How good a plane was the P-40, really? (1 Viewer)

[Shortround6]

Agree with all that except I would say drag mattered maybe more than weight, P-51C weighed 9800 lbs up to 11800, but it was bloody fast. Fw 190A-8, also pretty fast, weighed 9,738 lbs according to one estimate I just hurredly googled

Weight is important. It has a very big effect on climb rate.
But Drag is also important, That 275 sq ft wing was actually better than the normal P-40 wing but the 236sq ft P-51 wing was better.
The Fw 190 197sq ft wing was tiny.
The Typhoon had a 279 sq ft wing, yes it was high drag, they also had the Sabre engine to drag it around.

That was the problem with the XP-60 series. It was too big for the available engines. If you cut 40 sq ft you can cut over 180lbs of weight from the wing, you can cut a fraction from the fuselage, you can cut a few pounds from the landing gear and so on.
P-40 wing was around 1120lbs.

Something to remember is that for surface drag you double the wing square footage.

 

[Wild_Bill_Kelso]

It seems, just observing anecdotally, that both the sq ft and the span seem significant. That and all the subtleties of streamlining of course. Those fat bodied P-60s were non-starters IMO regardless of the wing.

Thickness also matters a lot ala Hurricane and Typhoon

 

[pbehn]

It seems, just observing anecdotally, that both the sq ft and the span seem significant. That and all the subtleties of streamlining of course. Those fat bodied P-60s were non-starters IMO regardless of the wing.

Thickness also matters a lot ala Hurricane and Typhoon

NAA proposed a shorter wing span Mustang I to the British which would be faster, the British would only accept if RoC and take of runs were unaffected, which meant it wasnt accepted

 

[Wild_Bill_Kelso]

P-51 had such a low-drag that it was kind of a special case, IMO. And with the low drag comes a bit less lift...

 

[pbehn]

P-51 had such a low-drag that it was kind of a special case, IMO. And with the low drag comes a bit less lift...

I read it in a book written by a gentleman of this parish. It was at the time that a certain P-400 that cannot be mentioned was coming into service. or the British, at the time absolute top speed would not be traded for all around utility, the Mustang Mk I was already fast but was heavy, increasing take of runs and decreasing RoC for a small increase in max speed was not a great choice. In view of its future use loaded up with an extra circa 300 gallons of fuel and other "stuff" like oil and Oxygen, it was a great decision.

 

[Wild_Bill_Kelso]

Well, this is akin to a theory I've been working on for a while, to that same effect. Speed is a very important part of a military aircraft's panoply of traits, "speed is life", no doubt. But other things also matter. Agility for one. Climb as well. And dive (acceleration, endurance, top speed) was very much also a thing.

 

[Shortround6]

Speed was in part a function of altitude. Aircraft with a critical altitude below 20,000' is going to need a LOT of horsepower and very low drag to go over 400 mph. They don't care about the speed at Sea level or 10,000 ft, and the data card doesn't have a convenient way to summarize maneuverability. But it turned out in the operational history that faster planes like the P-39, P-51A, and early P-38 were not necessarily better in combat in terms of outcomes. Which is why the P-40 lingered. Same is true for some other types we've been discussing lately

There maybe a margin of speed that is needed?
The Allison Mustangs were not all that common The A-36s made up just under 30% of production. And British Mustangs were not often used in the fighter role.

The P-XX was not used in the west that much. Even in NA they shunted them off to "quiet" areas, I mean come on, Using single seat fighters with crap for range as anti-sub patrol aircraft? It's speed advantage may not have made up for other short comings.

Speed, climb and range are also somewhat intertwined.
P-40F at 8500lbs was supposed to need 5.4 minutes to reach 15,000ft. and need 34 US gallons to do it (includes warm up and take off, the time does not).
However the same 8500lb P-40F needs 21.4 minutes to reach 25,000ft and needs 56 US gallons to do it. So lets just call it 20 Gallons for that extra 10,000ft of altitude.
Now an 8500lb P-40F is not carrying a drop tank and might have started with only 120 gal in the tanks. That doesn't leave much for a standing patrol, combat or getting back to the base. (how good does a P-40 glide?)
Now you could fill the tanks, fit the drop tank and take off at 9300lbs but now the chart says 29.4 minutes to 25,000ft and 69 gal used. only 13 gallons more used and you have a lot more left. But still Roughly 33% of fuel used to take-off and climb to 25,000ft?
Some of the charts are a little generic and slop over bit but they give an idea. Not saying that things weren't done if they had to but P-40s and P-XX's took a while to reach higher altitudes, sucked up a lot fuel getting there and pretty much flew in straight lines when they got there. At about 2600rpm they were good for around 300-600fpm depending on weight.

 

[Wild_Bill_Kelso]

There maybe a margin of speed that is needed?
The Allison Mustangs were not all that common The A-36s made up just under 30% of production. And British Mustangs were not often used in the fighter role.

I mean, they were common enough in China and Burma for a while, you could evaluate say 8-10 combats between roughly equal numbers of Allison P-51s and Ki-43s just from that book I was using for the Ki-43 thread... which I still need to finish summarizing. You'll find that the P-51s didn't do so well. I myself found this surprising, and I believe it may have been down, at least in part, to the aileron rigging. Apparently this was fixed in the Merlin variants, I'm not sure if it ever was in the Allison variants.


And this is where the Ki-43s have a top speed about 40-60 mph slower depending on the precise matchups. Which is part of the point I'm going to make back in that Ki-43 thread.

You can also similarly find at least that many engagements with early model P-38s, P-43s, and P-47s with pretty similar outcomes (i.e., the Ki-43s usually came out on top). Same for P-39/ P-400 vs A6M2 and Ki-43 in the Solomons and over New Guinea.

The P-XX was not used in the west that much. Even in NA they shunted them off to "quiet" areas, I mean come on, Using single seat fighters with crap for range as anti-sub patrol aircraft? It's speed advantage may not have made up for other short comings.

If you mean 'the plane that cannot be named' they did try them on a couple of occasions in North Africa and they got slaughtered so badly (IIRC they lost 6 or 7 out of a flight of ten, with no victories) that they put them to work on Maritime patrol. Later in Italy though they seem to have figured out how to use them as fighter bombers without taking so many losses and they did get used in that role a fair bit, into 1944 IIRC.

Speed, climb and range are also somewhat intertwined.
P-40F at 8500lbs was supposed to need 5.4 minutes to reach 15,000ft. and need 34 US gallons to do it (includes warm up and take off, the time does not).
However the same 8500lb P-40F needs 21.4 minutes to reach 25,000ft and needs 56 US gallons to do it. So lets just call it 20 Gallons for that extra 10,000ft of altitude.
Now an 8500lb P-40F is not carrying a drop tank and might have started with only 120 gal in the tanks. That doesn't leave much for a standing patrol, combat or getting back to the base. (how good does a P-40 glide?)
Now you could fill the tanks, fit the drop tank and take off at 9300lbs but now the chart says 29.4 minutes to 25,000ft and 69 gal used. only 13 gallons more used and you have a lot more left. But still Roughly 33% of fuel used to take-off and climb to 25,000ft?
Some of the charts are a little generic and slop over bit but they give an idea. Not saying that things weren't done if they had to but P-40s and P-XX's took a while to reach higher altitudes, sucked up a lot fuel getting there and pretty much flew in straight lines when they got there. At about 2600rpm they were good for around 300-600fpm depending on weight.

Well I don't know the precise details but the P-40Fs were being used to escort B-26s to Sicily from North Africa, and to Sardinia and Corsica from Sicily, and from Naples and later Corsica to Anzio and back (both with and without bombs) sometimes twice a day. So I guess they figured it out.

Also seeing as a P-40F could make 365-375 mph at 20,000 feet they weren't exactly dying at 25,000

According to this in July 1942 a P-40F at 8,450 lbs was still making 1,000 fpm at 25,000', and 530 fpm was at 30,000 ft., which is about the effective limit. Time to 25,000' is listed as a little over 14 minutes. I kind of doubt they used up 1/3 of the fuel just to get there.

 

[Wild_Bill_Kelso]

I read it in a book written by a gentleman of this parish. It was at the time that a certain P-400 that cannot be mentioned was coming into service. or the British, at the time absolute top speed would not be traded for all around utility, the Mustang Mk I was already fast but was heavy, increasing take of runs and decreasing RoC for a small increase in max speed was not a great choice. In view of its future use loaded up with an extra circa 300 gallons of fuel and other "stuff" like oil and Oxygen, it was a great decision.

The converse of this decision on the Mustang was IIRC that the FAA decided to 'clip' 8" from the wings of the F4U Corsair, I think to do with fitting it in the ship, but it apaprently suffered no ill effects.

 

[pbehn]

The converse of this decision on the Mustang was IIRC that the FAA decided to 'clip' 8" from the wings of the F4U Corsair, I think to do with fitting it in the ship, but it apaprently suffered no ill effects.

From what I read it improved landing by increasing the "sink rate" and reducing the tendency to "float" across the deck, there must have been a trade off with take off climb and altitude performance but 2000BHP can make up or a lot. Many Spitfires were customised with clipped wings, extended wings armament and even radios deleted for low level, high level or PR types but in all cases they were making a trade off, one thing for another.

 

[Shortround6]

According to this in July 1942 a P-40F at 8,450 lbs was still making 1,000 fpm at 25,000', and 530 fpm was at 30,000 ft., which is about the effective limit. Time to 25,000' is listed as a little over 14 minutes. I kind of doubt they used up 1/3 of the fuel just to get there.

This is the problem with trying to combine charts.
The normal climb to altitude chart combines both the time to altitude and the fuel burn from start up which are obviously different things.
Next problem is trying to reconcile the times quoted with the throttle settings.

In the test you posted they used 2850rpm and 48in (9lbs of boost) for the entire climb. The chart in the manual uses a lower throttle setting.
Now at 2850rpm and 48in the engine is burning about 110 gals an hour. or about 25-26 gallons just for that time to climb. Not quite full throttle. But it seems to take 15-22 gallons just to get off the ground and a few thousand feet of altitude.

Now we run into what the manual says, what they did in certain tests and what they did in the field.
The early/mid 1943 Manual for the P-40F/L says to use 2650rpm and 44.2in for max cruise.
The British used 2850rpm and 48in (9lbs) for up to 30min of climb.
The US never used the British 30 minute ratings in any US manual (?) for any Merlin.
Maybe the pilots in the field used the British limits or something close?
Obviously 2650rpm and 44.2in (7lbs) is going to used less fuel per minute than 2850rpm and 48in. The higher power may actually save fuel slightly by getting to altitude quicker.
The next problem is that unless the planes are in combat they are not using 2850rpm and high boost for flying around at 25,000ft.

Well I don't know the precise details but the P-40Fs were being used to escort B-26s to Sicily from North Africa, and to Sardinia and Corsica from Sicily, and from Naples and later Corsica to Anzio and back (both with and without bombs) sometimes twice a day. So I guess they figured it out.

They figured it all right. The P-40Fs were not flying at 25,000ft to escort B-26s. Since the B-26 had engines that had critical altitudes of under 15,000ft they flew thousands of feet lower than B-17s/B-24s. Corsica to Anzio is usually under 200 miles. Now the fighters may have wanted 3-6,000ft? more than the bombers. and the P-40F/L were worth 3-4,000 ft more than P-40Ns.

 

[Wild_Bill_Kelso]

double post

 

[Wild_Bill_Kelso]

From what I read it improved landing by increasing the "sink rate" and reducing the tendency to "float" across the deck, there must have been a trade off with take off climb and altitude performance but 2000BHP can make up or a lot. Many Spitfires were customised with clipped wings, extended wings armament and even radios deleted for low level, high level or PR types but in all cases they were making a trade off, one thing for another.

Oh yeah you are right I forgot about that sink rate

 

[Wild_Bill_Kelso]

This is the problem with trying to combine charts.
The normal climb to altitude chart combines both the time to altitude and the fuel burn from start up which are obviously different things.
Next problem is trying to reconcile the times quoted with the throttle settings.

In the test you posted they used 2850rpm and 48in (9lbs of boost) for the entire climb. The chart in the manual uses a lower throttle setting.
Now at 2850rpm and 48in the engine is burning about 110 gals an hour. or about 25-26 gallons just for that time to climb. Not quite full throttle. But it seems to take 15-22 gallons just to get off the ground and a few thousand feet of altitude.

Now we run into what the manual says, what they did in certain tests and what they did in the field.
The early/mid 1943 Manual for the P-40F/L says to use 2650rpm and 44.2in for max cruise.
The British used 2850rpm and 48in (9lbs) for up to 30min of climb.
The US never used the British 30 minute ratings in any US manual (?) for any Merlin.
Maybe the pilots in the field used the British limits or something close?
Obviously 2650rpm and 44.2in (7lbs) is going to used less fuel per minute than 2850rpm and 48in. The higher power may actually save fuel slightly by getting to altitude quicker.
The next problem is that unless the planes are in combat they are not using 2850rpm and high boost for flying around at 25,000ft.

I'll take your word for it. Like I say, the details are a bit beyond me, you know it better than I do but you also know it's tricky and there are various ways to measure it. From what I gather they would sometimes patrol at around 22 -23,000' depending on the exact conditions. They could clearly go higher when they needed to. Often they were flying and fighting much lower.

They figured it all right. The P-40Fs were not flying at 25,000ft to escort B-26s. Since the B-26 had engines that had critical altitudes of under 15,000ft they flew thousands of feet lower than B-17s/B-24s.

Yes very true, in fact the P-40s were not considered suitable to escort the B-24s which would sometimes (for longer missions) fly at higher altitude above 20,000 ft so as to make interception more difficult. The B-26s would sometimes fly as low as 7 or 8,000 feet from what I understand, considerably higher for longer missions. The thing was in both cases, you had both close escort and high cover. P-38s were normally used to escort the B-24s on longer missions.

Corsica to Anzio is usually under 200 miles. Now the fighters may have wanted 3-6,000ft? more than the bombers. and the P-40F/L were worth 3-4,000 ft more than P-40Ns.

P-40Ns were not used by the Americans in the MTO, as far as I know. The British used them (as Kittyhawk IV) but only as fighter bombers.

For escorting bombers, as I mentioned above, you would have a close escort, flying near the bombers altitude, and high cover which did have to be up at about 20,000 ft because that is where the Axis fighters would sometimes be. High cover might just be a single flight of planes though (i.e. 4 aircraft), depending on the size of the raid.

This was quite important regardless. It is why the US almost exclusively used the Merlin P-40s in the MTO, precisely because you could put some on high cover to protect from the bounce. That apparently made a big difference in outcomes. 57th FG did use some P-40k for a while, due to a shortage of Merlin engines and spares, but they sorted that out with a deal with the British and went back to all P-40F/L after that.

 

[Wild_Bill_Kelso]

The other part, about 200 mile range, I think you know this but it bears repeating. A 'stat block range' of 800-900 miles translates to ~200 or ~250 miles of actual operational range, with allowances for combat, for damage, for navigation problems getting to the target and back to base etc.

I don't know what the actual operational range of the P-40F was with the external tanks but I knew they were using them and flying across the Med in them. And that the P-40 had the best range of any Allied fighter in North Africa except the P-38.


View: https://youtu.be/IRhX_Jdj5AU?t=232

 

[BarnOwlLover]

It seems that the issue with the Allison Mustangs was indeed how the ailerons were set up. This was fixed on the Merlin P-51s with 10, 12 or 15 degree rigging. Ironically, it was tested on a Mustang I that was modified to be an A-36 prototype which also tested 20mm cannon fits, per post #153 in the A-36 picture thread.

Problem is unless we have the performance reports on that particular aircraft and a similarly powered P-40, we're always going to sort of be comparing apples to oranges for one reason on another. Even comparing the P-51B/D to the XP-40Q is going to be a bit like that, due to the fact that two were production planes and one was experimental. Now if you compare to XP-40Q to the XP-51F/G or its offspring (P-51H, which didn't see active combat in World War II though fighter units in the USAAF were equipped with them prior to August 15th '45), that's a bit more fair in terms of experimental plane vs experimental plane.

Unfortunately, it also shows how far behind the curb the P-40 was by then, and probably that Curtiss/Curtiss-Wright had too many irons in the fire with stillborn programs that amounted to nothing.

For whatever reason, until the Q, the P-40 never seemed to have the "stretch" in capability that the Spitfire and even the Me-109 had. And given the later -109's issues with that, that's sort of saying something. Though in fairness to the P-40, at least it's handling and overall performance didn't deteriorate (speed and climb just hit a wall), while the -109 suffered pretty badly until it got some of it's mojo back with the late G and K series.

But we do have to be fair in terms of combat performance. The least that can be said of the P-40 was that it held its ground and helped pave the way for better aircraft that came later, just as the Allison Mustangs did and other designs.

 

[Wild_Bill_Kelso]

It seems that the issue with the Allison Mustangs was indeed how the ailerons were set up. This was fixed on the Merlin P-51s with 10, 12 or 15 degree rigging. Ironically, it was tested on a Mustang I that was modified to be an A-36 prototype which also tested 20mm cannon fits, per post #153 in the A-36 picture thread.

Appreciate the clarification

Problem is unless we have the performance reports on that particular aircraft and a similarly powered P-40, we're always going to sort of be comparing apples to oranges for one reason on another.

I think with the operational history you can compare like with like fairly well.

Even comparing the P-51B/D to the XP-40Q is going to be a bit like that, due to the fact that two were production planes and one was experimental. Now if you compare to XP-40Q to the XP-51F/G or its offspring (P-51H, which didn't see active combat in World War II though fighter units in the USAAF were equipped with them prior to August 15th '45), that's a bit more fair in terms of experimental plane vs experimental plane.

I think P-40Q, as interesting as it was, is a dead end precisely because it was an experiment, and one which failed basically due to a bunch of prototype crashes. It looked pretty good on paper but it probably wasn't as good as a late model P-51 or Spitfire, let alone a jet, so it wasn't bringing anything new to the table. And those crashes may have been due to errors on the side of Curtiss, given the many issues they were having at that time. That, in turn, probably predicts problems Curitss would have in production, which the USAAF and War Dept were already more than weary of.

Unfortunately, it also shows how far behind the curb the P-40 was by then, and probably that Curtiss/Curtiss-Wright had too many irons in the fire with stillborn programs that amounted to nothing.

Behind the 'curve' I think you mean, and yes I totally agree.

For whatever reason, until the Q, the P-40 never seemed to have the "stretch" in capability that the Spitfire and even the Me-109 had.

Well, to be fair, until the Q, nobody put anything remotely similar to a two-stage Merlin 60 or a DB 605 type engine in it.

But since the Mustang was clearly going to be faster regardless, and had the potential for twice the range, and same for the P-38 and ultimately, the P-47, I think they went the right way.

And given the later -109's issues with that, that's sort of saying something. Though in fairness to the P-40, at least it's handling and overall performance didn't deteriorate (speed and climb just hit a wall), while the -109 suffered pretty badly until it got some of it's mojo back with the late G and K series.

But we do have to be fair in terms of combat performance. The least that can be said of the P-40 was that it held its ground and helped pave the way for better aircraft that came later, just as the Allison Mustangs did and other designs.

This is where I diverge from the standard trope. I'd say in Dec 1941- May 1942 ... roughly, the P-40 (mostly) held it's own. From June 1942 it mostly did a little better than hold it's own, even while some newer types were having serious teething issues or running into limitations. And that is why they kept it in the fighter role as long as they did.

As is no doubt obvious, I've done a deep dive into this, as the discrepancy between several individual pilot and individual unit assessments of the P-40 and the summary of it's general traits and history is a yawning chasm, and one of the mysteries of the war for me. Fighter units that are pulling their weight usually score about 2-1 or 3-1 or better in terms of victories to losses. That is because they don't always face other fighters of the first rank, so at least some of their combat encounters should be relatively easy.

For a long time there was really no way to verify anything. All we had was some stats and some wartime legends, really. Now thanks to Shores, Claringbould et al, we can see the details of operational history on both sides. In the early 'desperate days' of 1941-mid 1942, with the exception of the AVG, most P-40s units were doing about 1 for 1, or 1 for 2 (as in, two p-40s lost per 1 enemy aircraft) depending on the specific theater and battlefield. This was at a time when most other Allied fighters were doing a good bit worse than that, so they kept them 'in the breach'. AVG was doing better than that, about 2-1 against enemy fighters and about 3-1 overall, partly due to better tactics. From mid 1942, thanks to improved tactics and training plus a bit better aircraft variants, most P-40 units all over the world, US, RAF, RAAF, SAAF, RNZAF, and Soviet / VVS, were doing 2-1 or 3-1, and that continued until some time in 1944 in most cases.

So I would say that ultimately as a fighter type, over the course of the war it did more than hold it's ground.

 

[BarnOwlLover]

We also gotta be fair, a lot of things that get lambasted for being ineffective or obsolescent/obsolete, be it Allied or Axis, worked as intended when introduced. But things marched on so fast that things could quickly be obsolescent. And we do have to be careful at times, too, of the "vs" arguments. For non-aviation examples, the original M1 Bazooka AT rocket launcher and the PIAT AT spigot mortar. They worked against most tanks that the Germans had until the end of the war, let alone upgraded examples of those AT weapons. Where they fall down is when used against say the Tiger or King Tiger, which, while fearsome tanks, one, were relatively small in number compared to say the stalwart Panzer IV (which was produced in improved variants until War's end), and the Tiger tanks had their own shortcomings as well. Granted, quite a bit of that wasn't known by the Allies until later on, though.

Also, the M4 Sherman tank on paper (aside from maybe the later versions) seemed helpless in a one on one fight against a Tiger or King Tiger, but that's sort of apples to oranges (medium tank vs heavy tank). A more fair comparison would be against the Panzer IV or even the Panther.

Hence my point about "holding the line" and paving the way for what would come later.

From that standpoint, it can be argued for sure that the P-40 was made obsolescent by advancing Allied and Axis fighters. But it wasn't like the USAAF made the same mistake that say Italy did with sticking with the Fiat CR 32/42 biplanes when the tide already turned in favor of newer designs. But it does seem to be a common theme about things hitting walls and such in the aviation field, among others.

It's like the P-51's continual evolution and improvement, which has been touched upon here and elsewhere, same applies for the Spitfire and so on. Eventually, things will hit a wall. But sometimes, especially in the case of the Axis in terms of aviation, they did hit walls, but instead of improving, things stagnated until it was too late to adequately compensate. And not all of it (most of it isn't) attributed to poor planning or carelessness. Sometimes (a lot of times, actually), it was a case of better things in the pipeline that didn't come soon enough. Granted, especially with the Nazis there was a lot of political ineptitude going on, especially from 1942 onwards, but not always.

For whatever reason, maybe to make up for getting knocked a bit off kilter, the Allies were often quicker to try and address the balance and eventually achieve overmatch, both though quality and quantity.

As how this pertains to the P-40, we might not have had say the P-51 ultimately without the P-40. It was the P-40 and NAA's fears of it being an obsolescent design that would be nearing a developmental dead end that spawned their decision to proceed with what would become the Mustang. Also, we needed something to hold the line until better planes (P-51, P-47, P-38) were available in numbers. And the Brits/Commonwealth needed a fighter to hold the line in North Africa until enough Spitfires were built up to hold the line in England and could be sent to other theaters in numbers. And it did that better than some of the alternatives. Not to mention how many pilots of those later aircraft cut their teeth on P-40s in training to hone their skills. That was a big help right there.

And in fairness, I did read that P-40s even gave Ki-84s trouble in the CBI when they first clashed. Possibly what may've lead to opinions in the IJA in that theater on the Ki-84 and that some pilots felt that they would be at a disadvantage to say Merlin P-51s and two stage Spitfires.

 

[pbehn]

So I would say that ultimately as a fighter type, over the course of the war it did more than hold it's ground.

I agree, plus most of the issues with the P-40 stem from its engines supercharger, not from the airframe itself.

 

[GrauGeist]

But it wasn't like the USAAF made the same mistake that say Italy did with sticking with the Fiat CR 32/42 biplanes when the tide already turned in favor of newer designs.

The Fiat CR.42 was introduced into service in 1939 but it was not alone.

Thr Gloster Gladiator was introduced into service in 1937, the Polikarpov I-153 was introduced into service in 1939, the Henschel Hs123 was introduced into service in 1936. All these types saw combat during WWII and though deemed obsolete, performed well enough that many were still in use by 1944.

In the case of American types, the USN had the Curtiss SBC accepted into service in 1938 and the Grumman F3F accepted into service in 1936 and even placed orders for more as late as 1938.
While not seeing combat in WWII, the two types served well into 1943 before being retired.