Japanese Navy air service, 1938-45, with hindsight?

[tomo pauk]

Time frame should cover gearing-up to the Pacific war and the war itself.
What should've they specified differently for industry to make vs. what was made historically, in order to put up a better fight against the 'West', or mostly against the USN/USMC/USAAF? Not to make a host of designs that were produced in handful quantities each, like the numerous floatplanes? A more timely follow-up for the Zero? A much improved Zero for the mid-war, or an 'alternative Zero' from day one? Peek a bit better at German tech plans and operational experiences? Earlier introduction of protection both for crews and fuel tanks?
The ww2 still unfolds as it did historically until some time of 1942 here. Engine choice is more or less same as historical, make some tweaks or economizatios as you please. Guns - tad of the tweaking of what was historically available to Japan.

 

[tomo pauk]

This one got a lot of traction

Anyway. Cut the bespoke floatplanes' designs past 1939. Need a fighter on floats? Do what was done with the Zero: install the floats so there is a Rufe. Need a 2-/3-seater with floats? Install the floats on the Val or Kate or whatever.
That leaves Kawanishi and Aichi to mass-produce something of worth instead of wasting the time - a most precious commodity. Granted, Aichi's Val dive bomber was very useful, so press on with it, too.

 

[NOMISYRRUC]

All I can think of is... in the period between 1st January 1938 (the point of departure) and 8th December 1941:

• Train more aircrew, especially pilots;
• Train more ground crew, especially mechanics;
• Build more aircraft; and...
• Create a larger stock of aviation fuel.

Whether any of the above is possible is another matter.

For example...

As I understand it the IJNAF's excessive emphasis of quality over quantity resulted in many trainee pilots who would have become aces in any other aviation service being failed by their instructors.

If that's true the trainees that failed their training courses in the "real world" should be allowed to complete their training in "this version of history". They would be a reserve which would be used first to bring the IJNAF to its War Establishment on mobilisation, replace losses in the early campaigns and the remainder would become instructors.

 

[Dilandu]

Train more aircrew, especially pilots;

Exactly how? Japanese air training program was multi-year ones, because before starting the pilot training, they need firstly to train candidates in basics. Let's not forget, Japan was still very agrarian country. A lot of wannabe-pilots never ever drive a car in their whole lives, and have zero clues how internal combustion engine worked. They need to get a most basic training before they could be trained to actually fly a plane.

 

[NOMISYRRUC]

Train more aircrew, especially pilots;

Exactly how?

Which is why I wrote...

Whether any of the above is possible is another matter.

 

[NOMISYRRUC]

Japanese air training program was multi-year...

The point of departure is 1st January 1938 that's three full years and 93.70% of a fourth year before Japan enters World War II.

According to Guy Robbins on Page 215 of The Aircraft Carrier Story 1908-45...

The enlisted pilots were given a 30-month educational course before undergoing eight months of flying training (divided between basic and operational) of more than 100 hours, plus ground school which gave them a wider knowledge of the theory of flight and engine design than their American counterparts. The officers were selected after at least two years at sea and therefore did not need any general education, but they did have a two-month ground course before a ten-month flying course (150-175 hours).

That's 38 months to train an enlisted man and 10 months to train an officer.

With a start of 1st January 1938 there's enough time to train two classes of extra enlisted men (1938 and 1940) by the end of February 1942 and the extra men in the 1940 Class to complete their training in February 1943. That is each class begins on 1st January and ends at the end of February.

With the same starting date there's enough time to train 4 classes of officers (1938 to 1941) by the end of 1941. I.e. each of the four classes begins on 1st January and finishes on 31st December.

It aught to go without saying that an earlier point of departure would allow more time to train more pilots and as the number of pilots increased some of the extra pilots can be used to increase the number of pilots under training. That is subject to the availability of ground infrastructure, ground crew, aircraft and fuel - all of which should go without saying as well.

Quote from the Wikipaedia page on the Washington Treaty...

On December 29, 1934, the Japanese government gave formal notice that it intended to terminate the treaty. Its provisions remained in force formally until the end of 1936 and were not renewed.

@tomo pauk I think that this date (29th December 1934) is a better point of departure for the thread than the beginning of 1938. What do you think?

 

[NOMISYRRUC]

A lot of wannabe-pilots never ever drive [drove] a car in their whole lives, and have [had] zero clues [clue about] how [an] internal combustion engine worked. They need needed to get receive a most [an extremely] basic training before they could be trained to actually fly a [an] plane [aeroplane].

A lot the of wannabe-pilots that enlisted in the RAF hadn't driven a car before they "joined up" too. I very much doubt that many of them learned how an internal combustion engine worked when they were at public school or grammar school. I suspect that they also required extremely basic training before they could be trained to fly an aeroplane.

The above applies to the wannabe-pilots from the British upper and middle classes.

Hardly any of the wannabe-pilots from the working class would have driven the car before they enlisted. They would have known how an internal combustion engine worked. However, that's because the were "Trenchard Brats" (e.g. Frank Whittle) who had trained to be mechanics at Halton where they finished top of their classes and thus qualified for officer & pilot training at Cranwell.

In spite of these handicaps the RAF was able to quadruple its size from 30,000 regular personnel in 1934 (when expansion began) to 118,000 in the original 1939-40 Air Estimates (i.e. 5 years only one year more than is available to the IJNAF in the Opening Post). Plus it was able to train several thousand RAF Volunteer Reserve pilots between 1936 and the outbreak of World War II (which is one year less than the time available to the IJNAF in the Opening Post.)

 

[tomo pauk]

@tomo pauk I think that this date (29th December 1934) is a better point of departure for the thread than the beginning of 1938. What do you think?

Better for Japanese, since it gives them extra 3 years. OTOH - extending all of this to 7 years would've diluted the thread I'm afraid.
There is a lot to change for the IJN air service in 4 years, eg. Japanese can start shrinking the pilot training program towards 15-20 months, so they have a bigger pool of pilots for 1940 and on. They have a 'luxury' of having the pilots flying combat missions in the late 1930s, so the novices can gain experience.
The most valuable pool of well trained and experienced pilots need to be protected. Mandatory use of parachutes, installation of protection both for crewmen and fuel tanks, a reliable rescue service... Need for protection to be installed also means earlier emphasis on more powerful engines, like the Ha-41/-109, Kasei and Kinsei, that in turn might mean that by 1942-43 IJN aircraft are on more even terms vs. what West was making, while being crewed by reasonably capable men.

 

[lancer21]

I wanted to post here some time back, one of my qualms is with the J2M and N1K1-J, not only overlapping but also poor, the J2M was a huge mistake, swallowing design and production resources that might have been better used to get the A7M built asap.

So no J2M means Mitsubishi can focus on A7M which flies in spring 1942, big question though is with what engine, they need a minimum of 2000HP for it, i can't think of anything remotely suitable in spring 1942, the Kasei is too weak, the Homare will not be available in prototype form until late 1942 as i understand. Maybe if Mamoru is cancelled as i was saying elsewhere possibly some prototype Homare might be available earlier. At any rate for this to work the MK9/Ha-211 must be given top priority, so perhaps first flight ready prototypes will be available to power the A7M in 1943.

I would assume the reliability won't be much different from Homare due to the general fuel/quality steel situation, but still i think the A7M has the potential to be a better machine than the J2M AND fly off a carrier.

If they still want a land based interceptor, then have Kawanishi work on a low wing Shiden (which THEN can be fitted with floats if they still want a float fighter), which can fly in spring 1942 with whatever engine is available until Homare is ready.


I would also cancel the J1N, waste of resources, i can't think of it contributing in any significant way to the war effort, if they want a nightfighter just put an oblique cannon on the D4Y which is as fast, or perhaps get a navy variant of the Ki-46 which IJNAF used with an oblique cannon (this one is also faster than J1N). Oh and of course forget about any inlines for the D4Y, just put the Kinsei on from the start, it is more reliable, more durable and saves a lot of hassle, and the speed is just a few kph less.

 

[tomo pauk]

J1N indeed needs to go away.
As for the fighters: have the companies make the next-gen carrier-borne fighters. Mitsubishi (no J2M), Nakajima (no C6M recon, gorgeous as it was), Kawanishi (no flood of floatplanes' designs). Even Yokosuka, their fighter proposal using the wings from the D4Y. May the best fighter win. There is no point in making bespoke floatplane fighters, or dedicated ground-based fighters for the Navy.
Start with 1400-1500 HP engines (available from Spring of 1941 as the Ha 109 and Kasei), up-engine the new fighters when new engines are available. Already the Kasei in 1943 offers 1800+ HP. Don't bother with the counter-rotating Kasei, or the one with extension shaft and cooling fan.

 

[BB1984]

A lot of 20/20 hindsight here, but a modest acceleration of the Kinsei development (instead of wasting time/resources on cloning the DB601) could make both the A6M8 version of the Zero and the Ki-100 available in 1942 instead of 1945.

 

[muttly]

Perhaps they could have turned to Germany or maybe England and learned
more about liquid cooled engines and the Spitfire and 109 designs. Just a thought.

 

[tomo pauk]

Perhaps they could have turned to Germany or maybe England and learned
more about liquid cooled engines and the Spitfire and 109 designs. Just a thought.

Japanese tried with liquid cooled engines, and made a lousy job there. IJN will probably find Spitfire and Bf 109 lacking - neither was a good carrier-vessel bird as the Zero.

 

[muttly]

Anyone else the could have turned to for land based and carrier aircraft?

 

[tomo pauk]

Anyone else the could have turned to for land based and carrier aircraft?

'They', not 'the'? For land-based stuff it is easy, He 111, Ju 87, Ju 88, Fw 190, even Bf 109 - all with Japanese radial engines, though. British will not sell Spitfire, other stuff is either not worth it, or it is too late for the Japanese ww2.
American military stuff is meh before A-20, SBD or P-40, by what time it is too late. Japanese probably gained a lot of information via purchase of the DC-4E and licence agreement for the DC-3.
For carrier-based, IJN is at the top of the game in 1941-42 when it is about aircraft designs they have, the problems lay elsewhere. Like the pletora of single-purpose designs all competing for the small production capacity (when compared with what West had): J2M, J1N, C6N, half a dozen different floaplanes. The decisions to keep the 1000-1100 HP engines on a lot of 1st line aircraft even by 1943 is cringeworthy. Time and opportunity lost with Aichi licence-building the DB 601. No 2-stage supercharged nor trubo-supercharged engines is also a big problem.
Then we have a thing of pilot's training, too late introduction of radar (especially on aircraft), bad and incomplete installation of radio sets, neglecting of protection both for pilot/crew and fuel tank as if the crewmen and aircraft grow on the trees, lack of flexibility with what pilot is deployed where.... A lot of stuff that needs to be addressed.

 

[BB1984]

Anyone else the could have turned to for land based and carrier aircraft?

'They', not 'the'? For land-based stuff it is easy, He 111, Ju 87, Ju 88, Fw 190, even Bf 109 - all with Japanese radial engines, though. British will not sell Spitfire, other stuff is either not worth it, or it is too late for the Japanese ww2.

It's not clear to me why they would bother with Fw190 or Bf109 when they could have had the both the A6M8 version of the Zero and the Ki-100 available in 1942 if they had just been able to speed up Kinsei development to get a 1500 HP version in 1942 (not a big leap if the resources put into the DB601 had gone into Kinsei development instead).

• For shipboard, then cancel the J2M Raiden to free up Mitsubishi resources to get the A7M Reppū in service faster (which is also assisted by the Kinsei speed up, since that opens a path to getting the 18 cylinder Ha-43 sooner, which would also open a path to up-engining the Ki-100 . . . )

The D4Y dive bomber is the same story as the Ki-100, they could have skipped over the whole liquid cooled experiment and gone straight to the Kinsei; in any case the D4Y was a whole generation ahead of the Ju-87 and the D3A was "good enough" for early war so I'm not clear on any benefit of the Ju87.

The Ju88 is more interesting. A longer ranged plane capable of both dive and torpedo bombing would have been valuable, but even given the "what if" of the Japanese adopting it, they would have wanted to go to the slimmer fuselage Ju88S/Ju88G look much sooner to at least minimize the survivability problems the Luftwaffe ran into and to make it a more capable heavy/night fighter (same comment I made in the Luftwaffe "what if" thread). The Ju-88 would be the bridge to either a linearly developed Ju388 type plane or the P1Y Ginga.

 

[tomo pauk]

It's not clear to me why they would bother with Fw190 or Bf109 when they could have had the both the A6M8 version of the Zero and the Ki-100 available in 1942 if they had just been able to speed up Kinsei development to get a 1500 HP version in 1942 (not a big leap if the resources put into the DB601 had gone into Kinsei development instead).

Performance of Ki 100 was unimpressive by 1943 standards, so was that of the A6M8; even the A6M3 offered almost same turn of speed by mid-1942. Fw 190 can use the Ha 109 (already in production by mid 1941) and perform much closer to the Ki-44-II, rather than languish in 360 mph zone as the Ki 100 and A6M8 did.
Bf 109 was a much smaller aircraft than Zero or Ki-100, so we can expect it to out-perform those on same engine.

BTW - Ki 100 was Army's machine, Kawasaki was not making anything for the Navy.

The D4Y dive bomber is the same story as the Ki-100, they could have skipped over the whole liquid cooled experiment and gone straight to the Kinsei; in any case the D4Y was a whole generation ahead of the Ju-87 and the D3A was "good enough" for early war so I'm not clear on any benefit of the Ju87.

A much greater payload capacity. On 1000 HP, the Ju 87R-1 was rated for 1000 kg bomb and two drop tanks. Make those with 1100 HP Japanese radial instead of the D3A.
D4Y was indeed a good idea; yes, the engine need to be a radial from the get go.

The Ju-88 would be the bridge to either a linearly developed Ju388 type plane or the P1Y Ginga.

Ginga was a very good idea, if late to matter.

 

[lancer21]

I'm not a big fan of having the japanese just dump their stuff and build german, although i can see merits to the idea. For instance, i can see why they would be better off building a japanese FW-190 with either a licence built BMW-801 or a japanese radial on it, it's a good, mature airframe. This instead of the subpar J2M and N1K1-J.

About the D3A, i never understood why they haven't made it to carry a 500kg bomb. The SBD has the same power and carried a 1000lb. One way i was partially fixing this is for an intermediate 375kg bomb to be carried by the D3A (since payload is listed as one 250kg and two 60kg bombs, though possibly not at the same time). Not quite as lethal as the 1000lb , but still more boom than the 250kg used against the US carriers in OTL.

About Ki-100 and A6M8, they may not be spectacular by 1943 standards, but far better to have them in 1943 than not, although given that the 1500HP MW boosted Kinsei was only in prototype form in 1943, it's difficult to see how they can get in ready that early even if they drop the DB, besides Mitusbishi was developing the Kinsei, not Aichi or Kawasaki, although theoretically they might help if free from other design work.

 

[tomo pauk]

About Ki-100 and A6M8, they may not be spectacular by 1943 standards, but far better to have them in 1943 than not, although given that the 1500HP MW boosted Kinsei was only in prototype form in 1943, it's difficult to see how they can get in ready that early even if they drop the DB, besides Mitusbishi was developing the Kinsei, not Aichi or Kawasaki, although theoretically they might help if free from other design work.

1500 HP Ha 109 for the Japanese Fw 190, available in 1941.

 

[HoHun]

Hi Tomo,

The decisions to keep the 1000-1100 HP engines on a lot of 1st line aircraft even by 1943 is cringeworthy. Time and opportunity lost with Aichi licence-building the DB 601. No 2-stage supercharged nor trubo-supercharged engines is also a big problem.

Not that I have much actual data to go by, but my feeling is that you might be over-estimating the Japanese industrial capacities.

These reports are pretty revealing:

http://www.wwiiaircraftperformance.org/japan/ATIG-Report-24.pdf

http://www.wwiiaircraftperformance.org/japan/ATIG-Report-39.pdf

http://www.wwiiaircraftperformance.org/japan/ATIG-Report-45.pdf

My impression that the Japanese were basically limited by their very modest and fairly young industrial base that couldn't scale up anywhere fast enough to meet the requirements of an all-out war.

I'm not sure the attempt to license-built German aircraft would actually have been realistically feasible either, as one needs a lot of supporting industries and suppliers to build not just an airframe but a weapons system. I'd speculate that the amount of re-design required to make an aircraft fit for production by the Japanese industry might actually have been excessive, at least for state-of-the-art frontline types.

Of course, whether the path the Japanese historically took is sensible is another question ... even without the benefit of hindsight, a greater standardization of types could probably have been recognized as necessary to allow for more efficient production, as the learning curve models at the time were well-established.

However, even in WW2 Germany, the capability of the machine tool industry was a limiting factor for other industries, and I wouldn't be suprised if Japan ran into such a limitation even earlier. In that case, I'd assume that aircraft production was more or less characterized by craftmanship methods, which in turn means that mass production scale effects would have been lesser in scale than they would have been with a more industrialized approach. Accordingly, producing a large variety of types might not have been as bad as it might appear.

In "Neven, Herz und Rechenschieber" by Conradis I just read some figures showing that at Focke-Wulf the engineering man hours expended on machine tools far exceeded those expended on aircraft design, but unfortunately I can't find these figures right now as the book doesn't have an index and is not all that well structured if you mean to find something.

The reason I'm mentioning this is that if you have an aircraft industry relying more on artisanal methods than on machine tools, even the engineering resources might not be as badly affected by the production of a large number of types as it would be in a more mature and more productive industry. Of course, from the history of Mitsubishi we know that the Japanese were a bit short on engineering manpower anyway, so these considerations are not meant to dismiss the issue, just to give a possible perspective on the scale of its impact.

Please regard my post as mostly speculative, but maybe it's of interest anyhow. Personally, I'd certainly like to learn more about this!

Regards,

Henning (HoHun)

 

[tomo pauk]

Not that I have much actual data to go by, but my feeling is that you might be over-estimating the Japanese industrial capacities.

These reports are pretty revealing:

http://www.wwiiaircraftperformance.org/japan/ATIG-Report-24.pdf http://www.wwiiaircraftperformance.org/japan/ATIG-Report-39.pdf http://www.wwiiaircraftperformance.org/japan/ATIG-Report-45.pdf
My impression that the Japanese were basically limited by their very modest and fairly young industrial base that couldn't scale up anywhere fast enough to meet the requirements of an all-out war.

The reason why I'm championing the Fw 190 is exactly the thing of Japan having not the 1st rate industry, while trying to introduce a myriad of 1-task designs. Eg. Army was introducing one bespoke fighter design each year from 1939 on. We have Nakajima manufacturing 3 separate fighter types in almost every month from early 1941 to the late 1944 in a single factory. Kawanishi making like 5 separate floatplane designs with overlapping features was also an self-inflicted wound. That kills any ability to take the advantage of lowering the manufacturing manhours for something that is in series production.

I'm not sure the attempt to license-built German aircraft would actually have been realistically feasible either, as one needs a lot of supporting industries and suppliers to build not just an airframe but a weapons system. I'd speculate that the amount of re-design required to make an aircraft fit for production by the Japanese industry might actually have been excessive, at least for state-of-the-art frontline types.

We can take a look at the C6N - a much more advanced aircraft than the simple and effective Fw 190. In house designed and produced by Nakajima

However, even in WW2 Germany, the capability of the machine tool industry was a limiting factor for other industries, and I wouldn't be suprised if Japan ran into such a limitation even earlier. In that case, I'd assume that aircraft production was more or less characterized by craftmanship methods, which in turn means that mass production scale effects would have been lesser in scale than they would have been with a more industrialized approach. Accordingly, producing a large variety of types might not have been as bad as it might appear.

Germany have had a surplus of machine tools, while the acute deficit of manpower and raw materials was present. Such a surplus it was that many factories were working in two or just one shift, despite the wide scale usage of women and slave workers.
For 1941-45, number of machine tools in Germany was on par with number of machine tools in the USA (per this doc), despite the much lower number of workers Germany had, let alone despite the appalling access to the raw materials.
There is even a doc that claims that Germany have had more machine tools than USA, UK, France and Italy combined here.

 

[BB1984]

It's not clear to me why they would bother with Fw190 or Bf109 when they could have had the both the A6M8 version of the Zero and the Ki-100 available in 1942 if they had just been able to speed up Kinsei development to get a 1500 HP version in 1942 (not a big leap if the resources put into the DB601 had gone into Kinsei development instead).

Performance of Ki 100 was unimpressive by 1943 standards, so was that of the A6M8; even the A6M3 offered almost same turn of speed by mid-1942. Fw 190 can use the Ha 109 (already in production by mid 1941) and perform much closer to the Ki-44-II, rather than languish in 360 mph zone as the Ki 100 and A6M8 did.
Bf 109 was a much smaller aircraft than Zero or Ki-100, so we can expect it to out-perform those on same engine.

Ref the A6M8: it's carrier capable. It would give a substantial improvement over the earlier versions of the Zero while waiting for the A7M Reppū. There was no German carrier capable fighter to build instead of the A6M or the A7M.

Ref the K-100, yes it's a little slow, but it's still a massive improvement that could have been available in 1942 and, as a lot of Pacific combat showed, there was more to combat than speed. There's at least some evidence the Japanese regarded the Ki-100 as superior overall to the Ki-84, which was, in turn, regarded as competitive with the P-47 and P-51.

• Ref superior to the Ki-84: "During March and April they would fly the Ki-100 in comparison tests against the most capable Japanese fighter then in service, the Ki-84 "Frank". After extensive testing . . . it stated that given equally skilled pilots, the Ki-100 would ALWAYS win a fight with the Ki-84 in any one-to-one combat. ."
  • For full quote / sourcing see this page and scroll all the way down to the last post: http://www.arcforums.com/forums/air...rmance-accounts/&tab=comments#comment-2963972
• Ref the Ki-84, see the conclusions page of this report: http://www.wwiiaircraftperformance.org/japan/T-2_Report_on_Frank_I_Ki-84.pdf
• Note that I'm not suggesting these sources are definitive proof of anything, just that it's an indication that the Ki-100 fought much better than a simple top speed comparison is going to suggest.

 

[tomo pauk]

Ref the K-100, yes it's a little slow, but it's still a massive improvement that could have been available in 1942 and, as a lot of Pacific combat showed, there was more to combat than speed. There's at least some evidence the Japanese regarded the Ki-100 as superior overall to the Ki-84, which was, in turn, regarded as competitive with the P-47 and P-51.

• Ref superior to the Ki-84: "During March and April they would fly the Ki-100 in comparison tests against the most capable Japanese fighter then in service, the Ki-84 "Frank". After extensive testing . . . it stated that given equally skilled pilots, the Ki-100 would ALWAYS win a fight with the Ki-84 in any one-to-one combat. ."
  • For full quote / sourcing see this page and scroll all the way down to the last post: http://www.arcforums.com/forums/air...rmance-accounts/&tab=comments#comment-2963972

Thanks for the link.
One of reasons the Ki-84 was regarded competitive vs. P-51 and P-47 was the speed of the Japanese fighter. Americans clocked more than 420 mph on the Ki-84.
If the Japanese pilot flying the Ki-84 plays to the strengths of a light opponent - engage in a turning fight - he is bound to loose that fight. Opening the throttles on the Ki-84 is a way forward, just like it was the case with Hellcat or Lighting battling the Zero, in order to disengage and then engage with help of the superior speed.*
A Ki-100 can't catch any Allied fighter aware of it that is faster than Spitfire V, or the Mosquito. Ki-84 stands good chances there.

• Ref the Ki-84, see the conclusions page of this report: http://www.wwiiaircraftperformance.org/japan/T-2_Report_on_Frank_I_Ki-84.pdf
• Note that I'm not suggesting these sources are definitive proof of anything, just that it's an indication that the Ki-100 fought much better than a simple top speed comparison is going to suggest.

What I'm reading are the praises for the Ki-84, with remarks on lack of durability due to not having primed surfaces, along with imperfections one can only expect on a late-war Japanese fighter.
Ki-100 was IMO a good job of making a lemonade when the lemons were handed. Too bad the Japanese didn't install the Ha 109 on the 'not Ki-61' already in 1941.

* German pilot was doing that with Bf 109E-7 in Japan, angering the Japanese to no end. At the end, that experience saved the Ki-44 project, the only Japanese Army fighter that was able to emulate the 'boom and zoom' tactics the 109 was well suited for.

 

[HoHun]

Hi Tomo,

One of reasons the Ki-84 was regarded competitive vs. P-51 and P-47 was the speed of the Japanese fighter. Americans clocked more than 420 mph on the Ki-84.

I don't think 422 mph @ 21,000 ft was a speed actually achieved in any US test as it comes up right in the first performance analysis distributed in the TAIC intellegence data sheets, where it's clearly indicated as being based on a drag analysis of the Ki-43 (obviously combined with the power curve of the more powerful engine the Ki-84 was known to use).

These data sheets went through a couple of revisions - see attachments -, but I believe the only change was a small adjustment of critical altitudes at some point.

The Ki-84 was indeed flown in the US, but it seems that only general handling and characteristics were covered. The respective report (which can be found on wwiiaircraftperformance.org) points out that even the general handling tests were hampered by repeated failures of the (poor quality) exhaust stacks, and testing for performance would probably put a lot more stress on these.

So, considering that the aircraft was not in a good condition for performance testing, and the fact that we have documents on general testing and engine overhaul, but not on performance testing, while the test figures allegedly achieved in US testing are exactly the same as the numbers calculated from the very early intelligence estimate derived without knowledge of what the Ki-84 actually looks like, my conclusion is that they can't be considered to be reliable.

There is a number of Japanese tests as well, but they were from the developmental phase in which the type that might not have reached the full potential of airframe and engine yet, but my overall impression is that realistically, the Ki-84 probably wasn't able to reach the performance numbers from the TAIC estimates.

* German pilot was doing that with Bf 109E-7 in Japan, angering the Japanese to no end. At the end, that experience saved the Ki-44 project, the only Japanese Army fighter that was able to emulate the 'boom and zoom' tactics the 109 was well suited for.

That would be Erwin Leykauf, I believe? Do you have any pointers where I can read up about the connection to Ki-44 development? That sounds like a highly interesting story!

Regards,

Henning (HoHun)

 

[tomo pauk]

That would be Erwin Leykauf, I believe? Do you have any pointers where I can read up about the connection to Ki-44 development? That sounds like a highly interesting story!

This video seems like a well-researched one.

 

[lancer21]

Very interesting video, i was puzzled by the mention of a Ki-27-II though. I never heard about such a variant before. Anyone knows more? Also it's curious there is no mention of Ki-43 being tested against the 109E, unless Ki-27-II is a cover designation for Ki-43 for some reason.
I think though we'll drifting into IJAAF too much though, so perhaps another dedicated IJAAF topic would be a better place to discuss related what-ifs?

 

[tomo pauk]

I think though we'll drifting into IJAAF too much though, so perhaps another dedicated IJAAF topic would be a better place to discuss related what-ifs?

Good point. I'll start a new thread, Army Air service specific.

 

[BB1984]

One of reasons the Ki-84 was regarded competitive vs. P-51 and P-47 was the speed of the Japanese fighter. Americans clocked more than 420 mph on the Ki-84 . . .

Ki-100 was IMO a good job of making a lemonade when the lemons were handed. Too bad the Japanese didn't install the Ha 109 on the 'not Ki-61' already in 1941.

Ref speed:

• the Ki-100's lower speed meant that it ceded the initiative to faster fighters and I agree that was a big deal.
• My point is that once the engagement starts the Ki-100 seemed capable and I can't find a detailed evaluation but it seems like its dive capability was good which might make boom and zoom more problematic than vs., for instance, a Zero.
• Also, in my "what if" timeline, the Ki-100 in '44-45 would have been developed into a Ki-100B with the Mitsubishi's MK9 (Ha-43), the linear development of the Kinsei into an 18 cylinder version comparable in power to the Nakajima Homare installed in the Ki-84. This would have at least considerably decreased any speed gap between the Ki-84 and the Ki-100.

Ref lemons out of lemonade and why didn't they do it sooner: agree 100%

 

[lancer21]

Regarding the Ki-84 speed, indeed the american figures are too high, iirc in japanese wiki it says the speed of a fully rated Ki-84 was 640-650kph. The lower figure of 624-631 kph might be because the engine was derated (similar to what the germans had to do).

Same discrepance i found for the N1K2-J, iirc the highest figure i saw was 644kph, though i think i also saw 620kph. The usual figure as you know is given as just 595kph, which i always found inexplicably low, but if the engine was derated that makes sense. On the other hand, due to the war situation (poor fuel, poor metals/building quality), how many japanese fighters would have performed to their full potential, especially the 2000HP ones?

 

[tomo pauk]

Same discrepance i found for the N1K2-J, iirc the highest figure i saw was 644kph, though i think i also saw 620kph. The usual figure as you know is given as just 595kph, which i always found inexplicably low, but if the engine was derated that makes sense.

Similar situation was with the J2M: Allied sources say ~650 km/h (even 670 for the 'Jack 21'), Japanese put it at around 600 km/h.

 

[HoHun]

Hi Tomo,

The reason why I'm championing the Fw 190 is exactly the thing of Japan having not the 1st rate industry, while trying to introduce a myriad of 1-task designs. Eg. Army was introducing one bespoke fighter design each year from 1939 on. We have Nakajima manufacturing 3 separate fighter types in almost every month from early 1941 to the late 1944 in a single factory. Kawanishi making like 5 separate floatplane designs with overlapping features was also an self-inflicted wound. That kills any ability to take the advantage of lowering the manufacturing manhours for something that is in series production.

You might be right, but creating "bespoke" designs comes with the advantage that you can optimize it for one task and thus get better performance than you would from a multi-purpose design that inevitably has to make compromises - which could be a way to compensate for inferior technology.

With regard to the Army fighters, I suspect the continuation of Ki-43 production really was necessary because engine production couldn't just switch over to more advanced engines while maintaining the fighter production rate, especially when the new engines were still having teething troubles.

We can take a look at the C6N - a much more advanced aircraft than the simple and effective Fw 190. In house designed and produced by Nakajima

What would the conclusion be? I don't quite understand what you're aiming at here, though I fully agree the Fw 190 was a simpler design in many of its features.

Germany have had a surplus of machine tools, while the acute deficit of manpower and raw materials was present. Such a surplus it was that many factories were working in two or just one shift, despite the wide scale usage of women and slave workers.

I have to admit I wasn't aware that there actually was a surplus of machine tools. However, the machine tool industry as such was a bottle neck as far as I know, since there definitely was a lack of the highly-skilled workers this industry required.

The reason I mentioned this was to point out that maybe the Japanese had a similar bottle neck in their machine tool industry, which would of course slowed any plans to achieve efficient mass production. Still, it might have been the best way to go for them ... not that it would have made any difference to the final outcome, of course.

Regards,

Henning (HoHun)

 

[tomo pauk]

You might be right, but creating "bespoke" designs comes with the advantage that you can optimize it for one task and thus get better performance than you would from a multi-purpose design that inevitably has to make compromises - which could be a way to compensate for inferior technology.

With regard to the Army fighters, I suspect the continuation of Ki-43 production really was necessary because engine production couldn't just switch over to more advanced engines while maintaining the fighter production rate, especially when the new engines were still having teething troubles.

Half a dozen of bespoke 1-engine day fighters have had the same tasks - air defence (definitely) and air superiority (hopefully).
Ha 109 of 1941 was superior to a Sakae of 1944 or 1945 (and as in the ballpark with water-injected Kinsei of 1944-45), no teething troubles - at least no as far as I know - yet the decision was to axe the Ha 109 in 1944. Makes as much sense as cancelling the Merlin and carry on with Kestrel in 1939.

What would the conclusion be? I don't quite understand what you're aiming at here, though I fully agree the Fw 190 was a simpler design in many of its features.

I'm pointing out to the Japanese designers being able to came out with a design that pushes the state of the art, and the factories actually making these A/C (small numbers of A/C produced notwithstanding). Production of the Fw 190 was well within abilities of Japanese companies.

 

[HoHun]

Hi Tomo,

Half a dozen of bespoke 1-engine day fighters have had the same tasks - air defence (definitely) and air superiority (hopefully).

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

Thus structured, there's not all that much redundancy in it if you accept that there is a justification for carrier aircraft to be different from land-based aircraft. One might have done without different types, as the British did, but I'm not sure even they wouldn't have been better off with dedicated types.

The Ki-44 preceded the Ki-61, and I believe it was considered a bit of an experiment, explaining this redundancy. The J2M on the other hand might be seen as a duplication of effort.

The N1K-J was a coincidental development from a floatplane that turned out very well, and I'm not sure it would have been wise to cancel it. The A7M again was a carrier aircraft, but of course, it came too late.

Ha 109 of 1941 was superior to a Sakae of 1944 or 1945 (and as in the ballpark with water-injected Kinsei of 1944-45), no teething troubles - at least no as far as I know - yet the decision was to axe the Ha 109 in 1944. Makes as much sense as cancelling the Merlin and carry on with Kestrel in 1939.

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.

Regards,

Henning (HoHun)

 

[lancer21]

From what i can read around one of the reasons the Ha-109 was cancelled was because of the priority for Homare/Ha-45 production.
As much as i like the dumpy N1K1-J (i refer at this version specifically, separate from the later N1K2-J), it was a rushed design, due to it's configuration optimized for the float-fighter role, the landing gear had to be made excessively complicated and it was very fragile, the gun pods badly reduced speed, the engine was unreliable, so it can't be seen as much of a success imo. So for ATL purposes like i said earlier they really should have designed the whole Shiden family with a low wing from the start like the N1K2-J, floats or no floats, at least they would have saved themselves some time and trouble. So without the need to redesign it and hence change the production line, they can perhaps build about 2000 of them 1943-1945 instead of about 1500 in OTL.

By cancelling the J2M an earlier A7M could be built as a prototype at least in 1942, powered by the Homare until the MK9A is ready (but they must give full backing for this engine, i'm sure you are aware of the sad comedy of Homare and MK9 engines for A7M, Horikoshi was desperate to get the MK9 for it, the navy was adamant it wouldn't have anything but a Homare on the A7M) the OTL A7M was indeed underpowered with the Homare, but i believe that by using a smaller wing (discussed during design, they were debating a wing loading of either 130 or 150kg/m2, they chose the larger wing in OTL, difference in speed was assessed as 19kph), and trimming down weight as much as possible, they could perhaps get it close to 600 kph in speed, just enough to make it at least competitive with the F6F-3. The production of this early A7M could start in 1943 and be available in some numbers in 1944 for Kido Butai. So perhaps they could build about 1000 A7Ms instead of the OTL 700 or so J2M, if they give it full backing.

 

[tomo pauk]

As much as i like the dumpy N1K1-J (i refer at this version specifically, separate from the later N1K2-J), it was a rushed design, due to it's configuration optimized for the float-fighter role, the landing gear had to be made excessively complicated and it was very fragile, the gun pods badly reduced speed, the engine was unreliable, so it can't be seen as much of a success imo. So for ATL purposes like i said earlier they really should have designed the whole Shiden family with a low wing from the start like the N1K2-J, floats or no floats, at least they would have saved themselves some time and trouble. So without the need to redesign it and hence change the production line, they can perhaps build about 2000 of them 1943-1945 instead of about 1500 in OTL.

This, very much. Just make a no-nonsense fighter with a big radial engine (Kasei in this case) and produce it in series. If there is a better engine in next 18-24 months - great, re-engine it. Don't wait until late 1944 to have an actual, de-bugged, non-floatplane fighter in service.

 

[tomo pauk]

A better Zero: make it around the Kinsei from day one, and don't look back (yes, not a very original idea, but it has a lot of merit).
Protection for pilot and fuel is needed, too. Guns will need some tweaks, eg. the bigger ammo count for the cannon earlier, coupled with the earlier introduction of a HMG. The 'alt Zero' should make a good 'cushion' if the next-gen fighter is delayed.
From what I can gather, the Kinsei 46 as installed from August 1941 in the 'Mavis 22' was good for 1070 CV at 4200m; the earlier Kinseis like the 41 or 43 were low-level engines with 1080 HP at 2500m. By mid-1942, engine power vs. altitude went up significantly with the mark 51 to 54, 1100 CV at 6200 m, and with increase of power down low and for take-off. Improvements included a 2-speed supercharger, bigger impeller, slight increase of rpm for take-off; weight penalty was ~50 kg vs. the 40 series.

 

[lancer21]

Problem is the Kinsei engine will drastically reduce the range, as shown by the A6M8 compared to all the other Sakae powered Zeros, plus the fact that it has a diameter of 1,22m compared to 1,15m for Sakae would mean they will have to increase fuselage diameter if they still want the MGs to be in the cowling, which leads to a weight penalty etc. So me i'm not sure the Kinsei will make the early Zero a better machine, but i may be wrong i guess. Although i agree about increase ammo and a HMG asap. Also the short wing would help to increase dive speed.

If we go the Kinsei way, let's have the B5N powered by the Kinsei from the start too, in OTL the B5N1 was underpowered with the 840HP Hikari, but with the 1000/1070HP Kinsei it might be powerful enough to operate from the CVLs with full load. I guess this would also result in an undoubtely useful engine commonality for the main carrier planes A6M, D3A and B5N.

I wonder if there's any sort of data that shows the fuel consumption of the Kinsei and Sakae, to see how a Kinsei powered Zero might fare?

 

[tomo pauk]

Problem is the Kinsei engine will drastically reduce the range, as shown by the A6M8 compared to all the other Sakae powered Zeros, plus the fact that it has a diameter of 1,22m compared to 1,15m for Sakae would mean they will have to increase fuselage diameter if they still want the MGs to be in the cowling, which leads to a weight penalty etc. So me i'm not sure the Kinsei will make the early Zero a better machine, but i may be wrong i guess. Although i agree about increase ammo and a HMG asap. Also the short wing would help to increase dive speed.

MGs can go in the wings. Without the MGs and their ammo between the cockpit and engine, the fuel tanks can be installed there to cater for greater fuel consumption. Another thing is to make a 400L drop tank earlier than it was historically so.

 

[HoHun]

Hi Lancer21,

Problem is the Kinsei engine will drastically reduce the range, as shown by the A6M8 compared to all the other Sakae powered Zeros, plus the fact that it has a diameter of 1,22m compared to 1,15m for Sakae would mean they will have to increase fuselage diameter if they still want the MGs to be in the cowling, which leads to a weight penalty etc.

Is there an accepted (or at least reasonable) set of performance figures for the A6M8 one could use to extrapolate A6M1 performance with the Kasei engine?

Regards,

Henning (HoHun)

 

[tomo pauk]

@HoHun - perhaps the table from here?