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Mitsubishi Ki-46

mitsi-ki-46
Ki-46-III KAI


The Mitsubishi Ki-46 was designed to meet an Imperial Japanese Army requirement of 1937 for a higher performance reconnaissance aircraft to supersede the Ki-15. The specification called for an endurance of six hours at 250mph (400 km/h), between 13,500 and 20,000 ft (4,000 and 6,000m) and a maximum speed of 375mph (604km/h) at 13,500 ft (4,000m). The man responsible for the design was Tomio Kubo, who was assisted by the Aeronautical Research Institute of the University of Tokyo.

Work on the design started in December 1937, as a cantilever low-wing monoplane with retractable tailwheel landing gear, powered by two 900-hp / 671kW Mitsubishi Ha-26 radial engines. Kubo selected a small diameter fuselage with the main fuel tank located between pilot and observer, and thin section wings.

The two-seat Ki-46 prototype was flown (by Major Fujita) for the first time in late November 1939 from Kagamigahara in Gifu Prefecture, north of Nagoya. Early testing showed that maximum speed of the Ki-46 was some 10% below specification (540 km/h / 335 mph) at 4000 m / 13,000 ft), but as its speed and overall performance was better than in-service army and navy aircraft the type was ordered into production as the Army Type 100 Command Reconnaissance Plane Model 1 (Ki-46-l), later allocated the Allied codename 'Dinah'.

The entire Model 1 production (34 were built between 1939-40) plus the prototype were delivered to the Shimshizu flying school and to a special experimental reconnaissance unit. The aircraft was known as the Shintei in Japanese service, but was soon better known to the allies under its simplified identification name, the Dinah.

The Ki-46-1 series was soon replaced by the Ki-46II, which utilised the more powerful Ha102 engines, fitted with two-speed supercharger and rated at 1,080 hp each. The increase in available horsepower meant that the performance of the II improved, maximum speed rose to 375 mph (604 kph) at 19,030 ft (5,800 m). The transition to the new series was not without its problems, vapour locks were experienced and it was only after extensive research that the cause was found. Relocation of the fuel lines around the engines and a change from 87 to 92-octane fuel seemed to cure it. Poor aileron and rudder response, overheating of the oil and an unreliable oxygen system that to crew anoxia, were all problems which had to be overcome. Another problem involved the undercarriage, due to the aircraft's high rate of sink it was quite a common occurrence for the undercarriage to collapse on landing. Although stronger auxiliary rear struts were fitted this problem was to persist throughout the Ki-46's operational life.

The first Model 2 appeared in March 1941, the airframe was identical with the Model 1 and production soon gathered momentum. The Type 100 was delivered from July 1941 onwards to the 18th, 50th, 51st, 70th, 74th, 76th and 81st Independent Chutais (squadrons) based in China and Manchuria. Chinese air opposition was poor and the escape capability of Ki-46 such that the sole defensive armament, a single 7.7-mrn (0.303-in) Type 89 machine-gun on a flexible mounting operated by the observer, was seldom used in action.

During October 1941 Ki-46s based in French Indo-China reconnoitred the Japanese army's planned landing zones for the December invasion of Malaya. From December 1941 onwards, Ki-46s were deployed in small detachments in every army zone of operations, enjoying considerable success and remaining virtually unmolested for the first year of fighting. Such was the esteem in which the type was held that the Luftwaffe attempted to arrange licence pro-duction, and the army's greatest rival, the navy, managed to acquire a few for its own use.

As the losses suffered by the Ki-46II units increased the Koku Hombu, in May 1942, they instructed Mitsubishi to upgrade the Ki-46-II. This was achieved with the installation of two Mitsubishi Ha 112-II engines, rated at 1,500hp each, this boosted the top speed to 404 mph (650 km/h) and increased the range to 2,485 miles and endurance by an hour. The new design was designated the Ki-46-III and with it came a whole new shape. Gone was the steped canopy of the II series and in came a completely aerodynamic nose, with the canopy glazing extending right to the front of the aircraft in a smooth slope. The reason for the re-designed front was a simple, not just one born of aerodynamic necessity. The new engines required more fuel and the thin wing adopted in the original design allowed no room for fuel cells, it was therefore decided to fit an additional tank in front of the pilot. This tank held 52 Imp Gal (220 litres), provision was also made for the fitment of a ventral drop tank, holding 101.2 Imp Gal (460 litres). The undercarriage was beefed up and the provision for a single flexible machine gun in the rear cockpit was dispensed with.

As supply of the III series increased, some II's were converted into three seat radio navigation trainers, designated the Ki46-II Kai, they operated with the Shimoshizu Rikugun Hikogakuko (Shimoshizu Army Flying School).

609 Ki-46-III were built, a small number being converted later as Ki-46-III KAI fighter interceptors and Ki-46IIIb ground-attack aircraft.

The Ki-46-II and the Ki46-IIKai (Kai=KAIZO "Modified") trainer were the main production version of the Ki-46 design, with 1,093 being built.

In June 1943, the Rikugun Kokugijutsu Kenkyujo, or Army Aerotechnical Research Institute, began to study the adapta-tion of the Ki-46-III reconnaissance aircraft for the high-altitude interceptor fighter role. Development was actively pursued from May 1944 as the Ki-46-III KAI, or Army Type 100 Air Defence Fighter, and the Army Air Arsenal at Tachikawa instituted a conversion programme.

The nose was redesigned a new stepped cockpit canopy, and to accommodate two 20-mm Ho-5 cannon and the top centre fuselage fuel tank was removed to provide space for a Ho-203 37-mm cannon firing forward and upward at an angle of 30 deg. The two Mitsubishi Ha-112-lI engines rated at 1,500 hp for take-off were retained, and the first Ki-46-IIl KAI two-seat interceptor was completed by Tachikawa Dai-lchi Rikugun Kokushok and flown in October 1944, deliveries to operational units commencing during November. Operational results were disappointing owing to the poor climb rate of this type, but the conversion programme was continued at Tachikawa until March 1945, a substantial number being delivered. One unit was the 16th Dokuritsu, Hikotai, which operated in the latter months of the war.

With more powerful 1500-hp Mitsubishi Ha-112-11 engines and increased range, thanks to enlarged internal tankage and the introduction of a 460-litre (101-Imp gal) ventral drop tank, Model 3 showed a 26 km/h (16 mph) improvement in top speed over Model 2 and achieved a maximum range of 4000 km (2500 miles). External appearance was greatly changed by the new canopy over the pilot's cockpit, without the conventional step between the nose and top of fuselage which had charac-terized the earlier versions. Performance was so good that defensive armament was dis-pensed with. Production at Mitsubishi's Nagoya factory was hindered by earthquake damage in December 1944, and a further 100 of the type were built at Toyama.

Late production Ki-46-III's coming from both plants were fitted with individual exhaust stacks providing some thrust augmentation, which increased their speed and range slightly.

Operational trainer modifications of the Model 2 serving with the specialist Shimshizu flying school had a third, stepped-up cockpit fitted immediately behind the pilot's seat.

A few Ki-46-IIIb assault aircraft, devel-oped from the intercepter, were built, and four Ki-46-IV high-altitude prototypes during 1943 & 44, powered by 1,100 hp / 1119kW (at 33,465 ft / 10,200 m) Mitsubishi Ha-112-Ru supercharged engines, were tested from February 1944 onwards. Difficulties with the superchargers prevented production of the proposed reconnaissance and fighter versions. Total production of the Ki-46 in all variants was 1742 of which 902 were the III series, all built by Mitsubishi. All were initially manufactured by Mitsubishi at their Nagoya plant, but when this was damaged by an earthquake in December 1944, as well as being pounded by the B-29's of the US Air Force, production was transferred to their new plant at Toyama. Only about one hundred aircraft came out of this plant by wars end.

Production:
34 Ki-46 prototypes and Ki-46-I production aircraft (1939-40)
1,093 Ki-46-II production aircraft (1940-44)
2 Ki-46-III prototypes (1942)
609 Ki-46-III production aircraft, inc fighter conversions (1942-45)
4 Ki-46-IV prototypes (1943-44)


Ki-46-I
Engines: 2 x 900 hp Army Type 99 Model 1 Mitsubishi Ha-26-1 radials
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Empty weight: 7,449 lb (3,379 kg)
Loaded weight: 10,631 lb (4,822 kg)
Max speed: 335.5 mph at 13,350 ft
Range: 1,305 Miles (2,100 km)
Armament: One 7.7 mm Type 89 rear-firing machine-gun

Ki-46-II

Engines: 2 x 1,050 hp Army Type 1 Mitsubishi Ha102 radials
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Loaded weight: 11,133 lb (5,050 kg)
Empty weight: 7,194 lb (3263 kg)
Maximum speed: 604 km/h (375 mph)
Max speed: 375 mph at 19,030 ft
Range: 1,537 Miles (2,474 km)
Armament: One 7.7 mm Type 89 rear-firing machine-gun

Ki-46-II Kai
Engines: 2 x 1,050 hp Army Type 1 Mitsubishi Ha102 radials
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Armament: One 7.7 mm Type 89 rear-firing machine-gun

Ki-46-III
Engines: 2 x Army Type 4  Mitsubishi Ha-112-II radials, 1125kW / 1,500 hp
Max take-off weight: 5722-6500 kg / 12615 - 14330 lb
Empty weight: 8,446 lb (3,831 kg)
Loaded weight: 12,619 lb (5,722 kg)
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Wing area: 32.0 sq.m / 344.44 sq ft
Max. speed: 630 km/h / 391 mph at 19,685 ft
Ceiling: 10500 m / 34450 ft
Range w/max.fuel: 4000 km / 2486 miles
Crew: 2

Ki-46IIIa
Engines: 2 x Army Type 4  Mitsubishi Ha-112-II radials, 1125kW / 1,500 hp
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Empty weight: 8,446 lb (3,831 kg)
Loaded weight: 12,619 lb (5,722 kg)
Max speed: 391 mph at 19,685 ft
Range: 2,485 Miles (4,000 km)

Ki-46IIIb
Engines: 2 x Army Type 4  Mitsubishi Ha-112-II radials, 1125kW / 1,500 hp
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Empty weight: 8,446 lb (3,831 kg)
Loaded weight: 12,619 lb (5,722 kg)
Max speed: 391 mph at 19,685 ft
Range: 2,485 Miles (4,000 km)

Ki-46IIIc
Engines: 2 x Army Type 4  Mitsubishi Ha-112-II radials, 1125kW / 1,500 hp
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Empty weight: 8,446 lb (3,831 kg)
Loaded weight: 12,619 lb (5,722 kg)
Max speed: 391 mph at 19,685 ft
Range: 2,485 Miles (4,000 km)

Ki-46-III KAI

Engines: 2 x Army Type 4  Mitsubishi Ha-112-II radials, 1125kW / 1,500 hp
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length, 37 ft 8¼ in (11,48 m)
Wing area, 344.44 sq ft (32,00 sq.m)
Max speed, 391 mph (630 km/h) at 19,685 ft (6 000 m)
Range, 1,243 mls (2 000 km) plus one hour combat
Time to 26,250 ft (8 000 m), 19 min.
Empty weight, 8,446 lb (3 831 kg)
Loaded weight. 13,730 lb (6 228 kg)
Armament: One 37 mm Ho-203 cannon, two 20 mm Ho-5 cannons

Ki-46-IV
Engines: 2 x 1,500 hp Mitsubishi Ha-112-II Ru radials
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)

Ki-46-IVa
Engines: 2 x 1,500 hp Mitsubishi Ha-112-II Ru radials
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)
Empty weight: 8,840 lb (4,010 kg)
Loaded weight: 13,007 lb (5,900 kg)
Max speed: 391 mph at 19,685 ft
Range: 2,485 Miles (4,000 km)

Ki-46-IVb
Wingspan: 48 ft 2.75 in (14.7m)
Height: 12 ft 8.75 in (3.88m)
Length: 36ft 1 1/16 in (11.0m)

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Mitsubishi Ki-46

 

 

 


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