Principles of Helicopter Flight Book

Foreword     xi
Preface     xii
Physics     1
Newton's Laws     1
Newton's First Law     1
Newton's Second Law     2
Newton's Third Law     3
Conclusion     3
Mathematical Terms     3
Velocity     3
Acceleration     3
Equilibrium     4
Gravitational Forces     4
Centripetal Force     5
Vector Quantities     5
Moments and Couples     6
Moments     6
Couples     6
Energy     6
Pressure Energy     6
Dynamic (Kinetic) Energy     7
Units of Measurement     7
Graphs     8
Review 1     10
The Atmosphere     11
Atmospheric Pressure     11
Air Temperature     11
Combined Effects     12
Moisture Content     12
The Standard Atmosphere (ISA)     12
Pressure Altitude     13
Density Altitude     13
Summary     13
Operational Considerations     14
Review 2     14
Lift     15
Definitions     15
The Lift Formula     18
Dynamic Energy     20
Summary     20
Indicated Airspeed and True Airspeed     21
Center of Pressure     22
Aerodynamic Center     24
Review 3     26
Drag     27
Types of Drag     28
Parasite Drag     28
Profile Drag     29
Form Drag     29
Skin Friction     30
Induced Drag     31
Tip Vortices     33
Effect of Airspeed on Induced Drag     34
Effect of Aspect Ratio     34
Methods to Reduce Induced Drag     35
Wash-out     35
Tip Design     35
Total Drag Curve     36
Conclusion     37
Review 4     38
Lift/Drag Ratio     39
Best (or Maximum) L/D Ratio     40
Other Factors Influencing L/D Ratio     41
Conclusion     41
Review 5     42
Aerodynamic Forces     43
Definitions     43
Rotor Systems     45
Introduction      45
Rotational Airflow (Vr)     46
Blade Angle of Attack     46
Induced Flow     47
Airflow Caused by Aircraft Velocity     48
The Forces     48
Total Rotor Thrust     49
Rotor Drag (Torque)     49
Angle of Attack and the Rotor Thrust/Rotor Drag Ratio     50
Induced Flow and the Rotor Thrust/Rotor Drag Ratio     50
Inflow Angle     51
The Force Opposing Weight     52
Factors Influencing Rotor Thrust     53
Air Density     53
Rotor rpm     54
Blade Angle     54
Disc Area     54
Significant Aspects of High Inertia Blades     55
Conclusion     55
Review 6     56
Rotor Blade Airfoils     57
Drag Factors     57
Stress Factors     58
Effect of Local Air Velocity on Blade Design     59
Blade Tip Speeds     59
Development in Blade Design     60
Review 7     60
Rotor Drag (Torque)     61
Disc Loading Changes     61
Changes in Gross Weight     62
Changes in Altitude      62
Changes in Configuration     62
Ground Effect     62
Translational Lift     64
Summary     65
Review 8     66
The Anti-Torque Rotor     67
Anti-Torque Functions     67
Mechanical Considerations     68
Anti-Torque and Demand for Power     68
Effect of the Wind     69
Translating Tendency (Tail Rotor Drift)     70
Rolling Tendency     71
Tail Rotor Flapping     71
Shrouded Tail Rotors     72
Tail Rotor Design     72
Other Methods of Anti-Torque Control     72
Strakes and Anti-Torque     73
Tail Rotor Failure     74
Review 9     76
Controls and Their Effects     77
Collective Control     77
Cyclic Control     78
Effect of Controls on Blade Lead-Lag Behavior     78
Mean Lag Position     78
The Four Main Causes of Movement about the Lead/Lag Hinge     78
Conservation of Angular Momentum (Coriolis Effect)     78
Hookes Joint Effect     79
Periodic Drag Changes     80
Random Changes      80
Review 10     80
The Hover     81
Hover Our-of Ground Effect (OGE) and In-Ground Effect (IGE)     81
Factors Affecting Ground Effect     82
Helicopter Height Above Ground Level     82
Density Altitude and Gross Weight     82
Gross Weight and Power Required     83
Nature of the Surface     83
Slope     83
Wind Effect     84
Confined Areas - Recirculation     84
Factors Determining the Degree of Recirculation     84
Over-Pitching     85
Review 11     86
Forward Flight     87
Three Basic Aspects of Horizontal Flight     89
Tilting the Disc with Cyclic     89
An Alternate Explanation of Cyclic Action     91
Dissymmetry of Lift     91
Eliminating Dissymmetry of Lift     92
Blow-Back (Flap Back)     94
Blow-back (Flap-Back) When Using Collective     95
Summary     96
Designs that Reduce Flapping Amplitude     96
Delta-3 Hinges     96
Offset Pitch Horns     97
Reverse Flow     98
Translational Lift     99
Transverse Flow Effect     101
Review 12     102
Power, Range and Endurance     103
Power     103
Ancillary Power     103
Profile Power     103
Induced Power     104
Parasite Power     104
The Total Horsepower Required Curve (the HPR)     105
Attitude     106
Weight     107
Slingload and Parasite Drag Items     107
Flying the Helicopter for Range     108
Effect of the Wind     109
Engine Considerations     110
Range Summary     110
Flying the Helicopter for Endurance     111
Endurance Summary     111
Review 13     112
Climbing and Descending     113
Climbing     113
The Horsepower Available Curve (The HPA)     114
Factors Affecting the Horsepower Available Curve     114
Altitude     114
Density Altitude     115
Leaning the Mixture     115
Collective Setting     115
Rate of Climb     115
Angle of Climb     116
Effect of Lowering Horsepower Available Curve     116
Summary      117
Effect of the Wind     117
Climb Performance Summary     118
Descending     118
Angle of Descent     119
Effect of the Wind on Descents     120
Descent Performance Summary     121
Review 14     122
Maneuvers     123
Turning     123
Rate of Turn     124
Radius of Turn     125
Rate and Radius Interaction     125
The Steep Turn     125
Power Requirement     126
The Climbing Turn     127
The Descending Turn     127
Effect of Altitude on Rate of Turn and Radius of Turn     127
Effect of Changes in Gross Weight on Rate and Radius     128
Effect of the Wind on Rate and Radius     128
Effect of the Wind on Indicated Airspeed and Translational Lift     129
Effect of Slingloads     130
Effect of Slipping and Skidding     131
Pull-Out from a Descent     131
Review 15     132
The Flare     133
Initial Action     133
Flare Effects     133
Thrust Reversal     134
Increasing Total Rotor Thrust      134
Increasing Rotor rpm     134
Management of Collective     135
Review 16     136
Retreating Blade Stall     137
Effect of Increasing Airspeed on Stall Angle     137
Factors Affecting the Advancing Blade     138
Symptoms of Retreating Blade Stall     138
Recovery     139
Factors Influencing V[subscript ne]     140
Conclusion     141
Review 17     142
Autorotation     143
Initial Aircraft Reaction     143
The Lift/Drag Ratio and Forces Involved     143
The Stalled Region     144
The Driven (Propeller) Region     145
The Driving (Autorotative) Region     145
Combined Effects of All Regions     146
Autorotation and Airspeed     148
Combined Effect     149
Effect of Forward Speed on the Three Regions     150
Effect of Airspeed Changes on Rotor rpm     150
Autorotation Range and Endurance     150
Effect of Altitude on Range and Endurance     151
Effect of Gross Weight on Range and Endurance     151
Effect of Parasite Drag and Slingloads on Range and Endurance     152
Touchdown      152
Loss of Power at Low Heights     153
Factors Influencing Rotor rpm Decay When the Engine Fails     153
Combination of Airspeed and Height Best Avoided     153
Review 18     156
Hazardous Flight Conditions     157
Vortex Ring State     157
Effect on the Root Section of the Blade     158
Effect on the Tip Section of the Blade     158
Flight Conditions Likely to Lead to Vortex Ring State     160
Symptoms of Vortex Ring State     160
Recovery from Vortex Ring State     161
Tail Rotor Vortex Ring State     161
Ground Resonance     162
Causes of Ground Resonance     162
Factors that May Cause Ground Resonance     163
Rotor Head Vibrations     163
Fuselage Factors     163
Ground Resonance Recovery Action     164
Blade Sailing     164
Dynamic Rollover     165
Factors Influencing the Critical Angle     165
Cyclic Limitations     166
Mast Bumping     167
Avoiding Mast Bumping     169
Recovery from Low and Zero g     169
Mast Bumping Summary     169
Exceeding Rotor rpm Limits     169
Reasons for High Rotor rpm Limits     169
Engine Considerations     169
Blade Attachment Stress     169
Sonic Problems     170
Reasons for Low Rotor rpm Limits     170
Insufficient Centrifugal Force     170
Reduced Tail Rotor Thrust     170
Rotor Stalls     170
Recovery from Low Rotor rpm     171
Review 19     172
Helicopter Design and Components     173
Transmission     173
Main Rotor Gear Box     173
Freewheeling Unit     174
Drive Shafts     174
Tail Rotor Gear Box     174
Rotor Brake     174
Clutch     174
Chip Detectors     175
Governors     175
Swashplate (Control Orbit)     176
Phase Lag     177
Advance Angle     177
Rotor Blades     179
Chordwise Blade Balancing     180
Spanwise Blade Balancing     180
Trim Controls     180
Bias Control     180
Electronic Servo Systems     180
Tail Rotors     181
Tail Rotor Flapping      181
Tail Rotor Rotation     181
Helicopter Vibrations     181
Types of Vibrations     182
Vertical Vibrations     182
Lateral Vibrations     183
Combined Vertical and Lateral Vibrations     183
High Frequency Vibrations     183
Engine Vibrations     184
Remedial Action by the Pilot     184
Control Functions     184
Collective     184
Twist Grip Throttle     184
Engine Cooling     185
Carburetor Icing     185
Dual Tachometer Instruments     186
Rotor Stabilizing Design Systems     187
The Bell Stabilizing Bar     187
The Hiller System     187
The Underslung Rotor System     188
Rotorless Anti-Torque System     189
Advantages of the Notar System     189
Components     189
Air Intake     190
Engine-driven Fan     190
Slots     190
Direct Jet Thruster     191
Vertical Stabilizers     191
Undercarriages     192
Skids     192
Wheels     192
Oleo (Shock) Struts     193
Review 20     195
Stability     195
Static Stability     195
Dynamic Stability     195
Stability in the Three Planes of Movement     196
Longitudinal Stability     197
Longitudinal Stability Aids     197
Lateral Stability     198
Directional Stability     199
Directional Stability Aids     200
Cross Coupling with Lateral Stability     200
Offset Flapping Hinges     200
Review 21     202
Special Helicopter Techniques     203
Crosswind Factors     203
Lateral Blow-back (Flap-back)     203
Weathervane Action     203
Effect on tail Rotor Thrust     203
Different Types of Takeoffs and Landings     204
Downwind Takeoffs and Landings     204
Running Takeoff     204
Cushion-Creep Takeoff     205
Confined Area Takeoff (Towering Takeoff)     205
Maximum Performance Takeoff     206
Running Landing     206
The Zero-Speed Landing     207
Operations on Sloping Surfaces     207
Sling Operations      208
The Equipment     208
The Sling     210
Ground Handling     211
Flying Techniques     212
Snagging of Cable or Strap on the Undercarriage before Liftoff     212
Never-Exceed Speed (V[subscript ne])     213
Preflight Rigging     213
Length of Cable or Strap     213
Number and Type of Slings     213
Nets     213
Pallets     214
Load Center of Gravity     214
Pilot Action in Case of Helicopter Oscillation     214
The Approach     215
Types of Slingload     215
Horizontal Loads     215
Unusual Loads     216
Conclusion     219
Review 22     220
Mountain Flying     221
Updrafts and Downdrafts     221
Thermal Currents     223
Katabatic and Anabatic Winds     224
Mechanical Turbulence     224
Wind Strength     225
Size and Shape of Mountains     226
Stability or Instability of Air     226
Wind Direction Relative to Mountain Orientation     227
Summary     227
Valley Flying      227
Ridgeline Flying     228
The "Standard" Mountain Approach     228
General Coinments on Mountain Approaches     230
High Attitude Approach Considerations     230
Transition     232
Ground Effect Considerations on Mountain Sites     232
Determining Wind Change during Critical Phases     233
Landing Site Selection     233
Surface of Sites     233
Flight in Areas Covered in Snow and Ice     234
Survival Equipment     235
Review 23     236
Helicopter Icing     237
Ice Accretion     237
Influence of Temperature and Drop Size     237
Water Content of Air     238
Kinetic Heating     238
Shape of Airfoils and Other Aircraft Components     238
Mechanical Flexion and Vibration     239
Ice Formation on Blades at Different Temperatures     239
Electrical Anti-Icing     240
Consequences of Ice Accretion     240
Engine Intake Icing     241
Review 24     242
Helicopter Performance     243
Helicopter Performance Factors     243
Altitude     243
Pressure Altitude      244
Density Altitude     246
Combined Effect of Pressure and Density Altitude     247
Moisture Content of Air     248
Aircraft Gross Weight     248
External Stores     248
The Wind     249
Power Check     249
Performance Graphs     250
Units of Measurement     251
Hover Ceiling Graph     252
Takeoff Distance over a 50-Foot Obstacle     254
Turbine Engine Power Check     256
Maximum Gross Weight for Hovering     258
Climb Performance     260
Range     261
Endurance     262
Review 25     263
Weight and Balance     265
Definitions     265
Weight     267
Balance     267
Beyond the Center of Gravity Limits     268
Excessive Forward Center of Gravity     268
Excessive Aft Center of Gravity     269
Summary     269
Calculating the Center of Gravity Position     269
To Calculate the Longitudinal Center of Gravity Position     271
To Calculate the Lateral Takeoff Center of Gravity Position     271
Summary      273
Effect of External Loads on Center of Gravity Position     273
Conclusion     274
Review 26     274
Sample Examination     277
Temperature Conversion     287
Altimeter Setting Conversion     289
Review and Examination Answers     291
Glossary     295
Index     299