The power requirements measured in static thrust and in level forward flight are presented for two helicopter rotor configurations. One is a coaxial rotor arrangement having the rotors spaced approximately 19 percent of the rotor radius; the other is a tandem configuration in which the rotor-shaft spacing is 3 percent greater than the rotor daimater and in which the rotors lie in the same plane. The experimental meausrements are compared with the results of calculations based on existing NACA single-rotor theory.

Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.