cover fast 11/03/98 21:55 page 1 - · pdf file03-11-1998 · for a300/a300-600/a310...

Cover FAST 11/03/98 21:55 Page 1

Publisher: Airbus Industrie Customer Services, 1 rond-point Maurice Bellonte, 31707 Blagnac Cedex, FranceEditor: Denis Dempster, Product MarketingTelephone +33 (0)5 61 93 39 29, Telex AIRBU 530526F, Telefax +33 (0)5 61 93 27 67 Graphic design: Agnès Lacombe, Customer Services Marketing Photo-engraving: Passion Graphic, 60 boulevard Déodat de Séverac, 31027 Toulouse Cedex, FrancePrinter: Escourbiac, 5 avenue Marcel Dassault, 31502 Toulouse Cedex, France

This issue of FAST has been printed on paper produced without using chlorine, to reduce waste and help to conserve natural resources. 'Every little helps'.

FAST may be read on Internet http://www.airbus.com

The articles herein may be reprinted without permission except where copyright source is indicated, but with acknowledgement to Airbus Industrie. Articles which may be subject to ongoing review must have their accuracy verified prior to reprint. The statements made herein do not constitute an offer. They are based on the assumptions shown and are expressed in good faith. Where the supporting grounds for these statements are not shown, the Company will be pleased to explain the basis thereof.

AIRBUSTECHNICALDIGEST

NUMBER 22MARCH 1998

HYDRAULIC SYSTEMPREVENTING LEAKSJEROME QUENESCOURT

THE PORTABLE WATER DETECTION TOOLFOR A300/A300-600/A310 AIRCRAFTRENE SAVOIE AND MARIE-SOPHIE CALAIS

1717IMPLEMENTING JAR-OPS WITHAIRBUS INDUSTRIE OPERATIONAL DOCUMENTATIONGUY DI SANTO

THE INTERNATIONAL REGULATORY CLIMATEANDREW S. Mc CLYMONT 1111

7FUEL SYSTEMDETECTING LEAKS USING HELIUMALAIN MARECHAL AND ALAIN DENINOTTI

25LIGHTNING STRIKES AND AIRBUS FLY-BY-WIRE AIRCRAFTCAPTAIN CHRIS KRAHE 25

28AIM-FANS WINS GROWING NUMBER OF ORDERSJEAN-PIERRE DAMBRINE 28

30CUSTOMER SERVICES CONFERENCES 30THE FIRST AVIATION REGULATION? 3131RESIDENT CUSTOMER SUPPORTREPRESENTATION 3232

FAST / NUMBER 22 1

FAST 22/p1 � p6 11/03/98 23:45 Page 1

FAST / NUMBER 22 3FAST / NUMBER 222

Jérome QuenescourtHydraulic Systems Engineer

Eng. & Technical SupportAirbus Industrie

Customer Services Directorate

In an earlierarticle

"Hydraulic system- Working

practices" (FASTN°13), somefundamental

working practiceswere detailed,

aimed to reducethe number of

leaks. Since then,a dedicatedmonitoring

programme hasbeen launched and

working groupsformed to further

minimise theoccurrence

of leaks. The purpose ofthis article is to

provide guidelinesfor maintenance

personnel toreduce the

frequency of leakseven further.

HYDRAULIC SYSTEMPreventing leaks

Thereare three as-pects to bec o n s i d e r e d

when looking for the causes of leaks:● design, ● control of quality in production,● maintenance.

Only the manufacturer can do some-thing about the first two itemsandAirbus Industrie is continuallystudying how repetitive defects can bedesigned out of the system either bychanging the design, the supplier and/or the production process (Figure 1).

DESIGN

Part of the designer’s work is to makethe maintenance interventions, sched-uled and unscheduled, as infrequent aspossible, and the maintenance practicesas simple as possible. The TechnicalDesign Directives for the hydraulic sys-tem, written originally for the A300, arelargely still applicable, however therehave been some changes such as thegreater use of titanium piping which islighter than stainless steel and lessprone to pin-hole corrosion; the gener-alised use of flareless fittings; installa-tion of built-in Hydraulic SystemMonitoring Units and the qualificationof new fluids and methods of repairingpipes.

Further work is being done to en-hance the built-in test and monitoringcapabilities of the system allowing eas-ier and more accurate maintenance in-terventions as early as possible in thedegradation sequence.

QUALITY IN PRODUCTION

Computer aided design and manufac-turing of pipes have greatly improvedthe quality of the installation of piperuns particularly in areas having manypipes with multiple bends in closeproximity. The improved installationallied with:● respect of torque values and propertightening methods,● stress free installation,● seal installation with lubricants● use of dedicated tools,all lead to trouble free installations.

The Airbus Industrie ProcessSpecification (AIPS) sets the standardsfor production and installation of thehydraulic systems for all the Airbusaircraft.

One area where manufacturer andoperator have to be particularly vigilantis in the inadvertent acquisition of "bo-gus" parts that do not always conformwith basic quality standards. Hydraulicsystems have been known to sufferfrom the installation of these parts, par-

ticularly seals, which has led to rein-forced audits at vendors and informa-tion being transmitted to the operatorsthrough the Service Information Letter(SIL 29-064).

MAINTENANCE

Maintenance can be divided into twogroups - preventive and corrective.

Preventive maintenance

In the Maintenance Planning Docu-ments (MPD) there are scheduled taskswhich are defined to ensure hydraulicsystem integrity and avoid leaks. Thesetasks are found in the Zonal InspectionProgramme under System checks (typi-cal defects are shown in Figures 2 to 6).

Zonal inspection programme

The zonal programme asks for visualinspection of various aircraft systemsincluding the hydraulic system, at vari-ous locations (wheel well bay, underfloor, engine pylons, wing trailing edgeetc). It is during the visual inspectionsthat anomalies can be identified andcorrected, such as:● presence of seepage (Figure 2)● loose or missing ties, spacers orclamp blocks, (Figures 3, 4, 6)● damaged pipe-lines● loose connections● line chafing (Figure 6 and 7).

System checks

Some system checks are fundamentalto ensure the system integrity and toprevent future damage. For instance,regular hydraulic fluid sampling to al-low the operator to maintain the fluidquality within given limits (aciditylevel, chlorine and water content) andtherefore avoid component erosion orcorrosion. Moreover, as soon as com-ponents become eroded, internal leak-age rates increase, fluid is laminated,

Figure 1Hydraulic Leak Monitoring

*ARCS*ARCS: Airbus Representative

Communication System

Codingevents

Resident CustomerRepresentative Office

• StudyAirline/fleet

• Trackingrepeaters

• Effectivenessof improvement(SB)

Airbus Data Base (FORDSREP)

Analysis

Information flow: about 2000 events in 1997 (all A/C types)

TECH LOG

Extraction

Leakevents

New leakevents

LeakDataBase

FAST 22/p1 � p6 11/03/98 23:48 Page 2

Jérome QuenescourtHydraulic Systems Engineer

Eng. & Technical SupportAirbus Industrie

Customer Services Directorate

In an earlierarticle

"Hydraulic system- Working

practices" (FASTN°13), somefundamental

working practiceswere detailed,

aimed to reducethe number of

leaks. Since then,a dedicatedmonitoring

programme hasbeen launched and

working groupsformed to further

minimise theoccurrence

of leaks. The purpose ofthis article is to

provide guidelinesfor maintenance

personnel toreduce the

frequency of leakseven further.

HYDRAULIC SYSTEMPreventing leaks

Thereare three as-pects to bec o n s i d e r e d

when looking for the causes of leaks:● design, ● control of quality in production,● maintenance.

Only the manufacturer can do some-thing about the first two itemsandAirbus Industrie is continuallystudying how repetitive defects can bedesigned out of the system either bychanging the design, the supplier and/or the production process (Figure 1).

DESIGN

Part of the designer’s work is to makethe maintenance interventions, sched-uled and unscheduled, as infrequent aspossible, and the maintenance practicesas simple as possible. The TechnicalDesign Directives for the hydraulic sys-tem, written originally for the A300, arelargely still applicable, however therehave been some changes such as thegreater use of titanium piping which islighter than stainless steel and lessprone to pin-hole corrosion; the gener-alised use of flareless fittings; installa-tion of built-in Hydraulic SystemMonitoring Units and the qualificationof new fluids and methods of repairingpipes.

Further work is being done to en-hance the built-in test and monitoringcapabilities of the system allowing eas-ier and more accurate maintenance in-terventions as early as possible in thedegradation sequence.

QUALITY IN PRODUCTION

Computer aided design and manufac-turing of pipes have greatly improvedthe quality of the installation of piperuns particularly in areas having manypipes with multiple bends in closeproximity. The improved installationallied with:● respect of torque values and propertightening methods,● stress free installation,● seal installation with lubricants● use of dedicated tools,all lead to trouble free installations.

The Airbus Industrie ProcessSpecification (AIPS) sets the standardsfor production and installation of thehydraulic systems for all the Airbusaircraft.

One area where manufacturer andoperator have to be particularly vigilantis in the inadvertent acquisition of "bo-gus" parts that do not always conformwith basic quality standards. Hydraulicsystems have been known to sufferfrom the installation of these parts, par-

ticularly seals, which has led to rein-forced audits at vendors and informa-tion being transmitted to the operatorsthrough the Service Information Letter(SIL 29-064).

MAINTENANCE

Maintenance can be divided into twogroups - preventive and corrective.

Preventive maintenance

In the Maintenance Planning Docu-ments (MPD) there are scheduled taskswhich are defined to ensure hydraulicsystem integrity and avoid leaks. Thesetasks are found in the Zonal InspectionProgramme under System checks (typi-cal defects are shown in Figures 2 to 6).

Zonal inspection programme

The zonal programme asks for visualinspection of various aircraft systemsincluding the hydraulic system, at vari-ous locations (wheel well bay, underfloor, engine pylons, wing trailing edgeetc). It is during the visual inspectionsthat anomalies can be identified andcorrected, such as:● presence of seepage (Figure 2)● loose or missing ties, spacers orclamp blocks, (Figures 3, 4, 6)● damaged pipe-lines● loose connections● line chafing (Figure 6 and 7).

System checks

Some system checks are fundamentalto ensure the system integrity and toprevent future damage. For instance,regular hydraulic fluid sampling to al-low the operator to maintain the fluidquality within given limits (aciditylevel, chlorine and water content) andtherefore avoid component erosion orcorrosion. Moreover, as soon as com-ponents become eroded, internal leak-age rates increase, fluid is laminated,

Figure 1Hydraulic Leak Monitoring

*ARCS*ARCS: Airbus Representative

Communication System

Codingevents

Resident CustomerRepresentative Office

• StudyAirline/fleet

• Trackingrepeaters

• Effectivenessof improvement(SB)

Airbus Data Base (FORDSREP)

Analysis

Information flow: about 2000 events in 1997 (all A/C types)

TECH LOG

Extraction

Leakevents

New leakevents

LeakDataBase

FAST 22/p1 � p6 11/03/98 23:48 Page 2

This is an example of why trackingof component reliability may justify aneed for a fixed time between overhaul(TBO), replacement of a part, or em-bodiment of a modification.

The keys issues for seal reliability areproduct manufacturing quality andproper installation.

Manufacturing quality

The product manufacturing quality hasbeen recently at the focal point of in-service failures on the A330/A340 pro-grams. (Refer to SIL 29-064). As a re-sult, two vendors have been removedfrom the approved list of suppliers be-cause of identified quality deficiencyon some of their products. Three othervendors (Le Joint Francais, DowtyU.K, and Parker) have been auditedand their standard of manufacturingquality judged satisfactory.

Installation

Chapter 20 of the Aircraft MaintenanceManual recommends use of certaintools and provides other advice forproper installation of seals.

In the previous article in FAST itwas stated that "Seals, O-rings andpacking washers should be smearedwith MCS-352 lubricant or hydraulicfluid". It has recently been discoveredthat the application of MCS-352 on thethreads of plug-in unions can have anegative effect, causing the seal to besqueezed and damaged (Figure 5).

For plug-in unions hydraulic fluidshould be used as a lubricant.

There are generally three origins ofpipe failure:● chafing,● installation under stress,● corrosion.

High quality of manufacture of thepipes allowing good installation canlargely prevent these types of failures.A recent audit performed on all Airbuspipe production centres revealed thatmanufacturing processes and tech-niques are well adapted and controlled,with the use of :● numerical controlled bending ma-chines and improved knowledge ofspring back effect, ● laser dimensional check for every in-dividual manufactured pipe,● chlorine free pipe cleaning,● laser marking.

Compliance with installation ruleswill avoid chafing and pre-stressed installations. Design will also help

FAST / NUMBER 22 5

Plug-in union

O-Ring

Lubricant on the threads

Manifold port

Pinching

At final tighteningthe seal is pinched

between the plug-in union and the edge of

the chamfer. Thispinching damages the

rubber on the outer surface of the seal

During tightening of the union the lubricant

fills the groove and pushes the seal out

FAST / NUMBER 224

system operating temperature increaseswhich further degrades the fluid, in-creasing its acidity level. This neverending process will continue until af-fected components and fluid arechanged as necessary. This exampleshows the prevention role of the sys-tems checks required by the MPD bothfor mandatory tasks such as internalleak checks and economic tasks such asfluid sampling.

Corrective maintenance

For corrective maintenance to be effec-tive and long lasting a certain level ofbasic maintenance training and knowl-edge of the specific aircraft are re-quired. These requirements were de-tailed in the article in FAST 13. Avideo, poster and related documentationare available from the address at theend of this article.

Most leaks are discovered during linemaintenance - on the walk-around,night stop or pre-flight checks - andthey have to be corrected as quickly aspossible. This may require the installa-tion of a temporary repair kit ratherthan a permanent hydraulic tube repairrequiring pipe manufacturing capabil-ity. In this case SIL 29-069 "Pipe repairkit" and SIL 29-067 "Hydraulic tubingrepairs" provide useful information.

Other SILs providing related infor-mation on the various leak sources are :● 29-032 for A300/A300-600/A310,● 29-064 for A319/A320/A321,● 29-066 for A330/A340.

LEAK SOURCES

Components

A list of available and essential compo-nent improvements is provided in thededicated SILs listed above. The em-bodiment of those product improve-ments on an attrition basis or throughdedicated retrofit should provide a sig-nificant increase in system reliability.

Tracking of component reliability is necessary to meet on-condition/con-dition-monitoring maintenance require-ments. For hydraulic systems it con-cerns the main components such as theengine driven pumps (EDP) and powertransfer units.

There is evidence that those compo-nents, even when a proper overhaul hasbeen performed, do not recover theirfull potential after the overhaul, whichaffects their long term reliability. Also,if a part such as an EDP valve block isnot changed at the overhaul of the EDP,then it will accumulate many years ofoperation which may lead to naturaldamage, fatigue or corrosion.

Figure 2Detection of typical fluid seepage by stains on talcum powder

Figure 3Pipe clamping (spacer) loosening and moving

Figure 4Detail of spacer loosening and moving

Figure 6Risk of chafing due to loose clamping

Figure 5Effect of lubricant on plug-in union threads

FAST 22/p1 � p6 11/03/98 23:50 Page 4

This is an example of why trackingof component reliability may justify aneed for a fixed time between overhaul(TBO), replacement of a part, or em-bodiment of a modification.

The keys issues for seal reliability areproduct manufacturing quality andproper installation.

Manufacturing quality

The product manufacturing quality hasbeen recently at the focal point of in-service failures on the A330/A340 pro-grams. (Refer to SIL 29-064). As a re-sult, two vendors have been removedfrom the approved list of suppliers be-cause of identified quality deficiencyon some of their products. Three othervendors (Le Joint Francais, DowtyU.K, and Parker) have been auditedand their standard of manufacturingquality judged satisfactory.

Installation

Chapter 20 of the Aircraft MaintenanceManual recommends use of certaintools and provides other advice forproper installation of seals.

In the previous article in FAST itwas stated that "Seals, O-rings andpacking washers should be smearedwith MCS-352 lubricant or hydraulicfluid". It has recently been discoveredthat the application of MCS-352 on thethreads of plug-in unions can have anegative effect, causing the seal to besqueezed and damaged (Figure 5).

For plug-in unions hydraulic fluidshould be used as a lubricant.

There are generally three origins ofpipe failure:● chafing,● installation under stress,● corrosion.

High quality of manufacture of thepipes allowing good installation canlargely prevent these types of failures.A recent audit performed on all Airbuspipe production centres revealed thatmanufacturing processes and tech-niques are well adapted and controlled,with the use of :● numerical controlled bending ma-chines and improved knowledge ofspring back effect, ● laser dimensional check for every in-dividual manufactured pipe,● chlorine free pipe cleaning,● laser marking.

Compliance with installation ruleswill avoid chafing and pre-stressed installations. Design will also help

FAST / NUMBER 22 5

Plug-in union

O-Ring

Lubricant on the threads

Manifold port

Pinching

At final tighteningthe seal is pinched

between the plug-in union and the edge of

the chamfer. Thispinching damages the

rubber on the outer surface of the seal

During tightening of the union the lubricant

fills the groove and pushes the seal out

FAST / NUMBER 224

system operating temperature increaseswhich further degrades the fluid, in-creasing its acidity level. This neverending process will continue until af-fected components and fluid arechanged as necessary. This exampleshows the prevention role of the sys-tems checks required by the MPD bothfor mandatory tasks such as internalleak checks and economic tasks such asfluid sampling.

Corrective maintenance

For corrective maintenance to be effec-tive and long lasting a certain level ofbasic maintenance training and knowl-edge of the specific aircraft are re-quired. These requirements were de-tailed in the article in FAST 13. Avideo, poster and related documentationare available from the address at theend of this article.

Most leaks are discovered during linemaintenance - on the walk-around,night stop or pre-flight checks - andthey have to be corrected as quickly aspossible. This may require the installa-tion of a temporary repair kit ratherthan a permanent hydraulic tube repairrequiring pipe manufacturing capabil-ity. In this case SIL 29-069 "Pipe repairkit" and SIL 29-067 "Hydraulic tubingrepairs" provide useful information.

Other SILs providing related infor-mation on the various leak sources are :● 29-032 for A300/A300-600/A310,● 29-064 for A319/A320/A321,● 29-066 for A330/A340.

LEAK SOURCES

Components

A list of available and essential compo-nent improvements is provided in thededicated SILs listed above. The em-bodiment of those product improve-ments on an attrition basis or throughdedicated retrofit should provide a sig-nificant increase in system reliability.

Tracking of component reliability is necessary to meet on-condition/con-dition-monitoring maintenance require-ments. For hydraulic systems it con-cerns the main components such as theengine driven pumps (EDP) and powertransfer units.

There is evidence that those compo-nents, even when a proper overhaul hasbeen performed, do not recover theirfull potential after the overhaul, whichaffects their long term reliability. Also,if a part such as an EDP valve block isnot changed at the overhaul of the EDP,then it will accumulate many years ofoperation which may lead to naturaldamage, fatigue or corrosion.

Figure 2Detection of typical fluid seepage by stains on talcum powder

Figure 3Pipe clamping (spacer) loosening and moving

Figure 4Detail of spacer loosening and moving

Figure 6Risk of chafing due to loose clamping

Figure 5Effect of lubricant on plug-in union threads

FAST 22/p1 � p6 11/03/98 23:50 Page 4

with improved clamping definition (adjustable brackets) and dampening ofpressure pulsation of pumps.

Ageing affects the integrity of pipeinstallations (Figures 3 to 7) justifyingthe importance of periodic inspectionchecks such as in the zonal inspection.Typical ageing effects are:● reduced efficiency of clamp blocks

due to loosening, wear or damage, ● corrosion development (exposure tocontaminants such as saline atmos-phere, spillage from toilets),● damage to pipe surfaces duringmaintenance.

Pipe fittings

Maintenance is a common source ofleakage when loosening is due to un-der-tightening (often found on large fit-tings) and damage is due to over-tight-ening, generally found on aluminiumfittings or small fittings and due tocracking from frequent loosening andtightening. The main development infitting technology has been the intro-duction of more reliable flarelessunions. However experience has shownthat there is no substitute for systematiccompliance with correct tightening pro-cedures and use of the correct tools.

Airbus Industrie is studying more"damage tolerant" fitting designs suchas Rosan (Figure 8) and alternativetightening techniques which can copewith vibration and a maintenance envi-ronment where use of torque wrenchesis not common practice.

FAST / NUMBER 226

Adapter

O-Ring

Serrations

Lockring

CONCLUSION

Lubricant MCS-352 should not be used on the threads of the plug-in unions. Although the hydraulic leak rate on a fleet-widebasis is approaching a satisfactory level it can and will be improved. Further efforts by Airbus Industrie and the vendors toimprove hydraulic system reliability together with preventive maintenance actions applied by operators when necessary andproper application of procedures, will keep the hydraulic leak rates within an acceptable level. For this purpose, customers’feedback on in-service experience is vital.

Airbus Industrie will assist any operator suffering from a perceived excessive leak rate to initiate a leak preventive pro-gramme. This programme has been successfully implemented by a number of operators one of whom experienced a reduc-tion in leak rates by 50%. ■

Figure 8Rosan fitting definition: union and port

Figure 7Risk of chafing due to small clearance

For further information please contact: AIRBUS INDUSTRIE Engineering Services, Engineer Hydraulic Systems, Mr TORBJÖRN KETTEL

FAST / NUMBER 22 7

Alain MaréchalStructure Engineering SupportA300/A310/A330/A340Airbus Industrie

Alain DeninottiQuality Assurance Product ManagerAirbus Industrie

ntil now curingfuel leaks has been a relatively difficult

operation for operators and manufacturers alike. The methods available to identify the leak pathshave been air blowingassociated with soapy waterto detect bubbles (a methodas old as aviation itself),and suction associated with dye penetrant, neither method being very successful. This article describes a new detecting techniqueusing helium gas developedby Airbus Industrie.

FFFFUUUUEEEELLLL SSSSYYYYSSSSTTTTEEEEMMMMD e t e c t i n g l e a k s u s i n g h e l i u m

FAST 22/p1 � p6 11/03/98 23:53 Page 6

with improved clamping definition (adjustable brackets) and dampening ofpressure pulsation of pumps.

Ageing affects the integrity of pipeinstallations (Figures 3 to 7) justifyingthe importance of periodic inspectionchecks such as in the zonal inspection.Typical ageing effects are:● reduced efficiency of clamp blocks

due to loosening, wear or damage, ● corrosion development (exposure tocontaminants such as saline atmos-phere, spillage from toilets),● damage to pipe surfaces duringmaintenance.

Pipe fittings

Maintenance is a common source ofleakage when loosening is due to un-der-tightening (often found on large fit-tings) and damage is due to over-tight-ening, generally found on aluminiumfittings or small fittings and due tocracking from frequent loosening andtightening. The main development infitting technology has been the intro-duction of more reliable flarelessunions. However experience has shownthat there is no substitute for systematiccompliance with correct tightening pro-cedures and use of the correct tools.

Airbus Industrie is studying more"damage tolerant" fitting designs suchas Rosan (Figure 8) and alternativetightening techniques which can copewith vibration and a maintenance envi-ronment where use of torque wrenchesis not common practice.

FAST / NUMBER 226

Adapter

O-Ring

Serrations

Lockring

CONCLUSION

Lubricant MCS-352 should not be used on the threads of the plug-in unions. Although the hydraulic leak rate on a fleet-widebasis is approaching a satisfactory level it can and will be improved. Further efforts by Airbus Industrie and the vendors toimprove hydraulic system reliability together with preventive maintenance actions applied by operators when necessary andproper application of procedures, will keep the hydraulic leak rates within an acceptable level. For this purpose, customers’feedback on in-service experience is vital.

Airbus Industrie will assist any operator suffering from a perceived excessive leak rate to initiate a leak preventive pro-gramme. This programme has been successfully implemented by a number of operators one of whom experienced a reduc-tion in leak rates by 50%. ■

Figure 8Rosan fitting definition: union and port

Figure 7Risk of chafing due to small clearance

For further information please contact: AIRBUS INDUSTRIE Engineering Services, Engineer Hydraulic Systems, Mr TORBJÖRN KETTEL

FAST / NUMBER 22 7

Alain MaréchalStructure Engineering SupportA300/A310/A330/A340Airbus Industrie

Alain DeninottiQuality Assurance Product ManagerAirbus Industrie

ntil now curingfuel leaks has been a relatively difficult

operation for operators and manufacturers alike. The methods available to identify the leak pathshave been air blowingassociated with soapy waterto detect bubbles (a methodas old as aviation itself),and suction associated with dye penetrant, neither method being very successful. This article describes a new detecting techniqueusing helium gas developedby Airbus Industrie.

FFFFUUUUEEEELLLL SSSSYYYYSSSSTTTTEEEEMMMMD e t e c t i n g l e a k s u s i n g h e l i u m

FAST 22/p1 � p6 11/03/98 23:53 Page 6

Fuel tanks in modern commercial air-liners are housed principally in thewings, and the wing structure is also thefuel tank structure; there are no rubbertanks or other forms of inner wallswithin the wings. Wing structures arecomposed of large skin panels, dozensof ribs and stringers, and thousands ofbolts and rivets covered with a sealantto prevent fuel seepage (Figure 1). Thisstructure is flexible, as anyone who hasflown in turbulent weather will havenoticed, as they watch the wing tipsmoving up and down. Eventually fuelseepage does occur and the leaks be-come evident on the outer surface ofthe skin. The visible point of seepage is

at the end of the leak path (Figure 2a)and an efficient repair requires that theorigin of the leak path (or paths) isidentified and properly sealed. If not,there is a high risk that the leak will ap-pear again, and quite often it does.

THE INNOVATIVEAPPROACH

Airbus Industrie investigated severalleak path detection methods and has se-lected and developed a new detectiontechnique using helium as a tracer gasto allow easier detection of the sourceof the leak (Figure 2b).

This technique, which was developed

INSIDE

OUTSIDE

Helium

Gas leak=

Location ofsealant

deterioration

INSIDE

OUTSIDE

Leakingarea

Figure 2Different phases of detection method

Figure 4Example of artificial compression chamber around the lug shown on Figure 3

Figure 1Wing structure (typical)

in cooperation with two companies,Helitech and Varian, and with the sup-port of different maintenance centresand airlines, was the only one whichoffered the required sensitivity and reli-ability, and is a great step forwardcompared to the methods used previ-ously.

THE HELIUM TECHNIQUE

Helium is a non-toxic inert gas whichdoes not react chemically with anyother element, making it intrinsicallysafe. In addition, due to its small rela-tive molecular mass, it has a high pene-tration capability allowing it to passthrough the smallest gaps. Helium isparticularly interesting for this leak de-tection task because of its low concen-tration in the atmosphere (five particlesper million) which allows easy detec-tion of any small increase in this pro-portion. Finally it is an industrial gasavailable anywhere in the world.

Pressurised helium is already used inAirbus production lines to test forleaks. The leak is visually located ex-ternally (Figure 3) and the source isidentified internally by creating a com-pression chamber around the leak point(Figure 4) and filling it with helium un-der pressure thereby forcing the heliumback up the leak channel into the fueltank.

2a Identification of a leak 2b Use of helium gas as tracer gas

Figure 3Example of visual location of fuel leaking from flap track forward attachment lug

Resealing areaand potential leak paths

Access manhole

FAST22 p7 � 10 11/03/98 23:36 Page 8

Fuel tanks in modern commercial air-liners are housed principally in thewings, and the wing structure is also thefuel tank structure; there are no rubbertanks or other forms of inner wallswithin the wings. Wing structures arecomposed of large skin panels, dozensof ribs and stringers, and thousands ofbolts and rivets covered with a sealantto prevent fuel seepage (Figure 1). Thisstructure is flexible, as anyone who hasflown in turbulent weather will havenoticed, as they watch the wing tipsmoving up and down. Eventually fuelseepage does occur and the leaks be-come evident on the outer surface ofthe skin. The visible point of seepage is

at the end of the leak path (Figure 2a)and an efficient repair requires that theorigin of the leak path (or paths) isidentified and properly sealed. If not,there is a high risk that the leak will ap-pear again, and quite often it does.

THE INNOVATIVEAPPROACH

Airbus Industrie investigated severalleak path detection methods and has se-lected and developed a new detectiontechnique using helium as a tracer gasto allow easier detection of the sourceof the leak (Figure 2b).

This technique, which was developed

INSIDE

OUTSIDE

Helium

Gas leak=

Location ofsealant

deterioration

INSIDE

OUTSIDE

Leakingarea

Figure 2Different phases of detection method

Figure 4Example of artificial compression chamber around the lug shown on Figure 3

Figure 1Wing structure (typical)

in cooperation with two companies,Helitech and Varian, and with the sup-port of different maintenance centresand airlines, was the only one whichoffered the required sensitivity and reli-ability, and is a great step forwardcompared to the methods used previ-ously.

THE HELIUM TECHNIQUE

Helium is a non-toxic inert gas whichdoes not react chemically with anyother element, making it intrinsicallysafe. In addition, due to its small rela-tive molecular mass, it has a high pene-tration capability allowing it to passthrough the smallest gaps. Helium isparticularly interesting for this leak de-tection task because of its low concen-tration in the atmosphere (five particlesper million) which allows easy detec-tion of any small increase in this pro-portion. Finally it is an industrial gasavailable anywhere in the world.

Pressurised helium is already used inAirbus production lines to test forleaks. The leak is visually located ex-ternally (Figure 3) and the source isidentified internally by creating a com-pression chamber around the leak point(Figure 4) and filling it with helium un-der pressure thereby forcing the heliumback up the leak channel into the fueltank.

2a Identification of a leak 2b Use of helium gas as tracer gas

Figure 3Example of visual location of fuel leaking from flap track forward attachment lug

Resealing areaand potential leak paths

Access manhole

FAST22 p7 � 10 11/03/98 23:36 Page 8

FAST / NUMBER 2210

The procedure must start with a clearmapping of the fuel leak on the outersurface of the tank (precise leak loca-tion and approximate leak rate) thenthe tank can be defuelled, drained andvented until it becomes completely dry.Before entering the tank, all the safetychecks have to be performed to ensureadequate ventilation and acceptablefuel vapour concentration.

An artificial compression chamber(Figure 5a) over the leaking area has tobe created. This is simply done by pen-etrating one corner of a plastic bagwith the rubber hose from the heliumsupply and sealing the join with sealantand aluminium tape. The open end ofthe plastic bag is attached to the skin ofthe wing around the leak, also by alu-minium tape. This simple method canbe easily adapted to awkward situa-tions as shown on page 7 where theleak is from a flap track attachment fit-ting. This artificial chamber must beable to withstand a maximum internalpressure of 200 mbar. When this hasbeen done, the helium injection canstart at a constant pressure.The initialpressure choice depends on the kind ofleak (rate, location) and must be basedon knowledge of the structure and po-tential leak paths. Then the jet of he-lium being forced into the tank has tobe found. By moving the detection"sniffer" (Figure 5b) probe inside thetank, there will be various sound fre-quencies emitted by the detection de-vice depending on how far the probe isfrom the jet of helium (and the originof the leakage). During this operation,it could be necessary to increase the in-jection pressure. It should not be for-gotten that more than one leak may ex-ist in the same area. Therefore it couldbe necessary to repeat this operationseveral times. In this case it is recom-mended to vent the area between twodetection operations.

The artificial compression chambershould not be removed, because whenthe repair has been performed it can beused to check, in the same way, the qual-ity of the repair. This will prevent re-fuelling and de-fuelling of the tank if thequality of the repair is not acceptable.

CONCLUSION

Conventional methods for detecting fuel leaks are now becoming obsolete. This helium technique has been tested and finetuned on several aircraft. It is now the most efficient and reliable method of identifying fuel leak sources. It is cost effectiveas a much lower number of manhours are required to cure fuel leaks and it reduces significantly the aircraft downtime. Inaddition it also confirms the integrity of the repair, avoiding the use of fuel. This operation alone can easily save four daysof ground time.

Airbus Industrie highly recommends that operators apply this procedure, which is described in SIL. 57-091 applicable toall Airbus aircraft types. ■

INSIDE

OUTSIDE

Fuel tank

Helium injectedinto the chamber

Artificial compressionchamber taped overexternal leaking point

Fuel tank

Leak source detected by helium detector nozzle "sniffer"

INSIDE

OUTSIDE

5b Detection

Figure 5Detection phases5a Injection

nternational cooperation on civil aircraft regulations and certification has been in existence to some extent, initially a small extent, for more than 50 years.

It has been increasing in recent years as Europe slowly draws together many diversenational bodies to create a single Joint Aviation Authority to act on behalf of eachEuropean country member. At the same time, the level of cooperation on both sides of theAtlantic and with other regions of the world is also increasing in a manner which should -in the long term - achieve a practical worldwide certification process and an improvedoverall safety regulation system.That ideal is some way ahead, but is becoming a possibility for aircraft airworthinesscertification, if political restraints and perceived sovereignty protection policies can beavoided. It may take longer for operational "control" to reach such a common goal. We need to persuade the politicians to support our justifiable intentions for the overallbenefit of all. See the following article on JAR-OPS.

The International Regulatory Climate is a continually changing environment but there is an overall major purpose to promote an enhanced air safety environment for thetravelling public, without unreasonably increasing the regulatory burden on theAuthorities, the manufacturers and the operators.

The main theme to be remembered, and from time to time we need to be reminded, is that we are all aiming at the same target - safe, reliable, cost effective air transport.

Associated with this theme is an essential need to create a working environment ofconfidence, and positive technical relationships between all involved parties.

Andrew S. McClymont, Director Certification Strategies, Product Integrity , Airbus Industrie

FAST / NUMBER 22 11

THE ITHE INNTERNTERNAATITIOONALNALREGULREGULAATOTORRY CLIMY CLIMAATETE

The A330 concurrent JAA and FAA Type Certification Ceremony, 21st October 1993.

Seated left to right: Mr B. Ziegler (SVP Engineering Airbus Industrie), Mr C. Frantzen (DGAC France),Mr V. von Tein (Chief Operating Officer Airbus Industrie), Mr M. Dambaek (JAA Executive BoardChairman) and Mr D. Curtis (FAA Transport Airplane Directorate representative) plus other participants from France, Germany, Italy, The Netherlands, United Kingdom, Austria, Belgium,Portugal, JAA and FAA.

FAST22 p7 � 10 11/03/98 23:38 Page 10

FAST / NUMBER 2210

The procedure must start with a clearmapping of the fuel leak on the outersurface of the tank (precise leak loca-tion and approximate leak rate) thenthe tank can be defuelled, drained andvented until it becomes completely dry.Before entering the tank, all the safetychecks have to be performed to ensureadequate ventilation and acceptablefuel vapour concentration.

An artificial compression chamber(Figure 5a) over the leaking area has tobe created. This is simply done by pen-etrating one corner of a plastic bagwith the rubber hose from the heliumsupply and sealing the join with sealantand aluminium tape. The open end ofthe plastic bag is attached to the skin ofthe wing around the leak, also by alu-minium tape. This simple method canbe easily adapted to awkward situa-tions as shown on page 7 where theleak is from a flap track attachment fit-ting. This artificial chamber must beable to withstand a maximum internalpressure of 200 mbar. When this hasbeen done, the helium injection canstart at a constant pressure.The initialpressure choice depends on the kind ofleak (rate, location) and must be basedon knowledge of the structure and po-tential leak paths. Then the jet of he-lium being forced into the tank has tobe found. By moving the detection"sniffer" (Figure 5b) probe inside thetank, there will be various sound fre-quencies emitted by the detection de-vice depending on how far the probe isfrom the jet of helium (and the originof the leakage). During this operation,it could be necessary to increase the in-jection pressure. It should not be for-gotten that more than one leak may ex-ist in the same area. Therefore it couldbe necessary to repeat this operationseveral times. In this case it is recom-mended to vent the area between twodetection operations.

The artificial compression chambershould not be removed, because whenthe repair has been performed it can beused to check, in the same way, the qual-ity of the repair. This will prevent re-fuelling and de-fuelling of the tank if thequality of the repair is not acceptable.

CONCLUSION

Conventional methods for detecting fuel leaks are now becoming obsolete. This helium technique has been tested and finetuned on several aircraft. It is now the most efficient and reliable method of identifying fuel leak sources. It is cost effectiveas a much lower number of manhours are required to cure fuel leaks and it reduces significantly the aircraft downtime. Inaddition it also confirms the integrity of the repair, avoiding the use of fuel. This operation alone can easily save four daysof ground time.

Airbus Industrie highly recommends that operators apply this procedure, which is described in SIL. 57-091 applicable toall Airbus aircraft types. ■

INSIDE

OUTSIDE

Fuel tank

Helium injectedinto the chamber

Artificial compressionchamber taped overexternal leaking point

Fuel tank

Leak source detected by helium detector nozzle "sniffer"

INSIDE

OUTSIDE

5b Detection

Figure 5Detection phases5a Injection

nternational cooperation on civil aircraft regulations and certification has been in existence to some extent, initially a small extent, for more than 50 years.

It has been increasing in recent years as Europe slowly draws together many diversenational bodies to create a single Joint Aviation Authority to act on behalf of eachEuropean country member. At the same time, the level of cooperation on both sides of theAtlantic and with other regions of the world is also increasing in a manner which should -in the long term - achieve a practical worldwide certification process and an improvedoverall safety regulation system.That ideal is some way ahead, but is becoming a possibility for aircraft airworthinesscertification, if political restraints and perceived sovereignty protection policies can beavoided. It may take longer for operational "control" to reach such a common goal. We need to persuade the politicians to support our justifiable intentions for the overallbenefit of all. See the following article on JAR-OPS.

The International Regulatory Climate is a continually changing environment but there is an overall major purpose to promote an enhanced air safety environment for thetravelling public, without unreasonably increasing the regulatory burden on theAuthorities, the manufacturers and the operators.

The main theme to be remembered, and from time to time we need to be reminded, is that we are all aiming at the same target - safe, reliable, cost effective air transport.

Associated with this theme is an essential need to create a working environment ofconfidence, and positive technical relationships between all involved parties.

Andrew S. McClymont, Director Certification Strategies, Product Integrity , Airbus Industrie

FAST / NUMBER 22 11

THE ITHE INNTERNTERNAATITIOONALNALREGULREGULAATOTORRY CLIMY CLIMAATETE

The A330 concurrent JAA and FAA Type Certification Ceremony, 21st October 1993.

Seated left to right: Mr B. Ziegler (SVP Engineering Airbus Industrie), Mr C. Frantzen (DGAC France),Mr V. von Tein (Chief Operating Officer Airbus Industrie), Mr M. Dambaek (JAA Executive BoardChairman) and Mr D. Curtis (FAA Transport Airplane Directorate representative) plus other participants from France, Germany, Italy, The Netherlands, United Kingdom, Austria, Belgium,Portugal, JAA and FAA.

FAST22 p7 � 10 11/03/98 23:38 Page 10

Harmoniation ofJAR 25 and FAR 25

Deletion of national variantsCreation of JAR 25

Creation of a joint Europe/America process

Joint certification in EuropeSeparate certifications

FAR 25National Requirements

JAR 25 + National variants

FAR 25

JAR 25FAR 25

EASAFAA

HarmonisedJAR 25FAR 25

1993 The future1988 19921983

need to retain them. If they still feltthere was a justifiable need, then theyhad to be reviewed with the otherEuropean NAAs to try and reach acommon agreement to justify a require-ment different from the basic JAR 25.

If agreement or justification regard-ing a National Variant could not bereached within the NAAs then the orig-inating NAA was required to drop thatregulation. A difficult and sometimestime consuming process to find justifi-able legal means to remove a previ-ously well considered, and possiblylong time applied, design requirement.

The Airbus A320 type certificationexperience (1983-1988) was funda-mental in promoting the removal of allJAR 25 National Variants. This wasachieved at JAR 25 Change 13 in 1989,which was used for the European JointCertification of the Airbus A340.

However, it is well worth remember-ing that no Authority should be imple-menting a regulation which cannot besensibly and acceptably justified. Thatpoint should of course be part of everynew rule proposal justification. It ismore difficult later to remove a regula-tion which might no longer be justifi-able for the original reasons.

THE PRESENT DAY STATUS

Work has also been going on for morethan 10 years to reduce the number ofdifferences between the basic require-ment standards on each side of the

Atlantic with a major attempt at har-monisation of JAR 25 and FAR 25.There has also been an attempt to caterfor appropriate regulatory evolutionduring the life of a long productionmodel of an aircraft.

This latter case was addressed in theInternational Certification ProceduresTask Force during the last 8 years, setup to produce a "harmonised" jointlyagreed means to handle derivative air-craft, i.e. basic model evolution overmany years of continuous production,in an attempt to enhance the safety cer-tification levels during the life of suchtype designs. Derivatives of aircraftwhich originally went into service in1968 are being designed, developedand certificated up to 30 years later.

European harmonisation has beenslowly progressing since the late1960's, through the certification ofConcorde, Airbus A300 and later mod-els, BAe146, Jetstream 41, Saab340/2000, Dassault, Dornier, ATR42/72, CASA 235, etc... The certifica-tion procedures, and regulations, haveevolved with experience such thatnowadays a single JAA Team carriesout the Type Certification investigationand agreement of findings of compli-ance on behalf of all the NAAs in theJAA. However, this process, whichdoes work, is only by "gentleman'sagreement" in the JAA "Club ofAuthorities". The creation of a singleEuropean Aviation Safety Authoritywill greatly improve the present

FAST / NUMBER 22 13

HISTORY

It was through the principles and activ-ities of the International Civil AviationOrganization (I.C.A.O.) that guidelineswere produced in an attempt to createcommon technical standards in all as-pects of air transport regulation. Theseinternationally accepted guidelines, de-fined in the technical ICAO Annexes,provide the basic principles to enablethe air transport industry to operatesafely, reliably, regularly and legally.

The broad objectives from theDecember 1944 Chicago Conventionon International Civil Aviation were :● Safe and orderly development ofInternational Civil Aviation● Sound and economical operation forInternational Air Transport Services,and equality of opportunity.

These objectives remain valid today,providing the background to the de-fined rules, regulations and require-ments which are the basic roots of theflight safety levels achieved in the airtransport industry.

There are more than 180 contractingstates associated with ICAO, and itsAir Navigation Commission, and thereare 18 ICAO Annexes covering the rel-evant Standards and RecommendedPractices (SARPS).

It is the word "recommended", how-ever, which creates some of the longterm problems associated with the im-plementation of these ICAO SARPS -these "International Standards".

Each participating country defines itsown "legal" standards and notifiesICAO, and all other participating coun-tries, how they enable (or accept) com-pliance to be achieved with theInternational Standards. In fact, thenormal process is to formally notify de-fined non adherence or non compliancewith specific ICAO recommendationsin each countries’ internal legal "pack-age" of regulations. But this "flexible"way of behaving creates the possibilityof varying interpretations of regula-tions, because many countries are notprepared to give up sovereignty, or le-gal control of their own regulations.Some of the ICAO-SARPS are quitegeneral in content and leave someroom for national interpretations.

There is also a problem to be ad-dressed because a few countries claim-ing that they comply with the ICAOSARPS have in fact no structured avia-tion authority and no related nationalregulations.

AIRCRAFT CERTIFICATION

There are, or have been, two normaltypes of aircraft certification exercises -

the basic domestic certification underthe general control of the Authority ofthe State of Design and Manufactureand then the validation of that basiccertification by other countries.

The validations have tended to lookat acknowledged differences in the reg-ulatory standard between the domesticType Certification Basis and the re-quired Certification Basis of the vali-dating or importing country.

The validation team, apart from nec-essary aircraft design familiarisationand getting an informative groundingin the basic certification of the aircraft,generally concentrates on how certifi-cation can be found with the definedregulatory differences.

This additional certification/valida-tion work programme, with the impli-cation of possible design changes to theaeroplane, can be a major burden to themanufacturer, particularly when a num-ber of countries have significant na-tional differences. Regulatory differ-ences have in the past caused someexpensive design changes with ques-tionable cost effective safety benefit.

HARMONISATION OFREGULATIONS AND

PROCEDURES

Harmonisation of regulations and pro-cedures has been a major target of jointwork both in Europe and across theAtlantic.

As a result of strong Industry pres-sure both in Europe and in NorthAmerica, it has been possible to makeprogress in harmonising the variousairworthiness standards in order to re-duce significant differences in regula-tions and interpretations (Figure 1).

Taking the European scene as an ex-ample, this problem of national differ-ences was behind the early attempts tocreate Joint Aviation Requirements(JAR) as a common set of regulations.Unfortunately, they were in the begin-ning, not very common, because alarge number of National Variants wereincluded, to meet long held basic certi-fication standards which some coun-tries were not initially prepared to giveup. Although the JAR 25 large trans-port aeroplane design regulations wereoriginally based on the FAR 25 NorthAmerican format, all the NationalVariants raised defined differences.

Following the experience with realjoint certification and validation pro-jects in Europe on the Airbus A320 andSaab 340 during the 1980s, theNational Aviation Authorities (NAA)in Europe were required to review eachof their National Variants to confirmwhether there was still a justifiable

FAST / NUMBER 2212

Figure 1Harmonising regulations and procedures - The Airbus experience

FAST22 p11 � 16 11/03/98 23:20 Page 12

Harmoniation ofJAR 25 and FAR 25

Deletion of national variantsCreation of JAR 25

Creation of a joint Europe/America process

Joint certification in EuropeSeparate certifications

FAR 25National Requirements

JAR 25 + National variants

FAR 25

JAR 25FAR 25

EASAFAA

HarmonisedJAR 25FAR 25

1993 The future1988 19921983

need to retain them. If they still feltthere was a justifiable need, then theyhad to be reviewed with the otherEuropean NAAs to try and reach acommon agreement to justify a require-ment different from the basic JAR 25.

If agreement or justification regard-ing a National Variant could not bereached within the NAAs then the orig-inating NAA was required to drop thatregulation. A difficult and sometimestime consuming process to find justifi-able legal means to remove a previ-ously well considered, and possiblylong time applied, design requirement.

The Airbus A320 type certificationexperience (1983-1988) was funda-mental in promoting the removal of allJAR 25 National Variants. This wasachieved at JAR 25 Change 13 in 1989,which was used for the European JointCertification of the Airbus A340.

However, it is well worth remember-ing that no Authority should be imple-menting a regulation which cannot besensibly and acceptably justified. Thatpoint should of course be part of everynew rule proposal justification. It ismore difficult later to remove a regula-tion which might no longer be justifi-able for the original reasons.

THE PRESENT DAY STATUS

Work has also been going on for morethan 10 years to reduce the number ofdifferences between the basic require-ment standards on each side of the

Atlantic with a major attempt at har-monisation of JAR 25 and FAR 25.There has also been an attempt to caterfor appropriate regulatory evolutionduring the life of a long productionmodel of an aircraft.

This latter case was addressed in theInternational Certification ProceduresTask Force during the last 8 years, setup to produce a "harmonised" jointlyagreed means to handle derivative air-craft, i.e. basic model evolution overmany years of continuous production,in an attempt to enhance the safety cer-tification levels during the life of suchtype designs. Derivatives of aircraftwhich originally went into service in1968 are being designed, developedand certificated up to 30 years later.

European harmonisation has beenslowly progressing since the late1960's, through the certification ofConcorde, Airbus A300 and later mod-els, BAe146, Jetstream 41, Saab340/2000, Dassault, Dornier, ATR42/72, CASA 235, etc... The certifica-tion procedures, and regulations, haveevolved with experience such thatnowadays a single JAA Team carriesout the Type Certification investigationand agreement of findings of compli-ance on behalf of all the NAAs in theJAA. However, this process, whichdoes work, is only by "gentleman'sagreement" in the JAA "Club ofAuthorities". The creation of a singleEuropean Aviation Safety Authoritywill greatly improve the present

FAST / NUMBER 22 13

HISTORY

It was through the principles and activ-ities of the International Civil AviationOrganization (I.C.A.O.) that guidelineswere produced in an attempt to createcommon technical standards in all as-pects of air transport regulation. Theseinternationally accepted guidelines, de-fined in the technical ICAO Annexes,provide the basic principles to enablethe air transport industry to operatesafely, reliably, regularly and legally.

The broad objectives from theDecember 1944 Chicago Conventionon International Civil Aviation were :● Safe and orderly development ofInternational Civil Aviation● Sound and economical operation forInternational Air Transport Services,and equality of opportunity.

These objectives remain valid today,providing the background to the de-fined rules, regulations and require-ments which are the basic roots of theflight safety levels achieved in the airtransport industry.

There are more than 180 contractingstates associated with ICAO, and itsAir Navigation Commission, and thereare 18 ICAO Annexes covering the rel-evant Standards and RecommendedPractices (SARPS).

It is the word "recommended", how-ever, which creates some of the longterm problems associated with the im-plementation of these ICAO SARPS -these "International Standards".

Each participating country defines itsown "legal" standards and notifiesICAO, and all other participating coun-tries, how they enable (or accept) com-pliance to be achieved with theInternational Standards. In fact, thenormal process is to formally notify de-fined non adherence or non compliancewith specific ICAO recommendationsin each countries’ internal legal "pack-age" of regulations. But this "flexible"way of behaving creates the possibilityof varying interpretations of regula-tions, because many countries are notprepared to give up sovereignty, or le-gal control of their own regulations.Some of the ICAO-SARPS are quitegeneral in content and leave someroom for national interpretations.

There is also a problem to be ad-dressed because a few countries claim-ing that they comply with the ICAOSARPS have in fact no structured avia-tion authority and no related nationalregulations.

AIRCRAFT CERTIFICATION

There are, or have been, two normaltypes of aircraft certification exercises -

the basic domestic certification underthe general control of the Authority ofthe State of Design and Manufactureand then the validation of that basiccertification by other countries.

The validations have tended to lookat acknowledged differences in the reg-ulatory standard between the domesticType Certification Basis and the re-quired Certification Basis of the vali-dating or importing country.

The validation team, apart from nec-essary aircraft design familiarisationand getting an informative groundingin the basic certification of the aircraft,generally concentrates on how certifi-cation can be found with the definedregulatory differences.

This additional certification/valida-tion work programme, with the impli-cation of possible design changes to theaeroplane, can be a major burden to themanufacturer, particularly when a num-ber of countries have significant na-tional differences. Regulatory differ-ences have in the past caused someexpensive design changes with ques-tionable cost effective safety benefit.

HARMONISATION OFREGULATIONS AND

PROCEDURES

Harmonisation of regulations and pro-cedures has been a major target of jointwork both in Europe and across theAtlantic.

As a result of strong Industry pres-sure both in Europe and in NorthAmerica, it has been possible to makeprogress in harmonising the variousairworthiness standards in order to re-duce significant differences in regula-tions and interpretations (Figure 1).

Taking the European scene as an ex-ample, this problem of national differ-ences was behind the early attempts tocreate Joint Aviation Requirements(JAR) as a common set of regulations.Unfortunately, they were in the begin-ning, not very common, because alarge number of National Variants wereincluded, to meet long held basic certi-fication standards which some coun-tries were not initially prepared to giveup. Although the JAR 25 large trans-port aeroplane design regulations wereoriginally based on the FAR 25 NorthAmerican format, all the NationalVariants raised defined differences.

Following the experience with realjoint certification and validation pro-jects in Europe on the Airbus A320 andSaab 340 during the 1980s, theNational Aviation Authorities (NAA)in Europe were required to review eachof their National Variants to confirmwhether there was still a justifiable

FAST / NUMBER 2212

Figure 1Harmonising regulations and procedures - The Airbus experience

FAST22 p11 � 16 11/03/98 23:20 Page 12

The Industry wishes to see the newEuropean Aviation Safety Authority inplace by the year 2000.

Meanwhile there is a continuing needto maintain dialogue and improveworking arrangements between the ma-jor aviation safety control organisationsacross the world. There are signs ofprogress in this field with the conclu-sions and actions coming from the 13thand 14th Annual FAA/JAA/TCA andIndustry Harmonisation Conferencesheld respectively in San Diego in June1996 and in Berlin in June 1997.

The Industry and the Authoritieshave looked into a major problemwhich has arisen regarding the depth ofinvolvement expected to be undertakenby an Authority when validating thecertification of an already type certifi-cated aircraft, and have proposed a newconcept regarding this problem whichis worthy of serious consideration.

The Safety Regulation Codes of FAR25 and JAR 25 provide generallyequivalent levels of safety. The largeRegulatory Harmonisation programmewhich started 5 or 6 years ago, underARAC, was a good principle to follow,but it has become very costly and timeconsuming in terms of Industry andAuthority manpower resources. Amore efficient way to meet the generalneed for harmonisation has to befound.

A new idea on how to handle thisgrowing concern emerged, after somehard talking between and within theAuthority and Industry group. It startsfrom the general view that the twocodes are similar in concept althoughnot necessarily identical in regulationor interpretation in all aspects. Itshould therefore be possible to con-sider each code "equivalent", and aType Certification based on one code

FAST / NUMBER 22 15

"heavy" process. The relationship be-tween the JAA and other European or-ganisations is shown in Figure 2.

The harmonisation between Europeand the Western side of the Atlantic istaking its time also. In 1989, a targetwas declared at the annual JAA/FAA/Transport Canada and Industryjoint meeting in Bordeaux, to go formajor harmonisation of the FAR 25and JAR 25 regulations. At about thesame time, the US Government,through the FAA, set up their AviationRulemaking Advisory Committee(ARAC) structure and invited partici-pation from Canadian and EuropeanAuthorities and Industry.

After a slow and difficult start, atleast in the tasking of the ARACTransport Aeroplane and EnginesIssues Group, the review work and theattempts to reach consensus conclu-sions have produced some productiveresults, notably in flight and structuresregulations. In other subjects such as

cabin safety, there has been little or noconsensus and some difficult decisionswill have to be taken eventually by theAuthorities.

There is a general concern that inspite of all the significant resources putinto the ARAC process by bothIndustry and Authorities, the lack ofproductive agreed output in many areaswill reduce Industry commitment, andmay eventually fail to achieve the orig-inal good harmonisation ideal.

But by including Industry at a suit-able early stage of the review , and inthe drafting process, there ought to beless Industry opposition to the finalproposed regulatory product.

The regulations do need to be har-monised to an acceptable level beforethe implementation of joint proceduresagreed across the Atlantic, can reallyresult in the easing of the certificationburden on manufacturers, by havingone single certification process on be-half of all Authorities.

THE FUTURE PROSPECTS

The International Regulatory Climateis a variable environment. The princi-ples of harmonised regulation and har-monised joint certification processes,acceptable to all, are a proper ideal tostrive for in the civil aviation safetyscene. We need to maintain the effortto reach the ideal in spite of some un-expected set backs. The main way tocontinue to make progress is to talk to-gether and work together in a coopera-tive and open manner.

The "getting together" in Europe isbeing promoted both by Industry (man-ufacturers and now gradually the oper-ators) and most of the NAAs of theJAA. The major problem is how to cre-ate a single legal entity with the rele-vant powers to act on behalf of all themembers. The main feature to resolveis the formal handing over of sover-eignty for aviation safety matters bythe members governments, or safetybodies. There is also the question ofcovering the costs of a EuropeanAviation Safety Authority.

Recent discussions reviewed a possi-ble legal treaty or convention with rele-vant connection to the EuropeanUnion; the EU being the appropriateEuropean political body overseeing theadministration by the EuropeanCommission.

There are legal difficulties to be re-solved but generally there is a growingintent to see it happen and eventuallythe political will to make it happen willbe there. The first signs of politicalcommitment were seen at the EuropeanCouncil of Ministers in December 1996.

FAST / NUMBER 2214

European Civil Aviation Council (ECAC) (36)

Eurocontrol (23)

LithuaniaRepublic of MacedoniaMoldovaRomania

European Union (EU) (15)

European Free Trade Area(EFTA) (3)

CyprusCzech RepublicHungary MaltaSloveniaSlovakiaTurkey

AustriaBelgiumDenmarkFranceGermanyGreeceIrelandItalyLuxembourgNetherlandsPortugalSpainSwedenUK

SwitzerlandNorway

ArmeniaBulgariaCroatiaEstoniaLatvia

Poland Monaco

Finland

Iceland

JAA (27)

The Type Certificates for the A330

Figure 2JAA and European organisations

FAST22 p11 � 16 11/03/98 23:21 Page 14

The Industry wishes to see the newEuropean Aviation Safety Authority inplace by the year 2000.

Meanwhile there is a continuing needto maintain dialogue and improveworking arrangements between the ma-jor aviation safety control organisationsacross the world. There are signs ofprogress in this field with the conclu-sions and actions coming from the 13thand 14th Annual FAA/JAA/TCA andIndustry Harmonisation Conferencesheld respectively in San Diego in June1996 and in Berlin in June 1997.

The Industry and the Authoritieshave looked into a major problemwhich has arisen regarding the depth ofinvolvement expected to be undertakenby an Authority when validating thecertification of an already type certifi-cated aircraft, and have proposed a newconcept regarding this problem whichis worthy of serious consideration.

The Safety Regulation Codes of FAR25 and JAR 25 provide generallyequivalent levels of safety. The largeRegulatory Harmonisation programmewhich started 5 or 6 years ago, underARAC, was a good principle to follow,but it has become very costly and timeconsuming in terms of Industry andAuthority manpower resources. Amore efficient way to meet the generalneed for harmonisation has to befound.

A new idea on how to handle thisgrowing concern emerged, after somehard talking between and within theAuthority and Industry group. It startsfrom the general view that the twocodes are similar in concept althoughnot necessarily identical in regulationor interpretation in all aspects. Itshould therefore be possible to con-sider each code "equivalent", and aType Certification based on one code

FAST / NUMBER 22 15

"heavy" process. The relationship be-tween the JAA and other European or-ganisations is shown in Figure 2.

The harmonisation between Europeand the Western side of the Atlantic istaking its time also. In 1989, a targetwas declared at the annual JAA/FAA/Transport Canada and Industryjoint meeting in Bordeaux, to go formajor harmonisation of the FAR 25and JAR 25 regulations. At about thesame time, the US Government,through the FAA, set up their AviationRulemaking Advisory Committee(ARAC) structure and invited partici-pation from Canadian and EuropeanAuthorities and Industry.

After a slow and difficult start, atleast in the tasking of the ARACTransport Aeroplane and EnginesIssues Group, the review work and theattempts to reach consensus conclu-sions have produced some productiveresults, notably in flight and structuresregulations. In other subjects such as

cabin safety, there has been little or noconsensus and some difficult decisionswill have to be taken eventually by theAuthorities.

There is a general concern that inspite of all the significant resources putinto the ARAC process by bothIndustry and Authorities, the lack ofproductive agreed output in many areaswill reduce Industry commitment, andmay eventually fail to achieve the orig-inal good harmonisation ideal.

But by including Industry at a suit-able early stage of the review , and inthe drafting process, there ought to beless Industry opposition to the finalproposed regulatory product.

The regulations do need to be har-monised to an acceptable level beforethe implementation of joint proceduresagreed across the Atlantic, can reallyresult in the easing of the certificationburden on manufacturers, by havingone single certification process on be-half of all Authorities.

THE FUTURE PROSPECTS

The International Regulatory Climateis a variable environment. The princi-ples of harmonised regulation and har-monised joint certification processes,acceptable to all, are a proper ideal tostrive for in the civil aviation safetyscene. We need to maintain the effortto reach the ideal in spite of some un-expected set backs. The main way tocontinue to make progress is to talk to-gether and work together in a coopera-tive and open manner.

The "getting together" in Europe isbeing promoted both by Industry (man-ufacturers and now gradually the oper-ators) and most of the NAAs of theJAA. The major problem is how to cre-ate a single legal entity with the rele-vant powers to act on behalf of all themembers. The main feature to resolveis the formal handing over of sover-eignty for aviation safety matters bythe members governments, or safetybodies. There is also the question ofcovering the costs of a EuropeanAviation Safety Authority.

Recent discussions reviewed a possi-ble legal treaty or convention with rele-vant connection to the EuropeanUnion; the EU being the appropriateEuropean political body overseeing theadministration by the EuropeanCommission.

There are legal difficulties to be re-solved but generally there is a growingintent to see it happen and eventuallythe political will to make it happen willbe there. The first signs of politicalcommitment were seen at the EuropeanCouncil of Ministers in December 1996.

FAST / NUMBER 2214

European Civil Aviation Council (ECAC) (36)

Eurocontrol (23)

LithuaniaRepublic of MacedoniaMoldovaRomania

European Union (EU) (15)

European Free Trade Area(EFTA) (3)

CyprusCzech RepublicHungary MaltaSloveniaSlovakiaTurkey

AustriaBelgiumDenmarkFranceGermanyGreeceIrelandItalyLuxembourgNetherlandsPortugalSpainSwedenUK

SwitzerlandNorway

ArmeniaBulgariaCroatiaEstoniaLatvia

Poland Monaco

Finland

Iceland

JAA (27)

The Type Certificates for the A330

Figure 2JAA and European organisations

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should in principle be acceptable tocountries normally using the othercode. With that principle in mind wecan concentrate the harmonisationwork on key subjects where known dif-ferences in regulatory implementationare causing undue burden to industry,without any relevant safety benefit.

This proposal needs careful consider-ation by all parties before implementa-tion. A very tight time schedule wasproposed in 1996 to review and imple-ment the details, and real progress wasachieved in June 1997, with the jointagreement to two principle documentsdefining the future way ahead.

SAFETY OVERSIGHT

The interests of a growing number ofcountries, or groups of countries, in theworld aviation safety scene are also be-ing addressed. This fact, and the recentaggressive FAA policy regardingsafety oversight, demonstrate the needto promote further aviation safety ini-tiatives in a coordinated global fashion.Increasing interaction between ICAOand Member States is required, and ishappening, to achieve such progress ina practical and controlled manner.

A number of regional aviation safetyseminars have been, and are being, or-ganised in various parts of the world,supported by the recognised safetybodies, and by manufacturers and oper-ators and authorities. These initiativesand events provide opportunities forimproving safety awareness by com-munication and dialogue within andbetween all involved parties.

As a model for the creation of a re-gional aviation safety organisationmeeting the intent of the ICAO princi-ples, the example of the EuropeanJAA, and its future evolution into a sin-gle authority acting on behalf of allEuropean countries, can be offered. Itshows how large and small countriescan work together for a common cause.There is already a large body of re-cently harmonised regulatory materialcovering all aspects of safety regula-tion, which will soon also be availablein different languages.

Positive progress, using theEuropean example, is taking placeamong the countries of South Asia, andalso in the Caribbean and in SouthAmerica. Recent increases in ICAO ac-tivity and influence in these matters arewelcomed.

FAST / NUMBER 2216

CONCLUSION

Enhancement of the present aviation safety levels must be achieved in the coming years to meet the increasing volume of airtransport traffic with a reduction in the actual accident numbers, in order to maintain public confidence in this major produc-tive industry. Continuing worldwide cooperation to ameliorate the International Regulatory climate is essential to improvesafety. Airbus Industrie is an active participant with the airworthiness authorities in the effort to achieve that aim. ■

FAST / NUMBER 22 17

ll major aviation countries have a regulatorysystem for applying and monitoring the safety

standards of their civil aviation industry (see article“THE INTERNATIONAL REGULATORY CLIMATE” onpage 11). The International Civil AviationOrganisation (ICAO), sets minimum standards forinternational air transport but the national standards ofmany countries exceed these.

The Joint Aviation Authorities (JAA) are anassociated body of the European Civil AviationConference (ECAC) representing the civil aviationregulatory authorities of 27 European States (*) whohave agreed to co-operate in developing andimplementing common safety regulatory standards andprocedures. This co-operation is intended to providehigh and consistent standards of safety based on theICAO standards. Much emphasis is also placed onharmonising JAA requirements (JARs) with theregulations of the USA (FARs).

The JAA undertook a major harmonisation task to produce common operating regulationacceptable to all participating countries.The result, called JAR-OPS, defines the JointAviation Requirements in the fields of aircraftoperation. ICAO Annex 6 has been selected to providethe basic structure of JAR-OPS, but with additionalsub-divisions where considered appropriate. Thecontent of Annex 6 has been used and added to wherenecessary by making use of existing Europeanregulations and the Federal Aviation Requirements ofthe United States of America where acceptable.

JAR-OPS Part 1 covering Commercial AirTransportation by aeroplanes was adopted by the JAACommittee at the end of March 1995, the first issuebeing published on 22 May 1995.

A Notice of Proposed Amendment (NPA) wasissued in December 1996 to include new materialwhich could not be developed before the first issueand to take into account some amendments made toICAO Annex 6.

(*) Austria, Belgium, Cyprus, Czech Republic, Denmark,Finland, France, Germany, Greece, Hungary, Iceland,Ireland, Italy, Luxembourg, Malta, Monaco, Netherlands,Norway, Poland, Portugal, Slovakia, Slovenia, Spain,Sweden, Switzerland, Turkey and United Kingdom

Guy Di SantoDepartment Manager Airlines Operations SupportAirbus IndustrieCustomer Services Directorate

with Airbus Industrie Operational Documentation

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