How To Build a Zero (1945)

by Bill Sweetman
Apr 08, 2015

First published on Aug. 1, 1916 as Aviation and Aeronautical Engineering, the magazine's title has changed over the years to reflect its readership base and the industries it serves. It changed to Aviation, Aviation News, Aviation Week then became Aviation Week Including Space Technology in 1958 before finally changing to its current title, Aviation Week & Space Technology, in 1962.

Newsprint rationing clearly wasn't a big issue in the U.S. in May 1945, when our predecessor title Aviation published an ultra-detailed four-part dissection of Japan's "workhorse fighter", the Mitsubishi A6M Zero, with detail that would put some homebuilt-airplane plans to shame. Neither was cultural sensitivity, as the cover wording shows. 

The piece was based on examination of a little-produced variant, the A6M3 Model 32. The U.S. had acquired its first flyable Zero, a Model 21, in 1942, an aircraft that force-landed intact on Akuta Island in the Aleutians, but flipped inverted on soft ground, killing its pilot. The Model 32 was an anomaly -- the Sakae 21 with a two-speed supercharger replaced the original Sakae 12, but to accommodate the longer engine the firewall was moved aft, sharply reducing internal fuel capacity. The speed increase from the more powerful engine was less than expected and not considered worth the loss in range. 

The Model 32 was assigned a new codename -- originally "Hap" in honor of US Army Air Force commander Gen. Hap Arnold. However, nobody had asked Arnold what he thought about this, and his view was highly negative. The name was changed to "Hamp", but the A6M3 was more often called Zeke 32 because it was clearly a Zero variant. (Names like Zeke, Rufe, Mavis and Myrt were the work of an intelligence officer who had grown up in rural Tennessee.) 

However, the analysis hits on the key difference between the A6M and its contemporaries: an emphasis on range and lethality. As detailed by designer Jiro Horikoshi in his book Eagles of Mitsubishi, the Navy's requirement for speed and maneuverability comparable to emerging European designs (the Spitfire, Hurricane and Bf109 had all flown by the time the Zero project started), combined with unprecedented range and 20-mm. cannon armament, seemed impossible given the modest power of the biggest available engine. "I dropped into my chair as I tossed the document on my desk," Horikoshi wrote as he recalled reading the initial requirements document. "Just glancing at the requirements was enough to make me feel gloomy." 

What emerged was a highly refined design. Weight control was rigorous: Horikoshi wrote that "it was our policy to control anything heavier than 1/100,000th of the aircraft's final weight". Rather than using a single standard load factor, Horikoshi realized that some slender, flexible components could be made lighter without compromising the structure. 

Wingspan was limited by carrier compatibility, but rather than taking the weight hit of a fully folded wing, Horikoshi's team elected to fit short, light folding tips. Armament comprised two 20-mm. cannon and two machine guns: lethal in the hands of an expert, but with a low rate of fire that made it hard for a less skilled pilot to consistently hit the target.

The design stressed low-speed maneuverability, at the price of heavy controls at higher speed. Above all, the Zero had outstanding range, and appeared in places where its adversaries did not expect it; and early lessons learned by the Flying Tigers, the mercenary American Volunteer Group, were ignored. In the early air battles of the Pacific War, the Zero quickly became a feared adversary. 

Aviation's story -- quite possibly at the behest of the military -- misses one key to the Zero's success: its construction made use of high-zinc-content 7075 aluminum alloy, which had been secretly developed by Sumitomo and was significantly lighter than the 24S alloys used in the U.S. Better metals were not used worldwide until after the war. 

The key lesson learned in early Allied defeats was to never try to engage a Zero at low speed. The crucial U.S. advantage as the war continued was the availability of more powerful engines such as the Pratt & Whitney R-2800, the turbocharged Allison V-1710 in the P-38 and the two-stage-supercharged V-1650 Merlin in the P-51. That made it possible to combine range, maneuverability, high-rate-of-fire armament and protective measures (self-sealing fuel tanks and armor) in later fighter designs. Combined with "boom and zoom" tactics, and the steady attrition of Japan's pre-war cadre of highly trained pilots, that sealed the balance of airpower in the Pacific. But it doesn't make the Zero any less of an achievement. 

And how many aircraft designers have been the subject of Oscar-nominated animated films? 

► Read the article from the May 1945 issue of Aviation:

Design Analysis Of The Zeke 32 Hamp (part 1)

Design Analysis Of The Zeke 32 Hamp (part 2)

Design Analysis Of The Zeke 32 Hamp (part 3)

Design Analysis Of The Zeke 32 Hamp (part 4)

► Aviation Week is approaching its 100th anniversary in 2016. In a series of blogs, our editors highlight editorial content from the magazine's long and rich history, including viewpoints from the industry's most iconic names and stories that have helped change the shape of the industry.

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