Mitsubishi Ki.167
Among all medium bombers used by the IJA, the Ki.67-I was the most suitable to make
Tokko attacks. It was a fast and manoeuvrable airplane that achieved some successes against the US ships at Formosa and Ryukyu Island. It also made conventional attacks against the B-29s bases located in the Marianas, operating from Iwo Jima.
In January 1943, one Ki.67-I was modified to carry the IJN standard aerial torpedo Type 91 Model II of 450 mm. After conducting several tests with good results, hundred units of this aircraft were manufactured for the IJN and IJA. The naval version, named
Yasukuni, was equipped with Type H-6 radar and Yagi antennas.
In the autumn of 1944, a joint IJA / IJN unit of Ki.67s torpedo planes was formed, integrated by 7th and 98th Sentais and 762nd Kokutai, operating from Formosa under naval control. The first suicide attack of the
Peggy took place on January 6, 1945 when four planes of the 501st Special Attack Squadron, from the 7th Sentai, attacked a US carrier Task Force east of Taiwan. On the 24th, ten aircraft of the
Sichisei Kojun Unit conducted suicide attacks using torpedoes against a British carrier Task Force off Sumatra.
On March 30, a torpedo-plane of the Shinbu Special Attack Unit
Kanegawa made a
Tokko attack on Allied ships off Okinawa Island. On April 25, four suicide
Peggys of the 110th Sentai attacked Allied ships south-west of Kadena. On May 24, a Ki.67-I of the 60th Sentai acted as a guide plane of the
Giretsu airborne unit, integrated by twelve Ki.21 bombers. On 19 June, eight torpedo-planes of the
Sichisei Jinrai Unit conducted a
Tokko attack against British ships off Balikpapan. Six days later, in the same area, the
Sichisei repeated the attack.
By mid-July, the First Air Arsenal at Tachikawa received orders to modify several Ki.67-I in a similar way to the
Mukade variant of the P1Y1
Ginga, in order to make long range
Giretsu strafing attacks against the bases of the B-29 located in Saipan. The
Giretsu suicide missions were considered one-way only because of its long range and the absence of escort fighters. The modification consisted of installing four remote-controlled 20 mm cannons, with 300 rounds each in the bomb bay, angled 30 degrees downwards to be fired towards the ground, and flexible mounts for other four cannons in the nose and tail turrets.
After the end of the war, the first aircraft had been modified by 60 percent and Mitsubishi was working on a 2,500 km. long-range variant with additional fuel tanks in the fuselage and droppable fuel tanks under the wings. In July 1944, the IJA started the
To-Go programme, a series of modifications to adapt its fleet of bombers to the new strategy of suicide attacks already started by the IJN. That same month, the 1st Army Air Arsenal at Tachikawa commissioned the transformation of twelve Ki.48 aircraft into the suicide version of the Ki.48-II-KAI-Otsu equipped with bombs of 850 kg.
In August, the modifying of some Ki.49 into the suicidal variant of the Ki.49-II-KAI was started. Two 850 kg bombs were also installed inside the Ki.67, a modification that was the origin of the Ki.67-I-KAI version. To that purpose, it was necessary to eliminate much of the internal equipment and armament, replacing the nose and tail turrets with plywood aerodynamic fairings and reducing the crew to three men. The anti-ship bombs used by the IJA in 1944 were Type 3, No. 80, Mark 8 with an actual weight of 850 kg that were considered more effective than the naval model of 807.5 kg that equipped most of the suicide planes. For the
To-Go missions, the Type 3 bombs were modified by replacing the tail fuse with another electrically powered by means of an extended probe located in the nose airplane.
In total, 32
To-Go aircraft were modified and conducted suicide attacks against Allied ships between November 7, 1944 and April 25, 1945, operating with the special attacks units
Fugaku and
Tokko sections of the 62nd and 110th Sentais. In late 1944, the IJA concluded that the Ki.48s and Ki.49s equipped with conventional bombs were not effective in suicide attacks. The antiship bombs designed to pierce the heavy armoured decks of capital ships did not contain enough amount of HE Type 98 to cause serious damage, as they were located inside an aircraft that impacted at a relatively slow speed, compared to what could be achieved when the bombs dropped from a great height.
Another modification, made at least to one Ki.67, involved the installation of a large load of HE in the nose cone, that was electrically detonated by an extended probe. But the device did not turn out to be destructive enough during the flying tests. In late 1943 the Luftwaffe completed the testing of a new secret bomb named SHL-3500, a huge hollow charge 2 m in diameter containing 1,700 kg of HE. When exploding against a hard target generated a 4,000 degrees Celsius jet of molten metal from liner travelling at over twenty times the speed of sound. The jet could drill a hole through more than 8 m of armoured steel or 20 m of reinforced concrete.
The SHL-3500 bombs were designed to be carried in
Mistel configuration by a specially modified Junkers Ju 88 and the Germans were manufacturing the SHL-6000 version, 3.9 m in diameter, to adapt it to the He 177 Heinkel in 1945. The Japanese acquired the hollow chargers technology in October 1942 and by mid-1944 had already developed their version of 1.6 m diameter of the SHL bomb, called
Sakura-Dan. During the tests performed in Pai-Chengzi, Manchuria, the bomb was able to penetrate up 25 m in the simulated structure of a battleship.
With 2,900 kg,
Sakura-Dan was too heavy to be installed in the nose of a medium bomber and it was decided to modify the central section of the fuselage of a Ki.67 to place it on the centre of gravity of the aircraft, angled at 15 degrees downwards. Five aircraft were thus modified under the designation Ki.167 with an extended probe of 2 m which contained three electrical crush fuses, with selection in flight, based on the German model EI.AZ(45) A.
At least two Ki.167s were used in combat by the 62nd Sentai. On April 2, 1945, the s /n 5033 along with a Ki.67
To-Go and six Ki.84 escort fighters participated in an attack on Allied ships east of Kikai Island. On May 25, the s /n 5027 accompanied three other
To-Go and some Ki.84 in a new attack west of Naha. In a report published by the U.S.A.A.F. in 1946, a smaller version called
Sakura-2 is described that had 1.12 m of diameter and a weight of 1,300 kg and had been designed to be installed on the nose of the
To-Go bombers. The usual stand-off probe is not represented in the drawings so it is unknown what would have been the trigger mechanism. Some sources suggest a derivative from the Type 3 photoelectric influence fuse.