US ARMY YO-3A secret most silent Airplane for Night Observation & Designation, Vietnam 1970-71 -1/3 (Later operated by FBI & NASA)
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Presentation By Kurt Olney
crew chief on the YO-3A during the Vietnam War,
QUIET AIRCRAFT ASSOCIATION http://www.yo-3a.com/ QT-2PC & Y0-3A

On a still night, the Lockheed Y0-3A Quiet Star, flying at 1000 feet, was inaudible from the ground. This quiet night-flying spy plane collected intelligence in Vietnam until late 1971 and then was used by the FBI in crime surveillance and by NASA for sonic noise measurements.

Its stealth was achieved by a very slow-turning propeller and highly quieted exhaust, together with other sound deadening techniques. An advanced electro-optical sensor permitted the Quiet Star to detect a person one mile away in faint moonlight. The sensor operator sat in front, the pilot in the rear seat. Lockheed secretly built eleven of these aircraft in a Menlo Park, California, industrial park, using many components of a Schweizer glider to expedite development.

Presentation held at the Hiller Aviation Museum San Carlos CA http://hiller.org/ Sept..15, 2012

Lockheed YO-3 "Quiet Star" http://en.wikipedia.org/wiki/Lockheed_YO-3
http://en.wikipedia.org/wiki/Schweizer_X-26_Frigate

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CIMG0517 US ARMY YO-3A the secret most silent Airplane -1.MOV