In December 1942 the Naval Staff rejected a new twin-motor G7M1 bomber proposed by Mitsubishi. The attitude of naval leaders towards the firm became noticeably cooler and in February 1943 it was rival Nakajima that received a contract for the development of a Naval Experimental 18-Si Strike Bomber Renzan (“Mountain Range”)G8N1. The requirements for the 18-Si bomber were finalized on September 14, 1943: its speed was to be 590 km/hr, range with 4 tons of ordnance – 4250 km, maximum range – 8500 km. The G8N1 flew for the first time on October 23, 1944. In many respects, the aircraft resembled the American B-29 Boeing Superfortress. Long wings and four supercharged Nakajima NK9K-L Homare-24 engines rated at 2000 hp ensured high cruise speed and altitude. Defensive weapons included top, belly and tail ball turrets featuring electric drive and each armed with twin-barrel 20-mm Type 99-2 cannons. The nose turret featured a twin 13-mm Type 2 machine gun, and two machine guns of the same type were placed at the side windows. The G8N1 could carry up to four tons of ordnance or one Yokosuka MXY-7 Ohka-33 manned cruise missile. By July 1945 three additional prototypes had been produced, but one of them was destroyed by a bomb on the ground. Nakajima received an order for 48 aircraft but was unable to make full delivery because of constant bombing raids and a deficit of aluminum and alloy steel. And it was such a promising plane!
Owing to heavy losses of Ki-21 and Ki-49 bombers, the Army Staff asked Mitsubishi to speed up development of a new fast bomber that had been in the works since 1939. The apparent inability of naval aviation to defend New Guinea and Guadalcanal prompted the army leadership to issue a requirement for a dual-role aircraft that could both provide support to land troops and use torpedoes to destroy enemy invasion flotillas. The flight test program began on December 17, 1942 and at the end of 1943 16 preproduction aircraft were accepted for Army testing. Type 4 Army Heavy Bomber Hiryu (“Flying dragon”) Mitsubishi Ki-67 was the best Japanese medium bomber and in many respects far superior to its western counterparts. The aerodynamically pristine middle-wing monoplane with internal bomb carriage and effective self-defense weaponry (minimal «blind» zones, 20-mm Ho-5 cannon in the top ball turret, 12.7-mm Ho-103 machine guns in other gun stations) easily accelerated in diving to 600 km/hr and could make a loop with full 800-kg bomb load! The Army and the Navy finally agreed to joint flight crew training and joint use of the bomber fleet, and in April 1944 the first production Ki-67 bombers were equipped for torpedo attacks. The aircraft design was production-friendly but Japanese aviation industry made only 698 machines by the end of the war, since production was disrupted by the Tokyo earthquake in December and hampered by continuous American carpet bombing. The Ki-67 first showed its full capabilities in fighting over Taiwan in October 1944, earning allied respect and the code name «Peggy». During the Battle of Okinawa they fought jointly with G4M bombers, pounding the American land troops with bombs and attacking enemy ships with torpedoes.
Ki-67 was both a conventional bomber (top left) and a torpedo plane (left).
The Japanese are testing «Mitsubishi» Igo-1-A radio-command cruise missile (top).
The failure of the G5N bomber and delays in the G8N program caused the Naval Staff to mend relations with Mitsubishi and approve production of a new Model 34 G4M3 bomber, work on which had started back in 1943. The aircraft received a light single-spar wing with 12 integrated self-sealing fuel tanks inside and the same high-altitude Kasei-25 engines featured on the G4M2a. After flight tests in February and March 1944, it was decided to reinforce the wings, but at that time the Naval Staff issued additional requirements—installation of two more fuel tanks and modernized gun turrets, similar to those of the American B-17 and B-24. A series of additional changes followed, so that the first manufactured craft flew only at the end of October 1944, and until the end of the war only 60 G4M3s were made. By that time nearly all G4M2as and G4M3as were carrying the Type 3 ship detection radar with 50 km detection range - radar antennas were installed at the nose and along fuselage sides. This new equipment enabled the bombers to make torpedo attacks at night. The measures aimed at protecting the air crews and fuel tanks finally started to produce results - despite American air dominance, losses were no longer so catastrophic. American fighter pilots reported cases when a full complement of ammunition fired from a 12.7-mm Browning machine gun failed to bring down a “Betty” bomber.
G4M2e with attached MXY-7 «Ohka»-11 manned cruise missile,
maritime surveillance radar antennas are clearly visible,
spring 1945.
G4M1 aircraft on which the Japanese mission arrived to sign the capitulation, the Philippines, October 19, 1945. [8].
Inexperienced crews made Ki-67 and G4M aircraft much less effective than they could have been, and Imperial Japan turned to its last resort - kamikaze pilots. The Yokosuka MXY-7 Ohka-11 manned cruise missile was designed specifically for the G4M2e bomber. This kamikaze plane was equipped with solid boosters which accelerated it in terminal diving to 925 km/hr. It also carried a 1200-kg warhead. 755 Ohka-11 missiles were manufactured but the results of their deployment fell far short of expectations. Some of that number ended up on the ocean bottom together with the transport ships that carried them, and others simply fell into the sea because their pilots were so inexperienced. But the main problem was a stand-off distance much less than American radar detection range, which enabled American carrier-based fighters to shoot down the heavily overloaded carrier bombers with ease and at a considerable distance from their intended targets. On March 21, 1945 eighteen G4M2 bombers carrying fifteen Ohka-11 missiles accompanied by 30 «Zero» A6M5 fighters, launched an attack against the American air carrier force off Okinawa. Only three severely damaged fighters returned to base, as all the other Japanese aircraft were shot down by American deck fighters while still 100 km from their targets. The first successful Ohka-11 attack took place on April 1, 1945: the manned missiles damaged the battleship West Virginia and three transport ships. And the first American warship to be sunk by an Ohka-11 - the destroyer Able - went down on April 12. In the Battle of Okinawa, out of 185 Japanese G4M2e carrier bombers 118 were destroyed. Overall, the Japanese Air Force lost 2375 aircraft in fighting and another 1850 due to wear and tear. The United States lost 36 ships and vessels (another 368 were damaged) and 760 aircraft. By July 1945 massive American bombing raids against industrial facilities and air bases virtually destroyed the Japanese aircraft production industry together with the country's entire long-range bomber fleet.
Staryh Alexander Leonidovich, 2004, St. Petersburg
References:
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2. Kawanishi H8K1 ~ 3 Flying Boat//Japan: Koku~Fan, N 8, - 1975.- pp. 56-62
3. R. J. Francillon. Mitsubishi G3N “Nell” : Aircraft Profile # 160.- Profile Publ., UK
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10. M. Mayborn. Boeing B-29 Superfortress: Aircraft Profile # 101.- Profile Publ., UK
11. R. A. Freeman. Consolidated B-24J Liberator : Aircraft Profile # 19.- Profile Publ., UK, 1967
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14. Aeronautics Bureau's Navy Department report USA (NAVAER) «Standard performance of PBJ-1H aircraft», September 1, 1944, 6 pages, declassified//Naval Aviation News, - 1986, - 03-04.
