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Japan's Imperial Army flag

Japan's Mitsubishi Ki-21 bomber; Army Type 97 heavy bomber
Allied code name: originally Jane, later Sally

Photos

  • Mitsubishi Ki-21-11b Sally bomber
  • Mitsubishi Type 97, OB-97 bomber
  • Mitsubishi Type 97, OB-97 bomber

Design

Designed to meet a Imperial Japanese Army Air Force requirement that was given in 1936 / 1938. It was to be a heavy bomber. Nakata and Ozawa designed the Ki-21 to meet the specifications issued by Daihonei (air headquarters) on February 15, 1936.

Specifications:

  • Operating altitude: 6,500' - 13,000', 6,560' - 13,125' / 2,000 m - 4,000m
  • Endurance: 5 hours at 186 mph / 300 kph 5 hours at 187.5 mph
  • Speed: 250 mph at 10,000', 248.5 mph / 400 kph at 9,845' / 3,000 m
  • Climb: To 10,000' in 8 minutes, 9,845' / 3,000 m in 8 minutes
  • Crew: 4
  • Defensive armament: 3 machine guns
  • Bomb Load: 2,205 lb / 1,000 kg

Competition

Both Nakajima and Mitsubishi submitted prototypes and they were tested for six months.

The military ordered two more prototypes from each company and eventually decided on the Mitsubishi.

Improvements

In 1939 Mitsubishi was instructed to improve the Ki-21 and they replaced the Ha-6 engine with a Ha-101 engine to give the Ki-21 more performance.

Construction

The Ki-21 was made with a fabric covered metal frame.

Allied Naming

Originally given the name Jane after General MacArthur's wife, but the general didn't appreciate the name and it was changed to Sally.

When the Ki-21-IIb was scene it was initially thought to be a new version and was designated the Gwen. Once it was realized it was a modified Ki-21 it was redesignated the Sally 3. Sally 1 was the Ha-5 powered, and Sally 2 the Ha-101 powered Ki-21-IIas.

Prototype

The first Ki-21 prototype first flew in November 1936 / on December 18, 1936. The prototypes were evaluated against the Nakajima Ki-19s and Kawasaki Ki-22. It was found to have better performance and lighter wing loads. The Ki-19 had better flight characteristics and engines. These were combined into the Ki-21's third prototype.

The third prototype had by two Nakajima Ha-5s. Improved vertical tail surfaces.

Ki-21-II

Trials started in March 1940.

Ki-21-IIa

Trials started in December 1940.

Production

Produced by Mitsubishi and Nakajima. Production concluded in September 1944.

  • Prototypes: 2, 8
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Production: November 1936 - February 1938
  • Mitsubishi Ki-21: 8, 143
    • Numbers: 9 - 151
  • Mitsubishi Ki-21-I: 777
  • Mitsubishi Ki-21-Ia, Mitsubishi Ki-21-Ib, Mitsubishi Ki-21-Ic: 351, 774
    • Manufacturer: Nakajima Kikoki K.K.
    • Production: August 1938 - February 1941
  • Mitsubishi Ki-21-Ia, Army Type 97 Heavy Bomber Model 1A: 143
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Production: November 1937 - ?, March 1938 - 1939
  • Mitsubishi Ki-21-Ib: 120
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Numbers: 152 - 271
    • Production: 1939 - 1940
  • Mitsubishi Ki-21-Ic: 160
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Numbers: 272 - 431
    • Production: 1940
  • Mitsubishi Ki-21-II: 4, 1,278
    • First flew in December 1940
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Production: December 1940
  • Mitsubishi Ki-21-IIa, Army Type 97 Heavy Bomber Model 2A: 590
    • Production: December 1940 - ?, December 1940 - 1942
    • Manufacturer: Mitsubishi Jukogyo K.K.
  • Mitsubishi Ki-21-IIb: 688
    • Manufacturer: Mitsubishi Jukogyo K.K.
    • Production: 1942 - September 1944
  • Total: 2,064
    • Manufacturer: Mitsubishi, Mitsubishi Jukogyo K.K. at Nagoya, Nakajima Hikoki K.K. at Ota
    • Production: November 1936 - September 1944, March 1938 - September 1944

Variants

  • Mitsubishi Ki-21: Prototype.
  • Mitsubishi Ki-21-I: Had Mitsubishi Ha-6 radial engines (850 HP). In mid 1938 deliveries started.
  • Mitsubishi Ki-21-Ia, Army Type 97 Model 1A: Enlarged bomb bay. Production model.
  • Mitsubishi Ki-21-Ib: Better armament. Increased fuel. Fuel tanks protected by rubber sheets. Bomb bay made larger.
  • Mitsubishi Ki-21-Ic: Larger main wheels. Better armament. Increased fuel. An 110 gallon / 500 liter auxiliary fuel tank could be installed in rear of the bomb bay. When installed four 110 lb / 50 kg could be carried externally.
  • Mitsubishi Ki-21-II, Army Type 97 Heavy Bomber: Had Mitsubishi Ha-101 radial engines (1,500 HP). Horizontal tail surfaces were larger. Landing gear fully enclosed.
  • Mitsubishi Ki-21-IIa, Army Type 97 Heavy Bomber Model SA: Had a hand held 7.7 mm MG in rear dorsal position. Dorsal glasshouse replaced turret. Engines with more power. Landing gear modified.
  • Mitsubishi Ki-21-IIb, Army Type 97 Heavy Bomber Model 2B: Had 12.7 mm MG in a turret in the dorsal position. Dorsal glasshouse replaced turret.
  • Mitsubishi MC-21: Transport. Converted from Ki-21-Ia in China. All military equipment removed. Used by Dai Nippon Koku K. K. (Greater Japan Air Lines Co. Ltd). Nine soldiers could be carried. Some Army commanders used them as personal transports.

Usage

Used By

  • Sentais: 7th, 12th, 14th, 58th, 60th, 61st, 62nd, 92nd, 95th, and 98th
  • Dokuritsu Hikotai: 3rd
  • Hikodan: 22nd
  • Hikoshidan Shireibu Hikodan: 1st, 5th, 8th
  • Hamamatsu Army Bomber Flying School

First Unit

Towards the end of 1939 the 60th Hikosentai (air regiment) was equipped with the Ki-21.

Arrival in China

The 60th and 61st Sentai went to China with their Ki-21s in August 1938.

Pacific War

The Ki-21 was the main bomber in December 1941. It was used in the Malayan, Thai, Burmese, and Netherlands East Indies campaigns.

Philippines

The 5th Air Group, in Formosa, included the 14th and 62nd Hikosentais. They attacked Aparri, Tuguegarao, Vigan, and Luzon on December 8, 1941.

Indo-China

The 3rd Hikoshidan (Air Division), in Indo-China, including the 12th, 60th, and 98th Hikosentais bombed Siam and Malaya. There were a total of 87 Ki-21s.

When faced by P-40s and Hurricanes they suffered many losses.

Secondary Roles

By 1943 the Ki-21 was obsolete and was moved into secondary rolls. These included being a bomber trainer, communication aircraft, and a suicide plane.

Okinawa Commando Raid

The 3rd Dokuritsu Hikotai (Independent Wing) used Ki-21-IIbs to carry commandos that crash landed on Okinawa and caused much damage to aircraft and supply dumps.

Specifications

  Mitsubishi Ki-21
Type Medium bomber
Crew 5, 5 - 7
Pilot, co-pilot, bombardier / navigator, radio operator / gunner, gunner
Engine (Type) 2: Nakajima Ha-5 KAI
Cylinders Radial 14
Cooling Air
Net HP 850 each
Propeller blades 3 metal blade variable pitch
Dimensions  
Span 73' 9.75"
22.5 m
Length 52' 6"
16 m
Height 15' 11"
4.85 m
Armament 6: 7.7 mm MG
Normal bomb load 1,653 lb
750 kg
Maximum bomb load 2,205 lb
1,000 kg
  Mitsubishi Type 97
Type Long range bomber
Engine (Type) 2: Mitsubishi Kinsei A-14
Net HP 870 each
Dimensions  
Span 85'
Length 61'
Weight  
Loaded 24,000 lb
Performance  
Speed 225 mph
Range 2,500 miles
Armament  
Front 2: MG
Ventral 2: MG
Sides 2: MG
Tail 1: MG
Maximum bomb load 4,400 lb
  Mitsubishi Ki-21-I
Engine (Type) 2: Nakajima Ha-5 Kai
Cylinders Radial 14
Net HP 1,080 each
Propeller blades 3 each
Performance  
Speed @ 13,125' /
4,000 m
268 mph
431 kph
Climb 1,150'/minute
350 m/minute
Service ceiling 28,215'
8,600 m
Range 932 - 1,678 miles
1,500 - 2,700 km
  Mitsubishi Ki-21-Ia
Engine (Type) 2: Nakajima Ha-5
Fuel Capacity 580 gallons
Dimensions  
Span 73' 9 13/16"
22.5 m
Length 52' 5 29/32"
16 m
Height 14' 3 13/32"
4.35 m
Wing area 749.165 sq ft
69.6 sq m
Weight  
Empty 10,342 lb
4,691 kg
Loaded 17,452 lb
7,916 kg
Performance  
Speed at 13,125' / 4,000 m 268 mph
432 kph
Climb to 16,505' / 5,000 m 13 minutes 55 seconds
Service Ceiling 28,215'
8,600 m
Range - Normal 932 miles
1,500 km
Range - Maximum 1,680 miles
2,700 km
Armament  
Nose 1: 7.7 mm Type 89 MG
Ventral 1: 7.7 mm Type 89 MG
Dorsal 1: 7.7 mm Type 89 MG
  Mitsubishi Ki-21-Ib
Engine (Type) 2: Nakajima Ha-5 KAI
Cylinders Radial
Net HP 850 each
Armament  
Nose 1: 7.7 mm Type 89 MG
Dorsal 1: 7.7 mm Type 89 MG
Ventral 1: 7.7 mm Type 89 MG
Lateral 2: 7.7 mm Type 89 MG
Tail 1: 7.7 mm Type 89 MG
  Mitsubishi Ki-21-Ic
Engine (Type) 2: Nakajima Ha-5 KAI
Cylinders Radial
Net HP 850 each
Armament  
Nose 1: 7.7 mm Type 89 MG
Ventral 1: 7.7 mm Type 89 MG
Dorsal 1: 7.7 mm Type 89 MG
Tail 1: 7.7 mm Type 89 MG
Beam 2: 7.7 mm Type 89 MG
  Mitsubishi Ki-21-II
Engine (Type) 2: Mitsubishi Ha-101
Cylinders Radial 14
Cooling Air
Net HP 1,500 each
Propeller blades 3 each, 3 metal blade constant speed
Performance  
Speed @ 14,485' /
4,720 m
302 mph
486 kph
Climb 1,640'/minute
500 m/minute
Service ceiling 32,810'
10,000 m
Range 1,680 miles
2,700 km
  Mitsubishi Ki-21-IIb
Type Bomber, Medium Bomber
Crew 5
Engine (Type) 2: Mitsubishi Ha-101
2: Mitsubishi Ha-101 (Army Type 100)
Cylinders Radial, Radial 14
Cooling Air
Net HP 1,500 each
Dimensions  
Span 73' 9", 73' 9.75", 73' 9 13/16"
22.5 m
Length 52' 5 7/8", 52' 5 29/32", 52' 6"
16 m
Height 15' 10 7/8", 15' 10 15/16", 15' 11"
4.85 m
Wing area 749.16 sq ft, 749.165 sq ft, 749.2 sq ft
69.6 sq m
Weight  
Empty 13,382 lb
6,070 kg
Loaded 21,362 lb, 23,391 lb
10,610 kg
Performance  
Speed at 13,125' / 4,000 m 302 mph
486 kph
Speed at 15,485' / 4,720 m 302 mph
486 kph
Cruising Speed 236 mph
380 kph
Cruising Speed at 16,405' / 5,000 m 236 mph
380 kph
Climb to 19,685' / 6,000 m 13 minutes 13 seconds, 13.2 minutes
Service ceiling 32,810'
10,000 m
Range 1,680 miles
2,700 km
Armament 6: MG
Beam 2: 7.7 mm Type 89
Turret - Dorsal 1: 0.5" / 12.7 mm Type 1
Nose 1: 7.7 mm Type 89
Tail 1: 7.7 mm Type 89
Ventral 1: 7.7 mm Type 89
Bombs 2,200 lb, 2,205 lb
1,000 kg

Sources:

  1. Fighting Aircraft of World War II, Editor: Karen Leverington, 1995
  2. Aircraft of WWII, Stewart Wilson, 1998
  3. World War II Airplanes Volume 2, Enzo Angelucci, Paolo Matricardi, 1976
  4. Aeronautics Aircraft Spotters' Handbook, Ensign L. C. Guthman, 1943
  5. The Encyclopedia of Weapons of World War II, Chris Bishop, 1998
  6. Japanese Aircraft of the Pacific War, René J Francillon, 1970
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