* Renaissance genius observed flight basics by watching birds
* Digitized version of "codex" is on Mars rover Curiosity
By Deborah Zabarenko
WASHINGTON, Sept 12 (Reuters) - More than five centuries after he scribbled in the pages of a well-worn pocket notebook, Leonardo da Vinci's seminal document detailing how humans might emulate the flight of birds has landed at the Smithsonian National Air and Space Museum.
Steps from the Wright Brothers' 1903 Flyer in a shaded corner of the vast museum on Washington's Mall, da Vinci's "Codex on the Flight of Birds" goes on display on Friday for about six weeks.
Created by the Italian Renaissance visionary between 1505 and 1506, at the same time he was painting the "Mona Lisa," the codex contains the essentials of aeronautics, gleaned from da Vinci's observations of kite birds wheeling overhead.
The 18 pages of the notebook are written in the artist's idiosyncratic backwards mirror script and include drawings of the joints in bird wings, along with the ideas of lift and drag, air flow and gravity.
"When the bird beats its wings and waits to gain height, it raises the shoulders and beats the tips of the wings towards itself, thus condensing the air that stands between the tips of his wings and its chest," da Vinci wrote on one page, according to an English translation. "This makes the bird rise upward."
To aeronautical experts, the da Vinci codex on bird flight seems to have almost mystical powers.
Charles Elachi, director of NASA's Jet Propulsion Laboratory, said his heart started beating a bit faster when he was allowed to turn the pages of the codex during a 2011 visit to its home at Italy's Biblioteca Reale di Torino, or Royal Library of Turin. The codex is on loan from the library.
"I was so hesitant about going through the pages, but it is amazing, the things that Leonardo thought when he was drawing on this thing 500 years ago," Elachi said during a media preview of the Washington exhibit. "And basically that's the foundation of how we do flights."
Elachi wore gloves to avoid damaging the fragile notebook. In its Washington display, the document is in a sealed case and no photographs are permitted. But there are computer screens where visitors can turn the pages of a digital version of the codex, showing da Vinci's script and drawings on one side, facing the English translation on the other.
The 8-by-6-inch (20-by-15-cm) codex has traveled to the United States only once before, in 2008, and rarely leaves Italy, the museum said.
The notebook also includes some philosophical musings on lying, drawings of a leaf and the muscles in a human leg, and even a shopping list.
The codex has traveled to France, Siberia, Britain and back to Italy. A digitally scanned version of it is now on the Mars rover Curiosity, which landed on the red planet in August 2012.
One of da Vinci's ideas from the codex was to have leather bags filled with water to cushion any fall from flight by a human pilot. Elachi pointed out that this system is not far from the air bags that cushioned earlier rovers' landing on the Martian surface.
"Just imagine, 500 years ago, where he had no tools, no mathematical equations that we have now, no wind tunnels," Elachi said. "He basically was able, just by observation, to come up with a lot of the theories of what we do now."
More information and images from the exhibit are available at http://airandspace.si/edu/exhibitions/codex/ (Reporting by Deborah Zabarenko; Editing by Patricia Reaney and Eric Walsh)