7/28/2019 b-9-hyd120313-w11

1/54

WELCOME

7/28/2019 b-9-hyd120313-w11

2/54

Introduction,Aerospace Engineering

Pre RequisitesAircraft

Professions

Global Aviation Industries.

7/28/2019 b-9-hyd120313-w11

3/54

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

7/28/2019 b-9-hyd120313-w11

4/54

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

7/28/2019 b-9-hyd120313-w11

5/54

MotionPrimary Flight Controls

Definition of Airplane Axes

1 Ailerons control roll

2 Elevators control pitch3 Rudder controls yaw

1

3 2

7/28/2019 b-9-hyd120313-w11

6/54

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

7/28/2019 b-9-hyd120313-w11

7/54

Example of Flight

Controls (A320)

REF: A320 FLIGHT CREW OPERATING

MANUAL CHAPTER 1.27 - FLIGHT

CONTROLSPRIMARY

SECONDARY

7/28/2019 b-9-hyd120313-w11

8/54

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

7/28/2019 b-9-hyd120313-w11

9/54

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

7/28/2019 b-9-hyd120313-w11

10/54

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.

7/28/2019 b-9-hyd120313-w11

11/54

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

http://aerospace.eaton.com/news.asp?articledate=06/01/03&NewsCommand=ViewMonthhttp://aerospace.eaton.com/news.asp?articledate=06/01/03&NewsCommand=ViewMonth

7/28/2019 b-9-hyd120313-w11

12/54

Problems with HydraulicsHeavy

High maintenance

Adds cost and creates a logistics problemRequires space (pumps, hydraulic lines, etc.)

7/28/2019 b-9-hyd120313-w11

13/54

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

7/28/2019 b-9-hyd120313-w11

14/54

ec ro ec an caActuator

Reference: Air Force Research Laboratory

http://www.afrlhorizons.com/Briefs/0006/VA9902.html

7/28/2019 b-9-hyd120313-w11

15/54

Impact on DesignNeed to allow sufficient space for required

hydraulic systems

Weight of the system must be accounted for

7/28/2019 b-9-hyd120313-w11

16/54

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

http://dictionary.msn.com/find/pronkey.asp?refid=1861619380http://dictionary.msn.com/find/pronkey.asp?refid=1861619380

7/28/2019 b-9-hyd120313-w11

17/54

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

7/28/2019 b-9-hyd120313-w11

18/54

Hydraulic TheoryHydraulicsCovers the physical behavior of liquids in

motion

Pressurized oil used to gain mechanicaladvantage and perform work

Important PropertiesShapelessness

IncompressibilityTransmission of Force

7/28/2019 b-9-hyd120313-w11

19/54

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

7/28/2019 b-9-hyd120313-w11

20/54

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

7/28/2019 b-9-hyd120313-w11

21/54

Hydraulic Mechanical

Advantage F2 =

F1 = 20 lbf

A1 = 2 in2

A1 = 20 in2

7/28/2019 b-9-hyd120313-w11

22/54

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

7/28/2019 b-9-hyd120313-w11

23/54

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

7/28/2019 b-9-hyd120313-w11

24/54

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

7/28/2019 b-9-hyd120313-w11

25/54

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

7/28/2019 b-9-hyd120313-w11

26/54

Cylinder/Motor (B-end)Motor used if desiredmotion is rotaryEssentially a variable-

stroke pump inreverseUsed for capstan,

anchor windlass, etc

7/28/2019 b-9-hyd120313-w11

27/54

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

7/28/2019 b-9-hyd120313-w11

28/54

Accumulator Types

PistonMost common

BladderGun mountsSteering

systems

Direct contactLeast common

7/28/2019 b-9-hyd120313-w11

29/54

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)

7/28/2019 b-9-hyd120313-w11

30/54

DisadvantagesRequires positive confinement (to give shape)

Fire/explosive hazard if leaks or ruptures

Filtration critical - must be free of debrisManpower intensive to clean up

7/28/2019 b-9-hyd120313-w11

31/54

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

7/28/2019 b-9-hyd120313-w11

32/54

E ectro y rau c SpeeGear

7/28/2019 b-9-hyd120313-w11

33/54

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

7/28/2019 b-9-hyd120313-w11

34/54

Gear

7/28/2019 b-9-hyd120313-w11

35/54

Control of SystemRemote controlNormal methodControl from bridge

EmergencyTake local controlManually position control surface/rudder

7/28/2019 b-9-hyd120313-w11

36/54

Power

7/28/2019 b-9-hyd120313-w11

37/54

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

7/28/2019 b-9-hyd120313-w11

38/54

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

7/28/2019 b-9-hyd120313-w11

39/54

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

7/28/2019 b-9-hyd120313-w11

40/54

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

7/28/2019 b-9-hyd120313-w11

41/54

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

7/28/2019 b-9-hyd120313-w11

42/54

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

7/28/2019 b-9-hyd120313-w11

43/54

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

7/28/2019 b-9-hyd120313-w11

44/54

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

7/28/2019 b-9-hyd120313-w11

45/54

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

7/28/2019 b-9-hyd120313-w11

46/54

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

7/28/2019 b-9-hyd120313-w11

47/54

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

7/28/2019 b-9-hyd120313-w11

48/54

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

7/28/2019 b-9-hyd120313-w11

49/54

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

7/28/2019 b-9-hyd120313-w11

50/54

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

7/28/2019 b-9-hyd120313-w11

51/54

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

7/28/2019 b-9-hyd120313-w11

52/54

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

7/28/2019 b-9-hyd120313-w11

53/54

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

7/28/2019 b-9-hyd120313-w11

54/54

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