Leonardo da Vinci is often applauded as a great scientist, in addition to being a great artist. He was a Renaissance man in every sense of the word.
But a scientist? Not in a strict sense. He dabbled, but he generally (if ever) did not draw firm conclusions, as a true scientist would. His methodology was more observational than anything else.
Oh, and please don't call him "da Vinci." That's not his name. "Da Vinci" is Italian for "from Vinci," and simply denoted where he was from. Check out any encyclopedia and you'll see that they refer to him as "Leonardo." So do art historians. Anyone who calls him "da Vinci" is simply speaking out of ignorance.
Curse you, Dan Brown, for perpetuating that bit of misinformation (along with the many other falsehoods recorded in your book)!