A small what if: IJA goes with Ki-44 as their main fighter?

[tomo pauk]

Ki-44 as the basic airframe, that is.
The Ki-43 is phased out some time in 1943, Ki-27 is discontioued ASAP (it was produced until late in 1942), IJA says to Kawasaki 'err, we actually don't want V12 powered aircraft', Ki-84 is put on the back burner. Yes, the Pacific war still ends pretty much as it ended historically, but we might explore the plausible versions of the Ki-44, effect on air war in the Asia, possible Allied airforces' changes and tweaks etc.
Ki-44 airframe gets any engine suitable - Japanese have had a lot of handy radial engine types on disposal, and upgrade of armament as the war goes on.

 

[tomo pauk]

Ki-44 with Kinsei:
The 50 series are probably the 1st that can offer benefits for the Ki-44. Advantages over the Ha-41 is much better altitude performance, smaller diameter and a tad lower the weight. Ha-109 offers about the same altitude performance, but it weights another 110 kg more than 50 series Kinsei. Speed should've been a tad better than on the Ki-100?
Water-injected Kinsei 62, as used on late Dinahs, is even more interesting. W-I offered up to 270 HP; granted, benefits were limited to altitudes under ~19000 ft.
Series 40 Kinseis are of low-ish power (~1050 HP at 13800 ft per US data), but very light, so such powered Ki-44s would've been a bit faster than Ki-43-IIs due to it's much smaller wing? Should be diving better, too.

 

[Just Schmidt]

I'm not entirely sure what exactly 'putting Ki-84 on the back-burner' means, but if it implies slower development but somewhat later introduction of a more mature aircraft, that sounds reasonable enough. In 45 the Ki 44 will probably have become long in the teeth regardless.

I guess that many options for better engines exist, i trust you already indicated the most obvious. My two reservations is that the Ki-44 may not really have the range for escort, and that conservatism among pilots will result in the aircraft not being flown as much to its strengths as it should to really harvest the benefit.

Compared to the Ki-27 it is very much an improvement, even if the early Ki-44 I did not have as good performance as the II. In relation to the Ki-61 the IJAAF will have a more reliable fighter which should more or less average it in raw performance, but have significantly better reliability. And the German 20 mm machine cannons used on the Hien can be diverted, making an early improvement to hundreds of relatively early Ki-44's, which did not really have the punch that could be desired. That of course continues when home grown cannons becomes available, also if the need for those on the Ki-84 is less.

As for impact on the war I agree 100% that the ultimate outcome will not be altered. What may occur is a more resilient Japanese defense in primarily New Guinea and Burma, which conceivably could result in the earlier retirement of old allied types in these areas, somewhat delaying the build up of a useful fighter force in Europe. OTOH the allies may actually in practice be more committed to the official Europe first strategy, accepting that the roll back of the Japanese empire will take somewhat longer.

Then again, if one considers the war against Japan to consist of several competing campaigns, the allies may actually concentrate on the Island hopping and to a larger degree just contain the Japanese in New Guinea, Burma and the Phillipines. I don't see the allied campaign against Japanese merchant shipping suffering much in this scenario, nor the great naval battles unfolding much differently. The exception is of course Leyete Gulf, which may not happen at all.

With hindsight, the allies should probably concentrate as much on Europe as they did. After all, even a Japan left with more territory, more aircraft and more troops will probably be cowed by the atomic bombs. They will hardly be less hungry or short on fuel and strategic materials for their factories than historically was the case. But if aerial supremacy is not secured over France by the summer of 44, they may be used on Dresden instead if the Red Army haven't already gotten there in the summer of 45.

That is the biggest butterflies I dare to speculate about, if our charming little fighter receives the maximum priority at the earliest possible moment. I could very well be wrong.

 

[GrauGeist]

The KI-84 (which turned out to be one of Japan's most formidable fighters) was intended to replace the KI-43.
The KI-44 was not as nimble as the KI-43 and not as good as the KI-84, so why not accelerate the Shoki's development and get it into service as quickly as possible?

 

[tomo pauk]

I'm not entirely sure what exactly 'putting Ki-84 on the back-burner' means, but if it implies slower development but somewhat later introduction of a more mature aircraft, that sounds reasonable enough. In 45 the Ki 44 will probably have become long in the teeth regardless.

Putting the Ki-84 in the back burner might allow for improvements of Ki-44 to be done - engine and armament upgrades.tweaks in fuel tanks, protection, etc.
Ki-44 was a better performer than Ki-100, that materialized in 1945.

I guess that many options for better engines exist, i trust you already indicated the most obvious. My two reservations is that the Ki-44 may not really have the range for escort, and that conservatism among pilots will result in the aircraft not being flown as much to its strengths as it should to really harvest the benefit.

Range was probably not great with the reasonably powerful Ha-41/-109 engines. Slap in the nose something less powerful and less thirsty, like the 2-speed supercharged Sakae or Kinsei and range improves. Or, some extra fuel internal tankage and/or drop tanks.

The KI-84 (which turned out to be one of Japan's most formidable fighters) was intended to replace the KI-43.
The KI-44 was not as nimble as the KI-43 and not as good as the KI-84, so why not accelerate the Shoki's development and get it into service as quickly as possible?

Ki-44 Shoki was far better than Ki-84 Hayate from 1942 to the late 1944. Me, I'd have the Ki-44 up-engined with Homare ASAP.
As-is, Ki-44 was faster than Ki-43 (it will be faster even with same engine, since it was with considerably smaller wing), had far less restrictions when in dive, rolled faster (especially in high speed), was with better protection and had double the firepower.

 

[nuuumannn]

Putting the Ki-84 in the back burner might allow for improvements of Ki-44 to be done - engine and armament upgrades.tweaks in fuel tanks, protection, etc.

I'm curious what that might actually entail in real world situation, especially since each aircraft, the K-44 and the Ki-84 were built to two different requirements and were designed by the same design team led by the same designer. They weren't competitors and each was intended on fulfilling a separate role to one another. Surely it would not have made sense to focus development on one with one set of criteria and place less focus on the other for that reason. If this happened, the Ki-43 replacement would not have matured as it did within the time it did and the IJA, like the IJN with the A6M, would have lumbered with an older design being stretched to meet increasingly better enemy equipment.

The Ki-44 was not intended as the Ki-43 replacement; that was the Ki-84 as Dave pointed out, whereas the Ki-44 was considered a departure from traditional Japanese fighters in terms of its strengths in rate of climb and speed at the expense of manoeuvrability. It doesn't make sense to focus on one at the expense of another in this pair.

 

[tomo pauk]

The Ki-44 was not intended as the Ki-43 replacement; that was the Ki-84 as Dave pointed out, whereas the Ki-44 was considered a departure from traditional Japanese fighters in terms of its strengths in rate of climb and speed at the expense of manoeuvrability. It doesn't make sense to focus on one at the expense of another in this pair.

Let's say Ki-84 goes as-is.

 

[Kilkenny]

The KI-44-11 with four 20mm cannon should have begun replacing the Ki-43 in 1942 (completely replacing it by the end of 1943). Over this time, its engine should also have been more highly-tuned to improve its power (and thus top speed) and its supercharger improved by adding extra stages or speeds. Of course, if the IJA/IJN were really smart and worked together, after 1941 they should have concentrated only on the Kinsei and Kasei engines (and their 18-cylinder derivatives) at the expense of all other engines (even replacing the Sakae starting in 1942!). By 1945 the Juisei engine would have come online (and inserted in the Ki-44), thus skipping the horrendously unreliable Homare engine in the Ki-84 and other IJA/IJN aircraft.

 

[tomo pauk]

The KI-44-11 with four 20mm cannon should have begun replacing the Ki-43 in 1942 (completely replacing it by the end of 1943). Over this time, its engine should also have been more highly-tuned to improve its power (and thus top speed) and its supercharger improved by adding extra stages or speeds.

Nakajima did some of improvements already, the Ha 109 was development of the Ha 41, sporting a big S/C that was now with 2 speeds, and with straightened internals so it can rev faster.
Granted, a 2-stage supercharged Ha 109 would've been a very interesting engine, perhaps the Japanese copying idea from a F4F-3 or -4 captured/crashed with a working engine? The water-alcohol injection is also needed, the Japanese fuel octane rating was in shambles in 1944-45.

Of course, if the IJA/IJN were really smart and worked together, after 1941 they should have concentrated only on the Kinsei and Kasei engines (and their 18-cylinder derivatives) at the expense of all other engines (even replacing the Sakae starting in 1942!). By 1945 the Juisei engine would have come online (and inserted in the Ki-44), thus skipping the horrendously unreliable Homare engine in the Ki-84 and other IJA/IJN aircraft.

Sakae should've been indeed mostly phased-out by some time 1943, and produced only for aircraft where the Ha 109 or Kinsei don't fit. Ditto for Suisei.
Kinsei was worse than Ha 109 for high altitudes. The switch at Nakajima so they produce Mitsubishi's engines would've cost the Japanese dearly. What might be needed is to have Kawasaki and Aichi continue make radials only instead of DB 601 copies.
Homare is a known quantity; flatly assuming that Juisei will work flawlessly under the bad conditions of the last 12 months of
is not what I'd do.

 

[Kilkenny]

Nakajima did some of improvements already, the Ha 109 was development of the Ha 41, sporting a big S/C that was now with 2 speeds, and with straightened internals so it can rev faster.
Granted, a 2-stage supercharged Ha 109 would've been a very interesting engine, perhaps the Japanese copying idea from a F4F-3 or -4 captured/crashed with a working engine? The water-alcohol injection is also needed, the Japanese fuel octane rating was in shambles in 1944-45.



Sakae should've been indeed mostly phased-out by some time 1943, and produced only for aircraft where the Ha 109 or Kinsei don't fit. Ditto for Suisei.
Kinsei was worse than Ha 109 for high altitudes. The switch at Nakajima so they produce Mitsubishi's engines would've cost the Japanese dearly. What might be needed is to have Kawasaki and Aichi continue make radials only instead of DB 601 copies.
Homare is a known quantity; flatly assuming that Juisei will work flawlessly under the bad conditions of the last 12 months of
is not what I'd do.

Interesting/thoughtful comments... Perhaps if there were better production control for the Homare, it wouldn't have been so unreliable (and thus be fully competitive with the R-2800)... But it seems that most roads to better high alt. performance lead to the IJA/IJN not having good enough superchargers... I've read that the US turbo-superchargers were pretty unreliable, so perhaps if could/should have copied the Merlin's????...

 

[tomo pauk]

But it seems that most roads to better high alt. performance lead to the IJA/IJN not having good enough superchargers... I've read that the US turbo-superchargers were pretty unreliable, so perhaps if could/should have copied the Merlin's????...

US turbo-superchagers were very reliable past 1941. The control systems were sometimes misbehaving, that was sorted out by some time in 1942.
Copying the 2-stage S/C from Merlin 60 series is always a good idea. Japanese might capture the Wildcat's engine earlier than that of the Spitfire VIII?

 

[Shortround6]

The 2 stage supercharger is not the panacea that some people seem to think it was.

you have two things going with a 2 speed supercharger.
Yes you have much more boost going into the intake manifold.
You also have much more heat going into the intake manifold.
If you cannot control the heat (hotter intake charge) your gain in power is going to be minimal as the boost pressure will have to be restricted to control detonation.
The allies had the high performance fuel and the intercoolers and (on the radial) water injection to go with the two stage superchargers.

Trying to use two out of the 3/4 measures that gave the allies that performance is not going to give the level of performance got the allies got.

Look at the P-63, even using 100/300 fuel and a lot of water injection the two stage super charger on the P-63 moved the Full throttle height from 15,000 to to 25,000(Or a bit less). Very useful but well over one year compared to a Merlin 61.
Now try using 92 octane (or 96 or?) fuel in the two stage supercharger had run the intake manifold temperature a few hundred degrees hotter?

Yes you can more performance than the single stage supercharger and maybe that will enough for some of the interceptors to get into firing position to shoot at bombers.
You need a lot more to actually fight American fighters at 25,000-30,000.

 

[Kilkenny]

US turbo-superchagers were very reliable past 1941. The control systems were sometimes misbehaving, that was sorted out by some time in 1942.
Copying the 2-stage S/C from Merlin 60 series is always a good idea. Japanese might capture the Wildcat's engine earlier than that of the Spitfire VIII?

Wow; you know a lot... So please tell me what "highly tuned" means... Tighter clearances/higher compression? Better lubricants? Better ignition? Better engine and oil cooling? I read that the Sakae was relatively highly tuned, while the Kinsei gradually became less well-tuned; and the Homare, too...

 

[tomo pauk]

Wow; you know a lot... So please tell me what "highly tuned" means... Tighter clearances/higher compression? Better lubricants? Better ignition? Better engine and oil cooling? I read that the Sakae was relatively highly tuned, while the Kinsei gradually became less well-tuned; and the Homare, too...

I don't use the term "highly tuned". Seems too vague.

The 2 stage supercharger is not the panacea that some people seem to think it was.

you have two things going with a 2 speed supercharger.
Yes you have much more boost going into the intake manifold.
You also have much more heat going into the intake manifold.
If you cannot control the heat (hotter intake charge) your gain in power is going to be minimal as the boost pressure will have to be restricted to control detonation.
The allies had the high performance fuel and the intercoolers and (on the radial) water injection to go with the two stage superchargers.

We know that 2-stage supercharging worked with 87 oct fuel if the compression was kept at modest levels (6.5:1 on the Jumo 213E and F), and if there was an intercooler (213E) or the water-alcohol injection was used (both 213E and 213F). Japanese were using water injection, however their superchargers in wartime service were firmly in the 1-stage land.
(power chart for the Jumo 213F posted here, scroll down a bit)

Look at the P-63, even using 100/300 fuel and a lot of water injection the two stage super charger on the P-63 moved the Full throttle height from 15,000 to to 25,000(Or a bit less). Very useful but well over one year compared to a Merlin 61.
Now try using 92 octane (or 96 or?) fuel in the two stage supercharger had run the intake manifold temperature a few hundred degrees hotter?

It was IIRC a jump to 22500 ft for the 1st gen of 2-stage V-1710s vs. the latest V-1710s with 1-stage S/C that topped at 15000 ft. A major increase (7500 ft) in anyone's book.

Yes you can more performance than the single stage supercharger and maybe that will enough for some of the interceptors to get into firing position to shoot at bombers.
You need a lot more to actually fight American fighters at 25,000-30,000.

1st step might be that IJA admits to themselves that Ki-43 and Sakae are obsolete by late 1943, and that copy of DB 601 is late by now.

 

[Kilkenny]

I don't use the term "highly tuned". Seems too vague.



We know that 2-stage supercharging worked with 87 oct fuel if the compression was kept at modest levels (6.5:1 on the Jumo 213E and F), and if there was an intercooler (213E) or the water-alcohol injection was used (both 213E and 213F). Japanese were using water injection, however their superchargers in wartime service were firmly in the 1-stage land.
(power chart for the Jumo 213F posted here, scroll down a bit)



It was IIRC a jump to 22500 ft for the 1st gen of 2-stage V-1710s vs. the latest V-1710s with 1-stage S/C that topped at 15000 ft. A major increase (7500 ft) in anyone's book.



1st step might be that IJA admits to themselves that Ki-43 and Sakae are obsolete by late 1943, and that copy of DB 601 is late by now.

IM0, the Ki-44 should have begun replacing the Ki-43 in 1942... And Kinsei-powered Zeros (ala the A6M8) should have started replacing Sakae-powered Zeros by the end of that year.. The Sakae was a light, long-range carrier plane well-suited for the offensive operations of 1942, but thereafter the IJN needed a plane with an engine more capable of carrying armour, bigger guns, etc. And with refinement of its engine, the Shoki might have been almost as good as the J2M Raiden (which didn't go into service until two years later---- way too late).

 

[SaparotRob]

Weren't they trying to do just that and they may have had too many things on their plate? It's not like they could just duck out and use NACA's wind tunnel when theirs were busy or burn gallons of high octane for testing engines. Wasn't Jiro Horikoshi hospitalized with fatigue from designing new planes and updating old ones? I'm thinking he probably wasn't the only one. As you can tell I'm not up on this stuff.

 

[tomo pauk]

1) Weren't they trying to do just that and they may have had too many things on their plate? 2) It's not like they could just duck out and use NACA's wind tunnel when theirs were busy or burn gallons of high octane for testing engines. 3) Wasn't Jiro Horikoshi hospitalized with fatigue from designing new planes and updating old ones? I'm thinking he probably wasn't the only one. As you can tell I'm not up on this stuff.

1) That was the exact problem - flood of separate designs coming basically one year after another. Eg. Nakajima was making 3 fighter types in 1941-44 for the Army - yes, the old Ki-27 was still being made in December of 1942. All in one factory. Ki-43 was still being made in August of 1945 (not by Nakajima anymore, but still), while the Ki-44, a fighter far more suited for modern air combat, was phased out in 1944. (shaking my head in disbelief)
Nakajima was also making Zeros, they made more Zeros than Mitsubishi.
2) Japanese aircraft were reasonably streamlined. What was not there was engine power above 20000 ft. Lack of hi-octane fuel can be circumvented by a good deal with water-alcohol injection, however there was no circumventing the lack of modern superchargers or turbochargers the West had in use.
3) Mitsubishi (where Jiro Horikoshi was working) was not making fighters for the IJA. IJN mis-guided purchase policy is a topic of their own (a big topic).

 

[SaparotRob]

1) That was the exact problem - flood of separate designs coming basically one year after another. Eg. Nakajima was making 3 fighter types in 1941-44 for the Army - yes, the old Ki-27 was still being made in December of 1942. All in one factory. Ki-43 was still being made in August of 1945 (not by Nakajima anymore, but still), while the Ki-44, a fighter far more suited for modern air combat, was phased out in 1944. (shaking my head in disbelief)
Nakajima was also making Zeros, they made more Zeros than Mitsubishi.
2) Japanese aircraft were reasonably streamlined. What was not there was engine power above 20000 ft. Lack of hi-octane fuel can be circumvented by a good deal with water-alcohol injection, however there was no circumventing the lack of modern superchargers or turbochargers the West had in use.
3) Mitsubishi (where Jiro Horikoshi was working) was not making fighters for the IJA. IJN mis-guided purchase policy is a topic of their own (a big topic).

I know Jiro Horikoshi worked for Mitsubishi (read his book, saw some documentaries, love the cartoon!) but I'm guessing his counterparts at Nakajima, Aichi, Kawanishi, etc were in the same predicament. And now I know that problems were exacerbated by building everything under one roof! Not a Willow Run sized roof either.

 

[tomo pauk]

I know Jiro Horikoshi worked for Mitsubishi (read his book, saw some documentaries, love the cartoon!) but I'm guessing his counterparts at Nakajima, Aichi, Kawanishi, etc were in the same predicament. And now I know that problems were exacerbated by building everything under one roof! Not a Willow Run sized roof either.

I also believe those designers and engineers were overworked. Many times the aircraft they designed were produced in just a several dozen or several hundred of copies. Eg. Nakajima, the #1 manufacturer of airframes, produced less than 20000 aircraft in IIRC two factories (one for Army, another for Navy needs) from January of 1941 and mid August of 1945.

 

[Shinpachi]

If I may improve Nakajima Ki-44 as a main fighter for IJA, I will recommend Mitsubishi Ha-43 (A20) engine for 2,000hp which was developed based on the Kinsei. This engine was mystery for me for a long time as few productions but, in research for my coming CGI project J7W1, I have been convinced that this is merely a downsized version of Ha-42(A18) which was based on Kasei and so reliable unlike Nakajima Ha-45(Homare). There will be no problem to rely on this engine.

A20

A18