P40: The underated underdog, or just behind the times

"The reason Performance didn't change much with the change to the Merlin was because that Merlin was setup similarly to the Allison, i.e., single stage/single speed supercharger."

No, the Merlins used in the P-40 had single stage TWO speed superchargers.

They used 8.15 and 9.49 gear sets and were rated at 1240HP at 11,500ft and 1120hp at 18,500ft using 9lb of boost ( 48")compared to the later P-40 Allisons which gave 1125hp at 15,500ft at 7.25lbs of boost (44.5in)

The Merlin was rated at 1300hp for take off compared to the late Allisons 1200hp.

Going to the TWO stage Merlin design of supercharger would have ment an extra couple of hundred pounds of engine weight NOT INCLUDING the Liquied radiator for the aftercooler. This radiator has to be placed somewhere and will add at least some drag.

THE question is not weither it could be done but weither the improvement was worth the effort and the delay or interuption in production.

I watched Season 1 of Dogfights last night, and episode #3 was about the Flying Tigers. I've always like the P-40 but even I gained greater respect for it after watching the show. I certainly could hold her own and dish it out!

Shortround6 said:

"The reason Performance didn't change much with the change to the Merlin was because that Merlin was setup similarly to the Allison, i.e., single stage/single speed supercharger."

No, the Merlins used in the P-40 had single stage TWO speed superchargers.

They used 8.15 and 9.49 gear sets and were rated at 1240HP at 11,500ft and 1120hp at 18,500ft using 9lb of boost ( 48")compared to the later P-40 Allisons which gave 1125hp at 15,500ft at 7.25lbs of boost (44.5in)

The Merlin was rated at 1300hp for take off compared to the late Allisons 1200hp.

Going to the TWO stage Merlin design of supercharger would have ment an extra couple of hundred pounds of engine weight NOT INCLUDING the Liquied radiator for the aftercooler. This radiator has to be placed somewhere and will add at least some drag.

THE question is not weither it could be done but weither the improvement was worth the effort and the delay or interuption in production.

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Sorry, my mistake on the s.c., but the Allison's that were fitted to the P-40 were rated at 1150HP on take-off, not 1200.



Elvis

Elvis said:

Sorry, my mistake on the s.c., but the Allison's that were fitted to the P-40 were rated at 1150HP on take-off, not 1200.
Elvis

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Which P-40?

The -39 engines in D's and E's were rated at 1150HP.
The -73 engines in the K's were rated at 1325HP.
The -81,-99 and -115 engines in the M's and N's were rated at 1200HP.

One might compare the tomahawk with a Spit Mk 1. Look at the Griffon Spits and the Merlin Spits and one would see a virtually new airframe.
Compare the dimensions of a Mk 1 and later Spits with Griffons.
The Griffon was a much bigger and heavier engine than the Merlin requiring major changes to the airframe.
If one were to put a Griffon in a P 40 it would'nt be a P 40 any more.
The planform of a Griffon Spit is deceiving. It closely resembles Merlin engined Spits.

I'm new to this site and actually stumbled upon it looking for something. Very nice posts by all and the research or experience you all must have done to collect the data regarding the P40's from the 1st XP40 to the very last XP40Q or the name she was given, (Suzy-Q). Lots of what I'm reading is miss leading, or beating around the bush, witch may be from anger or from the love of this aircraft or neither. Yes the Rolls Royce/Merlin was the last engine to be used in this great or not so great aircraft.

I had to live with the P40 my entire life and know of it's existence from start to finish because my Grandfather was Walter Tydon who designed the P40. To me the P40-B is my favorite and the later P51's are up there also. I should have never mentioned that around my Grandfather. Here is why... If you look at the XP40, the very 1st one, it had the Marsupial Cooling System on the belly of the craft. Since the plans for all of these planes belong to the government, they are allowed to dictate on what stays and what goes. They made Curtiss-Wright remove this scoop because on the Ohio airstrip it works great but lets face reality. When at war, we'll drop some tanks and dozers and plow an airstrip somewhere. Now we have a dirt runway and the props and wheels kick up rocks and debris and send them through the cooling system putting holes in the radiators, not good !! Redesign it !!!
Look at the P51, same design, but this aircraft went into production well after the 1st P40 and the P51 was able to have this cooling system stay.

There is many other issues between these 2 planes and would probably PO some people so I won't get into that here. The bottom line is that both of these GREAT planes did there job.
I'm just trying to find some info or someone that either knew my Grandfather or flew this aircraft back then. I think all WWII Vets don't get the recognition they deserve and would be honored to speak with one.

Thank you,

Maybe pitlane could shed some light on the P 40b/c of the AVG. Allegedly the 100 engines were carefully assembled from rejected leftovers and put out 100 to 200 hundred more hp than standard.
I knew Bill McGarry of the AVG very well.
After the war he attended Loyola Law School in L.A. and became a lawyer with the federal government. When he retired he moved to Hemet where he died.
He is buried in Holy Cross Cemetary on Slauson Blvd in L.A. or is it Culver City very near the old Hughes airfield and Loyola University.

Shortround6 said:

Which P-40?

The -39 engines in D's and E's were rated at 1150HP.
The -73 engines in the K's were rated at 1325HP.
The -81,-99 and -115 engines in the M's and N's were rated at 1200HP.

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Sorry, you're right.

Elvis

fibus said:

Maybe pitlane could shed some light on the P 40b/c of the AVG. Allegedly the 100 engines were carefully assembled from rejected leftovers and put out 100 to 200 hundred more hp than standard.

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Well, "Vee's For Victory" goes along with the first part. Not so sure about the second part. THe AVG ws using higher boost pressures than USAAF book figures called for so they were getting more power but so were some other units that used the early P-40s. The AVG's hand built engines might have stood up to the extra power better than the British contract engines though

"Hand built" often entails a practice called "Blueprinting".
This is simply checking all the parts used to build an engine against the manufacturers specs and choosing those parts that spec out in such a way that the engine will give the best performance and reliability.
This plus careful tuning can often unlock "hidden" power that a normal "assembly line" engine might not exhibit.
This could partly explain why the Brits were able to successfully push those engines harder than they were (supposedly) able to handle.


Elvis

evangilder said:

Somewhere I have a photo of P-47s on the deck of a carrier in the Pacific. They did that to get them to where they were going as well.

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http://www.ww2aircraft.net/forum/aviation/p-47-carrier-capable-13506.html

These P47's took off of the escort carriers (probably in a lightly loaded config) and flew to nearby Saipan.

Elvis said:

"Hand built" often entails a practice called "Blueprinting".
This is simply checking all the parts used to build an engine against the manufacturers specs and choosing those parts that spec out in such a way that the engine will give the best performance and reliability.
This plus careful tuning can often unlock "hidden" power that a normal "assembly line" engine might not exhibit.
This could partly explain why the Brits were able to successfully push those engines harder than they were (supposedly) able to handle.
Elvis

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While blueprinting can unlock "hidden" power in production car engines I would doubt that aircraft engines were anywhere as sloppy car engines to begin with.

Since both the British and the AVG sometimes pushed these engines to 58" of boost (and even 62" at 3200rpm) I think we can see were the "extra" power came from. THe AVG engines might have stood up to it better though

Some of the AVG parts were not simply "checked" but were actually remanufactured or modified from parts that DID NOT meet original specifications. THE AVG engines were assembled in a seperate building so there was no chance that these "reject" parts would end up in an American or British engine by mistake.

fibus , I never heard of any rejected engines going in these planes but what Elvis says maybe true and was planned that way.
It could be that these engines could have been on the first run on the assembly line with minor flaws and put into airplane that had the same minor flaws as well. Thus giving a semi hand build plane and knowing they would be more superior than the production ones. I'm just guessing here. Help

Shortround6 said:

While blueprinting can unlock "hidden" power in production car engines I would doubt that aircraft engines were anywhere as sloppy car engines to begin with.

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My uncle was a Merlin mechanic with 411 RCAF squadron during WWII. One story I remember him telling was how surprised he was at the loose tolerances on the Merlins compared to the heavy equipment engines (diesel ?) that he was used to working on.
Not a quantitative anecdote I know, but I always found the story interesting.

Pitlane:
According to "Vee's for Victory" THe Engines for the AVG were not reject engines. The British released 100 airframes from one of their production contracts to the Chinese but it was without engines. The Chinese goverment had to buy the engines from Allison. Allison got permission to sell engines to the Chinese but only if it didn't interfear with US and British delieveries. Allison was working almost flat out to produce engines and didn't have spare production capacity but did have a a whole lot of parts that hadn't passed US or British inspection standards. A seperate "production" line was set up and these parts were reworked/modified and assembled into complete engines. THe serial numbers are all over the place although later engines in the 150 engine group do show some groups of consecutive numbers.
The compleate story of these engines may never be fully known but what is known is an interesting story and together with the use and maintainence of the these engines in the China theater makes an interesting read. There are also conflicting statements by peaple who were there so that a definiative statement as to how these engines were used is hard to make.
I suggest anyone who is interested read the book as this "chapter" is a number of pages long.

claidemore;

I rather doubt that diesel engines were that sloppy either. Somethng else to consider is that clearances change as engines heat up. That famous diesel clatter when they are cold.
Aircraft engines being mostly alumininium have a greater co-effiecent of expansion than an iron engine would and considering their size compared to a car engine might use a different tollerance.

Rolls-Royce found that thier intial recomendations for valve tappet clearance were in error. The .020 used for both intake and exhaust was thought to close up as the engine got hot. it did on the exhaust side but the clearance actually got bigger on intake side and later engines change to .010 on the intake valves.
R-R did allow over boring an engine to elimate a step at the top of a cylinder but fitting oversized pistons was only alowed after the war and only for a brief period of time. cylinders were to be plated when possable and reground to bring then into spec.

This is really good stuff in my opinion. It all rings true and now with the subject of allison engines so far away in time we will never know the complete truth.
One man I knew was an aeronautical engineer that worked at Wright during WW2 and had the assignment to inspect the manufacturing practices at subcontractors of aeronautical engines including the Allison. He was astounded, for instance, to see good connecting rods dropped into barrels or fitted with metal hammers.
Of course rubber mallets should be used and dropping rods atop another leads to nicks which can lead to failure of the part.
My conclusion about the Tomahawk is it was superior to the JAAF fixed wheel fighter aircraft it encountered and below 10,000 was equal to early Me/Bf 109's.
Both airplanes lacked good harmony of controls.
Coping with the Oscar and the Zero would take some care.
Tex Hill always considered the P 40 equal to Japanese aircraft and better in some ways but had to be used with correct tactics.

In the early 40's Col. Chennault came to Curtiss in Buffalo to look at the P-40s with my Grandfather. Bill Pawley, president of the Intercontinent Corp. had meet with the VP of Curtiss, Burdette Wright and some others. The US government was having Curtiss divert "100" P-40s from the English contract to China. They had engines in them.

Hi guys!

New kid on the block here. Just fan of aircraft, would have tried to be a pilot or something aircraft-related, but since childhood I was as blind as a bat. And no radar.

Good pieces of info from some of you, and I'd like to see those pics of the "naval" P-51.

About the P-40, I believe that it would hardly be improved. It was based on a pre-war design, it had some drawbacks and qualities, but on WW II the industrial factor weighted a lot. As soon as someone came up with airplanes using new concepts, and/or easier to produce, the P-40 would be relegated to "secondary tasks".

That's basically what I think that happened to the Hurricane: reliable, tough, able to face the more advanced BF-109... but if you compare Hawker's Fury and Hurricane, you see that the Hurricane is a Fury with a new engine, canopy, and a wing removed.

The P-40 was not so outdated as the Hurricane, but the principle is the same: many airplanes based on early-30s concepts were not able to keep up with the new models, the better ones survived, even if "only" as all-round workhorses.

Cheers

Shortround6 said:

While blueprinting can unlock "hidden" power in production car engines I would doubt that aircraft engines were anywhere as sloppy car engines to begin with.

Since both the British and the AVG sometimes pushed these engines to 58" of boost (and even 62" at 3200rpm) I think we can see were the "extra" power came from. THe AVG engines might have stood up to it better though

Some of the AVG parts were not simply "checked" but were actually remanufactured or modified from parts that DID NOT meet original specifications. THE AVG engines were assembled in a seperate building so there was no chance that these "reject" parts would end up in an American or British engine by mistake.

Click to expand...

Shortround6 said:

I rather doubt that diesel engines were that sloppy either. Somethng else to consider is that clearances change as engines heat up. That famous diesel clatter when they are cold.
Aircraft engines being mostly alumininium have a greater co-effiecent of expansion than an iron engine would and considering their size compared to a car engine might use a different tollerance.

Rolls-Royce found that thier intial recomendations for valve tappet clearance were in error. The .020 used for both intake and exhaust was thought to close up as the engine got hot. it did on the exhaust side but the clearance actually got bigger on intake side and later engines change to .010 on the intake valves.
R-R did allow over boring an engine to elimate a step at the top of a cylinder but fitting oversized pistons was only alowed after the war and only for a brief period of time. cylinders were to be plated when possable and reground to bring then into spec.

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Hey Shortround6, pull down your skirt, your inexperience is showing.

An engine is spec'd so that it will reliabily perform the task for which it was designed, regardless of the inginition system.
Yes, the Brits gain in performance is directly due to the increase of pressurization of the cylinders, but if you know you're going to do that, then you want to make sure the tolerances of the engine's affected parts are "spot-on", not just "close enough".
This is why they were "hand built" and why they were blueprinted.
Why else be so careful about assembly, if you weren't going to take the time to check each and every part.
Large rocker arm clearances are an indication that the engine's builder forsees the engine operating at high cylinder tempretures for an abnormally long period of time. This means the metal parts will expand to the point that they will exceed the normal clearances, so the manufacturer/builder allows for the prolonged heat by increasing the gap.
However, actual practice can sometimes show this is unneccesary and will thus rescind that spec and return either to the normal spec, or a lessened gap that may still be greater than the normal spec.
"Diesel Clatter" has nothing to do with the moving parts of the engine.
Its a condition commonly referred to as "engine knock" and it never does go away, or even lessen.
This condition exists in a diesel engine because it is not a "spark ignition" engine.
Instead, it compresses the air so tightly, it heats up to the point to where it can actually burn fuel, when atomized.
The same condition exists when a spark ignition engine "knocks". The air in the cylinder is actually hot enough to burn the a/f mixture after the intake valve has closed and the piston has begun to compress the mixture, but before the spark goes off.
Cylinder pressure in a spark ignition engine typically runs in the 90-150 psi range, but in a diesel engine, it can exceed 400 psi (thus the astronomical c.r.'s).
This puts a great increase in the load a diesel engine sees, and why those engines tend to be built a lot heavier than a non-diesel engine.



Elvis

PitLane said:

In the early 40's Col. Chennault came to Curtiss in Buffalo to look at the P-40s with my Grandfather. Bill Pawley, president of the Intercontinent Corp. had meet with the VP of Curtiss, Burdette Wright and some others. The US government was having Curtiss divert "100" P-40s from the English contract to China. They had engines in them.

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There was quite bit of finagleing going on with some of those contracts. The US was quite willing at times to give up some of it's "slots" in a production run in return for planes of a later model to be delivered at a later date. THe airframe manufacturer did not buy the engines from the aircraft engine makers. THe goverment bought the engines and had them shipped to the aircraft factory where they were fitted before the complete plane was delivered.
SO, yes the planes would have been delievered with engines (and spares sent along crated) but how the engines were paid for or how the engines came to be during production runs might be different than what appears at first glance. Please note that China didn't get into the lend lease act until April of 1941 so again some finagling was needed to cover contracts.