Hiryu Projects

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Graeme

Graeme

1st Sergeant
4,615
2,816
May 31, 2007
Part one. (Anti-shipping missile carrier)

The Japanese I-Go-1-Ko Radio controlled anti-shipping missile. Intended to be carried by a Ki-109 carrier aircraft-ten were built but never saw operational use. Weighed 3,086lb with a 1,764lb warhead and powered by a Tokuro rocket providing 529lb of thrust for 75 seconds it was expected to attain a speed of 342 mph. The rocket fired 1.5 seconds after launch. Tests were conducted over a range on Lake Biwa, near Koyto, with targets being rock formations on the edge of the Lake. Good results justified further production, but by this stage the war was lost.


 
The Ki-67-I-KAI or To-Go Hiryu was essentially a 'manned missile'. It was a straightforward adaptation of the bomber version with a long rod projecting from the nose to serve as an impact trigger for the warload. The To-Go Hiryu was intended to carry two 1,764 lb bombs, one internally and one externally, all unnecessary equipment being removed, and the blister and tail gun positions-and the dorsal turret on some aircraft-being replaced by plywood fairings. Fifteen Hiryus were converted to To-Go configuration by Kawasaki and others by the Tachikawa concern, and these were issued to "special attack" units formed by several Hiryu-equipped Sentais.




Some of the first To-Go Hiryus were hurriedly assigned to the Philippines for special operation by a "special attack" unit formed by the 74th Sentai, but these were damaged on the ground by the allied air attack, and discovered by a TAIU on Lingayen airfield, Luzon, on 9 January 1945. The first operational use of the To-Go Hiryu was apparently made by the "special attack" unit of the 7th Sentai formed in February 1945 initially with six instructors from the Hamamatsu Flying School led by one Maj Nishio. Known as the Fugaku Special Attack Corps after the prestigious Mt Fuji emblem carried by the Sentai, the To-Go Hiryus of this unit participated, in concert with other Kamikaze aircraft, in damaging attacks on the US carrier force of the 5th Fleet mid-March in the course of which the USS Franklin was do badly crippled that it had to be towed away by a cruiser, and the Yorktown and Wasp were severely damaged, although all three vessels were saved. The very nature of the operations, of course, prevented successes being ascribed to the individual units and thus the achievements or otherwise of the To-Go Hiryus of the Fugaku Special Attack Corps were to remain unknown.

The To-Go Hiryus were also assigned to "special attack" units formed by the 62nd and 98th Sentais, and these were used to participate in the desperate operations against the Allied forces engaged in invading the Ryukus in general and Okinawa in particular, the Allied landings commencing on 1April. The To-Go Hiryus joined with other Kamikaze aircraft in Operation Ten-Go, a co-ordinated air-naval suicide attack mounted 6-7 April in which six US ships were sunk and 24 others damaged. During 12-13 April, the suicide strikes were resumed in force, 21 US ships being sunk, 43 more being put permanently out of action and a further 23 being put temporarily out of action.

 
The Ki-167 was a Hiryu version specifically adapted to accommodate the so-called Sakuradan thermite bomb. The Sakuradan bomb installed in the Ki-167 was an unconventional 6,393-lb weapon, shaped somewhat like a pressure cooker with a diameter of 5 ft 3 in and the base facing forward and angled downward some 15 deg, demanded some structural modifications of the fuselage. The bomb was placed on the aircraft CG and its diameter necessitated the cutting away of some of the upper fuselage structure, the protruding portion being enclosed by a plywood fairing reminiscent of a camels hump. The rear casing of the charge was parabolic and 19.7 in thick in order to direct the blast forward.



The Sakuradan was based on a weapon developed in Germany in WWII, the plans for which were taken to Japan aboard the submarine I-30 in October 1942, and testing was conducted in the strictest secrecy at Pai-Chengzi in Manchuria. During these trials it was ascertained that the fierce flame generated by the weapon projected some 3,280 ft ahead of the point of detonation and at a distance of 985 ft from impact a medium tank could be totally destroyed. With insertion of the Sakuradan in the Hiryu, the starboard controls were deleted, the crew being reduced to pilot, engineer, navigator and radio operators, and all gun positions were faired over.



The first two Sakuradan-equipped Ki-167s were completed in February 1945, and after flight testing at Kagamigahara, these were delivered to the "special attack" unit of the 62nd Sentai at Tachiarai, to where the unit had transferred from Nishi Tsukuba. This unit also possessed several To-Go Hiryus, and the first mission with a single Sakuradan-equipped aircraft was flown from Kanoya, Kyushu, on 17 April, in concert with two To-Go Hiryus. The Ki-167 was piloted by Lt Kozaburo Kato and its target, as was that of the accompanying To-Go Hiryus, was the Allied carriers and other naval vessels off Okinawa.

The three aircraft took-off at intervals between 0715 and 0726 hours, successfully eluding interception by F6F hellcats SE of Tokunsoshima Island at about 0950 hours.
At 1010 hours, Lt Kato broke radio silence with the message: "Have found a carrier. Am attacking!" Shortly after this, Cdt Maemura, who was flying as navigator in one of the To-Go Hiryus, saw flame streaming back from the Sakuradan equipped aircraft, the nose of which suddenly pulled up sharply as it disappeared into cloud, and it was assumed that the Ki-167 was mortally hit before it could commence its attack on the target that Lt Kato had reported.

A second "special attack" unit was formed by the 62nd Sentai with two more Sakurandan equipped Ki-167s and two To-Go Hiryus, flying its first mission on 27 May from Kanoya against Allied naval forces west of Okinawa. Both Ki-167s disappeared after signalling that they were attacking targets and both To-Go Hiryus returned to base when they failed to find suitable targets. The "special attack" units of the 62nd Sentai were the only recipients of the Ki-167s, comparatively few of which were completed, at least one of these being destroyed in an accident and another as a result of sabotage. It is recorded that a unit equipped with Ki-167s under the command of Maj Isamu Katano was formed in June 1945, and was scheduled to leave Japan for an attack on Saipan on 16August, the day after official ceasefire, yet no example of the Sakuradan equipped aircraft was found by the Allies after the occupation.

 
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Heres a boneyard of the To Go Ki - 67. Note the long fuzing rod.
Poor Hiryu get rid of all usable parts.

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Graeme. I am a Japanee TV Producer making a public TV documentary on Sakuradan. We are interviewing survivors of two Tokko missions utilizing Sakuradan. I am impressed by your detailed descriptions. Are they based on Japanese documents? For the documentary we are looking for the relics, artifacts , photos and US Military documentations on the captured Hiryu, or any records of tokko attack by Sakuradan. I know it is extremely hard to locate the trace of this bomber but could you or anyone be suggest where we could search for the above issues.
 
hideo nakamura said:
I am impressed by your detailed descriptions. Are they based on Japanese documents?
Click to expand...

Sorry Hideo, it was early days on the Forum and I was experimenting with typing, uploading images, scanning, re-sizing and generally playing with the 'buttons and switches.'

You'll find it all came from Air International July 1983 or look for the bound Air International Volume Twenty Five.
 
Graeme said:
Sorry Hideo, it was early days on the Forum and I was experimenting with typing, uploading images, scanning, re-sizing and generally playing with the 'buttons and switches.'

You'll find it all came from Air International July 1983 or look for the bound Air International Volume Twenty Five.
Click to expand...

Graeme,

Thanks to your suggestions.
I got a copy of the article from NYPublic Library.
It seems like they relyed on Bunrindo version when they wrote it. It is the most concise information so far on Hiryu.
Hideo::)
 
Graeme, do you happen to have any more information on the first missile posted? Whether it was guided, attack profile etc.

Thanks
 
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