The Sikorsky R-4 was the first helicopter used in U.S. combat operations. At a time when vertical flight was still experimental, it was deployed into real wartime conditions. Limited range, fragile ...

Add Yahoo as a preferred source to see more of our stories on Google. Image Credit: James K. F. Dung - Public Domain/Wiki Commons. From the jungles of Vietnam to the deserts of Iraq, helicopters have ...