Anyone interested in some intellectual exercise?

No sir, not exactly. The KI-43 will be gradually phased out until it reaches a minimal production level suitable for sustaining our allies. All KI-43's in service with IJA operational squadrons, will be gradually replaced with A6M series aircraft, starting with the A6M2 (UA) model. All existing KI-43's surplus to our operational squadron requirements, those squadrons will be upgrading to the A6M2 series, will be pooled and used to meet the requirements of our training squadrons and arming our allied forces. We will have a significant upsurge in our aircraft requirements as these new pilots begin graduating from the basic portion of our flight schools, we're talking some months down the road. The KI-43 will become a limited standard type with minimal production. The A6M series will fill the fighter role with both land and carrier based IJN squadrons and with IJA fighter squadrons. If and when the KI-61 series becomes operational, it will replace the A6M series with both IJA and IJN land based squadrons. For logistical reasons I would upgrade Home Island and Chinese based squadrons to the KI-61 first. The A6M series will remain the frontline carrier based fighter because we have no follow on carrier capable type. The KI-61 lacks this capability. General Kourei was correct in what he was getting at earlier. An airframe designed for a 1500hp engine (KI-61) will see a greater performance increase than an airframe designed for a 1000hp engine (A6M/KI-43). While fitting the 1500hp engine to the A6M airframe will produce a higher performance aircraft the improvement will not be as great as in an aircraft designed for a 1500hp engine.

When and if, (remember we may encounter developmental issues) the KI-61 reaches full production status and begins replacing A6M in operational land based squadrons, the excess A6M aircraft will begin being returned for overhaul and use in training squadrons. KI-43 series production can be halted, except for spare parts (because we will have so many in service). Excess KI-43's released from training duties will be used to equip allied squadrons and as replacement aircraft for the same. At this point in time we will gradually begin to swap A6M factories over to KI-61 production, only retaining enough production capacity to meet our carrier based squadron needs.

Research and development for the A6M's replacement as a carrier based fighter will continue as ordered in December of 1940 (this aircraft became the A7M SAM). Unfortunately, we suspended this research in January of this year (1941) due to placing additional development requirements on the Mitsubishi development team for the 14-Shi interceptor (eventually became the J2M Raiden). I favor suspending this research (14 Shi) and re-starting our development of an A6M successor (A7M). We've already lost seven months, I do not wish to lose more. We cannot maintain the A6M's superiority or parity against western aircraft indefinately. Despite continuing research into upgrading it, the A6M series will eventually reach the point of obselescence.
(I will get further into the 14-Shi requirement and Interceptors later when we discuss this issue)

Kawanishi has recently approached us with a proposal for producing a land based fighter version of the N1K1 float fighter it currently has in development. We have not supported this and Kawanishi is pursuing it as a private venture. I favor awarding Kawanishi a development agreement for a land based version of this float fighter. I see limited need for additional float plane fighters past what we can accomplish with upgrading the float plane version of the A6M, the A6M2-N Rufe, which is scheduled for its first flight in early December this year, tenatively December 7th. My thoughts on float plane fighters is, that due to the restrictions imposed by having an attached float, they will not be able to compete with newer allied fighter types. Therefore, their role needs to be restricted to protecting against enemy tactical bombers and reconaissance aircraft. This requirement, for the forseeable future should be within the capabilities of the A6M2-N. I do favor incorporating improvements made to the A6M series into the -N version to maintain maximum capability. My proposal for Kawanishi would be, to use the developmental progress it has made thus far and going forward concentrate on the non-float version. I would issue the further requirement that if practical, produce a carrier based version. (four prototypes of this type were built and tested on Shinano before she was sunk, 2 N1K4-A Shidens and 2 N1K4-A Shidens. After the sinking, with no more operational carriers available, and with a pressing need for capable interceptors to oppose B-29 raids, the IJN dropped the project. The N1K1-J and N1K2-J "George" proved to be one of the best Japanese fighters of the war, able to meet the Hellcat and Corsair on equal terms and was probably the best "dogfighter" produced.) If we adopt this proposal I would estimate we will be fielding the first N1K George's in mid-1943, and it can serve as an interim carrier fighter until we have the A7M available. At that time, once carrier based requirements are met, it will also provide a potential follow on model to begin replacing the KI-61 series in the land based role.

 

Well, in a historical context, we are either producing the Ki-43-I or we are not, there is no middle ground. The Ki-43 was being produced in limited numbers at only one plant - Nakajima Hikoki K. K. at Ota(716 a/c produced between 4/41-2/43). Mass production of the Ki-43-II did not begin there until 11/42 - when the Ki-43-I was being phased out. Tachikawa Hikoki K. K. at Tachikawa did not begin mass production of the Ki-43-II until 5/43, and Tachikawa Dai-Ichi Rikugun Kokusho at Tachikawa did not begin a limited run of the Ki-43-IIa until 10/42.


In regards to the Ki-27 "Nate" produced by Mansyu/Manshukoku Hikoki Seiso K. K. at Harbin, there remains some debate as to whether Mansyu numbers were for the actual Ki-27 fighter or their Ki-97 advanced trainer - based on the Ki-27. Also, the Nakajima plant at Ota continued to produce the Ki-27 until 12/42 - although I am not sure if this was the fighter of trainer version. Given our planes for rapidly increasing Japan's output of trained pilots, it would seem in our best interests to continue to keep these factories producing the Ki-27 for use as an advanced trainer aircraft.(which is a fact that seems to have been forgotten in the race to ramp up production of combat aircraft).


With regards to the Ki-100. I am not sure how you came to the conclusion that the conversion was done in 14 days(possibly from the time of the destruction of the Kawasaki's Akashi plant until first flight of the Ki-100), but this is most certainly incorrect. Still, the time frame was very short - roughly 90 days. The IJAAF "laid down the law" to have the Ki-61-II converted to use the Mitsubishi Ha-112-II radial engine "or else." Shall we say that with this "proper motivation", the Kawasaki designers responded with hitherto unknown alacrity. They took apart and examined an Fw-190 A-5 that had been imported in late '43 and closely examined it's engine mounting & dynamics, and used this to create an radial engine mounting for the Ki-61-II. The completed prototype first flew on February 1, 1945.

Now, the real poser for us will be our lack of a FW-190 airframe until late-1943. Without that to study, the 90-day conversion goes right out the window. Hopefully 6-9 months would be adequate, maybe a year tops. The other problem is that our early-war high-horsepower engines were unreliable, and it took quite sometime to make those engines reliable. IIRC, it took awhile to overcome the Ha-112-II fuel injector problems, so it will likely be between late '42 through mid-43 till the radial engine Ki-61 is ready - for combat. And it will be sometime after that before it is seen in meaningful numbers in combat.


With regards to the A7M Reppu/Sam. While time was lost in it's development, the question remains as to what was actually lost...

The A7M Reppu was first designed to meet the IJNAF's 16-Shi specification for the new fighter, however, what the 16-Shi specifications actually were, AFAIK, has been lost to time. When the IJNAF & Mitsubishi returned to the A7M design in April '42, it was to meet the new 17-Shi specifications, the details of which were agreed upon in July, '42. What we do know is that the A7M1 first flew on May 6, 1944 with a Nakajima NK9K Homare-22(the engine specified by the IJN in September '42), rather than the Mitsubishi MK9A or MK9B engine that the designers intended to power the aircraft. The Nakajima Homare gave poor performance at or above mid-altitudes, so the A7M was modified to carry the intended Mitsubishi engine.

So, it is very likely that if we continue with the intended 16-Shi A7M, we will still be playing "catch-up" in 1943-44.


With regards to the N1K1 Kyofu & Shiden. An early appearance of the Kyofu-based Shiden is probably unlikely, and it will appear as it did historically - unless we boost our engine research. The N1K1 Kyofu first flew on May 6, 1942, while the Shiden first flew on December 27, 1942. Kawanishi developed the Shiden, on it's own accord shortly after it began work on the Kyofu, thus it did not take long to get the land-based Shiden in the air. However, the engine proved to be the most hindrance to the program, as the early Nakajima Homares failed to develop their advertised horsepower. Still, if we can boost engine production & development, this would be a very good candidate to replace the A6M.



As to weaponry, I would concur with dropping the rifle-caliber MGs as quickly as possible, and switching to an all cannon outfit for new fighter aircraft.

The early Japanese HMGs tend to jam easily(hence the retainment of the rifle caliber MGs past their prime), and they also don't synchronize well to the propeller, so if we use them at all in fighters, they should be in the wings - not mounted in the fuselage & firing through the engine cowling. We should also discontinue the use of the high-explosive HMG rounds, as these tend to explode in the barrel - causing fatal damage to the engine if used in the cowling guns.

The bombers are more of a pickle, as they tend to be very narrow, and are not likely to lend well to converting the 7.7s to larger guns - except in the tail position. Newer roomier turrets would likely need to be designed for the HMGs as well. Still, newly designed bombers should be able to overcome this hindrance as opposed to refitting the bombers we do have.

 

Yes sir, the Harbin production can be debated as to the type, but they did produce a version of the KI-27 Nate. As for trainers there were several models of the Nate built for training KI-27A-KAI 150 units, KI-27B-KAI 225 units, 1329 units total, of the single seat KI-79A and KI-79C and the double seat KI-79B and KI-79D. I believe this is the model you were referring to when you wrote, "their Ki-97 advanced trainer", but it's easy to get confused when talking Japanese aircraft designations because the KI-27 was also known as the Army Type 97 Fighter. So technically, it could be referred to as the trainer version of the Type 97, but in this case the KI- designator would not be used.

I have no problem leaving the KI-27 production up as long as we feel necessary, the decision belongs with you gentlemen. We will have some time between recruiting, testing, selection, ground school, initial flight training, solo training, etc. before we get to advanced fighter training. I was anticipating having additional KI-27 types available from operational squadrons that have had their aircraft upgraded. I had not forgotten the need for trainer types, we have numbers of trainers in service and additional aircraft I favor farming out to local industries, many of these types need only minor modifications to be made largely of non strategic materials such as wood. Some types we have in service Nakajima A4N1 Type 95, Yokosuka K2Y1 and K2Y2, Mitsubishi K3M3 Type 90-2, Yokosuka K4Y seaplane trainer, Kyushu K9W1 Type 2/Kokusai KI-86, and about nine or ten more, you get the idea. We will also have numbers of A5M's being returned for training duties. Older engine types such as the Nakajima Hikari, Hitachi Kamikaze, and Hitachi Hatsukaze required for these aircraft would have their production facilities moved from the Home Islands to our new industrial zones in China, along with the necessary production machinery and tooling. The existing plants would convert to newer engine types needed for our combat aircraft.

You have made very good points and each needs to be addressed fully. I have some running around I need to do right now and will try to finish addressing your concerns later this evening. Thank you for the excellent reply!!!!

 

As for your time frame question. There seems to be a great deal of contradictory or unclear information concerning the conversion of the KI-61 to KI-100. The pressing need for interceptors did have the Ministry of Munitions issue a directive to Kawanishi concerning design studies for mounting a radial engine to the KI-61 airframe. The directive is variously stated as being issued in October or November 1944. Kawanishi decided upon the HA-112, but showed little interest in the change, the chief engineer even stating that it was not practical. The destruction of the HA-140 engine factory was and 275 engineless airframes was what got Kawanishi's team to actually pursue the modification. I agree with your statement; "this "proper motivation", the Kawasaki designers responded with hitherto unknown alacrity". I think this an accurate characterization. It was my impression from reading various accounts of the development that it was the Ministry of Munitions and not the IJAAF that pushed Kawanishi into looking at the possibility, and that Kawanishi decided upon the HA-112 due to a number of factors, reliability and HP among them. Though not stated specifically one way or the other, it is my impression from the majority of sources, that the work prior to January 19th, when the engine plant was destroyed was confined to the selection of the appropriate engine. You are correct that an examination of a supplied FW-190 was part of the conversion process. I would suggest that this is not really a problem as far as we are concerned. There are several paths that could lead us to the earlier introduction date, and as stated before, we can encounter developmental problems.
-If (TOS) General Kourei manages to negotiate a suitable technological sharing agreement with Germany, our designers could inspect an FW-190 there, now. Or alternately have an example acquired and shipped to Japan by submarine. It has been in service since August.
-The ability to engineer this conversion does exist domestically. The Nakajima KI-44, already testing, was the product of mating a large diameter engine to an airframe of comparatively narrow cross section. It used the HA-109 version of the Nakajima HA-5/HA-34 series, an engine with a 1.6" (49.6") greater diameter than the Mitsubishi HA-112's 48" diameter. (If we run into developmental issues with the HA-33 series we could substitute the slightly larger HA-34 engine, it produces 1,440 HP vs 1,500 HP and is 178 lbs. heavier. This is still less than the HA-140 installation that was about 600 lbs. heavier between engine, radiator, coolant, etc.) The Yokosuka D4Y3 was also an airframe designed for the same engine as the KI-63 that had successfully had a radial engine mated to it. Though still in the future it did happen well before Japan ever acquired the FW-190 examined to convert the KI-61 to the KI-100.

 

I'm not sure this is true. It was not uncommon for an aircraft in development to incorporate specifications for sucessive years. (For those that are curious a Shi is a year specification, 16 Shi would be the 1941 specification and 17 Shi the 1942 specification) The Homare engine is in the 2,000HP range as is the MK9/HA-43 (actually 2,200HP) so I don't think there would be an appreciable effect on the design. I do have one question that you may know, I really have never been able to find an acceptable explaination. Normally, seven row radials developed into twin row 14 cylinder radials. Nine row radials normally developed into twin row 18 cylinder radials. With the Nakajima Homare they attempted to modify the 14 cylinder Sakae into the 18 cylinder Homare, same same with the Mitsubishi HA-43/MK9. It was an 18 cylinder development of the 14 cylinder Kinsei/HA-33. Why didn't Japan do as America did and develop their nine row radials such as the Nakajima Kotobuki into twin row 18 cylinder models. I suspect it was because the 18 cylinder models they did produce were more compact being based upon 14 cylinder models, but this is also one of the prime causes of their teething problems. Just thought you might know.

That's basically how I see it. I do think if we ask Kawanishi to abandon the N1K1 and focus development on the Shinden, the availability dates would flip-flop. The Shinden available around May 1942 and if Kawanishi decides to pursue the N1K1 on it's own it would be available in December. I also agree that we need to push engine development, and I will press the Council to allocate additional resources in this area, plus I feel that the Production Board I mentioned earlier should require technological data sharing between our major engine producers, so that incremental improvements can be incorporated into all engine lines.

 

If I may be permitted to make a general observation.

Colonel Bobimoto is offering the Council a best case projection for timetables re-guarding aircraft development, while the esteemed Admiral Takao offers the worst case projection for the same. Certainly both are possible and both should be kept in mind as we deliberate.

Undoubtedly we will have some come along faster than hoped, while others lag behind for reasons we do not see clearly at this time. This will occur in all our endeavor's from this point onward and in every area of this conflict.

All that we can do is to set things into motion, deal with the impeadiments as they present themselves and make the best use of what tools we have at any given moment. We can take some solace from the knowledge that our enemy's face the same obstacles as we do.

Prime Minister.

 

We should start with low end projections and then be ready to use any extra production as it comes. We can have production phase lines. we have a bottom level and every time the next level is reached we implement the plan for that level.

 

There is likely to be a lot of "wiggle room" in estimations, as the development of aircraft & their engines will be decided on how many points we put into R&D and production, plus what resources are available. Historically, the Japanese often had problems with their high-horsepower engines(especially their turbosuperchargers for high altitude performance) and not so much their airframes. Their are several examples of Japanese aircraft that were ready for production, however more time was needed for their engines.


USMCPrice,

I can't say as to the Japanese engine design, but I believe you are on the correct path. Not only were the Japanese designs more compact, the usually weighed a few hundred to several hundred pounds less than their American counterparts.

 

Thank you for your opinion on this matter, I was curious.

We will be issuing the 17th and all subsequent Shi, so we can define what we are looking for in an aircraft. Do you think it would be profitable to issue specifications to Nakajima to produce a twin row version of their Kotobuki and Hikari engines?
Historically, the 9-cylinder Kotobuki (HA-1) was modernized and evolved into the 9-cylinder Hikari with and enlarged bore and stroke. This was developed into a 14-cylinder double row version the HA-5 of 850-950 hp output, depending upon the version. Improved models of the engine were the HA-41, 1260hp and HA-109 1500hp with a 49.6" diameter and dry weight of 1,378 lbs. (HA-5, -41, -109 shared the HA-34 unified code).
Theoretically, an 18-cylinder double version of the Kotobuki would weigh 1544 lbs., but produce 1560 hp. A similar 18-cylinder Hikari should produce 1,640 hp. I could not find a good weight on the Hikari, nor a diameter on either.

 

So far, everyone is correct relative to hard minerals (coal, bauxite, etc.). However, the key mineral -- and the reason Japan declared war against the US in the first place -- is that the US has control of oil resources. Without an abundant supply of oil, your trade options are limited.

Yes, there are oil resources in the South China Sea, but they won't be developed for another two decades.

 

[sharedmedia=core:attachments:16730]

We intend to give the diplomatic option one more chance, but are making preparations for commencement of hostilities against Britain and the Netherlands in late November if there is no movement towards the lifting of the oil embargo. We currently have a deficit between domestic production and need of 8110 tons of oil per day. We currently have a reserve of 3,767,420 tons or enough oil for 464.54 days consumption at our current usage rate. Obviously expansion of our industry and combat operations will increase our rate of use.
We have a requirement of 13,900 tons of fuel per day for our economic needs, our domestic refining capacity is 9315 tons of refined fuel, oil and lubricants per day, so we are 4,585 tons of refined petroleum products short of our base requirements per day (again this does not include fuel for military operations or shipping). We have stored reserves of 4,862,678 tons of refined products, enough at our current consumption rate for 1060.56 days.
Of our initial objectives Palembang, Sumatra's oil output alone would meet the needs of our refineries. If we capture its refineries intact, our refined petroleum product shortfall would be erased, but we'd still have the shortfall in crude oil for our Home island facilities. If we seize all four of our primary targets intact, Palembang; Balikpaupan, Borneo; Djambi, Sumatra and Medan, Sumatra, we will be self-sufficient in crude oil and have a daily fuel surplus of 4700 tons. Our tertiary targets, in order of importance, Soerabaja, Java; Miri, Borneo; Samarinda, Borneo; Tarakan, Borneo; Bengkalis, Sumatra; Tjepoe, Java; Beola, Java; Babo, New Guinea and Brunei, Borneo would give us oil supplies of twice our current consumption level.
One of the problems with the SRA oil supply is that much of the oil has a high volatile content. We have a number of synthetic fuel plants that we have built with German aid. We have not aggressively pursued this technology and it is my desire that we negotiate a deal with the Germans for additional expertise and technological help to realize the potential of these facilities.

 

Back to our discussion of aircraft.
We will continue improvement on the Mitsubishi A6M line and this aircraft will be the standardized type for both IJN and IJA, carrier and land based fighter squadrons. The Nakajima KI-43 will receive a weapons upgrade and be declared limited standard with limited production retained until the Kawasaki KI-61 (radial engine) becomes operational. When operational the KI-61 (radial) will become standardized as the joint land based fighter. We should issue a modified 16 Shi carrier fighter specification for a 2000hp range aircraft with the following specifications; top speed 345 kn (639 km/h; 397 mph) above 6,000 m (20,000 ft), climb to 6,000 m (20,000 ft) in less than 6 minutes, be armed with two 20 mm cannon and two HO-103, 12.7mm machine guns, and retain the maneuverability of the A6M3. When we issue our 17 Shi carrier fighter specification we can build upon this minimum performance criteria to incorporate advances in aeronautics and engine technology, but we will have begun the research and design process. (This is basically the same criteria that resulted in the A7M fighter) Our 16 Shi carrier fighter proposal will also instruct Kawanishi to suspend or reduce priority on development of the N1K float fighter and order a maximum effort, directed at development of a carrier/land based interim fighter based upon development thus far to be designated the N1K2-J Shinden. (This should give us some insurance against developmental issues that may crop up with the A7M and KI-61 (radial) lines of development).
The 16 Shi (modified) will also authorize the development of a follow on land based, fighter type to replace the KI-43/KI-61 series, based upon a 2000hp range engine. (Historically this specification was issued in early 1942 and resulted in the Nakajima KI-84 Hayate, which first flew in March of 1943. We're just doing a little more long term planning and getting a several month jump on the historical timeline because we are deciding now to drop further development of the Nakajima KI-43 in favor of a fighter with better survivability characteristics such as armored glass, heavier airframe with internal bulkheads, self-sealing tanks, protective armor for the pilot etc.)
This should take care of our single engine fighter needs for the forseeable future. We will continue to issue revised specifications yearly to incorporate technological advances or combat lessons learned, but this should serve as a base outline for our developmental efforts into this type.

 

Interceptors- It will likely become necessary for us to have a need for an interceptor type to protect our industrial areas, resource locations, particularly oil and refinery locations and to protect our forward bases against high altitude medium and heavy bombers. I would suggest that the prime requirements for such a type are speed, high rate of climb, heavy firepower and high service ceiling. We currently have the Nakajima KI-44 Shoki (Tojo) under going service testing. Service testing of 42 aircraft, two prototype KI-44's and 40 pre-production units was begun on 15 September with positive results thus far. I favor giving the go ahead to begin full scale production and adopting this as our inter-service (IJA/IJN) Interceptor type.
Development on a Mitsubishi Naval land based Interceptor was authorized under the 14 Shi specifications. In January of this year we suspended development on our 16-Shi carrier fighter (historical A7M) in order to focus our efforts on continued A6M development and development of this 14-Shi Interceptor type. I do not see the need for continuing development of this aircraft (J2M Raiden) since we could just as easily adopt the KI-44, now under going service testing to fill the 14-Shi requirement for a Navy land based interceptor. (Resumption of R & D into the A7M did not resume until April of 1942, when the J2M entered flight testing. By stopping development of the J2M now we not only reduce redundancy, we regain 7 months of lost A7M developmental time. When the J2M Raiden was historically fielded in December of 1942, it offered no better performance and was actually inferior in most areas to the version of the KI-44 current at that time).
As a follow on type, I would favor issuing Kawasaki a developmental requirement for optimizing its KI-61 (radial) for the interceptor role by fitting the largest most powerful engine available, increasing its firepower and looking into various supercharging technologies to increase high altitude performance, at the expense of range and maneuverability. We can designate this type the KI-100.

 

I can live with this as a fighter production program. Barring heavy losses, if the A7M is viable as a Carrier fighter and the Ki-61 is equally successful as a Land fighter, we would seem to have a considerable number of A6M's to dispose of. Any thoughts as to how we might use them?

 

We have a lot of smaller bases that the longer range planes could be useful for.

 

I would hope that when and if we introduce the A7M, it's range is not too dis-similar to the A6M it replaces, which will likely be the IJN's Land based fighter until the Ki-61 proves itself.

 

A couple of query's Colonel Bobimoto.

Will the A5M and Ki-27 retain a spare parts production line since we will use them extensively in the training role?

Is not a portion of the Ki-27 inventory set aside for delivery to our Allied partners Air Force's as primary Fighter, at least until we begin to phase out the Ki-43?

 

In this case Mr. Prime Minister we will have plenty of uses for them. We will be pumping out so many new pilots we will always have the need for advanced fighter training aircraft. Remember, it will be some months down the road before we will have the first of our new pilot classes advance in their training to that point, so when they reach that stage we will need all the extra aircraft we can get our hands on. Additionally, production will never be able to keep all our operational squadrons with the most up to date aircraft, we will continually be re-equipping the best, and most engaged squadrons. They will pass their aircraft down to squadrons in less exposed areas, who will in turn pass theirs down to squadrons in lesser exposed areas, who will be passing theirs down to training squadrons.
To illustrate the current version the A6M2 is in short supply already. We will immediately introduce an upgunned version, for this discussion let's call it the A6M2-(UA) and field installation kits to bring the A6M2's up to this standard. This version will have the two cowl mounted 7.7's replaced by the 12.7mm HO-103 and it's two Type 99 20mm's with the HO-5. Now we will be limited by our production how fast this change can be made. I'd allocate the weapons to new production first and field upgrades second. Our current KI-43's will not be upgraded immediately because we can't produce that many kits. Upgrade kits and new production A6M2-(UA)'s will go first to Kido Butai, secondly to IJA/IJN land based units preparing for the Malaysian operation. The reason for this is we need to protect our carriers, their bomber and torpedo squadrons and the Kido Butai will be engaging the best the enemy has. Initially, I feel the British will be our most lethal adversary. KI-43's replaced by A6M2 (UA)'s will be passed down to squadrons fielding the older KI-27. Remember also, that each new line we introduce will be continually upgraded. We will probably soon be fielding the next version of the A6M. I'd like this version to include a strengthened wing frame structure and main spar (we have reports that aggressive pilots can over stress the wings during violent maneuvering) we will also strengthen the wing skinning. We use semi-monocoque construction in these aircraft where the skin is actually a structural strength component. At this time we can incorporate internal wing bays to add 4 additional 12.7mm guns, two in each wing.
Takao raised a point that I haven't forgotten about nor replied to as of yet;

Part of this was that the HO-103 when used in a synchronized cowl mounting loses over half it's rate of fire, decreasing from 850 rpm to around 400. Takao is correct, the Japanese in an effort to increase the lethality introduced explosive ammunition which as he said led to barrel explosions. The KI-43 even had plates and blast covers mounted to reduce the chance of engine damage in the event of a premature detonation. I agree we should not introduce the explosive round at this time. An additional factor is that the smallest caliber that an explosive round is really reliable and carries enough explosive to make it really effective is in the 20mm range. I would favor the use of 12.7mm incendiary rounds, and AP which are reliable and effective. As to the reliability issue Takao mentions, it appears that the reliability issue relates directly to the aforementioned explosive rounds. I have also read that one of the reasons for retention of the 7.7mm was a problem with adequate supply of 12.7mm ammunition. Mounting the 12.7mms in place of the 7.7mm is very simple and the guns were actually interchangeable in the KI-43. The synchronization issue I suspect was partially due to the attempt to synchronize two guns with different muzzle velocities, the mix of 1 x 7.7mm and 1 x 12.7mm was common in the KI-43. The higher MV of the 7.7 would allow for more RPM in a synchronized mounting. The fact that the KI-43 series never, to my knowledge, carried wing mounted guns, even as Japan continually attempted to upgrade aircraft firepower, makes me suspect that the wing was not condusive to wing mounted armament. This is an additional reason to limit KI-43 production and focus on A6M production. To address Takao's suggestion of wing mounting vs cowl mounting, I agree in general. A wing mounted 12.7mm will have over twice the RPM of a cowl mounting which means more rounds and greater lethality during the small window of opportunity when our pilot has the enemy in his gun sights. In the A6M type I would favor retaining the cowl mount in addition to the wing mounts because it gives us in effect one additional 12.7mm gun (2 x 12.7mm cowl mounted guns at 400 rpm=1 x wing mounted gun firing at 850 rpm).
One of the other issues we have is that the HO-103 in order to be made lighter uses a smaller .50 caliber round than the .50 caliber browning it was designed from. The HO-103 uses a 12.7mm x 81SR round and the US AN/M2 browning uses a more powerful 12.7mm x 99 round. Here we encounter the issue of weight the HO-103 weighs 48 lbs the AN/M2 61 lbs, the HO-5 20mm weighs just 72 lbs but has much greater lethality. We can adopt a direct copy of the M2 to increase our firepower or we can just go ahead and upgrade to the 20mm HO-5 when we get more powerful engines. The downside is ammunition weight, and then the size of the individual round decreases the amount of ammunition that can be carried. In the KI-43 that carried a mixed 7.7mm/12.7mm configuration the rounds carried were 500rds/270rds.
You can find an intersting discussion of the KI-43's armament here:
http://www.j-aircraft.com/research/rdunn/nakajima_ki43arm.htm

 

Is there any merit to attempting to strengthen the Ki-43's wing to allow it to incorporate wing mounted guns?

 

Belasar wrote:

I honestly don't know. I have long suspected that the wing is very narrow in profile and gun/ammunition bays in it would probably require fairing, which would disrupt airflow changing it's excellent handling characteristics. But, this is just a guess. Besides, if we adopt the A6M series across the board we don't have to "re-engineer" this aircraft when our goal is consolidation of types.