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49J A N U A R Y 2 0 1 2

F L I G H T

A I R W O R T H I N E S S

S U P P O R T

T E C H N O L O G Y FAST

Publisher: Bruno PIQUET

Editor: Lucas BLUMENFELD

Page layout: Quat’coul

Cover: Radio AltimetersPicture from Hervé GOUSSE

ExM Company

Authorization for reprint of FAST Magazine articles should be requestedfrom the editor at the FAST Magazine e-mail address given below

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e-mail: [email protected]: Amadio

FAST Magazine may be read on Internethttp://www.airbus.com/support/publications

under ‘Quick references’ISSN 1293-5476

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Customer ServicesEvents

Spare part commonalityEnsuring A320neo series commonalitywith the existing A320 FamilyAndrew James MASONGraham JACKSON

BiomimicryWhen aircraft designers learn from natureDenis DARRACQ

Radio Altimeter systemsCorrect maintenance practicesSandra PREVOTIan GOODWIN

ELISE Consulting ServicesILS advanced simulation technologyLaurent EVAINJean-Paul GENOTTINBruno GUTIERRES

The ‘Clean Sky’ initiativeSetting the toneAxel KREINEric DAUTRIAT

AltimetersFrom barometric to radio

Customer Services WorldwideAround the clock... Around the world

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This issue of FAST Magazine has been printedon paper produced without using chlorine, to reducewaste and help conserve natural resources.Every little helps!

Photo copyright AirbusPhoto credits:

Airbus Photographic Library, ExM Company, Airbus France, Getty Images

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SPARE PART COMMONALITY - ENSURING A320NEO SERIES COMMONALITY WITH THE EXISTING A320 FAMILYFA

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Spare partcommonality

Ensuring A320neo series commonalitywith the existing A320 Family

Commonality is one of the key drivers of theA320neo development. The A320neo series,where neo stands for ‘new engine option’, has atarget of over 95% spare parts commonality withthe existing models, enabling the new aircraft tofit seamlessly into existing A320 Family fleetsand customers’ operations. This will help airlinesto achieve significant savings in the areas ofInitial Provisioning (IP) investment andmaintenance training, compared to an all newaircraft series.

The A320neo series is a programme which usesinnovative new engine and aero-structuraltechnologies to provide a significant improvementin performance for the A319, A320 and A321aircraft. Whilst striving to deliver this benefit tothe operators, Airbus is also keen on minimizingthe changes to a proven product. Changing onlywhat is necessary to integrate the new engines,keeping the rest of the aircraft in harmony withthe operators’ existing economic and logisticalmodels, can ensure the future operators a simpler,lower cost service entry.

Graham JACKSONA320neo OperabilityTechnical IntegratorAirbus Engineering

Andrew James MASONProject Manager New Programmes IP

Airbus Material, Logistics and Suppliers

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SPARE PART COMMONALITY - ENSURING A320NEO SERIES COMMONALITY WITH THE EXISTING A320 FAMILY

Key drivers of theA320neodevelopmentSpares’ investment and serviceshave a huge impact on the lifecyclecost of an aircraft. In recognition ofthis, Airbus has set clear targets forthe A320neo development to drivecost factors such as spares’investment and commonality du-ring the aircraft definition phase.This includes the specificobjectives on both commonalityand overall RSPL* investment.

OVERALL RSPL INVESTMENT

The overall RSPL investment wasset at the same level for theA320neo series as for the standardA320 Family aircraft. It was thenbroken down to individual com-ponents, in order to ensure thatboth component reliabilities andcontractual agreements withsuppliers don’t increase the overallquantity and cost of parts in theRSPL.

A3

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n o t e s

RSPL (Recommended Spare PartsList)Airbus provides customers withmaterial provisioning dataconcerning spares’ holdings fora given fleet based on customizedparameters. This list givesrecommendations for theunscheduled maintenance planningfor the first year of operation.


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COMMONALITY STUDIES

The 95% commonality of partsdefined in Airbus’ objectives is notjust a marketing figure. An initialverification exercise has beenconducted to ensure that it ismeasurable, achievable and valueadding. The following sectionsdefine how this was carried out.

Airbus has compared the standardengine variants, CFM (jointventure between General Electricand SNECMA) and IAE (Inter-national Aero Engines), with both‘neo’ engine variants - ‘CFM LeapX’ and ‘PW1100G’, as shown infigure 2. The operators of bothstandard engine variants haveexpressed an interest in both newengine options, meaning all fleetcombinations must be considered.

The technical scope of theassessment covers the wholeairframe, including all systemsimpacted by the introduction of thenew engines, but excluding theengines and nacelles themselves.The analysis does not considerstructural parts.

Generation of aRecommendedSpare Parts List(RSPL)To generate RSPLs as a basis ofcomparison, key assumptions weredefined relating to the fleet size,aircraft utilisation, logistics andeconomics. The assumptions arebased on experience with allAirbus operators and represent theaverage A320 Family mission.

Four RSPLs were generated basedupon the defined assumptions andusing the same methodology as atypical customized airline’s RSPLfor the following configurations:

• A320 CFM56-5B Variant,• A320 IAE V2500 Variant,• A321 CFM56-5B Variant,• A321 IAE V2500 Variant.

RecommendedSpare Parts List:Short-listingThe Recommended Spare PartsList contains a huge range ofdifferent parts from large assem-blies such as an APU (AuxiliaryPower Unit) to small ‘nuts andbolts’. It is critical to filter theseparts to get a representative view ofthe commonality, as hundreds ofsmall standard hardware partnumbers with very small financialimpact can falsify the results.

Airbus therefore considered thenumber of recommended parts,multiplied by the respective partnumber price, to determine thespares’ financial impact of each part.

Through this exercise, standardsimple items such as filters, lightbulbs, placards, seals, switches andsensors with little financial impact,are removed from the calculationallowing the exercise to focus onthe valuable and high impact items.

Airframe spare part commonality studyconsidering A320 with different engine variants

Figure 2

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Parts’commonalityidentificationThe commonality of each part onthe short-listed RSPL has beendetermined for the A320neo seriesbaseline designs for all enginevariants. The determined commo-nalities have been graded using thefollowing categories (see figure 3):

• 1. Fully common• 2. Partially common - hardwareonly common*• 3. Partially common -interchangeable (‘neo’ tostandard)• 4. Non-commonThe suitability of existing A320Family parts for application on the‘neo’ series is continuously beingassessed to capitalize on thecommonality opportunities.

n o t e s

Software update is required.It allows the existing hardwareto be embodied on both the preand post ‘neo’ aircraft series.

Figure 3

Parts commonality identification


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Commonalityfeasibility studyresultsThe percentage of commonalitybetween each pair of variants isvisible in figure 4.

In order to clearly determine thecommonality percentage, theresults were classified into twocategories, to reflect the requiredcustomer investment:

• Either, new hardware, including:- Parts which are completelydifferent,- Parts which are new for theA320neo but can also beretrofitted on the standardA320 Family aircraft.

• Or, common hardware,including:- Parts which are completely thesame,- Parts for which the hardware isthe same (enabled by asoftware upgrade).

SOME EXAMPLES

A320neo series’ commonality canbe seen on many of the controlcomputers such as the FAC (FlightAugmentation Computer), ELAC(Elevator Aileron Computer) andthe DMC (Display ManagementComputer), where the hardwarewill remain exactly the same,requiring only a software update toallow full compatibility with thenew engine options. The newsoftware will be such that onceloaded onto the part, it can beinstalled on either the ‘neo’ orstandard A320 Family aircraft,easing parts’ management for amixed fleet.

Furthermore, the Integrated DriveGenerator (IDG) on the A320neo‘CFM LEAP-X’ is currentlycommon with the IDG on thestandard A320 ‘IAE V2500’. Aninvestigation was carried out on thefeasibility of adding functionalityto the IDG (see figure 5), whichwould have changed the partnumber. The change has since beenrejected, retaining commonality ofthis exceptionally expensive itemof the Initial Provisioning (IP).

Commonality feasibilitystudy results

Figure 4

The A320neo seriesis currently under

development and thedetailed design is yet

to be frozen, thecommonality

percentages willevolve as the design

definition progresses.

ComparisonCommon hardware

(%*)New hardware (%*)

A320 CFM56-5Band A320neo LEAP-X

95.6 4.4

A320 CFM56-5Band A320neo PW1100G

95.6 4.4

A320 IAE V2500and A320neo LEAP-X

95.9 4.1

A320 IAE V2500and A320neo PW1100G

95.5 4.5

*Percentage calculated over the current A320 parts' baseline

b e n e f i t s

The principal benefits of theA320neo aircraft series are:• Reduction in fuel burn of 15%versus the standard A320 Familyaircraft.• Minimum additional spares’investment required due to thesynergy between A320 Familytypes.• Minimal additional maintenancetraining required, owing toretention of existing components.• Inter-operable with current A320Family aircraft.• Benchmark reliability.

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During the A320neo development, Airbushas set objectives for both the RSPL costand the systems’ commonality, and hasaccurately projected the spare parts’ deltabetween the standard A320 Familyand the A320neo series.It is clear that 95% commonality forairframe systems is a tough target, but thesystematic and practical approach madepossible by using spares provisioning datashows how this can be achieved.Innovation in Airbus does not stop withthe introduction of new technologies.

The new engines for the A320neo series,sharklets and a continual aerodynamicoptimisation allow reductions in fuel burn,and therefore significant savings. Theimplementation of this, whilst retainingsystem commonality, is a true demonstrationof engineering excellence which is criticalin today’s competitive ‘single aisle’market. Alongside the aircraft marketleading performance, the success of theA320 Family is also a recognition ofAirbus’ constant strive to improve theproduct with the customer in mind.

Conclusion

This shows that Airbus can makeinformed decisions, based upon theoverall fleet lifecycle costs for thecustomer, and obtain the bestsolution for the aircraft parts'commonality.


IDG example

Figure 5

CONTACT DETAILS

Andrew James MASONProject Manager New Programmes IPAirbus Material, Logisticsand SuppliersTel: +49 (0)40 50 76 24 [email protected]

Graham JACKSONA320neo OperabilityTechnical IntegratorAirbus EngineeringTel: +33 (0)5 61 93 16 [email protected]

BIOMIMICRY - WHEN AIRCRAFT DESIGNERS LEARN FROM NATUREFA

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Denis DARRACQHead of Flight PhysicsResearch & Technology

Airbus Engineering

Asked to design a flying object of about 1kgcapable of a non-stop flight over more than10,000km in less than 10 days, many engineerswould cautiously answer that these requirementscannot be met with current technologies. Someothers might even demonstrate that it is physicallyimpossible to carry the required energy. But bysimply raising eyes towards the sky, researchershave observed that migrating sea-birds, such asthe bar-tailed godwit is achieving this outstandingperformance, and even beyond, when crossing the

central pacific region from Alaska to NewZealand. This small but elegant migratory sea birdis indeed capable of an incredible efficient flight.This is just to illustrate that nature is constitutedof biological solutions and behavioural strategiesthat are extremely efficient, such as energy savingin flight.In this article, you will be convinced that natureinspires aircraft designers, engineers and manu-facturers in many ways.

BiomimicryWhen aircraft designers

learn from nature

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BIOMIMICRY - WHEN AIRCRAFT DESIGNERS LEARN FROM NATURE

Nature: A modelfor humancreationsNatural selection has beenhappening ever since the first signsof life on Earth, more than threebillion years ago. Charles Darwinexplained that this key mechanismof evolution is driving theadaptation of species to theirenvironment. This long process hasyield to remarkable achievementsthat arouse the admiration of thosewho are looking carefully atnature.

In front of a challenge to humanintelligence, such as flying, thesenatural achievements have oftenbeen a direct source of imitationfor pioneers as described by OttoLilienthal in 1911 in “Birdflight asthe basis of aviation”. Sometimeswith dramatic consequences, asexperienced by first attempts ofhuman take-offs.

Then the scientific knowledge hasbeen acquired through a morerational approach of the problem. Ithas enabled a controlled poweredflight yielding a few decades laterto the emergence of the airtransport industry which carriesnow more than two billionpassengers per year across theworld.

Continuous progress of techno-logies combined to the exploitationof more and more powerfulcomputers has permitted to pro-duce more efficient aircraft. As aconsequence, the consumption andemissions of Airbus aircraft havebeen reduced by 70% and noiseproduction by 75% over the last 40years

But the performance obtained withstandard technologies will begin tosaturate soon. Moreover, it will notpermit to deliver the radical step inaircraft efficiency that is requiredin a not so far away future, to meetair transport objectives in terms offuel consumption and emissions.Nature is a source of inspiration foraircraft designers to improveperformance.

Biomimicry should not beconsidered as a full scientificdiscipline, but more as a newapproach in which biologists andengineers are working together,firstly by learning to share acommon language. The basic ideais to understand the mechanisms ofthe living world, to adapt them andto apply them on human pro-ductions, such as on aircraft, forAirbus.

A380 in flight


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We cannot copy precisely nature:An aircraft is not a bird andaeronautical engineers are notexpected to transform themselvesinto butterfly hunters. Commercialaircraft are indeed operating in anextreme environment at transonicspeeds, high pressures, very lowtemperatures and are much largerand heavier than any animal onEarth. For example, at thesespeeds, air compressibility isplaying a major role on aero-dynamic performance. Thereforethe objective is not to simply“mimic” but to understand and toget inspiration from “techno-logical” solutions and strategies ofthe nature.

The adaptation from the livingworld to aircraft production mayrequire several years of researchand development. At Airbus, weare following attentively all thesepotential sources of innovation forour future products.

But where to look?Assuming that apredator must be tougher and fasterthan its prey, it seems thereforesensible to look first at thecreatures on top of the food chain,such as flying raptors and sharks.

But species adapted to extremeconditions or born to a strategy oflong distance migrations have alsodeveloped some clever solutionsthat also should be looked at byengineers.

Denominations of recent andfuture technologies are a revealingindicator of this attraction ofengineers for the models of nature.In aeronautics, we speak of“morphing” shape, “natural” lami-narity, “health” monitoring, “self-healing” and “smart” materials,“memory” shape alloys, “genetic”algorithms, Airbus “sharklets”, etc.The purpose of this article is not tomake an exhaustive list ofinnovations inspired from nature,but more to give a status and aperspective in the field of flightsciences.

Flight control andflight performanceAt the end of the 19th. century, theWright brothers observed thatbirds were manoeuvring and reco-vering from gust destabilisation byslightly twisting the tip of theirwings.

Honeycombed-like structures areused for aircraft panels to gain weight

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They decided to implement asimilar system of wing warping onthe “Flyer” aircraft in 1903, tocomplete what is considered thefirst powered controlled flight.Less than ten years later, as wingswere becoming more rigid, wing-warping was replaced by moveablesurfaces located on the wing. Theuse of ailerons or spoilers forrolling is still the norm today on allmodern aircraft. This is likely thefirst successful application inaeronautics of biomimicry, thoughthe word did not exist at that time.

Globally, an efficient flightrequires producing enough lift(force opposed to gravity) to go upwhile lowering drag (force opposedto speed) to move forward with theminimum energy.

Unfortunately, the production oflift is generating some drag calledthe lift-induced drag or induceddrag. It can be the source of aboutone third of the total drag of anaircraft. Long narrow wings (cha-racterized in aeronautical terms byaspect ratio:Wing chord over span)generate less induced drag for agiven lift. Thanks to a higher wingspan of any living bird, albatrosses(aspect ratio up to 15) are ex-ploiting sea wind energy to glide inany direction effortlessly throughdynamic soaring. Modern com-mercial aircraft have pushed thelimits of aspect ratio up to about 9to 10, as beyond the benefits fromdrag reduction are offset by otherpenalties, such as manoeuvrabilityon ground.

Very large wings are a handicap forbird manoeuvrability (as nicelydescribed by Charles Baudelaire in"The albatross").

Therefore, in order to minimize theinduced drag for a given wingspan, nature has been extremelyinventive. Some large birds, suchas raptors and storks, are deployingimpressive large feathers on wingtips.

These feathers are smoothing themix of airflow near the tip that isresponsible of creating wing tipvortices that generate induceddrag. Similarly, the A380 whosewing span is limited to 80m tomeet airport gate space requi-rements, is equipped with wing tipfences, aiming to improve itsaerodynamic performance. TheA320 Family will also soon benefitfrom innovative wing tip devices -the “sharklets” - that is expected toresult in at least 3.5% reduced fuelburn (first test flight performed inDecember 2011).

To be safe and controlled, a landingmust be completed at low speed.Additional lift and drag is requiredto lower the speed. To achieve lowspeed performance, the aircraftdeploy flaps and increase the angleof attack. Hence aircraft and birdsadopt similar strategies: But maybethe bird solution is the moreadvanced.

More astonishingly, some birds aredeploying alula, a digit coveredwith feathers located on the frontpart of the wing, in order to createa slot on the leading edge. Currentspeculation is that this function isenabling birds to delay stall of thewing (i.e.: To produce more lift). Itis exactly this concept that is usedon commercial aircraft through thedeployment of slats.


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Some sea birds, evolving in areasof strong winds and turbulencehave developed a passive controlcapability of the flow - passivebecause it does not require anyenergy from the bird. Somefeathers located on the wing ofskua birds are deployed by reverseflow, preventing a local separationfrom spreading across the wholewing. Large flow separation isresponsible for stall. This passiveconcept is not applied on aircraftbut wings are equipped with activemoveable surfaces (e.g. spoilers) tocontrol the flow on the wing.

Biomimicry is very promising interms of new perspectives.

MorphingconceptsA common characteristic of life isthe flexibility of shapes that humanindustrial implementation struggleto reproduce. The rigidity of arobot, an aircraft or a submarine, isstriking compared to a man, a birdor a fish. Birds are characterizedby continuously varying the shapeof their wings which guaranteeoptimum performances for variouspurposes: Landing, gliding,flapping, manoeuvring for hunting,diving, etc. In aeronautical terms,these are “multi-functional” wings.

On the contrary, commercialaircraft are based on a fixed-wingstructure that is primarily designedfor optimum cruise performance.The rest of the aircraft mission isachieved through dedicated add-onmoving devices such as spoilers,flaps, slats, rudders and landinggears, that are generally retractedduring almost all the flight dura-tion.Even though the deployment andthe retraction of aircraft flaps andslats can be seen as “primary age”in morphing evolution, we knowthat we cannot go beyond with thecurrent structural technologies, dueto the impact on cost and weight.Nevertheless, novel technologiessuch as “smart” materials areraising the prospect to morphingaircraft concepts. Amongst variousenabling technologies, shapememory alloys sustain largedeformations and recover theirinitial form through temperaturevariations, and piezoelectric mate-rials produce mechanical stresswhen submitted to a voltage.Therefore, suitably designed struc-tures made from these materialscan be accurately controlled tomanage seamless deformation ofthe aircraft weight. This willrevolutionize the aircraft perfor-mance and will make themdefinitively look like birds.

The first test flight with "sharklets"on an A320 took place in December 2011

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Formation flightWe have all observed the im-pressive ‘V’ formation flight ofmigratory birds. Scientific studiesof pelicans in formation haveconcluded that follower birds areflying at a lower heart rate and aremore often gliding than flapping,compared to a solitary flight.Actually, follower birds areexploiting very opportunely the lift(i.e.: The energy) produced by theouter wings of leading birds.Studies confirmed that suchformation flights (actually inverted‘V’ flights) could be applied to airtransport with a significantreduction of emissions on trans-continental routes, even thoughthere would be a time penalty toorganize the flight from variousairports.

SurfacesBeyond all these macroscopicsolutions captured from theobservation of bird flights, weknow that the marine animals andeven the vegetal world, constitute atremendous potential source ofinnovation for future aircraft.Particularly, materials and inter-faces of species with theirenvironment might inspire revolu-tionary capabilities for aircraftengineers. Shark skin is notsmooth at all but on the contrary, isconstituted of micro structures in

the shape of grooves: The dermaldenticles. This was going againstthe belief of aerodynamicists - thesmoother the surface, the lower thedrag. Detailed investigations haveindeed demonstrated that thesegroove structures are reducingsignificantly the skin friction,enhancing speed, and the energeticefficiency of sharks. Flight tests onthe Airbus Beluga aircraft withshark skin-like surfaces called"riblets", have confirmed that suchsurfaces are reducing the fuelconsumption and emissions. About70% of the aircraft surface couldbe covered by these surfaces. Thedrag could be reduced by severalunits of percentage whichrepresents a significant step ofperformance for an aircraft.Nevertheless, there are severalchallenges to address such asproduction, operational reliability(resistance to erosion) andmaintenance.

Lotus plants trigger engineers’curiosity as they present remar-kable properties. They are alwaysclean and dry in a dirty and wetenvironment. Micro structures onthe surface of the leaves preventwater droplets spreading across.Droplets are slipping over the leafclearing the surface from anyparticle of dirt. This self-cleaningproperty is set to equip coatings foraircraft cabin fittings, or couldeven be exploited to prevent iceaccretion on wings.


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This article is dedicated to our sadly missedcolleague, Frédéric PICARD, who was a worldclass connoisseur of orchids. During his time inthe Airbus Innovation Cell, he used to conceivebiomimicry as one of the exciting leversfor innovation.

FrédéricPICARD

Establishing historically the sources ofprogress of human flights is not an easytask. And if aircraft look like birds, it issometimes impossible to distinguishwhether a technology is really due to theobservation of birds or to pure humanabstraction. Actually, it does not reallymatter: The lesson is that humandeterministic methodology and naturalselection often converge to the samesolutions.But the bird flight is only the emerged partof the iceberg that has been captured sofar. The rest of the living world, includingplants, is a huge tank of potentialinnovations for aeronautical engineers,particularly to control and exploit theturbulence of flows,

to design innovative materials andadvanced interfaces. The furtherexploration of nature in the perspective ofdrastically reducing air transport fuel burnis requiring a more direct collaborationbetween aeronautical engineers andexperts of all disciplines of biology.The extinction of any species caused byhuman activities - that is a tragedy in itself- represents a definitive loss of knowledgeand therefore a potential loss of source ofprogress for humanity and for theprotection of the environment. This is thereason why the preservation ofbiodiversity is a priority for industries thatwill face tremendous technologicalchallenges in the future, such as Airbus.

CONTACT DETAILS

Denis DARRACQHead of Flight PhysicsResearch & TechnologyAirbus EngineeringTel: +33 (0)5 62 11 75 [email protected]

Conclusion

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RADIO ALTIMETER SYSTEMS - CORRECT MAINTENANCE PRACTICES

Incorrect maintenance of key aircraft systems canharm the continued safe operation of the aircraft.One key system, used during critical flight phasesincluding landing, is the Radio Altimeter system.Several events have been reported where failuresof this system have contributed to damage theaircraft during landing operations. What is littleknown, is that in many cases these events couldhave been prevented. The root cause investigation

often identified that the reason for the malfunctionof the system was due to a degradation that couldhave been prevented by simple maintenancepractices, such as the cleaning correctly beingcarried out. This article aims to explain why theapplication of best practice maintenance proce-dures on the Radio Altimeter system is key, anddetails the best practices to support the continuedsafe operation of Airbus aircraft.

Radio Altimeter systemsCorrect maintenance practices

Ian GOODWINProduct SafetyEnhancement ManagerAirbus S.A.S.

Sandra PREVOTRadio Nav/Com & Data-Link Systems

Customer Support Engineering

RADIO ALTIMETER SYSTEMS - CORRECT MAINTENANCE PRACTICESFA

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How does a RadioAltimeter function?

The barometric altitude, usedduring cruise phases to determinean aircraft’s altitude, is by its natureimprecise due to the variation ofthe atmospheric pressure. Whilstthis is not a problem in cruise,during the approach phases, it ishowever necessary to have agreater precision which is notpossible using the barometricaltitude. A Radio Altimeter istherefore used to provide anaccurate height above ground levelwhen the aircraft is between 0 and2,500ft.The Radio Altimeter functions bymeans of radio waves. It transmitstowards the ground a radio wave,and measures the time taken toreceive the reflected wave inreturn. The time between theemission and reception allows thecalculation of the height of theaircraft above ground level. TheRadio Altimeter system consists oftwo (three on the A380) inde-pendent systems, each systemconsisting of a transceiver, atransmission antenna and areception antenna.

Antenna R1

Antenna T1

Antenna R2

Antenna T2

CaptPFD

GPWS

FWC 1

TCAS

RadioAlt 1

ELAC 1

FMGC 1XMSN

antenna

Receiptantenna

FOPFD

FWC 2

RadioAlt 2

ELAC 2

FMGC 2Receiptantenna

XMSNantenna

Interaction of the Radio Altimeter with aircraft systems (A320 used as example)

Figure 1

Capt: Captain - ELAC: Elevator Aileron Computer - FO: First Officer - FMGC: Flight Management and Guidance Computer - FWC: Flight Warning ComputerGPWS: Ground Proximity Warning System - PFD: Primary Flight Display - TCAS: Traffic Alert and Collision Avoidance System - XMSN: Transmission

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Exampleson aircraft

Symptoms Observations Corrective action

A319

Heavy landing inAUTOLAND and a

continuous RETARDcall out.

Radio Altimeterfeedback frozen at

-4ft. Moisture ingressobserved in the RA

installation.

Correct re-installationof the RA, including

installation ofwaterproofing.

A320Tail strike with multiple

spurious ECAMwarnings.

Both RA signalsobserved going NCD.

Similar effectspreviously observed onsame aircraft but hadcleared at gate, so no

trouble-shootingperformed.

RA connectors notinstalled as per AMM(Aircraft MaintenanceManual), with lack ofwaterproofing and

incorrect crimping onone antenna,

suspected following anincorrect SB

application. Antennasre-installed correctly.

A321 Untimely RETARD callout.

RETARD calltransmitted

at <22ft. RA antennaidentified dirty.

Dirt impacted thetransmission and

receipt of the signal.Corrected by cleaning

the RA antennasurface.

Consequences of Radio Altimeter failures

Table 1

i n f o r m a t i o n

Flare modeThis mode is automatically engagedwhen the Radio Altimeter indicates100ft. above ground.At 50ft. the aircraft trims the noseslightly down. During the flare,Normal Law provides a high angleof attack protection and bank angleprotection.The load factor is permitted to befrom 2.5G to -1G, or 2G to 0G whenthe slats are extended.The pitch attitude is limited from+30 to -15° which is reduced to25° as the aircraft slows down.

The radio height data is shown onthe Primary Flight Display (PFD)and also provides feedback to anumber of aircraft systems, toadvise these on the height of theaircraft. In figure 1, you will findthe typical interaction of the RadioAltimeter system with aircraftsystems.

What can gowrong?

Consequences of Radio Altimeterfailures have been welldocumented, but before reviewingsome case studies, let’s reviewwhat feedback the Radio Altimeter(RA) provides. There are twocommon operating modes of theRA system:• The first is coded NormalOperation (NO): In this case, theRadio Altimeter correctlytransmits and receives the radiowaves, and therefore provides anindication of the aircraft’s heightabove the ground.• The second is Non ComputedData (NCD): Above a certainaltitude (more than 5, 000ft orduring specific flight phases(i.e.: Roll > 30°)), the signallevel received by the receptionantenna does not allow theaircraft height to be computed.The height is therefore no longertransmitted and the RA outputbecomes NCD.

If an incorrect value is received,this can have a negative effect onthe aircraft system:• Too low value (erroneous), canlead to an early activation offlare which could lead to anincrease in the aircraft angle ofattack, which if not corrected,could lead to aircraft stall, hardlanding or other operationaleffect.• An incorrectly transmitted NCDvalue will lead the aircraft tobelieve that it is in cruisealtitude. If this occurs when theaircraft is on the ground or inapproach, this could lead to

the non-activation of the flarelaw*, leading to a tail strike ormultiple ECAM (ElectronicCentralized Aircraft Monitoring)messages on ground.

Does this occur inoperation?Damage to the Radio Altimetersystem can occur from either wearand tear coming from normal dailyoperation of the aircraft, or follo-wing an incorrect or incompleteapplication of maintenance prac-tices, all of which can lead toerroneous values. In such cases,these can lead to spurious cockpitindications or incidents which canresult in the aircraft being out ofservice for a lengthy period. Threetypical cases, with different causesare described in table 1.


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i n f o r m a t i o n

Radio Altimetercleaning requirements• SIL 34-099 scheduledmaintenance taskrecommendation for RadioAltimeter antennas’ externalsurface cleaning• 344200-0503-2for the A300 MPD*• 34-42-02for the A300-600ST OMP*• 344200-02-1 for the A300-600and A310 MPD• 344200-03-1 for theA318/A319/A320/A321 MPD• 344200-04-1 for the A330and A340 MPD• 344000-00000-01for the A380 MPD

* MPD: MaintenanceProgramme Development

* OMP: OperatorMaintenance Programme

Maintenanceaspects

The operational consequences andwhat is observed when there is anerroneous Radio Altimeter readinghas been covered in detail inAirbus’ Safety First edition #11.However, as an essential andimportant piece of equipment, it isnecessary to ensure that the main-tenance actions and procedures arecorrectly applied.

ACT NOW TO PREVENT LATERDELAYS

In the examples in table 1, whilstthe root cause is different, a keymessage to extract is that thetrouble-shooting and root causeidentification only commencedafter there was a significantoperational interruption. There-fore, in the event that a RadioAltimeter failure is suspected, thentrouble-shooting in accordancewith the Trouble-Shooting Manual(TSM) should be performed.

New TSM procedures have beenwritten to provide recommenda-tions to cover:• Erroneous Radio Altimeterheight indications,• Radio Altitude set to NotComputed Data (NCD).

Prevention isbetter than curewith a correctmaintenanceapplication

Root cause analysis in the threecase studies in table 1 show that theapplication of incorrect main-tenance or installation procedurescould drive to the RA mis-behaviour so, prevention beingbetter than cure, the followingpoints detail the actions to take.

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Figure 3

A: Before MOD - B: With additional slack - C: Broken connectors

Figure 2

Accumulation of dirt aroundRadio Altimeters

A B C

CLEAN TO PREVENT ERRONEOUSDATA

The first case is to ensure that theperiod of your maintenance taskassociated to the cleaning of theRadio Altimeter antennas iscorrectly suited to the aircraftoperation. The RA antennas,located on the bottom of theaircraft behind the main landinggear (centre landing gear on theA340), are in the ideal position toget covered by dirt whichaccumulates in normal operation.In addition, they suffer from beingstained by liquids discharged viathe onboard galley drain. Thesematerials can form a thick residueon the surface of the antenna andprevent them from functioningcorrectly.

To address this issue and as dirtaccumulation on the RA is acommon failure mode, the firstaction of the trouble-shooting forRA erroneous data is to clean itsantenna. To prevent the aircraftfrom getting into a position whereincorrect RA data is beingtransmitted due to dirt, a periodiccleaning is scheduled in the MPD(Maintenance Planning Document)with an interval of 6 months. In theevent that dirt accumulation isobserved to occur at a greater ratethan that covered by the MPD task(for example if operating on slushyor contaminated runways, particu-larly in winter periods, etc.) thenclean the RA antennas at a reducedinterval. The advantages of this isto prevent the RA data becomingNCD or erroneous at landing, andreducing the chances of a tail strikeor hard landing.

MORE FORCE IS NOT NECESSARILYTHE ANSWER

On the A320 Family aircraft, whenreplacing the Radio Altimeterantenna, it is often observed thatthere may not be quite enoughavailable cable length to com-fortably disconnect/connect theantenna to the cable.

This tempts the mechanic to pulljust that little bit harder, sometimeson the antenna, to give that little bitmore slack. This extra force on theantenna harness weakens theconnectors, and whilst it may lookundamaged from the outside,several flight cycles after theantenna replacement the connec-tors may break (see figure 3). Thiscan cause the disturbances of theRA signal which may transmiterroneous indications or switch toNCD, and lead to issues onapproach and landing increasingthe risk of an incident.To counteract this difficult accessto free the RA cable on the A320Family aircraft, Airbus hascertified a modification which re-routes the coaxial cable to provideadditional free cable to ease thereplacements of RA antennas. Thiscan also be embodied on aircraftvia a Service Bulletin.

Gel gasket

Additional sealant

Shrink sleeve

Shrink sleeve

Lock nut

Optional shrinksleeve (depending

on model)


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WATER ALWAYS FINDS ITS WAY TOTHE WRONG PLACES

One of the main causes forincorrect RA readings comes fromwater ingress and the con-tamination of the connectors.Water ingress can cause forexample an erroneous -6ft value bydirect coupling between thetransmitting and receiving antenna.Also, NCD values may occur dueto water causing corrosion of thecables or the antennas themselves.So what can be done about this?Water ingress can be tackled in twomeans:• By ensuring that the correctinstallation procedures arefollowed,and• By applying the latestinstallation recommendationsand appropriate waterproofmaterials.

The latest installations have beendesigned to identify and removeweak points in the water proofingof the harnesses.

The evolution has taken variouscourses of action:• Installation of additional shrinksleeves on the connector betweenthe RA antennas and cables theintroduction of which are coveredby the issuance of appropriatemodifications (see figure 4).• The AMM (AircraftMaintenance Manual)installation tasks have beenupdated, ensuring that theinstallation is correctlywaterproofed.

To enhance the waterproofcharacteristics of the shrink sleeveinstallation, additional sealant atthe top and bottom of theinstallation is added. This ensuresthat no water is able to ingress intothe assembly; either from the top orbottom of the installation (refer toassociated AMM procedures andSIL 34-087). When introducing thesealant, a key aspect is to makesure that the sealant has time todry. Not drying the sealant mayimpact the waterproof abilities ofthe installation. The appropriateAMM tasks now reference this as astandard installation.

Addition of shrink tubes to improvewaterproofing of the RA installation

Figure 4

Enhancement of water proofingby the addition of sealant

Figure 5

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The figures 4 and 5 show thebuilding up of the waterproofinstallation on the Radio Altimeterantenna. It is important to note thatto get the full protection, all partsneed to be correctly installed. Ifone of the parts is not correctlyinstalled, then there is likely to bewater ingress into the system withits consequential effects.

Further modifications have beenintroduced to prevent water ingressinto the antenna cable and consistof:• Adding sealant on the pipe.• Replacement of the currentpolyamide protection pipe with alonger metal one which is lessdisposed to deformation andcracking caused byenvironmental conditions.• Additional water proofingapplied to the end of theprotective boots, by puttingadditional tape and clamps atboth ends to make sure that theentrances of the protective bootsare sealed against eventualexternal water ingress (refer tofigure 6).

• Introduction of a new gel gasketbetween the Radio Altimeterantenna and the aircraft structureto improve waterproofness of theinstallation (detailed in figures5 and 7).

Steps for additional sealant between the RadioAltimeter antenna and the aircraft structure

Figure 7

Protective boots

Figure 6

Sealant PR1436GB

Antenna 'O' ring

Varnish

Protection pipe

Rivet4

2

1 3

Apply sealant betweenpipe and skin

1

Apply sealant aroundouter flange

2

Apply sealant ininner gap of pipe/skin

3

Apply sealant over the headof the rivets

4


To ensure that the Radio Altimeter systemcontinues to provide accurate and correctinformation, it is necessary to recognize,report and trouble-shoot symptoms of theRadio Altimeter misbehaviours as soon asthey appear.The operators must adapt theirmaintenance regime to the environmentalconditions and make sure that during the

installation of the Radio Altimeter, theinstructions are fully followed (includingrespecting sealant cure times).By following the points identified in thisarticle and developed in the referencedAirbus documentation, the integrity of theRadio Altimeter system can be ensuredand the continued safe operation of theaircraft supported.

Conclusion

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CONTACT DETAILS

Sandra PREVOTRadio Nav/Com & Data-LinkSystemsCustomer Support EngineeringTel: +33 (0)5 61 18 83 [email protected]

Ian GOODWINProduct Safety EnhancementManagerAirbus S.A.S.Tel: +33 (0)5 61 93 33 [email protected]

The replacementof cables - gettingold gracefullyLike all equipment, after a life timeof wear, tear and exposure to theenvironment, the Radio Altimeterantenna cables may become dama-ged, the water proofing maybecome less efficient and corrosioncan set in. Water ingress that hasoccurred may have affected theshielding or the wiring, causingcorrosion and thus perturb thesignals. Water present in the RAcables may cause cross couplingand erroneous values occurring.

The continued operation of theaircraft with old cables installed isnot recommended. Therefore, as aprecaution, Airbus has addressedthis issue by including in the MPDa regular task to replace the cablesand antennas. This is scheduled totake place every 144 months (12years), during the heavy inspectionfor structural items (refer to SIL34-097 for additional information).In addition, it ensures that theRadio Altimeter cables andantennas are installed to the mostrecent specification, with the lateststandard of waterproofness, ensu-ring continued efficiency andaccuracy of the Radio Altimetersystem.

Radio Altimeters locatedon the belly of the aircraft

d o c u m e n t a t i o n

Installation improvementsfor the Radio Altimeter:• SIL 34-087 Radio Altimeter antennas,protection against watercontamination• SIL 34-097 Aircraft ScheduledMaintenance Task Recommendationrelative to Radio Altimeter antennas’installation

• For the A320:AMM 34-42-11-400-001• For A330/A340:AMM 34-42-11-400-801

Service Bulletins:• SBs for improvement of electricalinstallation for antennas (Issue 2 orsubsequent):- A320-92-1030- A330-92-3044- A340-92-4054- A340-92-5005• SBs for installation of gel gaskets:- A320-34-1476- A330-34-3218- A340-34-4222- A340-34-5064

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ELISE CONSULTING SERVICES - ILS ADVANCED SIMULATION TECHNOLOGY

The Instrument Landing System (ILS) is aground-based system at airports. It providesreliable guidance to aircraft approaching andlanding at the airport, and is especially useful inreduced visibility conditions. The signal emittedby the ILS system can be sensitive to multipathdisturbances caused by objects close to therunway, including other aircraft, buildings andcranes. Accurately predicting disturbances such as

these, ELISE (Exact Landing InterferenceSimulation Environment) enhances the safety oflanding operations, can allow to increase runwaycapacity and allows the optimisation of airsideland usage. This article describes the specialisedconsulting service which uses this advancedsimulation software which predicts disturbanceswith an unequalled level of accuracy andreliability.

ELISE Consulting ServicesILS advanced simulationtechnology

Bruno GUTIERRESHead of Airbus BusinessNurseryAirbus S.A.S.

Jean-Paul GENOTTINHead of Airside Operations

Airport OperationsAirbus S.A.S.

Laurent EVAINAirport Regulatory Manager

Airport OperationsAirbus S.A.S.

Signal received =direct + multipath

LOC antenna

Directsignal

Multipath

Approach slope

3°GP

LOC

ELISE CONSULTING SERVICES - ILS ADVANCED SIMULATION TECHNOLOGYFA

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Approach slope: Intersection of Localizer (LOC)and Glide Path (GP) signals

Figure 2

What is an ILS?

An Instrument Landing System(ILS) is a ground-based instrumentapproach system (see figure 1) thatprovides precision guidance to anaircraft approaching and landingon a runway. It uses a combinationof radio signals to guide theaircraft during reduced visibilitylandings (Instrument Meteo-rological Conditions – IMC) suchas for low cloud ceilings, fog, rainor snowy conditions. The ILS iscomposed of the Localizer (LOC)antenna which provides runwaycentre line guidance to aircraft, andthe Glide Path (GP) antenna asshown in figure 2, which providesthe standard 3° slope guidance.

ILS multipathinterferenceAny large reflecting objects at anairport can potentially cause multi-path interference to the ILS signal.These disturbances can make theILS signal deviate from its nominalposition, which would cause adeviation of the aircraft inapproach to the extent that itbecomes unacceptable.Aircraft, cranes and large buildingscan produce an ILS multipathinterference that would exceed therequired tolerances as set inICAO’s (International Civil Avia-tion Organisation) Annex 10document.

Figure 3

Multipath disturbances of ILS signal caused by surrounding obstacles

Figure 1

Localizer and Glide Path antennas

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n o t e s

EADS: European AeronauticalDefense and Space companyENAC: Ecole Nationalede l’Aviation Civil

Figure 4

Methods of object modeling

Classic method in 2D

ELISE method in 3D

However, ILS predicting softwarecan be used to calculate theprobable location, magnitude andduration of ILS disturbancescaused by objects. A number ofILS disturbance prediction toolscurrently exist. These tools rely onthe theory of physical opticsapplied to 2D flat rectangularplates. They have the advantage ofproviding very rapid simulationtimes but their validity for treatingobstacles at grazing incidence isquestionable. Generally, the moreaccurate the ILS predicting tool,the more computation power,memory and time is required. Thisis particularly true for the latestgeneration of tools like ELISEwhich models objects in 3D.

The ELISE solutionAirbus in collaboration withEADS* Innovation Works (EADSIW) and the ENAC* has developed

a consulting service usingadvanced simulation software forILS disturbances called ELISE(Exact Landing InterferenceSimulation Environment). ENACis a renouned French civil aviationuniversity and centre of excellencein ILS antenna expertise. EADSIW operates the EADS corporateResearch and Technology (R&T)laboratories and a global networkof technical centres, includingelectromagnetism.

How does ELISEwork?ELISE uses advanced technologiesin:• Object modelling: ELISE iscapable to model the objects in 3dimensions, whereas theprevious generation of classicILS predicting tools uses 2D flatplates (see figures 3 & 4).


• Core computing: ELISE usesan exact method of resolution(Method of Moments) for theradio signal propagationequations (Maxwell’sequations), whereas previousclassical methods are basedonly on approximations(physical optics) of theMaxwell’s equations. The‘Method of Moments’ is themost advanced and accuratemethod to model the behaviourof ILS signals.

Based on those two advancedtechnologies, ELISE consultingservices offer a step change inaccuracy and reliability on ILSsignal predictions compared to theexisting classic ILS predictingtools.

The advanced levels of accuracyand reliability of the ELISEsoftware have been validated bymore than a hundred ground andflight measurements performed atseveral airports (see figure 6), incoordination with the reference ofEuropean Air Navigation ServiceProviders - ANSP (DTI in France,DFS in Germany, NATS in the UKand SkyGuide in Switzerland).

These measurement campaignshave demonstrated that ELISEsimulations deliver a better corre-lation with these measurements,which translate into direct ope-rational and tangible benefits toELISE users.

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Methods of resolution of ILSpropagation equations

Figure 5

Better correlation between results from the actual measurements and ELISE

Figure 6

MeasurementELISE

Error between ELISE results and actualmeasurement

Simplified classic method

Exact ELISE method

Measurementclassic method

Error between results from classic methodand actual measurement

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ELISE benefitsELISE delivers direct operationaland financial benefits to the targetcustomers (i.e.: Air NavigationService Providers, airport opera-tors and consultants) described inthe three following points.

1. TO IMPROVE SAFETY BYREDUCING THE RISK OFUNPREDICTABLE ILS FLUCTUATION

When an aircraft takes-off it cangenerate fluctuations in theLocalizer signal used by anyaircraft on approach. Thesefluctuations can cause lateraldeviations to the aircraft onapproach or during landing to thepoint where the landing aircraftcould veer off the runway surface.By modelling the aircraft in 2Donly, classic tools cannot predictthose fluctuations, which is aconcern for safety. ELISEmodelling in 3D is accurate andcan predict all situations deliveringreliable simulations.

2. TO INCREASE GROUND CAPACITYBY REDUCING SIGNIFICANTLY THE ILSPROTECTION AREAS

The Localizer signal needs to beprotected from multipath inter-ference. One of the protectionareas is near any parallel taxiwaysto the runway. On the taxiway, theaircraft is at a grazing angle to theLocalizer signal. At grazing angles,classical prediction tools providefar more conservative results thanELISE.

Simulation with classic methodLimits of ICAO CAT 1Simulation with ELISE showing out of tolerance disturbance

Figure 7

Safety issue when results from classic methods under-estimate the real impactof obstacles

ELISE CONSULTING SERVICES - ILS ADVANCED SIMULATION TECHNOLOGYFA

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Unhelpfully and as shown in figure8, classic tools can even predictout-of-tolerance disturbances (inred), which in reality, are wellwithin the tolerance defined by theICAO Annex 10 specifications (ingreen). By using classic tools, theANSP could impose unnecessaryoperational constraints to theairport, even to the point of notallowing the use of a paralleltaxiway which would adverselyimpact the runway’s capacity.ELISE can significantly help anANSP take decisions that optimizeaircraft operations with sound andreliable predictions.

3. TO ALLOW THE CONSTRUCTION OFBUILDINGS CLOSER TO THE RUNWAY

The ICAO European guidelines formanaging Building RestrictedAreas (BRA) define a volumewhere buildings have the potentialto cause unacceptable interferenceto the ILS signal. Within the BRA,it is necessary to demonstrate(using simulation or other means)that any proposed building forexample will not cause distur-bances in excess of the predefinedlimits.

ELISE advanced technologies havepermitted the development ofelegant “stealth” solutions forbuilding facades to prevent thebuilding from causing the loss ofCategory III operations at airportrunways. The solution is based ondiffraction gratings that redirectthe incident wave back to its sourcerather than the specular direction.Diffraction grating has been ex-tensively studied in the 1980s buthas never been applied onbuildings for the ILS problem. Theshape of the diffraction grating isoptimized for the specific positionand orientation of the buildingtoward the runway.By using this stealth technology onbuildings located within previouslyforbidden areas, land-constrainedairports are now in a position to sig-nificantly increase their landincome (up to 100 hectares can besaved).

Way forward

The ELISE software is beingintroduced in the ICAO WorkingGroup in the Navigation Systems’Panel (NSP) in charge of updatingthe ILS Protections Areas in ICAOAnnex 10.

Sca

t.si

dew

ayp

ositi

on(m

)S

cat.

sid

eway

pos

ition

(m)

Scat. forward position (m) % of ICAO limits

Scat. forward position (m)

0 50 100%

Taxiway parallel to the runway

Taxiway parallel to the runway

ILS protection areas around runwayoptimized with ELISE

Figure 8

With classicmethods

With ELISE

29

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Airbus is much more than the leadingaircraft manufacturer. It delivers a largerange of services not only to airlines, butalso to Air Navigation Service Providersand airports. ELISE is one such service,with advanced simulation software thatpredicts ILS disturbances with a level ofaccuracy and reliability unequalled today.

The ELISE team can provide detailedanalysis and expertise to airports whichwant to maximize their ground capacity,build new buildings closer to the runwaysor operate new aircraft. If you would likemore details, please contact our specialists.

Conclusion


CONTACT DETAILS

Laurent EVAINAirport Regulatory ManagerAirport OperationsAirbus S.A.S.Tel: +33 (0)5 61 93 11 [email protected]

Jean-Paul GENOTTINHead of Airside OperationsAirport OperationsAirbus S.A.S.Tel: +33 (0)5 62 11 80 [email protected]

Bruno GUTIERRESHead of Airbus Business NurseryAirbus S.A.S.Tel: +33 (0)5 62 11 06 [email protected]

After almost one year of businesstests, Airbus’ ELISE ConsultingServices receives very strongpositive feedback from severalairports and Air NavigationService Providers. Since lastquarter 2011, several studies havebeen already done for customers.Year 2012 is expected to see aconfirmation of the interests of thehuge capabilities of the ELISEsoftware.

EADS Innovation Works (IW)gathers the EADS corporate Researchand Technology (R&T) laboratories thatguarantee the group’s technicalinnovation potential with a focus onthe long-term horizon. EADS IW has themission to identify new value-creatingtechnologies and to developtechnological skills and resources.Gilles PERES (electromagneticspecialist) and Andrew THAIN (designerof stealth buildings) are part of theelectromagnetic team that developeda complete range of software itemsincluding ASERIS which is at the heartof ELISE. These software support thestudies of electromagneticcompatibility, antenna sittings, stealth,and more generally, the effects ofthe electromagnetic aggressions onthose systems.

The Ecole Nationale del'Aviation Civile (ENAC)is a French civil aviation university.Since 1 January 2011, it has becomethe biggest aeronautical universityin Europe. The trainings provided atthe ENAC involve each year an averageof 2,000 students composed ofengineers, air traffic controllers,electronic engineers, technicians, airtransport pilots and flight dispatchers.Bertrand SPITZ (ILS instructor) is partof the electronic department thatdeveloped a worldwide expertise in ILSantenna knowledge. He has developedthe ILS antenna modelling and thehuman interface display of the ELISEsoftware.

EADS IW and ENAC:Two core partners for ELISE

Supported by

THE ‘CLEAN SKY’ INIATIVE - SETTING THE TONEFA

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The ‘Clean Sky’initiative

Setting the toneClean Sky brings together leading aviationcompanies and experts to form a truly Europeantechnology platform. Its key objective? To maturethe most advanced green technologies in thefields of large commercial transport aircraft,regional aircraft, rotorcraft, aircraft engines andaircraft systems.For Airbus, Clean Sky is one of the mostimportant elements of aeronautical research inEurope; not only due to its budget of 1.6 billioneuros, but also due to the fact that for the firsttime in history, the Clean Sky initiative hascreated a 7-year partnership on a European level,

to enable the validation of large-scale systems inreal flight demonstrations.Embedded in the 7th European FrameworkProgramme, the Joint Technology Initiative (JTI)that is Clean Sky offers a key opportunity toaccommodate Airbus Research and Technologypriorities, with the view to preparing the nextgeneration of ever more efficient aircraft.The following article has been published in theAir and Space Academy Newsletter (#72) anddemonstrates Clean Sky’s active involvement inpaving the way for an eco-efficient future.

Eric DAUTRIATExecutive DirectorClean Sky J.U.

Axel KREINSenior Vice-President

of Research and TechnologyAirbus S.A.S.

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THE ‘CLEAN SKY’ INITIATIVE - SETTING THE TONE

An example of Airbus’ role inClean Sky is the coordination(jointly done with Saab Aero-systems) of the Smart Fixed Wingaircraft platform, which is one ofthe six mentioned integratedtechnology demonstrators in CleanSky. Here Airbus is pursuing majoractivities to mature an all new lowdrag “Smart Wing“ concept andthe integration of the mostpromising innovative engine con-cept - the Contra Rotating OpenRotor (CROR) - to achieve asubstantial improvement in fuelburn and noise reduction for thenext generation large transportaircraft.Airbus is also contributing to otherintegrated technology demons-trators, like systems for greenoperations, eco-design or theTechnology Evaluator.

Clean Sky’s articlepublished in theAir and SpaceAcademyNewsletter

“Clean Sky”, a designation thatclearly sets the tone. Whethergreen or blue, we know straight offthat it will be a question of sky andenvironment. Let's be clear. Thequestion here is not one of wagingwar on the (scant) smoke stillescaping from our factorychimneys, nor even coping withthe volcanic ash which grabbed theheadlines in 2010. We are talkingof aeronautical technologies desig-ned to reduce the environmentalfootprint of future aircraft in termsof CO2, noise, NOx and life cycleeffects.

Born out of the ACARE (AdvisoryCouncil for Aeronautics Researchin Europe) Strategic ResearchAgenda, Clean Sky is a somewhatunusual initiative.

A “Joint Technological Initiative”,it hinges on a public-privatepartnership associating the Euro-pean Commission and just aboutthe entire civil aircraft industry ofEurope. In the course of a ten yearperiod (2008-2017), it aims todeliver integrated demonstratorswith a high TRL (TechnologyReadiness Level).

The total cost of the programme is1.6 billion euros, making it one oftwo or three of the largest researchprogrammes ever financed by theEuropean Union in any field.

In addition to direct benefits toEuropean citizens, the reduction ofCO2 emissions and noise alsoprovides a federating objective on atechnological level. Efforts will bemade in the areas of aerodynamics,mass, propulsion efficiency, flightpath optimisation, etc.

The programme is organized intosix Integrated Technology De-monstrators (ITD), technologicalplatforms grouping together cohe-rent research areas and theinterested players (see figure 1).

ITD: Integrated Technology Demonstrator

Governing board:12 industrial leaders + 6 associates

+ EU commissionScientific

and technicaladvisory board

Europeanparliament.

Annual discharge

National statesrepresentatives

group

Partners ITD ITD ITD PartnersITD ITD ITD

General forumJoint Undertakingexecutive team

TechnologyEvaluator

Clean Sky is steered by public and private stakeholders

Figure 1

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Each one is directed by a tandem ofindustrialists. Three of them con-cern aircraft directly:• Smart Fixed-Winged aircraft, forcommercial aircraft (Airbus andSaab)• Green Regional Aircraft (Aleniaand EADS’ Spanish arm)• Green Rotorcraft (Eurocopterand AgustaWestland)with three further transversetopics:• Sustainable and Green Engines(Rolls-Royce and Safran)• Systems for Green Operations(mission and flight pathmanagement, energymanagement with Thales andLiebherr)• Eco-Design (Dassault andFraunhofer).

The whole is topped by a‘Technology Evaluator’, a set ofmodels intended to identify envi-ronmental benefits on a level of anindividual mission, an airport orthe entire world fleet. This Eva-luator is directed by Thales and theDLR.

Around this circle of ITD leaders isa wider circle of associates: Over70 other industrialists, researchcentres, SMEs (Small & MediumEnterprise) and universities, com-mitted like the leaders for the wholeduration of the programme. Theseinclude organisations as diverse asZodiac, MTU, Onera, Ruag, theUniversities of Milan and Cranfieldor the Romanian INCAS.

Leaders, associates and theEuropean Commission constitutethe members of the Clean SkyJoint Undertaking, or J.U., apeculiar legal creature whoseunique mission is to implement theTechnological Initiative of thesame name. They are representedby a governing board, which acts asboth the management committee ofthe programme and the board ofdirectors of the J.U. The essence ofthe public-private partnership liesin the joint taking of strategicdecisions. Of course, shareddecision making also impliesshared funding. Funds are providedhalf by the Commission - from theFP7 (Framework Programme forresearch - Euro funding and indus-try co-funding) budget - and halfby industry. (NB: The term “indus-try” is a simplification. It includesresearch centres and other publicorganisations sharing the samefinancing terms).

A third circle exists, of crucialtechnological and politicalimportance: The “Partners”. Theseare selected by means of regular(more or less quarterly) calls forproposals. They must meet precisetechnical specifications stemmingfrom the requirements of the de-monstrators. Today, after sevencalls for proposals and the relatedevaluation processes which arecarried out according to EuropeanCommission rules, it would appearthat the SMEs are doing well,representing about 40% of a total ofalmost 300 identified partners (andrising): Clean Sky is graduallyinvolving not only the majoraeronautics players, but also asignificant number of newcomers.

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As regards governance, the highestauthority is wielded by thegoverning board while the mana-gement of the programme isentrusted to the executive directorof this Joint Undertaking and histwenty-member team. The J.U.issues contracts to members andpartners and ensures proper exe-cution of activities; the Director isdirectly responsible to the Euro-pean Parliament.

It would be tedious to cite thehundred or so key technologies and30 demonstrator projects includedin the six ITDs. A few exampleswill suffice in order to make somegeneral observations:• Open Rotor (see figure 2) is themost weighty, to the extent thatClean Sky finances two parallelprojects: One by Rolls-Royce,the other by Snecma, both withgeared counter-rotating pusherpropulsors. In terms of CO2benefit, Open Rotor is verypromising with approximately30% reduction in engine specificfuel consumption, a little lessonce installed because of weightpenalties for example. Problemsof noise, vibration andcertification have to be resolvedof course, but the latestinformation is encouraging. Oneof these demonstrators will bebench tested in 2015, andsubsequently flight tested on anAirbus A340-600. This conceptis in fact not entirely new, havingalready been tested in the UnitedStates during the 1980s’ surge infuel prices, more short-lived thantoday. It does though benefitfrom developments carried outin the past quarter of a century.

FIRST OBSERVATION

Clean Sky includes neither flyingwings, rhomboidal wings, solarplanes nor hydrogen propulsion,but rather aims for the shorterterm, the very next generation ofaircraft:

• Laminarity is another large-scaleproject, and a flightdemonstration is also planned in2015 on an A340, with therealisation and installation of an8 metre-long wing element. Forthe moment it is a question ofnatural laminarity, which makesmanufacturing aspects all themore essential, as well as theverification of the robustness ofthis laminarity, which must notbe lost with the first mosquitostrike! Like Open Rotor,laminarity is a very promisingtechnology that will be relevantfor future aircraft generationsthat could enter the marketaround the horizon 2025. CleanSky provides the platform andtimeframe, making the largerequired technological steps atthe right time.

Figure 2

Contra-rotating Open Rotor

NACRE: New AircraftConcepts Research

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SECOND OBSERVATION

Clean Sky, by definition, is relatedto industrial strategies. It aims toprepare, from the viewpoint ofenvironmental technologies, futuregenerations of planes and rotor-craft. This provides an essentialguarantee - disregarding unfore-seen factors which are alwayspossible in research - that publicexpenditure will not be fritteredaway on superb but unapplicabletechnologies. It is also the objec-tive of shared governance:• Flight path optimisation isanother effective means toreduce both CO2 emissions andnoise. In addition to the SESAR(Single European Sky ATMResearch) programme, anotherJ.U. comprising the technicalside of the European Single Skyinitiative, which will optimize airtraffic and achieve environmentalbenefits by avoiding fuel waste,Clean Sky is also looking into

cockpit technologies which willenable real time optimisation ofan individual mission.

THIRD OBSERVATION

SESAR is interested in traffic,Clean Sky with the vehicle. Sincethe one cannot advance without theother, the two programmes arepartially linked:• Research concerning compositematerials (and therefore weight)is carried out within theframework of regional aircraft.Some examples include carbonnanotubes in order to improveconductivity and shear strength,and multi-layer, multifunctionmaterials. Admittedly, Clean Skyis far from being the only partyinvolved in research activities oncomposites! For commercialaircraft, it is carried out in othercontexts.

FOURTH OBSERVATION

Clean Sky is not an island, on thecontrary, it has many partners,many connections with the classicFP7 or national programmes;better still, Clean Sky aims to havesome leverage on the latter. Let usnote that in France, for example,the CORAC (COnseil pour laRecherche Aéronautique Civile)takes this necessary complemen-tarity very seriously:• Business aircraft, regional aircraftand helicopters coordinate part oftheir “all electric” activities since“all electric” or “almost all”, iseasier to achieve in these sectors(for reasons, in particular, ofdissipated power) than forcommercial aircraft, although thelatter are not entirely absent.Corresponding architectures willall be tested on a “Copper Bird”belonging to the “eco-design”ITD.

FIFTH OBSERVATION

Clean Sky is a coordinated pro-gramme, with many interactionsbetween the different ITDs, and nota simple juxtaposition of interests.

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Clean Sky has already proven itself to bean essential instrument in drivingtechnology and innovation for the future ofaviation. Given the ambitious targets setout in Europe’s vision for aviation,"Flightpath 2050", it is essential that wekeep our foot firmly on the accelerator.A commitment to delivering the mostpromising technologies in aviation - thefastest growing transport sector with>4,8%/a - at the earliest possibleopportunity, – necessarily meansmaintaining technological leadership,

creating high skilled jobs, increasingtransport efficiency, sustaining economicalprosperity and driving environmentalimprovements worldwide.Indeed, a second generation J.U. willundoubtedly be required under the nextFramework Programme if we are tomaintain our current trajectory, whilstembracing ever-more ambitiousobjectives, such as using large-scaleintegrated demonstrators for newconfigurations.

Conclusion

CONTACT DETAILS

Axel KREINSenior Vice-Presidentof Research and TechnologyAirbus [email protected]: +33 (0)5 62 11 06 44

Eric DAUTRIATExecutive DirectorClean Sky [email protected]: +32 22 21 81 52

This, together with the globalnature of the technology evaluator,demands a “systems” approachwhich has not been a feature ofEuropean programmes until now.

Clean Sky being an aeronauticalenterprise, one might say that it hasnow reached full cruising speed,after a delayed take-off. Initialhurdles have been overcome andthe necessary budgetary flexibilityand operational effectivenessachieved. Later, it will be up to themarket to put these technologiesinto operation. The first inter-mediate achievements are emer-ging: Partial tests in flight, produc-tion of innovative parts, etc.

These parts of the puzzle willbegin to be assembled towards2013, when the largest demon-strators start to turn over.In the meantime, the environ-mental benefits must be secured.Clean Sky has proven to be a veryessential instrument in drivingsubstantial technology advancementfor the future of aeronautics.

Article written by Eric DAUTRIAT(Copyright used by permission - Clean Sky)

ALTIMETERSFA

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From barometric to radioIn 1928, Paul Kollsman invented a barometric altimeter making it possible for pilotsto fly using only their gauges, such as in heavy fog or at night when visibility is limited.The aviator, James H. Doolittle, became the first pilot to take off, fly and land duringthe first all-instrument flight on a Consolidated N-Y-2 biplane, on September 24 1929.

What timeis it?

Well, I’m not quite sure.

Can’t youtell with your sophi

sticated

watch showing time all over

the world?

No, Sir. This isn’t a w

atch but one

of the earliest barome

tric altimeters

ever invented.

“”

The history of the altimeter begins with the invention of the mercury barometer, the firstdevice to measure air pressure. As early as in 1643, Italian physicist EvangelistaTorricelli (a pupil of Galileo), filled a tube with mercury. One end of the tube was closed;the other open end was turned upside down and inserted in a cup of mercury. Becausethe air exerted pressure on the mercury in the cup, about thirty inches of mercuryremained in the tube.

Nowadays, the Radio Altimeter sends out radio waves to a fixed point on the groundand then determines the altitude by the time it takes the wave to bounce back. Unlikethe barometric altimeter, a Radio Altimeter won't be affected by the weather. However,a Radio Altimeter is usually only used when the aircraft descends below 2,500ft asdetailed in this FAST magazine (Radio Altimeter systems - page 15), and regularmaintenance practices are recommended.

airbus magazine fast 49

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