Mitsubishi J2M

The Mitsubishi J2M Raiden (雷電, "Thunderbolt") was a single-engined land-based fighter aircraft used by the Imperial Japanese Navy Air Service in World War II. The Allied reporting name was "Jack".

Design and development
The J2M was designed by Jiro Horikoshi, creator of the A6M Zero to meet the 14-Shi (14th year of the Showa reign, or 1939) official specification. It was to be a strictly local-defense interceptor, intended to counter the threat of high-altitude bomber raids, and thus relied on speed, climb performance, and armament at the expense of manoeuvrability. The J2M was a sleek, but stubby craft with its over-sized Mitsubishi Kasei engine buried behind a long cowling, cooled by an intake fan and connected to the propeller with an extension shaft. Pilot visibility was poor, but a domed canopy introduced later in production partially alleviated this concern.

Teething development problems stemming from the Kasei engine, unreliable propeller pitch change mechanism and the main undercarriage members led to a slowdown in production. A continual set of modifications resulted in new variants being introduced with the ultimate high-altitude variant, the J2M4 Model 34 flying for the first time in August 1944. It had a 1,420 hp Kasei 23c engine equipped with a turbo supercharger (mounted in the side of the fuselage just behind the engine) that allowed the rated power to be maintained up to 30,000 ft. Two upward-aimed, oblique-firing (aimed at seventy degrees) twenty mm cannons, mounted in the German Schräge Musik style, were fitted behind the cockpit with the four wing cannons retained. Unresolved difficulties with the turbo supercharger caused the project to be terminated after only two experimental J2M4s were built.

Production
A total of 621 aircraft were built by Mitsubishi Jukogyo K.K in Nagoya and Suzuka plants. A total of 128 J2M3s were built by Koza Kaigun Kokusho (Koza Naval Air Arsenal) based upon USSBS Pacific War, Reports Nos. 16 and 34)
 * J2M1 - eight aircraft.
 * J2M2 - 131 aircraft. (approximately)
 * J2M3 - 307 aircraft built by Mitsubishi and 128 aircraft built by Koza KK.
 * J2M4 - two aircraft. (including one J2M3 converted to J2M4 standard)
 * J2M5 - 43 aircraft.
 * J2M6 - two aircraft.

Operational history


The first few produced J2M2s were delivered to the development units in December 1942 but severe problems were encountered with the engines. Trials and improvements took almost a year and the first batch of the serial built J2M2 Model 11 was delivered to 381st Kokutai in December 1943. Parallel with the J2M2, production of the J2M3 Raiden Model 21 started. The first J2M3s appeared in October 1943 but deliveries to combat units started at the beginning of February 1944.

The Raiden made its combat debut in June 1944 during the Battle of the Philippine Sea. Several J2Ms operated from Guam and Saipan and a small number of aircraft were deployed to the Philippines. Later, some J2Ms were based in Chosen airfields, Genzan (Wonsan), Ranan (Nanam), Funei (Nuren), Rashin (Najin) and Konan under Genzan Ku, for defending these areas and fighting against Soviet Naval Aviation units.

Primarily designed to defend against the Boeing B-29 Superfortress, the lack of a turbocharger handicapped the aircraft at high altitude. However, its four-cannon armament supplied effective firepower and the use of dive and zoom tactics allowed it to score occasionally. Insufficient numbers and the American switch to night bombing in March 1945 limited its effectiveness.

Two captured J2Ms were U.S. Technical Air Intelligence Command (TAIC) tested using 92 octane fuel plus methanol, with the J2M2 (Jack11) achieving a speed of 655 km/h (407 mph) at 5,520 m (17,400 ft), and J2M3 (Jack21) achieving a speed of 671 km/h (417 mph) at 4,980 m (16,600 ft).

Variants

 * J2M1
 * Prototype fitted with the 1,044 kW (1,400 hp) Mitsubishi MK4C Kasei 13 14-cylinder air-cooled radial engine, and armed with two 7.7 mm (.303 in) Type 97 machine guns in the upper fuselage and two wing-mounted 20 mm Type 99 Model II cannon.


 * J2M2 Model 11
 * Fitted with the 1,379 kW (1,850 hp) Mitsubishi MK4R-A Kasei 23a 14-cylinder radial engine, same armament as the J2M1.


 * J2M3 Model 21
 * Mitsubishi MK4R-A Kasei 23a engine, two wing-mounted 20 mm Type 99 Model II cannon and two wing-mounted 20 mm Type 99 Model I cannon.


 * J2M3a Model 21A
 * Mitsubishi MK4R-A Kasei 23a engine, four wing-mounted 20 mm Type 99 Model II cannon.


 * J2M4 Model 32
 * Prototype fitted with the 1,357 kW (1,820 hp) Mitsubishi MK4R-C Kasei 23c engine. Many armament configurations have been reported, e.g., fuselage-mounted oblique-firing 20 mm Type 99 Model I cannon designed to fire upward as it passed underneath a bomber, two wing-mounted 20 mm Type 99 Model II cannon, and two wing-mounted 20 mm Type 99 Model I cannon (some J2M3s were also modified in the field to this configuration). However, no solid evidence exists that the prototypes ever flew armed.


 * J2M5 Model 33
 * High altitude version powered by 1,357 kW (1,820 hp) Mitsubishi MK4U-A Kasei 26a engine with mechanically driven supercharger, giving increased speed at height at the expense of shorter range (just over half that of the J2M2 and J2M3). Two 20 mm Type 99 cannon in fuselage, two 20 mm Type 99 Model II cannon in wings.


 * J2M5a Model 33A
 * Four wing-mounted 20 mm Type 99 Model II cannon. Now, all four wing cannon were harmonized in trajectory and ballistics performance like the Kawanishi N1K-J Shiden fighters, but with more ammunition than they had (200 v. 70-125 rpg). The 20x101 mm cartridge gave the 128 g HE (6-8%) projectile an effective range of 1,000 m (3,280 ft) and a muzzle velocity of 750 m/s. The rate of fire was only 500 rpm each however (down from 520 rpm for the Type 99 Model I which only had a muzzle velocity of 600 m/s and a range of 730 m/2,400 ft with its 20x72 mm cartridge).


 * J2M6 Model 31
 * Chronologically earlier than J2M4 and J2M5 this version was based on J2M3. Had wider cockpit and improved bubble canopy later used in J2M3 built since July 1943.


 * J2M6a Model 31A
 * Chronologically earlier than J2M4 and J2M5 this version was based on J2M3a. Had wider cockpit and improved bubble canopy later used in J2M3a built since July 1943. One J2M6a was built.


 * J2M7 Model 23A
 * J2M3 powered by Kasei 26a engine, none built.


 * J2M7a Model 23A
 * J2M3a powered by Kasei 26a engine, none built.

Survivors
A surviving J2M is on display at the Planes of Fame museum in Chino, California.

Operators

 * Imperial Japanese Navy Air Service
 * 256th Kokutai November 1944 - December 1945
 * 301st Kokutai February 1944 - July 1945
 * 302nd Kokutai March 1945 - August 1945
 * 332nd Kokutai August 1944 - August 1945
 * 352nd Kokutai August 1944 - August 1945
 * 381st Kokutai End 1943 - April 1945
 * Yokosuka Kokutai
 * Yatabe Kokutai
 * Genzan Kokutai
 * Tainan Kokutai
 * Konoike Kokutai
 * Chushi Kokutai
 * Chushi Kokutai