This book covers vertical-rising aircraft as envisioned from the earliest concepts to the period when the helicopter became a practical machine in the late 1930s. It focuses on the many pioneering ideas and efforts that led to the creation of today's modern helicopter and it explores possibilities for the future. Inside are over 200 illustrations and an encyclopedic glossary that enables the reader to understand the development of the technology and procedures. It is intended for professionals, students, and the increasing body of aviation enthusiasts and conservators.