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"A New-Type Japanese Medium Bomber" from Tactical and Technical Trends

The following report on a new Japanese twin-engine bomber variant originally appeared in Tactical and Technical Trends, No. 25, May 20, 1943. The bomber is identified as an improved version of the Mitsubishi Ki-21 "Sally" bomber.

[DISCLAIMER: The following text is taken from the U.S. War Department publication Tactical and Technical Trends. As with all wartime intelligence information, data may be incomplete or inaccurate. No attempt has been made to update or correct the text. Any views or opinions expressed do not necessarily represent those of the website.]


A new Japanese twin-engine, medium bomber has been reported recently shot down in India. It is believed to be designated as Type 97 Mark II; manufactured by Mitsubishi, an improved version of the Type 97 twin-engine bomber, "Sally", re-engined and with improved armament, carrying a crew of seven.

The span of this new bomber, given as 74 ft. 10 in., is a little greater than the Type 97. The length of 48 feet is slightly less. It is a mid-wing monoplane with engines centrally slung, the nacelles being slightly longer under the wing to house the backward-retracting oleo-legs. It has a single fin and rudder. The main plane is of boxspar construction, with the trailing edge tapered more than the leading edge and with a small dihedral angle. It is of stressed skin metal construction, with the exception of the control surfaces, which are of the conventional metal frame construction, fabric-covered. There are split trailing edge flaps 14 ft. 4 in. long and 2 ft. 7 in. wide, starting at the fuselage with ailerons directly outboard of these in two sections and reaching almost to the wing tips. It has a perspex nose and a turret on top of the fuselage towards the tail.

Name plates on the engines state that they are the Mitsubishi Type 100, with 1,450 hp. This engine, apparently an improvement on the Kinsei engine in the Type 97, is a 14-cylinder, twin-row, air-cooled radial 52 inches in diameter, with a deep reduction-gear casing, and probably fitted with a two-speed supercharger, giving a superficial resemblance to the Wright Double Cyclone. The propellers are the three-blade metal type, with electrical pitch-changing mechanism operated by a motor on the forward end of the boss and enclosed in the spinner.

The armament in the new aircraft is reported to be considerably heavier than hitherto encountered in any Japanese bomber, although no armor is apparently provided.

A 7.7-mm Lewis-type machine gun is gimbal-mounted in the nose within an eccentric ring, in the same manner as in the He-111. Similar German influence is apparent in the design of the dorsal turret, which is like that of the Do-217E-2, except that the Japanese version is manually operated in both traverse and elevation. A Browning-type 12.7-mm machine gun is mounted on the inner side of a rotatable annular turret ring. For firing, the gunner stands at the side and aims by means of a reflector sight very similar to but smaller than the German "Revi." An emergency ring-and-bead sight is also fitted. Elevation and depression are effected by a hand crank, at the end of which is the firing button. Estimated maximum depression is 30° and elevation 80°, with an all-around traverse.

The lateral guns are two 7.7-mm Lewis-type machine guns. The one on the port side is mounted on a bracket and can be swung across an opening which also serves as a door to the fuselage. The starboard gun, in a cylindrical socket mounting in the middle of the bottom side, traverses a smaller aperture directly opposite.

The ventral gun, a 7.7-mm machine gun for rear use only, is fired through a hole formed by opening two doors in the bottom of the fuselage. Both doors have footsteps in the center, the forward half of each having a perspex window with two protection bars. There are two similar windows on each side of the fuselage, permitting a view to port and starboard. Forward of these are three perspex panels half-way up the fuselage side. A red push button on the starboard side of the fuselage floor near the gun is presumably connected up to some warning device (horn?) in the pilot's cockpit.

A 7.7-mm Vickers-type machine gun is mounted in the tail on a free-traversing bracket, the elevation and depression of which is controlled by another bracket attached to the forward end of the gun barrel. Both brackets are connected by link mechanisms to rods running down both sides of the fuselage. These, in turn, are coupled to a curved arm carrying a pistol grip which is operated by the gunner standing in the turret. Coupled in the linkage is a ring-and-bead sight, which protrudes through two holes in the turret, and movement of the pistol grip controls the gun and the sight. The maximum movement appears to be 10 degrees in any direction, giving a cone of fire with a 20-degree angle. On the control arm are two "T" handles connected by Bowden cable to the cocking handle and to the stoppage clearing handle, respectively. The gun is fired by a trigger mechanism in the arm, connected by Bowden cable to the front sear on the gun.

The bomb bay in this new bomber, measuring approximately 15 ft. by 3 ft. and being 18 in. deep, is believed to carry a maximum load of 2,500 to 3,000 pounds. This load is an improvement on that of any known Japanese bomber. The bombs appear to be mounted alternately, nose-to-tail.

Five fuel and two oil tanks were traced. The oil tanks were in the leading edge, and the name plate gave a capacity of about 38 U.S. gals. Both of these latter tanks had self-sealing coverings which formed the actual outside skin of the wing. Two fuel tanks are situated in each wing root, and a third in the fuselage over the bomb bay. The total capacity is about 687 gals.

When carrying a load of 1,100 pounds, it is estimated that the airplane has a maximum speed of 285 mph at 13,000 feet, a service ceiling (with normal load) of 30,000 feet, and a cruising range of 950 miles. With 2,750 pounds of bombs the economical range is 1,300 miles.


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