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, the 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.
Teething development problems stemming from the Kasei engine cooling system, 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 9,100 m (29,900 ft) Two upward-aimed, oblique-firing (aimed at seventy degrees) 20 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 J2M4's were built.
The first few produced J2M2's 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 Kōkūtai in December 1943. Parallel with the J2M2, production of the J2M3 Raiden Model 21 started. The first J2M3's 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 J2M's 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 defence of 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 J2M's, a J2M2 and a J2M3, were tested by the U.S. Technical Air Intelligence Center (TAIC), using 92 octane fuel plus methanol, with the J2M2 (Jack Model 11) achieving a speed of 655 km/h (407 mph) at 5,520 m (17,400 ft), and J2M3 (Jack Model 21) achieving a speed of 671 km/h (417 mph) at 4,980 m (16,600 ft).
- 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. - Eight builds.
- J2M2 Model 11: Powered by 1,379 kW (1,850 hp) Mitsubishi MK4R-A Kasei 23a 14-cylinder radial engine, same armament as the J2M1.
- J2M3 Model 21: Armed with two wing-mounted 20 mm Type 99 Model II cannon and two wing-mounted 20 mm Type 99 Model I cannon.
- J2M3a Model 21A: Armed with four wing-mounted 20 mm Type 99 Model II cannon.
- 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.
- J2M5 Model 33: High altitude variant 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. Two 20 mm Type 99 cannon in fuselage, two 20 mm Type 99 Model II cannon in wings.
- J2M5a Model 33A: Armed with four wing-mounted 20 mm Type 99 Model II cannon. Wing cannon were harmonized in trajectory and ballistics with each 200 rpg.
- 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.
- Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970. ISBN 0-370-00033-1. (2nd edition 1979, ISBN 0-370-30251-6).
- Green, William. Air Enthusiast Magazine, Quarterly Volume 1, Number 2 Bromley, Kent: Pilot Press Ltd, 1971.
- Green, William. Warplanes of the Second World War, Volume Three: Fighters. London: Macdonald & Co. (Publishers) Ltd., 1973, First edition 1961. ISBN 0-356-01447-9.
- Pęczkoski, Robert, Mitsubishi J2M Raiden "Jack". Redburn: Mushroom Model Publications, 2004. ISBN-10: 83-916327-7-6 ISBN-13: 978-83-91632-77-2.
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