Japanese fighter structural strength

[Jukka Juutinen]

Were IJNAF and IJAAF fighters designed to similar structural specs? What were the allowed g-limits and VNE of e.g. the J2M3?

[Jim Oxley]

I'm not quiet sure what it is that you are after Jukka, but here's some info for you to consider.

There was no 'agreed' set of specifications between the IJNAF and the IJAAF. Co-operation between the relevant Air Arms did not, and rarely would, exist at a command level. And there are a number of reasons for this development.

Each service considered that it was the primary defender of Japan. Both used their air arms for political positioning and point scoring, right for the start in 1910 when two Army Officers were sent to Europe to learn to fly. When they returned in December of that year The IJA then offered to teach officers from the IJN to learn to fly. The IJN refused. Instead it sent three officers to France and three to the US in 1912 to learn to fly, purchase aircraft and to learn to maintain them.

In the 1930's each Service, as a way of gaining power within the burgeoning aircraft industry, created it's own pool of machine tools. They then loaned or leased these tools to a prospective manufacturer in accordance with their needs. A stipulation was that Army tools could not be used for Navy aircraft , and visa versa. Each service went so far as to establish technical advisers at each manufacturer to monitor this.

Following on from the above each Service sought to control basic raw material allocation and civilian labour forces. The situation became so bad that the Government had to set up a new Ministry - Munitions - to control and administer all things pertaining to production of war material. And this was in 1943!

Each Service also developed it's own air development unit- the Koku Hombu for the IJAAF and the Kaigun Koku Hombu - responsible for aircraft design and development, aircraft engines, equipment selection, gun research and testing as well as supervision of training of flight and maintenance personnel.

Another factor that prevented any form of co-operation on aircraft development relates to the military function of each Service, and the design philosophy by that Service of how it's aircraft will help it fulfill that requirement.

The IJAAF saw it's role primarily as that of support for it's land forces. In the 30's it's focus and War plans was on China and the Soviet Union. Hence range wasn't as great a factor as that of ease of maintenance and ability for aircraft to operate from poor airfields.

The IJNAF focused on the protection of trade routes, and the Western colonial powers. So range was a major factor, as was strength as aircraft had to operate from Carriers.

In the late 30's both air arms developed excellent aircraft leading into WWII. The IJAAF had the Ki-43 Hayabusa and the IJNAF the A6M2 Zero. Both were outstanding aircraft, and each reflected it's parent Services needs. Both had amazing manoeuverability (a Japanese Pilot fetish in that period), but structurally they were very different. The Ki-43 was very light, designed for ease of maintenance and speed of production. The A6M was far more robust, yet still unemcumbered by 'western' attachments so as to have phenomenonal range and striking ability.

For example the Ki-43-1c was limited to 5 G pullouts on dives, the A6M2 to 6G. VNE in a dive for the Ki-43-1c was 280 kts and the A6M2 to 320 kts. Later models of both had higher limitations.

Whereas the IJNAF failed to initiate development research at an early stage for a Zero replacement, the IJAAF already had two aircraft in the wings to follow the Ki-43.

The first was a radical departure from current thinking. The Ki-44 Shoki was fast, heavy, had punch and was limited in manoeuverability. But it could climb rapidly and dive faster than anything the IJAAF or the IJNAF had on the books. And it was already being combat trialled at the same time as the Ki-43 was entering full service. The second aircraft was the excellent Ki-61 Hein. faster than the Shoki, more manoeuverable, less taxiing to fly, it was superior to both the Ki-43 and the Ki-44. In turn the Koku Hombu use dthe information gained by the Ki-61 in to the development of the Ki-84, perhaps the best of the Japanese fighters per se.

The IJNAF did come to realise that the A6M Zero was sadly outdated, but was so slow in bringing to friution a replacement aircraft that the Zero had to labour on until wars end.

[Jukka Juutinen]

Interesting info! But 5 g limit with the Ki-43? That´s lower than some WW One fighters...