The Mitsubishi Ki-46 

Allied codename 'Dinah'

Japan
Japan

side viewfront viewunder view

If ever an aircraft deserved a female name, it must have been the 'Dinah' . The clean and gracefull lines of this aircraft were forboding to the speed and endurance that the type could reach. The Dinah was very successful for it's intended role: high altitude reconnaissance. It was respected by the Allies, and loved by it's crews, and was probably the most wanted aircraft to be manufactured under license by the German Luftwaffe (negotiations for a manufacturing license were to no avail, unluckily for the Germans).
The Ki-46 was designed specifically as a high-altitude reconnaissance aeroplane to meet a requirement issued in December 1937 by the Imperial Japanese Army Air Force. The service was currently operating a number of moderately good reconnaissance aircraft, but during 1937 decided that the time was ripe for the development of a considerably more advanced type that would be ‘state of the art’ in aerodynamic and propulsion terms, and also provide the service with a truly long-range capability for the obtaining of reconnaissance information at the strategic as well as the operational and tactical levels.
The requirement was issued only to Mitsubishi, which entrusted the task of designing the new aircraft to a team under the supervision of Tomio Kubo. The design team was able to draw on the company’s experience in designing and building the prototypes of the Ki-39 twin-engined long-range fighter (beaten to a production order by the Kawasaki Ki-45 Toryu) and its Ki-40 long-range reconnaissance derivative.
The Ki-46 was a cantilever low-wing monoplane of all-metal construction with fabric-covered control surfaces, and among its features were an airframe of exceptional aerodynamic cleanliness with the crew of two (separated by a fuel tank) in a raised cockpit section smoothly faired into the upper line of the forward fuselage, and fully retractable tailwheel landing gear. Trials revealed that the Ki-46 was some 37 mph (60 km/h) below the required maximum level speed of 373 mph (600 km/h), but the Imperial Japanese Army Air Force was satisfied with the type as it was somewhat faster that the new Nakajima Ki-43 Hayabusa fighter that was about to enter service, and ordered the Ki-46-I into production as the Army Type 100 Command Reconnaissance Aeroplane Model 1. At this time Mitsubishi was in the final stages of developing a more powerful radial engine that would allow Ki-46 to meet its speed requirement, but the service directed that a pre-production batch of Ki-46-I aircraft should nonetheless be completed for use by the Shimoshizu Army Flying School in the operational training role.

Version list:

Further pictures:

Top view of a Mitsubishi Ki-46 'Dinah' in full flight
Top view of a Mitsubishi Ki-46 'Dinah' in full flight

A Mitsubishi Ki-46 'Dinah' on an airfield
A Mitsubishi Ki-46 'Dinah' on an airfield

 

Technical data on the Mitsubishi Ki-46-I
Powerplant 2 × Mitsubishi Ha-26-I Army Type 99 Model 1 radial, rated at 900 hp (670.94 kW) each Role during war
  • Reconnaissance Aircraft
Length 36 ft 1.06 inch Height 12 ft 8.75 inch
Empty weight 7449 lb Operational weight 10631 lb typical
Wing Span 48 ft 2.75 inch Wing Aspect ratio 6.75
Wing Area 344.444 sq ft Service ceiling 35530 ft
Maximum speed 336 mph at 13350 ft Cruising speed unknown
Initial climb rate Climb to 16,405 ft in 7 min 45 sec Range 1305 miles typical
Fuel capacity internal 365 Imp gal (438 US gal) Fuel capacity external -
Machine guns
  • 1 × 0.303 inch Type 89 trainable rearward-firing in the rear cockpit
Cannons -
Bomb load -Torpedoes/rockets -
Crew 2: pilot, observer/radio operator/gunner Naval or ground based Ground
First flight (prototype) Late November 1939 Operational Service 1940 - 1945
Manufacturer Mitsubishi Jukogyo K.K. Number produced 1.742 total, 34 this version including prototypes
Metric system
Length 11 m Height 3.88 m
Empty weight 3379 kg Operational weight 4822 kg typical
Wing Span 14.7 m Wing Aspect ratio 6.75
Wing Area 32 m² Service ceiling 10830 m
Maximum speed 541 km/h at 4069 m Cruising speed unknown
Initial climb rate Climb to 5.000 m in 7 min 45 sec Range 2100 km typical
Fuel capacity internal 1.675 liters Fuel capacity external -
Machine guns
  • 1 × 7,7 mm Type 89 trainable rearward-firing in the rear cockpit
Cannons -
Bomb load -Torpedoes/rockets -

Technical data on the Mitsubishi Ki-46-II
Powerplant 2 × Mitsubishi Ha-102 Army Type 1 radial, rated at 1055 hp (786.49 kW) each Role during war
  • Reconnaissance Aircraft
Length 36 ft 1.06 inch Height 12 ft 8.75 inch
Empty weight 7194 lb Operational weight 11133 lb typical,
12787 lb max
Wing Span 48 ft 2.75 inch Wing Aspect ratio 6.75
Wing Area 344.444 sq ft Service ceiling 35170 ft
Maximum speed 375 mph at 19030 ft Cruising speed 249 mph at 13125 ft
Initial climb rate Climb to 26,250 ft in 17 min 58 sec Range 1537 miles typical
Fuel capacity internal 365 Imp gal (438 US gal) Fuel capacity external unknown
Machine guns
  • 1 × 0.303 inch Type 89 trainable rearward-firing in the rear cockpit
Cannons -
Bomb load -Torpedoes/rockets -
Crew 2: pilot, observer/radio operator/gunner Naval or ground based Ground
First flight (prototype) Late November 1939 Operational Service 1940 - 1945
Manufacturer Mitsubishi Jukogyo K.K. Number produced 1.742 total, 1.093 this version
Metric system
Length 11 m Height 3.88 m
Empty weight 3263 kg Operational weight 5050 kg typical,
5800 kg max
Wing Span 14.7 m Wing Aspect ratio 6.75
Wing Area 32 m² Service ceiling 10720 m
Maximum speed 603 km/h at 5800 m Cruising speed 401 km/h at 4000 m
Initial climb rate Climb to 8.000 m in 17 min 58 sec Range 2473 km typical
Fuel capacity internal 1.675 liters Fuel capacity external unknown
Machine guns
  • 1 × 7,7 mm Type 89 trainable rearward-firing in the rear cockpit
Cannons -
Bomb load -Torpedoes/rockets -

Technical data on the Mitsubishi Ki-46-III
Powerplant 2 × Mitsubishi Ha-112-II Army Type 4 radial, rated at 1500 hp (1118.23 kW) each Role during war
  • Reconnaissance Aircraft
Length 36 ft 1.06 inch Height 12 ft 8.75 inch
Empty weight 8446 lb Operational weight 12619 lb typical,
14330 lb max
Wing Span 48 ft 2.75 inch Wing Aspect ratio 6.75
Wing Area 344.444 sq ft Service ceiling 34450 ft
Maximum speed 391 mph at 19685 ft Cruising speed unknown
Initial climb rate Climb to 26,250 ft in 20 min 15 sec Range 2485 miles typical
Fuel capacity internal 417 Imp gal (500 US gal) Fuel capacity external 101 Imp gal (121 US gal) ventral drop tank
Machine guns -Cannons
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose (-IIIb and IIIc versions)
Bomb load -Torpedoes/rockets -
Crew 2: pilot, observer/radio operator/gunner Naval or ground based Ground
First flight (prototype) Late November 1939 Operational Service 1940 - 1945
Manufacturer Mitsubishi Jukogyo K.K. Number produced 1.742 total, 611 Ki-46-III's including prototypes
Metric system
Length 11 m Height 3.88 m
Empty weight 3831 kg Operational weight 5724 kg typical,
6500 kg max
Wing Span 14.7 m Wing Aspect ratio 6.75
Wing Area 32 m² Service ceiling 10500 m
Maximum speed 629 km/h at 6000 m Cruising speed unknown
Initial climb rate Climb to 8.000 m in 20 min 15 sec Range 3999 km typical
Fuel capacity internal 1.895 liters Fuel capacity external 460 liters ventral drop tank
Machine guns -Cannons
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose (-IIIb and IIIc versions)
Bomb load -Torpedoes/rockets -

Technical data on the Mitsubishi Ki-46-III KAI
Powerplant 2 × Mitsubishi Ha-112-II Army Type 4 radial, rated at 1500 hp (1118.23 kW) each Role during war
  • Fighter
  • Reconnaissance Aircraft
Length 37 ft 8.19 inch Height 12 ft 8.75 inch
Empty weight 8446 lb Operational weight 13730 lb typical
Wing Span 48 ft 2.75 inch Wing Aspect ratio 6.75
Wing Area 344.444 sq ft Service ceiling 34450 ft
Maximum speed 391 mph at 19685 ft Cruising speed unknown
Initial climb rate Climb to 26,250 ft in 19 min 0 sec Range 1243 miles typical
Fuel capacity internal Less than 417 Imp gal (500 US gal) Fuel capacity external 101 Imp gal (121 US gal) ventral drop tank
Machine guns -Cannons
  • 1 × 37 mm Ho-203 fixed oblique-firing (up- and forward) in the rear fuselage
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose
Bomb load -Torpedoes/rockets -
Crew 2: pilot, observer/radio operator/gunner Naval or ground based Ground
First flight (prototype) Late November 1939 Operational Service 1940 - 1945
Manufacturer Mitsubishi Jukogyo K.K. Number produced 1.742 total, 611 Ki-46-III's including prototypes
Metric system
Length 11.49 m Height 3.88 m
Empty weight 3831 kg Operational weight 6228 kg typical
Wing Span 14.7 m Wing Aspect ratio 6.75
Wing Area 32 m² Service ceiling 10500 m
Maximum speed 629 km/h at 6000 m Cruising speed unknown
Initial climb rate Climb to 8.000 m in 19 min 0 sec Range 2000 km typical
Fuel capacity internal Less than 1.895 liters Fuel capacity external 460 liters ventral drop tank
Machine guns -Cannons
  • 1 × 37 mm Ho-203 fixed oblique-firing (up- and forward) in the rear fuselage
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose
Bomb load -Torpedoes/rockets -

Technical data on the Mitsubishi Ki-46-IVa
Powerplant 2 × Mitsubishi Ha-112-II Ru radial, rated at 1500 hp (1118.23 kW) each Role during war
  • Reconnaissance Aircraft
Length 36 ft 1.06 inch Height 12 ft 8.75 inch
Empty weight 8840 lb Operational weight 13007 lb typical,
14330 lb max
Wing Span 48 ft 2.75 inch Wing Aspect ratio 6.75
Wing Area 344.444 sq ft Service ceiling 36090 ft
Maximum speed 391 mph at 32810 ft Cruising speed 280 mph at 13125 ft
Initial climb rate Climb to 32,810 ft in 16 min 30 sec Range 2485 miles typical
Fuel capacity internal 435 Imp gal (522 US gal) Fuel capacity external 101 Imp gal (121 US gal) ventral drop tank
Machine guns -Cannons
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose (-IVb version)
Bomb load -Torpedoes/rockets -
Crew 2: pilot, observer/radio operator/gunner Naval or ground based Ground
First flight (prototype) Late November 1939 Operational Service 1940 - 1945
Manufacturer Mitsubishi Jukogyo K.K. Number produced 1.742 total, 4 this version (all prototypes)
Metric system
Length 11 m Height 3.88 m
Empty weight 4010 kg Operational weight 5900 kg typical,
6500 kg max
Wing Span 14.7 m Wing Aspect ratio 6.75
Wing Area 32 m² Service ceiling 11000 m
Maximum speed 629 km/h at 10000 m Cruising speed 451 km/h at 4000 m
Initial climb rate Climb to 10.000 m in 16 min 30 sec Range 3999 km typical
Fuel capacity internal 1.977 liters Fuel capacity external 460 liters ventral drop tank
Machine guns -Cannons
  • 2 × 20 mm Ho-5 fixed forward-firing in the nose (-IVb version)
Bomb load -Torpedoes/rockets -

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Mitsubishi Ki-46 
Mitsubishi Ki-46-I The ki-46 took it's time between the conception of the idea, and the delivery of it's first prototype. However, the wait was not in vain. It took such a long time because extensive wind-tunnel tests were performed at the Aeronautical Research Institute of the University of Tokyo. These tests resulted in the excellent close-fitting cowlings, and other aerodynamic features. Furthermore, the Institute designed the fully retractable landing gear of the Ki-46.
Even so, the prototype failed the speed requirement set by the Imperial Japanese Army by 40 mph (64 km/h), but all other criteria of endurance, range, handling, cockpit visibility were sufficient or exceeding the requirements. The Ki-46 was still faster than the Nakajima Ki-43-I Hayabusa which was entering service at that time, and the Mitsubishi A6M2. Furthermore, Mitsubishi was in the final stages of the development of a more advanced version of the Ha26-I engine with a higher power output, and without an increase in diameter (and thus no increase in drag). Production was started at full.
Number built: 34 including prototypes
Mitsubishi Ki-46-II The Ki-46-I was delivered to the Shimoshizu Rikugun Hikogakuko (Shimoshizu Army Flying School), and experience learned that there were still a few flaws. Apart from the more advanced and uprated powerplant, other things were attended too as well. these issues included Vapour locks under hot and humid weather conditions which was finally solved with the switch from 87-Octane to 92-Octane fuel and relocation of the fuel lines. Also pilots complained of overheating oil during long climbs, which rendered the actual climb rate as opposed to theoretical climb rate inadequate. Ailerons responded slowly and rudder was ineffective. Also there were problems with the oxygen system, which was unreliable. Last but not least the landing gear was not strong enough to cope with the high sink rate of the aircraft during the landing, and collapsed regularly.
the first Ki-46-II was completed in March 1941, and proved that with the new engines the Ki-46 was able to exceed the maximum level speed requirement of 373 mph (600 km/h) at 13,125 ft (4.000 m) by 375 mph (604 km/h) at 19,030 ft (5.800 m). this speed and height made the Ki-46 hard to intercept by especially the obsolescent enemy fighters of China and the Allied forces during the early years of the War.
Number built: 1.093
Mitsubishi Ki-46-II KAI this version was a conversion of the original Mitsubishi Ki-46-II. It was used as a three-seat radio and navigation trainer. This aircraft had a stepped cockpit in two stages, the first was like the original, the second step was the new position for the third crewmember (instructor?).
Number converted: unknown
Mitsubishi Ki-46-III This version that first flew in December 1943 had a yet further improved powerplant, 2 × Mitsubishi Ha-102-II with direct fuel injection. The higher fuel consumption of these engines and the requirement for a longer endurance and higher speed yet meant that the fuel capacity needed to be increased. An additional fuel tank in front of the pilot was installed, together with provisions for a ventral drop tank. On the downside of the newer engine was the neede for larger engine nacelles, because the engine was slightly larger. To accomodate the increase in weight the landing gear had to be strengthened as well.
the most visible difference of the new version was the cockpit canopy, however. The stepped cockpit was changed with a glazed and curved one that started at the nose of the aircraft.
Later production aircraft also were fitted with individual exhaust stacks that provided some thrust augmentation and increased speed and range accordingly.
The rear gun was omitted because experience had shown that in the field the gun was almost always removed. This left the Ki-46-III unarmed, and totally depending upon it's speed and height.
Number built: 611 including 2 prototypes
Mitsubishi Ki-46-III KAI The excellent performance of the Dinah suggested that the type could be adapted for the bomber interceptor role, and some aircraft were modified as such. Armament was installed in the nose, being 2 × 20 mm Ho-5 fixed forward-firing cannon. All reconnaissance equipment was removed, and in the fuselage 1 × 37 mm Ho-203 fixed obliquely upward and forward firing cannon was installed, like a German Schräge Musik installation. This was all only intermediate since other specialised aircraft were expected to enter service soon.
Number converted: unknown
Mitsubishi Ki-46-IIIb The Mitsubishi Ki-46-III KAI proved unsuccesful because of it's poor climb rate, and the only other conversion was an attack aircraft. It was identical to the Mitsubishi Ki-46-III KAI, but had the 37 mm cannon removed.
Number converted: unknown
Mitsubishi Ki-46-IIIc This version only remained on the drawing board, and was intended to act as an attack aircraft like the Mitsubishi Ki-46-IIIb. No further details are known
Number converted: 0
Mitsubishi Ki-46-IV This final version of the Dinah had an improved powerplant yet, fitted with turbosuperchargers. These chargers gave the aircraft superios performance at altitude. The engine nacelles were modified to accomodate a methanol-cooled air-intake, and fuel capacity was increased once more. No operational aircraft were built
Number built: 4
Mitsubishi Ki-46-IVb This would have been an attack fighter, but even the on the drawing board this version was scratched.
Number converted: 0
Army Type 100 Command Reconnaissance Aeroplane Model I Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-I 'Dinah'
Army Type 100 Command Reconnaissance Aeroplane Model 2 Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-II 'Dinah'
Army Type 100 Operations Trainer Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-II KAI 'Dinah'
Army Type 100 Command Reconnaissance Aeroplane Model 3 Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-III 'Dinah'
Army Type 100 Air Defense Fighter Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-III KAI 'Dinah'
Army Type 100 Assault Aeroplane Official Imperial Japanese Army Air Force designation for the Mitsubishi Ki-46-IIIb 'Dinah'. No official designation for the Ki-46-IV exists, since it was only in prototype phase.

Operational remarks:

the Ki-46 Dinah was not only one of the most beautiful aircraft of the War, it was probably the best reconnaissance aircraft as well. The Dinah was almost untoucheable by enemy fighters, so it could perform it's task with almost immunity.
throughout the Pacific the Dinah was the eyes of the Japanese Army, with great effectiveness. Countless mission reports of the Allied show that the Dinah was mostly out of range again before the Allies were able to put any fighters in the air to intercept them. The Dinah kept a close watch on even heavily armed and defended airfileds like the Boeing B-29 airbases at the end of the war.
In fact, the Allied forces only had a chance to intercept the Dinah when they were forewarned with help of ground control radar, and were fitted with powerful fighters that could climb well like the Lockheed P-38F's and the Supermarine Spitfire V's.
Even so, at the end of the War the Dinah again showed it's excellent breeding, for two Ki-46-IV's covered 1,430 miles (2.301 km) at an average speed of 435 mph (700 km/h) in Februari 1945. Another reconnaissance was the following of B-29 bombers that were heading for the Japanese homelands. the Dinah's could give an accurate report of the height, speed, position and direction of the enemy bombers to ground control, which could in turn alert the right units to try and intercept the B-29's.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 9/23/01