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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 19361 / 19382. It was to be a heavy bomber.2 Nakata and Ozawa designed the Ki-21 to meet the specifications issued by Daihonei (air headquarters) on February 15, 1936.5,6

Specifications:

  • Operating altitude: 6,500' - 13,000'3, 6,560' - 13,125' / 2,000 m - 4,000m6
  • Endurance: 5 hours at 186 mph / 300 kph6 5 hours at 187.5 mph3
  • Speed: 250 mph at 10,000'3, 248.5 mph / 400 kph at 9,845' / 3,000 m6
  • Climb: To 10,000' in 8 minutes3, 9,845' / 3,000 m in 8 minutes6
  • Crew: 46
  • Defensive armament: 3 machine guns6
  • Bomb Load: 2,205 lb / 1,000 kg6

Competition

Both Nakajima and Mitsubishi submitted prototypes and they were tested for six months.3

The military ordered two more prototypes from each company and eventually decided on the Mitsubishi.3

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.1

Construction

The Ki-21 was made with a fabric covered metal frame.6

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.6

When the Ki-21-IIb was scene it was initially thought to be a new version and was designated the Gwen.6 Once it was realized it was a modified Ki-21 it was redesignated the Sally 3.6 Sally 1 was the Ha-5 powered, and Sally 2 the Ha-101 powered Ki-21-IIas.6

Prototype

The first Ki-21 prototype first flew in November 19362 / on December 18, 19361,3,5,6. The prototypes were evaluated against the Nakajima Ki-19s and Kawasaki Ki-22.6 It was found to have better performance and lighter wing loads.6 The Ki-19 had better flight characteristics and engines.6 These were combined into the Ki-21's third prototype.6

The third prototype had by two Nakajima Ha-5s.6 Improved vertical tail surfaces.6

Ki-21-II

Trials started in March 1940.6

Ki-21-IIa

Trials started in December 1940.6

Production

Produced by Mitsubishi and Nakajima.1 Production concluded in September 1944.2

  • Prototypes: 25, 86
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Production: November 1936 - February 19386
  • Mitsubishi Ki-21: 82, 1436
    • Numbers: 9 - 1516
  • Mitsubishi Ki-21-I: 7771
  • Mitsubishi Ki-21-Ia, Mitsubishi Ki-21-Ib, Mitsubishi Ki-21-Ic: 3516, 7742
    • Manufacturer: Nakajima Kikoki K.K.6
    • Production: August 1938 - February 19416
  • Mitsubishi Ki-21-Ia, Army Type 97 Heavy Bomber Model 1A: 1436
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Production: November 1937 - ?3, March 1938 - 19396
  • Mitsubishi Ki-21-Ib: 1203,6
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Numbers: 152 - 2716
    • Production: 1939 - 19406
  • Mitsubishi Ki-21-Ic: 1603,6
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Numbers: 272 - 4316
    • Production: 19406
  • Mitsubishi Ki-21-II: 42,6, 1,2781
    • First flew in December 19402
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Production: December 19406
  • Mitsubishi Ki-21-IIa, Army Type 97 Heavy Bomber Model 2A: 5902,3,6
    • Production: December 1940 - ?3, December 1940 - 19426
    • Manufacturer: Mitsubishi Jukogyo K.K.6
  • Mitsubishi Ki-21-IIb: 6882,3,6
    • Manufacturer: Mitsubishi Jukogyo K.K.6
    • Production: 1942 - September 19446
  • Total: 2,0642,3,5,6
    • Manufacturer: Mitsubishi2, Mitsubishi Jukogyo K.K. at Nagoya3,6, Nakajima Hikoki K.K. at Ota2,6
    • Production: November 1936 - September 19446, March 1938 - September 19443

Variants

  • Mitsubishi Ki-21: Prototype.2
  • Mitsubishi Ki-21-I: Had Mitsubishi Ha-6 radial engines (850 HP).1 In mid 1938 deliveries started.2
  • Mitsubishi Ki-21-Ia, Army Type 97 Model 1A: Enlarged bomb bay.2 Production model.5
  • Mitsubishi Ki-21-Ib: Better armament.3,5 Increased fuel.3,5 Fuel tanks protected by rubber sheets.6 Bomb bay made larger.6
  • Mitsubishi Ki-21-Ic: Larger main wheels.2,6 Better armament.3,5,6 Increased fuel.2,3,5,6 An 110 gallon / 500 liter auxiliary fuel tank could be installed in rear of the bomb bay.6 When installed four 110 lb / 50 kg could be carried externally.6
  • Mitsubishi Ki-21-II, Army Type 97 Heavy Bomber: Had Mitsubishi Ha-101 radial engines (1,500 HP).1,6 Horizontal tail surfaces were larger.2,6 Landing gear fully enclosed.6
  • Mitsubishi Ki-21-IIa, Army Type 97 Heavy Bomber Model SA: Had a hand held 7.7 mm MG in rear dorsal position.1 Dorsal glasshouse replaced turret.2 Engines with more power.3 Landing gear modified.3
  • Mitsubishi Ki-21-IIb, Army Type 97 Heavy Bomber Model 2B: Had 12.7 mm MG in a turret in the dorsal position.1 Dorsal glasshouse replaced turret.2
  • Mitsubishi MC-21: Transport.2,6 Converted from Ki-21-Ia in China.2,6 All military equipment removed.6 Used by Dai Nippon Koku K. K. (Greater Japan Air Lines Co. Ltd).6 Nine soldiers could be carried.6 Some Army commanders used them as personal transports.6

Usage

Used By

  • Sentais: 7th, 12th, 14th, 58th, 60th, 61st, 62nd, 92nd, 95th, and 98th6
  • Dokuritsu Hikotai: 3rd6
  • Hikodan: 22nd6
  • Hikoshidan Shireibu Hikodan: 1st, 5th, 8th6
  • Hamamatsu Army Bomber Flying School6

First Unit

Towards the end of 1939 the 60th Hikosentai (air regiment) was equipped with the Ki-21.5

Arrival in China

The 60th and 61st Sentai went to China with their Ki-21s in August 1938.1,2,6

Pacific War

The Ki-21 was the main bomber in December 1941.2,5 It was used in the Malayan, Thai, Burmese, and Netherlands East Indies campaigns.2,3

Philippines

The 5th Air Group, in Formosa, included the 14th and 62nd Hikosentais.5 They attacked Aparri, Tuguegarao, Vigan, and Luzon on December 8, 1941.5

Indo-China

The 3rd Hikoshidan (Air Division), in Indo-China, including the 12th, 60th, and 98th Hikosentais bombed Siam and Malaya.5,6 There were a total of 87 Ki-21s.6

When faced by P-40s and Hurricanes they suffered many losses.6

Secondary Roles

By 1943 the Ki-21 was obsolete and was moved into secondary rolls.2 These included being a bomber trainer, communication aircraft, and a suicide plane.2,6

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.6

Specifications

  Mitsubishi Ki-21
Type Medium bomber2
Crew 56, 5 - 72
Pilot, co-pilot, bombardier / navigator, radio operator / gunner, gunner6
Engine (Type) 2: Nakajima Ha-5 KAI6
Cylinders Radial 146
Cooling Air6
Net HP 850 each6
Propeller blades 3 metal blade variable pitch6
Dimensions  
Span 73' 9.75"2
22.5 m2
Length 52' 6"2
16 m2
Height 15' 11"2
4.85 m2
Armament 6: 7.7 mm MG2
Normal bomb load 1,653 lb2
750 kg2
Maximum bomb load 2,205 lb2,6
1,000 kg2,6
  Mitsubishi Type 97
Type Long range bomber4
Engine (Type) 2: Mitsubishi Kinsei A-144
Net HP 870 each4
Dimensions  
Span 85'4
Length 61'4
Weight  
Loaded 24,000 lb4
Performance  
Speed 225 mph4
Range 2,500 miles4
Armament  
Front 2: MG4
Ventral 2: MG4
Sides 2: MG4
Tail 1: MG4
Maximum bomb load 4,400 lb4
  Mitsubishi Ki-21-I
Engine (Type) 2: Nakajima Ha-5 Kai2
Cylinders Radial 142
Net HP 1,080 each2
Propeller blades 3 each2
Performance  
Speed @ 13,125' /
4,000 m
268 mph2
431 kph2
Climb 1,150'/minute2
350 m/minute2
Service ceiling 28,215'2
8,600 m2
Range 932 - 1,678 miles2
1,500 - 2,700 km2
  Mitsubishi Ki-21-Ia
Engine (Type) 2: Nakajima Ha-56
Fuel Capacity 580 gallons6
Dimensions  
Span 73' 9 13/16"6
22.5 m6
Length 52' 5 29/32"6
16 m6
Height 14' 3 13/32"6
4.35 m6
Wing area 749.165 sq ft6
69.6 sq m6
Weight  
Empty 10,342 lb2,6
4,691 kg2,6
Loaded 17,452 lb2,6
7,916 kg2,6
Performance  
Speed at 13,125' / 4,000 m 268 mph6
432 kph6
Climb to 16,505' / 5,000 m 13 minutes 55 seconds6
Service Ceiling 28,215'6
8,600 m6
Range - Normal 932 miles6
1,500 km6
Range - Maximum 1,680 miles6
2,700 km6
Armament  
Nose 1: 7.7 mm Type 89 MG6
Ventral 1: 7.7 mm Type 89 MG6
Dorsal 1: 7.7 mm Type 89 MG6
  Mitsubishi Ki-21-Ib
Engine (Type) 2: Nakajima Ha-5 KAI5
Cylinders Radial5
Net HP 850 each5
Armament  
Nose 1: 7.7 mm Type 89 MG6
Dorsal 1: 7.7 mm Type 89 MG6
Ventral 1: 7.7 mm Type 89 MG6
Lateral 2: 7.7 mm Type 89 MG6
Tail 1: 7.7 mm Type 89 MG6
  Mitsubishi Ki-21-Ic
Engine (Type) 2: Nakajima Ha-5 KAI5
Cylinders Radial5
Net HP 850 each5
Armament  
Nose 1: 7.7 mm Type 89 MG6
Ventral 1: 7.7 mm Type 89 MG6
Dorsal 1: 7.7 mm Type 89 MG6
Tail 1: 7.7 mm Type 89 MG6
Beam 2: 7.7 mm Type 89 MG6
  Mitsubishi Ki-21-II
Engine (Type) 2: Mitsubishi Ha-1012,5,6
Cylinders Radial 142,6
Cooling Air6
Net HP 1,500 each2,6
Propeller blades 3 each2, 3 metal blade constant speed6
Performance  
Speed @ 14,485' /
4,720 m
302 mph2
486 kph2
Climb 1,640'/minute2
500 m/minute2
Service ceiling 32,810'2
10,000 m2
Range 1,680 miles2
2,700 km2
  Mitsubishi Ki-21-IIb
Type Bomber1,3, Medium Bomber5
Crew 51,3,5
Engine (Type) 2: Mitsubishi Ha-1011,3
2: Mitsubishi Ha-101 (Army Type 100)5
Cylinders Radial5, Radial 143
Cooling Air3
Net HP 1,500 each1,3
Dimensions  
Span 73' 9"3, 73' 9.75"1,5, 73' 9 13/16"6
22.5 m1,5,6
Length 52' 5 7/8"1, 52' 5 29/32"6, 52' 6"3,5
16 m1,5,6
Height 15' 10 7/8"1, 15' 10 15/16"6, 15' 11"3,5
4.85 m1,5,6
Wing area 749.16 sq ft5, 749.165 sq ft6, 749.2 sq ft1
69.6 sq m1,5,6
Weight  
Empty 13,382 lb1,2,5,6
6,070 kg1,2,5,6
Loaded 21,362 lb3, 23,391 lb1,2,5,6
10,610 kg1,2,5,6
Performance  
Speed at 13,125' / 4,000 m 302 mph1
486 kph1
Speed at 15,485' / 4,720 m 302 mph3,5,6
486 kph5,6
Cruising Speed 236 mph5
380 kph5
Cruising Speed at 16,405' / 5,000 m 236 mph6
380 kph6
Climb to 19,685' / 6,000 m 13 minutes 13 seconds5,6, 13.2 minutes1
Service ceiling 32,810'1,3,5,6
10,000 m1,5,6
Range 1,680 miles1,3,5,6
2,700 km1,5,6
Armament 6: MG3
Beam 2: 7.7 mm Type 895,6
Turret - Dorsal 1: 0.5" / 12.7 mm Type 15,6
Nose 1: 7.7 mm Type 895,6
Tail 1: 7.7 mm Type 895,6
Ventral 1: 7.7 mm Type 895,6
Bombs 2,200 lb3, 2,205 lb5
1,000 kg5

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
20th Century American Military History Crucial Site