Nakajima Experimental Attack-Bomber "SHINZAN"

Illustrated by Shigeo Koike.

There were some early attempts to produce a long range bomber -  for example, the Mitsubishi G7M1 Taizan  (a  16-shi  project)  - plus  designs  that  were  actually  built  such  as the  Nakajima  G5N Shinzan  and  Nakajima G8N  Renzan. The Shinzan was not a success and the Renzan failed to reach operational service as a combat aircraft, let alone reach America and return.

The DC-4E was sold by Douglas to Japan's Mitsui Trading Company, Ltd. for Japan Air Lines Company, Ltd.; no more are built. The Japanese pay $950,000 for the airplane, which is shipped to Tokyo by sea on September 29. After it is reassembled by Douglas technicians, the Super Mainliner will be the model for that nation's first four-engine land plane, the unsuccessful Nakajima G5N bomber/transport Shinzan (Mountain Recess).

The design that emerged from this study was for an all-metal mid-wing monoplane with fabric-covered control surfaces and powered by four 1,870 hp Nakajima NK7A Mamori 11 air-cooled radial engines driving four-bladed propellers. Notable features included a long ventral bomb-bay, glazed nose and twin tailfins replacing the DC-4E's distinctive triple rudder. The DC-4E's retractable tricycle undercarriage was retained, as well as the original wing form and powerplant arrangement. Defensive armament comprised one 20mm Type 99 Model 1 cannon each in a power-operated dorsal and tail turret plus single-mount hand-operated 7.7mm Type 92 machine guns in the nose, ventral and waist positions.

The first prototype G5N1 made its maiden flight on 14:35 8 April 1941. Overall performance proved disappointingly poor however, due to a combination of excessive weight, the unreliability of the Mamori engines and the complexity of the design. Only three more prototypes were completed. In an attempt to salvage the project, two additional airframes were fitted with 1,530 hp Mitsubishi MK4B 12 "Kasei" engines and redesignated G5N2s. Although the Mitsubishi engines were more reliable than the original Mamori 11s, the aircraft was now even more hopelessly underpowered and further development of the type was halted.

Of the six completed Shinzans, four of them were relegated for use as long-range Navy transports under the designation G5N2-L Shinzan-Kai Transport. The Allies allocated the code-name "Liz" to the aircraft, in the expectation it would be used as a bomber.

Z Superbombers Project (1942-1944)

Similar to the Nazi ‘Amerika-Bomber’ project to develop long-range strategic bomber to strike the United States from Germany, Japan initiated the ‘Project Z’ to develop an intercontinental bomber to strike North America. The Japanese were desperate to develop something like the US B-29 Superfortress long-range heavy bomber which was introduced in 1944.

Imperial Japanese Navy had designed the four-engined ‘Nakajima G5N’ heavy bomber prior to the Second World War and introduced it in 1941. But their planners wanted something much larger, faster, heavier and capable of flying at 32,800 feet with a load of 22 one thousand pound bombs; B-29 Superfortress also had similar capabilities with a speed up to 350 mph during wartime. Imperial Japanese Army was presented several designs for the Project Z; these included- the Nakajima G10N Fugaku and Kawasaki Ki-91. Fugaku means Mount Fuji. G10N Fugaku was supposed to have a wingspan of 213 ft 2 in and a total length of 147 ft 7in. It would have been powered by six 5,000 hp engines and capable of reaching speeds of 365 mph at 25,000 ft. Nakajima Aircraft Company started developing G10N’s 4 row 36 cylinder 5,000 hp engines in 1943 but abandoned due to complexity. Z Superbombers Project was cancelled in July 1944.

China Expedition

While they had been manufacturing Western designs under license in the 1920s, Japanese aircraft builders had been catching up on the fine points of aeronautical design. In the early 1930s, they were ready to proceed with designs of their own.

In February 1934, Imperial Navy air headquarters issued a 9-shi specification calling for a new single-seat fighter. Although carrier-based capability was virtually implicit in a navy requirement, one of its chief architects, Lt. Cmdr. Hideo Sawai, had deliberately avoided specific reference to such characteristics, concerned that it would inhibit the designers. In contrast to British and American naval aviation planners, Sawai wanted the manufacturers to produce a high-performance fighter that would bring Japan up to world standard—the matter of adapting and equipping it for operations from carrier decks would be dealt with afterward. The specification called for a maximum speed of 350 kilometers per hour (217 miles per hour) at 3,000 meters (9,840 feet) and the ability to climb to 5,000 meters (16,405 feet) within 6.5 minutes. Armament was to consist of two 7.7mm machine guns, wingspan would not exceed 11 meters (36 feet), and length no more than 8 meters (26 1/2 feet).

Among those who sought to meet the requirement was Mitsubishi’s chief designer, Jiro Horikoshi. After giving cursory consideration to other configurations, Horikoshi determined that the fighter must be a low-wing monoplane, with attention paid to the cleanest possible aerodynamics and to the minimum possible weight. The airframe he designed used stressed-skin aluminum over a two-spar box-type wing structure of inverted gull form, which was later altered into a flat center section with dihedral for the outer wing panels. After considering the possibility of incorporating retractable landing gear into his design, Horikoshi rejected it on the grounds that the 10 percent decrease in drag would result in only a 3 percent increase in speed, not enough to justify the system’s greater weight and complexity. Instead, his monoplane would have fixed undercarriage, with streamlined fairings over the wheels.

The first Ka-14 prototype, powered by a 550-horsepower Nakajima Kotobuki 5 nine-cylinder radial engine, was completed in January 1935, just eleven months after Mitsubishi received the 9-shi specification. During its first flight tests in February, it reached a speed of 444 kilometers per hour (276 miles per hour) at 10,500 feet, exceeding both the navy’s requirement and Horikoshi’s own expectations. Nevertheless, the Ka-14 had a great obstacle to overcome when it competed with the Nakajima A4N1 biplane in the autumn of 1935, because of the almost insurmountable prejudice in favor of dogfighting capabilities over all others among senior JNAF officers. The Ka-14’s low wing loading made it extremely maneuverable for a monoplane, but it still could not match the maneuverability of the A4N1—until the rules of mock combat were altered to include climb and dive tactics. That change gave the Ka-14 such an overall edge that even Minoru Genda, one of the most ardent biplane partisans, was won over to the new type.

After further development—and an unsuccessful attempt to interest the army in the design—Mitsubishi was able to put its monoplane into production as the A5M1 Model 96 carrier fighter in the autumn of 1936. An improved version with a 610-horsepower Kotobuki 2 KAI 3ko engine, a longer chord cowling, and a three-blade propeller in place of the two-blade airscrew entered production in the late spring of 1937 as the A5M2-ko. The outbreak of war with China on July 7, 1937, lent urgency to the JNAF’s efforts to hasten the A5M to operational units, and the newly formed 13th Kokutai (Air Group) got its first monoplanes just four days later.

“Battle of Shanghai”

Initially, the Japanese army advanced quickly, taking Beijing and Tientsin; but resistance stiffened as it approached Shanghai, and at the same time Japan’s regular arsenal of biplanes was proving unable to achieve a decisive degree of air superiority over the mixed bag of Chinese aircraft that opposed them. The need for such an edge became critical on August 14, when nine Mitsubishi G3M2s of the Kanoya Kokutai, led by Lt. Cmdr. Shinichi Nitta, left Matsuyama (Sung Shan) air base near Taipei, Taiwan, crossed the Formosa Strait and tried to bomb Jienqiao training field near Hangzhou, while another nine G3Ms led by Lt. Cmdr. Nantaro Asano attacked Guangde airfield. Chinese intelligence had learned of the coming mission and Colonel Kao Zihang, commander of the 4th Pursuit Group at Zhoujiakao, had ordered his 21st, 22nd, and 23rd Squadrons to Jienqiao, where their Curtiss Hawks would refuel and take off to intercept the raiders.

Kao’s fighters were the last of a long line of classic biplanes that had begun in 1925 with the P-1 Hawk (the first Curtiss to bear the name), and which culminated in the F11C-2 Goshawk. Final refinements in the Goshawk were metal wings and hand-cranked retractable landing gear on the XF11C-3, inspired by that of the Grumman XFF-1 two-seat fighter. Entering US Navy service in May 1933, the F11C-3—later redesignated as the BF2C-1 fighter-bomber—joined the Grumman F3F and Polikarpov I-153 as the only single-seat biplane fighters with retractable undercarriage to achieve quantity production.

Export versions of both Goshawk variants reverted to wooden wing structures, the fixed-gear plane being called the Hawk II and the retractable model the Hawk III. Powered by a 740-horsepower Wright R-1820-F53 radial engine, the Hawk III had a top speed of 240 miles per hour, mounted two .30-caliber Browning machine guns, and served in the air arms of Thailand and Argentina as well as China, which imported its first twelve in March 1936. Another ninety arrived in crates and were assembled at the Central Manufacturing Company at Hangzhou. The Chinese had seventy-two operational when the Japanese invaded, as well as fifty Hawk IIs.

August 14 began with Chinese air attacks against the Japanese army in Shanghai and against supporting naval units offshore, including Hawks of the 5th Pursuit Group carrying one 250-kilogram bomb each. Lieutenant Liang Hongwen in plane No. 2401 of the 24th Pursuit Squadron was credited with hitting the stern of the Japanese light cruiser Idzumo off Nantong, but it turned out to be a near miss—which was fortunate, since his target was in fact the British heavy cruiser Cumberland. Two other Chinese bombs fell near the American heavy cruiser Augusta. Another “international incident” occurred that afternoon when three Hawks from the 24th attacked the Japanese-occupied Kungda Textile Factory, but one of their bombs fell on the Nanking Road in the International Settlement. Meanwhile, Liang came under attack by an aggressively flown Nakajima E8N1 floatplane from the light cruiser Sendai, and was so badly shot about that he had to force land and died of his injuries soon after. Next, five Hawk IIs and nine Hawk IIIs made another attempt to bomb the Kungda factory, and some also attacked the floatplane, scoring fifteen hits before it lost them in a cloud.

Poor though the Chinese bombing performance was, it spurred Vice Adm. Kiyoshi Hasegawa, commander of the Japanese Third Fleet, to order attacks against their airfields. Due to typhoon weather conditions, however, the only unit game to defy them was the Kanoya Kokutai with its modern G3Ms—all-metal twin-engine monoplanes capable of 232 miles per hour and of mounting three 7.7mm machine guns. They took off at 1305 hours Formosa time, but storm clouds and poor visibility limited their altitude to 1,641 feet. They would also have to carry out their mission without fighter escort, but the Japanese were not overly concerned, arrogantly assuming that they would not need it against the inept Chinese.

The 4th Group’s Hawk IIIs were still in the process of refueling at Jienqiao when Nitto’s bombers arrived, strung out due to the weather, which made it hazardous to fly in formation. Kao, boarding his personal Hawk III marked IV-I, ordered all fighters to scramble up, ready or not. This had grave consequences for two of them—Hawk III 2105 of the 21st Pursuit Squadron ran out of fuel and crashed, mortally injuring Lt. Liu Shufan, and 2106 force landed, injuring Lt. Chin Anyi. The rest laid into the Japanese, and Colonel Kao, after silencing two gunners, closed to twenty meters to shoot a G3M, piloted by Petty Officer 3rd Class Iyoshio Momosaki, down in flames over Banshan. He then attacked Warrant Officer Fujio Yamashita’s bomber, crippling its left engine with fourteen hits, along with twenty-one in its right wing, and thirty-eight to the fuselage before his fuel gave out, compelling him to disengage and force land at Jienqiao. A third G3M, piloted by Petty Officer 1st Class Yanase Mitsui, and which was swarmed by 21st Squadron Hawk IIIs flown by Capt. Lee Guitan, Lt. Wang Wenhua, and Liu Chisheng, went down near Chiaosi.

At 1800 hours Asano’s nine G3Ms arrived over Guangde in V formation but only scored one bomb hit. As they made for home, they encountered Capt. Chow Tingfong, commander of the 34th Provisional Pursuit Squadron, who had been test-flying a Hawk III. Although he had no ammunition, Chow attacked and managed to break up the formation. As the Japanese flew on, they ran into the 22nd Pursuit Squadron, and one of its pilots, Lt. Cheng Hsiaoyu, hit the right engine and wing tank of Warrant Officer Hitoshi Ogawa’s G3M. Ogawa pressed on for Taiwan but ran out of fuel short of his goal and ditched near the Keelung harbor lighthouse, where he and his crew were rescued. Yamashita managed to get his riddled bomber back to Matsuyama on one engine, but its landing gear collapsed on landing, and it was written off.

Though overlooked in the West, the “Battle of Shanghai” had multiple significances in aviation annals. In 1940 the Republic of China pronounced August 14 as “Air Force Day.” Indeed, Colonel Kao had scored his air arm’s first aerial victories. To his shared kill that day, Liu Chisheng would add ten more flying Hawks, I-16s, and I-152s, to become China’s ace of aces and a major general in the Republic of China Air Force. In terms of air strategy, the Chinese fighters’ success struck a serious blow to Italian general Giulio Douhet’s widely accepted theory that bombers alone could win wars. Conversely, the Japanese were rudely awakened to the folly of sending their bombers in unescorted, and to the critical need for a fighter capable of seizing control of the sky.

Land-based Japanese navy units, augmented by the air groups of the light carrier Hosho off Shanghai, were joined on August 15 by the large carrier Kaga, and both vessels achieved a marginal degree of local air superiority with their aging Nakajima A2N1 fighters.