There can be no doubt that the US Department of Defense has already conducted a thorough study of this scenario. But that's classified.
Fortunately, experts at the Smithsonian Channel have weighed in, analyzing the strengths and vulnerabilities of both dragons and the Boeing AH-64 Apache helicopter.
Who would win? Both have a chance of victory. The outcome would depend upon luck and the tactics used by the combatants.
-via The Mary Sue