Which country designed the best engines for WWII?

ChrisMcD said:

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Development of Aircraft Engines / Aviation Fuels: Two Studies of Relations between Gov't and Industry

Schlaifer, Robert; Heron, S. D.
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Online here: link

University of California comes through again...

What is the other Sam Heron one?
History of the aircraft piston engines ; a brief outline
Catalog Record: History of the aircraft piston engines ; a... | Hathi Trust Digital Library
Is that available online as well?

It is there but it copyright protected, so you can search but not download the whole thing.

It is a very brief overview of a lot of things.

Chapters include
Early engines, from Wright to Hispano V-8 in 13 pages.
Curtiss D-12, 2 pages
Rolls Royce R, 2 pages.
"AIr Cooled engine development in general" (actual chapter title) 10 pages.
and so on chapter XII for instance " Fuels for Spark Ignition engines" is 10 pages and covers WW I to about 1959/60
BTW the book is about 5 1/2 inches by 8 1/2 inches so there isn't a lot on each page.

If you can get it cheap, fine, but not really a good resource on it's own.

Yes but there are over 180 pages on the WWII jet engines and over 150 pages on development of high octane aviation fuels.

I think we are talking about different books.

Development of Aircraft Engines / Aviation Fuels: Two Studies of Relations between Gov't and Industry Is
two books published together. One of roughly 540 pages on aircraft engines by Robert Schlaifer and the 2nd one on aviation fuels of about 160 pages by S. D. Heron.

S.D. Heron's later book "History of the aircraft piston engine" is the small one.

Heron also wrote a "book" for the US Air Force and US Navy titled "Aviation Fuels and their effects on engine performance" of 145 pages. It is listed as NAVAER-06-5-501 and USAF T. O. No. 06-5-4
This is usually paperback and 8 1/2 by 11 in size. It is much more technical in nature than the other two rather than a history.

Hello SR6
Yes you are right, i was talking about the combo. Sorry for the misunderstanding.

Juha

Great! I believe Tomo may already have this one.

No - I have only this one: Development of Aircraft Engines / Aviation Fuels: Two Studies of Relations between Gov't and Industry by Schlaifer, Robert; Heron, S. D.: Harvard Business School Hardcover - Henry Knox Book Company
In a not-so-official format

One book I can recommend is
Aircraft Power Plants by Arthur P. Fraas (1943)

Amazon has one (used) for $10.00. Not a history book of engines but more a textbook on basic engine principles but biased to aircraft engines. Lots of interesting charts and formulas. Explains why supercharged aircraft engines operate somewhat differently than car engines and has chapters on various systems.
For the price it is tough to beat.

Gnomey said:

Yep. All the major countries had good engines with the Germans and Americans having good rotaries and the British having a good inline. For me I voted for Britain because of the Merlin among others with the US and Germany very close behind.

Can someone change the England in the poll to Britain (or UK)...

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Radials, not rotaries. They were called "rotaries" because the crankshaft was stationary and the engine block spun around; their heyday ended about 1918. Radials had the crankshaft move around, and the cylinders stay still.

Italy had some promising, high-powered engines early in the war, but didn't have the resources to get them working. Britain had some excellent radials from Bristol.

renrich said:

Lets see, the PW R2800 powered the P47, F4U, F6F, B26, A26, C46, too many to enumerate. Smaller PWs powered B24, etc. Wright Cyclones powered a number of attack planes as well as B17s. Seems like US has big edge if only radials considered. British had RR Merlins which powered Spits, Hurris, Lancasters, etc. Bristol radials. Germany had DB inlines which powered BFs and several med. bombers and BMW radials in FWs etc. What hurts US is no really successful inline engines. Had to use RR in fighters and PT boats. The fine radials they built offset some but tough call.

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PT Boats used Packard engines. The only reason no in-lines hurt the US is that some army general thought that inlines made planes faster. Since the invention of the NACA cowling, that wasn't true. Check out zero-lift drag coefficients.

swampyankee said:

Italy had some promising, high-powered engines early in the war, but didn't have the resources to get them working. Britain had some excellent radials from Bristol.

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Unfortunately for the Italians they were pretty much stuck with 87 octane fuel which certainly limited development potential. A number of the pre-war engines were biased towards making a good power to weight ratio with 87 octane fuel which generally meant large displacement engines operating at low rpm that were light in weight. Once started down that path it is very hard to change.
For instance Fiat had the A 80 engine, an 18 cylinder two row radial of 2789 cu in displacement. However, instead of being a rival to the P & W R-2800 it weighed just over 2/3rds as much (1600lbs vs 2300lbs) and as a consequence was limited to 2200rpm instead of the 2600-2700 rpm of early R-2800s, boost is unknown (to me any way) but the engine was rated at 1200hp for take-off using a supercharger gear close to the R-2800 and having a critical altitude of 6,600ft.
Most of the other Italian 18 cylinder radials were pretty much of kind, The Alfa 135 was essentially two Bristol Mercury's but that gave a 2940 cu in engine weighing 2094lbs running at 2400rpm. Piaggio started with the P.XII which was 3234 cu in at 1874lbs running at 2100rpm.
resources to get them "working" would entail considerable weight gain to beef them up to run at higher rpm, given that with 87 octane fuel they couldn't increase boost much.

swampyankee said:

The only reason no in-lines hurt the US is that some army general thought that inlines made planes faster. Since the invention of the NACA cowling, that wasn't true. Check out zero-lift drag coefficients.

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Actually it was true. Too often we are not comparing like to like. Trying to compare airframe 'A' with a radial to airplane 'B' with an inline often includes way more variables than just the engine installations.
We need to compare the same airframe using the types of engine in question. The P-36 vs P-40 figures are very instructive.

We also need to remember that both the NACA cowling and the liquid cooled engines were both evolving. While the difference was sometimes closed up it often widened again and went through a number of cycles in just 10-15 years.
The NACA cowling for instance was countered in the early/mid 30s by the adoption of glycol coolant which allowed for smaller/lower drag radiators.
The NACA cowl was also evolving it took 5-7 years before adjustable exit flaps came into somewhat common use. Before that an NACA cowl, while a considerable improvement over either no cowl or even a Townend ring was fixed. If sized correctly for good cooling in a climb it was still higher drag than desirable in level flight.
The emphasis on the cowl also ignores the engine makers almost constant battle to increase the number of sq in of fin area per sq in of cylinder barrel wall or cylinder head area.
1920s Wright J-5

late 20s Wright R-1750

late model R-1820

fins on the barrel are very close space sheet metal roll into groves machined in the wall.
Much more cooling was obtained from the same mass airflow or air through the cowl with the better finning.
Early NACA cowls had no baffling between cylinders or to direct airflow inside the cowl.
Granted it didn't take a whole lot to come come close in drag to some of the early liquid cooled installations.

Stan Miley, in one of his articles, noted that the zero-lift drag coefficient of WW2-era fighter aircraft with liquid or air-cooled engines is pretty much indistinguishable, although the P-51 is an outlier with a very low zero-lift drag coefficient (about 0.017); the Corsair was about 0.023, and the Bf109 (at least one mark) is at 0.029 (it's an outlier, balancing out the P-51); most fighters, whether running radials, V-12s, or H-24's ran from 0.022 to 0.024.

Typically, cooling drag is a major component (as much as 25%) of a high-powered aircraft's zero-lift drag, and good cooling system design is hard, probably harder on an air-cooled engine than a liquid cooled one. The engineers at North American did an incredibly good job with the cooling system of the P-51; most cooling systems weren't as well designed,

swampyankee said:

off hand (there are probably others) about the only fighter aircraft to be in near-identical air-cooled and liquid-cooled variants are the FW190 (almost certainly Germany's best fighter) and the P-36 and P-40.

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Something is off somewhere then because they figured that a P-36 had 22% more drag than a P-40.

This is borne out by various tests done on the P-36 and P-40 aircraft like one testing "blisters" on the wing leading edge of the P-40 where power at 15,000 ft varied from 950hp down to 700hp with speed using 700hp being 298mph without the blisters and 294mph with. Speed for a P-36 during propeller tests was 292-295mph using 845-850hp at 15,000ft. or basically needing 20% more power to go the same speed.
A P-40B was rated at 286mph at 15,000ft using 600hp and 310mph using 720hp at 15,000ft for cruising.
The P-36B with different supercharger gears was good for 316-317.5mph depending on paint at 17,000ft using 950hp.
A P-40B using 2600rpm (920hp) at 15,000ft could do 331.5mph in the slightly thicker air.

Granted the P-40 had the benefit of exhaust thrust while the P-36 did not but the exhaust thrust from cruise power is a lot less than the thrust at full power. P-40 at 720hp cruise was burning 57 gallons an hour being leaned out.

P-40 power ratings are estimates from power curves done on the ground. Power levels for the P-36 are from torque meters on the engine in flight.

And again cowls and air cooling ( and they had to slow the air through the cowl and cooling fins down on the air cooled engines) were a moving "target" as it was figured that the P-40 test hack the P & W fitted a two stage supercharged R-1830 to ( a version of the engine in a F4F) had 8% more drag than a P-40 (it also made better use of exhaust thrust than a standard P-36) but that was in 1942 not 1939.

swampyankee said:

Stan Miley, in one of his articles, noted that the zero-lift drag coefficient of WW2-era fighter aircraft with liquid or air-cooled engines is pretty much indistinguishable, although the P-51 is an outlier with a very low zero-lift drag coefficient (about 0.017); the Corsair was about 0.023, and the Bf109 (at least one mark) is at 0.029 (it's an outlier, balancing out the P-51); most fighters, whether running radials, V-12s, or H-24's ran from 0.022 to 0.024.
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The most streamlined marks of Bf 109, like the Bf 109F4, were with Cd0=0.023, per Messerschmitt data (link; lower left corner of the table as 'Schnellflug Cw' value).
Cd0 of the Fw-190A-8 was 0,0265, of the 190D-9 was 0.0243, per Focke wulf data (link; divide the 'Schnellflug Cw0' value with 'Fluegelflaeche' value). The earlier marks of the 190A were a bit more streamlined due not having the bulged heavy MG installation. With that figure of 0.0265 in mind, the F4U at 0.023 looks fishy, though I Know there were two tables floatng around that claimed such a low Cd0.

Interestingly enough, the 'America's hundred thousand' book lists Cd0 for some US fighters like this:
- P-39 0.0217
- P-63 0.0203
- P-40F 0.0242
- F2A 0.0300
- P-47 0,0217 in one table, 0.0251 in another
- F6F 0.0272
- F4U 0.0267
- P-51-D 0.0176
- F4F-4 0.0253

You mean 0.0267, not 0.267, for the F4U - and 0.0253, not 0.253, for the F4F-4?

Yes, indeed, I'll edit the post.

tomo pauk said:

The most streamlined marks of Bf 109, like the Bf 109F4, were with Cd0=0.023, per Messerschmitt data (link; lower left corner of the table as 'Schnellflug Cw' value).
Cd0 of the Fw-190A-8 was 0,0265, of the 190D-9 was 0.0243, per Focke wulf data (link; divide the 'Schnellflug Cw0' value with 'Fluegelflaeche' value). The earlier marks of the 190A were a bit more streamlined due not having the bulged heavy MG installation. With that figure of 0.0265 in mind, the F4U at 0.023 looks fishy, though I Know there were two tables floatng around that claimed such a low Cd0.

Interestingly enough, the 'America's hundred thousand' book lists Cd0 for some US fighters like this:
- P-39 0.0217
- P-63 0.0203
- P-40F 0.0242
- F2A 0.0300
- P-47 0,0217 in one table, 0.0251 in another
- F6F 0.0272
- F4U 0.0267
- P-51-D 0.0176
- F4F-4 0.0253

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From https://history.nasa.gov/SP-468/ch5-3.htm, I found 0.0211 for the Hellcat and 0.0163 for the Mustang. I think allthis proves is that it's not easy to find Cd0 values on the Web. I have access to a university library; they may have AIAA journals.