This is a photo of the “Tokushu Choban Re-Go” built in 1944. The name is actually the abbreviation of “Tokushu Choutugai-Shiki Renshi 1 Go” which literally translates as “Special Hinged Rotor Machine No.1″.

It was designed by Professor Masato Hirotsu of the Yokohama Advanced Industrial School (present Yokohama University), who was involved in the development of tethered helicopters (i.e. serves same function as observation balloons) at Kayaba. Prof. Hirotsu started his work on this helicopter in 1942. He is said to have been inspired of the twin rotor design by the Fw61, but thought of placing the rotors in-line instead of the side by side as in the Focke Wulf design. Incidentally, Piasecki also started work on the PV-3 twin rotor design at around the same time.

His idea won Imperial Japanese Army interest and under IJA funding, the helicopter was built at his school. In June 1944, the Re-Go was completed, and in the first taxiing test, it succeeded in lifting its tail with a slight forward motion with Prof. Hirotsu in the cockpit. In the following lift test with the Re-Go fixed to the ground, it was proven that it created enough lift to hover the 500kg helicopter.

Unfortunately, Re-Go’s first flight came unexpectedly with an unfortunate ending. While pending the first flight, a curious student secretly got into the cockpit and started the motor. The Re-Go hovered a foot or so, but before the student could end his little adventure and put it back on the ground, a sudden side wind turned the Re-Go on its left side.

Prof. Hirotsu started building an improved second prototype, but the fall of Marianas and the Philippines and the consequent B-29 raids forced the project to an end.

Source: Monthly Maru article by Goro Suzuki.