Medium Bomber Mitsubishi

The first prototype Ki-21 flew on December 18, 1936. The Ki-21 was a midwing plane with X-6 Kinsei (Gold Star) engines with Hamilton Standard three-blade variable pitch propellers. The three-spar wing had a working light alloy skin and was divided into three sections. The ailerons were made of light alloy with fabric sheathing. Hydraulically extendable flaps are all metal. The semi-monocoque fuselage with a working skin had an oval cross-section. The bomb bay was located under the spars of the center section, and above them were two gas tanks, shifted to the left side (there was a passage to the tail section on the right). The plumage had a metal structure with linen sheathing. The first and second pilot-navigator were located side by side, the bombardier was in the bow, the gunner-radio operator was in the tail. Defensive armament consisted of three 7.7-mm Type-89 machine guns. One was in the bow turret with firing angles only in the vertical plane, the second was in the rear turret, and the third was in the lower hatch. The chassis was retracted and released hydraulically.

The first production Ki-21-1a did not look different from the third prototype. The engines Ha-5 - "army type 97" with a capacity of 950 liters were chosen as the power plant. with. at 2400 rpm at sea level and 1080 hp. with. at an altitude of 4000 m. The fuel supply was increased from 1840 liters to 2635 liters. Defensive armament consisted of three 7.7 mm machine guns.

Type 97 Model I Bombers of Hamamatsu Army Flying School

Modifications

• Ki-21-I - the first serial modification, produced from November 1937 to February 1941 at the Mitsubishi plant in Nagoya (423 aircraft built) and under license at the Nakajima plant in Ota (341 aircraft). All bombers of this modification externally practically did not differ from the third prototype, they were equipped with the same engines - Nakajima Na-5 with a capacity of 1080 hp. with., but had an increased from 1840 to 2635 liters of fuel. The first version was the Ki-21-Ia with three 7.7-mm Type 89 machine guns in the bow, upper and lower firing points. It was replaced by the Ki-21-Ib, which was distinguished by enhanced defensive armament (two 7.7-mm machine guns were added - one in the fuselage for firing from the side windows, the second in the tail remote-controlled installation). Flaps and horizontal tail of an increased area were used. In addition, the volume of the bomb bay increased, and the gas tanks were partially rubber-lined. The last option was the Ki-21-Iс. These bombers were armed with an additional machine gun located in the side window. Reinforced landing gear with wheels of larger diameter were used. A fuel tank with a capacity of 500 liters could be installed in the rear bomb bay (when using it, four 50-kg bombs were located on the external suspension nodes). After decommissioning, a number of Ki-21-Ia bombers were converted into transport aircraft, which were used by both the Air Force and the Greater Japan Airlines - under the designation MC 21.
• Ki-21-II is the second serial modification, developed taking into account the experience of combat use of Ki-21-I aircraft in China. The new cars were equipped with engines of the Mitsubishi Na-101 with a capacity of 1500 hp. sec., which made it possible to significantly improve flight characteristics (for example, the maximum speed at an altitude of 4400 m increased to 478 km / h, and the ceiling - to 10,000 m). Flight tests of the prototype began in March 1940, and in December four production vehicles were presented for military tests. If the 590 bombers of the first version of the Ki-21-IIa differed from the Ki-21-Ic, apart from the new power plant, it is very insignificant.
• Ki-21-IIb (until September 1944, when production of the Ki-21 was discontinued, 688 units were built) differed from its predecessors by installing on them instead of a canopy gunner, limiting the angle of fire from the upper machine gun, a large spherical tower with one 12 , 7-mm machine gun Type 1. In addition, starting with 275 copies, the armor protection of the pilot and the turret gunner was used in the form of steel plates 16 mm and 12.5 mm thick.

The baptism of fire of the Ki-21 bombers took place in China, where they showed their best side. The results of the use of aircraft of this type during the battle at Khalkhin Gol were also positive. This is not surprising, since the Ki-21 by the time it entered service in 1938 was undoubtedly an outstanding, albeit not devoid of flaws, aircraft.

The experience of combat use made it possible to identify the main flaws of the bomber, namely, weak defensive weapons and insufficient protection of fuel tanks and crew members' jobs. Trying to eliminate the shortcomings, the designers of "Mitsubishi" developed a modification of the Ki-21-II. These aircraft met the beginning of the Second World War in the Pacific Ocean in the rank of the best bombers of the Japanese Army Air Force, and at the first stage achieved good results, bombing targets in the Philippines, Burma and Malaya. Thus, accompanied by Ki-27 and Ki-43 Nakajima fighters, Ki-21 bombers destroyed the bases of the British and Australian Royal Air Force in Agora Setari, Sungai Petani and Butterworth. Despite the fact that the Ki-21s were very popular among the troops for their good controllability and ease of maintenance, they quickly became obsolete. Even the modernized aircraft were highly vulnerable to the fire of anti-aircraft artillery and enemy fighters, which, moreover, were improved and became more and more numerous. However, despite the decline in combat qualities, the Japanese continued to use the rapidly aging Ki-21, since the Ki-49 bombers they created to replace Nakajima turned out to be difficult to control and had a small combat load. Only after the launch of the Ki-67 bomber in the series at the beginning of 1944, the Ki-21 began to be transferred from the units of the first line to training and transport units. In the last months of the war, many of the surviving vehicles were used as kamikaze planes.

Photo	Description
	Drawing Ki-21-IIb
	Ki-21-Ic

Bibliography

• "Encyclopedia of military engineering " /Aerospace Publising/
• "Japan Warplanes of World War II" /Oleg Doroshkevich/