Mitsubishi A6M1 Zero

Part of the first wave of great World War II fighters, the first flight of Mitsubishi’s famous Zero came on April 1, 1939.

Let’s take a look at an important type that was so secret it was almost entirely unnoticed at first.

Starting in 1937 the Imperial Japanese Navy issued an order for a new fighter to replace the Mitsubishi A5M, which was just entering service. They sent their “12-shi” list of requirements to both Mitsubishi and Nakajima. The requirements were pretty ambitious for the time, They wanted a top speed over 310 mph, climb to 10000 feet in less than 10 minutes, an endurance of 6-8 hours with drop tanks, and armament of 2 x 20 mm cannon.
Further, the new type had to equal or exceed the maneuverability of the A5M and be the same size (to fit on aircraft carrier elevators).

The wise engineers at Nakajima concluded the requirements were unattainable and withdrew from the bid. Mitsubishi’s chief engineer, Jiro Horikoshi, thought it was doable but not easily. It would require extraordinary weight control and a new top secret aluminum alloy called “extra-super duraluminum (ESD)”. This was a remarkable new alloy, with superior weight to strength numbers; it was however prone to rapid corrosion and fatigue (which has some impact on why so few Zeros are still airworthy and is a constant headache for their owners).
The rest of the formula behind the new A6M is well enough known, very light construction and painstaking attention to a streamlined form.
Armor for the pilot and self sealing fuel tanks were just becoming standard in most of the world but Horikoshi’s fighter was light in every sense, which not only meant such features were not used but that it would require more than a “simple” fix when it was accepted that they were needed.
The pilot’s canopy was a revolutionary feature that often gets overlooked. Obviously not a true “bubble”, but the seat was high and the canopy allowed a 360 degree view. As revolutionary as the Hawker Typhoon’s bubble is often considered, the Zero was practically there first.
The wide undercarriage and low speed wing were all about making the Zero a superb carrier aircraft. That wing design also made the type supremely maneuverable at low speeds.

As so often happens, several of the prototype’s features were changed before series production. The two bladed propeller was found to cause concerning vibrations and was replaced with a three bladed unit within a few weeks (I suspect the original propeller also failed to capitalize on the engine’s full output). The second prototype was also delivered with a two bladed propeller, but also not for long. The engine was initially Mitsubishi’s own Zuisei; it was rated at 850 hp, but it struggled to perform as advertised (perhaps due to a supercharger that was also problematic). The Navy insisted on a switch to Nakajima’s more reliable Sakae engine, this technically defines the difference between the A6M1 and production model A6M2 aircraft.
Both prototypes came with an “anti-spin” ventral stabilizer in the place where the tail hook would eventually be mounted. I find this an amusing story, Horikoshi was apparently quite annoyed that the company had added this thing that he felt did nothing, and ruined the fine lines of his airplane. I believe we only know about this because the designer went off on the subject in a post-War book he wrote on the development of the Zero; but no photos or engineering drawings of the fin survive (as far as I know). When Hasegawa kitted the A6M1 (2000 or 2010? It was to celebrate one of the Zero’s anniversaries) they included the stabilizer, and helpfully had different profiles for the first and second prototype. So how do they know? Maybe they found an eyewitness or interview I know nothing about? I think I’ll have to call this feature speculative.
Also note the model shows armament. Granted, for the 20 mm cannon that just means some holes in the wings; but the 7.7 mm machine guns are visible in the cockpit and the barrels exit the fuselage just before the cowling. Now I do know that eventually this plane WAS armed. The first prototype was turned over to the Navy in September 1939 and was doing gunnery tests in November. But it seems odd to me if it made its first test flights armed? And the two bladed propeller was only used for about six weeks. So let’s say for our purposes here it was armed, or at least had realistic dummies installed for weight and balance reasons! That’s my story and I’m sticking to it…

Its also worth mentioning the new Type 99 20 mm cannon used on the A6M. Through the 1930s most of the World was still using light caliber machine guns in their fighters, usually two light machine guns just like at the end of World War I. In the mid-1930s it was becoming apparent to many that with faster speeds and more rugged aircraft that it might not be adequate for a future conflict. A Japanese naval observer in France saw the new 20 mm cannon by Swiss manufacturer Oerlikon and pushed for its adoption. By 1937 the Navy had decided on licensed manufacture of that weapon. The Type 99 was developed for the Japanese by Oerlikon engineers working in Japan. It was specifically light in keeping with the whole theme of the Zero. Later derivatives were heavier and improved muzzle velocity and rate of fire. In December of 1941 the Oerlikon engineers were arrested like most other westerners and spent the remainder of the War incarcerated.

The anti-spin stabilizer is visible just below horizontal stabilizer where the tail hook would normally be. Its shape as depicted is conjectural.

This aircraft represents the first of the two A6M1 prototypes. Chief designer Horikoshi gushed over its beauty. Obviously a bit of a bias; but he was also the chief designer of the A5M (Claude), G4M (Betty), F1M (Pete), A7M (Sam), Ki-51 (Sonia) and many others. As far as I know he only gushed over the Zero. The Mitsubishi plant was located some 30 miles from the nearest airfield, via unpaved roads. So the plane was crated and transported by ox cart, taking a full day. (This situation was never rectified. To the end of the War Mitsubishi’s output was dependent on ox carts and healthy, well fed beasts).
From the first flight on April 1, 1939 the pilot was pleased with the aircraft. There were tweaks and modifications, as there always are, but the basic form remained unchanged for production. After completing basic flight testing, both prototypes were accepted by the Navy for more advanced testing including radios, weapons and other military equipment.

A5M4 and A6M1. Both came from the mind of Jiro Horikoshi, but share little family resemblance. The Zero was technically the Claude’s replacement, but this A5M4 was built after the A6M1.

As mentioned earlier, this is the Hasegawa kit. It is an easy build and I left it mostly clean, like its ready to go for that first flight.

The A6M1 prototype with a production A6M2. Apart from the bigger engine, there are changes to the tail and all control surfaces.

About atcDave

I'm 5o-something years old and live in Ypsilanti, Michigan. I'm happily married to Jodie. I was an air traffic controller for 33 years and recently retired; grew up in the Chicago area, and am still a fanatic for pizza and the Chicago Bears. My main interest is military history, and my related hobbies include scale model building and strategy games.
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9 Responses to Mitsubishi A6M1 Zero

  1. For such a nation you’d have thought they would have a better transport system than ox and cart!

    • atcDave says:

      No doubt!

    • Ernie Davis says:

      It boggles the mind. But then the German army relied on horse drawn artillery throughout the war and most infantry units were also supplied by horse. Only about 1 in 5 units in the German army was fully mechanized.

      Still, disassembling planes and shipping by oxcart does seem to rise to the next level of “The Webster Test”. What were you thinking?

      • atcDave says:

        You know I do agree!
        I do have to admit I parsed that about as badly as I could for the Japanese. The factory did have rail, and I believe shipping access. But because of the intended assembly point at an airport they chose the unpaved road option. They DID have trucks, but Mitsubishi chose oxcarts in the belief it was a less jarring ride and the aircraft would arrive in better condition.
        Its also worth mentioning Nakajima was the preferred supplier by both the Army and Navy for exactly this issue; they had bigger and better developed facilities. Nakajima not only built more than half of all Japanese aircraft, they also built about 2/3s of all A6Ms. Unlike the US, the Japanese made no distinction in designation based on the manufacturer. So its often tricky to know if a particular Zero was built by Mitsubishi or Nakajima (this really only matters to a modeler for the colors used). Kind of a familiar story for wartime industry, Nakajima ultimately profited handsomely on the “12-Shi” project that they had previously backed out of for being unreasonably ambitious.
        Mitsubishi was a smaller company (in the Japanese conglomerate sense of the word), that was extremely fortunate through the 1930s and ’40s to have a remarkably talented team of engineers under Jiro Horikoshi.

        Which is a long way of coming back to “what were they thinking”?! Any similar American project would have certainly included a long look at the infrastructure issues and improvements of whatever sort were needed. It is seriously amazing to read about Mitsubishi having to argue for keeping the their oxen fed as a priority part of fighter production, but there it is.

      • Ernie Davis says:

        Kind of why jeeps weren’t all made by Bantam in Butler, PA.

      • atcDave says:

        Yes exactly!

      • Ernie Davis says:

        It is funny though, how the feeling of craftsmanship survived so many of the Axis war programs. I think we talked about this also with one of the Italian planes.

        I recently re-watched Ford vs. Ferrari (worth a look if you haven’t seen it, though you are from Michigan so…). I also toured the Ferrari plant a few years ago. They still make fewer cars in a year than Ford makes in a day. But they are really fine looking cars.

      • atcDave says:

        Yes, in fact I was just looking at some of the thoughts on US evaluations of the Zero and exactly along those lines, many were very impressed with the pure craftsmanship of the Japanese fighter.

        And yes I loved Ford vs Ferrari! Outstanding movie. There is no shortage of auto nerds around these parts and everyone I know loved that film. Some of the jabs between Ford and Ferrari still ring true; so there was a sort of odd feeling of rooting for the underdog and home team. Fun time. Really fun with my father-in-law, he’s really into NASCAR and auto sports in general, but he knew nearly nothing about European type racing. So he was on the edge of seat enjoying and not knowing the story.

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