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IJN Hosho and her aircraft

By: Daniel H. Jones

Aviation in Japan began with the importing of several foreign designs for experimental purposes. Within ten years of its inception military aviation in Japan was well organized with the Army and Navy establishing separate air services and importing technical missions to help speed up progress. It was generally believed in Japan that the French were better equipped with land based aircraft while the British were more advanced in Naval air. Thus, the Army brought in a French technical mission, with some SPAD XIII aircraft, while the Navy requested British assistance. The British technical mission, called the Sempill Mission after its leader, arrived in Japan in September of 1921.

A group of 29 instructors under Capt. Sempill began training operations at the Navy's first air base at Kasumigaura. Several new aircraft types, including the Gloster Sparrowhawk, were introduced and for over a year intensive training was carried out in flight control, torpedo bombing, squadron tactics and in numerous technical courses. The influence of this mission was profound and contributed to rapid progress in organizational and operational efficiency. They also were of assistance to the ship designers as they brought with them plans of the latest British aircraft carriers, ARGUS and HERMES. These were state of the art at the time. ARGUS was the first flush deck carrier and HERMES was the first aircraft carrier to be designed as such rather than being converted from another hull. These plans had an influence on the design of the first Japanese carrier HOSHO.

The aircraft manufacturing companies were created to support the expansion of military aviation. They began by manufacturing foreign designs under licensing arrangements in order to gain experience. However, it was realized that this was not the long term answer and Mitsubishi, Kawanishi, and Nakajima, (the three largest), each sought design assistance from established companies in Europe. Mitsubishi approached Junkers and Rohrbach in Germanv and invited Mr. Herbert Smith of Sopwith to come to Japan to design aircraft. Smith arrived in 1921 and was given the assignment of designing three new carrier based aircraft to equip the nearly complete carrier HOSHO. When HOSHO was commissioned in 1922 she became the first carrier completed to be designed for the role. Although HMS HERMES was designed first, construction proceeded at a leisurely pace and the HOSHO entered service before her.

The three aircraft types designed by Smith were, the 1MF, a single seat fighter, the 2MR, a two seat reconnaissance type, and the 1MT, a triplane torpedo bomber. The first two were quite successful and were both produced in quantity. The triplane proved to be too large and heavy for carrier operations, particularly if operating from such a small ship as the HOSHO. Only 20 were built before production was halted. Mitsubishi was instructed to design another aircraft to replace the 1MT and Herbert Smith created a more stable biplane replacement, the 2MT, using the same Napier Lion engine that had powered the triplane. This proved an immediate success.

The lMF, Type 10 fighter, was powered by a Hispano engine and 138, (in several versions), were produced to form the first carrier fighter squadrons of the Imperial Navy. The 2MR was an enlarged 2 seat version of the same basic design, also powered by the Hispano engine and designated Type 10 Carrier Based Recoimaissance. In all versions, 159 were built and after years of naval operations many were used in civil service. The first versions of both designs used a car type radiator while later versions had a more pointed nose with Lamblin Radiators mounted on the fuselage sides or underneath.

The 2MT entered service in 1925 with the designation of Type 13 Torpedo Bomber. This was the longest lived of the three designs, remaining in production in continuously improved forms until 1933. A total of 442 of them, in all versions, were built.

Photographs of HOSHO with aircraft on deck or in the air seem to show only the Type 10 fighters. Drawings are provided of the variants of the Type 10 1MF, Type 10 2MR, Type 10 1MT, and the type 13 2MT for scratch building the missing types. It is almost certain that the other standard aircraft types would have been operated, at least experimentally, from the HOSHO.

The new Fujimi kit of the HOSHO depicts the ship as in 1922-23. For this time period only the Type 10 fighter, (1MF1 or 1MF2), and Type 10 reconnaissance, (2MR1) would have been in service. Adding any of the other aircraft types would require some modifications to the ship.

The carrier HOSHO underwent many changes during her career. The starboard mounted bridge structure was removed in 1923 and she became a flush deck carrier. This carrier style, totally flush deck with no bridge, was to be repeated many times in the Imperial Navy. The bridge was discarded because pilots found it interfered with their vision and it was too small for the officers to effectively command flight operations. Side gallery platforms were added for directing operations. This new arrangement was well liked by both pilots and deck officers. A radio mast was mounted on the gallery on the starboard side after the bridge structure was removed. Later this was replaced with a larger one, then removed altogether.

The landing system originally installed was the British WWI system, or "the Trap", consisting of a combination of longitudinal wires and the more familiar across deck arrester cables. On early British carriers, such as HERMES, the area where the wires were strung was actually sunk slightly below the remaining deck level. Aircraft coming aboard would drop into this depressed area, hooks on the undercarriage would engage the longitudinal wires, while the tail hook would engage the across deck wires. The idea of the longitudinal system was to keep the aircraft traveling in a straight line while the aft tailhook brought it to a stop. What more often happened in practice was that the landing gear hooks caused the aircraft to nose over on landing. Many early carrier pilots were missing their front teeth, considered an occupational hazard, from nose overs and sudden contact with the forward cockpit coaming or protruding machine gun butts. Experiments soon showed that the "trap" was unnecessary and in both the IJN and American Navy, (on the USS LANGLEY), this system was removed and replaced with a simpler system of across deck arrester cables. The British, perhaps because they invented it, hung on to the older system for a much longer time.

The three funnels were originally designed to hinge and to fold down to a horizontal position during flight operations, a feature shared with the USS LANGLEY. Sometime in the late twenties, the funnels were permanently fixed in the horizontal position. With the elimination of the folding feature, the deck was extended over the funnels; gaining several feet in width. The forward portion of the flight deck sloped downward when the ship was first completed. Later this portion of the flight deck was raised almost to the horizontal with only a very slight downward angie remaining. As aircraft size and speed increased, HOSHO was becoming too small for safe flight operations. About 1944 the deck was extended both forward and aft to allow her to be able to operate higher performance aircraft.

Numerous detail changes also occurred. Boat arrangements were modified and the positions changed. When built, HOSHO was armed with four 5.5" guns and two 3" anti-aircraft guns. At the outbreak of the War with America the 3" guns were removed and were replaced with four twin 25mm gun mounts. Sometime during the war, the 5.5" guns disappeared and the 25MM guns were increased to ten triple 25MM mounts. Near the end of the war, after HOSHO was damaged by bombing, the 25mm guns were reduced to two triple mounts and she was thus armed when surrendered at Kure in 1945.

HOSHO served in the combined fleet from 1922 to 1933 when she was withdrawn and used for training duties. During the 1938-39 period HOSHO received a full air complement, (of obsolete types), and was employed again with the Combined Fleet and saw action in the China War. In 1940 she again reverted to the training role and remained so employed until after the Pearl Harbor attack. Shortly thereafter HOSHO was reequipped with modern aircraft, (exact numbers and types not known for certain), and was assigned to the 3rd. Carrier Division along with the RYUJO. After a few minor operations she took part in the Battle of Midway as part of the main fleet. She then returned to home waters and was reassigned to the training role for the duration of the war. This second line employment is probably what saved her, for she was usually operated away from the main fleet anchorages and was overlooked in the wide ranging air sweeps by US Navy aircraft towards the end of the war. At war's end she was still afloat although she had sustained some bombing damage in 1945. HOSHO was used after the war to repatriate Japanese soldiers and civilians from the many outlying island garrisons which had becn bypassed in the American drive across the Pacific. She served in this duty until 1947 when she went to the scrapper's torch. Thus HOSHO was both the first and the last Japanese carrier.

1/700 Scale Drawings

IJN Hosho 1922
IJN Hosho 1924
IJN Hosho's aircraft 1924

IJN Hosho 1936
IJN Hosho 1945

This article originally appeared in Plastic Ship Modeler 1995/2 and is reprinted here with the permission of the author and editor.

Copyright © SMML 2003