Project: Yuri I

The Yuri I project was the second to achieve liftoff and surpassed the Da Vinci III to set the current world record. In 1994, it achieved an altitude of 0.2 m and a time of 19.46 sec with a drift of 9.95 m. Unofficially, it achieved 24 seconds 0.7 m. It was designed and built by a team from the Nihon Aero Student Group (NASG) lead at the time by Dr Akira Naito. This project was followed by Yuri II. Detailed description of the 19.46 sec attempt here. Description of a televised documentary on Dr Naito and the Yuri I and II projects here (Translation). Yuri is a Japanese name meaning "Lilly". One can imagine that the rotor configuration resembles the petals of a flower.

Dr. Patterson on Yuri I

Dr Patterson (leader of the Da Vinci project) wrote in an email his impressions on seeing the Yuri I.

"Date: Thu, 3 Nov 1994 01:19:36 -0700 (PDT) From: [William Patterson] To: "Andrew M. Letton"  Subject: Re: yuri I think this is ok it may have a little junk in it. The interface between my ancient word processor and pine isn't working too well. Bill FLIGHT OF THE YURI In august of this year, Dian and I went to Seattle for a human powered flight symposium. The primary reason was not to gab about our past activities but to be present for Prof. Naito's demonstration flight of the YURI II. Prof. Naito and I have been in communication for several years concerning our efforts to hover under human power. I was overjoyed to hear that he had hovered in 1993 and wanted to be present for his demonstration in Seattle. The YURI has four rotor heads connected by a very sophisticated truss structure and weighs less than 80 lbs. Each rotor blade is 5 meters long. The yuri is a 20 meter square machine with the pilot in the center above the tip path plane of the rotors. The machine lifts off immediately upon the onset of rotor rotation. Flight is absolutely silent and placid. The YURI seems to slip into the air. I was too far from the flight area to feel any rotor wash, but I presume that it was minimal. The whole experience was totally different from flights of the da Vinci. The da Vinci propellers generated a helicoidal vortex that impinged on the rotor blade tips and could be heard by all present. The YURI slips into the air with out fuss and certainly requires much less power for flight. The da Vinci was an untamed beast compared to the YURI. I was not an official observer, but I am confident that the YURI was out of contact with the ground for 24 seconds. It was also able to fly for a shorter time with a female pilot/engine. All I can do is bow in congratulation. I hope the flight of the da Vinci and the YURI spur others into taking up the chase. Technical data. 4 rotor systems 2 blades each. 5 meter radius rotor speed 20 rpm."

Before Yuri 1, the NASG team designed, built and tested many other configurations.


Photos from the 19.46 sec attempt: (New)


Air flow pattern at the blade root.
On page 19 of the IHPVA vol. 11, no. 4, the purpose of the "tent" seen on this photo is explained. It is a deflector meant to add lift. Using small strings to visualize the air flow pattern.
It looks like they are using a motor to test the helicopter.
They achieve a great height.
Close-up view of the motor installation.
Trailing edge and tab.
Using smoke to visualize the air flow pattern.
Yuri I now hangs in the Kakamigahara Aerospace Museum. NEW


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