Table of Contents Preface.....................................................................v Acknowledgments................................................vii Introduction to the Helicopter ............................1-1 Introduction....................................................................1-1 Turbine Age ...................................................................1-2 Uses................................................................................1-3 Rotor System..................................................................1-3 Rotor Configurations..................................................1-4 Tandem Rotor ........................................................1-4 Coaxial Rotors .......................................................1-4 Intermeshing Rotors................................................1-4 Tail Rotor ...................................................................1-5 Controlling Flight...........................................................1-5 Cyclic ........................................................................1-5 Collective ...................................................................1-5 Antitorque Pedals .......................................................1-6 Throttle ......................................................................1-6 Flight Conditions ...........................................................1-6 Chapter Summary ..........................................................1-7 Relative Wind.............................................................2-9 Rotational Relative Wind (Tip-Path Plane)................2-9 Resultant Relative Wind...........................................2-11 Induced Flow (Downwash) ..................................2-11 Rotor Blade Angles ..................................................2-12 Angle of Incidence................................................2-12 Angle of Attack.....................................................2-13 Powered Flight .............................................................2-14 Hovering Flight............................................................2-14 Translating Tendency (Drift)....................................2-15 Pendular Action........................................................2-15 Coning ......................................................................2-16 Coriolis Effect (Law of Conservation of Angular  Momentum) .............................................................2-16 Gyroscopic Precession .............................................2-17 Vertical Flight ..............................................................2-17 Forward Flight .............................................................2-17 Airflow in Forward Flight .......................................2-19 Advancing Blade .................................................2-19 Retreating Blade ..................................................2-19 Dissymmetry of Lift .............................................2-20 Translational Lift......................................................2-21 Effective Translational Lift (ETL)........................2-22 Translational Thrust..............................................2-22 Induced Flow............................................................2-23 Transverse Flow Effect ............................................2-23 Sideward Flight............................................................2-23 Rearward Flight ...........................................................2-24 Turning Flight ..............................................................2-24 Autorotation .................................................................2-25 Vertical Autorotation................................................2-25 Autorotation (Forward Flight)..................................2-26 Chapter Summary ........................................................2-26 Aerodynamics of Flight.......................................2-1 Introduction....................................................................2-1 Forces Acting on the Aircraft ........................................2-2 Lift ..............................................................................2-3 Bernoulli’s Principle...............................................2-3 Venturi Flow...........................................................2-4 Newton’s Third Law of Motion..............................2-5 Weight ........................................................................2-5 Thrust .........................................................................2-6 Drag ............................................................................2-6 Profile Drag ............................................................2-6 Induced Drag ..........................................................2-7 Parasite Drag...........................................................2-7 Total Drag ...............................................................2-7 Airfoil ............................................................................2-7 Airfoil Terminology and Definitions .........................2-7 Airfoil Types ..............................................................2-8 Symmetrical Airfoil ................................................2-8 Nonsymmetrical Airfoil (Cambered)......................2-8 Blade Twist ...............................................................2-9 Rotor Blade and Hub Definitions ...........................2-9 Airflow and Reactions in the Rotor Disk.......................2-9 Helicopter Flight Controls ..................................3-1 Introduction....................................................................3-1 Collective Pitch Control.................................................3-2 Throttle Control .............................................................3-2 Governor/Correlator ......................................................3-2 Cyclic Pitch Control.......................................................3-3 Antitorque Pedals...........................................................3-4 Heading Control .........................................................3-4 Chapter Summary ..........................................................3-5 Chapter 3 Chapter 2 Chapter 1 ix