Ki-83, was it as good as thought?

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Staff Sergeant
Jul 30, 2012
Chicagoland Area
Does anyone have any information about the Ki-83? It seems to get high praise based on prototypes captured by the US at the end of the war and looks good on paper, but does anyone have concrete info about it? It seems like a later Japanese version of the FW187, good potential in prototype form.
They only built 4 and they were test-flown by US pilots after the war and highly praised. They never flew dissimilar air combat that I've ever seen anywhere (and I've looked), and the fate of the last one is unknown ... presumed scrapped in 1950.
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Any idea what performance would have been with high performance inline liquid cooled engines like a DB603 would have been? I think the drag would have been lower and the supercharger better.
I could take a stab at it, but it's a "what if," and could be argued endlessly. The US test revealed a high speed on good fuel, but it was rated at about 438 mph on end-of-war Japanese fuel. I haven't really done much research on it since they only built 4.

We'd have to know the HP achieved for the US tests and the HP anticipated from the inlines, and the % decrease in drag anticipated. All of these would be a guess because the 483 mph I have seen quoted has been passed along over the years ... but I've never seen the flight test report that was cited.

Without that it is an exercise in frustration since everything is unknown.

So, the engines in it were rated at 2,070 HP. The DB inlines were mostly rated at from less up to about 1,700 Hp with MW50 injection at 13,000 feet. So it we take the Japanese quoted speed of 438 mph and assume a drag reduction of about ... say ... 15%, it would still come in at 434 mph ... or just about the same. But the 1,700 HP with MW50 was with German "good fuel," so it's hard to say. If you disagree, don't bash me ... post your own estimate instead.

But the Ki-83 could not have done anything but help the cause had they gone into production and had they actually been delivered in some numbers, at least from a performance standpoint. From a manufacturing standpoint, I can't begin to make a good estimate. Japan was hurting for manufacturing near the end of the war, both from running out or raw material and damage from continuous bombing. I have no idea how many Ki-83's might have been made or if they had pilots and fuel for them.

I suspect the Ki-83 might have been a bright spot in the otherwise dismal running down of their war-making capability. The individual Japanese soldier was always a good one. Their bravery was never questioned. But they did run out of good pilots and their products were having a hard time, quality-wise, near the end. Some of that was metal that was being made without all the needed components.

It's tough to meet production schedules when you have daily bombing raids on manufacturing facilities, few remaining good pilots, and little coming in as far as raw material goes.

WWII really WAS the first war to be decided by aircraft.

These planes were said to be remarkably maneuverable and are cited as being able to execute a 2,200 foot diameter loop at 400+ mph.
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Here's my 2 pages on the Ki 83 from Green, William and Swanborough, Gordon "Japanese army fighters: Part 1", Macdonald and Janes 1976

Hope the text is readable, it worked in the preview. You'll note that something went horribly wrong in translation between km/h and mph for 8000 meters.


The Ki-83 seems to have laminar flow wings.
I wonder why the Ki-45 Toryu was not as good as it has almost the same specifications and dimensions?
In the specifications posted by just schidt we should notice that even with japanese fuel could achieve 704 km/h, but more amazingly reach 33000ft in just 10,5 minutes!
It appears that with High octane fuel would be competitve at RoC even with late war alleid single seaters. And that level of performance by a 2 Seat plane, that even possesed a small Internal bomb bay!
The implication of the numbers, 416 mph at 5,000 m, 426 mph at 8,000 m and 437 mph at 9,000 m, is that the critical altitude of the turbosupercharger is relatively low. Indeed a good reason for doubting if Japan could have produced many Ki 83s is that Japan had great difficulty building turbosuperchargers. If we compare a rough contemporary from America, the P-47N, we find that the Ki 83's empty weight is 26% heavier (13,907 lb versus 11,000 lb) and its wing area is 12.4% greater (362 sq. ft. versus 322 sq. ft.). The Ki 83 has about 4,000 hp compared to 2,800 hp for the P-47N and the speed at around 15,000 ft is fairly similar with 416 mph at 5,000 m for the Ki 83, which will be at military power, compared to 417 mph at 15,000 ft with the P-47N using WEP (Republic data from P-47 Performance Tests). However, the P-47N has a critical altitude of 32,000 ft with WEP at which its speed is 467 mph. The conclusion is that the Ki 83 would be much faster with American superchargers.
I'm not too sure we'd have sold or licensed the Japanese any turbos right about that time. Something about the war being in the way maybe. Suppose you are right anyway, but they couldn't get any American turbochargers. Where would you be headed with this conclusion? I doubt seriously the Japanese would have licensed the USA to build any Ki-83's either.

That pretty much leaves us with 4 Ki-83 prototypes that never saw combat, doesn't it? Right about where we are now?
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Focusing on mechanical superchargers with good aerodynamic design for the compressors and ducting as well as efficient intercooler design and good ejector exhaust stubs (good for radials at least) would have made more sense for the Japanese. It's not much different from comparing the turbocharged V-1710 to the Merlin/R-1650 or Turbo R-2800 to similar series 2-stage supercharged R-2800s except that V-12s naturally make for more efficient ejector exhausts.

A slightly smaller (or at least lighter) twin should have mated to a pair of Kasei or Homare engines well enough and not been held back by engine/turbo developments.

Mitsubishi already had an excellent starting point with the Ki 46 as far as aerodynamic qualities went, they just needed an airframe built heavily enough to cope with fighter maneuvering while also being better suited for a heavy nose mounted armament. (and associated CoG and a better rear view though the pilot's canopy -without an observer)

If the Ki 46 itself was actually able to be reinforced for reasonable fighter specs early in the war, then that was a big missed opportunity in itself compared to leaving that role to the lower performing Ki 45. Later Ki 46 models were already armed for interceptor duties and up-engined to 1500 hp Kinsei engines, so it seems like a possible missed opportunity. (including replacing the Zuisei engines with 12-1300 hp Kinsei engines prior to adopting the 1500 hp models)
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Nothing much to add, especially as i don't directly have a link to the discussion, but a buddy of mine who used to frequent J-Aircraft and normally is a great knowledge base on Japanese aircraft once mentioned that they had a large discussion about the Ki-83s top speed and to the best of their abilities concluded that it was most likely in the range of 730kph with WEP (notable because the Japanese never tested speed or climb at anything beyond Military), and that the various figures putting it at about 760kph probably would of required quite a bit of extra horsepower (400hp i believe.)

However this is literally a retelling of a discussion about a discussion from a trustworthy friend ("Hiromachi"), so of course understand i am not claiming concrete knowledge on the matter. (if anybody can find this discussion on J-aircraft please link it, so far I've come up with nothing)

I would add that i would love to know more about its wing design, but finding much of anything concrete about this aircraft seems rather hard. Without a doubt though it was a good design and surprisingly attractive.
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Looks like a thoroughbred to me, but came too late to make a difference. I think the first indication of Japanese twin prowess were the Ki-45 and Ki-46, both of which were good. The Ki-83 was likely an outgrowth of the success with the earlier two. Given the state of the war, it would not be at all surprising to learn on intercompany cooperation.

But I have no basis for that, just a thought ... perhaps not ...

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