If no P-51, how would the P-40 have evolved?

riacrato · Jun 5, 2012

Spitfire was pretty low-drag for late 30s / early 40s standard, except for a few areas.

AFAIK P-40 had a complex and heavy spar structure, something that wouldn't be easy to change.

Shortround6 · Jun 5, 2012

spicmart said:
At what point can one say that a certain design's development potential is used up. How can one measure that? Looking at the airframe one can get the impression that if given a powerful enough engine and maybe a relocating of the coolant radiator that the P-40 might be competitive with the Spitfires which also were not low-drag-wonders. At least why shouldn' it be?

How many times do you want to re-locate the radiator?

They tried at least twice after the P-40E and the original XP-40 was tried with 2 different locations and the forward location with at least two different cowls/housings.

krieghund · Jun 6, 2012

The first step to improve the P-40 is for Allison to develop a 2-stage supercharger for the V1710 then clean up the aircraft as the P-40F equipped with the V-1650-1 shows a 2-stage engine is not much better than a single stage engine without cleaning up the aerodynamics.

The P-40Q is in the right direction.

wuzak · Jun 6, 2012

krieghund said:
The first step to improve the P-40 is for Allison to develop a 2-stage supercharger for the V1710 then clean up the aircraft as the P-40F equipped with the V-1650-1 shows a 2-stage engine is not much better than a single stage engine without cleaning up the aerodynamics.

The P-40Q is in the right direction.

The V-1650-1 was a single stage engine. It had a two speed gearbox, unlike the V-1710, which had just the singke, fixed, ratio.

krieghund · Jun 6, 2012

wuzak said:
The V-1650-1 was a single stage engine. It had a two speed gearbox, unlike the V-1710, which had just the singke, fixed, ratio.

Yes thanks for the correction. that is what I meant. The P-40 was more maneuverable than the P-51D and the only ace the P-51 had was its speed, it could disengage at will.

FLYBOYJ · Jun 6, 2012

krieghund said:
The P-40 was more maneuverable than the P-51D.

And your proof of that? At what speed and altitude, or is that a blanket statment? So please let us know your sources for that...

GregP · Jun 6, 2012

I think the P-40 had great potential.

The XP-40Q was about as good as a Mustang, though about 10 mph slower. In combat, 10 mph is meaningless. The real issue with the P-40 was not the basic design, but the wing and airfoil and lack of a high-altitude engine. Had they fielded an upgraded airfoil (higher critical mach number) with a wing area sufficient to give a combat wing loading of, say, 35 – 38 pounds per square foot, and added a 2-stage, 2-speed supercharger OR a turbocharger, then things might have been quite different.

At low altitudes the P-40 was a very dangerous opponent and out-rolled most of the competition. It was also decently fast at about 360 mph down low. On the deck, not many were, in fact, faster. The P-51D, while it could make 437 mph at height, was about a 360 mph at sea level, right along with the P-40.

Let's remember that they DID add a Merlin to the P-40 in the P-40F. However, it was a single-stage, single-speed unit and the performance was no better than with the single-stage, single-speed Allison. Had they added a multi-stage, multi-speed unit, then things at higher altitudes would have been different. It might or might not have been a world beater, but would have given a nasty surprise to many.

Trebor · Jun 6, 2012

michaelmaltby said:
XP-40Q

lol wow the only thing P-40 about it is the tail, and maybe the nose

Trebor · Jun 6, 2012

krieghund said:
Yes thanks for the correction. that is what I meant. The P-40 was more maneuverable than the P-51D and the only ace the P-51 had was its speed, it could disengage at will.

the P-40 was barely even maneuverable. the only way that the Flying Tigers could defeat Japanese fighters was to take advantage of its ruggedness and speed and take them head on. (I may be missing some things, fellas. if you'd like, contribute)

Milosh · Jun 6, 2012

Trebor said:
the P-40 was barely even maneuverable. the only way that the Flying Tigers could defeat Japanese fighters was to take advantage of its ruggedness and speed and take them head on. (I may be missing some things, fellas. if you'd like, contribute)

How would the Fw190 or the Bf109 have faired against the Japanese fighters.

Trebor · Jun 6, 2012

Milosh said:
How would the Fw190 or the Bf109 have faired against the Japanese fighters.

what? I don't know. I don't think German fighters ever faced off against Japanese fighters

Shortround6 · Jun 6, 2012

GregP said:
I think the P-40 had great potential.

The XP-40Q was about as good as a Mustang, though about 10 mph slower. In combat, 10 mph is meaningless.

10mph may be meaningless the actual difference is a bit greater. I could be wrong but I believe the P-40Q carried 4 guns with about 200-201 rounds per gun?
Going to six guns or 350-400rpg (or both) may may little difference in speed but a much larger difference in climb, turn and initial roll. Just going from 200rpg to 350rpg for four guns is 180-190lbs. Some sources claim production models would have had six .50s or four 20mm cannon which really would have affected certain aspects of performance.

GregP said:
At low altitudes the P-40 was a very dangerous opponent and out-rolled most of the competition. It was also decently fast at about 360 mph down low. On the deck, not many were, in fact, faster. The P-51D, while it could make 437 mph at height, was about a 360 mph at sea level, right along with the P-40.

Please define "down low". On the deck the only way a P-40 was going to get to 360mph unless pulling out of a dive was by using JATO rockets. Most sources give under 300mph with normal military power and one source gives 314mph at sea level for a P-40N using a -81 engine using 57in MAP (13.5-14lbs boost) WEP. This is at 7900lbs which means aluminium radiators and oil coolers, smaller wheels and brakes, no forward wing tank and a few other tricks to lighten the plane. It is a test done by the RAAF and perhaps not up to Curtiss factory standards but it rather hard to see were another 40-45mph is going to come from.

GregP said:
Let's remember that they DID add a Merlin to the P-40 in the P-40F. However, it was a single-stage, single-speed unit and the performance was no better than with the single-stage, single-speed Allison. Had they added a multi-stage, multi-speed unit, then things at higher altitudes would have been different. It might or might not have been a world beater, but would have given a nasty surprise to many.

The engine used in the "F" was a two speed single stage unit, not single speed. Performance was "relocated" compared to an "E" model P-40. Performance "down low" was a bit worse but performance above 15,000ft was better. Some tests (or charts) showing a speed advantage of 30mph or more above 20,000ft for the "F".

tomo pauk · Jun 6, 2012

Trebor said:
the P-40 was barely even maneuverable. the only way that the Flying Tigers could defeat Japanese fighters was to take advantage of its ruggedness and speed and take them head on. (I may be missing some things, fellas. if you'd like, contribute)

Hi,
It depends what kind of a maneuvre one wants the P-40 to make, at what speed and at what altitude. P-40 was one of the best rollers between 200-300 mph (only Spit w/ clipped wings Fw-190 being better), with the rate of roll being twice as good as the Zero (and almost 3 times as good at 300 mph), for example. If one rolls to slow, he is an awarding target (= ill able to throw off enemy's aim), and will be too late to make a turn.
Of course, trying to make maneuvers with the P-40 at 25000 ft (where his V-1710 acts like he's lacking 6 of it's 12 cylinders) is not something that P-40 drivers should be trying to often.

krieghund · Jun 8, 2012

FLYBOYJ said:
And your proof of that? At what speed and altitude, or is that a blanket statment? So please let us know your sources for that...

Dang, knew someone would call me on that before I could get my source. It is in a P-51 book discussing pilot training in the states flying comparison between the P-40 and P-39 against the P-51D. The only things going for the P-40 were its roll rate and turn rate which I assume is below the critical altitude of the the Allison.

The same book also describes a USAAF group commander describing how his Allison powered mustangs with ruined bearings would bring them home but a Merlin mustang wouldn't.

Still looking.........

FLYBOYJ · Jun 8, 2012

krieghund said:
Dang, knew someone would call me on that before I could get my source. It is in a P-51 book discussing pilot training in the states flying comparison between the P-40 and P-39 against the P-51D. The only things going for the P-40 were its roll rate and turn rate which I assume is below the critical altitude of the the Allison.

As indicated earlier, the P-40 had one of the best roll rates of any WW2 single engine fighter but in the end, depending on speed and altitude (and of course pilot ability) it was not going to out-maneuver a P-51 across the board. Where the P-40 had its strengths, the P-51 had other attributes (acceleration, power to weight ratio) that can cancel the P-40s advantages, again this depending on speed altitude and pilot skill.

krieghund · Jun 8, 2012

FLYBOYJ said:
As indicated earlier, the P-40 had one of the best roll rates of any WW2 single engine fighter but in the end, depending on speed and altitude (and of course pilot ability) it was not going to out-maneuver a P-51 across the board. Where the P-40 had its strengths, the P-51 had other attributes (acceleration, power to weight ratio) that can cancel the P-40s advantages, again this depending on speed altitude and pilot skill.

Agreed, however, a p-40 drawing 70" it could give the 'tang a run for its money at lower levels which is where pilot training BFM was probably performed.

GregP · Jun 8, 2012

Actually the XP-40Q was almost a stock P-40 airframe. The turtledeck was cut down and the engine installation and radiator were improved, along with the engine itself, and it was fitted with a 4-bladed prop.

There was a LOT of basic P-40 in it.

Shortround6 · Jun 8, 2012

krieghund said:
Agreed, however, a p-40 drawing 70" it could give the 'tang a run for its money at lower levels which is where pilot training BFM was probably performed.

what happens when the " 'tang " pulls 70" ? or even 67"

FLYBOYJ · Jun 9, 2012

krieghund said:
Agreed, however, a p-40 drawing 70" it could give the 'tang a run for its money at lower levels which is where pilot training BFM was probably performed.

Shortround6 said:
what happens when the " 'tang " pulls 70" ? or even 67"

And do want to start comparing wingloading as well?

krieghund · Jun 9, 2012

FLYBOYJ said:
And do want to start comparing wingloading as well?

And don't forget the airfoil differences between the them as well as prop efficiencies, etc. This could wind down into an Urinary Olympics.

If no P-51, how would the P-40 have evolved?

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