Japanese logistics, purchase programs and war booty, reality and alternatives 1936-44

[EwenS]

This interactive map shows the majority of Japanese merchant vessel losses where well within the range of shore based aircraft.

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brandanpbuck.com

The number of ships lost just off the coasts of Japan and the Philippines is ludicrous.

More interesting is how the pattern of losses changes over time.

Another aspect is just why did the US subs become more efficient at sinking Japanese merchant traffic over time? It was not just better torpedoes after 1942 or more subs. It was better intelligence, putting subs in the right place at the right time to sink the traffic. That was something that really developed in the latter part of 1943.

Controversial Victory: The “Tanker War” Against Japan, 1942–1944

In the immediate aftermath of the Second World War, the Army Air Corps (soon to be Air Force) provoked controversy by criticizing the Navy’s “tanker war” against Japanese oil, stating that Japan’s collapse might have occurred months if not years sooner had a coordinated submarine campaign...

www.degruyter.com

 

[TM06]

If I may touch a bit on naval aircraft, while an early A6M8 (Kinsei-engined Zero) sounds appealing, I think it misses the mark of what Japan would need.
The actual A6M8 with the 1,500 hp Kinsei 62 reached 367 mph / 590 kph at around 6,000 m, which falls very short of the 391 mph / 629 kph of the Hellcat and especially the 430 mph / 690 kph of the F4U-1A.
By the time the Kinsei 60-series reaches large scale production - mid 1942 - the Zero is already obsolete. The biggest issue plaguing the Zero wasn't its performance, it was the fact it was never properly replaced. Rather than any major upgrades to keep the Zero going, I believe that it would be more effective to design a replacement as soon as it it entered service.
The IJA high command also needs to be more willing to accept replacements - historically their misguided complacency is what caused the Zero to be used long after it was obsolete.
The replacement for the Zero also needs to be under more lax restrictions. The Reppu's development was hindered due to the extremely strict (and borderline idiotic) requirements put forward by the high command.

What I propose is that the N1K gets designed earlier with the Kasei, being put into service by mid-to-late 1942 with all production dedicated to the Zero converted to the Shiden. If Mitsubishi focuses on the Ha-214 and ditches the Ha-43, it might be possible to replace the Kasei with the Ha-214 due to their similar dimensions, which would likely create a very capable fighter.

 

[tomo pauk]

If I may touch a bit on naval aircraft, while an early A6M8 (Kinsei-engined Zero) sounds appealing, I think it misses the mark of what Japan would need.
The actual A6M8 with the 1,500 hp Kinsei 62 reached 367 mph / 590 kph at around 6,000 m, which falls very short of the 391 mph / 629 kph of the Hellcat and especially the 430 mph / 690 kph of the F4U-1A.
By the time the Kinsei 60-series reaches large scale production - mid 1942 - the Zero is already obsolete. The biggest issue plaguing the Zero wasn't its performance, it was the fact it was never properly replaced. Rather than any major upgrades to keep the Zero going, I believe that it would be more effective to design a replacement as soon as it it entered service.
The IJA high command also needs to be more willing to accept replacements - historically their misguided complacency is what caused the Zero to be used long after it was obsolete.

In mid-42, Zero was probably the best carrier-borne fighter in the world. It will take until F4U and F6F are embarked to dethrone it, and that is more than a year after the Midway disaster. The F4U-1 was probably good for about 400 mph without the water injection, and for another 10 mph with it (1944-45)?
The A6M8 cancelled the drop in the performance that Zero 52c (A6M5c) experienced due to the installation of the protection suite, as well as due to the replacement of the two LMGs with three HMGs. Speed went from 565 (A6M5) to 541 km/h (M5c), and the RoC also suffered due to the ~15% increse in weight. Kinsie 60 will add 30% of power over what the Sakae 21 was good for above 5.7km, that is a hefty amount; Kinsei 50 series will add 15% over the Sakae 21. The Kinsei-powered Zero might've had a shot on the B-17 (especially with the 60 series engine in the nose).

A bit convoluted way of saying that the Kinsei-powered early Zero will be even a greater menace to the Allied aircraft due to it's higher speed and rate of climb.
Yes, replacement for the Zero is still very much needed.

 

[GrauGeist]

Regarding the Lockheed Model 14:

The (IJA) Kawasaki KI-56 was an improved version of the Model 14, the (IJN) Tachikawa Type LO was a licensed version of the Model 14.

 

[TM06]

In mid-42, Zero was probably the best carrier-borne fighter in the world. It will take until F4U and F6F are embarked to dethrone it, and that is more than a year after the Midway disaster. The F4U-1 was probably good for about 400 mph without the water injection, and for another 10 mph with it (1944-45)?
The A6M8 cancelled the drop in the performance that Zero 52c (A6M5c) experienced due to the installation of the protection suite, as well as due to the replacement of the two LMGs with three HMGs. Speed went from 565 (A6M5) to 541 km/h (M5c), and the RoC also suffered due to the ~15% increse in weight. Kinsie 60 will add 30% of power over what the Sakae 21 was good for above 5.7km, that is a hefty amount; Kinsei 50 series will add 15% over the Sakae 21. The Kinsei-powered Zero might've had a shot on the B-17 (especially with the 60 series engine in the nose).

A bit convoluted way of saying that the Kinsei-powered early Zero will be even a greater menace to the Allied aircraft due to it's higher speed and rate of climb.
Yes, replacement for the Zero is still very much needed.

You could make an argument that the Seafire Mk. III was the best at the time but that's semantics.
My point is that the Zero's design was outdated by 1942, and would need to be replaced (or at least under the process of replacement) before 1943 rolls around to have the best chance against the Americans.
It's also worth noting that the base Zero had serious issues with control compression at 250~300 mph, the A6M8 would've had even worse compression at its higher speeds. Compare that to a slightly lower-powered N1K with a Kinsei 60 or Kasei 21~23, which would have better speeds, similar manoeuvrability and much better high-speed flight characteristics - with better survivability to boot.
Before the replacement comes online, the Zero should get the Kinsei yes. But after that, it needs to be sidelined as soon as possible.

 

[Shortround6]

You could make an argument that the Seafire Mk. III was the best at the time but that's semantics.
My point is that the Zero's design was outdated by 1942, and would need to be replaced (or at least under the process of replacement) before 1943 rolls around to have the best chance against the Americans.
It's also worth noting that the base Zero had serious issues with control compression at 250~300 mph, the A6M8 would've had even worse compression at its higher speeds. Compare that to a slightly lower-powered N1K with a Kinsei 60 or Kasei 21~23, which would have better speeds, similar manoeuvrability and much better high-speed flight characteristics - with better survivability to boot.
Before the replacement comes online, the Zero should get the Kinsei yes. But after that, it needs to be sidelined as soon as possible.

A big problem replacing the Zero is that the Zero replacement is supposed to operate off a carrier.
Which means a similar wing loading to the Zero for similar landing and take-off speeds. It may not need to be identical but trying to operated 25-30% heavier could be a real problem for the IJN.

 

[tomo pauk]

Which means a similar wing loading to the Zero for similar landing and take-off speeds. It may not need to be identical but trying to operated 25-30% heavier could be a real problem for the IJN.

Much more of a problem than operating a dive bomber or a C6N from a carrier? Or operating an F6F on an Allied carrier?

 

[EwenS]

No one thus far seems to have mentioned the intended Zero replacement on the carrier decks, the A7M Reppu, Allied reportiing name Sam. Intended to operate from Taiho and later carriers IIRC. Development began briefly in late 1940/early 1941 before being shelved due to higher priorities before restating in Jul 1942. First flight May 1944. It encountered numerous problems along the way.

Mitsubishi A7M - Wikipedia

en.m.wikipedia.org

Mitsubishi A7M Reppu ("Sam")

I assume the A7M Reppu is well-known among the readers of this forum. I've got a question about it and found no dedicated A7M thread, so here's one! For starters: It was a prototype for a new Japanese carrier-borne fighter; didn't make it into production till the end of WW2. It was designed as...

www.secretprojects.co.uk

 

[tomo pauk]

No one thus far seems to have mentioned the intended Zero replacement on the carrier decks, the A7M Reppu, Allied reportiing name Sam. Intended to operate from Taiho and later carriers IIRC. Development began briefly in late 1940/early 1941 before being shelved due to higher priorities before restating in Jul 1942. First flight May 1944. It encountered numerous problems along the way.

Mitsubishi A7M - Wikipedia

en.m.wikipedia.org

Mitsubishi A7M Reppu ("Sam")

I assume the A7M Reppu is well-known among the readers of this forum. I've got a question about it and found no dedicated A7M thread, so here's one! For starters: It was a prototype for a new Japanese carrier-borne fighter; didn't make it into production till the end of WW2. It was designed as...

www.secretprojects.co.uk

I'm not sure that Reppu had anything going on for it.

 

[Shortround6]

Much more of a problem than operating a dive bomber or a C6N from a carrier? Or operating an F6F on an Allied carrier?

Dive bombers generally had bigger wings than fighters. You can substitute trickery/sophistication for wing area, like the C6N.
Everything is a trade-off. You want high performance from a carrier fighter (short take-off and landing) you can use a small wing, but you need fancier flaps and/or leading edge devices which means extra cost to build and extra maintenance.
Carriers were different in different navies (including catapults and arresting gear) at different times.
F6F used both a large wing and large flaps. It also used a wing 32% larger than the wing on a Kawanishi N1K.
We can also recall the A6M7 Zero. A dive bomber version of the Zero to operated off of smaller carriers (?).

You can also strap rockets onto the fighters for take-off
Not sure you really want to do that for routine CAP patrols though.

What people (admirals) wanted in 1941-42 (planning) was not what they would put up with in 1944-45 (reality of combat situation).

 

[tomo pauk]

Dive bombers generally had bigger wings than fighters. You can substitute trickery/sophistication for wing area, like the C6N.

For the Japanese, having Fowler flaps on aircraft was not a trickery come 1941, but a norm, with Zero being an exception.
(yes, C6N's wing was very sophisticated)

 

[Shortround6]

For the Japanese, having Fowler flaps on aircraft was not a trickery come 1941, but a norm, with Zero being an exception.
(yes, C6N's wing was very sophisticated)

Not all Fowler flaps were created equal
From Old thread

J2M: 50 degree (from J2M2)
Ki-43: 20 degree
Ki-44: 35 degree
N1K1: 30 degree

J2M2-J2M5 had maximum flap deflection of 50 degrees, but for combat it was 16 degrees.
Source : Model Art Issue 470 - Page 104 or Famous Airplanes of the World 061 - Mitsubishi Navy Interceptor (J2M) Raiden (Jack) - Page 14

Ki-43 had maximum flap deflection to 30 degrees with speed limit of 250 km/h , and combat deflection 15 degrees with speed limit of 400 km/h.
According to the source :
"6. The butterfly flaps were adopted to increase the performance in banking (turns). The performance is increased considerably by lowering the flaps 15 degrees. However, continuous use will create drag. The flaps operations in combat (Up-Down) are controlled by the flap selector control lever, or, electrically, by the control stick push buttons."
Source: References on piloting Type I Fighter, Model 2 issued on January 16th, 1943 by Army Air Inspection Dept, Akeno Army Flying School.

Ki-44 had maximum deflection of 35 degrees with speed limit of 250 km/h, 15 degrees for combat with speed limit of 400 km/h and 9 degrees up to 450 km/h.
Source is Ki-44 manual, but I dont have exact title translation.


N1K1 had a two stage flaps, to be precise it had a "master" flaps of fowler type which could be deflected up to 19 degrees and at the end of those there were "slave" flaps of standard split type which increased the overall deflection to 41 degrees. If I will find a picture, I can upload it if need be.
The performance of those was a decrease of turn radius by 20 % or even more, however the turn time did not improve as good as turn radius and usual turn time decreased by about 1 to 1.5 second.
The maximum lift-coefficient are approximetely as follows:

Aerial-combat flap at 0 degrees 1.7
Aerial-combat flap at 19 degrees 2.5

Source: Aviation report 0311 - Study of aerial-combat flap (Part 1), Model 15 prototype float seaplane fighter - issued in 1943.

Lockheed tended to use a lot of Flap deflection. Japanese were building them under license.

Grumman used large flaps.

Note the Grumman is not a Fowler flap. It is a slotted flap.

Upper wing surface moves with the flap.

Each Navy and each manufacturer did what they thought was best at the time.
Different flap deflections are going to imposed different loads on the airframe (reason why the different speed limits).
Greater deflections need more actuator travel.
Large flaps place limits on how far aft the rear spar can be.
If the customer is willing to pay for a complicated airframe you can do more.

 

[tomo pauk]

Not all Fowler flaps were created equal

They were far more equal among themselves in what they offer, than when we compare them with 'normal' flaps of the day.

Each Navy and each manufacturer did what they thought was best at the time.
Different flap deflections are going to imposed different loads on the airframe (reason why the different speed limits).
Greater deflections need more actuator travel.
Large flaps place limits on how far aft the rear spar can be.
If the customer is willing to pay for a complicated airframe you can do more.

All good.
If anyone knew how to make good/great flaps, Japanese knew it.

 

[TM06]

No one thus far seems to have mentioned the intended Zero replacement on the carrier decks, the A7M Reppu, Allied reportiing name Sam. Intended to operate from Taiho and later carriers IIRC. Development began briefly in late 1940/early 1941 before being shelved due to higher priorities before restating in Jul 1942. First flight May 1944. It encountered numerous problems along the way.

Mitsubishi A7M - Wikipedia

en.m.wikipedia.org

Mitsubishi A7M Reppu ("Sam")

I assume the A7M Reppu is well-known among the readers of this forum. I've got a question about it and found no dedicated A7M thread, so here's one! For starters: It was a prototype for a new Japanese carrier-borne fighter; didn't make it into production till the end of WW2. It was designed as...

www.secretprojects.co.uk

The Reppu was undoubtedly an excellent design, but it doesn't fit into the earlier timeline that would be required here. I can't imagine it would be able to perform as well with a Kinsei 60 or Kasei 21~23 as even with the 2,000 hp Homare the A7M1 prototype was considered underpowered.
It needed an engine like the Ha 43 in the 2,200 hp range in order to be properly competitive, and the other earlier possible options in that power class (Ha 214, Ha 219) would require a significant redesign to fit due to their size and bulk - a significant time loss compared to the N1K which could be easily adapted to the Kinsei and Kasei and thus making it into production much sooner.

 

[Shortround6]

The Reppu was undoubtedly an excellent design, but it doesn't fit into the earlier timeline that would be required here. I can't imagine it would be able to perform as well with a Kinsei 60 or Kasei 21~23 as even with the 2,000 hp Homare the A7M1 prototype was considered underpowered.
It needed an engine like the Ha 43 in the 2,200 hp range in order to be properly competitive, and the other earlier possible options in that power class (Ha 214, Ha 219) would require a significant redesign to fit due to their size and bulk - a significant time loss compared to the N1K which could be easily adapted to the Kinsei and Kasei and thus making it into production much sooner.

Yes and no.
There was a project that was started in early 1940 (?) the 16-Shi specification. But it didn't get far due to a shortage of design staff and project stalled. It was revived in April 1942 as the 17-Shi specification. Which is too late.
Very little seems to be known about the 16-Shi specification?
The 17-Shi seems to be fairly close to the F6F in size, weight, armament and performance. Unfortunately that means an engine of comparable power/size was needed as you have said.

The speculative (hypothetical) 16-Shi might have been able to be powered by an in-between engine between the Sakae and MK9. But you need an engine that is going to show up even before the Homare. You also need a smaller, lighter aircraft with less armament.
Wither you can actually get a combat effective carrier fighter using a late 1942/early 1943 Kinsei, Kasei or Army type 2/Ha-109 engine seems to be the question.
Better armament that the A6M2, more performance. Now what can we give up? Range/endurance? Not install protection to keep it light?
Can you use a 'regular' wing? The Raiden was supposed to have used a laminar flow wing. Good idea but even NA had trouble with build quality to actually get laminar flow.
Some of the other tricks used on the Raiden didn't work well in practice. Carrier landings using the Raiden cockpit/canopy?? Getting rid of the long prop-shaft and fan would have speeded development but at what cost in speed?

 

[tomo pauk]

The speculative (hypothetical) 16-Shi might have been able to be powered by an in-between engine between the Sakae and MK9. But you need an engine that is going to show up even before the Homare. You also need a smaller, lighter aircraft with less armament.
Wither you can actually get a combat effective carrier fighter using a late 1942/early 1943 Kinsei, Kasei or Army type 2/Ha-109 engine seems to be the question.

Either of these engines will me making 1250 HP at 5.5 km or more. A far cry vs. the Sakae making 950 HP there, and Zero was reasonably combat effective with that engine in the nose in that time.

Better armament that the A6M2, more performance. Now what can we give up? Range/endurance? Not install protection to keep it light?

We'd been giving up mostly the low price, since the next-gen fighter will not be as cheap as the Zero.
Range/endurance is a thing of how much of the fuel is carried vs. the engine power (consumption), a thing that bigger tanks were solving from the Wright Flyer days. Point of the more powerful engine in the nose is that one needs to sacrifices less, not more, so protection should be mandatory.

 

[Shortround6]

Either of these engines will me making 1250 HP at 5.5 km or more. A far cry vs. the Sakae making 950 HP there, and Zero was reasonably combat effective with that engine in the nose in that time.



We'd been giving up mostly the low price, since the next-gen fighter will not be as cheap as the Zero.
Range/endurance is a thing of how much of the fuel is carried vs. the engine power (consumption), a thing that bigger tanks were solving from the Wright Flyer days. Point of the more powerful engine in the nose is that one needs to sacrifices less, not more, so protection should be mandatory.

Well, the Homare was supposed to make a lot more power, so lets look at the power at altitude and the weight of the engines.

Sakae 12...................950hp.....................4200 meters.......................530kg
Sakae 21...................980hp.....................6000 meters.......................590kg
Kinsei 54.................1100hp....................6200 metes.........................-------
Kinsei 62.................1250hp....................5800 meters.......................--------
Ha-109.....................1220hp...................5200 meters.......................720kg
Kasei13....................1300hp....................6000 meters.......................------
Kasei 15...................1280hp....................6000 meters.......................------
Kasei 21...................1410hp.....................4200 meters......................------

Homare 11..............1460hp...................5700 meters......................830kg
Homare 21..............1620hp...................6200 meters......................830kg
R-1830 -86..............1040hp...................5600 meters......................710kg

My copy of "Japanese Aero-Engine" is missing 4 pages, corrections/additions welcome.
What Japanese engines were coming available when in 1942/early 1943 is very important. The Kasie engine used in the J2M2 took quite a while to sort out. Perhaps the Bomber version of the engine could have been used or one of the bomber engines that were used in the G4M series of the time, which is why I threw in the Kasie 15.

The Improvement from the A6M2 to the A6M3 was significant. However it is sort of overshadowed because the A6M3 didn't have the range needed to fly the Rabaul to Guadalcanal missions (at least not at first) and with the destruction of the Japanese carriers there were only two carrier battles after Midway in 1942 in which the forces involved were much smaller than at Midway. After the Battle of Santa Cruz there was an 18 month gap in carrier battles.
There was a lot of Island to Island combat and there was US carrier vs Japanese Island combat going on.
The Zero spiraled down as the Sakae 31 engine never gave the increased power promised and any/all improvements hurt the performance of the A6M5 aircraft.
The Kinsei 54 might have held up the Performance of the A6M with the improvements but not increased it by much.
There is a fine line where a 1220-1300hp engine is going to give the needed performance in late 1942 and 1943 (F6Fs don't begin to show up until Aug 1943?) to allow the Japanese to retain superiority over the US Army fighters in the Island to Island fighting.

 

[tomo pauk]

What Japanese engines were coming available when in 1942/early 1943 is very important. The Kasie engine used in the J2M2 took quite a while to sort out. Perhaps the Bomber version of the engine could have been used or one of the bomber engines that were used in the G4M series of the time, which is why I threw in the Kasie 15.

If Japanese/Mitsubishi want even more from their engines, the resources and time spent on fancy extension shafts or counter-rotating props should've been better spent on making 2-stage superchargers. Until/unless that is made, just plop the 'normal' engines on the fighters.

The Zero spiraled down as the Sakae 31 engine never gave the increased power promised and any/all improvements hurt the performance of the A6M5 aircraft.

For all of it's qualities, the Sakae 31 was still a small engine. The earlier a bigger engine is on the Zero, the Zero is better able to retain importance. By 1942, the price advantage of the Sakae vs. Ha 109 has all but vanished (with Kinsei falling between the two?).
If the Kinsei 50 series in in the nose by mid-1942, the further installation (mid-1943?) of the 60 series should've been trivial.

 

[TM06]

If Japanese/Mitsubishi want even more from their engines, the resources and time spent on fancy extension shafts or counter-rotating props should've been better spent on making 2-stage superchargers. Until/unless that is made, just plop the 'normal' engines on the fighters.

For all of it's qualities, the Sakae 31 was still a small engine. The earlier a bigger engine is on the Zero, the Zero is better able to retain importance. By 1942, the price advantage of the Sakae vs. Ha 109 has all but vanished (with Kinsei falling between the two?).
If the Kinsei 50 series in in the nose by mid-1942, the further installation (mid-1943?) of the 60 series should've been trivial.

I'm in favour of the Ha 109 in IJA aircraft - it would be a better performer than the Kinsei 50 series and even the Kinsei 60 series, possibly becoming one of the best engines in its class worldwide should it get a proper two-stage supercharger.
But I do wonder if that would also allow for the Ha 219 to enter production sooner should Nakajima focus on the Ha 5 series (of which the Ha 219 is a part of) instead of the Homare and Sakae? The 219 had some issues with cooling, but that's nothing compared to the complete maintenance headache that was the Homare. Maybe a properly developed 219 shows up late 1943~early 1944?

 

[tomo pauk]

I'm in favour of the Ha 109 in IJA aircraft - it would be a better performer than the Kinsei 50 series and even the Kinsei 60 series, possibly becoming one of the best engines in its class worldwide should it get a proper two-stage supercharger.

There was a lot of the potential in the Ha 109 engine, that Japanese squandered in 1943-45. Like the addition of the water-alcohol injection, better exhaust, increased production and usage, production and usage in the Navy aircraft, and indeed the 2-stage supercharged version. Engine itself was of modest size & weight, and it seems that it was reliable. The Ki-84 with the water-injected Ha 109 + better exhausts would've been very interesting IMO.

But I do wonder if that would also allow for the Ha 219 to enter production sooner should Nakajima focus on the Ha 5 series (of which the Ha 219 is a part of) instead of the Homare and Sakae? The 219 had some issues with cooling, but that's nothing compared to the complete maintenance headache that was the Homare. Maybe a properly developed 219 shows up late 1943~early 1944?

Nakajima invested a lot in the Mamori/Mamoru engine type, that certainly taxed the engine division improving and debugging other engines.
The Ha 219 seems to me as a more conventional engine than the Homare - perhaps that might've been a boon wrt. to the Japanese situation back in ww2? It was also heavier than the Homare by 300+ kg, and wider/taller (1280 mm vs. 1180) - it will require a more substantial aircraft than the Homare. Ha 219 was supposed to make about 20-25% better power than the Homare - that is a hefty difference in power indeed.

As for the Homare's problems - two questions are still to be answered, 80 years later:
- how much the headache was the Homare really?
- how much of the problems Homare had were actually due to the engine itself, and how much these problems were due to the general Japanese situation in the last 12 months of the war wrt. the lack of nickel and the like, fuel octane rating, factories and repair centres being bombed etc?

Reverting back to the Ha 219, the Mitsubishi's counterpart (Ha 42) seems to be a reliable engine under the same conditions, while the all-new tech Ha 43 never flew a combat sortie. So indeed the Ha 219 might've been a better choice, despite it's bulk & weight.

Now that I've scratched the Ha 42 - that seems like an engine worthy of an 1-engine fighter wrapped around it. Kill the Ki 67 for all I care.