ASD-STAN PREN 4533-003-2016 Aerospace series Fibre optic systems Handbook Part 003 Looming and installation practices (Edition P 2).pdf

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1、ASD-STAN STANDARD NORME ASD-STAN ASD-STAN NORM prEN 4533-003 Edition P 2 April 2016 PUBLISHED BY THE AEROSPACE AND DEFENCE INDUSTRIES ASSOCIATION OF EUROPE - STANDARDIZATION Rue Montoyer 10 - 1000 Brussels - Tel. 32 2 775 8126 - Fax. 32 2 775 8131 - www.asd-stan.org ICS: Supersedes edition P 1 of Ap

2、ril 2005 and will supersede EN 4533-003:2006 Descriptors: ENGLISH VERSION Aerospace series Fibre optic systems Handbook Part 003: Looming and installation practices Srie arospatiale Systmes des fibres optiques Manuel dutilisation Partie 003 : Rgles de lart pour la fabrication et linstallation des ha

3、rnais Luft- und Raumfahrt Faseroptische Systemtechnik Handbuch Teil 003: Praktiken zur Fertigung und Installation von Leitungsbndeln This “Aerospace Series“ Prestandard has been drawn up under the responsibility of ASD-STAN (The AeroSpace and Defence Industries Association of Europe - Standardizatio

4、n). It is published for the needs of the European Aerospace Industry. It has been technically approved by the experts of the concerned Domain following member comments. Subsequent to the publication of this Prestandard, the technical content shall not be changed to an extent that interchangeability

5、is affected, physically or functionally, without re-identification of the standard. After examination and review by users and formal agreement of ASD-STAN, it will be submitted as a draft European Standard (prEN) to CEN (European Committee for Standardization) for formal vote and transformation to f

6、ull European Standard (EN). The CEN national members have then to implement the EN at national level by giving the EN the status of a national standard and by withdrawing any national standards conflicting with the EN. Edition approved for publication 1st April 2016 Comments should be sent within si

7、x months after the date of publication to ASD-STAN Electrical Domain Copyright 2016 by ASD-STAN prEN 4533-003:2016 (E) 2 Contents Page Foreword 2 Introduction . 3 a) The Handbook 3 b) Background 3 1 Scope 4 2 Normative references 4 3 Initial design considerations 4 3.1 General 4 3.2 System design co

8、nsiderations . 5 3.2.1 Introduction 5 3.2.2 Interconnects . 6 3.2.3 Maintainability strategy . 7 3.3 Practical harness routing considerations . 8 3.4 Securing and attachment mechanisms . 8 3.5 Protection mechanisms 11 3.5.1 General 11 3.5.2 Conduit .12 3.6 Installation mechanisms .14 3.7 Through lif

9、e support 14 3.8 Enabling Fibre optic cable re-termination .14 3.9 Handling 16 Foreword This standard was reviewed by the Domain Technical Coordinator of ASD-STANs Electrical Domain. After inquiries and votes carried out in accordance with the rules of ASD-STAN defined in ASD-STANs General Process M

10、anual, this standard has received approval for Publication. prEN 4533-003:2016 (E) 3 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 m

11、ore 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,

12、 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 component

13、s 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 o

14、f the growing use of non-metallic aerostructures. However, future avionic requirements are driving bandwidth specifications from 10s 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 potenti

15、ally be exploited to advantage in many avionic applications, such as video/sensor multiplexing, flight control signalling, electronic warfare, and entertainment systems, as well as in sensing many of the physical phenomena on-board aircraft. The basic optical interconnect fabric or optical harness i

16、s 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 contami

17、nation) 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 safet

18、y 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 of

19、ten 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

20、 significant research collaboration between component and equipment manufacturers as well as the end use airframers. prEN 4533-003:2016 (E) 4 1 Scope This handbook considers best practice during initial design and how the practices chosen affect through life support of the installation. Looming and

21、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

22、 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 rule

23、s 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 u

24、ndated 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 a

25、nd 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, cleanin and inspection 3 Initial design considerations 3.1 General Wherever possible the installation of fibre

26、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 s

27、imilar 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 person

28、nel moving within the aircraft; Stowage or movement of cargo; Battery electrolytes and fumes; prEN 4533-003:2016 (E) 5 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 temperatur

29、es; 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, o

30、r 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 cl

31、ose 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 access

32、ibility, 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 le

33、ngths 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. 3.2 System design considerations 3.2.1 Introduction In the design of a fibre optic har

34、ness, 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 existin

35、g infrastructure and equipment). However if the platform is a new build, then there may be more freedom to design the routing path. prEN 4533-003:2016 (E) 6 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 di

36、fferent 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 mod

37、ern 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

38、 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

39、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

40、 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 li

41、nks. 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 impo

42、rtance 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 ar

43、eas 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 i

44、nterconnects 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 a

45、ssociated 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. Some systems (particularly single-mode systems with laser sources) may also be sensitive to reflections propagating back to

46、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

47、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 t

48、hat 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 gene

49、rally 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. prEN 4533-003:2016 (E) 7 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: