Why no wing armament for the Ki-43?

[windswords]

One thing that has always puzzled me is why no wing guns were ever mounted on the Ki-43. It's not like the IJAAF didn't know how - both the Ki-44 and Ki-61 had wing armament from the beginning and they were in production within a year to a year and a half of the Ki-43 going into service. I suspect it must be the location of wing fuel tanks or something similar. If someone knows for certain please share.

Thanks

 

[buffnut453]

An evolutionary issue? The Ki-27 it replaced only had 2 machine guns in the fuselage so maybe that was the specified armament load for the Ki-43. The Ki-43's wings were never stressed to take guns in the wings, indeed even then the early Ki-43-Is suffered from wing surface wrinkling due to combat manoeuvres.

 

[Shortround6]

Later ones got under wing bombs.

The Japanese type 89 7.7mm mg was based of the British Vickers and the Vickers did not have best reputation for reliability, durability yes. The British would not mount the Vickers where the pilot could get to it, even it it was just beat on it with his fist. This was the major reason the British went with the Browning.
I could be wrong but I think the Japanese only used the type 89 7.7mm mg in the wings of a few planes.
The Ho 103 was more often used in the wings but was a larger, heavier gun (although smaller and lighter than the US .50). Perhaps the Japanese didn't want to take the performance hit of a pair of Ho 103s in the wing. A pair of guns with just 200rpg goes about 79kg without links, ammo boxes/chutes, mounts, local reinforcement, charging systems, etc. Not a lot of weight but then the Ki-43 didn't have a lot of power.

 

[buffnut453]

Even the Ki-43-I had provision for underwing drop tanks. Japanese fighters do seem a little under-gunned. Even the vaunted A6M struggled with the limited ammo and rate of fire of it's cannon.

 

[Shortround6]

Early in the war there was shortage of Ho 103 guns (or ammo?) with many Ki-43s equipped with one gun in each caliber.

 

[windswords]

Later ones got under wing bombs.

Perhaps the Japanese didn't want to take the performance hit of a pair of Ho 103s in the wing. A pair of guns with just 200rpg goes about 79kg without links, ammo boxes/chutes, mounts, local reinforcement, charging systems, etc. Not a lot of weight but then the Ki-43 didn't have a lot of power.

I see the logic in your statement but I have to point out that the Ki-43 used the same engine (Nakajima Ha-25) that the Zero did and the Zero had 20 mm cannons in the wings which did not hamper it's performance in any way. That is why I think it has something to do with the actual structure of the wings internally (if you look at any drawings of the wings of the Ki-43 they don't look any less thick than other contemporary fighters of the day).

 

[Elmas]

In mid-thirties cantilever wings that relied in D-boxes formed by the longeron and a stressed skin up to the leading edge for torsional stiffness were on their infancy, and so the Technical Branch of various Air Forces, that tend to be generally very conservative, tought that the stiffness of the wings was insufficient to permit the installation of guns. Of course, if a wing has a torsional movement, even small, shooting is impossible.
This happened, for example, for the Italian fighters Macchi MC 200 and Fiat G 50.
When afterwards Engineers and Technical Staff realized that wings were much stiffer than they tought, guns were set there: the wing of Macchi MC 205, with one 20 mm Mauser in each, was not very different, structurally, from that of Macchi MC 200.

 

[Shortround6]

I see the logic in your statement but I have to point out that the Ki-43 used the same engine (Nakajima Ha-25) that the Zero did and the Zero had 20 mm cannons in the wings which did not hamper it's performance in any way. That is why I think it has something to do with the actual structure of the wings internally (if you look at any drawings of the wings of the Ki-43 they don't look any less thick than other contemporary fighters of the day).

I could very well be wrong. Perhaps the Japanese Army had different standards than the Navy? I believe the Army was not happy with the decrease in maneuverability from the Ki-27 to the Ki-43 until Nakajima fitted the flaps with an 8 degree combat setting?
The Ki-43 was usually considered even more maneuverable than the Zero.

 

[windswords]

Shortround6,

You are correct about the IJAAF's assessment of the Ki-43's maneuverability, therefore the addition of the "butterfly" flaps. But at some point in the war it would be apparent that twin 12.7mm machine guns were too light of an armament. So, initially not having wing guns could be for maneuverability but later they could have put guns in the wings - yet they didn't. So it must be something about how the wings were constructed internally.

 

[Shortround6]

I have looked at a couple of drawings (how accurate vs artists imagination?) and the Ki-43 used a three spar wing . Forward spar was behind the landing gear. Middle/main spar was in the middle of the wing and lined up with a forward cockpit bulkhead/frame about where the canopy joint between the fixed and sliding part was. Rear spar was inline with the the fuselage frame about in line with the rear of the pilots seat. This spar was forward of the point/s at which the ailerons and flaps attached/hinged. There were fuel tanks between the forward and main spar and between the main and rear spar but they did not extend out past the landing gear. I don't know if there was room for the receiver of the ho-103 between the spars. Putting hole for a gun barrel is one thing. making a hole for a receiver is another. Or maybe they didn't have enough ho-103s to go around as it was?

 

[windswords]

I think you are on to something, Shortround6. Did not most fighter aircraft have one spar in the wing? Three sounds like there was not room for both the gun barrel and the receiver. And then there is the ammo drum or belt. Do multiple spars make a wing stronger? I don't remember reading that the Ki-43's wing was stronger than any of its contemporaries.

 

[Shortround6]

P-40 had 5 spars but then they counted the mounting plates/beams used as hinge points for the ailerons and flaps as spars. Multi-spar wings use more light spars rather than one or two large heavy spars so it is very hard to make judgement on weight or strength based on the number of spars alone. Strength (and weight) could also come form the wing skin. The Japanese Zero twice had it's dive speed upgraded by using heavier sheet metal on the wing skins.

The Japanese also had a real problem with a shortage of engineers. If the ones they had were working on new designs (KI-44 and Ki-84) then they weren't available for even minor work on the old the designs. Or if they worked on upgrading the older designs it delayed the new ones. For instance Mitsubishi started work on a replacement for the Zero at the end of 1940, due to problems with engine development and having to assign the engineers to upgrading the A6M Zero at least once the first prototype didn't fly until May of 1944. Final version wasn't standardized until Oct/Nov of 1944.

I have no idea which, if any (or all?), of these factors affected adding to the armament of the Ki-43 although the last 2 prototype aircraft had Mitsubishi Ha-112 engines (Kinsei) like the Ki-100 but lower rated and a pair of 20mm cannon in teh fuselage/cowl. Still no wing guns.

 

[Shinpachi]

I've ever heard Ki-43 was more fragile than A6M when it was requested good maneuverability like Ki-27 and two accurate machine guns mounted in the fuselage were considered enough. If this was true, that would be because Ki-43 was genuinely designed as land-based fighter while A6M as carrier fighter.

Ki-44 was to fulfill Ki-43's disadvantage with higher speed and heavier armaments but regrettably most pilots and IJA preferred old fashioned air combat as the hit-and-run tactics looked coward though Nakajima predicted new era with the Ki-44.

This situation had happened because IJA did not imagine that they would have to fight with more advanced sturdy US fighters in the future. Needless to say, so was IJN.

 

[windswords]

I hear what you are saying Shinpachi, but when it became apparent the Ki-43 needed more guns it didn't get it. Even the A6M5c got 2 extra 13.1 mm machine guns in the wings for a total of 2 cannons and 3 heavy machine guns. I still think there was something about the internal construction of the wing that did not allow for putting guns there.

 

[Shinpachi]

Situation was simple, windswords.

1. The Ki-43 was built with the minimum strength for the 2 fuselage machine guns.
2. Nakajima had designed the wing with 3 spar unfortunately as wing guns were thought unnecessary.
3. Nakajima had no time and manpower enough to redesign it any more when the Pacific War had started.

 

[CharlesBronson]

I would say because japanese aircraft designers were somewhat stupid and still thinking in ww1, but maybe that is too daring.

 

[Shinpachi]

I forgot to tell and this may be important.

Ki-43's 3-spar wing came from Ki-27.
Ki-27's wing came from Douglas DC-2.
Nakajima was not familiar with 2-spar wing for the full metal aircraft till Ki-44.

 

[Shortround6]

Actually Japanese aircraft designers were rather smart and innovative.

Remember the aircraft designers were trying to fill requirements put out by the Army and Navy. The Aircraft designers did NOT tell the Army and Navy what to use or how to use it.

What the Japanese did not have was enough designers/engineers/draftsmen to work on numbers of projects at the same time. This was a problem that affected ALL countries to a greater or lesser extent during WW II.
You can teach somebody to rivet or weld in a few weeks. Creating draftsmen takes lot longer and engineers even longer.

 

[windswords]

Shinpachi: The statement about the 3 spar wing backs up what Shortround6 said. The location of the spars made it impossible to put guns in the wing.

As to the Japanese being stupid, no, the designers and engineers came up with some great innovations. The first purpose built anti-submaine patrol aircraft was Japanese (Q1W Lorna). The best flying boat of WWII was Japanese (H8K Emily). The Japanese in less than 10 years went from the Ki-27 Nate to the Ki-84 Frank and from the A5M Claude to the A7M Sam and the J7W Shinden. That's quite an accomplishment. They came up short in industrial capacity and the number of trained engineers and draftsman. You could say that the army and navy were not on the ball because they gave the specifications for aircraft like the Ki-43 emphasizing turning ability above all else not realizing that this type of aerial fighting was soon to be extinct.

 

[Shinpachi]

Thanks for your kind and good understanding, windswords.
Stupid were not Japanese engineers but leaders who did not understand rest of the world.
Pride is necessary but too much pride destroys oneself. It was good lesson