Mitsubishi Ki 46 Timeline
12 December 1937: The Koku Hombu issued to Mitsubishi a specification for a fast
long-range reconnaissance aircraft. Endurance 6 hours at 400 km/h (249 mph.)
between 4,000 m. (13,125 ft.) and 6,000 m. (19,685 ft.). Maximum speed was
to be 600 km/h/4,000 m. (373 mph./13,125 ft.). Armament to be one 7.7 mm
type 89 rear-firing machine gun. The choice of engines either single or twin:
790 hp. Nakajima Ha-206, 950 hp. Nakajima Ha-25 or 850 hp. Mitsubishi Ha-26.
Note: The task of reaching these goals was assigned to Tomio Kubo and Joji
Hattori, who, from the outset, placed all emphasis on aerodynamic cleanliness,
adopting the minimum practical fuselage cross section and the thinnest available
wing section, while the Aeronautical Research Institute of the University of Tokyo
devoted its attention to the development of close-fitting, low drag cowlings for the
Mitsubishi Ha-26 that had been selected to power the new aircraft.
Early November 1939: The prototype was completed at Mitsubishi's Nagoya plant.
Late November 1939: The first flight piloted by Major Fujita at the controls took place
at Kagamigahara in Gifu Perfecture. The maximum speed reached was 540 km/h
(335.5 mph.) at 4,000 m. The engines were two Mitubishi Ha 26-1 of 900 hp. at
Note: Even though the speed of the Ki 46 fell short of the specifications it was still
faster than the Ki 43-1 (308 mph.) and A6M2 (331 mph.) undergoing trials at that
time so production of an initial batch was authorized under the designation Army
Type 100 Command Reconnaissance Plane Model 1.
Note: Mitsubishi had developed an advanced version of its Ha-26-I (Ha-102) Army
Type 101) engines with a 2-speed supercharger anticipated to develop 1080 hp./
T.O., and 1,035 hp. at 2,800 m. Take-off horse power was reached but the
and the engine could actually reach 1,050 hp./2,800 m and 950 hp./5,800 m.
With this engine the Ki 46 was anticipated to easily reach the initial
requirement speed. Mitsubishi was instructed to proceed with the Ki 46-II.
Late Spring 1940: The pre-series Ki 46-Ko (Ki 46-I) began to appear. These were
assigned to special units for intensive service evaluation and the Shimoshizu
Army Flying School for pilot training.
June 1940: Vapor locks occurred frequently under hot and humid weather conditions
so test were conducted in Formosa on the Ki 46-I. The Ki 46-II also went into these
test in June 1942. Correction were found by the changing from 87 to 92 octane fuel
and relocating the fuel lines around the engines.
March 1941: The first Ha-102 powered Ki 46-II was completed. Flight trials revealed a
maximum speed of 604 km/hr. at 5,800 m. (19,030 ft.). Range was increased to
2,485 ml./257 mph. (4,000 km/414 km/h).
July 1941: Ki 46-II aircraft were delivered to the 18th, 50th, 51st, 70th, 76th and 81st
Dokuritsu Dai Shijugo Chutais in Manchuria and China. The following is from pilot
notes: Oil overheated during the long climb to cruising altitude necessitating
slower rate of climb. The ailerons responded slowly and the rudder was ineffective.
The oxygen system was unreliable during long flights. Due to the aircrafts high rate
of sink, the undercarriage often collapsed on landing.
Note: Constant modifications eventually corrected the major difficulties.
20 & 22 October 1941: Captain Ikeda, commanding officer of a unit of Ki 46-IIs, that had
been moved to French Indo-China, reconnoitered the area selected by the Japanese
High Command for the planned amphibious landings in Malaya.
Note: When hostilities finally broke out, the Ki 46 units were deployed in small detachments
to cover the entire Southeast Asia area. The Army Type 100 Command Reconnaissance
planes were able to perform their missions with almost complete freedom from interception.
This was due to two reasons. There was no ground control radar to guide the Allied
obsolete fighters and the speed of the Ki 46. This ability attracted the attention of the
Japanese Navy which negotiated the acquisition of a small number of the type.
May 1942: The Koku Hombu had anticipated the arrival of faster Allied fighters and instructed
Mitsubishi to install their new 1500 hp. Ha-112-II into an improved version of the Ki 46 in
order to increase its maximum speed to 650 km/h (404 mph.) and its range by one hour.
Fuselage fuel capacity was increased from 1675 liters to 1895 liters. Provisions were made
for a 460 liter ventral drop tank. The landing gear was strengthened. The rear-firing 7.7 mm
machine gun was removed. The forward fuselage was changed and a new, more aero-
dynamic canopy was installed.
December 1942: Two Ki 46-III prototypes were completed with individual exhaust stacks which
increased speed slightly. Performance improved markedly between 8,000 m. and 10,000 m.
June 1943: Initial studies began to develop the Ki 46-III as a high-altitude interceptor by the
Rikugun Kocugijutsu Kenkyujo (Army Aerotechnical Research Institute). (K 46-III KAI)
1943-1944: Four Ki 46-IV (Tei) prototypes were built with 2 Ha-112-ii Ru engines capable of
1,500 hp./T.O., 1,250 hp./ 7,000 m., 1100 hp./10,200 m., that used exhaust-driven
turbo-superchargers. Fuel capacity was increased to 1,977 liters.
February 1944: Ki 46-IV flight test began, but difficulties with the turbo-supercharger delayed
October 1944: The first Ki 46-III KAI was completed.
November 1944: The Ki 46-III Kai began to be delivered to Operational units defending Japan.
The aircraft proved to be a disappointment because of its slow climb (once armed and
armored), taking 19 minutes to reach 8,000 m. All photographic equipment had been
removed and the nose was redesigned to hold two 20 mm. Ho-5 cannon. The central
fuselage fuel tank was removed and a forward obliquely mounted 37 mm. Ho-203 cannon
December 1944: The Nagoya plant producing Ki 46-IIs and -IIIs was heavily damaged by an
earthquake and Allied bombing. It was forced to move to Toyama, where only about 100
Ki 46s were completed.
February 1945: Two Ki 46-IVs flew 2,301 km at an average speed of 700 km/h with a strong
Note: Koku Hombu: Imperial Army's Air Headquarters.
Air International Vol.19 No.5
Japanese Aircraft of the Pacific War by Rene J Francillon
Edited by CORSNING, 19 March 2018 - 07:01 PM.