Japanese Fighter Design

by Martin Caidin

Although the Mitsubishi S-001 has been generally accepted as the well-known Japanese Zero, there are actually more than eight fighter types of the Japanese Army and Navy Air Forces in service at the present time. The Mitsubishi fighters, manufactured by the Mitsubishi Jukogyo Kabushiki Kaisha (Mitsubishi Heavy Industries, Ltd), have appeared more frequently than the other types.

The Mitsubishi firm manufactures the S-001 Zeke, S-002 Hamp, and the SHS-00 float-type Zero fighter for the Naval Air Forces, and the S-001 Zeke, S-002 Hamp, S-003 Tony, and the now obsolete S-97 for the Army. Other Naval types include the Nakajima SKT-97 float-type two-seat observation-fighter model commonly mistaken for the Mitsubishi Zero, the Nagoya S-00 and S-001, Sento Ki 00 and 001. The Sasebo KT-00 float-type reconnaissance seaplane, often confused with the SKT-97, is now out of service. These two-seat float-plane aircraft were extremely useful for operations under the grueling and often poor flying conditions experienced in the Aleutian and Kurile Island areas, but proved extremely vulnerable to American fighters. The less frequently encountered Nakajima Army S-01 and the new Tojo fighter complete the list of Army fighters.

Close cooperation between the Nagoya, Kawasaki, Sasebo, Mitsubishi Jukogyo Kabushiki Kaisha, and Nakajima Hikoki Kabushiki Kaisha aircraft firms has resulted in Zeros of unidentical recognition characteristics and altered performances. The Mitsubishi Hamp is identical to its predecessor the Zeke, except for clipped wings resulting in a smaller wing-span, more powerful armament and power plant, and generally improved performance. The Type III Tony is the first inline-engine-type Japanese fighter to be encountered by American forces in the Pacific, and is a direct contrast to the typical Japanese fighter design. The Army and Navy Mitsubishi Zeke and Hamp fighters are identical, but for addition of carrier arrester gear on the Navy models, hinged wingtips of the Navy fighter.

The Mitsubishi Navy SHS-00 float-plane Zero fighter is a development of the standard versions with a single pontoon and wing-floats. This reduces the performance considerably, cuts the speed by as much as 60 mph.

More confusion has been caused by the Nagoya and the strangely erroneous Sento Ki Navy fighters than other Zero types, as the S in Japanese fighter designations stands for Sentoki, or fighter. The only plausible explanation for this puzzling fact is that the original design was approved by the Japanese warlords, contracts awarded to several aircraft firms in various cities of Japan with the Sento Ki designation chosen for simplicity. The Nagoya S-00 and S-001 are almost exactly identical to the Sento Ki fighter, and each design may have been submitted by the Nagoya Aircraft Firm or the Mitsubishi firm located at Nagoya.

The Nakajima Army S-01 has been reported to be the fastest Jap fighter yet encountered, with the exception of the Tojo, on which little information is available. British sources credit the Nakajima with a maximum speed of 387 mph, incredibly fast for a fighter of 1,050 hp. These fighters are being produced at the Ohta and Gumma-Ken plants of the Nakajima firm. A light armament of only two 12.7-mm (50-cal) guns is carried, and the power plant is the 1,050-hp Mitsubishi Kinsei MK-44 radial. Wingspan is 37' 7", length 28" 7". Design is extremely clean, with a minimum of obstruction to the airflow accounting somewhat for the high speed.

The Tojo, latest Japanese fighter thrown into battle by the Japs in the Pacific, is an excellent fighter, and shows decided improvement in Japanese design. First Nipponese warplane of any type to include a four-bladed prop, the Tojo is reported to have an engine more powerful than anything previously noted on Japanese fighters.

The remaining two Japanese fighter types not yet accounted for are still in the experimental stage. These types are identified simply as the Suzukaze 20 and the AT-27. Both aircraft spin contra-rotating props. The Suzukaze is powered by two tandem-mounted radial engines of approximately 1,250 hp each, has a large spinner, presents a peculiar contrast to standard single engine fighters. A long fin-like tail stretches from the pilot's cockpit straight out to the extreme tip of the rudder, with the fuselage generally resembling a long barrel. Four guns are arranged in each wing in pairs with one gun mounted above the other. Speed is claimed as 478 mph. The AT-27 is the first steam-cooled, inline-engine fighter to appear during this war. Extremely clean in design, the AT-27 mounts two 1,250-hp engines in tandem enclosed wholly in the cigar-shaped fuselage. A maximum speed of 410 mph is claimed but neither of these aircraft has appeared in active combat.

The Zero was christened thus by the double 00 in its designation. The last two digits in the S-00, incidentally, represents the Japanese year 2,600 corresponding to our 1940. S-001 would indicate, in the Mitsubishi designation, (but not for the other firms), that the S-001 was produced in 2601, and is a later model of the S-00. And so on for the 5-002, S-003, etc.

Contrary to popular American belief, the Zero did not make its debut in 1941 during the attack on Pearl Harbor, but appeared in China in 1936, in the form of the Mitsubishi 96 which established a nasty reputation for itself. During 1936, the Chinese Air Force captured two Japanese fighters. One model was equipped with fixed landing gear, attained a maximum speed of 285 mph. Amazingly agile, the aircraft presented a clean design, swept all opposition from the skies that encountered it. The other model, a special S-96, was the first Jap fighter to be equipped with retractable landing gear. This aircraft was the direct descendant of the Zero. Speed was boosted 30 mph by just the feature of retractable gear. From the lessons of these two aircraft, the S-97 was born. A low-wing, retractable gear monoplane, it boasted a high speed of 265 mph with a Mitsubishi Kinsei 650-hp radial.

About this time, the Kawasaki S-97 appeared. Identical to the Mitsubishi, its speed was boosted to 290 mph with the installation of an 850-hp two-row Kawasaki radial. Despite the fact that 1937 fighters of Mitsubishi and Kawasaki were low-wing aircraft of snappy appearance, the Kawasaki S-98 of the next year was a biplane. A single-seater of small size, it was intended for use against ground objectives. The liquid-cooled Kawasaki developed 820 hp for takeoff. Japan then tinkered with her copy of the Seversky P-35 pursuit, and produced a very good facsimile that exceeded the Seversky's performance in several aspects. From the lessons obtained from all these former aircraft, Japan secretly started mass production on the Zero. Sacrificing the lives of her peacetime airmen, Japan capitalized on light construction and a minimum of equipment for her fighters, applying every structural trick in the book to lighten construction and spare weight. Armor was discarded, self-sealing tanks were laughed at as so much excess weight, and Japan produced a fast, maneuverable, well climbing fighter — but a flying coffin for pilots. The skin of the Zero is fashioned from thinner gauge metal than we would consider using on our fighters. Plywood fuel tanks, armorless airframes, and fragile structure quickly disintegrated before heavy, tough, well-armed adversaries. Zeros promptly fell apart or rolled into balls of flame under the fire of American .50-cal guns.

The Mitsubishi Zero is a conventional-looking, radial-engine low-wing monoplane. The wing is evenly tapered with considerable dihedral, and rather long span. Due to the small size of the average Japanese pilot, the fuselage is slim, the cockpit cover being mounted above it and not forming contours of the fuselage proper. The radio antenna mast is mounted at the extreme rear of the cockpit, the landing gear retracts flush into the wings; the tail wheel retracts into the fuselage. Wing tips are hinged on the carrier model for storage below deck, and are operated by hand. The wide landing gear permits a fast landing speed, safe operation out of small fields.

A large bullet-like auxiliary fuel tank of wood may be suspended beneath the fuselage for extra range. Droppable, the tank is carried till the Zero enters combat, then is released as the fighter switches onto main tanks for the fights and flight home. This feature seemed to startle the Allies at first when the Mitsus began to turn up hundreds of miles from where they could logically be expected, even though Japanese fighters equipped with auxiliary fuel tanks were flying from anchored carriers off the coast of China in 1937.

When the tank is not carried, a 500-lb bomb may be installed to adapt the aircraft to use as a fighter-bomber. Turning radius of the S-001 Zeke is 440 yds, and just above that for the slightly heavier models. An exceptional rate of climb, perhaps the greatest of any fighter aircraft in the world today, is an outstanding ability of the Zero. The feat of being able to stick her nose almost vertically at the blue, and then climb at an initial rate of above 4,000 feet per minute, permits free and easy handling from small fields surrounded by high mountain peaks. This also means interception of bombers is immediate. Rate of dive is poor, due to fragile wing structure and the light weight of the machine. An extremely light wing loading of slightly over twenty pounds per square foot accounts for the high degree of maneuverability. A whirling dervish of a fighter, it presented a style of air fighting that was as startling as the hooks of an underhanded southpaw pitcher.

Armament of the S-001 is two .25- or .31-cal nose machine guns (7.7 mm), and two wing mounted 20-mm cannon. The later models have heavier armament. Muzzle velocity of the wing cannon is poor, due to the weak structure of the wing. Effective range of these weapons is only 350 yds as compared with the 500-yd range of our .50-cal Browning. Maximum speed of the S-001 is 345 mph at 13,000 feet, while the S-002 Hamp can surpass 365 mph. Service ceiling has been listed officially as 36,000 feet, but Zeros encountered at high altitudes have been known to stop climbing at 30,000 feet, sometimes fall off on one wing attempting to go on. American sources credit the S-001 Zeke with a Mitsubishi Kinsei power plant developing 1,200 hp, while British sources indicate a Mitsubishi Kinsei MK-44 1,050-hp radial. Horsepower of the Navy S-002 Hamp is kept at 1,050 hp by the British, while American sources claim an increase of about 100 hp.

The wingspan of the Zeke is 39' 5", length 30' 3", height 9', and wing area 256 sq ft. Loaded weight is 5,140 lbs, and 4,775 lbs for combat. The clipped wings of the Hamp reduce the wingspan to 35', and performance is generally increased. Range of both aircraft is 650 miles, but is extended to 1,600 miles with the use of the belly tank. Several models of the Hamp have been installed with armor plate, though it is still ineffective for any safe protection.

The S-003 Tony is a heavier machine than the preceding models, and resembles the He-113 in general construction. With the increased performance, and appearance of several new American fighters, the Zero is more dratted than dreaded.

This article was originally published in the June, 1944, issue of Air News magazine, vol 6,no 5, pp 24-26.
The original article includes 3 photos: 2 Hamp (in flight and on the ground with US markings) and an Oscar; and the page of side views above.
Photos and drawings credited to Air News, USAAF.
NOTE: in the article, the author refers to the S-002 as Hap; in deference to current usage and to the memory of General Arnold, I have renamed those references to Hamp. —JLM