b-9-hyd120313-w11
TRANSCRIPT
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WELCOME
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Introduction,Aerospace Engineering
Pre RequisitesAircraft
Professions
Global Aviation Industries.
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Aircrafts Maximum Take-Off Weight (MTOW) drivesaerodynamic forces that drive control surface size andloadingA380 1.25 million lb MTOW extensive use of hydraulics
Cessna 172 2500 lb MTOW no hydraulics all manual
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As airplanes grow in size, so
do the forces needed to move theflight controls thus the need to
transmit larger amount of power
Ram Air Turbine
Pump
Hydraulic
Storage/Conditioning
Engine
Pump
Electric
Generator
Electric
Motorpump
Flight ControlActuators
Air Turbine
Pump
Hydraulic system
transmits and controls
power from engine to
flight control actuators
2
Pilot inputs are
transmitted to remote
actuators and amplified
1
3
Pilot commands move
actuators with little effort
4
Hydraulic power is
generated mechanically,electrically and
pneumatically
5
Pilot Inputs
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MotionPrimary Flight Controls
Definition of Airplane Axes
1 Ailerons control roll
2 Elevators control pitch3 Rudder controls yaw
1
3 2
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Controlling AircraftMotionSecondary Flight Controls
High Lift Devices:
Flaps (Trailing Edge), slats (LE Flaps)increase area and camber of wing
permit low speed flight
Flight Spoilers / Speed Brakes: permit
steeper descent and augment ailerons at
low speed when deployed on only one
wingGround Spoilers: Enhance deceleration
on ground (not deployed in flight)
Trim Controls: Stabilizer (pitch), roll and rudder (yaw)
trim to balance controls for desired flight
condition
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Example of Flight
Controls (A320)
REF: A320 FLIGHT CREW OPERATING
MANUAL CHAPTER 1.27 - FLIGHT
CONTROLSPRIMARY
SECONDARY
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Why use Hydraulics?Effective and efficient method of power amplificationSmall control effort results in a large power output
Precise control of load rate, position and magnitude Infinitely variable rotary or linear motion controlAdjustable limits / reversible direction / fast response
Ability to handle multiple loads simultaneously Independently in parallel or sequenced in series
Smooth, vibration free power outputLittle impact from load variation
Hydraulic fluid transmission mediumRemoves heat generated by internal lossesServes as lubricant to increase component life
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Basic Hydraulic System
Reference:
http://www.allstar.fiu.edu/AERO/Hydr02.htm
A valve is
opened, the
hydraulic flows
into the actuator
and presses
against the
piston, causing it
to move and in
turn move theattached control
surface
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General UsesUsed for flight control, actuation of flaps,
slats, weapons bays, landing gear, breaks
Provides the extra force required to movelarge control surfaces in heavy aerodynamicloads.
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General SpecificationsSeveral different FluidsMIL-H-5606, MIL-H-83282, and MIL-H-81019General Temperature Ranges : -65F to 295F
Pressures:Airbus A380 has 5000psi hydraulic systemTypical commercial airline pressure is 3000 psi
http://aerospace.eaton.com/news.asp?articledate=06/01/03&NewsCommand= http://www.tpub.com/content/aviation/14018/css/14018_178.htm
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Problems with HydraulicsHeavy
High maintenance
Adds cost and creates a logistics problemRequires space (pumps, hydraulic lines, etc.)
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Possible Improvements
Electric ActuatorsConsists of a small electric motor, pump and
actuator ram requiring about 1 pint of hydraulicfluid
Flight tested by NASAs Dryden Flight ResearchCenter on a modified F-18.Provides significant weight savings by
eliminating pumps and hydraulic lines
Also could decrease required maintenance
Reference: NASA Dryden Flight Research Center. News
Release 98-84
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ec ro ec an caActuator
Reference: Air Force Research Laboratory
http://www.afrlhorizons.com/Briefs/0006/VA9902.html
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Impact on DesignNeed to allow sufficient space for required
hydraulic systems
Weight of the system must be accounted for
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Hydraulics
hydraulics [h drlliks ] nounstudy of fluids: the study of water or
other fluids at rest or in motion,especially with respect to
engineering applications
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Hydraulics used in many applications:Steering/control systems (rudder, planes)Deck machinery (anchor windlass, capstans,
winches)Masts & antennae on submarinesWeapons systems (loading & launching)
Other: elevators, presses
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Hydraulic TheoryHydraulicsCovers the physical behavior of liquids in
motion
Pressurized oil used to gain mechanicaladvantage and perform work
Important PropertiesShapelessness
IncompressibilityTransmission of Force
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Important Properties
ShapelessnessLiquids have no neutral formConform to shape of containerEasily transferred through piping from one
location to another
IncompressibilityLiquids are essentially incompressibleOnce force is removed, liquid returns to
original volume (no permanent distortion)
Transmission of ForceForce is transmitted equally & undiminishedin every direction -> vessel filled with
pressure
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Hydraulic TheoryPascals Law
Magnitude of force transferred is in directproportion to the surface area (F = P*A)
Pressure = Force/Area
Liquid properties enable large objects (rudder,planes, etc) to be moved smoothly
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Hydraulic Mechanical
Advantage F2 =
F1 = 20 lbf
A1 = 2 in2
A1 = 20 in2
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Basic Hydraulic SystemHydraulic FluidUsually oil (2190 TEP)
Pressure SourceHydraulic pump (A-end of system)
Pressure userHydraulic motor (B-end of system)
Piping system (w/ valves, tanks, etc)Get fluid from A-end to B-end
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Hydraulic Pump (A-End)Pumps can be positive displacement orcentrifugal
Waterbury pump Variable-stroke pistonpump
Tilting box can tiltfwd/aft while pumprotates
Angle of tilting box
determines capacity and
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Hydraulic Pump (A-End) Variable-stroke piston pumpTilting box can tilt fwd/aft while pump rotates Angle of tilting box determines capacity and
dir. of flow
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Cylinder/Motor (B-end)
Piston/cylinder used if desired motion islinearHydraulic pressure moves piston & ramLoad is connected to ram (rudder, planes,
masts, periscopes)
PistonCylinder
RAM
Hydraulic Fluid Supply/Return Ports
Seal
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Cylinder/Motor (B-end)Motor used if desiredmotion is rotaryEssentially a variable-
stroke pump inreverseUsed for capstan,
anchor windlass, etc
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Piping SystemHas to withstand excessive pressure
Valves, filters, & HXs all necessary
AccumulatorsHolds system under pressure (w/out contin.
pump)Provides hydraulics when pump off/lost
Compensates for leakage/makeup volumeTypes: piston, bladder, & direct contact
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Accumulator Types
PistonMost common
BladderGun mountsSteering
systems
Direct contactLeast common
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Advantages
Convenient power transferFew moving partsLow losses over long distancesLittle wear
FlexibilityDistribute force in multiple directionsSafe and reliable for many usesCan be stored under pressure for long
periodsVariable speed control
Quick response (linear and rotary)
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DisadvantagesRequires positive confinement (to give shape)
Fire/explosive hazard if leaks or ruptures
Filtration critical - must be free of debrisManpower intensive to clean up
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Electrohydraulic Drive
SystemUses hydraulics to transfer power from electricmotor to load
Rotary: Waterbury pump connected to rotary piston
hydraulic motor (speed gear)Tilting box of A-end controls direction/speed of B-endAdv: high starting torque, reversibility, high power-to-
weight ratio
ex: Electrohydraulic Speed Gear or Steering Gearcapstan, anchor windlass, cranes, elevator, ammo hoist
E ectro y rau c Spee
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E ectro y rau c SpeeGear
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Electrohydraulic Steering
GearSame as speed gear except B-end is ahydraulic cylinder to produce linear motion
Waterbury pumps connected by piping tohydraulic ram cylinderVarious methods for connecting rams to tillersTwo pumps for redundancy & reliability
Movement of steering wheel through hydraulicsystem moves rudder
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Gear
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Control of SystemRemote controlNormal methodControl from bridge
EmergencyTake local controlManually position control surface/rudder
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Power
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HYDR. MOTOR
TORQUE TUBE
GEARBOX
Power
Landing gear Extension, retraction, locking, steering, braking
Primary flight controls Rudder, elevator, aileron, active (multi-function)
spoiler
Secondary flight controls
high lift (flap / slat), horizontal stabilizer, spoiler,thrust reverser
Utility systems Cargo handling, doors, ramps, emergency
electrical power generation
Flap DriveSpoiler Actuator
Landing Gear
Nosewheel Steering
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Power
Mechanical Engine Driven Pump (EDP) - primary hydraulic power source,
mounted directly to engines on special gearbox pads Power Transfer Unit mechanically transfers hydraulic
power between systems
Electrical Pump attached to electric motors, either AC or DC Generally used as backup or as auxiliary power Electric driven powerpack used for powering actuation zones Used for ground check-out or actuating doors when
engines are not running
Pneumatic Bleed Air turbine driven pump used for backup power Ram Air Turbine driven pump deployed when all engines
are inoperative and uses ram air to drive the pump Accumulator provides high transient power by releasing
stored energy, also used for emergency and parking brake
Ram Air Turbine
AC Electric Motorpump
Maintenance-free
Accumulator
Engine Driven Pump
Power Transfer Unit
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Key Hydraulic System Design
DriversHigh Level certification requirement per aviation
regulations:Maintain control of the aircraft under all normal and
anticipated failure conditions
Many system architectures* and design approachesexist to meet this high level requirement aircraftdesigner has to certify to airworthiness regulators byanalysis and test that his solution meets requirements
* Hydraulic System Architecture:Arrangement and interconnection of hydraulic power sourcesand consumers in a manner that meets requirements forcontrollability of aircraft
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Considerations for Hydraulic System Designto meet System Safety RequirementsRedundancy in case of failures must be
designed into system Any and every component will fail during
life of aircraft Manual control system requires less
redundancyFly-by-wire (FBW) requires more
redundancy Level of redundancy necessary evaluated
per methodology described in ARP4761
Safety Assessment Tools Failure Modes, Effects and Criticality
Analysis computes failure rates and failurecriticalities of individual components andsystems by considering all failure modes
Fault Tree Analysis computes failure ratesand probabilities of various combinations offailure modes
Markov Analysis computes failure ratesand criticality of various chains of events
Common Cause Analysis evaluatesfailures that can impact multiplecomponents and systems
Principal failure modes considered Single system or component failure Multiple system or component failures
occurring simultaneously Dormant failures of components or
subsystems that only operate in emergencies Common mode failures single failures that
can impact multiple systems
Examples of failure cases to be considered One engine shuts down during take-off need
to retract landing gear rapidly Engine rotor bursts damage to and loss of
multiple hydraulic systems Rejected take-off deploy thrust reversers,
spoilers and brakes rapidly All engines fail in flight need to land safely
without main hydraulic and electric powersources
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Civil Aircraft System Safety Standards(Applies to all aircraft systems)
Failure
Criticality Failure Characteristics
Probability of
Occurrence
Design
Standard
Minor Normal, nuisance and/or possibly requiringemergency procedures
Reasonably
probableNA
Major Reduction in safety margin, increased crewworkload, may result in some injuries
Remote P 10-5
Hazardous Extreme reduction in safety margin, extendedcrew workload, major damage to aircraft and
possible injury and deaths
Extremely remote P 10-7
Catastrophic Loss of aircraft with multiple deaths Extremelyimprobable
P 10-9
Examples
Minor: Single hydraulic system fails
Major: Two (out of 3) hydraulic systems fail
Hazardous: All hydraulic sources fail, except RAT or APU
System Design
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System DesignPhilosophyConventional Central System ArchitectureMultiple independent centralized
power systemsEach engine drives dedicated pump(s),
augmented by independently poweredpumps electric, pneumatic
No fluid transfer between systems to
maintain integritySystem segregation
Route lines and locate components farapart to prevent single rotor or tireburst from impacting multiple systems
Multiple control channels for criticalfunctions
Each flight control needs multipleindependent actuators or controlsurfaces
Fail-safe failure modes e.g., landinggear can extend by gravity and belocked down mechanically
LEFT ENG.
SYSTEM 1
SYSTEM 3 RIGHT ENG.
SYSTEM 2
EDP EDP
ROLL 1
PITCH 1
YAW 1
OTHERS
EMP
EMP RAT
PTU
ROLL 2
PITCH 2
YAW 2
OTHERS
EMP
ROLL 3
PITCH 3
YAW 3
LNDG GR
EMRG BRKNORM BRK
NSWL STRG
ADP
EDP Engine Driven Pump
EMP Electric Motor Pump
ADP Air Driven Pump
PTU Power Transfer Unit
RAT Ram Air Turbine
Engine Bleed Air
OTHERS
System Design
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System DesignPhilosophyMore Electric ArchitectureTwo independent centralized power
systems + Zonal & DedicatedActuatorsEach engine drives dedicated pump(s),
augmented by independently poweredpumps electric, pneumatic
No fluid transfer between systems tomaintain integrity
System segregationRoute lines and locate components far
apart to prevent single rotor or tire burstto impact multiple systems
Third System replaced by one or morelocal and dedicated electric systems
Tail zonal system for pitch, yawAileron actuators for rollElectric driven hydraulic powerpack for
emergency landing gear and brake
Examples: Airbus A380, Boeing 787
LEFT ENG.
SYSTEM 1
RIGHT ENG.
SYSTEM 2
EDP EDP
ROLL 1
PITCH 1
YAW 1
OTHERS
EMP
GEN1 RAT
ROLL 2
PITCH 2
YAW 2
OTHERS
EMP
ROLL 3
ZONALPITCH 3 YAW
3
NORM BRK
EMRG BRKLNDG GR
NW STRG
GEN2
EDP Engine Driven Pump
EMP Electric Motor Pump
GEN Electric Generator
RAT Ram Air Turbine Generator
Electric Channel
OTHERS
ELECTRICAL
ACTUATORS
LG / BRKEMERG
POWER
System Design
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System DesignPhilosophyAll Electric Architecture
Holy Grail of aircraft power distribution .Relies on future engine-core mounted electric generators
capable of high power / high power density generation,
running at engine speed typically 40,000 rpmElectric power will replace all hydraulic and pneumatic
power for all flight controls, environmental controls, de-icing, etc.
Flight control actuators will like remain hydraulic, using
Electro-Hydrostatic Actuators (EHA) or local hydraulicsystems, consisting ofMiniature, electrically driven, integrated hydraulic power
generation system
Hydraulic actuator controlled by electrical input
y y re
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y- y- reSystems
Fly-by-Wire
Pilot input read by computersComputer provides input to electrohydraulicflight control actuator
Control laws include Enhanced logic to automate many functions Artificial damping and stability Flight Envelope Protection to prevent airframe
from exceeding structural limits
Multiple computers and actuators provide
sufficient redundancy no manual reversion
Conventional MechanicalPilot input mechanically connected to flight
control hydraulic servo-actuator by cables,linkages, bellcranks, etc.
Servo-actuator follows pilot command with highforce output
Autopilot input mechanically summed
Manual reversion in case of loss of hydraulics orautopilot malfunction
BOEING 757 AILERON SYSTEM
PILOT INPUTS
AUTOPILOT INPUTS
LEFT WING
RIGHT WING
Interfaces
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InterfacesDesign Considerations
Hydraulic System
Hydraulic power from EDP-
Engine
Nacelle / Engine
Pad speed as a function of
flight regime idle to take-off
Landing Gear
Power on Demand
Flow under normal and all
emergency conditions
retract / extend / steer
Electric motors, Solenoids
Electrical System
Electrical power variations
under normal and all
emergency conditions
(MIL-STD-704)
Flight Controls
Power on Demand
Flow under normal and
all emergency conditions
priority flow when LG,
flaps are also
demanding flow
Avionics
Signals from pressure,
temperature, fluid quantity sensors
Signal to solenoids, electric motors
Architectures
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1,000
10,000
100,000
1,000,000
10,000,000
Cessna17
2
Phenom10
0
KingAir20
0
Learjet4
5
BAeJ
etstre
am4
1
Learjet8
5
Hawk
er400
0
Challen
ger60
5
Falco
nF7X
Glob
alXRS
Gulfstre
amG65
0
Embr
aerE
RJ-195
Boein
g737-70
0
Airbu
sA321
Boein
g757-30
0
Airbu
sA330-30
0
Boein
g777
-300E
R
Boein
g747
-400E
R
Airbu
sA380
MTOW-lb
LARGE BIZ / REGIONAL JETS
SINGLE-AISLE
WIDEBODY
MID / SUPER MID-SIZE BIZ JETS /
COMMUTER TURBO-PROPS
VERY LIGHT / LIGHT JETS / TURBO-PROPS
GENERAL AVIATION
ArchitecturesComparative Aircraft Weights
Increasing Hydraulic System Complexity
Architectures
Mid-Size Jet
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ArchitecturesExample Block Diagrams Learjet 40/45
MAIN SYSTEM EMERGENCY SYSTEMMTOW: 21,750 lb
Flight Controls: Manual
Key Features One main system fed by 2 EDPs Emergency system fed by DC electric pump Common partitioned reservoir (air/oil) Selector valve allows flaps, landing gear, nosewheel
steering to operate from main oremergency system All primary flight controls are manual
Safety / Redundancy Engine-out take-off: One EDP has sufficient power
to retract gear All Power-out: Manual flight controls; LG extends by
gravity with electric pump assist; emergency flap
extends by electric pump; Emergency brake energy
stored in accumulator for safe stopping
REF.: AIR5005A (SAE)
hi
Super Mid Size
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ArchitecturesExample Block Diagrams Hawker 4000
MTOW: 39,500 lb
Flight Controls: Hydraulic with manualreversion exc. Rudder, which is Fly-by-Wire (FBW)
Key FeaturesTwo independent systemsBi-directional PTU to transfer power between
systems without transferring fluidElectrically powered hydraulic power-pack for
Emergency Rudder System (ERS)
Safety / RedundancyAll primary flight controls 2-channel; rudder has
additional backup powerpack; others manualreversion
Engine-out take-off: PTU transfers power fromsystem #1 to #2 to retract LG
Rotorburst: Emergency Rudder System islocated outside burst area
All Power-out: ERS runs off battery; others
manual; LG extends by gravity
REF.: EATON C5-38A 04/2003
Single-Aisle
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Aircraft Hydraulic ArchitecturesExample Block Diagrams Airbus A320/321
MTOW (A321): 206,000 lb
Flight Controls:HydraulicFBW
Key Features3 independent systems2 main systems with EDP
1 main system also includes backup EMP& hand pump for cargo door3rd system has EMP and RAT pump
Bi-directional PTU to transfer powerbetween primary systems withouttransferring fluid
Safety / RedundancyAll primary flight controls have 3
independent channelsEngine-out take-off: PTU transfers power
from Y to G system to retract LGRotorburst: Three systems sufficiently
segregatedAll Power-out: RAT pump powers Blue;
LG extends by gravity
REF.: AIR5005 (SAE)
ArchitecturesWide Body
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ArchitecturesExample Block Diagrams Boeing 777
MTOW (B777-300ER): 660,000 lb
Flight Controls: Hydraulic FBW
Key Features3 independent systems2 main systems with EDP + EMP each3rd system with 2 EMPs, 2 engine bleed
air-driven (engine bleed air) pumps, +RAT pump
Safety / RedundancyAll primary flight controls have 3
independent channelsEngine-out take-off: One air driven pump
and EMP available in system 3 to retractLG
Rotorburst: Three systems sufficientlysegregated
All Power-out: RAT pump powers centersystem; LG extends by gravity
LEFT SYSTEM RIGHT SYSTEMCENTER SYSTEM
REF.: AIR5005 (SAE)
ArchitecturesWide Body
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ArchitecturesExample Block Diagrams Airbus A380
MTOW: 1,250,000 lb
Flight Controls: FBW (2H + 1Echannel)
Key Features / RedundanciesTwo independent hydraulic systems
+ one electric system (backup)Primary hydraulic power supplied by 4
EDPs per systemAll primary flight controls have 3
channels 2 hydraulic + 1 electric
4 engines provide sufficientredundancy for engine-out cases
REF.: EATON C5-37A 06/2006
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Aircraft hydraulic systems are designed forhigh levels of safety using multiple levels ofredundancy
Fly-by-wire systems require higher levels ofredundancy than manual systems to maintainsame levels of safety
System complexity increases with aircraftweight
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Suggested ReferencesFederal Aviation RegulationsFAR Part 25: Airworthiness Standards forTransport Category Airplanes
FAR Part 23: Airworthiness Standards forNormal, Utility, Acrobatic, and CommuterCategory Airplanes
FAR Part 21: Certification Procedures ForProducts And Parts
AC 25.1309-1A System Design and AnalysisAdvisory Circular, 1998
Aerospace Recommended Practices (SAE)
ARP4761: Guidelines and Methods forConducting the Safety Assessment Processon Civil Airborne Systems and Equipment
ARP 4754: Certification Considerations forHighly-Integrated or Complex AircraftSystems
Aerospace Information Reports (SAE)AIR5005: Aerospace - Commercial Aircraft
Hydraulic Systems
Radio Technical Committee Association (RTCA)DO-178: Software Considerations in
Airborne Systems and EquipmentCertification (incl. Errata Issued 3-26-99)
DO-254: Design Assurance Guidance ForAirborne Electronic Hardware
TextMoir & Seabridge: Aircraft Systems
Mechanical, Electrical and AvionicsSubsystems Integration 3rd Edition,Wiley 2008