Which country designed the best engines for WWII?

[Shortround6]

Part of the problem with the co-efficient of drag numbers is that they vary depending on who was doing the test or where.
Unless done in the same wind tunnel under the same conditions you are going to get a lot of variation even in the same airplane. You can get some variation between wind tunnel test/s and actual flight tests.

Conditions are important as very few of these secondary sources really give the conditions. One chapter in AHT simply says they are the zero lift drag co-efficient at moderate speeds.
Same moderate speed for all US aircraft? Same moderate speed for all allied aircraft? Same moderate speed for allied and axis aircraft?
Surface prep of aircraft in question?

When it comes to the drag of air cooled radials vs Liquid cooled in-lines I would really only consider data from air-frames that used both engines like the P-36/P-40, Hawker Tempest, Kawasaki Ki-61/Ki 100, Lagg-3/La-5? and the like. Even planes like the Macchi 200--202 have differences in the fuselage that would alter the results.
Both liquid cooled and air cooled engines also changed radiator set-ups or engine cowls/baffling on the same aircraft at times making comparisons a bit more difficult.

 

[tomo pauk]

The British came out with a table, that lists Cd0 among other stuff. FWIW: link to the thread in this site.

 

[swampyankee]

Since I've seen fairly considerable spreads in Cd,cl=0​ of 10% or more. Here are some error sources:

• Commonwealth and US sources use different methods of calculating wing area. I believe the Germans and French used a method different from the English speaking world.
• Minor differences in fit can make significant changes in Cd,cl=0​.
  
• Differences in assumptions about span efficiency will affect Cd,cl=0​: a low estimate for span efficiency will reduce the value for Cd,cl=0​

Even well-respected wind tunnels produce significantly different results; I've reduced wind tunnel data and I've seen the differences between the various NASA tunnels, plus those of the NRDC and OSU. Flight test data are less certain, and different countries have different data standards.

 

[Shortround6]

I would like to make a couple of comments that relate to posts several pages back.

1. Not all radials can run for very long with cylinders missing. There are a number of instances of R-2800s doing it. Less Stories of other P & W engines ? (B-24s might have a few stores?), Wright may have a few but just not as well publicized? I doubt that Gnome-Rhones could do it. They had enough trouble with 2 bearing crankshafts without taking out one or more cylinders. The Russian M-88 clone falls in here. Italian or Japanese engines have any reports of doing it?
2. A number of Allisons came home with bullet holes in the engine, perhaps not in the cooling passages? Holes in gear cases though.

3. Using post war commercial engines to try to prove anything about durability/reliability of war time engines is bogus.
ALL P & W post war commercial R-2800s were "C" series engines and shared no common parts with wartime military engines except the P-47M & N, ( and built but not issued to combat area F8Fs). Post war commercial use of "B" series engines was pretty much limited to surplus C-46s converted for civil use.
Some holds true for the Bristol Hercules and to some extent the Centaurus. Post war Commercial Hercules engines used a different crankcase, crankshaft (bigger bearings) and new cylinder heads at least.
Post war Commercial Merlins were the 100 Series (Commercial engines got numbers in the 600 and 700 range).

 

[ChrisMcD]

Not all radials can run for very long with cylinders missing. T

Just to add to the list of "tough" radials - the Bristol Perseus (half a Hercules) gets a creditable mention for having it's cylinder head shot off and getting it's pilot home.
http://dinger.byethost5.com/Dunkirk.htm?i=1
about half way down - 31st of May!

I think the Skua gets a poor deal. First FAA aircraft to shoot down a German plane in WWII, First dive bomber to sink a major warship (Konigsberg) and a good showing at Dunkirk

 

[tomo pauk]

Perseus was a 9 cyl radial, Herc was 14 cyl
Thanks for the link.

 

[ChrisMcD]

Perseus was a 9 cyl radial, Herc was 14 cyl
Thanks for the link.

AFAIK many manufacturers tended to use the single row cylinders, but go for a smaller number on their first twin row versions (I'm thinking Wasp and Twin Wasp). You could the argue that the Centaurus was effectively the 18 cylinder version - albeit with a longer stroke (and again - Cyclone, Twin-Cyclone, Duplex-Cyclone).

 

[Shortround6]

Actually the Wasp (R-1340) used 5.75 X 5.75 cylinders while the Twin Wasp (R-1830) used 5.50 X 5.50 cylinders. The Advanced Twin Wasp (R-2000) used 5.75 X 5.50 cylinders (one of the few over square aircraft engines) while the Double Wasp (R-2800 used 5.75 X 6.00 cylinders. As did the Wasp Major (R-4360) and the Twin Wasp R-2180.
You really can't tell the players without a score card
Just to keep everybody on the right path the Wasp Junior (R985) used 5.1875 X 5.1875 Cylinders as did the Twin-Wasp Junior (R-1535)
The Hornet A used 6.125 X 6.375 Cylinders While the Twin Hornet used 5.75 X 6.00 cylinders.

 

[swampyankee]

The ability for an engine to continue operation after having a cylinder blasted off was very unlikely to be a design goal, just a happy accident.

As for reliability and serviceability, one of the reasons turbines succeeded is that even early turbines, like the Avons on the Comet 2, had lower routine maintenance needs than piston engines. No liquid-cooled engines, except the Merlin, had any kind of post-war commercial success, which probably is more a comment aboutthe relative operating expense of liquid-cooled vs air-cooled engines than anything else.

 

[tomo pauk]

There were many factors for the post-war commercial success. 1st was the surplus of transport aircraft, mostly C-47, that were powered by radial engines. Nobody was in shopping spree for new aircraft, unles those can provide a major improvement over DC-3/C-47. Those new aircraft were using engines providing over 2000 HP for take off, and there was no such V12 engines in main producing country - USA - thus leaving them with either R-2800 or R-3350.
Germany, the main country that was big in big V12s was no issue post war for obvious reasons. UK was satisfied with Merlins, looking with one eye to the jet engines.

 

[Shortround6]

One reason for the commercial "success" of the Merlin (use in commercial aircraft) was the absolutely crappy state of the British economy post WW II. This extended to the commonwealth. Imports were regulated/heavily taxed while exports were strongly encouraged. A British or commonwealth company could buy British cheaper than importing American aircraft/engines.

I am not sure that Avons count as early turbines. They didn't go into service with the Comet until 1953/54 which leaves 8-9 years of Piston powered airliners. In the 1940s (46-49) very few jet engines had an overhaul life suitable for commercial use and fuel consumption was horrendous.

 

[swampyankee]

There were many factors for the post-war commercial success. 1st was the surplus of transport aircraft, mostly C-47, that were powered by radial engines. Nobody was in shopping spree for new aircraft, unles those can provide a major improvement over DC-3/C-47. Those new aircraft were using engines providing over 2000 HP for take off, and there was no such V12 engines in main producing country - USA - thus leaving them with either R-2800 or R-3350.
Germany, the main country that was big in big V12s was no issue post war for obvious reasons. UK was satisfied with Merlins, looking with one eye to the jet engines.

One other reason is that pre-war Germany had relatively little commercial aviation, and that was [probably] heavily subsidized and largely subordinated to government or quasi-military purposes: the German aircraft engine industry existed largely for the Luftwaffe. Even the British and French had relatively small commercial aviation pre-war, with the long-range aviation basically existing for luxury service to imperial possessions. All of these countries were physically small, and all had excellent rail networks, in contrast to the US. Britain, France, and Germany together would probably (I've not done the math) fit between Boston, Philadelphia, and Chicago. The US had major commercial centers on both coasts, and while the trans-continental rail lines did exist (and were quite important; a train with a 6-man crew could move more freight cross country than well over 200 trucks, each with a driver), they also took quite a while to get across the continent. Planes were enough quicker to be worth a premium (and, of course, aviation was subsidized, mostly through air mail contracts until the late 1970s or early 1980s), and this led to the growth of a large and robust civil aviation sector, with companies to supply it. The airlines were all run by businessmen, intent on maximizing profit (or at least minimizing cost), and the larger airlines had the clout to have C-W or P&WA build any engines they desired. You can see some of this post-war, when commercial demands have been pushing turbofan engine technology quite hard; the same sort of commercial pressure was felt by C-W and P&WA before WW2. Corresponding commercial pressure did not exist elsewhere; the only country which could have developed a strong commercial aviation industry was the USSR, and its air transport sector was certainly not commercial, and was even more in service to government desires than Germany's.

In other words, for-profit commercial users didn't want liquid-cooled V-12s before WW2. Even countries with quite good V-12s saw their commercial aviation fleet transition to radials before ww2. What 1930s airliners were built with V-12s? I'm guessing very few, if any.

 

[ChrisMcD]

AFAIK most of the successful British commercial airliners of the 50's were also radial powered.

Radials - Vickers Viking, Handley Page Hermes/Hastings, Airspeed Ambassador, Bristol Freighter.

Inline - Avro York, Avro Tudor. I've read that Rolls spent a fortune developing the commercial Merlin, but it was not really a great success apart from the Canadair North Star

 

[tomo pauk]

After the war, the 27L Merlin (or V-1710) will be hard pressed to compete with 38L Hercules, let alone bigger engines, when it is about take-off power. Talk 1600 HP vs. 2000 HP, give or take; makes 6400 HP vs. 8000 HP in a four-engined A/C. In that light, the benefits Merlin offered in military aircraft (streamlining, capability for high peak power) did not mattered, especially since it took many bells & whistles for the Merlin to beat 2000 HP mark (2-stage S/C, intercooling, sometimes water injection) that drove the cost of purchase and maintenance up, and still those 2000+ HP were not available for take off.
Sure enough, Merlin vs. Centaurus is a loosing proposal here.
BTW - you can also bet that Bristol will use their engine on their A/C if they can help it

 

[stona]

One other reason is that pre-war Germany had relatively little commercial aviation, and that was [probably] heavily subsidized and largely subordinated to government or quasi-military purposes: the German aircraft engine industry existed largely for the Luftwaffe.

In 1918 the German aviation industry comprised 35 aircraft plants and 26 engine plants. It had built 44,000 aircraft and 48,000 engines during WW1. Considering that the German Army had just 218 aircraft and 12 airships in 1914 and the Navy planned a total of 36 aircraft by 1919 this is a remarkable expansion.
The problem is that Germany lost that war! The Treaty of Versailles prohibited the manufacture of aircraft, engines or equipment. It also required the Germans to hand over to the Allies, or destroy, 15,714 fighters and bombers, 27,757 aero engines and sixteen airships. Furthermore, one million square metres of aircraft hangarage was dismantled and all military flying equipment, aircraft and training programmes were prohibited.
By 1920 the number of German aircraft manufacturers had dropped to 7 and just 95 aircraft were produced that year (74 by Junkers).
By 9th February 1922 these terms had been met and an official three month ban on ALL aircraft began. Following that civil construction would be allowed, but the performance of any new civil aircraft was limited. Maximum speed to 170 kph, operational ceiling 4,000m, range 300 Km and maximum payload 600 Kg. This year a total of 47 aircraft were produced in Germany. This number, almost entirely small sporting and civil aircraft, increased to 406 by 1925.
The restrictions on German aircraft production were not alleviated until the Paris Air Agreement on 26th May 1926. This did allow the Germans to start to join in with the evolution of aviation technology already underway in other Western powers, but they came late to the table. It also led to a fall in aircraft production as larger and more sophisticated designs were developed. It took until 1928 before the pre-agreement levels were attained, 409 aircraft produced in 16 plants.
The economic crisis of 1929 resulted in the collapse of several aviation firms, despite subsidies and secret orders for military aircraft.
Production fell consistently until 1932 when just 231 aircraft were produced in Germany, 85 of these were the Klemm sports planes.
In February 1932 Felmy submitted his study for the creation of an Air Force with just 720 aircraft, but even this seemed a large and optimistic total at the time.
On 30th January 1933 Hitler was appointed Reich Chancellor. On 3rd February Goering was appointed to head a Reich Commission for Aviation, which would lead, on 27th April, to the creation of the RLM and hence the Luftwaffe.
Given the state of the industry which the Nazis inherited it is clear that they started off on the back foot. It is not cool or fashionable to point out positive achievements of such a regime in these politically correct days, but the fact that the Luftwaffe existed, equipped as it was, just seven years later is remarkable.

Cheers

Steve

 

[Shortround6]

What is equally remarkable (but helps explain the Luftwaffe of 1939/40) was from that starting point the Germans building several thousand "1st generation" warplanes before switching to the well known planes they went to war with (2nd generation ?).

Arado 65 & 68 fighters, He 51 fighters, Heinkel 45 & 46 recon, Dornier 11/13/23 bombers Junkers Ju 86 (around 900 built of all types)
and others.

 

[swampyankee]

In 1918 the German aviation industry comprised 35 aircraft plants and 26 engine plants. It had built 44,000 aircraft and 48,000 engines during WW1. Considering that the German Army had just 218 aircraft and 12 airships in 1914 and the Navy planned a total of 36 aircraft by 1919 this is a remarkable expansion.
The problem is that Germany lost that war! The Treaty of Versailles prohibited the manufacture of aircraft, engines or equipment. It also required the Germans to hand over to the Allies, or destroy, 15,714 fighters and bombers, 27,757 aero engines and sixteen airships. Furthermore, one million square metres of aircraft hangarage was dismantled and all military flying equipment, aircraft and training programmes were prohibited.
By 1920 the number of German aircraft manufacturers had dropped to 7 and just 95 aircraft were produced that year (74 by Junkers).
By 9th February 1922 these terms had been met and an official three month ban on ALL aircraft began. Following that civil construction would be allowed, but the performance of any new civil aircraft was limited. Maximum speed to 170 kph, operational ceiling 4,000m, range 300 Km and maximum payload 600 Kg. This year a total of 47 aircraft were produced in Germany. This number, almost entirely small sporting and civil aircraft, increased to 406 by 1925.
The restrictions on German aircraft production were not alleviated until the Paris Air Agreement on 26th May 1926. This did allow the Germans to start to join in with the evolution of aviation technology already underway in other Western powers, but they came late to the table. It also led to a fall in aircraft production as larger and more sophisticated designs were developed. It took until 1928 before the pre-agreement levels were attained, 409 aircraft produced in 16 plants.
The economic crisis of 1929 resulted in the collapse of several aviation firms, despite subsidies and secret orders for military aircraft.
Production fell consistently until 1932 when just 231 aircraft were produced in Germany, 85 of these were the Klemm sports planes.
In February 1932 Felmy submitted his study for the creation of an Air Force with just 720 aircraft, but even this seemed a large and optimistic total at the time.
On 30th January 1933 Hitler was appointed Reich Chancellor. On 3rd February Goering was appointed to head a Reich Commission for Aviation, which would lead, on 27th April, to the creation of the RLM and hence the Luftwaffe.
Given the state of the industry which the Nazis inherited it is clear that they started off on the back foot. It is not cool or fashionable to point out positive achievements of such a regime in these politically correct days, but the fact that the Luftwaffe existed, equipped as it was, just seven years later is remarkable.

Cheers

Steve

Do remember that you're comparing an aviation industry during wartime with what may occur post-war. I suspect, had aviation not been banned by Versailles (a ban that was almost immediately ignore by the Weimar government), about 90% of that production would go away. Governments, even German governments have other things to do than fund their armed forces.

 

[stona]

I suspect, had aviation not been banned by Versailles (a ban that was almost immediately ignore by the Weimar government), about 90% of that production would go away. Governments, even German governments have other things to do than fund their armed forces.

The Germans met all the requirements of the Versailles Treaty, destroying or transferring all those tens of thousands of engines and aircraft and various infrastructure. I gave the actual production numbers of aircraft in some of the interwar years that also clearly demonstrate that post WW1 German governments did not 'immediately ignore' the Treaty terms. This is another latter day myth, one I've seen repeated in supposedly reputable TV documentaries among other places.
The German government DID secretly order a small number (in the tens) of military aircraft during these years, and there was the well documented 'cooperation' with the USSR.
None of this was enough to support a meaningful aviation industry and until the Paris Agreement of 1926 no such thing existed. In 1932, before the Nazis came to power, Germany produced just 232 aircraft.

Of course governments had differing priorities, particularly after the financial crisis of 1929, but in 1923 the British Government took the decision to create a 52 squadron home defence force, aircraft for RAF overseas Commands were classified as exported. Between 1923 and 1930 Air Ministry orders averaged 646 aircraft per year. The military aircraft firms received, on average, £1.8 million from the government in this period, and an examination of their accounts shows that they could operate quite profitably at this time. In 1923 Supermarine made a £58,002 profit on £137,683 of sales. In 1927 the same numbers were £403,868 and £111,935.
There was also a healthy civil market, this was dominated by de Havilland. In 1935 de Havilland sales exceeded £1 million (£1,018,318) a huge number at the time.
In 1932, when the Germans made that paltry 232 aircraft the profits of five British manufacturers read like this. Handley Page - £8,135, Fairey - £198,510, Westland - £11,933, Armstrong Whitworth - £19,808, Napier - £17,560. With the exception of Fairey these are all much lower than in the three previous years, due to the economic climate, they are, nonetheless, still in profit. It was this that led to consolidation, the Vickers - Supermarine merger, the formation of Hawker Siddeley for examples. Comparisons with the pre-Nazi aviation industry in Germany are impossible to make. It would be like comparing a combine harvester and a horse, both have applications in agriculture but that's about it.

One 1935 pound was equivalent to five 1935 US dollars. Something that cost £1 in 1935 would cost £60-70 today.

Cheers

Steve

 

[swampyankee]

Back on track here I think the Napier Sabre was the most advanced piston engine to see service in WW2, but I think that, on the whole, the US companies Pratt & Whitney Aircraft and Curtiss-Wright designed the best large engines. I also think many people underestimate the importance of NACA to aviation throughout the world, not just in the US. They also, I think, underestimate how much international cooperation there was in aviation up until something like 1935 or so. People from NACA and its European, possibly including Soviet, and Japanese counterparts would probably be reading the same journals and attending the same national and international conferences and many were alumni of the same schools. Even now aerospace engineering is not that large of a community. I suspect all the design and analytical engineers working for all the aircraft engine companies wouldn't fill the Rose Bowl.

 

[Shortround6]

"Back on track here I think the Napier Sabre was the most advanced piston engine to see service in WW2, but I think that, on the whole, the US companies Pratt & Whitney Aircraft and Curtiss-Wright designed the best large engines."

The Napier Sabre may have been the most advanced, wither it was worth the time and money spent on it is another matter, since the answer, if it exists, has been buried since WW II. While at least some cost figures for P & W and Wright engines does surface on occasion both the Bristol and Napier sleeve valve R&D costs have remained unknown to the world at large. Somebody may be able to ferret out the cost of post war Bristol engines but since all Napier sales were to the government they may be much harder to find.
The Sabre, for all it's "advancement went exactly nowhere after the war. No commercial sales and darn little use in post war military aircraft except to complete a few existing contracts?
Now I will grant that the majority of post war P & W R-2800s difference from even the war time "C" series engines and that the post war Wright R-3350s also differeed from the majority of wartime R-3350s. Likewise post war Hercules and Centaurus engines differed form war times ones( Hercules went to main bearings with larger rollers for one thing).

AN awful lot of money and time was spent on the Sabre which wound up powering about 4500-4600 airplanes, almost all being single engine.