Air Service of the Japanese Army, 1938-45 alternative

[tomo pauk]

In order to avoid clogging the IJN air service thread, I'd open an Army-specific thread for discussion about their alternatives in choice of flying hardware, logistics (as far as they can address it), production, etc. The Pacific war unfolds as it did hisorically, ie. the war with West starts as it was the case.

 

[lancer21]

Spurred by the interesting discussion in the IJNAF topic. So yeah, how can they do better? I have various pet peeves of mine on the matter as well, but i will start by throwing ideas like more emphasis on Ki-44, or a Ki-61 with the smaller Ki-60 wing? (Ki-61 had a more refined fuselage compared to Ki-60, that's why despite the larger wing it was faster than Ki-60!). Ki-43 production should start as soon as possible, as imperfect as the Ki-43 was initially, and must replace Ki-27 no latter than 1941. In OTL Ki-27 production continued in parallel until late 1942! I would want at least 4 or 5 sentais to have Ki-43s in late 1941, as opposed to just two OTL. Same with Ki-44, if they don't vaccilate that much maybe they could have a sentai equipped with them already in late 1941 or at least early 1942, rather than a single chutai in OTL (and experimental at that).
Or the Ki-45 designed around the Ha-25 or Ha-26 engine from the start, rather than the troublesome and useless Ha-20, which was one of the major factors the program being so much delayed, the other which may or not be related to the Ha-20 engine being nacelle stall, apparently it flew relatively ok with the Ha-25 engine when this was finally fitted in mid-1940. But as you know eventually they completely redesigned the Ki-45 into the Ki-45 Kai with Ha-102 engines, although it only entered production in 1942. My "good enough" Ki-45 (same form as the prototypes) with Ha-25 engines should be in production in 1940/41, and at least couple of sentais should have them by late 1941, their 20mm cannon must be useful against allied bombers at least.

 

[lancer21]

Reposting link to the IJAAF testing of Bf-109E video on Youtube

View: https://www.youtube.com/watch?v=EsKZScFwXqA


Wow, they could have had the Bf-109E almost two years earlier, in 1939! What a loss for IJAAF, makes you wonder the impact on Ki-43 and indeed IJAAF as a whole (Ki-43 was just a problematic prototype in 1939) if they would have tested the 109E in 1939.

Any idea what did they make of the He-100 and He-112?

 

[tomo pauk]

Spurred by the interesting discussion in the IJNAF topic. So yeah, how can they do better? I have various pet peeves of mine on the matter as well, but i will start by throwing ideas like more emphasis on Ki-44, or a Ki-61 with the smaller Ki-60 wing? (Ki-61 had a more refined fuselage compared to Ki-60, that's why despite the larger wing it was faster than Ki-60!). Ki-43 production should start as soon as possible, as imperfect as the Ki-43 was initially, and must replace Ki-27 no latter than 1941. In OTL Ki-27 production continued in parallel until late 1942! I would want at least 4 or 5 sentais to have Ki-43s in late 1941, as opposed to just two OTL. Same with Ki-44, if they don't vaccilate that much maybe they could have a sentai equipped with them already in late 1941 or at least early 1942, rather than a single chutai in OTL (and experimental at that).

From what I've been able to gather, the Ki-61 have had a more refined cooling system, that helped with speed vs. the small-winged Ki-60. Me - I'd have the Ki-60 designed around a radial engine (Kinsei preferable). That way the cooling system is not an issue, and the radial engine installation will be lighter than the DB 601 installation, that again favors the wing loading.
Ki-44: already with Sakae (or whatever the Army called it) it will be much faster than either the Ki-43 or the Navy's Zero with same engine, since the Ki-44 was much smaller. It can roll fast, it can dive fast, has 4 guns from the get go - excellent.
Ki-27 improvement: introduce the retractable U/C, 1st Zuisei in the nose, than the Sakae. A pair of MGs in the wing. Between the improved Ki 27 and early Ki-44, the need for Ki-43 is much reduced.

Or the Ki-45 designed around the Ha-25 or Ha-26 engine from the start, rather than the troublesome and useless Ha-20, which was one of the major factors the program being so much delayed, the other which may or not be related to the Ha-20 engine being nacelle stall, apparently it flew relatively ok with the Ha-25 engine when this was finally fitted in mid-1940. But as you know eventually they completely redesigned the Ki-45 into the Ki-45 Kai with Ha-102 engines, although it only entered production in 1942. My "good enough" Ki-45 (same form as the prototypes) with Ha-25 engines should be in production in 1940/41, and at least couple of sentais should have them by late 1941, their 20mm cannon must be useful against allied bombers at least.

Do we want the Ki 45 to be a fighter, or perhaps it is better for Kawasaki to make a bomber? Japan can barely afford modern 1-engined fighters, the Ki 45 even with the Zuisei is both taxing them too much, for a feeble gain for 1941 and on: 1 cannon and 2 HMGs @ 340 mph despite the investment of two engines and whatnot.

Perhaps have Kawasaki make a 1-engined fighter around the big Kasei, with two cannons and two HMGs to be made instead of the Ki-45? The Ki-45 was produced in different factory than the Ki-61.

 

[lancer21]

You make some good points, there is of course many possible permutations of what and what not they should have done, mine above was just trying as few changes as possible compred to OTL, the fewer the changes the more feasible they are imo.

Some other ideas regarding different types i like to ponder about.

Ki-30 and Ki-32, cancel the Ki-32 with the inline unreliable Ha-9 and just build more Ki-30 instead.

We've already touched Ki-43,44,60,61 etc. there are many ways they could be better. Indeed forget the inlines, yes to radial engined Ki-61, a maximum of two of the above should be built complementing rather than overlapping eachother (Ki-43,44,61 were built at the same time pretty much), and then Ki-84 asap.

Hmm, interesting your idea of a Ha-25 powered Ki-44, nasty little brute that could have been. At least the wings wouldn't break even at 800kph, how fast would it be, about 550kph?

Ki-45, apart from above, indeed why build it in the first place when perhaps a Ki-46 variant would be good enough if they still want a twin-engine fighter (mostly useful at night).

If we take your idea of a heavy single engine fighter instead of Ki-45 and add to it my 1800HP alt-Mamoru, then we have an "almost P-47" in 1942! Crickey, that would be a nasty 600kph machine, i imagine it as a sort of early Ki-119 type beast.

Ki-49 was underpowered, use the more powerful Ha-101 (Kasei) of 1500HP from the start, and later switch to my alt-Mamoru of still 1800HP but an 18 cylinder of 48 liter based on the Ha-5 family.

Ki-67 was ok, though could use a bigger bombload.

Also i never quite understood why IJAAF and IJNAF bomber bomb loads were so low, just a slight increase to say 1000kg means two 500kg or four 250kg bombs on Ki-21/49, same for navy G3M/G4M etc. The light Ki-48 well i don't really know what was supposed to add to IJAAF, perhaps another example of too many types?

Oh and get the 12,7mm Ho-103 in production as soon as possible, preferably well before the war.

 

[tomo pauk]

You make some good points, there is of course many possible permutations of what and what not they should have done, mine above was just trying as few changes as possible compred to OTL, the fewer the changes the more feasible they are imo.

Some other ideas regarding different types i like to ponder about.
Ki-30 and Ki-32, cancel the Ki-32 with the inline unreliable Ha-9 and just build more Ki-30 instead.
We've already touched Ki-43,44,60,61 etc. there are many ways they could be better.

We're probably more in agreement, rather than in disagreement

Ki-45, apart from above, why build it in the first place indeed, perhaps a KI-46 variant would be good enough if they still want a twin-engine fighter (mostly useful at night).

The 'why build it in the 1st place' comment is what I agree 100%.
People were making 2-engined fighters expecting these will offer a combination of heavy firepower, high performance and long range (if the doctrine called for it). Ki-45 didn't check any of these boxes.

How about a 2-engined fast bomber instead of the Ki 46, start with Kinsei from the get-go? Modified into a fast recon, and into a night heavy fighter? Yes, I'm blindly copying the Mosquito idea.

If we take your idea of a heavy single engine fighter instead of Ki-45 and add to it my 1800HP alt-Mamoru, then we have an "almost P-47" in 1942! Crickey, that would be a nasty machine, i imagine it as a sort of early Ki-119 type beast.

Works for me.
Kawasaki made <2000 of 2-engined fighters, and <3500 of 1-engined ones. An early effort with an 1-engined radial-powered fighter might've probably gotten them about 6000 of those, competitive vs. Spitfire, Hellcat, Corsair or early P-38 versions, while also making the job of the Allied bombers harder.
BTW - seems like Ha 104 (a.k.a. Ha 42) is rarely if ever considered as a 'fighter engine'; granted, it was not some 'sexy' engine, but it gave a lot of power on 87 oct + water/alcohol injection.

Ki-49 was underpowered, use the more powerful Ha-101 (Kasei) of 1500HP from the start, and later switch to my alt-Mamoru of still 1800HP but an 18 cylinder of 48 liter based on the Ha-5 family.

Also i never quite understood why IJAAF and IJNAF bomber bomb loads were so low, just a slight increase to say 1000kg means two 500kg or four 250kg bombs on Ki-21/49, same for navy G3M/G4M etc. The light Ki-48 well i don't really know what was supposed to add to IJAAF, perhaps another example of too many types?

Yes, very small payload for the Japanese bombers. Even if they trade fuel for bombs, rarely the bomb load was greater than 800 kg, even for the powerful Ki-67. Speed was not that great, either.
Perhaps adopt the P1Y idea earlier (yes, it was Navy's A/C), it's relatively small size was making less of the drag than what the big G4M or Ki-49 did.
Ki-48 - again completely agree. Let's turn Kawasaki into an fighters-only company for the Army needs, and forget bombers?

 

[lancer21]

Regarding the Ha-104, it was pretty much R-3350 size (54 liter) but for the Ki-67 at least they deliberately left out MW boost and kept rpm reasonably low so it's as reliable as possible. But it still gave 1900HP (i also found 2000HP). The MW boosted version was giving 2400HP though.

The smaller 48 liter Ha-219 (my alt-Mamoru), was giving as much as 2450HP with MW boost, but of course it was far too late in the war to matter. One can imagine a sort of earlier simpler Ki-87 powered by this engine, pretty much a japanese P-47 (i forgot about this one when posting earlier)

 

[tomo pauk]

Regarding the Ha-104, it was pretty much R-3350 size (54 liter) but for the Ki-67 at least they deliberately left out MW boost and kept rpm reasonably low so it's as reliable as possible. But it still gave 1900HP (i also found 2000HP). The MW boosted version was giving 2400HP though.

Hmm - a fighter designed around a Ha 104 = "Japanese Tempest II"?

 

[lancer21]

They had that idea, namely the Ki-119, but was far too late in 1945, and they wanted it as a fighter bomber due to the war situation. It was quite slow due to the requirements at 580-600kph, had a big wing, carried a 800kg bomb etc.

But one can imagine a fighter optimized pre-Ki-119, somewhat smaller so faster. Kawasaki was working on Ki-45,48,60,61 more or less simultaneously before the war. So in theory by dropping some of those they would have design capacity to work on our favourite radial engine Ki-61 AND this pre-Ki-119.

I was also looking at various late war projects/ prototypes etc. such as the aforementioned Ki-87, then the Ki-83, Ki-94 (both), Ki-74 bomber etc. The 700ph Ki-83 for instance shows the potential of a single seat Ki-46 fighter derivative (the Ki-83 aerodynamics were based on Ki-46).

 

[tomo pauk]

Which ones do you count towards this - Ki-27, Ki-43, Ki-44, Ki-61, Ki-84, A5M, A6M, J2M, A7M, N1K-J?

I would see that as a generational sequence:

Pre-war: Ki-27, A5M
Early-war: Ki-43, A6M
Mid-war: Ki-44, Ki-61, J2M
Late-war: Ki-84, N1K-J, A7M

I've moved this part of discussion to the Army-specific thread.
Ki-43, -44, -84 from Nakajima, Ki-61, -45 from Kawasaki, plus the Ki-102 fighter bomber. Not counting the prototypes that flew, and not counting the Ki-100 as separate design.
Having a competitive fighter by 1942 powered by existing engine type renders a lot of those redundant, hence my trumpeting of the Fw 190 made in Japan.

Could it have been a question of price? If that engine family was markedly more expensive to produce than the competing designs, that would explain its abandonement.

Ha 109 cost by early 1943 was 25000 yen, the Sakae was 20000 yen (probably the same price for Zuisei for the Ki-45 and Ki-46-I and -II). Ha 109 was making 35-40% more power than Sakae or Zuisei (Ki-44 carried 50-100% greater firepower than Ki-43, was faster, could roll and dive far better than the Ki-43), yet Japanese were willing to pay for two Zuiseis on the Ki-45, in return for 60 km/h deficit vs. Ki-44. Or to pay for two Kinseis on the Ki-102.
So I'd chalk the phasing out the Ha 109 and Ki-44 under 'Japanese Army air srvice made a bad procurement decision' category.

 

[HoHun]

Hi Tomo,

Ki-43, -44, -84 from Nakajima, Ki-61, -45 from Kawasaki, plus the Ki-102 fighter bomber. Not counting the prototypes that flew, and not counting the Ki-100 as separate design.
Having a competitive fighter by 1942 powered by existing engine type renders a lot of those redundant, hence my trumpeting of the Fw 190 made in Japan.

Ah, I forgot the Ki-100. I left out the Ki-45 on purpose though since the post I was responding to said "single-engined" fighter

I believe a Fw 190 was tested in Japan, too. Years ago, we had a long thread over on j-aircraft.com ... https://www.j-aircraft.org/smf/index.php?topic=15249.0

Here's an interesting page on the Japanese perspective on the Fw 190: https://arawasi-wildeagles.blogspot.com/2014/01/japanese-focke-wulf-fw-190.html

With regard to competetiveness, what was the point you'd consider the (latest) Japanese fighters weren't at least equal?

If you want a Japanese fighter that's actually available in more than penny-packet numbers in 1942, it's either the A6M2/3 or the Ki-43-II.

Potentially, these could be modified to take a more powerful engine, which I guess would be your best bet. The Fw 190A was just being introduced to the Luftwaffe in late 1941, and still having a lot of teething troubles, so I'm not sure how realistic it was to expect it to come off Japanese production lines by 1942. I don't think Japanese production Fw 190s could have been powered by BMW engines, so we would have to pick a (hopefully) suitable Japanese engine instead.

Ha 109 cost by early 1943 was 25000 yen, the Sakae was 20000 yen (probably the same price for Zuisei for the Ki-45 and Ki-46-I and -II). Ha 109 was making 35-40% more power than Sakae or Zuisei (Ki-44 carried 50-100% greater firepower than Ki-43, was faster, could roll and dive far better than the Ki-43), yet Japanese were willing to pay for two Zuiseis on the Ki-45, in return for 60 km/h deficit vs. Ki-44. Or to pay for two Kinseis on the Ki-102.

Thanks, that's highly interesting! Where did you find information on the prices? That's quite fascinating to consider! I'm a big fan of the Ki-44, which in my opinion is quite a competitive aircraft that doesn't get the appreciation it deserves!

To not abandon my original point entirely, I still think that it might be possible that the Yen prices don't tell us everything about the effort and resources required to build these engines. Maybe they reflect the economic costs accurately, but any attempt to produce them in greater numbers would have required much greater investment in tooling than the competing engines?

However, one thing that I find a bit puzzling about the Japanese engine industry is that they built so many of these small twin-row 14 cylinder engines that didn't provide much more power than some single-row radials, like the R-1820. Or is that a wrong impression I get from comparing the 1942 Japanese engines to the 1944 US ones?

Regards,

Henning (HoHun)

 

[lancer21]

Interesting info re costs, do you by any chance have information re costs and manhours necessary to build the Ha-112/Kinsei and the Ha-40/Atsuta? Would it take less manhours to build a radial compared to an equivalent inline in general?

Getting back to the Ha-109, let's not forget that it was a larger, heavier engine, so despite it's 1500HP some of that would be gobbled up by increased drag both from the engine, and from the larger airframe necessary to carry said engine.

So among the many possible permutation one is just merge the Ki-44 and Ki-61 concepts into one and either have a big wing Ki-44 or a radial engine Ki-61, and replace the Ki-43 in production asap.

 

[tomo pauk]

With regard to competetiveness, what was the point you'd consider the (latest) Japanese fighters weren't at least equal?

If you want a Japanese fighter that's actually available in more than penny-packet numbers in 1942, it's either the A6M2/3 or the Ki-43-II.

Potentially, these could be modified to take a more powerful engine, which I guess would be your best bet. The Fw 190A was just being introduced to the Luftwaffe in late 1941, and still having a lot of teething troubles, so I'm not sure how realistic it was to expect it to come off Japanese production lines by 1942. I don't think Japanese production Fw 190s could have been powered by BMW engines, so we would have to pick a (hopefully) suitable Japanese engine instead.

We can take a look at what was actually up against Japanese (ie. no point in comparing also the German stuff), and then draw conclusions? Not just bombers, but also fighters; just Army A/C in this thread?

My take is that historical Japanese fighters were still very useful in better part of 1943. Yes, Ki-43 can't dive well, protection is non existing, firepower can kill a fighter but will struggle with a bomber; Ki-44 requires an experienced pilot that knows how to use boom and zoom, but then again neither the Allied fighters are all flawless, just a small number of them can out-pace the Ki-44 or out-climb and out-maneuver the Ki-43. Once Allies field a good number of Spitfire VIIIs, F4Us, F6Fs, P-38s, P-51A/C/D, P-47, the game is set against the Japanese fighters. They also had very small chances to catch Mosquito or B-29. Even the A-20 is a problem.

The 'penny packet' number of new-gen Japanese fighters is indeed a problem that I'm dabbling about like a broken record Investing in a 2-engine fighter (Ki-45) that is not better than a Zero was a dire mistake - have Kawasaki make the Ki-44 instead. Even the Ki-44 with same engine as the Ki-43 is a better thing than the said Ki-43, let alone if the Kinsei is on the Ki-44. Or make the Ki-60 or Ki-61 with a radial engine from the day one, in both Kawasaki's factories.

Ki-43 with Kinsei also makes sense.

Troubles of the Fw 190 were caused by the engines, 1st the still-born BMW 139, then by the problematic BMW 801. Japanese Fw 190 uses Japanese engine (Ha 109 preferably, Mitsubishi can try with Kasei) and the engine woes don't happen.

Thanks, that's highly interesting! Where did you find information on the prices? That's quite fascinating to consider! I'm a big fan of the Ki-44, which in my opinion is quite a competitive aircraft that doesn't get the appreciation it deserves!

I've read that in a doc downloaded from the Japanese archives, hopefully I'll nail the download link and post it.

However, one thing that I find a bit puzzling about the Japanese engine industry is that they built so many of these small twin-row 14 cylinder engines that didn't provide much more power than some single-row radials, like the R-1820. Or is that a wrong impression I get from comparing the 1942 Japanese engines to the 1944 US ones?

Flood of the small 14 cylinder engines was certainly not getting the Japanese anywhere. Especially when looking at mature bigger engines they also had in production. Small engine of 1100-1200 HP is a bad thing in a fighter past 1942 (even at Pacific/Asia), when the enemy is not just outnumbering you, but also does it with fighters that have another 300, 500 or 800 HP more.

Interesting info re costs , do you by any chance have information re costs and manhours necessary to build the Ha-112/Kinsei and the Ha-40/Atsuta? Would it take less manhours to build a radial compared to an equivalent inline in general?

Getting back to the Ha-109, let's not forget that it was a larger, heavier engine, so despite it's 1500HP some of that would be gobbled up by increased drag both from the engine, and from the larger airframe necessary to carry said engine.

IIRC the doc with prices was Nakajima-only. If a company is already making radial engines, it is probably prudent for them to carry on doing that rather than to make a switch to the liquid-cooled engines; both Kawasaki and Aichi were making radials under licence befoe the DB 601 copies (Kawasaki was making radials until 1945). We can take a look at prices of American engines and perhaps arrive at the ballpark?

Ki-44 was the smallest Japanese fighter, still it carried the Ha 109.
600+ km/h in mid 1942, that is more than 50 km/h faster than it's most likely opponent, the P-40. Or 70-80 km/h faster than Ki-43, Hurricane or F4F.

So among the many possible permutation one is just merge the Ki-44 and Ki-61 concepts into one and either have a big wing Ki-44 or a radial engine Ki-61, and replace the Ki-43 in production asap.

Agreed with the proposals.

 

[tomo pauk]

FWIW, the pdf with downloading links for a lot of USSBS reports:

 

[HoHun]

Hi Tomo,

FWIW, the pdf with downloading links for a lot of USSBS reports:

Thanks a lot, there are quite a few fascinating documents linked in that list!

One document (No. 4009762) translates a German report on the Japanese war efforts, dating from November 1944.

"It is extraordinary that, considering the amount of the workers and factories, aircraft production is noticably smaller than in Germany."

The reasons are given as (with a bit of my interpretation):

- Insufficient numbers of qualified workers and, especially, managers, and insufficient training for the average worker
- Insufficient production of flight instruments (which I guess means aircraft ("Fluggerät") ... the translation seems a bit odd here) - not designed for mass production, lacking standardization, ignorance of manufacturing methods, including tooling.
- Poorly organized factories - for lack of technical personnel, incomplete understanding of adapted foreign technologies, a pre-industrial mindset, lack of standardization, tooling poorly suited for mass production. Outsourcing of production tasks is poorly organized, too.
- Machine tools - due to the priority of aircraft production, standard machine tools are available in sufficient quanitities, but special tools such as presses are scarce, which impedes mass production. The available special tools were imported before the war from the US, Britian and Germany, but Japan basically has no production capacity to speak of for such machines.
- Raw materials: Steel is in danger of running short, but the aviation industry received priority for the moment. Ore and bauxite is available in sufficient quantities, but the enemy advance in the south threatens this availability.
- Transportation: Currently there is just enough transportation capacity to provide raw materials, but once the Allies start attacking transportation, that might easily cause a crisis.

Summary:

"[...] the ignorance of the constructors [= designers] regarding production methods together with lack of standardization, good technical personnel, and a number of special machine tools and the resulting old-fashioned manual production prevents greater output of flight instruments [= aircraft, in my opinion]"

Some interesting quotes are included in the attached snippets.

Regards,

Henning (HoHun)

 

[tomo pauk]

- Insufficient production of flight instruments (which I guess means aircraft ("Fluggerät") ... the translation seems a bit odd here) - not designed for mass production, lacking standardization, ignorance of manufacturing methods, including tooling.

Yes, I'd agree with your interpretation of the word "Fluggerät".

 

[lancer21]

Pondering about IJAAF again, how about a small wing Ki-43 (15sq meter wing like the Ki-44) if we somehow make the japanese embrace the small wing concept like Bf-109 or He-112B rather than continue with their dogfight obsession?

Or indeed how about an early Ki-44 powered by the 1080HP Ha-5 engine instead of the Ki-43 altogether? Trying to guesstimate performance, since the Ki-44-I was doing 580kph on the 1260 HP Ha-41 engine (itself developed from Ha-5), would a figure of say 550kph be realistic for this early 1939 Ki-44?

About engines, what if Kawasaki will keep developing the Ha-9 like the soviets did continuously with the Mikulin M-17/34/35/37/38/42 series, also based on the BMW-VI. OK it's a big honking engine at 46 litre (or aparently 42 litre for the Ha-9), but compared to the highly tuned DB-601 needing precise tolerances and good quality materials to have it work properly, they could be getting same power from the larger developed Ha-9 (hence not needing such high RPM etc.), sacrificing some weight and drag for reliability, not to mention retooling to build the DB. Just a thought, though still just building radials instead of inlines would be easier.

Btw regarding Ki-43, as i understand it did have self sealing tanks, on the Ki-43-I aimed to protect against 7,7mm rounds and on the later Ki-43-II aimed to protect against the 12,7mm rounds, but i guess they were not every effective (though according to the Osprey Ki-43 Aces book still of some help)?

 

[tomo pauk]

Pondering about IJAAF again, how about a small wing Ki-43 (15sq meter wing like the Ki-44) if we somehow make the japanese embrace the small wing concept like Bf-109 or He-112B rather than continue with their dogfight obsession?

Or indeed how about an early Ki-44 powered by the 1080HP Ha-5 engine instead of the Ki-43 altogether? Trying to guesstimate performance, since the Ki-44-I was doing 580kph on the 1260 HP Ha-41 engine (itself developed from Ha-5), would a figure of say 550kph be realistic for this early 1939 Ki-44?

Both small-winged Ki-43 and 'Ki-44 minus' are good ideas. Especially the early Ki-44, it should've worked even with Sakae, speed should've been better than what Zero did, let alone the Ki-43. Unlike these two, it adds a good rate of roll and useful dive speed, comparable to what the Western fighters had.
For a small fighter with good performance on modest power, we can take a look at the FFVS J.22 (yes, it was later than the Ki-44).

About engines, what if Kawasaki will keep developing the Ha-9 like the soviets did continuously with the Mikulin M-17/34/35/37/38/42 series, also based on the BMW-VI. OK it's a big honking engine at 46 litre (or aparently 42 litre for the Ha-9), but compared to the highly tuned DB-601 needing precise tolerances and good quality materials to have it work properly, they could be getting same power from the larger developed Ha-9 (hence not needing such high RPM etc.), sacrificing some weight and drag for reliability, not to mention retooling to build the DB. Just a thought, though still just building radials instead of inlines would be easier.

As in the last IJA topic post - a big engine allows for a lot of elbow room vs. octane fuel rating and tight tolerances. A V12 (even a big one) = less drag than most of the powerful radials.
The Ha-9-powered Ki-28 was the fastest of the 3 types tested by the IJA, the Ki-27 was picked due to it being the most maneuverable. If Kawasaki can get on a 1000-1100 HP version of it by 1940, it should make a lot of impetus to have the new fighter powered by it, certainly a faster fighter than it will be possible with a radial engine of the same power. Issue with the BMW V12 engines is that they were featuring 'independednt' cylinders; Mikulin's engines were with cylinders en-bloc from M-34 on - probably a reason why Kawasaki with blessing by Army went to the DB 601A licence?

 

[lancer21]

Perhaps they could invest some time/resources into redesigning the Ha-9 just like Mikulin did with the AM-34, i see no reason why they can't get 1100-1200HP out of it in 1940 or so and 1400-500HP in 1942 or so, and even more with MW boost late war (say 1700-1800HP or so). If the end result is a bit easier to manufacture and a bit more reliable than the Ha-40, it's useful to have it.

Incidentally, the Ki-45 was initially designed around the Ha-9 before switching to radials, so with a pair of these ALT Ha-9s it will be a different, faster beast, which may make it more useful to have.

 

[tomo pauk]

Perhaps they could invest some time/resources into redesigning the Ha-9 just like Mikulin did with the AM-34, i see no reason why they can't get 1100-1200HP out of it in 1940 or so and 1400-500HP in 1942 or so, and even more with MW boost late war (say 1700-1800HP or so). If the end result is a bit easier to manufacture and a bit more reliable than the Ha-40, it's useful to have it.

Incidentally, the Ki-45 was initially designed around the Ha-9 before switching to radials, so with a pair of these ALT Ha-9s it will be a different, faster beast, which may make it more useful to have.

The M-34 was a brand-new engine vs. the M-17. Kawasaki should've probably tried to do the same; they will need to do that fast.
If there is such a 1100-1200 HP V12 engine in 1940, a high-performance fighter can be designed around one engine. 1400-1500 HP in 1942 should've easily propelled a fighter close to 620-630 km/h.

Japanese-language Wikipedia notes that Ki-45 was designed around the Ha-20 engine ('Hikari'; 470-480 kg). The AM-35A was 830 kg + weight of cooling system. A twin with two big V12s would've been size of Bf 110?