https://www.usni.org/magazines/proceedings/1948/march/yokosuka-naval-air-base-and-japanese-naval-aviation
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(1948 article about naval aviation history in Yokosuka)
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What is presently known as the Marine Air Base at Yokosuka, Japan, was the birthplace of Japanese Naval Aviation and came into being as an air station in 1911 when an English seaplane was brought to what was then known as Oppama Naval Air Base. Shortly afterward the plane complement of the base was increased to two seaplanes by the importation of one of the first Farman airplanes. Before the commissioning of the base as an air station, it had been a naval ship base for a little over twenty-five years.
The primary purpose of the base was to determine the usefulness of the airplane in military reconnaissance work. With this in mind, the Japanese had, two or three years prior to the opening of the air base, sent eight or ten naval officers to England to take flight instruction. These men formed the nucleus of what was to become in later years the “Wright Field” of Japan.
It might be interesting to note at this point that the first recorded “flight” in Japan took place in the late 1860’s when an unknown Japanese used a parachute-like affair to float from the top of a mountain to a village below. The local overlord, fearing that such an occurrence might lead to spying upon his castle, an act as taboo in those days as viewing the interior of the Emperor’s palace is today, played upon the superstitions of the ignorant villagers to such extent that they scalded the pioneer to death as a “devil.” For thirty or forty years thereafter, experimentation in aviation in Japan lapsed.
A revival of interest in flying was brought about by the Wright brothers’ flight at Kitty Hawk, N.C., in 1903. Shortly after Orville and Wilbur Wright startled the world with their epoch-making soar, Japan sent an emissary to the United States to study the Wrights’ methods of airplane construction. He returned to Japan a few months later and spent the next year in an almost vain effort at imitation of the Wrights’ plane. The model that this Japanese constructed made one flight at an exposition in Tokyo in 1905 during which it attained an altitude of four feet and a sustained flight of approximately five hundred yards. After several more years of experimentation, the Japanese became discouraged with their own efforts and in 1911 imported English and French models for their Army and Navy.
In 1912, satisfying themselves that the airplane would prove to be an invaluable reconnaissance component, they set up at Yokosuka Naval Air Base a section dedicated to the design and study of various types of aircraft. In 1913-14, one plane, the Yokosho (contraction of Yokosuka Naval Dock Yard) was designed and completed, and for the next five or six years various modifications of this first seaplane were used for research and training purposes. Nearly one hundred of this Jap-designed plane were built in this period.
However, in 1919 the Japanese again became dissatisfied with their aviation progress. After noting that most of the world was surpassing them in plane design, Japan once more turned to England for guidance, importing Avro planes of both land and sea types. At the same time English instructors were brought over to teach the Japanese fine points of flying these new types of planes. During this period, a landplane base was established at Kasumi-ga-ura—a base which later served the same function as a landplane base that Yokosuka did as a seaplane station.
Meanwhile, the Japanese commissioned the great Mitsubishi organization to manufacture fighter and torpedo planes, and in 1921 the first fighter, the Dyu Nen Shiki, was completed. Two years later, initial production was started on torpedo planes. Kasumi-ga-ura, blossoming forth as a full-fledged technical research laboratory for landplanes, was carrying on the same type of work for land-based fighters and bombers at this time, and in addition had become one of Japan’s major primary training schools. All pilots desiring to take advanced training on seaplanes at Yokosuka had first to complete their primary flight training at Kasumi-ga-ura.
Work in the Technical Research Section was continued at Yokosuka until 1931 when the division was transferred to a site about eight miles from the Naval Air Base. A year prior to the removal of the Research Section, the Technical Area Arsenal was established at Yokosuka for experimentation with various designs and types of new aircraft. To some extent, the development of new armaments was carried out here although the major portion of this work was done at the Technical Area Arsenal Branch, located about ten miles from the base.
However, one of Japan’s deadliest weapons—the Baka bomb which carried its own suicide pilot and was slung underneath a regular bomber—was the direct result of work at the main arsenal at Yokosuka Air Base. In addition to the development of the Baka bomb here, great strides had been made in the realm of jet and rocket propulsion. In fact, at the war’s end, not only had jet-propulsion planes undergone complete flight tests, but over three hundred of them had been produced and were ready to take their place on Japan’s warfronts.
Although the Yokosuka Naval Air Base was primarily developed as a seaplane base, flight training center, and research organization, it possesses several fine airstrips for land-based craft, the first of which strips was started in 1920 and completed in 1922. During the course of the war, these fields were used by several fighter and torpedo squadrons, based there as defense units.
Even considering the strides that Japan had made with various new types of armament and aircraft, in the opinion of one of the former high-ranking Japanese naval officers who had been stationed at Yokosuka she would have lost the war. For even without the advent of the atomic bomb, Japan’s supply lines were practically non-existent, and she was suffering from critical shortages of practically every major war material.
Also, according to this same Japanese source, the Air Base was attacked by our planes only twice—one a strafing foray and the other a bombing attack—and only minor damage was done. The former Japanese officer, now in charge of native labor at Yokosuka, expressed amazement that the American bombers had not attacked this important installation oftener. Possibly the explanation of this fact can be attributed to the nature of the work carried on there with the attendant desire that the base be spared for American intelligence purposes, if possible.
At the peak of its activities, the base’s complement exceeded 18,000 men and women. Of this number, 10,000 were employed in the factories and research laboratories maintained in the Technical Area Arsenal, the balance being aviation cadets and military personnel connected with the actual running of the base. In addition, there were also over three hundred pilots attached to the defense squadrons based there.
A year before the war’s end, the Japanese commanders, in anticipation of American bombing raids, started work on a tremendous number of caves and tunnels. Shortly before American Marine forces arrived to take over the Air Base, the majority of them were completed and over 7,000 men were living and working in them. Most of the caverns, with the exception of one huge underground hangar, were laboriously excavated by hand.
On September 7, 1945, Marine Air Group 31 along with elements of the Fourth Marine Regiment took over Yokosuka Naval Air Base, and intelligence officers immediately began an investigation of the Japanese work in the Technical Area Arsenal. Some startling facts were uncovered during the course of the search. The Japanese were not very far behind us in experimentation on rocket and jet propulsion. They were conducting experiments on powder-jet, liquid-propulsion, turbo-jet, and ram-rocket propulsion, and had several models under production.
The ram-rocket was of the simplest construction modeled after the German V-1, and would utilize almost any type of fuel. It was, however, a heavy fuel consumer, and was limited in its usefulness due to this fact. Various types of Japanese ram-rockets employed various combustibles as fuel—gasoline, diesel oil, and an oil extracted from the roots of pine trees. This pine-root oil could be refined to any required octane rating, and during the closing days of the war was used to considerable extent by the Japanese, as their facilities for obtaining petroleum products were rapidly on the wane.
The powder-jet model was used for flying bombs, some Kamikaze planes, and in some instances for auxiliary power on standard planes for quick getaways and take-offs. Because of the fuel problem involved, its use was limited to types of weapons and planes which required only short spurts of power.
According to Ryotaro Hikida, former commander of the Engineering Corps in the Technical Area Arsenal and a graduate of Tohoku Imperial University, the turbo-jet type of propulsion had been most successful from a Japanese standpoint, although at the close of hostilities experiments were being conducted utilizing hydrogen peroxide as a jet fuel. The major disadvantage of using peroxide as a fuel, he declared, was its “touchiness” and high explosive properties. The introduction of any foreign substance into the fuel system was likely to result in a tremendous blast. Several injuries resulted during the course of experiments run on hydrogen peroxide rockets. Hikida stated that if this fault could have been overcome an excellent propellant would have resulted producable at low cost.
Experiments being made on various types of jet-propulsion included a Jap-designed high-altitude engine employing liquid air as a fuel. Lack of liquid-oxygen manufacturing facilities, however, confined experimentation on this to a very small scale.
In the face of ever increasing metal shortages, the Japanese had designed and completed a plywood airplane which was to be utilized as a “hell-diver” or dive-bomber trainer. Research figures (Jap) indicated that this ship had undergone ground tests which showed it capable of withstanding 12.6 g pull-out, while it had actually been subjected to a 5 g strain in flight tests. Japanese technical men were amazed when told that with our new-type “zoot suits” our aviators could withstand almost double that figure.
One of the most amazing developments to come out of the Technical Area Arsenal was the automatic flap, which the Japanese claim to have pioneered. This new-type flap was so engineered that it would automatically lower to the required angle merely by the change in two variables—altitude (density of air) and acceleration—thus maintaining as closely as possible the proper correlation between load and drag. According to Japanese reports, this flap was in use on one of their single-engine fighters, and had proved highly successful in increasing the maneuverability of these planes in combat tactics.
There were also several different types of planes undergoing experimental tests in the Technical Area Arsenal. Among these were a twin turbo-jet plane designed for Kamikaze use; a pusher-fighter Ente-type (so-called after its German prototype) and a take-off on the Italian Campieni-type, with the engine installed in the fuselage about ten feet back of the nose, and employing a long drive-shaft to furnish driving power to the propeller.
As a result of the few bombings that Yokosuka Air Base underwent, most of the buildings on the station were in fairly good condition when the Marines took over, but little of the vaunted Japanese cleanliness and sanitation was found. Open sewers, great heaps of refuse, and filth of every kind were evident on every side, and it was only through great diligence and effort on the part of the Marines and Navy Medical Department that illness on the base was held to a minimum. It is interesting to note that according to the former Japanese executive officer of this base, the daily average of hospitalized Japanese was well over one hundred and fifty, while according to Colonel J. C. Munn, commanding Marine Air Group 31, there have never been more than twelve Marines confined to the sick bay and hospital at any one time.
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* Technical Sergeant Stokes was a journalist in Texas for thirteen years before entering the Marine Corps in July, 1943. After two years at Personnel Group Marine Corps Air Depot he served overseas with the Fleet Marine Force in Hawaii and with the Second Marine Aircraft Wing at Okinawa and Yokosuka. Leaving his civilian connections with radio stations, Sergeant Darling served in the Army in 1942 and then joined the Marine Corps as a combat radio correspondent in August, 1943, his final service as such being with the Second Marine Aircraft Wing at Yokosuka, Japan.
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