SIST EN 4533-003:2018
(Main)Aerospace series - Fibre optic systems - Handbook - Part 003: Looming and installation practices
Aerospace series - Fibre optic systems - Handbook - Part 003: Looming and installation practices
This handbook considers best practice during initial design and how the practices chosen affect through life support of the installation. Looming and installation practices are a critical aspect of any aircraft electrical/avionics installation. In order to provide a reliable and efficient system it is important that the fibre optic installation is designed for reliability and maintainability.
This document provides technical advice and assistance to designers and engineers on the incorporation of fibre optic harnesses into an airframe, while, wherever possible, maintaining maximum compliance with current aircraft electrical harness procedures.
All topics that are related to Installation of optical cables are addressed in EN 3197.
These rules are applicable for fibre optic cables and connectors defined by EN specifications.
Luft- und Raumfahrt - Faseroptische Systemtechnik - Handbuch - Teil 003: Praktiken zur Fertigung und Installation von Leitungsbündeln
Série aérospatiale - Systèmes des fibres optiques - Manuel d'utilisation - Partie 003: Règles de l'art pour la fabrication et l'installation des harnais
Le présent manuel présente les règles de l’art pendant la conception initiale et l’impact des pratiques
choisies tout au long du cycle de vie le soutien de l’installation. Les règles de l’art pour la fabrication et
l’installation sont des aspects critiques de toute installation électrique/avionique à usage aéronautique.
Afin de fournir un système fiable et efficace, il est important de concevoir l’installation des fibres
optiques en pensant à leur fiabilité et à leur maintenabilité.
Le présent document fournit des conseils et une assistance techniques aux concepteurs et aux ingénieurs
au sujet de l’incorporation des harnais de fibres optiques dans la cellule d'avion, tout en restant, autant
que possible, au maximum conformes aux procédures courantes relatives aux harnais électriques à usage
aéronautique.
Tous les sujets relatifs à l’installation des câbles optiques sont traités dans l’EN 3197.
Ces règles sont applicables aux connecteurs et câbles optiques définis dans les specifications EN.
Aeronavtika - Sistemi iz optičnih vlaken - Priročnik - 003. del: Postopki za izdelavo in namestitev vezalnega pasovja
General Information
Relations
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Luft- und Raumfahrt - Faseroptische Systemtechnik - Handbuch - Teil 003: Praktiken zur Fertigung und Installation von LeitungsbündelnSérie aérospatiale - Systèmes des fibres optiques - Manuel d'utilisation - Partie 003: Règles de l'art pour la fabrication et l'installation des harnaisAerospace series - Fibre optic systems - Handbook - Part 003: Looming and installation practices49.060Aerospace electric equipment and systems33.180.01VSORãQRFibre optic systems in generalICS:Ta slovenski standard je istoveten z:EN 4533-003:2017SIST EN 4533-003:2018en,fr,de01-marec-2018SIST EN 4533-003:2018SLOVENSKI
STANDARDSIST EN 4533-003:20091DGRPHãþD
SIST EN 4533-003:2018
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 4533-003
December
t r s y ICS
v {ä r x r Supersedes EN
v w u uæ r r uã t r r xEnglish Version
Aerospace series æ Fibre optic systems æ Handbook æ Part
r r uã Looming and installation practices Série aérospatiale æ Systèmes des fibres optiques æ Manuel d 5utilisation æ Partie
r r uã Règles de l 5art pour la fabrication et l 5installation des harnais
Luftæ und Raumfahrt æ Faseroptische Systemtechnik æ Handbuch æ Teil
r r uã Praktiken zur Fertigung und Installation von Leitungsbündeln This European Standard was approved by CEN on
t u July
t r s yä
egulations which stipulate the conditions for giving this European Standard the status of a national standard without any alterationä Upætoædate lists and bibliographical references concerning such national standards may be obtained on application to the CENæCENELEC Management Centre or to any CEN memberä
translation under the responsibility of a CEN member into its own language and notified to the CENæCENELEC Management Centre has the same status as the official versionsä
CEN members are the national standards bodies of Austriaá Belgiumá Bulgariaá Croatiaá Cyprusá Czech Republicá Denmarká Estoniaá Finlandá Former Yugoslav Republic of Macedoniaá Franceá Germanyá Greeceá Hungaryá Icelandá Irelandá Italyá Latviaá Lithuaniaá Luxembourgá Maltaá Netherlandsá Norwayá Polandá Portugalá Romaniaá Serbiaá Slovakiaá Sloveniaá Spainá Swedená Switzerlandá Turkey and United Kingdomä
EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels
9
t r s y CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Membersä Refä Noä EN
v w u uæ r r uã t r s y ESIST EN 4533-003:2018
EN 4533-003:2017 (E) 2 Contents Page European Foreword . 3 Introduction . 4 1 Scope . 5 2 Normative references . 5 3 Initial design considerations . 5 3.1 General . 5 3.2 System design considerations . 7 3.3 Practical harness routing considerations . 10 3.4 Securing and attachment mechanisms . 10 3.5 Protection mechanisms . 13 3.6 Installation mechanisms . 16 3.7 Through life support . 16 3.8 Enabling Fibre optic cable re-termination . 17 3.9 Handling . 19
SIST EN 4533-003:2018
EN 4533-003:2017 (E) 3 European Foreword This document (EN 4533-003:2017) has been prepared by the Aerospace and Defence Industries Association of Europe - Standardization (ASD-STAN). After enquiries and votes carried out in accordance with the rules of this Association, this Standard has received the approval of the National Associations and the Official Services of the member countries of ASD, prior to its presentation to CEN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2018 and conflicting national standards shall be withdrawn at the latest by June 2018. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 4533-003:2006. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. SIST EN 4533-003:2018
EN 4533-003:2017 (E) 4 Introduction a) The Handbook This handbook aims to provide general guidance for experts and non-experts alike in the area of designing, installing, and supporting fibre-optic systems on aircraft. Where appropriate more detailed sources of information are referenced throughout the text. It is arranged in 4 parts, which reflect key aspects of an optical harness life cycle, namely: Part 001: Termination methods and tools Part 002: Test and measurement
Part 003: Looming and installation practices Part 004: Repair, maintenance, cleaning and inspection b) Background It is widely accepted in the aerospace industry that photonic technology significant advantages over conventional electrical hardware. These include massive signal bandwidth capacity, electrical safety, and immunity of passive fibre-optic components to the problems associated with electromagnetic interference (EMI). Significant weight savings can also be realized in comparison to electrical harnesses which may require heavy screening. To date, the EMI issue has been the critical driver for airborne fibre-optic communications systems because of the growing use of non-metallic aerostructures. However, future avionic requirements are driving bandwidth specifications from 10’s of Mbits/s into the multi-Gbits/s regime in some cases, i.e. beyond the limits of electrical interconnect technology. The properties of photonic technology can potentially be exploited to advantage in many avionic applications, such as video/sensor multiplexing, flight control signalling, electronic warfare, and entertainment systems, as well as sensor for monitoring aerostructure. The basic optical interconnect fabric or `optical harness’ is the key enabler for the successful introduction of optical technology onto commercial and military aircraft. Compared to the mature telecommunications applications, an aircraft fibre-optic system needs to operate in a hostile environment (e.g. temperature extremes, humidity, vibration, and contamination) and accommodate additional physical restrictions imposed by the airframe (e.g. harness attachments, tight bend radii requirements, and bulkhead connections). Until recently, optical harnessing technology and associated practices were insufficiently developed to be applied without large safety margins. In addition, the international standards did not adequately cover many aspects of the life cycle. The lack of accepted standards thus lead to airframe specific hardware and support. These factors collectively carried a significant cost penalty (procurement and through-life costs), that often made an optical harness less competitive than an electrical equivalent. This situation is changing with the adoption of more standardized (telecoms type) fibre types in aerospace cables and the availability of more ruggedized COTS components. These improved developments have been possible due to significant research collaboration between component and equipment manufacturers as well as the end use airframers. SIST EN 4533-003:2018
EN 4533-003:2017 (E) 5 1 Scope This handbook considers best practice during initial design and how the practices chosen affect through life support of the installation. Looming and installation practices are a critical aspect of any aircraft electrical/avionics installation. In order to provide a reliable and efficient system it is important that the fibre optic installation is designed for reliability and maintainability. This document provides technical advice and assistance to designers and engineers on the incorporation of fibre optic harnesses into an airframe, while, wherever possible, maintaining maximum compliance with current aircraft electrical harness procedures. All topics that are related to Installation of optical cables are addressed in EN 3197. These rules are applicable for fibre optic cables and connectors defined by EN specifications. 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
EN 3197, Aerospace series — Design and installation of aircraft electrical and optical interconnection systems EN 4533-001, Aerospace series — Fibre optic systems — Handbook — Part 001: Termination methods and tools EN 4533-002, Aerospace series — Fibre optic systems — Handbook — Part 002: Test and measurement EN 4533-004, Aerospace series — Fibre optic systems — Handbook — Part 004: Repair, maintenance and inspection 3 Initial design considerations 3.1 General Wherever possible the installation of fibre optic links and bundles should aim to mirror that of copper systems and comply as much as possible with current general aircraft electrical harness procedures. There are numerous installation specifications detailing the requirements for the routing of copper based harnesses, however they are very similar in content, therefore fibre optic harness routing will have to fulfil the following criteria: a) Accessibility for inspection and maintenance; b) Prevent or minimise the risk of damage from: Chafing, scraping or abrasion; Use as handholds or as support for personal equipment; Damage by personnel moving within the aircraft; Stowage or movement of cargo; Battery electrolytes and fumes; SIST EN 4533-003:2018
EN 4533-003:2017 (E) 6 Stones, ice, mud and burst tyre debris in landing gear bays; Combat damage (to the maximum extent practicable); Loose or moving parts; Moisture and fluids; Localised high temperatures; Frequent mating and de-mating of connectors; Exposure to high temperature/high vibration areas. Copper installations are prone to electrical interference and their use is restricted in “volatile” zones. Fibre optic cables are immune to electrical interference and are ideally suited for use in, or routing through “volatile” zones. Examples of areas that fibre optic harnesses may provide a better solution over copper include: a) Areas where there are high levels of electrical field; b) Areas where electric fields need to be kept to a minimum, e.g. compass deviation; c) Routing through and close to fuel tanks; d) Close proximity to electrically initiated explosive devices (EIEDs) and their systems. During the design phase of a fibre optic installation routing considerations need to be addressed when determining the optimum routing, these include: a) System criticality; b) Harness accessibility, improves on-aircraft repair and maintenance, but should not degrade system protection; c) System segregation and redundancy, maximisation of damage limitation; d) Accessibility of connectors; e) System and component repair and maintenance issues (it is noted that design of common harness lengths on an aircraft may improve the supportability (common spares inventory) if repairs are required); f) Introduction of dormant fibre in harnesses and/or extra fibre lengths may reduce on-aircraft repair times. SIST EN 4533-003:2018
EN 4533-003:2017 (E) 7 3.2 System design considerations 3.2.1 Introduction In the design of a fibre optic harness, the link topology and the available routing path on the platform will dictate the physical length of the harness and any required branching of the assembly. If the fibre optic installation is to be installed on an existing platform, then possible routing paths may be restricted (due to existing infrastructure and equipment). However if the platform is a new build, then there may be more freedom to design the routing path. It is noted that fibre optic design software has been developed to assist in the layout of fibre optic harnessing. This can be used to model different paths and also calculate insertion loss of the link, depending on the path route. A small number of commercial packages are believed to be available. These can also predict losses associated with installation bends of the optical fibre and connector misalignment. It is further noted that modern fibre optical cable designs are utilising bend tolerant optical fibres and a number of aerospace designs are in existence. These exhibit lower losses when bent to a small radius. Whilst this could allow tighter installation bends to be designed, it needs to be emphasised that the strength of the optical fibre still needs to be respected. Generally tighter bends will increase the strain on the fibre and may reduce lifetime (particularly if there are any defects in the glass). It is therefore generally advisable to ensure typical minimum bend radius limits for aerospace optical fibre cables according to the product standard. 3.2.2 Interconnects Fibre optic connectors (interconnects) will be required to connect the fibre optic harness to end equipment or to other harness sections on the airframe. It is noted that harnesses may require multi-way connectors (with multiple optical contacts or termini) or single-way connectors depending on the specific design of the harness. This will in turn affect the management of the optical cable leading to that connector and any back shell design. Careful attention should be made to the number and placement of interconnects in the fibre optic links. The final choice and location of the interconnect needs to take into account the required performance, reliability and maintenance elements of the system. These aspects often conflict with each other in system design and so some trade-off should be performed at the design stage. Of primary importance is that the fibre optic interconnects and components do not introduce a loss that exceeds the power budget of the system. Provided that sufficient power budget is available, the use of appropriately positioned production breaks can improve the maintainability of the system. For example, in areas of high maintenance activity where there is an increased likelihood of damage, the use of additional interconnects with short fibre optic links will facilitate a quick and simple replacement of a damaged link.
In turn this capability has to be traded against the possibility that the additional interconnects may increase the insertion loss of the links reducing the reliability of the system. Experience has shown that failures at or near to the interconnect are not an uncommon failure mode, particularly where loads placed on the links are easily transferred to the interconnect assembly and associated accessories. Careful placement of the interconnect and the correct use of appropriate harness tie-down mechanisms will reduce the likelihood of this type of failure. SIST EN 4533-003:2018
EN 4533-003:2017 (E) 8 Some systems (particularly single-mode systems with laser sources) may also be sensitive to reflections propagating back to the source. Additional connectors added to improve maintainability may significantly increase the total amount of reflection depending on the connector design. Where sensitivity to back reflection exists, low reflection connectors such as UPC or APC types may need to be considered in the design. In summary the introduction of additional interconnects should be considered if the attendant increase in insertion loss and back reflection can be accommodated by the system, and the additional interconnects improve maintainability without causing impact on the reliability of the system. It is noted that connectors and tight bends will generally introduce the largest losses into an optical fibre harness. The material attenuation of the glass fibre will be small over the relatively short harness lengths of an aircraft. In addition to the losses of the cable and connectors in the system it is generally advisable to allow a 3 dB margin in the harness insertion loss to allow for lifetime ageing of the installation. This should also be factored into any system design calculations. 3.2.3 Maintainability strategy The design of harness / routing is completely linked with the maintainability strategy. In phase with this strategy the harness / routing design shall take into account the constraints depending the choice between: The use of splice as repair solution, The use of dormant / spare fibres, The replacement as unique repair solution. 3.2.3.1 Splice Splices present many benefits such as no limitation regarding mechanical and environmental properties when they are properly protected, very low impact on the optical link budget (the losses introduced by the repair have to be taken into consideration, according to the repair type, e.g. mechanical vs. protected fusion splice), and it can be considered as a permanent repair in certain cases. The main drawback is that it is necessary to access to the fibre optic cable under repair. 3.2.3.2 Dormant/spare fibre Dormant/spare fibre can be utilised in a fibre optic application installation without excessively diminishing the weight savings attained by using fibre optic cable links. However, the introduction of additional cables links will inevitably increase initial cost and system complexity, together with the additional problems of cable fibre optic link connector end/ferrule protection and stowage. In addition, any spare or redundant fibres links would be subject to the same or similar environmental conditions as the 'live' fibre link it is duplicating. SIST EN 4533-003:2018
EN 4533-003:2017 (E) 9 Deciding on the level of redundancy and depth required, should be based on a number of factors, these include: Careful consideration would have to be taken into account during the design phase to ascertain the depth of spare/dormant fibres required against weight and space envelope restrictions and limitations. The introduction of spares into any system would almost certainly have a knock on effect on cost. In the case of single w
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