Ki-46-III KAI/Ki-46-IV: Wasted Potential? What would you change/fix?

[Airborne2001]

NOTE: My photos are sourced from this WarThunder suggestion, which happens to be from the Aireview magazine/book:

Mitsubishi Ki-46-IVb

Mitsubishi Ki-46-IVb History: Four prototypes of the Ki-46-IV were developed between 1943 and 1944, retaining the Ki-46-III’s airframe but upgraded with Ha-112-II Ru engines. These engines included exhaust-driven turbosuperchargers, allowing for impressive high-altitude capabilities with a...

forum.warthunder.com

The Ki-46 was arguably Japans top reconnaissance aircraft. It was noted for being very fast with a good service ceiling compared to other types, so naturally it got turned into an interceptor and ground attack aircraft. While the recon types were phenomenal, the combat types were a bit of a disappointment. The type was truly only given an ability to hold an armament without much modification to make it behave more like a combat aircraft. As a result, it didn't have enough armor (though you could say that for most Japanese aircraft of WWII), it didn't climb well enough to properly engage the B-29, and a 37mm upright cannon it didn't have good stability. There were other issues, but this is the basic idea.

The Tachikawa Ki-70 was supposed to replace it in the recon role, but the prototype ended up not showing much over the Ki-46-III. The Ki-70 was thus cancelled. To compensate, the Ki-46-IV was created. This variant featured turbocharged Kinsei engines, and it had quite a bit of potential. The only major issue were some problems with turbocharger reliability, but that aside it was a strong performer. With good tailwinds a Ki-46-IV averaged ~700kph (~435mph) at high altitude! The climb rate was also better than the Ki-46-II, which was the lightest operational variant. It was planned to make recon (ko) and interceptor/ground attack (otsu) variants of the plane, but in addition to the engine problems it seems like it never got as much priority as designs like the Ki-108 and Ki-93. This all said though, as far as I'm aware there were no major changes to the airframe again to adapt it for combat roles (other than armament, obviously.)

Do you think there is wasted potential here that could've been put to good use? What changes would you make to the III and IV to make it better in combat roles?

Here are some technical information charts:

Here are some other sources I've used for info:

Mitsubishi Ki-46 'Dinah'

The Mitsubishi Ki-46 'Dinah' was the Japanese Army's main reconnaissance aircraft of the Second World War, and was one of the most aerodynamically perfect aircraft of its era.

www.historyofwar.org

Mitsubishi Ki-46 - Wikipedia

en.wikipedia.org

 

[Shortround6]

With good tailwinds a Ki-46-IV averaged ~700kph (~435mph) at high altitude!

A Hurricane I with good tailwinds averaged just over 400mph on a cross-country flight.
Nobody believes that a Hurricane was really a 400mph fighter.
I will note that a P-38J was good for 413.4mph at 30,000ft using 1312hp per engine.
P-38 was significantly heavier but slightly smaller (wing area and frontal area).

Playing bomber interceptor may have worked. Playing either fighter or ground attack may not have gone so well. How many "G"s was the Ki-46 supposed to withstand?
B-29s do not do high G maneuvers. Trying to fight P-47s or P-51s may not go well for light twin (Mosquito was only supposed to do 5 "G"s).
B-25s and B-26s were only good for about 4 "G"s and that is with a lot of fuel and the bombs already dropped. Japanese AA sucked. It did cause losses but similar attacks in Europe were seldom done against the German Flak. Single engine aircraft were preferred for both speed and agility.
The Ki-46 did it's job of recon plane very well but recon planes seldom use High "G" maneuvers.

Can the Japanese actually produce turbo chargers in quantity that actually work (last) although turbos are only needed for high altitude work.
Ki-46 was only drafted into the interceptor roll because the Japanese army screwed up the Ki-96 and Ki-102/108 programs.

Ki-46 IV used methanol to help cool the intake air as they didn't have space for intercoolers.
How long was the methanol good for in combat?

You can develop a lot of things. But things like real intercoolers can mean more drag.

Japanese development in late 1944 and 1945 was sometimes influenced was bombing raids and earthquakes affecting factories.

 

[Airborne2001]

A Hurricane I with good tailwinds averaged just over 400mph on a cross-country flight.
Nobody believes that a Hurricane was really a 400mph fighter.
I will note that a P-38J was good for 413.4mph at 30,000ft using 1312hp per engine.
P-38 was significantly heavier but slightly smaller (wing area and frontal area).

Playing bomber interceptor may have worked. Playing either fighter or ground attack may not have gone so well. How many "G"s was the Ki-46 supposed to withstand?
B-29s do not do high G maneuvers. Trying to fight P-47s or P-51s may not go well for light twin (Mosquito was only supposed to do 5 "G"s).
B-25s and B-26s were only good for about 4 "G"s and that is with a lot of fuel and the bombs already dropped. Japanese AA sucked. It did cause losses but similar attacks in Europe were seldom done against the German Flak. Single engine aircraft were preferred for both speed and agility.
The Ki-46 did it's job of recon plane very well but recon planes seldom use High "G" maneuvers.

Can the Japanese actually produce turbo chargers in quantity that actually work (last) although turbos are only needed for high altitude work.
Ki-46 was only drafted into the interceptor roll because the Japanese army screwed up the Ki-96 and Ki-102/108 programs.

Ki-46 IV used methanol to help cool the intake air as they didn't have space for intercoolers.
How long was the methanol good for in combat?

You can develop a lot of things. But things like real intercoolers can mean more drag.

Japanese development in late 1944 and 1945 was sometimes influenced was bombing raids and earthquakes affecting factories.

I think one of the main things Japan could've done is the basic of giving it self-sealing fuel tanks. One of the issues with the Ki-46-III KAI interceptor was its lack of stability due to the oblique 37mm cannon. Personally, while I get why they did it, I think a 37mm is a bit extreme. Downsizing to a 30mm or even 20mm would still be decent. In fact, the Ki-46-III Hei was going to do this, but it never got built... I do agree though that the ideal choice would've been the various Ki-45 successors if the army didn't slack with the constant requirement changes.

 

[tomo pauk]

Shed some fuel for the starters? The 'Dinah 3' was supposed to be carrying up to almost 3000 lbs (~500 US gals) of internal fuel - just a ticket for a recon bird, but a too much for a wannabee fighter with 2 x 1500 HP. Carrying just 300 US gals means 1200 lbs less weight, or about 10% less of the loaded weight of a recon bird (maxed at ~12400 lbs). Only one crew member, no rear gun = 200+ lbs less.
Use the weight saved to introduce the s-s tanks, firepower, and reinforcements of the airframe.

 

[Airborne2001]

Shed some fuel for the starters? The 'Dinah 3' was supposed to be carrying up to almost 3000 lbs (~500 US gals) of internal fuel - just a ticket for a recon bird, but a too much for a wannabee fighter with 2 x 1500 HP. Carrying just 300 US gals means 1200 lbs less weight, or about 10% less of the loaded weight of a recon bird (maxed at ~12400 lbs). Only one crew member, no rear gun = 200+ lbs less.
Use the weight saved to introduce the s-s tanks, firepower, and reinforcements of the airframe.

Good call on the fuel reduction! I forgot to mention it, but yeah getting rid of the second crew member would also help to lower the weight a bit. I completely agree that those changes could allow for self sealing fuel tanks and airframe strengthening.