph of speed compared to the P-40B. The P-40C gained, like many P-40s, an extraordinary amount of weight.
The P-40C also gained the 52 gallon drop and like many planes given even a small under fuselage tank mount it cost speed in a disproportionate amount compared to the weight of the empty rack. An example of drag vs weight.

That said it seems like the wind over Buffalo may been traveling in a favorable pattern that gave good numbers
That or the Curtiss pilots were flying down wind of the Bell pilots.

Shortround6 said:

We have been conditioned to think that weight is more important than it was as far as speed goes.

that is pure weight with no impact at all on the exterior of the airplane. That rarely happens.

The change of 900lbs was not trivial, it just showed up in different ways. Like it affected to the climb rate of even that lightweight P-40D to point that the P-40B climbed 1900ft higher than the P-40D did in the same 5 minutes. and that is with the extra 60hp the -39 engine had. With with that slow down the American's had after 5 minutes the P-40B was just over 2 minutes faster to 20,000ft or to look at in the worst light, the P-40D took 25% longer to get to 20,000ft. Then you can throw in every thing else that weight hurts, including turn and acceleration.
The P-40C is supposed to have lost around 7mph of speed compared to the P-40B. The P-40C gained, like many P-40s, an extraordinary amount of weight.
The P-40C also gained the 52 gallon drop and like many planes given even a small under fuselage tank mount it cost speed in a disproportionate amount compared to the weight of the empty rack. An example of drag vs weight.

That said it seems like the wind over Buffalo may been traveling in a favorable pattern that gave good numbers
That or the Curtiss pilots were flying down wind of the Bell pilots.

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P-40B/C actually had a decent climb rate in some tests as high as 3,000 fpm.

Actually so did all the models when climbing with high boost, at least for the first 2 or 3 minutes. (A P-40D, as we know, actually had not 60, but more like about 350 more horespower available, up to around 8-10,000 ft)

But none of that changes my point, which you seem to be wiggling away from. I never claimed that weight was more important than drag, but 900 lbs (or 2000 lbs as with some of the other Kittyawk / Hawk 87 tests we have records for) is not a trivial difference and actually should affect speed, everything else being the same. This is indeed why the P-40C is typically listed as a bit slower than the B, in spite of having exactly the same engine and as far as I know, no significant difference in drag. The only difference is the C is a bit heavier.

Am I missing something?

Another thing that gets ignored is the drag from things like the drop tank hardware.

All that junk hanging there was creating drag on the P-40C that did not exist on the B did not benefit performance.

All US fighters up to and including the P-51 had a lot of hardware hanging from the aircraft after the drops were ejected which seems strange to me as the Japanese had managed to produce drops that left a perfectly clean aircraft even before Pearl Harbor.

Both the P-40 and the Ki-43 first flew in early 39. Both the Ki-43 and A6M had drop tanks that took all the aerodynamic a---holes with them when they separated. Most of the US and British aircraft used flexible hose(s) to connect their tanks to their aircraft and often parts of the flex hose would add to the drag. The Japanese used a plug and socket that produced little or no drag.

I would love to find the time machine the Japanese used so that they could copy things before other countries hand invented them

Good point, and I considered that, though I'm not sure that 'external furniture' for carrying the fuel tank or bomb was always there during the tests of the P-40C. There are a bunch of tests on WW2aircraftperformance and similar sites of P-40E, F, K, N and etc. with and without "sway braces" and they do seem to have an impact on performance. Tests at the factory, however, which I think is where the ~ 10 mph speed difference of the P-40B and C shows up, don't usually include the sway braces and etc..

So it is a valid question, but I think all things being equal, a few hundred pounds such as the B to the C, let alone the ~1,000 -2000 lbs for B to D /E will make a difference in speed. P-40B/C isn't the only example of this either, you can also look at the different tests of the E, which ranged from 330-360 mph, mainly depending on weight, and the different subtypes of the P-40N which varied as much as 40 mph I think also based on weight, (and also various other aircraft as well).

In December 1942 the RAAF reports it had 216 Twin Row Wasp on order, by September 1943 up to 1,000, down to 870 in April 1944

The period of the reported change over of reduction gearing types, W/ending, Cumulative total Delivered, Delivered for the Week, Notes
3-Mar-44, 551, 5, 9 completed, awaiting delivery
10-Mar-44, 561, 10, 4 completed, awaiting delivery
17-Mar-44, 566, 5, 4 completed, awaiting delivery
24-Mar-44, 570, 4, 4 completed, awaiting delivery
31-Mar-44, 572, 2, 6 completed, awaiting delivery
10-Apr-44, 579, 7, 2 completed, awaiting delivery
14-Apr-44, 579, 0, 4 completed, awaiting delivery
21-Apr-44, 582, 3, 5 completed, awaiting delivery
28-Apr-44, 582, 0, 9 completed, awaiting delivery

References, Files A705 9/18/108 and 150/4/1761. Minutes of Beaufort local Modifications Committee Meeting No.11 on 10 June 1942 and No.17 on 2 September 1942. Page 26 of 9/18/108 says marks IX and X unallocated. Pages 21 and 22 note a plan to install Pratt and Whitney R1830-43 into A9-332 and R1830-63 into A9-181

Australian twin wasp production began in November 1941 and finished in August 1945, 5 in 1941, 148 in 1942, 358 in 1943, 249 in 1944 and 110 in 1945, total 870. Single row wasp January 1939 to October 1942, June to September 1943, 680 made. Using official production figures, with 2 engines per Beaufort and 1 per Boomerang, assuming engines lasting airframe lifetime and lost/scrapped when the airframe is lost, the deficiency of Twin Wasp Engines in Australia end 1941 was 15, then 290 end 1942, 776 end 1943, peaked at 938 in August 1944 (last Beaufort production), down to 876 in December 1944, 870 in January 1945 (last Boomerang production) and to 780 in August 1945 (last Twin Wasp production)

Model, Qty, Engine, Changes

P-40N-1, 400, V1710-81, Similar to the P-40, E, K and M types of airplanes except as follows; Different engine with boost control; armament 4 0.50 cal. wing guns; no provisions for wing bombs, increased armour plate protection; no front wing tank; mechanical landing gear, flaps and indicators; non metallic tanks; SCR-522 radio; alternate SCR-274N; Type A-12 demand oxygen system. [Acceptance March 1943, stripped light weight P-40 similar to P-40H except change in armament, removal of battery, starter and auxiliary wing fuel tanks saving 484 pounds. Items reinstalled in service and N-5's were fully equipped]

P-40N-5, 1100, V1710-81, The last 3,600 P-40N-1 airplanes, redesignated with the following: landing gear book; revised pilot's seat; provisions for complete SCR-695 radio equipment; recognition lights; revised fuselage rear vision; provisions for wing bombs and wing fuel tanks; draft curtain; substitution of 27 inch magnesium wheels. [Armament increase, addition of auxiliary wing fuel tanks, wing racks to accommodate larger fuel tanks or bombs. Provision for trans Atlantic towing by B-17]

P-40N-10, 99, V1710-81, The last 3,500 P-40N-5 airplanes, redesignated with due to the addition of winterization equipment, manual oil dilution and rate of climb indicator.

P-40N-15, 377, V1710-81, Same as the P-40N-10 except for relocation of battery to a position forward of firewall and 1 landing light installation.

P-40N-20, 1523, V1710-99, Same as the P-40N-15 except for the following: V-1710-99 engine, which is the V-1710-81 engine plus the automatic engine control unit; installation of type A-1 bombsight.

P-40N-25, 500, V1710-99, Same as the P-40N-20 except for a hinged instrument panel requiring new filtered vacuum system for the reinstallation of gyro horizon and flight indicator and vacuum turn and bank indicator to replace electric type.

P-40N-30 500, V1710-99, Same as the P-40N-25 except that it has the DV-8 oil cooler valve and the line surge valve in lieu of the Harrison rotary valve.

P-40N-35, 500, V1710-99, Similar to the P-40N-30 except for the following: Deletion of the carburettor cold air valve; revised fuel system; gun mount bolt change; deletion of SCR-535 radio mounting provisions; canopy changes; deletion of upward recognition light; addition of turn and bank ball on gun sight; connector plug replacement; SCR-695 radio modifications; 60 amp circuit breaker.

P-40N-40, 220, V1710-115, Similar to the P-40N-35 except for the following: Engine change; deletions of camouflage; 30 inch wheels; metal covered ailerons; gun camera mounting; alclad ammunition boxes.

The P-40N-5 went from 7 to 9/16 wheel bolts, except the RAAF received a batch of them with 7/16 bolts in the 9/16 holes.

Australian Archives Series A1695 control 272/209/EQ page 109, changes P-40N-30 to 35 to 40 as of August 1944.
N-30 and N-35 have 27 inch landing wheels, N-40 will have 30 inch wheels
N-30 has three downward and one upward recognition lights, N-35 and N-40 have three downward lights only
Type N-30 is fitted with a model N2 gun sight aiming point camera and types N-35 and N-40 with a camera model N6
N-30 had provision for SCR515 radio, this has been deleted from N-35 and N-40

RAAF Chiefs of Staff report, 15 Mar 1944 Parts being made to enable replacement of V1710-81 with V1710-99 engines in P-40N. 6 Apr 1944 20 sets of parts made, more being made. The RAAF had received 165 P-40N-1 to N-15

"Provision for trans Atlantic towing by B-17"

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LolWut?