The Art of the Helicopter John Watkinson - Karatunov.net

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centrifugal stiffening, 71, 100 and centripetal force, 38–40 CM of, 39–40 coning angle, 71–2 and downwash, 74, 76 dragging flexures, 159 dynamic balancing, 40 dynamic inflow, 75 elastomeric damping, 159, 160 fatigue, 162 feathering, 62, 134–6 cyclic feathering, 98 flutter, 65–6 Fourier analysis shows coefficients of harmonics negative, 48–9 and gyroscopic precession, 52 H-force, 93, 94 harmonic blade motion, 98–9 induced velocity, 74 lift function harmonics, 98 lightning protection, 162 never exceed speed, 97 root tension, 39 rotor conning, 71–2 rotor H-force, 93 stall limit, 94, 95 taper and twist, 77–8, 116, 162 tip loss, 77, 81–4, 173 torque and thrust, 72–3 virtual hinges, 159 Y-force, 93, 94 see also Airfoils; Rotation, mechanics of; Vibration from blades Rotor brakes, 17 Rotor configurations see Multi-rotor helicopters; Tandem rotor helicopters Rotor heads: about rotor heads, 117 articulated: about articulated rotors, 118 in high winds, 158 rotor response, 133 collective control, 68–70, 136–7 control axis, 120, 121–2 Coriolis force, 26 CV (constant velocity) joint, 125 cyclic trim, 141–2 dragging (lead lag), 143–5 dragging/dragging hinges, 123–6 droop stops, 123 feathering, 62, 134–6 flapping, 122–3 flapping bearings/hinges, 158–60 flexural, 134 rotor response, 133 hingeless head, 128 rotor response, 133–4 hinges order, 126–8 Hooke joint, 123–5 offset heads, 124–5 pitch control, 136–41 servo tab system, 138–9 shaft axis, 118–19 swashplates, 136–7 teetering two-bladed heads, 128, 129–30, 155–8 rotor response, 133 tilting heads, 142–3 tip path axis, 119–21 virtual hinges, 159 zero-offset heads, 129–30, 155–8 problems with, 130–1 rotor response, 133 Rotor response, 131–4 following/following rate, 132 positive feedback problems, 133 response rate, 132 Rotor revolutions per minute see RRPM Rotor shaft, torsional vibration, 110 Rotorcraft types, 9–12 conventional single main rotor, 9 see also Convertiplane; Gyrodyne (compound helicopter); Gyroplanes (autogyro); Multi-rotor helicopters RPM control of engines, 195–8 RRPM (rotor revolutions per minute), 52, 68, 72 metering, 246–7 rotor speed control/governing, 195–8, 258 turbine engines, 236 Runway numbering, 264 SAE numbers (oil), 206 Safety, and performance, 324 Sampling, 292 Servo tab system, 138–9 Servos: artificial feel systems, 59 compensation, 57 hardover failure, 59, 321 open loop condition, 57 servo error, 57–8 stiffness, 57 see also Feedback SHM (simple harmonic motion), 41–4 and damping, 42 see also Rotation Shock waves, 35 Short-term Fourier transform (STFT), 48 SI units, 23 Sidebands, 44–6 and blade vibration, 103 Nyquist frequency, 45–6 Index 387
388 Index Sideways flight, 178 Sikorsky: Blackhawk, 176 CH-47 hydraulics, 256–7 CH-54 Skycrane, 171 R-4, 129 R-5, 158 S-65/Sea Stallion/Sea Dragon, 176, 180 S-67 winged helicopter, 351 S-76B, 181 VS-300, 2, 4 Simple harmonic motion see SHM Slicing, 295 Sliding swashplates, 136–7 Slip, and stability, 344–5 Slip indicator, 171, 284–6 Slip string device, 287–8 Slip and turn indicators, gyroscopic, 284–6 Slope landing, 153–4 Sound: basic mechanism in gases, 33–6 percussion (transient), 35 periodic, 35–6 shock waves, 35 speed of propagation, 34–5 Speed limit, 97–8 auxiliary forward thrust, 97 Spiral stability, 342, 345 Stabilators, 180, 181–2 Stability, 341–6 about stability, 341–2 augmentation control, 260–2, 305–13 about stability augmentation, 305 in model helicopters, 312–13 directional stability, 342–3 Dutch roll, 345 dynamic stability, 343–4 flybars, 305–13 hover stability, 346 lateral stability, 343, 344 pitch stability, 342 with slip, 344–5 speed stability, 342 spiral stability, 342, 345 and VFR and IFR operation, 341 see also Bell flybar system; Hiller flybar system; Lockheed flybar system Stall: advancing blade compressibility stall, 96, 97 airfoil stall, 66 blade stall and compressibility, 93–7 partial blade stall, 94 stall limit, 94, 95 Starter motors, gasoline engines, 204 Static droop, 196–7 STFT (short-term Fourier transform), 48 Stiffness and compliance, 41 Stiffness controlled systems, 42 Strength and rigidity, 25–6 Swashplates, 136–7 Swirl, 64, 78 Sycamore helicopter, 5, 6, 143 Synchro generators, 291 Synchro motors, 291–2 Synchropter side-by-side rotor helicopters, 13–15, 364–8 Kaman H-43 (Husky), 366–8 Kaman K-Max, 367–8 Kolibri (hummingbird) helicopter, 364–6 yaw control, 366–7 Tail function and design: about tails, 166–9 boom construction, 184–6 boom strakes, 185 construction, 171–2 crosswind problems, 178–9 D-ring, 166–7 downwash problems, 180 fenestron system, 167, 186–7 fin effect, 172 fins, 182–3 flapback and dragging, 172 forward flight aspects, 179 Gurney flap, 181 NOTAR (NO TAil Rotor) system, 167, 187–9 power and control, 167–8 sideways flight, 178 slip indicator, 171 stabilators, 180, 181–2 swashplate, 168 tail plane design, 179–81 tip loss, 173 torque balancing, 169–71 weathercocking, 172 yaw problems, 177–9 see also Tail rotors Tail rotors: air flow direction, 173–6 canted, 177 collective pitch control, 168–9 on cranked booms, 175–6 dangers, 167 flapping hinges, 172 gearbox, 168 location, 173–7 noise, 167 performance, 177–9 size compromises, 173 tail rotor drift, 169–70 tail rotor roll, 169–70
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The Art of the Helicopter
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The Art of the Helicopter John Watk
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Contents Preface xi Acknowledgement
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4.12 Feathering 134 4.13 Pitch cont
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8.5 Power management 326 8.6 Flying
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xii Preface reader to make sense of
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1 Introduction to rotorcraft 1.1 Ap
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Introduction to rotorcraft 3 Fig. 1
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Introduction to rotorcraft 9 for th
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Introduction to rotorcraft 11 Fig.
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(a) (b) (c) (d) Introduction to rot
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Fig. 1.18 The contra-rotating coaxi
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Fig. 1.20 The structure of a light
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Introduction to rotorcraft 19 wings
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Introduction to rotorcraft 21 a rot
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Technical background 23 Fig. 2.1 At
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Fig. 2.3 Effect of force on velocit
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C Force A E Resultant (a) Force B (
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(a) (b) Technical background 29 Fig
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Technical background 31 Fig. 2.11 A
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Technical background 33 Fig. 2.12 (
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Technical background 35 If the volu
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Fig. 2.16 The definition of a radia
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Technical background 39 force would
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Technical background 41 Figure 2.20
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Technical background 43 force where
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Technical background 45 the cosine
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Technical background 47 Fig. 2.28 F
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Technical background 49 Fig. 2.30 T
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Technical background 51 centripetal
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2.17 The gyroscope Technical backgr
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Technical background 55 of oscillat
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Technical background 57 the inertia
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Technical background 59 shut down a
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3 Introduction to helicopter dynami
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Introduction to helicopter dynamics
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(a) (c) (b) Introduction to helicop
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(a) (b) (c) (d) Introduction to hel
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Fig. 3.23 Conditions for hover and
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(a) (b) Introduction to helicopter
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(a) (b) Introduction to helicopter
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4.1 Introduction 4 Rotors in practi
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(a) (b) Rotors in practice 119 Fig.
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Rotors in practice 121 Designers of
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Rotors in practice 123 opposite occ
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Rotors in practice 125 Fig. 4.6 (a)
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Rotors in practice 127 assembly tha
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Rotors in practice 129 Pitch change
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× T=c× D Rotors in practice 131 F
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Rotors in practice 133 In a real he
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Rotors in practice 135 Fig. 4.15 Va
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(a) (b) Rotors in practice 137 Fig.
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Rotors in practice 139 Fig. 4.18 Th
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Rotors in practice 141 swashplate a
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Fig. 4.23 A fixed-pitch tilting hea
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Rotors in practice 145 Fig. 4.25 Bl
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Rotors in practice 147 Fig. 4.27 Ef
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Rotors in practice 149 Fig. 4.29 (a
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Rotors in practice 151 concerned ar
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Rotors in practice 153 and lag damp
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Rotors in practice 155 disappears a
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(d) (e) (f) Rotors in practice 157
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Rotors in practice 159 hull and a v
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Rotors in practice 161 Fig. 4.35 (C
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Rotors in practice 163 Abrasion is
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Rotors in practice 165 There are so
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eing more visible to ground personn
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otates the rod in the screw thread.
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In the case of a rotor having offse
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The tail rotor designer is faced wi
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Fig. 5.5 A right-side wrong-directi
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centre of mass. The solution was to
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safe to start the rotors. However,
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Fig. 5.10 Tail plane locations: (a)
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Fig. 5.12 (a) A top-mounted fin is
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Fig. 5.14 (a) Main rotor lateral ro
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long. The cross-section of the duct
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drag. However, the slots are emitti
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6 Engines and transmissions The pow
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Engines and transmissions 193 the D
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(a) (b) Engines and transmissions 1
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(a) (b) (c) Engines and transmissio
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Fig. 6.5 A typical horizontally opp
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Engines and transmissions 201 the v
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Engines and transmissions 203 The c
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6.9 The oil system Engines and tran
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Engines and transmissions 207 (non-
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(a) (b) Engines and transmissions 2
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Engines and transmissions 211 a hot
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Engines and transmissions 213 Fig.
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Engines and transmissions 215 In wa
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Engines and transmissions 217 is a
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Engines and transmissions 221 own t
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Fig. 6.16 The complex fuel system o
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Engines and transmissions 233 and c
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Engines and transmissions 237 Sensi
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Engines and transmissions 243 the A
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Fig. 6.37 Displays which may be see
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Engines and transmissions 251 slipr
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Engines and transmissions 253 a fau
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Engines and transmissions 255 resul
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Engines and transmissions 257 The p
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Fig. 7.1 (a) A minimal control loop
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Fig. 7.2 (a) When attitude conditio
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fixed point in the hover despite ex
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(a) (b) Fig. 7.4 (a) The earth beha
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7.4 Compass errors A magnetic compa
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In most cases the machine will have
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Fig. 7.7 The remote indicator for a
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is set by the use of a control knob
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Fig. 7.11 The VSI (vertical speed i
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Fig. 7.13 A chaser system which all
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e modified if the gyro is in a movi
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must be in steady flight when the D
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arranged on opposite sides of the p
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Fig. 7.19 The turn indicator is spr
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7.17 Airflow-sensing devices The he
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Fig. 7.24 Using RADAR signals. At (
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Fig. 7.27 Transducers used in signa
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Fig. 7.28 In PCM or digital signall
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(a) Fig. 7.30 Using slicing and rec
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Fig. 7.33 The false codes created i
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Fig. 7.35 In a pure binary system,
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Fig. 7.38 Producing two’s complem
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Fig. 7.40 A power-assisted hydrauli
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Fig. 7.42 An electro-hydraulic valv
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path axis and the flybar axis diver
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and autostabilization, it also prov
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Fig. 7.47 The Lockheed gyrobar syst
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Fig. 7.49 In the Lockheed AMCS, the
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Fig. 7.50 With the autopilot diseng
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or without the AFCS. Systems of thi
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Thus if a VOR receiver detected a 9
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7.29 Fault tolerance In feedback sy
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8 Helicopter performance 8.1 Introd
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Helicopter performance 325 column i
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Helicopter performance 327 Fig. 8.1
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Helicopter performance 329 to skid
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(a) (b) Helicopter performance 331
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Helicopter performance 333 Fig. 8.7
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8.7 Climbingand descending Helicopt
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Page 362 and 363: 9 Other types of rotorcraft Althoug
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Page 366 and 367: Other types of rotorcraft 351 Fig.
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Page 380 and 381: Other types of rotorcraft 365 a low
Page 382 and 383: Other types of rotorcraft 367 the y
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Page 388 and 389: Other types of rotorcraft 373 For e
Page 394 and 395: Acceleration: and force, 22-5 and v
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Page 398 and 399: tanks, 219-20 turbine engines, 237-
Page 400 and 401: Lockheed flybar system, 309-13 AMCS
Page 404 and 405: tail/main rotor interaction, 173 te
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