Airbus FBY Overview

October 2004

Presented by

Brian EndersbyManager Electromechanical Systems

Airbus Fly-By-Wire OverviewA318/A319/A320/A321

Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2

Monday, February 27, 12

Agenda Why Fly-By-Wire Airbus Fly-By-WireDesign

Objectives Design implementation Redundancy Dissimilarity Computer architecture

Fly-By-Wire control LawsPrinciple Pitch AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

control normal law Lateral control normal law

Fly-By-Wire protection Fly-By-Wire control law reconfiguration Control and indicatingAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Why Fly-By-WireIn 1983, Airbus launched the A320 with Fly-By Wire For Airbus Fly by Wire aircraftDifferent aircraft types have similar handling characteristics Flight envelope protection available Architecture simplified reduced maintenance, weight, cost

AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.


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Why Fly-By-WireIn 1983, Airbus launched the A320 with Fly-By Wire For Airbus Fly by Wire aircraftDifferent aircraft types have similar handling characteristics Flight envelope protection available Architecture simplified reduced maintenance, weight, cost


Difficult to deliver with mechanical Flight Control systemsAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Airbus Fly-By-Wire Design Objectives

Safety objectivesloss of roll control: loss of pitch control: loss of elevator control: THS runaway: extremely improbable extremely improbable extremely remote extremely improbable


Availability objectivesDispatch of the aircraft with one computer failed. One spoiler or one aileron servo control GO


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Airbus Fly-By-Wire Design implementationRedundancy at all levels(surfaces, power supplies, monitoring)



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Airbus Fly-By-Wire Design implementationRedundancy at all levels(surfaces, power supplies, monitoring)

Dissimilarity

hardware and software(avoid common mode failures)


Computer architecture

for failure detection/reconfiguration(Command Monitor )


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Airbus Fly-By-Wire Design considerationAll the surfaces are hydraulically actuated and electrically signalled Elevator Ailerons Slats Flaps * Rudder* Rudder & stabilizerhave back-up mechanical control

Spoilers AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

* Horizontal stabilizer


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Airbus Fly-By-Wire Design implementation Redundancy (A318-A319-A320-A321)Electrical generation and distribution

Generation

Two engine-driven generators One APU generator Two batteries One CSM / G (constant speed

motor/generator) driven by hydraulic circuit (Blue), powered by its dedicated pump or RAT

In case of electrical emergency configuration, two Fly-By AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

Wire computers are still powered and provide high level control law applied to minimise common point risks.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2

Additionally, extensive segregation rules have beenOctober 2004 Page


Airbus Fly-By-Wire Design implementation Redundancy (A318-A319-A320-A321)Hydraulic generation and distribution

Three Hydraulic circuits (Green , Blue, Yellow)

Green pressurized by an engine driven pump Yellow pressurized by an engine driven pump

electrical pump. Blue pressurized by an electrical pump and RAT. Green and yellow circuit can drive each other by means of the Power Transfer Unit (PTU)

and an

Two electro-hydraulic servo-controls per surface. AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

In case of double hydraulic failure, high level control lawstill available with remaining flight controls.


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Airbus Fly-By-Wire Design implementation Redundancy (A318-A319-A320-A321)Computer to actuator repartition

The electrical signalling of the flight control surfaces is achieved by 7digital computers.2

ELevator and Aileron Computers (ELAC) 3 Spoiler and Elevator Computers (SEC) 2 Flight Augmentation Computers (FAC)

Four computers available on elevator AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

Two specific computers are dedicated to manage the data from theflight control computers for indication, warnings, maintenance and recording purposes.2

Flight Control Data Concentrator (FCDC)October 2004 Page



Airbus Fly-By-Wire Design implementation Redundancy (A318-A319-A320-A321)



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Airbus Fly-By-Wire Design implementation Dissimilarity (A318-A319-A320-A321) Different types of computer to control the surfacesTwo Three Two

ELAC SEC FAC

Different micro-processors usedELAC: SEC: FAC:

3 Motorola 68000 2 Intel 80C86 2 Intel 80C286


Different software languages used for each computerchannel.C Assembler Dedicated one,

specifically developOctober 2004 Page



Airbus Fly-By-Wire Design implementation computer architecture Each computer which controls the surfaces has two functions:Flight control laws computation Surface servo loops control

Each computer is able:To To To

detect its internal failures inhibit its surface control signal its status

For each function (e.g. elevator control,etc) a priority order AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

exists between the computers for post failure reconfiguration logic.

All the computers are simultaneously activated to preventhidden failures , but only one command per function.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Airbus Fly-By-Wire Design implmentation computer architectureEach computer is has two independent, symmetrical and self monitoring channelsCOMMAND channel MONITOR channel



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Each channel : Computes the flight control laws Calculates the deflection commands Controls the actuator deflection Ensures engagement of post failure reconfiguration logic Performs monitoring Provides Power supply for transducers


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Each channel : Computes the flight control laws Calculates the deflection commands Controls the actuator deflection Ensures engagement of post failure reconfiguration logic Performs monitoring Provides Power supply for transducers Command & Monitor philosophy used to detect failures by comparing computed outputs are within predefined thresholds.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Airbus Fly-By-Wire Design considerations computer architectureP I L O T I N P U TS I D E S T I C K

FLIGHT CONTROL COMPUTER COMMAND Software 1 d COM C O N T R O L L E R ACTUAL d 1

d COM

ELECTROVALVE HYDRAULIC ACTUATOR 1 2


S Y S T E M

A D I R S S

MONITOR Software 2 d MON

ACTUAL d 2 DEFLECTION d of CONTROL SURFACE

d

I F N C P C U T etc.


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Airbus Fly-By-Wire Design implementation Mechanical back-up (A318, A319, A320, A321, A330-200, A330-300, A340-300)all safety objectives are fulfilled by redundancy, dissimilarity,system architecture In Addition A flight control mechanical back-up is provided:


For pitch control

For Yaw / roll control

Stabilise and control the aircraft during a temporary loss of all computers.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire control laws - Concept pilot stick input, to aircraft response, is called thecontrol law

The control law determines the handling characteristics ofthe aircraft.

The Control Law algorithm is optimised to obtain the bestaircraft performance throughout the flight envelope AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.


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Fly-By-Wire control laws - ConceptNon-fly-by-wire aircraftCONTROL COLUMN

Mechanical linkage

Surface deection

Fly-by-wire aircraft AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

SIDESTICK

FLIGHT CONTROL COMPUTER Pilot order

+ -

Surface deection order

Surface deection Aircraft response

FeedbackAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire control laws - ConceptFlt Control computers Control lawSYSTEM STATUS SIDESTICK Pilot order Electrical signal

NORMALSurface deection

ALTERNATE


DIRECT

Control law selected dependent upon Flight Control System statusAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire control laws - ConceptNormal and alternate lawSIDESTICKFLIGHT CONTROL COMPUTER Pilot order

+ -

Surface deection order


Feedback

Pilots input is converted into an A/C objective. No direct relationship between stick and surface. The aircraft is servo looped

Direct law AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

SIDESTICK

FLIGHT CONTROL COMPUTER Surface deection

Surface deflection order kinematic

Aircraft response

Pilots input is directly converted into surface deflection orders.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2

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Fly-By-Wire control laws - Concept

Control laws are modified to the flight phases and ground to air transition conditions.

Ground mode AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

Transition

Flight mode

Transition

Flare mode

Transition

Ground mode

Transitions are smooth


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Fly-By-Wire control laws Pitch control Forward or aft sidestick deflection results in a verticalload factor demand (G Load) / pitch rate.FLIGHT CONTROL COMPUTER G load demand

SIDESTICK

+ -

Elevator & THS deflection order


G Load / Pitch rate feedback

In short term, commanded flight path is maintainedElevator AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

and THS are automatically deflected to compensate for turbulences, thrust, configuration and speed changes. Aircraft is automatically and continuously trimmed (neutral static stability)

In long term, pilots action may be required to adjust flightpath as desired.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire control laws Pitch control



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Fly-By-Wire control laws Lateral control Lateral side stick deflection results in a roll rate demand.SIDESTICKFLIGHT CONTROL COMPUTER Roll rate demand e

+ -

Roll & Yaw deflection order


Roll Yaw rate / Bank Slide slip feedback

The roll rate is achieved by roll surfaces while rudder provides automaticturn coordination and yaw damping. AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

The aircraft is laterally stable: no aileron trim is required (neutral spiralstability) Roll and yaw surfaces are automatically deflected to cope with turbulences or aircraft asymmetry, using max deflection if required.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire control laws Lateral control



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Fly-By-Wire control lawsWithin the normal flight envelope regardless of altitude, speed, Cg or configuration,Aircraft Aircraft Loads

is stable: yet is highly maneuverable on demand response is precise and consistent about all axiss.

are controlled & monitored in both pitch and roll.



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Fly-By-Wire control lawsWithin the normal flight envelope regardless of altitude, speed, Cg or configuration,Aircraft Aircraft Loads

is stable: yet is highly maneuverable on demand response is precise and consistent about all axiss.

are controlled & monitored in both pitch and roll.


Resulting handling characteristics provide a safe, accurate and comfortable flight within the normal flight envelopeAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire protection A full set of protection is provided in case the normalwindshear, very high turbulences, midair collision avoidance manoeuvres, or GPWS, TCAS activation,

flight envelope is violated due to some extreme situation such as

Protection Function:Gives AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

full authority to pilot and achieves the best aircraft performance response Reduces the risk of over controlling / overstressing the aircraft Compatible with Pilot instinctive response to flight conditionsAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire protectionPitch attitudePitch limits

Load factor

Bank angle


Flight mode

Flare mode

Ground mode

High AOAAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2

AIR FLOW

High speedOctober 2004 Page


Fly-By-Wire protection Pitch attitude Design aim:To enhance the effectiveness of AOA and high speed protection in extreme conditions. Pitch authority is reduced at extreme attitudes.

Principle:


Nose-up Flaps 0 to 3 30 Flaps full 25

Nose down 15Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire protection Load factor Design aim:To minimize the probability to damage the aircraft structure when high maneuverability is needed + 2.5 g to - 1g in a clean configuration + 2 g to 0 g with slats/flaps extendedConventional A/CNz AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

G load

Limitations:

FBW A/C (normal or alternate control law)Nz 2.5 g Straight pilot's input

Cautious pilot's input

2.5 g g load A/C response

g load A/C response t0 Time t0 Time A/C time constantOctober 2004 Page

A/C time constant + pilot's reaction timeAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2


Fly-By-Wire protection Bank angle If side stick is released when the bank angleexceeds 33, the aircraft will return to and maintain 33 bank angle. bank angles up to 33.

Automatic pitch compensation provided for

AP disconnects and FD bars disappear when thebank is > 45, FD bars reappear when bank angle is < 40 (or 45 if AOA or high speed protection). AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

With full side stick bank angle is limited to 67 If high speed protection is operative, the positivespiral stability threshold starts from 0 and bank angle is limited to 45.October 2004 Page



Fly-By-Wire protection High speed Design aim:Protects the aircraft from exceeding VMO/MMO limit by introducing a positive load factor (nose-up demand) to the side stick


VMO/MMO limit


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Fly-By-Wire protection High Angle of Attack Design aim:To

introduce positive static stability at the low speed end of flight envelope To protect against stall, even in high dynamic manoeuvres or in gusts To provide the ability to reach and maintain a high CL, side stick full aft, without exceeding stall angle No interference with normal operating speeds and manoeuvres

Principle:When AOA greater

than AOA prot., a fwd/aft side stick input results in

an AOA demand AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

Results:AOA

prot. is maintained if side stick is left at neutral position AOA max is maintained if side stick is deflected fully aft


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Fly-By-Wire protection High Angle of Attack

CL

Angle of Attack (AOA) Stall : Sudden loss of lift and or aircraft control AIRBUS S.A.S. All rights reserved. Confidential and proprietary document.

Max: Angle of attack reached with full aft stick(max aircraft performance) Floor: Angle of attack, where TOGA thrust is automatically applied by the A/THR

Prot: Angle of attack from which stick input is converted into angle of attack demand (stick neutral Prot) VLS: Angle of attack reached at approach speed (VLS)Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Fly-By-Wire protection High Angle of Attack As speed decreases itreaches Vls, the lowest achievable speed with autothrust engaged

Between PROT & MAX, Floor will activate, autopilot disconnects and speed brakes automatically retract if extended



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Control law reconfiguration Normal LawPitch attitudePitch limits

Load factor

Bank angle Pitch normal lawPitch side stick = load factor demand


Roll normal lawRoll side stick = roll rate demand

Flare mode

Ground mode

High AOA

AIR FLOW

High speed

With any single failure, all protections remain availableAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Control law reconfiguration (A318-A319-A320-A321)Normal lawDouble or triple ADR failure Double self detected IR failure Double hydraulic failure Double FAC failure Double SFCC slat channel failure Yaw damper function loss Double aileron Double ELAC failure All spoilers loss Triple SEC failure THS jammed ELAC2 + hyd B ELAC1 + hyd G ELAC1 + hyd Y


Alternate LawsAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Control law reconfiguration Alternate Law(A318-A319-A320-A321) Pitch attitudePitch limits

Load factor

Bank angle Pitch normal lawPitch sidestick = load factor demand


Roll normal law Roll Direct law

Flare mode

Ground mode

High AOA

AIR FLOW

Stall warning

overspeedHigh speed stabilityOctober 2004

Overspeed warningPage

Low speed stabilityAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2


Control law reconfiguration (A318-A319-A320-A321)Normal lawDouble or triple ADR failure Double self detected IR failure Double hydraulic failure Double FAC failure Double SFCC slat channel failure Yaw damper function loss Double aileron Double ELAC failure All spoilers loss Triple SEC failure THS jammed ELAC2 + hyd B ELAC1 + hyd G ELAC1 + hyd Y Triple IRS failure Double IRS failure (2nd not self detected) Double R/A failure when landing gear down


Direct Laws

Landing gear down

Alternate LawsAirbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Control law reconfiguration Direct LawPitch attitudePitch limits

Load factor

Bank angle Pitch normal law Pitch direct law Roll normal law Roll direct law


Flare mode

Ground mode

High AOA

AIR FLOW

High speed The direct law provides the Handling characteristics of a natural Aircraft.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Control law reconfiguration Direct LawIn direct law, the aircraft is a natural aircraft with improved handling characteristics compared to a non fly-by-wire aircraft:SIDESTICKFLIGHT CONTROL COMPUTER Surface deection

Surface deflection order kinematic (CG, configuration)

Aircraft response

In pitch: The


elevator deflection is proportional to the stick deflection maximum deflection is a function of configuration and CG. The aircraft response is homogeneous regardless of configuration and CG. The pitch trim is manually controlled using trim wheel.

In roll: The

aileron / spoiler deflections depend upon the stick deflection and on aircraft configuration. The aircraft response is homogeneous regardless of configuration. Simple yaw damping and limited turn co-ordination are provided as a function of yaw rate and stick deflection.Airbus Fly-By-Wire Overview - EYDCC - Ref. D27PR0302099 - Issue 2 October 2004 Page


Control and indicating (A318-A319-A320-A321)



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This document and all information contained herein is the sole property of AIRBUS S.A.S. No intellectual property rights are granted by the delivery of this document or the disclosure of its content. This document shall not be reproduced or disclosed to a third party without the express written consent of AIRBUS S.A.S. This document and its content shall not be used for any purpose other than that for which it is supplied. The statements made herein do not constitute an offer. They are based on the mentioned assumptions and are expressed in good faith. Where the supporting grounds for these statements are not shown, AIRBUS S.A.S. will be pleased to explain the basis thereof.



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Documents

Airbus FBY Overview