The Art of the Helicopter John Watkinson - Karatunov.net

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Fig. 7.2 (a) When attitude conditions from the artificial horizon can act directly upon the powered controls, the result is an autopilot. Under different circumstances, the pilot may wish to have complete control or no control or even a partial control as he wishes. The control system must be able to react to those different requirements. (b) In a series actuator system, a servo extends or shortens a pushrod from the control column. If the autopilot is on, it will simply cancel everything the pilot does. If the pilot releases the stick, the actuator may move the stick instead of the controls. Series actuators must lock the control column when the autopilot is engaged. (c) A parallel actuator system in which the actuator moves the centre reference of the cyclic stick springs. (d) Modern system in which the pilot’s input produces a false error to the autopilot. By cancelling the false error, the autopilot carries out the pilot’s wishes. Control 261
262 The Art of the Helicopter Fig. 7.3 With an autopilot, attitude, altitude, airspeed and heading can be controlled automatically, but the pilot must still select the course. With an autopilot coupled to a flight director, navigational inputs can control the autopilot so that a course can be held. understand the dynamic response of the helicopter in order to avoid any overshooting or oscillation when correcting the attitude. The attitude of the machine is still controlled by the pilot, but the stability of the machine is improved by using attitude signals from the artificial horizon. In Figure 7.3 the process has been taken one stage further. Here the augmented stability achieved in Figure 7.1(b) makes it possible for the machine to be controlled automatically. Inputs to the signal processor from the altimeter, the airspeed indicator and from a compass allow the machine to hold a heading without any action from the pilot. This system is generally called an automatic pilot or just an autopilot. The system of Figure 7.3 relieves the pilot of the need to fly the machine continuously, but can only hold a heading and would not compensate for a change in wind strength or direction. However, with further inputs from a navigation system or from a flight director the machine could hold a course determined by a GPS receiver, VOR beacon or an instrument landing system (ILS). In this case the flight director creates a further feedback loop. The actual course is computed by navigational equipment and compared with the desired course. Any error is then fed to the autopilot as a modified heading reference. In early helicopters, the provision of stability augmentation and autopilot systems was frequently optional, whereas in modern machines such systems are often designed in from the outset. One modern trend is away from instruments with a direct visual readout. Instead instruments may be used which have only an electrical output and are best called sensors or transducers. These outputs are supplied not only to the autopilot, but also to a display processor that produces a virtual instrument panel on a computer graphics-type display. This is known colloquially as ‘glass cockpit’ technology. One advantage is that the instruments themselves can be located anywhere convenient and do not have to be in the instrument panel. In helicopters, the stability augmentation and autopilot capabilities may be extended into the hover. In this case altitude and airspeed information from atmospheric pressure is not good enough and instead RADAR will be used to measure height and groundspeed. In flying cranes and in search-and-rescue helicopters the ability to remain at a
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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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Page 228 and 229: Engines and transmissions 213 Fig.
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Page 238 and 239: Fig. 6.16 The complex fuel system o
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Page 270 and 271: Engines and transmissions 255 resul
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Page 286 and 287: Fig. 7.7 The remote indicator for a
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Page 290 and 291: Fig. 7.11 The VSI (vertical speed i
Page 292 and 293: Fig. 7.13 A chaser system which all
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Page 300 and 301: Fig. 7.19 The turn indicator is spr
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Page 304 and 305: Fig. 7.24 Using RADAR signals. At (
Page 306 and 307: Fig. 7.27 Transducers used in signa
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Page 312 and 313: Fig. 7.33 The false codes created i
Page 314 and 315: Fig. 7.35 In a pure binary system,
Page 316 and 317: Fig. 7.38 Producing two’s complem
Page 318 and 319: Fig. 7.40 A power-assisted hydrauli
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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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Helicopter performance 337 In the c
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Helicopter performance 339 of its c
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8.10 Stability Helicopter performan
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Fig. 8.13 The origin of pitchup ins
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Helicopter performance 345 moment f
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9 Other types of rotorcraft Althoug
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Other types of rotorcraft 349 De la
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Other types of rotorcraft 351 Fig.
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Other types of rotorcraft 353 incre
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Other types of rotorcraft 355 and c
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Fig. 9.7 The Bell-Boeing Osprey til
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(a) (b) Other types of rotorcraft 3
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Other types of rotorcraft 365 a low
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Other types of rotorcraft 367 the y
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Other types of rotorcraft 371 the r
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Other types of rotorcraft 373 For e
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Acceleration: and force, 22-5 and v
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Convertiplane, 11-12, 355-8 Bell-Bo
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tanks, 219-20 turbine engines, 237-
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Lockheed flybar system, 309-13 AMCS
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centrifugal stiffening, 71, 100 and
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tail/main rotor interaction, 173 te
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