# Would a Merlin 60 powered p40 beat a p-51?



## helmitsmit (Sep 28, 2011)

Heard the P-40 was faster, better turn and rate of roll at low level (5,000ft) than P51D. Would a P-40F with merlin 60 series and longer nose but minimal changes to airframe beat 437mph at 25,000ft?


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## wuzak (Sep 28, 2011)

No.

P-51A was faster on the same power as the P-40.


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## Shortround6 (Sep 28, 2011)

I second the NO. 

If the Mustang had not out performed the P-40 the British wouldn't have bought it in the first place.


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## FLYBOYJ (Sep 28, 2011)

DEPENDS WHO WAS FLYING EACH AIRCRAFT!


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## GregP (Sep 29, 2011)

I think it is possible the new P-40 would generally out-perform the Mustang with a Merlin 60, but likely would not be faster. 

It would roll better, probably turn better, and would finally have high-altitude capability. The top speed would probably depend as much on the cleanliness of the installation as anything. I'd estimate the new P-40 would likely be in the low 400 mph range, say 410 mph or so. If they put on the Mustang's 4-bladed Ham-Std prop, who knows?

Top speed isn't everything, just ask a Hellcat pilot. It was probably the slowest US fighter of the war ... after 1943 anyway ... but it had the best kill ratio of any fighter in the world up until the F-15 Eagle.

As for the poll, it depends on what you mean by "win." Top speed ... probably the Mustang. All round performance, maybe the new P-40.

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## krieghund (Sep 29, 2011)

In a similar respect this was already tried with the P-40Q but the engine was an Allison V1710-121 with maximum WEP of 1800 hp. Its max speed was 422 mph at 20000ft at 9000lbs @ 161 gals and 4 x .50. Overall it was cleaned up nicely but alas to little to late as the P-51D could out range it easily. Two pictures included in USAAF colors and racing livery from the 1947 Cleveland Air Race. By virtue of the Q's lower wing loading and higher power loading it would out turn and out climb the P-51 at lower altitudes but the P-51 would be better at higher altitudes.

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## GregP (Sep 29, 2011)

Love the P-40Q and have for years. I understand it was a great plane but the war was winding down and the Mustang was doing very well, so they didn't see a need to indtroduce a new fighter, train the mechanics, and set up the logistics for a plane that basically flew as well as the P-51, that was already in service, did.

The later moel Allison was also a great-running engine, and was probably at a higher TBO than the Merlins, but that wasn't enough to start mass-production. I believe the HP was 1,425 (it was a V-1710-121) for takeoff, and it was still making 1,100 HP at 24,000 feet. The service seiling was 39,000 feet.


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## post76 (Sep 30, 2011)

This would not be a yes or no answer. 
If we are speaking of contemporary models, the P-40F would out climb the Mustang but would not match its top speed.
P-40 wins in radius and rate of turn up to about 300mph (IAS) where the Mustang gains with increasing speed as well as increases in altitude.
P-40 wins in radius at most other speeds having higher load factor, ie cuts tighter turn at cost to speed.
P-51 wins in level speed
P-51 wins in dive
P-51 wins in altitude performance and it is there where the P-51 would hold all the cards over the P-40.
At lower altitude the P-40 stands a chance.
Engagements would favor the P-51 as it would have the choice to fight or break away at will, having better top speed.

Its also fair to mention the P-40N-40, 200 built, that was manufactured with lighter aluminum. Total all up weight was 7000lbs. using 4 50 guns. 
It was reported as having a ceiling of 38k ft. 
This plane might offer better competition to the P-51D, particularly in the vertical.

A plane like the P-40Q would also narrow those gaps. 
Its performance sounds almost Ki-84ish... to me.

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## davparlr (Sep 30, 2011)

P-40 had a 37% higher CDzero than the P-51. It was never going to be faster. Turn rate is good but the history of the fighter was for better speed not turn rate. Pilots have always claimed that speed is life. Turn rate has not been called that.

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## Shortround6 (Sep 30, 2011)

davparlr said:


> P-40 had a 37% higher CDzero than the P-51. It was never going to be faster. Turn rate is good but the history of the fighter was for better speed not turn rate. Pilots have always claimed that speed is life. Turn rate has not been called that.



Well, if you changed the wing airfoil, and the plane form and the landing gear retracts. Then changed the fuselage, radiators and tail. Just a few more modifications to the canopy and cockpit you could get the "P-40" to beat the Mustang. But aside from the nameplate and a few screws/rivets it wouldn't be a P-40


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## post76 (Sep 30, 2011)

davparlr said:


> P-40 had a 37% higher CDzero than the P-51. It was never going to be faster. Turn rate is good but the history of the fighter was for better speed not turn rate. Pilots have always claimed that speed is life. Turn rate has not been called that.


 
I do wonder what a drag race at 10k ft looked like.
Obvously, the P-51 had the top end, but how far ahead would the P-40 get, if possible. 

Note that the P-51B would not match the P-40N in time to climb to 15k ft with out the use of 150 grade gasoline. 1944 figures.

Perhaps design developments for the P-40 focused on climb more so than top speed.
ie, prop chord and reduction gearing...



> Shortround6 ...But aside from the nameplate and a few screws/rivets it wouldn't be a P-40



What about just WEP and an octane boost?
Run the Allison at 75" instead of 57"....
then what?

Did they even bother testing them under such conditions, or would it still require too much retooling at the factory to make it 
worth it?
Afterall, you'd still need range even if it matched or exceeded the P-51s figures.


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## Shortround6 (Sep 30, 2011)

The P-40 you are referring to was a stripped down model. It turned out not be practical for combat and that is why so few were built and many of the ones that were built were modified in the field to heavier weights. Weight savings used were aluminium radiators and oil coolers instead of copper/brass, magnesium wheels which are not bad but more of the weight savings came from cutting the guns for 6 to 4 and limiting ammo to 201 rounds per gun. More weight was saved by leaving out one fuel tank and cutting internal capacity to 120 US gallons. The empty tank was about 100lbs, more weight was saved by leaving out the battery and electric starter for the engine. And the wing bomb racks were left off. 

Even if the engine would stand 75in of pressure that is going to last only a very short while. The supercharger was maxed out at 9500ft at 57in. above that the pressure fall so f and below that the pressure will increase until you get your 74in but that is going to be down around 1000ft or so. Great performance if the engine will last at 0-5000ft but not better than normal from 5000ft up with no difference from 9500ft up. What is the point?


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## Lighthunmust (Sep 30, 2011)

The question asked by the thread topic is “Would a Merlin 60 powered P-40 beat a P-51?”. Note the word “beat” and not the phrase “be a better fighter than” in the topic question. I voted for the P-40 because even the vaunted Mustang is not a 100%sure thing and because it ....



FLYBOYJ said:


> DEPENDS WHO WAS FLYING EACH AIRCRAFT!



It is not the size of the man in the fight, it is the size of the fight in the man that usually determines victory. I have read a few accounts of mock combats where a guy in a P-40 really surprised guys in "better" American fighters.


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## post76 (Sep 30, 2011)

Shortround6 said:


> The P-40 you are referring to was a stripped down model. It turned out not be practical for combat and that is why so few were
> built and many of the ones that were built were modified in the field to heavier weights. Weight savings used were aluminium radiators and oil coolers
> instead of copper/brass, magnesium wheels which are not bad but more of the weight savings came from cutting the guns for 6 to 4 and limiting ammo to 201
> rounds per gun. More weight was saved by leaving out one fuel tank and cutting internal capacity to 120 US gallons. The empty tank was about 100lbs, more
> weight was saved by leaving out the battery and electric starter for the engine. And the wing bomb racks were left off.



I'm citing situations and examples where the P-40 could beat the P-51 and reasons why it wouldn't.
The P-40N was the most ever built. The time to climb figures refer to the C-1 and C-5.
I've only heard of them being reconverted for bomber use, but most were used as trainers.




> Even if the engine would stand 75in of pressure that is going to last only a very short while. The supercharger was maxed out at 9500ft at 57in. above that
> the pressure fall so f and below that the pressure will increase until you get your 74in but that is going to be down around 1000ft or so. Great performance
> if the engine will last at 0-5000ft but not better than normal from 5000ft up with no difference from 9500ft up. What is the point?



That's probably what Curtiss asked. 
(Can i modify/develope this fighter to fly from Iwo to Japan and still be a competitive fighter?)
There was more to be had if they pursued installing the supercharging unit and water/alcohol system, as well as using 150 grade gasoline. 
All that went on the Mustang.
I'm just saying, it appears the room to expand performance was there with some simple performance modifications on the engine. 
Why change the airframe?
I would think that a higher grade gas and water would change the power chart figures you refer to, no?
The engine would prove to stand 100" using 1960s technology.
Did they know that in 1943-1944....who knows. 
Thats probably more of a question for General Motors than Curtiss.
Curtiss probably got through the first three prototypes and realized that the possibility for matching/exceeding P-51 performance was there, but
getting the same range and altitude performance would require a completely different airframe. 

What is the point, when you have not only the P-51 but a range of other birds capable of the same type of mission, and factories already producing 
them.


My educated opinion...


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## Siegfried (Oct 2, 2011)

The P-40 never received the same Power as the spitfire even when the P-40 was for a short time given the Merlin 20 it was an earlier lower powered version not that latter 1600hp ones. A Merlin 20 or 60 series engined P-40 would match the Spitfire V and IX respectively in maneuverability and speed, beat it in terms of roll rate, dive rate and range and be slightly inferior in climb rate.

However without the laminar profile wing its hard to get the speed and fuel load of the P-51.

This goes back to the US not developing a two speed supercharger for the Allison engine.


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## Jabberwocky (Oct 3, 2011)

Siegfried said:


> The P-40 never received the same Power as the spitfire even when the P-40 was for a short time given the Merlin 20 it was an earlier lower powered version not that latter 1600hp ones. A Merlin 20 or 60 series engined P-40 would match the Spitfire V and IX respectively in maneuverability and speed, beat it in terms of roll rate, dive rate and range and be slightly inferior in climb rate.


 
If you compare the Spitfire Mk V with the Merlin 45 at 1210 hp (+ 12 lbs), to the P-40F with the V-1650-1 at 1325 hp (54.5" hg), the Spitfire is marginally quicker below about 10,000 ft (typically less than 5 mph though), roughly similar between 10,000 and 16,000 and superior above about 18,000 ft. Allison-powered P-40s were typically faster than Spitfires below 10-12,000 ft, but slower above about 14,000.

The Spitfire is MUCH better in terms of rate of climb, typically having at least a 50% advantage between 0 and 10,000 ft and increasing from there. By 20,000 ft, a P-40F is climbing at 1300-1500 ft/min, a Spitfire Mk V is doing 2400-2700 ft min. Even lightened, more powerful Allison powered P-40s are at least 33% slower in terms of RoC.

The comparative roll rates of both the Spitfire and various P-40s depends on the period of the war. The Spitfire went through numerous changes to lateral control through the war. Early P-40s were much better than early Spitfires at all speeds. NACA 868 indicates that the Spitfire Mk V with metal skin ailerons would outroll the P-40 to 245 mph, after which the P-40 is increasingly superior. 

The Spitfire was generally lower wing loaded and had higher power loadings, but only marginally. This would indicate to me that the Spitfire would have better rate and radius of turn.


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## gjs238 (Oct 3, 2011)

Shortround6 said:


> Well, if you changed the wing airfoil, and the plane form and the landing gear retracts. Then changed the fuselage, radiators and tail. Just a few more modifications to the canopy and cockpit you could get the "P-40" to beat the Mustang. But aside from the nameplate and a few screws/rivets it wouldn't be a P-40


 Sounds like a description of the P-51H.


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## GregP (Oct 4, 2011)

I have often wanted to try a Merlin 2-stage supercharger on an Allison. Too bad they wont fit without major surgery.

The Allison is a very good engine that could have been improved quite signigicantly if the design was left to and owned by Allison instead of the US Government. Think of the possibilities if Sir Stanley Hooker had been asked to design a 2-stage, 2-speed supercharger for the Allison! 

Alas, he wasn't asked to help out, and he was probably the one person who could have done it without too much difficulty.

An so we are left with the Allison Aux Stage supercharger which, although it worked, was heavy and altogether too big for what it did ... and it came too late to be of much use in the war.


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## bobbysocks (Oct 4, 2011)

i think if it could be made to beat a 51 you would see it at the races. i would have liked to see what a merlin powered 40 could do but dont think it could have taken the role of the 51. that Q model does look nice though...


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## GregP (Oct 5, 2011)

The aricraft at the races were cheaply obtained when such aircatf were plentiful. There never was a plentiful P-40Q since they only made 2, and people don;t usually cut up a military fighter unless it is a little at a time.

It took 30 years for Rare bear to be dominant and 40+ years for Strega, with incremental improvements.


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## razor1uk (Oct 5, 2011)

*Expensively whistles*


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## tomo pauk (Oct 5, 2011)

'Invalid attachment'?


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## Zsnark (Sep 11, 2021)

gjs238 said:


> Sounds like a description of the P-51H.


I agree, why try to adapt an airframe which is essentially a tricked up 1930s P36 to compete with a later, better design. The P40 did OK until it was replaced by the P51, P47, and P38. 
The Mustang was simply a later, better design.


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## SaparotRob (Sep 11, 2021)

Shortround6 said:


> Well, if you changed the wing airfoil, and the plane form and the landing gear retracts. Then changed the fuselage, radiators and tail. Just a few more modifications to the canopy and cockpit you could get the "P-40" to beat the Mustang. But aside from the nameplate and a few screws/rivets it wouldn't be a P-40


It would be a P-39.


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## SaparotRob (Sep 11, 2021)

I'm leaving.

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## Thumpalumpacus (Sep 11, 2021)

SaparotRob said:


> I'm leaving.



Don't forget your coat, mister.

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## swampyankee (Sep 11, 2021)

Would a Merlin-powered P-40 beat a Merlin-engined P-51?

No. The P-51 was a newer design (as mentioned above, the P-40 was basically an upgraded P-36), with a much lower zero-lift drag, even disregarding the benefits (frequently severely overstated) of laminar-flow airfoils.

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