ms2-ieee hyd systems presentation

5/24/2018 MS2-IEEE Hyd Systems Presentation

1/27 2008 Eaton Corporation. All rights reserved.

Aircraft Hydraulic System Design

Peter A. Stricker, PEProduct Sales Manager

Eaton Aerospace Hydraulic Systems Division

August 20, 2010


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Purpose

Acquaint participants with hydraulic system

design principles for civil aircraft

Review examples of hydraulic system

architectures on common aircraft


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Agenda

Introduction

Review of Aircraft Motion Controls

Uses for and sources of hydraulic power

Key hydraulic system design drivers

Safety standards for system design

Hydraulic design philosophies for conventional, more

electric and all electric architectures

Hydraulic System Interfaces

Sample aircraft hydraulic system block diagrams

Conclusions


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Introduction

As airplanes grow in size, so

do the forces needed to move the

flight 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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Introduction

Aircrafts Maximum Take-Off Weight (MTOW) drives

aerodynamic forces that drive control surface size and loading

A3801.25 million lb MTOWextensive use of hydraulics

Cessna 1722500 lb MTOWno hydraulicsall manual


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Controlling Aircraft MotionPrimary Flight Controls

Definition of Airplane Axes

1 Ailerons control roll

2 Elevators control pitch

3 Rudder controls yaw

3 2


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Controlling Aircraft MotionSecondary 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 wing

Ground 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 CONTROLS

PRIMARY

SECONDARY


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Why use Hydraulics?

Effective and efficient method of power amplification Small control effort results in a large power output

Precise control of load rate, position and magnitude Infinitely variable rotary or linear motion control

Adjustable limits / reversible direction / fast response Ability to handle multiple loads simultaneously

Independently in parallel or sequenced in series

Smooth, vibration free power output Little impact from load variation

Hydraulic fluid transmission medium Removes heat generated by internal losses

Serves as lubricant to increase component life


10/2710

HYDR. MOTOR

TORQUE TUBE

GEARBOX

Typical Users of Hydraulic 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, thrustreverser

Utility systems

Cargo handling, doors, ramps, emergency electrical

power generation

Flap DriveSpoiler Actuator

Landing Gear

Nosewheel Steering


11/2711

Sources of Hydraulic Power

Ram Air Turbine

AC Electric Motorpump

Maintenance-free

Accumulator

Engine Driven Pump

Mechanical

Engine Driven Pump (EDP) - primary hydraulic power source,mounted directly to engines on special gearbox pads

Power Transfer Unitmechanically transfers hydraulicpower 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 enginesare inoperative and uses ram air to drive the pump

Accumulator provides high transient power by releasingstored energy, also used for emergency and parking brake

Power Transfer Unit


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Key Hydraulic System Design Drivers

High Level certification requirement per aviation

regulations:

Maintain con trol of th e aircraft under al l norm al and

antic ipated fai lure con dit ions

Many system architectures*and design approachesexist to meet this high level requirementaircraft

designer has to certify to airworthiness regulators by

analysis and test that his solution meets requirements

* Hydraulic System Architecture:

Arrangement and interconnection of hydraulic power sources

and consumers in a manner that meets requirements for

controllability of aircraft


13/2713

Considerations for Hydraulic System Designto meet System Safety Requirements

Redundancy in case of failures must bedesigned into system

Any and every component will fail during life ofaircraft

Manual control system requires lessredundancyFly-by-wire (FBW) requires more redundancy

Level of redundancy necessary evaluated per

methodology described in ARP4761 Safety Assessment Tools

Failure Modes, Effects and Criticality Analysiscomputes failure rates and failure criticalities ofindividual components and systems byconsidering all failure modes

Fault Tree Analysiscomputes failure ratesand probabilities of various combinations offailure modes

Markov Analysiscomputes failure rates andcriticality of various chains of events

Common Cause Analysisevaluates failuresthat can impact multiple components andsystems

Principal failure modes considered Single system or component failure

Multiple system or component failures occurringsimultaneously

Dormant failures of components or subsystemsthat only operate in emergencies

Common mode failuressingle failures thatcan impact multiple systems

Examples of failure cases to be considered One engine shuts down during take-offneed

to retract landing gear rapidly

Engine rotor burstsdamage to and loss ofmultiple hydraulic systems

Rejected take-offdeploy thrust reversers,spoilers and brakes rapidly

All engines fail in flightneed to land safelywithout main hydraulic and electric power

sources


14/2714

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

probable

NA

Major Reduction in safety margin, increased crewworkload, may result in some injuries

Remote P 10-5

Hazardous Extreme reduction in safety margin, extended

crew 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 (US1549 Hudson River A3202009)

Catastrophic: All hydraulic systems fail (UA232 DC-10 Sioux City1989)


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System Design PhilosophyConventional Central System Architecture

Multiple independent centralized powersystems

Each engine drives dedicated pump(s),augmented by independently poweredpumpselectric, pneumatic

No fluid transfer between systems tomaintain integrity

System segregation Route lines and locate components far

apart to prevent single rotor or tire burstfrom impacting multiple systems

Multiple control channels for criticalfunctions

Each flight control needs multiple

independent actuators or controlsurfaces

Fail-safe failure modese.g., landinggear can extend by gravity and be lockeddown 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 PumpADPAir Driven Pump

PTU Power Transfer Unit

RAT Ram Air TurbineEngine Bleed Air

OTHERS


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System Design PhilosophyMore Electric Architecture

Two independent centralized powersystems + Zonal & Dedicated

Actuators

Each engine drives dedicated pump(s),augmented by independently poweredpumpselectric, pneumatic

No fluid transfer between systems to

maintain integrity System segregation

Route lines and locate components farapart 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, yaw Aileron actuators for roll

Electric driven hydraulic powerpack foremergency 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

GENElectric Generator

RAT Ram Air Turbine Generator

Electric Channel

OTHERS

ELECTRICAL

ACTUATORS

LG / BRKEMERG

POWER


17/27

17

System Design PhilosophyAll 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 speedtypically 40,000 rpm

Electric power will replace all hydraulic and pneumatic powerfor all flight controls, environmental controls, de-icing, etc.

Flight control actuators will like remain hydraulic, using

Electro-Hydrostatic Actuators (EHA) or local hydraulic

systems, consisting of

Miniature, electrically driven, integrated hydraulic power

generation system

Hydraulic actuator controlled by electrical input


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18

Fly-by-Wire (FBW) Systems

Fly-by-Wire

Pilot input read by computers Computer provides input to electrohydraulic flight

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

redundancyno manual reversion

Conventional Mechanical

Pilot input mechanically connected to flight controlhydraulic servo-actuator by cables, linkages,

bellcranks, etc.

Servo-actuator follows pilot command with high

force output

Autopilot input mechanically summed

Manual reversion in case of loss of hydraulics or

autopilot malfunction

BOEING 757 AILERON SYSTEM

PILOT INPUTS

AUTOPILOT INPUTS

LEFT WING

RIGHT WING


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19

Principal System InterfacesDesign Considerations

Hydraulic System

Hydraulic power from EDP

Nacelle / Engine

Pad speed as a function of

flight regimeidle 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


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20

1,000

10,000

100,000

1,000,000

10,000,000

Cessna

172

Phen

om100

KingAir200

Learj

et45

BAeJ

etstre

am41

Learj

et85

Hawk

er4000

Challen

ger605

Falco

nF7X

GlobalXRS

Gulfstre

amG650

Embr

aerE

RJ-195

Boein

g737

-700

Airbu

sA321

Boein

g757

-300

Airbu

sA330-300

Boein

g777

-300ER

Boein

g747-400ER

Airbu

sA380

M

TOW-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

Aircraft Hydraulic ArchitecturesComparative Aircraft Weights

Increasing Hydraulic System Complexity

Mid Si e Jet


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21

Aircraft Hydraulic ArchitecturesExample Block Diagrams Learjet 40/45

MAIN SYSTEM EMERGENCY SYSTEMMTOW: 21,750 lbFlight 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 or emergencysystem 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 energystored in accumulator for safe stopping

REF.: AIR5005A (SAE)

Mid-Size Jet

Super Mid Size


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22

Aircraft Hydraulic ArchitecturesExample Block Diagrams Hawker 4000

MTOW: 39,500 lb

Flight Controls: Hydraulic with manual reversionexc. Rudder, which is Fly-by-Wire (FBW)

Key Features

Two independent systems

Bi-directional PTU to transfer power betweensystems without transferring fluid

Electrically powered hydraulic power-pack forEmergency Rudder System (ERS)

Safety / Redundancy

All primary flight controls 2-channel; rudder hasadditional backup powerpack; others manualreversion

Engine-out take-off: PTU transfers power fromsystem #1 to #2 to retract LG

Rotorburst: Emergency Rudder System is locatedoutside burst area

All Power-out: ERS runs off battery; others manual;

LG extends by gravity

Super Mid Size

REF.: EATON C5-38A 04/2003

Single Aisle


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23

Aircraft Hydraulic ArchitecturesExample Block Diagrams Airbus A320/321

MTOW (A321): 206,000 lb

Flight Controls: HydraulicFBWKey Features

3 independent systems

2 main systems with EDP1 main system also includes backup EMP &hand pump for cargo door3rdsystem has EMP and RAT pump

Bi-directional PTU to transfer power betweenprimary systems without transferring fluid

Safety / Redundancy All primary flight controls have 3 independent

channels

Engine-out take-off: PTU transfers power fromY to G system to retract LG

Rotorburst: Three systems sufficientlysegregated

All Power-out: RAT pump powers Blue; LGextends by gravity

Single-Aisle

REF.: AIR5005 (SAE)

Wide Body
http://www.airliners.net/photo/Delta-Air-Lines/Airbus-A320-212/1684554/&sid=03a40fcf2808dd1522dd7e93ba740a32


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24

Aircraft Hydraulic ArchitecturesExample Block Diagrams Boeing 777

LEFT SYSTEM

Wide Body

RIGHT SYSTEMCENTER SYSTEMMTOW (B777-300ER): 660,000 lb

Flight Controls: Hydraulic FBWKey Features

3 independent systems

2 main systems with EDP + EMP each

3rdsystem with 2 EMPs, 2 engine bleed air-driven (engine bleed air) pumps, + RAT pump

Safety / Redundancy

All primary flight controls have 3 independentchannels

Engine-out take-off: One air driven pump andEMP available in system 3 to retract LG

Rotorburst: Three systems sufficientlysegregated

All Power-out: RAT pump powers centersystem; LG extends by gravity

REF.: AIR5005 (SAE)

Wide Body


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25

Aircraft Hydraulic ArchitecturesExample Block Diagrams Airbus A380

Wide Body

MTOW: 1,250,000 lb

Flight Controls: FBW (2H + 1E channel)

Key Features / Redundancies

Two independent hydraulic systems+ one electric system (backup)

Primary hydraulic power supplied by 4EDPs per system

All primary flight controls have 3 channels2 hydraulic + 1 electric

4 engines provide sufficient redundancyfor engine-out cases

REF.: EATON C5-37A 06/2006


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26

Conclusions

Aircraft hydraulic systems are designed for

high levels of safety using multiple levels of

redundancy

Fly-by-wire systems require higher levels ofredundancy than manual systems to maintain

same levels of safety

System complexity increases with aircraftweight


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Suggested References

Federal Aviation RegulationsFAR Part 25: Airworthiness Standards for

Transport Category Airplanes

FAR Part 23: Airworthiness Standards forNormal, Utility, Acrobatic, and CommuterCategory Airplanes

FAR Part 21: Certification Procedures For

Products And PartsAC 25.1309-1A System Design and

Analysis Advisory Circular, 1998

Aerospace Recommended Practices (SAE)ARP4761: Guidelines and Methods for

Conducting the Safety AssessmentProcess on Civil Airborne Systems andEquipment

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 3rdEdition, Wiley2008

ms2-ieee hyd systems presentation

Documents

theflight controls

flighttrim controls

control surface size

little effort4hydraulic

use hydraulics

augment ailerons

low speedwhen

permit steeperdescent