Cover	1
	Title Page	5
	Copyright	6
	Contents	7
	Introduction	11
	Notations and Acronyms	15
	1: General Considerations	21
	1.1. Power transmission in aircraft	21
	1.1.1. Needs and requirements for secondary power and power flows	21
	1.1.2. Actuation functions	22
	1.1.3. Actuation needs and constraints	25
	1.2. Primary and secondary power transmission functions for actuators	28
	1.2.1. Primary functions	30
	1.2.2. Secondary functions	32
	1.2.3. Signal approach and power approach	33
	1.2.4. Types of actuators	34
	1.3. Hydraulic power actuation	36
	1.3.1. Units and reference values	36
	1.3.2. Energy transport by a liquid	38
	1.3.3. Historical evolution of power and pressure use	42
	1.3.4. Potential advantages and disadvantages of hydraulic technology	47
	1.3.5. Overall hydraulic circuit architecture	51
	2: Reliability	53
	2.1. Risks and risk acceptance	53
	2.2. Response to failure	56
	2.2.1. Resistance to failure	57
	2.2.2. Tolerance to failure	58
	2.2.2.1. Fail-active system	59
	2.2.2.2. Fail-safe system	60
	2.2.3. Examples	60
	2.3. Redundancy	60
	2.3.1. Static redundancy	64
	2.3.1.1. Simple parallel redundancy	66
	2.3.1.2. Redundancy by averaging	66
	2.3.1.3. Majority voting redundancy	67
	2.3.1.4. Command/monitoring	68
	2.3.2. Dynamic redundancy	68
	2.4. Feared events and failure rates in actuation	71
	2.5. Fundamentals of reliability calculation	72
	2.5.1. Variables used in reliability calculation	72
	2.5.2. Generic failure rate models	75
	2.5.2.1. Exponential probability of failure distribution	75
	2.5.2.2. Weibull distribution	76
	2.5.3. Reliability of element associations	77
	2.5.3.1. Elements associated in series	77
	2.5.3.2. Elements associated in parallel	77
	2.5.3.3. Elements associated through majority vote	79
	2.5.3.4. Elements associated through detection–correction	79
	2.5.3.5. Examples	79
	2.6. Short glossary of technical terms pertaining to reliability	80
	3: Hydraulic Fluid and its Conditioning	83
	3.1. Needs and constraints	83
	3.1.1. Opportunities and constraints in hydrostatic power transmission	83
	3.1.2. Actual hydraulic fluid	84
	3.1.3. Physical properties	86
	3.1.3.1. Fire-proofing	87
	3.1.3.2. Insufficient awareness of effective physical properties	87
	3.1.3.3. Impact of compressibility on performances	87
	3.1.3.4. Very high sensitivity of viscosity to temperature	87
	3.1.3.5. Impact of free gas	88
	3.2. Fluid conditioning	88
	3.2.1. Fluid in sufficient quantity	88
	3.2.1.1. Facilitate pump suction	89
	3.2.1.2. Allow volume to vary as a function of pressure and temperature	89
	3.2.1.3. Compensate for the volume variation caused by equipment	89
	3.2.1.4. Compensate for external leakage	90
	3.2.2. Pressurization and charging	90
	3.2.2.1. Pressurization	90
	3.2.2.2. Charging	93
	3.2.3. Filtration	93
	3.2.3.1. Suction filter	95
	3.2.3.2. Drain filter	95
	3.2.3.3. High pressure filter	95
	3.2.3.4. Integral filter	96
	3.2.3.5. Return filter	96
	3.2.3.6. Breather filter	96
	3.2.3.7. Filling filter	96
	3.2.4. Thermal management	96
	3.2.4.1. Cooling	97
	3.2.4.2. Heating	98
	3.2.5. External leakage collection	101
	3.3. Monitoring and maintaining the fluid in working conditions	101
	3.3.1. Fluid quantity	102
	3.3.2. Cleanliness	102
	3.3.3. Pressurization – depressurization	103
	3.3.4. Examples	103
	3.4. Energy phenomena caused by the fluid	104
	3.4.1. Hydraulic resistance	104
	3.4.2. Hydraulic capacitance	104
	3.4.3. Hydraulic inertia	107
	3.4.4. Speed of sound in the hydraulic fluid	107
	4: Hydromechanical Power Transformation	109
	4.1. Hydromechanical power transformation	109
	4.2. Functional perspective	114
	4.3. Technological shortcomings	115
	4.3.1. Energy losses	116
	4.3.2. Compressibility of the hydraulic fluid	117
	4.3.3. Wall deformation	117
	4.3.4. Pulsations	117
	4.3.5. Drainage	119
	4.4. Pump driving	120
	4.4.1. Driving performed by main engines: Engine Driven Pump (EDP)	120
	4.4.2. Driving performed by an electric motor: Electro Mechanical Pump (EMP) or Alternative Current Motor Pump (ACMP)	122
	4.4.3. Driving performed by a hydraulic motor: Power Transfer Unit (PTU)	122
	4.4.4. Dynamic air driving: Ram Air Turbine (RAT) or Air Driven Pump (ADP)	124
	4.4.5. Driving performed by a gas turbine: Solid Propellant Gas Generator (SPGG) or Monofuel Emergency Power Unit (MEPU)	124
	4.4.6. Fluid supply under pressure	125
	5: Power Metering in Hydraulics	127
	5.1. Power metering principles	127
	5.2. Power-on-Demand	130
	5.2.1. Metering by pump drive adjustment	130
	5.2.2. Metering by displacement adjustment	131
	5.3. Metering by hydraulic restriction	134
	5.3.1. Functional configuration	135
	5.3.1.1. Single-effect and double-effect hydraulic user	136
	5.3.1.2. Intermediate state	136
	5.3.1.3. Directional and metering functions	137
	5.3.1.4. Metering carried out by a flow control valve	138
	5.3.1.5. Metering carried out by a proportional valve	139
	5.3.2. Types of distribution	140
	5.3.2.1. Series distribution	140
	5.3.2.2. Parallel distribution	141
	5.4. Impact of restriction configuration and properties on the metering function	142
	5.4.1. Fixed hydraulic restriction	142
	5.4.1.1. Laminar flow	143
	5.4.1.2. Turbulent flow	144
	5.4.1.3. Transition	144
	5.4.1.4. Orders of magnitude	145
	5.4.2. Variable hydraulic restriction	145
	5.4.2.1. Types of restrictions	145
	5.4.2.2. Geometrical characteristics of a variable restriction	147
	5.4.2.3. Power capabilities	149
	5.4.2.4. Properties with respect to control	153
	5.4.2.5. Interfacing and valve opening controls	155
	5.4.2.6. Resistance or tolerance to jamming	158
	5.5. Servovalves	159
	5.5.1. Architecture	159
	5.5.2. Incremental improvements of servovalve performances	163
	5.5.3. Power supply of the electromagnetic motor	165
	5.5.4. Concepts of pilot stages	165
	5.5.5. Direct drive valve	171
	5.5.5.1. Applications	172
	5.5.5.2. Architecture of direct drive valves	173
	6: Power Management in Hydraulics	177
	6.1. Power distribution	177
	6.2. Providing power	177
	6.2.1. Transporting fluid	177
	6.2.1.1. Hydraulic connectors	179
	6.2.1.2. Hydraulic lines	179
	6.2.1.2.1. Nature of hydraulic lines	179
	6.2.1.2.2. Hydraulic line size	180
	6.2.2. Isolating	182
	6.2.3. Sequencing user power supplies	185
	6.2.4. Merging sources	185
	6.2.5. Sharing sources	186
	6.2.5.1. Flow sharing with priority	187
	6.2.5.2. Balanced flow sharing	187
	6.2.6. Storing/restoring energy	188
	6.2.6.1. Needs	188
	6.2.6.2. Setup	190
	6.2.7. Adjusting the pressure level	191
	6.3. Protecting	192
	6.3.1. Protecting against overpressure/overload	193
	6.3.2. Protecting against cavitation and desorption	196
	6.3.3. Protecting against over-consumptions	198
	6.4. Managing the load	200
	6.4.1. Locking the load in position	200
	6.4.2. Ensuring irreversibility	201
	6.4.3. Releasing the load	202
	6.4.4. Damping the load	203
	6.4.4.1. Damping a driving load when the actuator is active	203
	6.4.4.2. Damping a hydraulically released load	203
	6.4.4.3. Avoiding load vibrations	205
	6.4.4.4. End-stop snubbing	206
	7: Architectures and Geometric Integration of Hydraulically-supplied Actuators	209
	7.1. Introduction	209
	7.2. Arrangement of actuation functions	210
	7.3. Architecture and routing of hydraulic power networks	211
	7.3.1. Architecture	211
	7.3.2. Routing	213
	7.4. Integration of components and equipment	213
	7.4.1. In-line integration	214
	7.4.2. Manifold integration	214
	7.4.3. Sub-system integration	217
	7.5. Integration of actuators in the airframe	220
	7.5.1. Controls	220
	7.5.1.1. Moving-body linear actuator	220
	7.5.1.2. Moving-rod linear actuator	221
	7.5.2. Structural integration	223
	7.5.2.1. Range of motion confined to a few degrees	223
	7.5.2.2. Range of motion greater than 90°	225
	7.5.2.3. Secondary flight controls	228
	Bibliography	229
	Index	239
	Other titles from ISTE in Systems and Industrial Engineering – Robotics	241
	EULA	248