Technical Manual, U.S. War Department, October 1, 1944
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Chapter IV: Japanese Air Service
Section V: Equipment
1. GENERAL. a. Aircraft. (1) Basic design principles. Japanese aircraft have been built largely for the purpose of attaining great maneuverability, thereby sacrificing protection, firepower, and sturdiness. However, armor plate now is found on an increasing number of aircraft, as is also light leak-proofing for the fuel tanks. These belated attempts to provide more protection for their aircraft may mean that the Japanese are becoming aware of the importance of crew protection.
(2) New developments. A few recent improvements have been noted in Japanese aircraft, and further innovations may be expected. Greater attention to streamlining, and the use of larger, more powerful, and differently designed engines appear to be the two outstanding lines of development. The streamlining of the cockpit of type 99 Dive Bomber VAL Mk 2, and the use for the first time in a modern Japanese fighter of a liquid-cooled, inline engine in type 3 Fighter TONY are examples of these trends. The standard fighter armament is two 7.7-mm and two 20-mm guns; however, a 37-mm gun has been found on the twin-engine fighter NICK.
2. ARMAMENT. a. General. The Japanese show very little originality in their aircraft armament, except in modifying foreign designs, such as those of Great Britain, United States, Switzerland, and Germany. The only weapon that might be called truly Japanese is the Model 89, Nambu type, magazine-fed, aircraft machine gun which was converted from the Nambu ground machine gun. However, even this is a modified Hotchkiss design. It appears that a great variety of noninterchangeable types of ammunition exist for aircraft guns of the same caliber.
b. Guns. The Japanese employ aircraft guns with calibers ranging from 7.7-mm to 37-mm. Details of each type are shown in figure 67.
3. OTHER EQUIPMENT. a. Radio. See chapter 10.
b. Oxygen apparatus. (1) The designs of Japanese oxygen systems and their parts are good, although the basic principles used are not considered the best. The high pressure system has been generally disregarded in favor of a low pressure one, in view of the vulnerability of the former. The Japanese system usually consists of the following parts; high pressure oxygen bottle, pressure reducing regulator, pressure gauges, automatic regulator, and masks or tubes.
(2) There are two types of bottles. The first is a forged cylinder; the second a drawn and welded bottle. Neither of these containers has been found with protective measures, such as armor or wire wrappings, to prevent shattering.
(3) There is an automatic regulator of good design. The flow of oxygen is shut off until 10,000 feet is reached, at which altitude an aneroid lifts the metering needle allowing oxygen to pass through the outlet.
(4) On a few Japanese operational aircraft, an emergency chemical oxygen generator has been found.
c. Navigation equipment. (1) The Japanese seem to have good navigation equipment, for the few navigational instruments that have been captured in good condition have been of simple but effective design, indicating much copying from other countries. An octant taken from a Japanese reconnaissance airplane was found to be fairly accurate, easy to use, and painstakingly manufactured. A navigation calculator, consisting of a simple, but neatly made, celluloid disc is used.
(2) A Japanese drift sight operating on a bubble gimbal system was found easy to use, for it reduces the effect of roll and pitch. The optical system is arranged so that the apparent motion of the image of the bubble is in the same direction as the motion of the sight. The treatment of various parts of the sight to prevent corrosion is of good quality. The compasses that have been examined are of conventional design, and their workmanship is good as a general rule. An automatic pilot that was examined was found to be so similar to a type manufactured in the United States that parts in some instances were interchangeable. The case and some of the internal parts were heavier than that used by United States manufacturers, but the workmanship was good.
d. Instruments. Japanese instruments on the whole are more or less copies of instruments used in this country several years ago. Mass production methods were used on some of them, while on others, much hand finishing was in evidence. A more or less conventional design was followed in the case of engine instruments, about the only deviation being in the manifold pressure gauge which had new type of markings on its face. Boost pressure was shown in red on the right-hand side of the dial, and negative pressure in black on the left-hand side: zero mark, or atmospheric pressure, was the dividing line between the two colors.
e. Night-fighting equipment. Night-flying equipment on the aircraft examined to date shows very little improvement over that used in the United States Air Force several years ago. No individually lighted instruments, except the pilot's compass, have been found. Cockpits are lighted by small dashboard type lamps: some of the lamps are controlled by rheostats, while others have no control at all, but simply are turned on by a toggle type switch. Recent night fighter activities of the Japanese in the South Pacific area have shown an improvement in effectiveness which may indicate an advancement in technical aspects of their equipment as well as improved tactics.
f. Parachutes. (1) The Japanese use a quickly attachable seat type parachute for their bomber and transport crews. Another seat type parachute is used by pilots of fighters and other smaller aircraft. There have been reports that the Japanese use a chest type chute, but to date no information is available in regard to the type of aircraft with which it is used. The construction is of circular type. Four red-colored lines, attached to four of the main risers extending inside the canopy to the apex (top vent), are used for "spilling" the chute.
(2) The material in the canopy and shrouds is a good quality silk, and harness and pack are made of an equally good quality cotton. Although the harness is finely woven, it is not as strong as those manufactured in the United States. In general, except for the advantageous four red shrouds mentioned above, this type parachute is inferior to those made in the United States. As for the chest type parachute, there is not an adequate amount of data available to date, except that the Japanese silk webbing of the harness is much less bulky than American cotton but not as strong.
g. Photographic equipment. To date very little is known about the advanced designs of Japanese photographic equipment. All of it in good enough condition to test has been copied from equipment manufactured in the United States several years ago. Only a few minor changes had been made, namely, the handle grip sight and in the film magazine. Workmanship on the camera was excellent and indicated adherence to conventional practice. On a later-model camera that was recovered, the cone and part of the body were made of heavy cardboard. This specimen may have been an experimental camera, for no other models have been found. The film used had a nitrate base, and the emulsion was a little slower than that used by United States forces.
h. Flotation gear. Flotation gear has been found in some of the Zekes and Hamps; in both types of planes it was placed in the rear of the fuselage. This equipment consists of a rubberized cloth bag which is held in place by 8 pieces of woven cotton reinforcing tape attached to each corner. The gear is inflated by a CO2 cylinder which is located behind the pilot's seat. Evidence of flotation gear in dive and torpedo bombers shows that it is installed in the top of the wings near the fuselage. This type air equipment is used mostly in training and on routine flights.
i. Fuel tank protection. There are three main types of Japanese fuel tank protection. The first, and least effective, is called "leak absorbing;" it consists of four layers of natural rubber joined together and totaling 3.1-mm (1/8 in.) in thickness. This is covered by a kapok matting which in turn is covered by a silvered fabric resembling balloon silk. The second type, termed "leak-proofing," is 12-mm (0.47 in.) thick. It is composed mostly of heavy crude rubber in 2 layers. The third type, referred to as "self-sealing," is 28.6-mm (1 1/8 in.) thick; it is made up of 6 rubber layers reinforced by an inner silken mesh and an outer galvanized iron mesh. The self-sealing properties of this type appear to be good, at least on the outer surface. A jettisonable fuel tank made of wood has been examined, the length of which is 5 feet 2 inches, the diameter 15 1/4 inches, and the capacity approximately 35 United States gallons. The construction is of plywood panels 7/64 inch thick.
j. Fuels and lubricants. From the samples of fuels and lubricants that have been obtained, it has been found that the Japanese fuels are good, although some contain a rather high amount of aromatics. The lubricants tested, although similar to those used in the United States, do not have some of the cold properties of the latter. Samples of greases in wheels and propellers also were found to be similar to American products.
k. Bombsights. Examination of a damaged bombsight revealed that it operated on the same principle as the French bombsights manufactured at the beginning of the present war. Stabilization of this sight is obtained by means of a level bubble in the optical field which is maintained in a stabilized position by hand. This sight worked on a timing principle and did not have electric bomb release. Another bombsight used by the Japanese was essentially a 3 1/2-foot telescope with no stabilizing or levelling aids. The eyepiece had no adjustment, but the sight incorporated range rate correction, deflection rate correction, and focusing.
l. Bombs and torpedoes. (1) Japanese bombs in general are made of steel and usually are not streamlined. Except for the armor-piercing and semi-armor-piercing bombs, they are of three-piece construction, consisting of nose, body, and tail. The nose and tail units are screwed in, welded, spot welded (the point of welding is the weakest part of the bomb), or riveted to the body of the bomb. The tail cones of some general-purpose bombs are filled with explosives; in these bombs, the body and tail units are filled in separate operations and subsequently attached. Either nose and/or tail fuses are used which are all mechanically operated. Long delay fuses, operated by a solvent dissolving a celluloid screw, also have been employed, while others are operated by a slight pyrotechnic delay.
(2) Some of the more common type bombs are the antipersonnel bombs ranging from 1 to 15 kilograms (2.2 to 33 pounds); incendiaries from 1 to 250 kilograms (2.2 to 550 pounds); and high explosives from 50 to 800 kilograms (110 to 1760 pounds). A gas bomb of 50 kilograms (110 pounds) also has been employed. For night tactics there is a 33 kilogram (72.6 pounds) illuminating flare.
(3) The Japanese make use of 5 types of torpedoes which differ in weight, length, diameter, speed, and explosive charge. Most standard models measure 17 feet long with a diameter of 17.7 inches. These torpedoes weigh 1,800 pounds and have an approximate speed of 42 knots. There exists one model which weighs 3,245 pounds, and is 22 feet long, with a diameter of 21 inches and a speed of 45 knots.
m. Sea rescue equipment. A limited amount of Japanese sea rescue equipment has been made available for examination. A 5-man, pneumatic, rubber life raft, measuring 12 feet long by 3 feet 10 inches wide, was found to be below current standards. The principal fault was the fact that the floor consists of meshed tarred cord which does not protect the occupants from the effects of salt water. As to sea rescue equipment for one man, a kapok life belt was examined and found to be identical with the Navy kapok jacket. A horseshoe-shaped, pneumatically inflated life preserver also is known to be used by the Japanese. This preserver, of single-ply construction, is weaker, but considerably lighter, than any equivalent preserver made in the United States. It has a good rubber coating, but is not designed to fit the individual. The ropes attached to the side indicate that the user hangs on to the preserver instead of wearing it.
n. Clothing. (1) The Japanese Air Force receives a good grade of clothing. Their flying suits, made of good silk and cotton, are well tailored and are similar in design to flying suits used by the United States Army Air Forces. All items of flight clothing recovered were sewed by skilled operators on standard machines, and the materials had received water- and flame-proofing treatment.
(2) The Japanese also have an efficient, electrically heated flying suit, which, when worn as an outer garment, compares favorably with United States electric suits. This suit, when tested, showed no hot spot when worn as an outer suit, but it did heat up too much around the shoulders when worn under other clothes. It also had cold spots on the back of the legs and on the inside of the arms. The fabric used is chocolate colored, and is of good quality.
4. CHARACTERISTICS OF OPERATIONAL JAPANESE AIRCRAFT. a. Markings. Japanese aircraft markings usually consist of a large red disc on the top and bottom of the outer section of each wing and on each side of the fuselage. The side marking is omitted on Army aircraft, but is retained on Navy aircraft. Occasionally the red disc is surrounded by a narrow white line. On biplanes wing markings appear only on the top of the upper wing and the bottom of the lower wing.
b. Designation of types. Tables in this chapter present the main characteristics of operational Japanese aircraft. It will be noted that both a type number and an identification or code name are given for each airplane. Under the Japanese system of airplane designation, the type number indicates the year in which the aircraft was adopted. Type 97 corresponds to the Japanese year 2597 (our year 1937) and type 0 (Zero) to 2600 (our year 1940). For this reason, various categories of aircraft—fighters, bombers, reconnaissance, and others—all may be designated, for example, as Type 0.
c. Identification or code names. In order to eliminate the confusion regarding the designations of Japanese aircraft, a code name was assigned each airplane by the Allied Air Forces in the Southwest Pacific in September 1942. The fighters and floatplanes were given masculine names, such as Zeke and Pete, whereas the bombers, land-based reconnaissance, and flying boats were given feminine names, such as Betty, Dinah, and Emily. Transports were assigned names beginning with the letter "T." When the existence of a new type is confirmed, a new code name is assigned to the aircraft.
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