Japanese Design Philosophy

[JoblinTheGoblin]

I was inspired to make this post, having heard of the exemplary record of the Ki-43, and claims that the Ki-100 had similar characteristics to more advanced aircraft like the Merlin-powered P-51 in nearly all aspects of manoeuvrability except, oddly enough, level flight speed, and maybe some other metric I haven't mentioned here.

Given the apparent success of such low performance designs, were there any other great powers that could have adopted a similar aircraft design philosophy to Japan's at any point in the interwar period, and adhered to that school throughout the war or some alternate counterpart, that being:

- Smaller, weaker, but lighter engines for fighter aircraft.
-- Adding to this, a preference for air-cooled radial engines over liquid-cooled in-line engines.
--- If the P-51D was radial-engined, but still miraculously kept the same performance, 'Japanese Mustang' prototypes would be popping up around 1945, or if you prefer, on the drawing boards by then. (The Japanese knew of the lesser Airacobra design as early as 1942, when their situation was more favourable, hence why they copied that instead for otherwise unsuccessful prototypes). The A7M and Ki-87 took cues from the radial-engined P-47, for example.
- Emphasis on range and/or slow(er) speed manoeuvrability, for instance, larger, wider wings.
- Slower, more gradual evolution of aircraft, such as prolonging the production of obsolete or tried and true designs.
- Bombers with excessively long ranges but generally smaller bomb loads.
- Oddly advanced dive/torpedo bombers that have the ability to come close to or exceed the maximum level speeds of foreign counterparts.
- "Laminar flow", balloons, or some other similarly quirky side interest.
- Continuously issuing aircraft requirements that couldn't, or wouldn't, be met, especially maximum level speed.
- Specifying the top speed of an aircraft to be that achieved at a certain engine power that happened to be below the maximum achievable engine power at altitude, dash power, overboost, WEP, 'full power' or some other equivalent term.
- Producing aircraft that could neither exceed ~580kph nor ~640kph in level flight at altitude.
-- Testing experimental aircraft that could neither exceed ~700kph nor ~750kph in level flight at altitude.
- Gradual transition to faster German-derived jet aircraft to both compensate for faltering traditional indigenous plane designs, similar to one interpretation of late-war German design philosophy I've heard involving 'losing the horsepower race' and increased emphasis on jet aircraft designs, and to counter the coming Allied jet threat.

I have some other aspects in mind, but they're either too dismissive or too specific to Japan to include, such as every attempt at a larger or more powerful engine being unreliable for whatever reason, leading the world in useful but somewhat redundant aircraft types like high-speed, long range reconnaissance aircraft, flying boats, or floatplanes, or big, fat, noisy carrier submarines and noisy aerial torpedoes.

Italy, perhaps? Some neutral country?

Edit: Added some other teachings of the Japanese school.
Edit #2: Minor changes for clarity.
Edit #3: Removing some unverified teachings, and adding a few more in return.
Edit #4: Added yet another teaching.

 

[ThomasP]

The phenomenon you are referencing is due to a combination of things.

For Germany (after they failed to take Russia) and for Japan (after early-'43?) the war became one of logistics and attrition. If we speak in general terms, both of the Axis nations were assured to lose (barring some sort of extraordinary event) after late-1942 or early-43.

At that point, even if everything were equal in terms of tech, it becomes a case of how many aircraft with quality pilots you can put up at any given time - much more than small(ish) advances in technology and performance. Remember - with everything else being equal - in air-air combat the side with the height advantage ond/or speed advantage will have the best chance to control the fight initially. Once the aircraft are engaged in combat it becomes more a case of situational awareness and numbers. Speed will still help, but not as much, except that you can usually break off at will if the difference in speed is significant enough.

For every aircraft shot down during a maneuver dogfight where both pilots know they are fighting each other, there will be somewhere around 7 or 8 aircraft shot down when they are caught unawares - sometimes it can even be called luck such as when a pilot realizes he is in a bad situation and breaks off by diving - and passes right in front of another enemy aircraft with a pilot quick enough to pull the trigger.

Just by putting up a significant number of reasonable qualtiy airframes the Japanese (and Germans) were pretty much assured of scoring reasonable numbers of kills vs the 'superior' Allied aircraft.

The reason they did not shoot down many more Allied aircraft is that they ran out of fuel, spares, and skilled pilots.

"Quantity has a quality all on its own" and "Showing up is half the fight"

[edited slightly on 9 Apr for clarity]

 

[cammerjeff]

I agree with what ThomasP says in his post. I would add that IMO Japan had a Unique set of requirements in the late 1930's. They wanted the following characteristics for their Fighters

1-Geat memorability ( Turning ability )
2-Long Range ( for the Navy at Least )
3- Use of available Domestic engines ( preferably air cooled )

As the European Nations did not require long range fighters ( At least until you think about attacking the USSR ) they could design smaller airframes, and they some more advanced engines to choose from in the late 1930's ( at least England & Germany ) plus there seemed to be a competition for producing the world record fasted aircraft in Europe.
Japan did not have any close independent nations with an advanced aviation industry in that time frame. So long range wins out.

There were some attempts to produce lighter Fighters at the time, using lower HP engines, but they seemed to be diversions from what was actually needed. Now if you can produce a light but strong airframe, fill it with enough fuel, add self sealing fuel tanks, and some armor. Load it with 2 cannon and 2 MG's, how much slower will the results be than one designed with 25-30% more power? Will it be useful? Can you build enough of them and train enough pilots to have a meaningful numbers advantage?

Also how many of the lower powered engines can you produce vs the higher powered engines? Comparing the amount of materials and manpower needed to produce each type. If it takes almost as many man hours to make the lower HP engines, and almost the same materials, what is the advantage?

I fear you would get something like what the Italian aircraft industry became in the late 1930's.

But maybe I misunderstand your Question.

But I could be missing something also.

 

[tomo pauk]

I was inspired to make this post, having heard of the exemplary record of the Ki-43, and claims that the Ki-100 had similar characteristics to more advanced aircraft like the P-51B+ in nearly all aspects of manoeuvrability except, oddly enough, level flight speed, and maybe some other metric I haven't mentioned here.

There was probably nothing odd in P-51B+ having a much greater level flight speed than the Ki-100 - after all, Ki-100 was offering the level speed of the Spitfire I.

- Smaller, weaker, but simpler and lighter engines.
-- Adding to this, simpler designs that workers of lower skill or experience can produce more efficiently.
- Emphasis on range and/or slow(er) speed manoeuvrability, for example, larger, wider wings.
- Heavier aircraft armament, such as cannons on aircraft, 20mm or greater.
- Slower, more gradual evolution of aircraft, such as prolonging the production of obsolete or tried and true designs.
- Bombers with excessively long ranges but generally smaller bomb loads.
- Oddly advanced dive/torpedo bombers that have the ability to come close to or exceed the maximum level speeds of foreign counterparts.
- "Laminar flow", balloons, or some other similarly quirky side interest.
- Continuously issuing aircraft requirements that can't, or won't, be met, especially maximum level speed.
- Specifying the top speed of an aircraft to be that achieved at military power or similar, as opposed to take-off power at altitude, WEP or equivalent.

- Soviet union, Italy?
- The more machine tools one has, the less skillful the manpower can be - Japanese were not that efficient after all?
- Americans?
- Germans, French, Polish (for export, though) and Soviet were the 1st to introduce cannons, so any pick is good enough.
- Basically everyone?
- Americans favored long range, although their bombers were also carrying good bombloads.
- A-36A, Pe-2, Henley - all of them started out as fighters, though. Also the Fw 190 and G.55S that were supposed to carry torpedoes, although I don't think that these were ever used in that role. Re.2002 was also supposed to carry a (small) torpedo.
- Germans were the kings of quirky things.
- ?
- Take-off power at altitude was possible only with turbocharged engines. WEP and military power were American terms, perhaps not mix it with other countries?

 

[Shortround6]

Just to cover the first 4 and remembering that all aircraft is a compromise.

- Smaller, weaker, but simpler and lighter engines.

We often focus on displacement of the engines, which the aircraft designers could care less about.
Smaller and lighter means less power, which is the obvious, What is less obvious is that smaller engines often had less power density, I am referring to power per unit of frontal area. like sq ft. It also often meant less power to weight. Leaving the Japanese out of it for the moment this was the problem the Italians had. Their 840-1000hp 14 cylinder radials were lighter than the P&W R-1830 but not enough lighter. The Fiat A74 was bit smaller but the Piaggio P.XI was larger in diameter and bit lighter. Now using a 14 cylinder two row radial is about as simple as it gets. But there are a number of limits. The Piaggio P.XI was the same diameter as the P &W R-2800 so you have a problem with fuselage diameter. One way the Piaggio P.XI was so light was that they left out the center bearing on the crankshaft which limits strength and the ability to use high rpm. Which limits power.
Trying to use 9 cylinder radials runs into real problems. Each cylinder has to be large which means a large diameter engine and it also means needing to restrict rpm (piston speed) and it means problems cooling. As cylinders get larger the volume (amount of fuel burned) goes up faster than the surface area (ability to get rid of heat). Wright, the champion of high powered 9 cylinder radial, kept increasing the complexity of the size, number, depth of fins and the complexity of the manufacturing processes to make the cylinders and heads.
Similar but not identical problems for V-12s. The Hispano Suiza engines were large displacement, light but not strong enough to survive making the needed power, and in some ways easy to make (only 2 valves per cylinder) but actually not easy to manufacture. The castings, machining operations, heat treatment and tolerances needed were not easy to deal with.

-- Adding to this, simpler designs that workers of lower skill or experience can produce more efficiently.

In engine land the US invented machines/processes that hugely speeded up production for the same amount of man hours. Now the cost of the machines and the man hours to produce the machines was very expensive compared to just adding lower skilled workers but for large production it paid off. Using large numbers of semi-skilled workers to finish grind/polish air cooled cylinder head fins when you need thousands of cylinder heads per month (14 cylinder heads per engine) ?
Same for airframes. The US built tooling to speed up the production of airframe parts. Some airframes were very complicated to build. Sometimes great simplification could be done without much affect on aircraft performance. The US even on the A-20 in 1940 was building Fuselages in sections or halves and doing quite a bit of work on them where they could access the inner and outer surfaces at the same time, run wires and piping, mount control runs, etc and then joining the sections together instead of finding small workers to be contorted in strange shapes to work on fuselage (or wing) interiors. But that means larger roll around platforms, cranes, and the ability to maneuver/move large pieces on the assembly line, assuming you actually have moving assembly lines and not just a row or line of aircraft nose to tail that the workers push from one area to another.
All countries could have designed better for easier production. But a lot times they were frozen by too small initial orders. You don't speed the money for big, expensive tooling for orders in the low hundreds. You need big numbers to pay for the labor saving tooling.
You can do a lot better production design. But you need production designers and engineers and draftsmen. If you don't have enough engineers and draftsmen you don't have the manpower to help the aircraft/engine designers work on the next generation of product.

- Emphasis on range and/or slow(er) speed manoeuvrability, for example, larger, wider wings.

Range equals weight, and longer, wider wings equals drag. Every thing is a compromise.

- Heavier aircraft armament, such as cannons on aircraft, 20mm or greater.

Timing, it turns out that it took about 5-6 years to go from concept to actual large scale use of an aircraft gun (includes tooling up factory and training workers).
A lot of threads on guns in forum. 20mm guns cover a wide spectrum, with shells varying from 79 grams to over 160 grams (solid AP shot) and velocities from 600m/s to 880m/s and cycle rates from around 500rpm to 800rpm. Most guns that were on one of the range in one catagory was near the other end in another catagory.
The Russians were champs at cheap, light effective 20mm guns, but they paid for it with lower than average shell weight and lower than average durability of the guns. One might argue than the British and US spent too much on durable guns that would out last the average airframe. But the Soviets were not fighting thousands of miles away from the factories and needing to send spare guns and parts by ship.
A lot is made of the claim that the British/US 20mm was 3 times more effective than the US .50 cal. Which seems to be true. However the US and British had planes with large engines that could take the weight of the guns and ammo. That judgment is also only for the 20mm Hispano and the US .50 cal. Other countries 20mm to 12.7-13mm effevtivenss ratios may be some what different. And that is the firepower ratio. Since the 20mm Hispano gun was over twice as a heavy as the M2 .50 cal gun the effectiveness per lb of gun weight is only about double.
The Soviet 20mm ShVAK gun was about twice as effective as the 12.7mm Berezin gun both in firepower and in firepower to weight. Please note that the Soviets often limited their armament of their fighters in order to preserve performance with their low powered engines.
If you are deliberately using low powered engines you may have to stay with less powerful armament to keep performance in an acceptable area.

 

[Shortround6]

"Quantity has a quality all on its own" and "Showing up is half the fight"

US had the capacity to make a crap load of fighters. For the US there was a 2nd problem.
They had to show up for the fight. Transport the "Quantity" and it's support/logistics train 1/2 way around the world.

The Japanese problem was not quite as bad, but compared to the Germans and Soviets?
Japan to Burma or Japan to Rabaul?
Supply of spare parts, pilots, ground crew, food/fuel?

 

[ThomasP]

re

- Continuously issuing aircraft requirements that can't, or won't, be met, especially maximum level speed.

I do not think this point belongs in the description, but I am not sure as I do not have enough information on the many types of airframe the Japanese put in service vs the initial design requirements. I am only somewhat familiar with the original RFPs and design requirements for a few aircraft - given by the Japanese bureaus (Army and Navy?) responsible for laying out their wishlists.

In the cases of the Ki-43 and A6M, both airframes met or exceeded the wishlists in most or all areas. I think the H8K did also, but am not sure.

It would be nice if we could find and post the many RFPs and design requirements as they were at the times.

 

[JoblinTheGoblin]

There was probably nothing odd in P-51B+ having a much greater level flight speed than the Ki-100 - after all, Ki-100 was offering the level speed of the Spitfire I.

My point is, that from everything I've read online, in forum discussions and online encyclopaedias, the Ki-100 was, in essence, a slow P-51. Basically, Japanese aircraft were, in a sense, like uniquely slower variants of aircraft of other nations, which were not as slow.

- The more machine tools one has, the less skillful the manpower can be - Japanese were not that efficient after all?

I maybe should have phrased it differently. It's that Japanese designs were simpler for the sake of less skilled workers, eschewing more intricate, and in some cases more sophisticated, technology in the process. Aircraft with liquid-cooled engines, such as the Ki-28 or the imported A7He, were rejected for their complex engines, among their other apparent deficiencies. Another example of a design rejected for its complexity was the Ki-94I.

- Americans?

? They still had quite the fast warbirds.

- Americans favored long range, although their bombers were also carrying good bombloads.

Yep.

- A-36A, Pe-2, Henley - all of them started out as fighters, though. Also the Fw 190 and G.55S that were supposed to carry torpedoes, although I don't think that these were ever used in that role. Re.2002 was also supposed to carry a (small) torpedo.

Until now, I was unaware as to the existence of the Henley. I had forgotten about the Pe-2, though variants of some Japanese aircraft, like the D4Y, did at least come close in terms of level speed to the twin-engined bomber. If the higher end estimates of, say, the Ki-84's performance are to believed, that aircraft would have been a comparable fighter-bomber to those other fighter-bombers you listed. For pure light bomber designs, the B7A, D4Y and B6N were comparable to the Firebrand, the Helldiver, and other examples.

- Germans were the kings of quirky things.

True, though some quirky projects in particular, like jet aircraft, night vision and guided weapons, went somewhere.

- Take-off power at altitude was possible only with turbocharged engines. WEP and military power were American terms, perhaps not mix it with other countries?

How about maximum (achievable) engine power, dash power, boost(?) or some other term I may be forgetting here?

If you are deliberately using low powered engines you may have to stay with less powerful armament to keep performance in an acceptable area.

The Japanese thought differently.

- ?

I do not think this point belongs in the description, but I am not sure as I do not have enough information on the many types of airframe the Japanese put in service vs the initial design requirements. I am only somewhat familiar with the original RFPs and design requirements for a few aircraft - given by the Japanese bureaus (Army and Navy?) responsible for laying out their wishlists.

In the cases of the Ki-43 and A6M, both airframes met or exceeded the wishlists in most or all areas. I think the H8K did also, but am not sure.

Earlier on, the initial Ki-46 prototype failed to meet a 600kph requirement. The Ki-84, from all accounts, could not have achieved the 680kph the army required of it. The J5N failed to meet an Army "18-shi specification" for a 666(???) kph fighter. Neither the A7M1 or the A7M2 matched a ~639kph specified speed, a speed similar to that of a late model F6F, superceded by the formidable F8F.
Already, with the advent of later Spitfires and Merlin-powered P-51s, Ki-43 pilots were beginning to hurt for faster planes that could fly well. Where was the Japanese Mustang?

 

[Shinpachi]

If we talk about the speed only, including such an experimental model like A7M, here is J8M with 890km/h.
Combat result with a P-51 would have been like this


View: https://www.youtube.com/watch?v=c1Pi6cxiLbU&t=23s

 

[bf109xxl]

The authors clearly kept their imagination restrained. Where's the kamikaze orbital bomber? Where are the manned anti-aircraft missiles ramming into the helpless B-29? The spirit of samurai self-sacrifice is poorly conveyed. The enemy is not completely destroyed. Seems, that the tradition of composing fairy tales is going away...

 

[JoblinTheGoblin]

The authors clearly kept their imagination restrained. Where's the kamikaze orbital bomber? Where are the manned anti-aircraft missiles ramming into the helpless B-29? The spirit of samurai self-sacrifice is poorly conveyed. The enemy is not completely destroyed. Seems, that the tradition of composing fairy tales is going away...

You'll have to step further into the world of Japanese animation for such things...

View: https://youtu.be/X5vIGnk3XJ8

 

[bf109xxl]

You'll have to step further into the world of Japanese animation for such things...

View: https://youtu.be/X5vIGnk3XJ8

I always suspected there are gateways between parallel worlds. And Japan won in one of them.

 

[ThomasP]

re

Earlier on, the initial Ki-46 prototype failed to meet a 600kph requirement. The Ki-84, from all accounts, could not have achieved the 680kph the army required of it. The J5N failed to meet an Army "18-shi specification" for a 666(???) kph fighter. Neither the A7M1 or the A7M2 matched a ~639kph specified speed, a speed similar to that of a late model F6F, superceded by the formidable F8F.
Already, with the advent of later Spitfires and Merlin-powered P-51s, Ki-43 pilots were beginning to hurt for faster planes that could fly well. Where was the Japanese Mustang?

I think you are mixing two different arguments.

There is the question of why the Japanese airframes did not (could not?) meet the representative agency's speed requirements, and there is the question of why the Japanese airframes did not (could not?) match the speed of the Allied airframes.

1. The agency's requirements were what they hoped to see achieved. Hopes for aircraft performance were often dashed for various reasons - among all the combatants. The production A7M2 was supposed to do 629 km/hr (per your post 10 km/hr less than asked for?). If they had asked for 619 km/hr how would that modify your statements and how would that affect the A7M's value? Or if the US had asked for 649 km/hr of the F6F design?

2. Matching the speed of the Allied fighters might not be practical (possible?) without better fuel logistics (ie quality of fuel and quantity). Without 100/130 grade fuel it was highly unlikely that the Japanese could match the speeds of the Allied fighters and have comparable combat abilities, and without sufficient quantities of the 100/130 grade it was pointless to design aircraft that relied on it for performance. What would the potential speeds be for the Japanese aircraft you mentioned if they had had 100/130 grade fuel available during the engine and airframe development?

When you add in Japan's substantially smaller population base, substantially smaller industrial base, and substantial lack of access to natural resources (relativel to the Allies), I find it amazing that the Japanese did as well as they did. Also, don't forget that when comparing the combatants population base industrial base, and access to natural resources, you need to kind of add the US and UK together.

 

[JoblinTheGoblin]

When you add in Japan's substantially smaller population base, substantially smaller industrial base, and substantial lack of access to natural resources (relativel to the Allies), I find it amazing that the Japanese did as well as they did. Also, don't forget that when comparing the combatants population base industrial base, and access to natural resources, you need to kind of add the US and UK together.

I guess my question is, if another country faced a situation similar to Japan's, similar to what you've laid out, particularly a European or American country, how would it fare? Could the factors that influenced Japan's preference for certain aspects of performance like turn-times have occurred in another country, making it's aviation industry go down a similar path?

To summarise my original enquiry, what made Japan's aircraft different, and what would it take for said factors to emerge in another country?

But, for one of your questions, I have an answer.

If they had asked for 619 km/hr how would that modify your statements and how would that affect the A7M's value? Or if the US had asked for 649 km/hr of the F6F design?

The former scenario would not change my lack of enthusiasm regarding the A7M's performance (though I will admit, the A7M3-J Kai's looks pique my interest). I would only see it as yet another conservative design in the Japanese inventory. As for the latter scenario, it would only slightly dampen my outlook on American aircraft, as they would still have such venerable designs as the P-47, P-51, P-38 and the F4U. The F6F would have still been an effective aircraft, not to mention faster than any Japanese carrier-borne aircraft with the possible exception of the C6N Flying Limousine.

 

[ThomasP]

re

To summarise my original enquiry, what made Japan's aircraft different, and what would it take for said factors to emerge in another country?

If you look at the pre-war evolution of the US, UK, German, and Japanese aircraft designs, it was fairly even across the board. In 1937 you could maybe say that Germany had the best fighter in the Bf109, in 1938 the US had the best [ insert here], the UK had the best [insert here], Japan had the best [insert here]. In 1939 the [insert here] had the best [insert here], etc.

After 1939-40, the big change was the US and UK access to high quality 100/125 and 100/130 grade respectively. And they started to design their aircraft to use the fuel. Other than providing the same fuels to Japan, you would need to increase their population base, industrial base, and natural resource base, in order for the Japanese to do what the Western Allies did. One of the primary reasons that Japan and Germany went to war was to gain secure and ready access to strategic resources.

So in order to have the military aviation of another country such as the US, UK, or to a degree Germany, behave in a similar manner, you would remove access to high quality fuels, and reduce their population base, industrial base, and natural resource base.

Japan was not lacking in scientific, engineering, or military skills - they were lacking in resources to produce what was needed to fight a prolonged war.

If Japan had the same same access to high grade fuels and natural resources, and had the same population and industrial base, as the US had in 1939-40, we might be speaking Japanese now - or at least being politely resentful of Japan 79 years after the end of the war.

 

[Shinpachi]

Japanese had been so hard to immitate the western technologies since the 19th century that they did not notice that they could not win the world with such immitated technologies no matter how hard they modified them. They began to discover their own way with the kamikaze tactics (whichever manned or unmanned), the submarine aircraft carriers like I-400s and the baloon bombs to attack the U.S. homeland directly but such technologies should have begun developments 10 years earlier at latest. See Toyota. They know this lesson very well and are not interested in EV cars from the beginning

 

[ThomasP]

My 2002 Toyota Prius now has just under 610,000 miles on it, and has never broken down and left me requiring a tow truck.

 

[Shinpachi]

It's hybrid and Toyota is going to hydrogen

 

[ThomasP]

It will be interesting to see how well hydrogen fuel vehicles will be received in Japan, and then (hopefully) in the US and other countries. The idea was put forward here in the mid-1990s, but the lack of a manufacturing/logistics chain and the political power of Big Oil have prevented any significant progress.

 

[Shinpachi]

At least, EV cars are not so popular in Japan as other countries due to Toyota's policy for the hydrogen.