Engineering Design Handbook - Helicopter Engineering, Part One - Preliminary Design:

380 Pages·24.231 MB·English

AMC PAMPHLET AMCP 706-201
ENGINEERING DESIGN
HANDBOOK
HELICOPTER ENGINEERING
PART ONE
PRELIMINARY DESIGN
HEADQUARTERS, U.S. ARMY MATERIEL COMMAND AUGUST 1974
AMCP 706-201
LIST OF ILLUSTRATIONS
Fig. No. Title Page
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Fig. 2-1 Helicopter as a Subsystem ............................. 2-2
Fig. 2-2 Configuration Composition .................... 2-4
Fig. 2-3 Contribution of Operational Factors to Mission Effectiveness .......... 2-4
Fig. 2-4 Trade-offs in Reliability and Maintainability (AMCP 706-13 4) ............. 2-6
Fig. 2-5 Illustration of System Complexity ..................................... 2-6
Fig. 2-6 Failure Rate History During Operating Lifetime of Items .......... 2-7
Fig. 2-7 Reliability as a Function of Complexity ......................... 2-7
Fig. 2-8 Trends in Helicopter Cruise Speeds ............................ 2-1 1
Fig. 2-9 Trend of Structural Weights for Helicopters ..................... 2-1 1
Fig. 2-10 Representative Mission Profile, Heavy-lift Helicopter ..................... 2-12
Fig. 2-1 1 Cost and Effectiveness for Various Designs . ... .......... 2-14
Fig. 2-12 Typical Curvilinear CER ............................................. 2-17
Fig. 2-13 Scatter Diagrams for Three Test CERs ............................ 2-19
Fig. 2-14 Selected CER With Trend Line and Confidence Bands .................... 2-19
Fig. 2-15 Logic Flow Diagram for Design Trade-off Model ........................ 2-2 1
Fig. 3-1 Typical Mean Drag and Lift Coefficients ............................... 3- 4
Fig. 3-2 Disk Loading vs Power Loading ...................................... 3-5
Fig. 3-3 Moments and Forces of a Hovering Rotor .............................. 3-6
Fig. 3-4 Vortex Pattern Beneath Hovering Rotor ................................ 3-7
Fig. 3-5 Vortex Pattern ..................................................... 3-7
Fig. 3-6 NACA 0012 Airfoil Lift Coefficient ................................... 3-8
Fig. 3-7 NACA 0012 Airfoil Drag Coefficient .................................. 3-8
Fig. 3-8 Maximum Figure of Merit ......... ............................. 3-9
Fig. 3-9 Figure of Merit Ratio for M, = 0.55 ........... .............. 3-9
Fig. 3-10 Figure of Merit Ratio for M, = 0.60 .................................. 3-10
Fig. 3-1 1 Figure of Merit Ratio for M, = 0.65 .................................. 3-10
Fig. 3-12 Blade Twist Correction - Baseline: 8, = -8 deg ....................... 3-10
Fig. 3-13 Blade Root Cutout Correction - Baseline: 20% Cutout .................. 3-10
Fig. 3-14 Replacement of Rotor and Ground by Cylindrical Vortex and Image Vortex . 3-1 1
Fig. 3-15 Knight and Hefner Ground Effect Correction ........................... 3-12
Fig. 3-16 Vertical Drag ...................................................... 3-14
Fig. 3-17 Sample Net Vertical Drag Calculation for Compound Helicopter ........... 3-15
Fig. 3-18 Wake Profile, Out-of-ground Effect, Isolated Rotor ....................... 3-16
Fig. 3-19 Wake Profile, Out-of-ground Effect, With Aircraft (Estimated) ............. 3-16
Fig. 3-20 Formats for Total Efficiency .......................................... 3-16
Fig. 3-21 Calculation of Resultant Velocity V ' in Forward Flight ................... 3-16
Fig. 3-22 Wald's Equation .................................................... 3-17
Fig. 3-23 Effect of Reversed Flow ............................................. 3-18
Fig. 3-24 Basic Flow Chart for Numerical Method ............................... 3-22
Fig. 3-25 Typical Charts for Estimating Performance ............................. 3-23
Fig. 3-26 Airframe Effects, Effect of Fuselage Pitch and Yaw ...................... 3-24
Fig. 3-27 Velocity Components ................................................ 3-24
Fig. 3-28 Projected Disk Area, Overlapping Rotors ............................... 3-25
Fig. 3-29 Hovering Induced Power Correction Due to Overlap ..................... 3-25
Fig. 3-30 Tandem-rotor Interference Factors ..................................... 3-26
Fig. 3-31 Retreating Tip Angle of Attack ....................................... 3-21
Fig. 3-32 Tip SpeedZimitations for Operation at Constant Mach Number ............ 3-29
Fig. 3-33 Maximum Thrust Coefficient/Solidity for Steady Flight ................... 3-30
Fig. 3-34 Effect of Airfoil Thickness Ratio on Limit Airfoil Section Characteristics .... 3-3 1
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AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No. Title Page
Fig . 3-35 Effect of Collective Pitch on Power and Oscillatory Loads ................. 3-34
Fig . 3-36 Component Power at Two Values of Collective Pitch ................. 3-35
Fig . 3-37 Installation of Electrically Powered Model .............................. 3-38
Fig . 3-38 Installation of Hydraulically Powered Model ............... 3-39
Fig . 3-39 Typical Results for Model Without Rotor .............................. 3-41
Fig . 3-40 Typical Rotor Results from a Wind Tunnel Test ......................... 3-42
Fig . 3-41 Arrangement of Download Facility . .................. 3-43
Fig . 3-42 Engine Weight vs Shaft Horsepower ................................... 3-43
Fig . 3-43 Engine Specific Fuel Consumption vs Shaft Horsepower .................... 3-43
Fig . 3-44 Gas Turbine Engine Cycle (Generalized) ........................ .. 3-44
Fig . 3-45 Effect of Gas Turbine Cycle Parameters Upon Specific Fuel Consumption ... 3- 44
Fig . 3-46 Effect of Gas Turbine Cycle Parameters Upon Specific Power .............. 3-45
Fig . 3-47 Gas Turbine Engine Cycle Process-Ideal and Real ......... 3-46
Fig . 3-48 Effects of Leakage Upon Specific Fuel Consumption ...................... 3-47
Fig . 3-49 Variation of Specific Fuel Consumption With Shaft Horsepower (Typical) 3-48
Fig . 3-50 Variation of Cycle Parameters With Partial Power Operation (Typical) ...... 3-49
Fig . 3-51 Pressure Jet Transfer Efficiency as a Function of Cycle Losses ........ 3-51
Fig . 3-52 Cutaway of a Typical Turboshaft Engine (T53L-13) ...................... 3-53
Fig . 3-53 Helicopter Turboshaft Engines ........................................ 3-54
Fig . 3-54 Modifications to the Basic Gas Turbine Engine Cycle ................ 3-55
Fig . 3-55 Effect of Turbine Inlet Temperature on Turbine Cooling Air Requirement 3-56
Fig . 3-56 Schematic Diagram of a Simple Gas Turbine ...... 3-59
Fig . 3-57 Plan View of Rotor in Flight ............ ................ 3-60
Fig . 3-58 Fully Articulated Rotor With Central Flappi ................ 3-61
Fig . 3-59 Fully Articulated Rotor With Offset Flapping Hinge ..................... 3-61
Fig . 3-60 Photograph of Fully Articulated Rotor With Separated Hinges ............. 3-62
Fig . 3-61 Schemstic of Fully Articulated Hub With Coincident Hinges .............. 3-62
Fig . 3-62 Photograph of Fully Articulated Rotor With Coincident Hinges ............ 3-63
Fig . 3-63 Schematic of Two-bladed Semirigid Rotor .............................. 3-63
Fig . 3-64 Photograph of Two-bladed Semirigid Rotor ............................. 3-64
Fig . 3-65 Floating Hub Rotor ................................................. 3-64
Fig . 3-66 Modern Hingeless Rotor ........................................ 3-65
Fig . 3-67 Tilt of Rotor Thrust Vector .......................................... 3-65
Fig . 3-68 Rotation of Blade Inzrement. Plan View ................................ 3-66
Fig . 3-69 Rotation of Blade Increment. Rear View ............................... 3-66
Fig . 3-70 Side View Showing Coning Angle of a Hovering Rotor ................... 3-68
Fig . 3-71 Maximum Integrated Design Lift Coefficient To Avoid Compressibility Losses 3-75
Fig . 3-72 Optimum Efficiency Chart for a Three-bladed Propeller ................... 3-76
Fig . 3-73 Hamilton Standard Propeller Efficiency Chart for a Three.bladed. 100 Activity
Factor. 0.3 Integrated Design Lift Coefficient Propeller .................. 3-77
Fig . 3-74 Advance Ratio Equal Zero Portion of Generalized Torque and Thrust Charts 3-78
Fig . 3-75 Effect of Activity Factor on Torque Coefficient .......................... 3-78
Fig . 3-76 Effect of Integrated Design Lift Coefficient on Torque Coefficient. J \< 1 ... 3-79
Fig . 3-77 Effect of Integrated Design Lift Coefficient on Torque Coefficient. J 2 1 ... 3-79
Fig . 3-78 Variation of Percentage of Camber Correction Required for Torque and Thrust
With Advance Ratio and Blade Angle ................................ 3-80
Fig . 3-79 Variation of Advance Ratio With Blade Angle at Constant Effective Torque
Coefficient ........................................................ 3-81
Fig . 3-80 Variation of Advance Ratio With Effective Thrust Coefficient at Constant Blade
Angle ........................................................... 3-82
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AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No . Title Page
. .
Fig . 3-81 Effect of Integrated Design Lift Coefficient on Thrust Coefficient ........... 3-83
Fig . 3-82 Effect of Activity Factor on Thrust Coefficient .......................... 3-84
Fig . 3-83 Variations of Shrouded Propeller Performance as Influenced by Shroud Drag . 3-85
Fig . 3-84 Dimensions of the Experimental Duct for Ducted Propeller Tests ........... 3-86
Fig . 3-85 Performance Data for the Ducted Propeller Overall Efficiency at Different
Propeller Pitch Angles .............................................. 3-86
Fig . 3-86 Flow Separation on the Lower Part of the Entrance Lip of the Propeller Duct 3-87
Fig . 3-87 Flow Separation on the Upper Part of the Entrance Lip of the Propeller Duct 3-87
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Fig 3-88 Schematic Diagrams Illustrating Component Arrangements in Turbofan Engines
(AMCP 706-285) .................................................. 3-88
Fig . 3-89 Comparison of Performance for Turboprop and Turbofan Engines .......... 3-89
Fig . 3-90 Thrust Specific Fuel Consumption (TSFC) for Turboprop. Turbofan. and Turbojet
Engines as a Function of Flight Speed ................................ 3-89
Fig . 3-91 Sample Configuration of a Convertible Fan/Shaft Engine .................. 3-89
Fig . 3-92 Ideal Augmentation Provided by Water/Alcohol Injection for a Turboshaft En-
gine ..................................................... 3-89
Fig . 3-93 Helicopter Preliminary Design Study ................................... 3-91
Fig . 3-94 Mission-specified Constraint .......................................... 3-92
Fig . 3-95 Altitude Dependence of Turbine Engine Power .......................... 3-93
Fig . 3-96 Temperature Dependence of Turbine Engine Power ...................... 3-94
Fig . 3-97 Gas Turbine Specific Fuel Consumption ................................ 3-94
Fig . 3-98 Induced Power Correction ........................................... 3-95
Fig . 3-99 Tandem-rotor Geometry ............................................. 3-96
Fig . 3-100 Hover Power Loading at Altitude ..................................... 3-97
Fig . 3-10] Sea Level Power Loading ............................................ 3-98
Fig . 3-102 Rotor Figure of Merit ............................................... 3-98
Fig . 3-103 Maximum Rotor Figure of Merit ...................................... 3-98
Fig . 3-104 Power Required in Forward Flight .................................... 3-99
Fig . 3-105 Climb Power Determination .......................................... 3-99
Fig . 3-106 Fuel Flow in Hover ................................................. 3-100
Fig . 3-107 Fuel Required in Forward Flight ...................................... 3-101
Fig . 3-108 Available Fuel Weight Ratio ......................................... 3-102
Fig . 3-109 Required Fuel Weight Ratio .......................................... 3-103
Fig . 3-110 Configuration Selection .............................................. 3-103
Fig . 3-1 1 1 Main Rotor Radius ................................................. 3-104
Fig . 3-112 Minimum Cost Configurations ........................................ 3-104
Fig . 3-1 13 Cost-effectiveness Optimization ........................................ 3-105
Fig . 3-1 14 Typical Mission Profile .............................................. 3-105
Fig . 3-1 15 Hover Ceiling ...................................................... 3-106
Fig . 3-1 16 Hover Ceiling Calculation Procedure ................................... 3-108
Fig . 3-117 Aircraft Hover Power Development .................................... 3-109
Fig . 3-1 18 Payload-range Capability ............................................. 3-109
Fig . 3-119 Engine Fuel Flow Characteristics (Typical) ............................. 3-1 10
Fig . 3-120 Hover Fuel Calculation .............................................. 3-1 11
Fig . 3-121 Time. Distance. and Fuel To Climb from Sea Level ....................... 3-1 11
Fig . 3-122 Helicopter Speed Capability .......................................... 3-1 11
Fig . 3-123 Specific Range Performance ............................ ........... 3-1 12
Fig . 3-124 Range Index Curve . ........ ........................... 3-1 12
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AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No . Title Page
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Fig . 3-125 Payload-range Calculation Chart ...................................... 3-1 14
Fig . 3-126 Specific Range Performance .......................................... 3-1 15
Fig . 3-127 Payload-range Capability ............................................. 3-1 15
Fig . 3-128 Optimum Specific Range Performance ................................. 3-1 15
Fig . 3-129 Elements Required for Specific Range Computation ...................... 3-1 16
Fig . 3-130 Specific-range/Gross-weight Schedule .................................. 3-1 19
Fig . 3-131 Range Index Method ................................................ 3-120
Fig . 3-132 Effect of Altitude and Gross Weight on Range .......................... 3-121
Fig . 3-133 Effect of Wind on Range Capability ................................... 3-122
Fig . 3-134 Ferry Range Mission ................................................ 3- 124
Fig . 3-135 Generalized Range Parameter ......................................... 3- 125
Fig . 3-136 Generalized Helicopter Performance ................................... 3-126
Fig . 3-137 Elements Required To Compute Endurance ............................. 3- 128
Fig . 3-138 Effect of Gross Weight and Altitude on Endurance ....................... 3- 129
Fig . 3-139 Level Flight Power Required ......................................... 3- 130
Fig . 3-140 Climb Capability ................................................... 3-131
Fig . 3-141 Forward Climb Capability-Graphical Format .......................... 3-132
Fig . 3-142 Minimum Level Flight Power Required ................................ 3-133
Fig . 3-143 Application of Rotor/Power Maps to Climb Performance ................. 3-134
Fig . 3-144 Maximum Forward Rate of Climb Determination ........................ 3-135
Fig . 3-145 Service and Combat Ceiling Capability ................................. 3-136
Fig . 3-146 Ceiling Capability Calculation ........................................ 3-137
Fig . 3-147 Vertical Climb Performance .......................................... 3-138
Fig . 3-148 Determination of Vertical Climb Capability ............................. 3-139
Fig . 3-149 Takeoff Profile .................................................. 3-139
Fig . 3-150 Height-velocity Profile ............................................... 3-140
Fig . 3-151 Power Requirements for Takeoff ...................................... 3-141
Fig . 3-152 Landing Profile ...................................... ............ 3-142
Fig . 3-153 Development of Takeoff Level Acceleration Capability .................... 3-142
Fig . 3-1 54 Takeoff Performance .Acc eleration Phase ............................. 3-143
Fig . 3-155 Development of Takeoff Performance Climb Capability ................... 3-144
Fig . 3-156 Takeoff Performance .Clim b Phase .................................. 3-145
Fig . 3-157 Development of Approach Rate of Descent ....... ... 3- 146
Fig . 3-158 Landing Performance .App roach Phase .............................. 3-147
Fig . 3-1 59 Determination of Landing Deceleration Capability .................... 3-148
Fig . 3-160 Landing Performance .Dec eleration Phase ...... 3-149
Fig . 3-161 Typical Altitude-speed Limits ................. 3- 149
Fig . 3-162 Relationship Between True and Equivalent Airspee 3-149
Fig . 3-163 Typical Altitude-velocity Diagram ..................................... 3-149
Fig . 3-164 Typical Structural Altitude-speed Constraints ............................ 3- 150
Fig . 3-165 Altitude Constraints Imposed by Main Rotor Control Limits and Tail Rotor
Adequacy ........................................................
Fig . 3-166 Typical Vibration Characteristics ......................................
Fig . 3-167 Fuselage Pitch Attitude ...............
Fig . 3-168 Basic Mechanism of Autorotation .............................
Fig . 3-169 Rotor Speed Decay Following Power Failure .............
Fig . 3-170 Nondimensional Velocities in Vertical Autorotation ......................
Fig . 3-171 Forces on Helicopter in Autorotation ....................
Fig . 3-172 Rate of Descent in Aut orot a tioti ..................
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AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No. Title Page
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Fig . 3-173 Maximum Rotor Capability .......................................... 3- 157
Fig . 3-174 Idealized Flare Maneuver ............................... ..... 3-157
Fig . 3-175 Conditions for Autorotation End of Cyclic Flare ...................... 3-158
Fig . 3-176 Generalized Nondimensional Height-velocity Curve for Single-engine Helicopters 3-159
Fig . 3-177 High Hover Height ................................................. 3- 159
Fig . 3-178 Critical Velocity .................................................... 3-159
Fig . 3-179 Height-velocity Curve for UH-I ....................................... 3- 160
Fig . 3-180 Height-velocity Curve for CH-47B ..................................... 3- 160
Fig . 3-181 Typical Rotor Thrust Capability .............................. 3- 162
Fig . 3-182 Analytical Model for Maximum Rotor Thrust .................. ...... 3- 163
Fig . 3-183 Analytical Aerodynamic Maximum Thrust .............................. 3- 163
Fig . 3-184 Power Required Characteristic in Steady-state Forward Flight ............. 3- 166
Fig . 3-185 Specific Fuel Consumption vs Engine Power .................... .... 3- 166
Fig . 3-186 Effect of Engine/Rotor Rpm on Power ................................. 3- 166
.
Fig 3-187 Variation of Fuel Flow With Engine Rpm ................... ........ 3- 167
Fig . 3-188 Maximum Range Management Variables ............................... 3- 167
Fig . 3-189 Flight Path Profiles for Takeoff Procedures ............................. 3-168
Fig . 3-190 Influence of Takeoff Procedure on Operating Weight and Field Size ........ 3- 168
Fig . 3-191 Landing Profile ..................................................... 3-169
Fig . 3-192 Continued Flight and Rejected Takeoff Diagram ......................... 3-171
Fig . 3-193 Outputs-Continued Flight After Engine Malfunction .................... 3-171
Fig . 3-194 Outputs-Rejected Takeoff After Engine Malfunction .................... 3- 172
Fig . 3-195 Determination of Matched CDPs for the Continued Flight and Rejected Takeoff
Cases ............................................................ 3- 172
Fig . 3-196 Balked Landing and Landing Diagram ................................. 3- 173
Fig . 3-197 Landing Decision Point (LDP) Characteristic With Vertical and Horizontal Ap-
proach Speed ..................................................... 3-173
Fig . 3-198 Primary Iteration for Impact Velocity With Height-collective Flare ......... 3-174
Fig . 3-199 Determination of Matched LDPs for the Landing and Balked Landing Cases . 3-174
Fig . 3-200 Weight /Twin-engine Torque (TEQ) Relationship ........................ 3-175
Fig . 3-201 Moments Acting on Aircraft While in Sideslip Trimmed Flight ............ 3- 175
Fig . 4-1 Positive Sign and Vector Conventions for Forces Acting on the Helicopter . 4-3
Fig . 4-2 Resolution of Weight and Drag in Trimmed Flight ....................... 4-4
Fig . 4-3 Moments Resulting From Control Stick Movement ....................... 4-4
Fig . 4-4 Escort Mission Profile ............................................... 4-7
Fig . 4-5 Reconnaissance Mission Profile ....................................... 4-8
Fig . 4-6 Frequency of Occurrence of Load Factors ....................... 4-10
Fig . 4-7 Derived Gust Velocity Encounter Distribution .................... 4-10
Fig . 4-8 Typical V-n Diagrams Showing Flight Maneuvers ........................ 4-13
Fig . 4-9 Level Flight Forces ................................................. 4-14
Fig . 4-10 Pullup Maneuver ................................................... 4-15
Fig . 4-1 1 Maximum Load Factor vs Rotor Speed (Hypothetical But Typical Rotor) ... 4-15
Fig . 4-12 Typical Maneuver-Time Spectrum .................................... 4-15
Fig . 4-13 Gust Load Factor vs Helicopter Forward Velocity ....................... 4-16
Fig . 4-14 Considerations Affecting Design Limit Sinking Speed ..................... 4-19
Fig . 4-15 Effects of Pilot’s Location Upon Sinking Speed at Touchdown ............. 4-20
Fig . 4-16 Landing Attitudes. Tricycle Gear ...................................... 4-21
Fig . 4-17 Landing Attitudes. Skid Gear ......................................... 4-21
Fig . 4-18 Landing Attitudes. Tail Wheel Gear ................................... 4-22
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AMCP 706-201
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LIST OF ILLUSTRATIONS (Continued)
Fig . No . Title Page
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Fig . 4-19 Landing Attitudes, Quadricycle Gear .................................. 4-22
Fig . 4-20 Most Common Asymmetrical Landing Attitudes ............... 4-23
Fig . 4-21 Asymmetrical Attitudes, Tricycle Gear ........................... 4-24
Fig . 4-22 Asymmetrical Attitudes, Skid Gear ................... 4-24
Fig . 4-23 Asymmetrical Attitudes. Tail Wheel ................... 4-25
Fig . 4-24 Asymmetrical Attitudes. Quadricycle Gear .............................. 4-26
Fig . 4-25 Considerations Affecting Conformability of Landing Gear to Terrain ........ 4-27
Fig . 4-26 Typical Impact Pulse for ............................... 4-30
Fig . 4-27 Braked Roll. Two-point ............................... 4-34
Fig . 4-28 Braked Roll. Three-point .................................. 4-34
Fig . 4-29 Turning .................................. .......... 4-35
Fig . 4-30 Horsepower and Torque. Respectively. vs Rotor Speed at Topping and Ground
Idle Powers for a Typical Free-turbine Engine ................. 4-37
Fig . 4-31 Drag Limits for Helicopter Fittings ............................... 4-43
Fig . 4-32 Contour Map Over the Rotor Disk o Airloads. lb/in .............. 4-50
Fig . 4-33 Effect of Blade Twist on Loading Distribution .......... ............. 4-51
Fig . 4-34 Rotor Plan View (Looking Down) ..................................... 4-51
Fig . 4-35 Nondistorted Rotor Wake Geometry (Wake Skew Neglected) .............. 4-52
Fig . 4-36 Wake Trajectories for One Blade (Hovering Flight. OGE) ................. 4-53
Fig . 4-37 Angle-of-attack Distribution at High Forward Speed ................ 4-54
Fig . 4-38 Mach Number Distribution at High Forward Speed ...................... 4-55
Fig . 4-39 Modal Representation of Blade Displacements ........................ 4-58
Fig . 4-40 Elements in Analysis ................................................ 4-59
Fig . 4-41 Typical Blade Cross-sectional Loading ........................... 4-60
Fig . 4-42 Representative Blade Structure ........................................ 4-61
Fig . 4-43 Determination of Constant K. to Calculate Critical Buckling Stress (Eq . 4-39) 4-6 1
Fig . 4-44 Typical Flapwise-load Envelope ....................................... 4-63
Fig . 4-45 Typical Tail Rotor Gearbox Load Diagram ............................. 4-70
Fig . 4-46 Planetary System Load Diagram ...................................... 4-73
Fig . 4-47 Loading Diagram for y-Direction ...................................... 4-75
Fig . 4-48 Typical Main Rotor Control System Schematic .......................... 4-77
Fig . 4-49 Typical Upper Control System on Aft Rotor of a Tandem Helicopter ....... 4-78
Fig . 4-50 Blade Pitch Motion for Fully Articulated Rotor .................. 4-79
Fig . 4-51 Rotor Pitch Change ................................................. 4-80
Fig . 4-52 Typical Bungee Capsule ............................................. 4-81
Fig . 4-53 Typical Tail Rotor Control System Schematic ........................... 4-82
Fig . 4-54 Pitch Link Load Waveform .......................................... 4-83
Fig . 4-55 Block Diagram. Control Load Determination ............................ 4-85
Fig . 4-56 Alternating Pitch Link Load vs Airspeed ............................... 4-88
Fig . 4-57 Predicted Alternating Pitch Link Load vs Airspeed ...................... 4-89
Fig . 4-58 Spring Mass System ................................................. 4-90
Fig . 4-59 Typical Steady-state Maneuvers ....................................... 4-92
Fig . 4-60 Typical Transient Maneuvers ......................................... 4-93
Fig . 4-61 Load-Factor vs Airspeed (For Various Pitch Velocities) .................... 4-94
Fig . 4-62 Load Factor vs Bank Angle .......................................... 4-94
Fig . 4-63 Typical Tail Boom Weight Distribution ................................ 4-96
Fig . 4-64 Unit Loading for Tail Boom .......................................... 4-97
Fig . 4-65 Typical Fuselage Shear and Moment Curves ............................ 4-99
Fig . 4-66 Rotor Vibratory Loads Transmitted to Structure ......................... 4-101
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LIST OF ILLUSTRATIONS (Continued)
Fig . No. Title Page
.
Fig . 4-67 Left Wing Load Grid. Showing Load Stations and Monitoring Stations ...... 4-105
Fig . 4-68 Empennage and Aft Body Load Grid. Showing Load Stations and Monitoring
Stations ...................................... 4- 106
Fig . 4-69 Effects of Dynamic Load Factor Increment ............................. 4- 107
Fig . 4-70 Dynamic Increment Definition ........................................ 4- 107
Fig . 4-71 Ramp Force Excitation .............................................. 4- 108
Fig . 4-72 Typical Spanwise and Chordwise Lift Distribution ....................... 4-108
Fig . 4-73 Typical Ordnance Blast Pressure ...................................... 4- 109
Fig . 4-74 Effect of Velocity on Incremental Lift Coefficient in Gust Encounter ........ 4-1 10
Fig . 4-75 Wing and Rotor Gust Load Comparison at Low Airspeed ................ 4-1 10
Fig . 4-76 Comparison of Towing Conditions With Different Restraints .............. 4-1 11
Fig . 4-77 Allowable Shear Buckling Shearflow ................................... 4-1 11
Fig . 4-78 Schematic Beam-rib Structure ......................................... 4-1 12
Fig . 4-79 Comparison of Combined Shear and Torsion for Two Loading Conditions ... 4-1 13
Fig . 4-80 Combined Bending and Axial Load for Two Loading Conditions ........... 4-1 14
Fig . 4-81 Combined Loading Condition Envelopes at a Particular Location ........... 4-1 14
Fig . 4-82 Schematic of Spring Substitution for Skid Gear .......................... 4-1 16
Fig . 4-83 Time History of Level Landing With Forward Velocity ................... 4-1 18
Fig . 4-84 Schematic Mission Profile-Personnel Transport Mission .................. 4- 128
Fig . 4-85 Mission Gross Weight Variation With Time ............................. 4-131
Fig . 4-86 Goodman Diagram ................................................. 4-132
Fig . 4-87 Typical S-N Curve .................................................. 4-132
Fig . 4-88 S-N Curve Shapes for Steel and Aluminum ............................. 4-133
Fig . 4-89 Example S-N Curve ................................................. 4- 134
Fig . 4-90 Ground-air-ground Cycles ............................................ 4-135
Fig . 4-91 Analytical Demonstration of Infinite Fatigue Life ........................ 4-137
Fig . 5-1 Three Types of Vibration ............................................ 5-3
Fig . 5-2 Simple Harmonic Motion ............................................ 5-4
Fig . 5-3 Time History of an Element off; and y. in Steady State ................... 5-5
Fig . 5-4 Complex Representation of Condition of Fig . 5-3 ........................ 5-6
Fig . 5-5 Typical Normal Mode of a Helicopter in Plane of Symmetry .............. 5-7
Fig . 5-6 Relative Modal Amplitude vs Forcing Frequency ........................ 5-7
Fig . 5-7 Mathematical Model of an Isolation System ............................. 5-10
Fig . 5-8 Normalized Response for a Typical Isolation System ..................... 5-12
Fig . 5-9 Principal Elements of the DAVI System ................................ 5-12
Fig . 5-10 Southwell Diagram .................................................. 5-14
Fig . 5-11 Rotor Viewed in Fixed System Oscillating in Ground Resonance Mode ...... 5-15
Fig . 5-12 Plot of Roots of Undamped Ground Resonance Equations ................ 5-15
Fig . 5-13 Phase Relations of Blades (n - 1). 0. 1 in Regressing Mode .............. 5-18
Fig . 5-14 Phase Relations of Blades (n - 1). 0. 1 in Advancing Mode .............. 5-19
Fig . 5-15 Phase Relations of Blades (n - 1). 0. 1 in Differential Collective Mode ..... 5-19
Fig . 5-16 Lift Deficiency OA/OB and Phase Lag 4 vs Reduced Frequency h/V ..... 5-20
.
Fig 5-17 Experimental Reduced Flutter Speed V/(b o.) and Flutter Frequency o/w. for
Single Blade With 37% Chordwise CG Location ........................ 5-21
Fig . 5-18 Torsional Amplitude vs Chordwise CG Position for p = 0.3, Articulated Blade 5-2 1
Fig . 5-19 Torsional Stress Amplitude vs Advance Ratio. Nonarticulated Blade ........ 5-21
Fig . 5-20 Boundary from Advancing Tip Mach No . 0.85 and 270-deg Azimuth Divergence
Limit for Torsional Blade Stiffness Parameter 2 GJ/(2rpC? R’) =
11 .O Oo(fPS)* ....................................................... 5-22
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AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No . Title Page
Fig . 5-21 Frozen Azimuth Flapping Instability Boundary .......................... 5-22
Fig . 5-22 Damping Levels of Articulated Blade. B = 1.00 ......................... 5-24
Fig . 5-23 Flapping Stability Boundary for Rigid Articulated Blade With Elastic Root Re-
straint ........................................................... 5-24
Fig . 5-24 Amplitude Ratio vs Advance Ratio for Articulated Blade. y = 5 With and
Without Torsional and Flap-bending Flexibility ......................... 5-24
Fig . 5-25 Hingeless Blade in Drooped and Leading Position ........................ 5-25
Fig . 5-26 Prop-rotor Pitching and Yawing About Pivot ........................ 5-28
Fig . 5-27 Stability Boundaries for System of Fig . 5-26 ............................. 5-28
Fig . 5-28 Multiblade Root Plots for Three- and Four-bladed Rotors With Integral Tilting
Moment Feedback ................................................. 5-30
Fig . 5-29 Definition of Parameters for Ground Resonance Analysis ................. 5-31
Fig . 5-30 Damping Ratios for Blade and Airframe at Ground Resonance Stability Limit 5-32
Fig . 5-31 Coupled Airframe/Rotor Lead-lag Instability Ranges ..................... 5-32
Fig . 5-32 Sample Helicopter Drive System ...................................... 5-40
Fig . 5-33 Diagram of Sample Drive System ..................................... 5-40
Fig . 5-34 Diagram of a Multiple-mode Torsional System .......................... 5-41
Fig . 5-35 Generalized Diagram of Individual Mode from Fig . 5-34 .................. 5-42
Fig . 5-36 Variation of Natural Frequency With Inertia of Power Turbine-Example ... 5-43
Fig . 5-37 Variation of Natural Frequency With Stiffness of Turbine Output Shaft-Example 5-44
Fig . 5-38 Simplified Block Diagram of Engine. Rotor. Drive. and Engine Control Systems 5-47
Fig . 6-1 Definition of Axis Systems ........................................... 6-3
Fig . 6-2 Definition of Parameters and Sign Convention for a Compound. Single-rotor
Helicopter ........................................................ 6-4
Fig . 6-3 Definition of Parameters and Sign Convention for a Tandem-rotor Helicopter 6-5
Fig . 6-4 C, Values Required for Pitch-roll Decoupling ........................... 6-8
Fig . 6-5 Disturbed Hovering Condition ........................................ 6-10
Fig . 6-6 Period of Oscillation for A. = 0 ...................................... 6-11
Fig . 6-7 Time to Double Amplitude for A. = 0 ................................ 6-12
Fig . 6-8 Period of Oscillation for A. = 0.5 sec-* ................................ 6-13
Fig . 6-9 Time to Double or Halve Amplitude for A. = 0.5 secW2. ................. 6-14
Fig . 6-10 Attitude Input of Gyratory System in Steady-state Pitching Oscillation ...... 6-16
Fig . 6-1 1 Damping Effect of Gyratory System in Steady-state Pitching Oscillation ..... 6-17
Fig . 6-12 Effect of Gyro System Linkage Ratio C, on Hovering Stability ............. 6-18
Fig . 6-1 3 Effect of Advance Ratio on Allowable Feedback Parameter A .............. 6-20
Fig . 6-14 Forces and Moments Acting on a Single-rotor Helicopter While Hovering ... 6-22
Fig . 6-15 Effect of Center of Gravity Position on Stability ......................... 6-23
Fig . 6-16 Damping vs Control Sensitivity. Vertical Motion ..................... 6-25
Fig . 6-17 Minimum Control Sensitivity and Damping Requirements in Pitch from MI
8501 ..................... .................................. 6-30
Fig . 6-1 8 Minimum Control Sensitivity an ping Requirements in Roll from MIL-H-
............................... 6-3 1
Fig . 6-19 Minimum Control Sensitivity and Damping Requirements in Yaw from MIL-H-
8501 ............. ........ .............................. 6-32
.
Fig 6-20 Comparison of Flight Test Results With MIL-H-8501 Requirements for Instru-
ment Flight ....................................................... 6-33
Fig . 6-21 Pitching Moments Produced in Hover by Stick Displacement on a Single-rotor
Helicopter ........................................................ 6-36
xxxviii
AMCP 706-201
LIST OF ILLUSTRATIONS (Continued)
Fig . No . Title Page
.
Fig 6-22 Pitching Moments Produced in Hover by Stick Displacement on a Tandem-rotor
Helicopter ........................................................ 6-38
.
Fig 6-23 Yawing Moments Produced in Hover by Pedal Displacements on a Tandem-rotor
Helicopter ........................................................ 6-40
Fig . 6-24 Forces and Moments on Single-rotor Helicopter in Forward Flight ......... 6-42
Fig . 6-25 Coefficients of Flapping With Respect to Speed Derivative ................ 6-43
Fig . 6-26 Coefficients of Angle of Attack With Respect to Speed Derivative .......... 6-44
Fig . 6-27 Flapping Derivatives ................................................ 6-46
Fig . 6-28 Forces and Moments Acting on Tandem-rotor Helicopters ................ 6-47
Fig . 6-29 Angle-of-attack Envelope for Armed Helicopter (Clean Configuration) ....... 6-49
Fig . 6-30 Pitch Attitude Envelope for Armed Helicopters (Clean Configuration) ....... 6-50
Fig . 6-31 Level Flight (120 kt) ................................................ 6-50
Fig . 6-32 Descending Flight (160 kt) ........................................... 6-51
Fig . 6-33 Typical Cyclic Stick Plot ............................................. 6-53
Fig . 6-34 Longitudinal Control Schematic ....................................... 6-55
Fig . 6-35 Spring Feel System With Breakout .................................... 6-55
Fig . 6-36 Maneuver and Displacement Force Gradients ........................... 6-56
Fig . 6-37 Flight Control System Schematic ...................................... 6-58
Fig . 6-38 Pitch Responses to Unit Step Control Input ............................. 6-63
Fig . 6-39 Pitch and Pitch-rate Responses to Unit Step Control Input for Aerostatic Stability 6-64 .
Fig . 6-40 Augmentor Loop ................................................... 6-65
Fig . 6-41 Vertical Acceleration Response to Unit Step Control Input ................ 6-66
Fig . 6-42 Root Loci for Hovering Helicopter .................................... 6-68
Fig . 6-43 Control Schematic With Augmentor Servo .............................. 6-68
Fig . 6-44 Coning Angle Sensor With Proportional Feedback ....................... 6-69
Fig . 6-45 Coning Frequency Response to Periodic Inflow .......................... 6-70
Fig . 6-46 Tilting Moment Sensor With Integral Feedback .......................... 6-70
Fig . 6-47 Fore-aft Flapping Frequency Response to Periodic Inflow ................. 6-71
Fig . 6-48 Free-body Gust Alleviation Factor ..................................... 6-71
Fig . 6-49 Von Karman Vertical Gust Velocity Spectrum. L = 400 ft ............... 6-71
Fig . 6-50 Integral Feedback Gain K. at Stability Limit ............................ 6-72
Fig . 7-1 Typical Transmission System in Single-rotor Helicopter ................... 7-2
Fig . 7-2 Typical Main Gearbox Lubrication System .............................. 7-4
Fig . 7-3 Spur Gear and Rack ................................................ 7-6
Fig . 7-4 Helical Gear and Rack Terminology ................................... 7-8
Fig . 7-5 Bevel Gear and Rack ................................................ 7-9
Fig . 7-6 Zero1 Bevel Gear ................................................... 7-10
Fig . 7-7 Minimum Mesh Path for a Sun-pinion-ring Mesh ........................ 7-11
Fig . 7-8 Hypoid Gears ...................................................... 7-14
Fig . 7-9 Pitch Surfaces for Basic Gear Arrangements ............................ 7-15
Fig . 7-10 Plane Tooth Action ................................................. 7-16
Fig . 7-1 1 Tooth Profile Curvatures ............................................. 7-16
Fig . 7-12 Involute Rack ...................................................... 7-17
Fig . 7-13 Involute Geometry .................................................. 7-17
Fig . 7-14 Gear Scoring Design Guide for Aerospace Spur and Helical Power Gears .... 7-20
Fig . 7-15 Load Capacity vs Surface Finish ...................................... 7-20
Fig . 7-16 Comparison of Standard Design With Full Recess Action Design ... ... 7-25
Fig . 7-17 Simple Ball Bearings ................................................ 7-26
.
Fig 7-18 Simple Ball/Roller Bearings .......................................... 7-27
axxix