Rear view of a Ki-67-I being refuelled.

The three prototypes were not completed until December 1942, February 1943, and March 1943, respectively, but Mitsubishi had already been instructed to build additional prototypes and service-test machines. All three prototypes were armed similarly-one 7.92mm machine gun in each of the nose, port, and starboard beam positions, and one 12.7mm gun in dorsal and tail turrets. The first prototype left the earth on its maiden flight on December 27, 1942. It displayed some longitudinal instability and control oversensitivity under certain flight conditions, but overall, the Mitsubishi team and the Army were pleased with the new creation. Although the maximum speed was eight miles per hour slower than the specification called for, the Ki-67 easily met or exceeded every other requirement. Once the service-test machines were modified to improve their handling characteristics, the type was discovered to be both easy to fly and amazingly manoeuvrable. Without a bombload of any kind, the Hiryu could easily loop and turn tightly, and its controls remained smooth and effective even in dives of up to 373 mph. In addition to increased fuel capacity from 565 gallons to 855 gallons-and the extra tanks were self-sealing, no less-the service test examples had a revised armament. The nose gun was changed to a 12.7mm weapon, the dorsal turret’s gun became a 20mm cannon, and the beam positions became “blisters” rather than flush-mounted windows.

In December 1942, it was suggested that the new aircraft would make an excellent land-based torpedo bomber, and in January of the following year, Mitsubishi was instructed to fit an underbelly torpedo rack on 100 production Hiryus. The 17th and 18th production Ki-67s were used to test the plane’s suitability for this demanding role, and Major Sakamoto of the Army’s Air Examination Department took the two planes and their Army crewmen to the Yokosuka Naval Air Station for trials. The Hiryu proved so successful that Mitsubishi was directed to install torpedo racks on all Ki-67s beginning with the 161st aircraft, and the Army agreed to release some Hiryus for Naval service. The JNAF renamed them the Yasukuni, after the shrine near Tokyo devoted to honoured war dead.

The Army, in fact, was so pleased with the new bomber, that additional equipment was being continually planned for it, and actual adoption of the Ki-67 for service was delayed because no one apparently could agree on a standardized configuration for it. Finally, the Army Air Staff was forced by the demands of the war to quit dithering. The design was frozen on December 2, 1943, after one last change was made-the beam guns were changed to 12.7mm weapons-and it was formally accepted as the Army Type 4 Heavy Bomber Model 1 Hiryu (Ki-67-I).

Close-up of the experimental I-Go-IA anti-shipping missile slung under a Ki-67's belly.

The foolish delay in finalizing the design meant that the first combat use of the Peggy didn’t occur until the series of air-sea battles off the Formosan coast in October 1944. The Army’s 7th and 98th Sentais and the Navy’s 762nd Kokutai (Air Group) scored some hits on the American cruisers Houston and Canberra, but failed to sink either vessel (they were towed out of the battle zone), and all three units suffered heavy losses. But from then on, torpedo-carrying Ki-67s of both services fought side-by-side for the remainder of the war, being particularly active in opposing the American landings on Okinawa. In its original bomber role, the Hiryu was used by the JAAF over China, and Hamamatsu-based Ki-67s, staging through Iwo Jima, made repeated attacks on B-29 bases in the Marianas until Iwo was invaded.

Production of the Ki-67-I received the highest-priority rating, but only 698 were built. The parent company, Mitsubishi, built 606 at three different factories; Kawasaki built 91; and the Tachikawa Army Air Arsenal built one. Also, Nippon International Air Industries performed the final assembly of 29 Mitsubishi-built examples. Only one more major change was made: the single 12.7mm machine gun in the tail turret was replaced by a twin-gun mount starting with the 451st example. It was also planned to increase the bombload to 2,756 pounds beginning with the 751st aircraft, but Allied bombings and the December 1944 earthquake, which especially affected engine production, seriously impaired production of this and every other Japanese aircraft.

Naval personnel loading a torpedo under a Ki-67.

By the end of the war, several special or experimental versions of the Ki-67 were planned, but only one was actually built-the Ki-109 heavy fighter, described separately. Others that reached the drawing board, and in some cases prototype form, included the following:


Ha-104 Ru powered Ki-67: The 21st and 22nd Hiryus were modified to test the turbo supercharged engines intended for the Ki-109.

Ki-67-II: This was a projected version to be powered by two 2,400-hp Ha-214s; the 16th and 17th machines were used as test-beds for this engine.

Ki-67 glider tug: A standard Ki67-I was used to tow the Manazuru (Crane) transport glider in tests.

Ki-67-I-KAI: A special suicide-attack version, modified by the Tachikawa Arsenal. All turrets were removed and faired over, the crew reduced to just three, and a long rod protruded from the airplane’s nose, to set off on impact either two standard 1,764-lb. bombs or a special explosive charge weighing 6,393 pounds. Apparently, some of these were built and used operationally, but there is no record of their success, or lack of it.

I-Go-1A carrier: One Ki-67-I was modified to carry a single I-Go-1A radio-controlled anti-shipping missile under its fuselage.

Ki-69: Proposed escort-fighter version; not proceeded with.

Ki-97: Proposed transport version, marrying the wings, tail surfaces, engines and undercarriage of the Ki-67 to a new fuselage intended to carry 21 passengers; not proceeded with.

Ki-112: Projected multi-seat fighter version; not proceeded with.

A torpedo-carrying Ki-67 taxis out for a mission.