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Mitsubishi Ki-21 (Sally) Medium Bomber Aircraft

The Mitsubishi Ki-21 medium bomber started operational service in 1939 and lasted into the final months of the war, by then relegated to suicide kamikaze attacks.

 Updated: 11/30/2016; Authored By Staff Writer; Content ¬©

The Mitsubishi Ki-21 (codenamed "Sally" by the Allies) was a successful medium bomber in service with the Japanese Air Force since 1939, seeing combat action up until 1945 despite the fact that the aircraft was already outclassed by the crop of American and English airplanes in the theater. Nevertheless, the Ki-21 proved a success since its inception and would become even more lethal when in use as kamikaze aircraft. While an adequate aircraft in its own right, the Ki-21 suffered form the same major drawbacks inherent in most of the Japanese designs of World War 2 - inadequate defensive armament and armor protection for the crew.

Externally, the Ki-21 was a clean design, sharing some layout similarities to its American counterparts the B-25 Mitchell and the B-26 Marauder. The system yielded two engines on a mid-mount monoplane wing assembly. The cockpit was fitted just forward of the wing root providing the pilot a decent view of the engines to either side of him. The nose featured a green-house type glass arrangement with more small windows positioned to look downward than upward. A dorsal turret was fitted just past the wings with a single vertical tail surface adorning the empennage. Armament on early models consisted of a few 7.7mm machine guns though this would be upgraded to several more in later models including a heavy caliber 12.7mm type in the later Ki-21-II model series. Single instances of guns were positioned in the nose, dorsal turret, a ventral position and two beam positions. Beyond that an internal bomb load capacity of 2,205 pounds was afforded. Crew accommodations amounted to five personnel.

The Ki-21 was initially drawn up by the Mitsubishi corporation to an Imperial Japanese Army Air Force requirement appearing in 1936 with prototypes airborne by the end of that year. Despite this quick development, the system would have to wait till te end of 1939 to be fielded en mass thanks to delays along the production front. By then, the Ki-21 was already being fielded in China and elsewhere after that. Initial combat reports signaled the deficiencies in the design - primarily with armor and armament - and, as such, the system appeared in a "b" and "c" variant class to address this. Despite this effort, the initial production line of Ki-21's was already wholly obsolete and a newer version known as the Ki-21-II appeared with Mitsubishi-brand 1,500 radial engines in place of the original Nakajima types. This new model series spawned into an "a" and "b" variant model which differed mostly in armament - the latter showcasing Type 1 12.7mm (.50 caliber) machine gun in a pedal-operated dorsal turret.

The Ki-21 found many an initial success in the early years of the war in the Pacific, thanks in part to a solid design and to the general unprepared nature of the Allies. By the end of the war, operation of the Ki-21 was limited to the macabre delivery of kamikaze units to which the potent internal payload was put to extensively lethal use. The Ki-21 was to be superceded in production by the newer Nakajima Ki-49 Donryu "Helen", though that aircraft in itself was a general disappointment.

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Mitsubishi Ki-21-IIb (Sally) Technical Specifications

Service Year: 1939
Type: Medium Bomber Aircraft
National Origin: Imperial Japan
Manufacturer(s): Mitsubishi - Japan
Production Total: 2,064

Structural (Crew Space, Dimensions and Weights)

Operating Crew (Typical): 5
Overall Length: 52.49 feet (16 meters)
Overall Width: 73.82 feet (22.50 meters)
Overall Height: 15.91 feet (4.85 meters)

Weight (Empty): 13,382 lb (6,070 kg)
Weight (MTOW): 23,391 lb (10,610 kg)

Installed Power and Standard Day Performance

Propulsion: 2 x Mitsubishi Ha-101 radial piston engines developing 1,500 horsepower each.

Maximum Speed: 302 mph (486 kph; 262 knots)
Maximum Range: 1,678 miles (2,700 km)
Service Ceiling: 32,808 feet (10,000 meters; 6.21 miles)
Rate-of-Climb: 1,499 feet-per-minute (457 m/min)

Armament / Mission Payload

1 x 12.7mm Type 1 machine gun in dorsal turret
1 x 7.7mm Type 89 machine gun in nose
1 x 7.7mm Type 89 machine gun in tail gun position
1 x 7.7mm Type 89 machine gun in in ventral gun station
1 x 7.7mm Type 89 machine gun in left beam station
1 x 7.7mm Type 89 machine gun in right beam station

Up to 2,205lbs of internal ordnance.

Global Operators / Customers

Imperial Japan

Model Variants (Including Prototypes)

Ki-21 - Base Series Designation; codenamed "Sally" by the Allies.
Ki-21-Ia - Initial Production Model; fitted with 2 x Nakajima Ha-5 KAI radial engines.
Ki-21-Ib - Ki-21-Ia Sub-variant; redesigned bomb bay doors; improved defensive armament; improved armor protection; increased fuel capacity.
Ki-21-Ic - Ki-21-Ia Sub-variant; redesigned bomb bay doors; improved defensive armament; improved armor protection; increased fuel capacity.
Ki-21-II - Fitted with Mitsubishi Ha-101 engines of 1,500 horsepower; redesigned engine cowlings.
Ki-21-IIa - Ki-21-II Variant
Ki-21-IIb - Ki-21-II Variant; featured pedal-operated dorsal turret; 1 x 12.7mm machine gun fitted to dorsal gun turret position.
Army Type 97 Heavy Bomber - Official Ki-21 Series Designation.
Army Type 97 Heavy Bomber Model 1A - Official Ki-21-Ia Designation.
Army Type 97 Heavy Bomber Model 1B - Official Ki-21-Ib Designation.
Army Type 97 Heavy Bomber Model 1C - Official Ki-21-Ic Designation.
Army Type 97 Heavy Bomber Model 2A - Official Ki-21-IIa Designation.
Army Type 97 Heavy Bomber Model 2B - Official Ki-27-IIb Designation.