Mitsubishi J2M Raiden, part one

 

The Mitsubishi J2M Raiden was designed by Jiro Horikoshi, the creator of the Mitsubishi A6M Zero to meet the 14-shi official specification calling in 1939. This specification called for a strictly local-defense interceptor, to defend against high-altitude bomber raids. To meet that requirement, the proposed fighter had to rely on speed, climb performance and armament sacrificing maneuverability. The J2M was a sleek, but stubby aircraft with its oversized Mitsubishi Kasei engine buried inside a long cowling and cooled by an intake fan which was connected to the propeller with an extension shaft.

Work on the project began in March 1940 and, back then, it was very innovative by Japanese standards. It featured a low wing with symmetrical airfoil and slotted flaps with a very low cockpit, to minimize drag. The prototype was powered by a single 1.460 hp Mitsubishi Kasei radial engine mounted in a very slim cowling with a small air intake. This, forced the designers to use a fan to achieve proper cooling. 

All those innovations resulted in serious delays in work on the prototype. Furthermore, with Horikoshi concentrating on development of the A6M Zero, Kiro Takahashi, had to take the lead on the development team, remaining in overall control of the project.

It wasn't until March 1942 that the prototype was completed and the first flight, from Kagamigaura airfield, in Chiba, Japan, took place on 20th May. A total of 8 development prototypes were built.

The J2M2 Model 11 was the first production version, which flew for the first time in October 1942. It featured a redesigned cockpit and a Kasei engine with better cooling system and individual exhausts. A total of 131 machines (155 according to other sources) of this variant were manufactured (which were also heavily field-modified to reduce engine vibration) between October 1942 and 1943, including the fourth prototype, which was the pattern for production aircraft. 

The J2M3 Model 21 was another version with improved armament. The fuselage-mounted machine guns were discarded in favor of two additional cannons in the wings, making the airplane to be armed with two 20 mm Type 99 Model 1 and two 20 mm Type 99 Model 2 cannons. In order to fit the additional cannons, the wings had to be strengthened. It also featured improved armor protection. All those changes made a heavier airplane, with the subsequent performance decrease. When the new framed cockpit of the J2M6 was tested, some J2M3 were retroactively fitted with that new cockpit frame.

It also had a sub-variant, called J2M3ko Model 21ko, which replaced the two wing-mounted Type 99 Model 1 cannons with Type 99 Model 2 cannons placed in underwing pods. Twenty-one machines of this sub-variant were built.

In total, counting all sub-variants, 307 J2M3 were manufactured (438 according to other sources) by Mitsubishi at Nagoya and Suzuka and Koza Naval Aviation Workshop from February 1944 to July 1945.

Sources:

1. https://en.wikipedia.org/wiki/Mitsubishi_J2M

2. Mushroom Model Magazine - Yellow Series 6110 - Mitsubishi j2M Raiden 'jack'

3. https://www.valka.cz/Micubisi-J2M-Raiden-Jack-t28908