Army Aeronautical Inspection Department (Tama Army Airfield)

The Army Aeronautical Inspection Department (陸軍航空審査部, Rikugun Kōkū Shinsabu) was the Imperial Japanese Army's supreme authority for the testing, evaluation, and approval of all new aircraft types and aviation weapons systems. Its origins trace back to December 1, 1939, when the Army Air Headquarters (陸軍航空本部) established a "Flight Experiment Division" (飛行実験部) at Tachikawa Airfield to conduct systematic flight testing of prototype aircraft separately from the Army Aviation Technology Research Institute (陸軍航空技術研究所).

On April 1, 1940, the Flight Experiment Division relocated from the increasingly crowded Tachikawa Airfield to the newly constructed Tama Army Airfield (多摩陸軍飛行場) in Fussa-machi, Nishi-Tama District, Tokyo Prefecture — locally known as the Fussa Airfield (福生飛行場). The new facility, with its 1,200-meter runway that began operations in August 1940, was purpose-built for flight testing, situated adjacent to the Tachikawa aviation industrial complex and Showa Aircraft Industries to the south.

On October 15, 1942, the organization was elevated and restructured by Imperial Ordinance No. 681 as the "Army Aeronautical Inspection Department" (陸軍航空審査部), consolidating the former Flight Experiment Division with elements of the Army Aviation Technology Research Institute's 5th Section (responsible for basic flight testing). This created a comprehensive testing organization with greater authority and resources than its predecessor.

The department's internal structure comprised the Main Headquarters (本部), administrative sections, and the critically important Flying Experiment Division (飛行実験部), which was subdivided into specialized squadrons: the Fighter Squadron (戦闘隊), Reconnaissance Squadron (偵察隊), Bomber Squadron (爆撃隊), Attack Squadron (攻撃隊), Special Squadron (特殊隊), and later a Special Weapons Squadron (特兵隊) responsible for testing rocket-powered and jet aircraft. A branch office was maintained in Harbin, Manchuria.

Department heads (部長) included: Lieutenant General Sakaguchi Yoshitarō (阪口芳太郎, October 1942 – May 1943), Major General Hashimoto Hidenobu (橋本秀信, May – December 1943), Major General Nakanishi Ryōsuke (中西良介, December 1943 – October 1944), Lieutenant General Teramoto Kumakichi (寺本熊市, October 1944 – June 1945), and Lieutenant General Ogata Tatsuyoshi (緒方辰義, from June 1945). Flying Experiment Division commanders included Colonel Katō Toshio (加藤敏雄, from October 1942) and Colonel Imagawa Issaku (今川一策, from September 1943).

The department's test pilots (テストパイロット, abbreviated "テスパイ") were hand-picked from the Army's finest combat aviators and represented the elite of Imperial Japanese military aviation. Notable members included: Major Aramaki Yoshitsugu (荒蒔義次), who had intercepted Doolittle Raid B-25s in April 1942 while test-flying a prototype Ki-61 at Mito; Captain Kuroe Yasuhiko (黒江保彦), a celebrated ace from the Nomonhan Incident and China campaigns who extensively flew captured P-51C Mustangs; Major Iwahashi Jōzō (岩橋譲三), the chief Ki-84 test pilot who declared upon his first flight "This will do!"; and many others including Ishikawa Tadashi, Kimura Kiyoshi, Sakagawa Toshio, Sakai Iori, Jinbo Susumu, and Katakura Jo.

The department tested virtually every significant aircraft type in the Imperial Japanese Army's inventory, from prototypes to production models: the Nakajima Ki-43 Hayabusa, Nakajima Ki-44 Shōki, Kawasaki Ki-61 Hien, Nakajima Ki-84 Hayate, Kawasaki Ki-100, Mitsubishi Ki-67 Hiryū, and experimental types including rocket interceptors. Equally significant was the systematic evaluation of captured Allied aircraft — including the North American P-51 Mustang, Boeing B-17, Curtiss P-40, Hawker Hurricane, and others — providing invaluable intelligence on enemy capabilities. The complex at Tama/Tachikawa was compared by Allied intelligence to the USAAF's own Wright-Patterson Field in Ohio.

Experienced test pilots from the department frequently served as founding commanders of front-line units equipped with new aircraft types. Commanders and core cadre for units such as the 47th Independent Chutai (Ki-44 Shōki), the 68th Sentai (Ki-61 Hien) and the 22nd Sentai (Ki-84 Hayate) were drawn from the Flying Experiment Division, ensuring that operational units benefited from deep technical knowledge of their new equipment.

As the strategic bombing campaign intensified in late 1944, the Flying Experiment Division's Fighter Squadron was reorganized into an emergency air defense unit — commonly known as the "Fussa Flying Unit" (福生飛行隊) — placed under the 10th Air Division for the defense of the Tokyo metropolitan area. These elite test pilots, intimately familiar with the performance envelopes of every Japanese fighter type, flew intercept missions against B-29 Superfortress formations attacking the capital.

On September 4, 1945, two days after the formal surrender ceremony aboard USS Missouri, a detachment of the U.S. Army 1st Cavalry Division arrived at the Tama Airfield. They found the facilities largely intact, with approximately 280 of the Imperial Japanese Army's most modern aircraft — including numerous prototypes and experimental types — preserved in hangars. This treasure trove of aviation technology proved invaluable for Allied technical intelligence. The base was initially renamed Fussa Army Airfield, then at the end of September 1945 redesignated Yokota Army Airfield (later Yokota Air Base) after a nearby village appearing on a 1944 American map.

The Army Aeronautical Inspection Department was formally abolished on November 10, 1945. Today, no wartime structures remain at the site, which has been entirely redeveloped as Yokota Air Base — the headquarters of United States Forces Japan (USFJ) and the 374th Airlift Wing. The base spans 7.14 square kilometers across the municipalities of Fussa, Hamura, Musashimurayama, Mizuho, Tachikawa, and Akishima. The legacy of the department lives on in the Japan Air Self-Defense Force's Air Development and Test Wing (飛行開発実験団) at Gifu Air Base, which is considered the spiritual successor to the wartime organization.