was a Japanese

aircraft designer Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is s ...

. He designed many

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

fighter aircraft used by the

Imperial Japanese Army Air Force The Imperial Japanese Army Air Service (IJAAS) or Imperial Japanese Army Air Force (IJAAF; ) was the Military aviation, aviation force of the Imperial Japanese Army (IJA). Its primary mission was to provide tactical close air support for ground ...

. His most important work was the , aka

Kawasaki Ki-61 The Kawasaki Ki-61 ''Hien'' (飛燕, "flying swallow") is a Japanese World War II fighter aircraft. Used by the Imperial Japanese Army Air Service, it was designated the "Army Type 3 Fighter" (三式戦闘機). Allied intelligence initially be ...

("flying swallow") or "''Tony''". Also he was one of the chief designers of the

Nihon Aircraft Manufacturing Corporation The Nihon Aircraft Manufacturing Corporation ( ''Nihon Kōkūki Seizō Kabushiki-gaisha''), or NAMC, was the manufacturer of Japan's only post-World War 2 production airliner to enter service, the YS-11. NAMC was a consortium of several manufac ...

(NAMC) YS-11.

Biography

Takeo Doi was born in Yamagata city,

Yamagata prefecture is a Prefectures of Japan, prefecture of Japan located in the Tōhoku region of Honshu. It has a population of 1,005,926 (1 February 2025) and an area of 9,325 Square kilometre, km2 (3,600 Square mile, sq mi). Its neighbours are Akita Prefectu ...

, Japan in 1904. He graduated from the Yamagata Higher School in 1924, and from the Department of

Aeronautics Aeronautics is the science or art involved with the study, design process, design, and manufacturing of air flight-capable machines, and the techniques of operating aircraft and rockets within the atmosphere. While the term originally referred ...

, Faculty of

Engineering Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...

Tokyo Imperial University The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public university, public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several Edo peri ...

in 1927 .

Jiro Horikoshi was a Japanese aeronautical engineer. He was the chief engineer of several Empire of Japan, Japanese Fighter aircraft, fighter aircraft designs used during World War II, most notably the Mitsubishi A6M Zero fighter, as well as the NAMC YS-11. E ...

and Hidemasa Kimura, who designed the

Mitsubishi A6M The Mitsubishi A6M "Zero" is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries. It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The ...

''Zero fighter'' and the ''Koken'' (Tokyo Imperial University Aeronautical Research Institute) Long-range Research-plane, respectively, were his classmates at the department in the university. In 1927 Doi started his career at the Aircraft Department of Kawasaki Dockyard Company Limited (

Kobe Kobe ( ; , ), officially , is the capital city of Hyōgo Prefecture, Japan. With a population of around 1.5 million, Kobe is Japan's List of Japanese cities by population, seventh-largest city and the third-largest port city after Port of Toky ...

, Japan), which later became Kawasaki Aircraft Company Limited in 1937. These are the predecessors of present

Kawasaki Heavy Industries Aerospace Company is the aerospace division of Kawasaki Heavy Industries (KHI). It produces aircraft, space systems, simulators, jet engines, missiles, and electronic equipment. During the 1930s and 1940s, Kawasaki Aircraft Industries developed numerous types o ...

reorganized in 1969. At that time, Dr. Richard Vogt was also working for the Kawasaki Dockyard Company Limited. The company invited Vogt from Germany as a technical advisor to teach its engineers in the construction techniques of

Dornier Dornier may refer to: * Claudius Dornier (1884–1969), German aircraft designer and builder ** Dornier Flugzeugwerke, German aircraft manufacturer founded in 1914 by Claudius Dornier * Dornier Consulting, international consulting and project manag ...

aircraft which Kawasaki was building under license. As a chief designer, Vogt trained Doi to be his successor. They worked jointly on several aircraft projects, including the (KDA-5 Army Type 92 biplane fighter, KDA-2 Army Type 88

reconnaissance In military operations, military reconnaissance () or scouting is the exploration of an area by military forces to obtain information about enemy forces, the terrain, and civil activities in the area of operations. In military jargon, reconnai ...

biplane, KDA-3 single-seat fighter, and KDA-5 Army Type 92-I biplane fighter). During this period, Doi was dispatched to

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, where he worked for one and a half years. In Europe he studied aircraft engineering. While Doi was in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

he paid attention to the technology of

George Dowty Sir George Herbert Dowty (27 March 1901 – 7 December 1975) was an English inventor and businessman. He founded Dowty Aviation in the 1930s producing aircraft components such as hydraulic systems, undercarriage units, and warning devices. Ea ...

, founder of Dowty Aviation. As Dowty's technology in aviation

hydraulic system Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...

s was state-of-the-art and met the requirement of the Japanese military, Doi chose Dowty equipment for the

landing gear Landing gear is the undercarriage of an aircraft or spacecraft that is used for taxiing, takeoff or landing. For aircraft, it is generally needed for all three of these. It was also formerly called ''alighting gear'' by some manufacturers, s ...

of the Army Type 92-I Fighter. This decision helped Dowty to develop his company, Dowty Aviation, and became a milestone for the expansion of the Dowty Equipment group thereafter. By strange coincidence,

Dowty Rotol Dowty Propellers is a British engineering company based in Brockworth, Gloucestershire that specialises in the manufacture, repair and overhaul of propellers and propeller components for customers around the world. It is owned by GE Aerospace ...

, descendant of the company, was the supplier of the propellers used on the

NAMC YS-11 The NAMC YS-11 is a turboprop airliner designed and built by the Nihon Aircraft Manufacturing Corporation (NAMC), a Japanese consortium. It was the only post-war airliner to be wholly designed and manufactured in Japan until the development of t ...

airliner. After Vogt returned to Germany, Doi became the key person in the design bureau of Kawasaki Aircraft until the company ceased operations at the end of

. His most important and outstanding work was the design of Army Type 3 Fighter

"''Hien''". Ki-61 ''Hien'' demonstrated surprising performance that surpassed the famous

Mitsubishi A6M Zero The Mitsubishi A6M "Zero" is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company, a part of Mitsubishi Heavy Industries. It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The ...

. A total of 3,159 Ki-61 ''Hien'' and its variants were built. After WWII, Doi was forced to interrupt work on aircraft design until the

Treaty of San Francisco The , also called the , re-established peaceful relations between Japan and the Allied Powers on behalf of the United Nations by ending the legal state of war, military occupation and providing for redress for hostile actions up to and inclu ...

came into force in 1952. During this period, he worked as a day laborer, while continuing to have faith that he would eventually return to aviation field. He continued to study the latest technology with Kimura who was the professor fired from the

University of Tokyo The University of Tokyo (, abbreviated as in Japanese and UTokyo in English) is a public research university in Bunkyō, Tokyo, Japan. Founded in 1877 as the nation's first modern university by the merger of several pre-westernisation era ins ...

.Swords into plowshares: Civilian application of wartime military technology in modern Japan, 1945-1964 (PDF)
/ref> Kimura was Doi's best friend. When the treaty lifted the ban on designing and operating aircraft, Doi returned to his original work. In 1956 the

Ministry of International Trade and Industry The was a Ministry (government department), ministry of the Government of Japan from 1949 to 2001. The MITI was one of the most powerful government agencies in Japan and, at the height of its influence, effectively ran much of Japanese industri ...

of Japan announced a domestic production plan of middle-sized commercial aircraft, i.e. the YS-11. The consortium of companies, the

(NAMC), was established. NAMC included

Mitsubishi Heavy Industries is a Japanese Multinational corporation, multinational engineering, electrical equipment and electronics corporation headquartered in Tokyo, Japan. MHI is one of the core companies of the Mitsubishi Group and its automobile division is the prede ...

, and

Fuji Heavy Industries , formerly , is a Japanese multinational corporation and conglomerate primarily involved in both terrestrial and aerospace transportation manufacturing. It is best known for its line of Subaru automobiles. Founded in 1953, the company was named ...

, Shinmeiwa Manufacturing, Japan Aircraft, Showa Aircraft, and

Kawasaki Heavy Industries is a Japanese Public company, public multinational corporation manufacturer of motorcycles, engines, Heavy equipment (construction), heavy equipment, aerospace and Military, defense equipment, rolling stock and ships, headquartered in Minato, To ...

(Kawasaki Aircraft). Doi was nominated the chief designer of equipment team. Doi became a professor at

Meijo University is a private university in Japan. Its main campus is in Tempaku-ku, Nagoya, Aichi Prefecture, and it has two other campuses in Nagoya, Aichi Prefecture. It had two faculty members who were Nobel laureates as of 2021. History The name Meij� ...

after he retired Kawasaki Heavy Industries. He also served as a councilor of the Japan Society for Aeronautical Science, a trustee of Japan Aeronautic Association, and an advisor emeritus of Kawasaki Heavy Industries. Details of his philosophy on aircraft design were written in his memoirs, regarding the designing policy, developmental history of the aviation technology, and his friends, published in Japan in 1989.

Aircraft of his design

Kawasaki Ki-10 The was the last biplane Fighter aircraft, fighter used by the Imperial Japanese Army, entering service in 1935 in aviation, 1935. Built by Kawasaki Aerospace Company, Kawasaki Kōkūki Kōgyō K.K. for the Imperial Japanese Army, it saw combat ...

(Army Type 95 Fighter) *

Kawasaki Ki-45 The Kawasaki Ki-45 ''Toryu'' (屠龍, "Dragonslayer") is a two-seat, twin-engine heavy fighter used by the Imperial Japanese Army in World War II. The army gave it the designation ; the Allied reporting name was "Nick". Originally serving as ...

"''Toryu''" (Army Type 2 Two-seat Fighter) *

Kawasaki Ki-48 The Kawasaki Ki-48 (, shortened to 'Soukei', Army Type 99 Twin-engined Light Bomber), is a Japanese twin-engine light bomber that was used during World War II. Its Allied reporting name was "Lily". Design and development The development of the ...

(Army Type 99 Bomber) * Kawasaki Ki-56 (Army Type 1 Transport Aircraft) *

"''Hien''" (Army Type 3 Fighter) * Kawasaki Ki-100 (Army Type 5 Fighter) *

* Kawasaki P-2J (customized Lockheed

P-2 Neptune The Lockheed P-2 Neptune (designated P2V by the United States Navy prior to September 1962) is a Maritime patrol aircraft, maritime patrol and anti-submarine warfare (ASW) aircraft. It was developed for the US Navy by Lockheed Corporation, Lockh ...

anti-submarine warfare Anti-submarine warfare (ASW, or in the older form A/S) is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations ar ...

aircraft)

Writings

* 航空機設計50年の回想 ("''Fifty Years Recollections on Aircraft Design''") by Takeo Doi (Kantosha, October 1989), * 軍用機開発物語 ("''Story of Warplane Development''") by Takeo Doi (Kojinsha, August 2007),

References

External links

Kawasaki Heavy Industries, Ltd.

(in Japanese) * ttp://www.aero.or.jp/web-koku-to-bunka/part2sakaidraft.html "Fifth Alumni of Department of Aeronautics, Tokyo Imperial University (Part 2)"in Airforum(in Japanese) {{DEFAULTSORT:Doi, Takeo Aircraft designers Japanese aerospace engineers 1904 births 1996 deaths People from Yamagata Prefecture University of Tokyo alumni