SIST EN 4533-003:2009
(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
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 harness installation is designed for reliability and maintainability. This concept holds true for both copper based and fibre optic harnesses.
The objective of this part of EN 4533 is to provide technical advice and assistance to designers and engineers on the incorporation of fibre optic harnesses into an airframe, while maintaining maximum compliance with current aircraft electrical harness procedures. This part considers the looming and installation aspects during initial design, throughout the manufacture and installation of the fibre optic harness and how the practices chosen affect through life support of the harness.
Luft- und Raumfahrt - Faseroptische Systemtechnik - Handbuch - Teil 003: Verfahren zur Fertigung und Installation von Leitungsbündeln
Fertigungs- und Installationsverfahren für Leitungsbündel sind ein kritischer Aspekt in jeder elektrischen/für die Luft- und Raum¬fahrt vorgesehenen Installation in Luftfahrzeugen. Für die Bereitstellung eines zuverläs¬si¬gen und effizienten Systems ist es wichtig, dass die Kabelbauminstallation für Zuverlässigkeit und Wartungs¬fähigkeit ausgelegt ist. Dieses Konzept gilt sowohl für Kupfer- als auch für LWL-Kabelbäume.
Zweck dieses Teils von EN 4533 ist die Bereitstellung technischer Empfehlungen und Unterstützung für Konstruk¬teure und Ingenieure für den Einbau von LWL-Kabelbäumen in ein Luftfahrzeug und gleichzeitiger Über¬einstimmung mit den derzeitigen verfahren für elektrische Kabelbäume in Luftfahrzeugen. Dieser Teil behandelt die Aspekte der Fertigung und Installation von Leitungsbündeln während der ersten Konstruktions¬phase, der gesamten Herstellung und der Installation von LWL-Kabelbäumen sowie den Einfluss der ausge¬wählten Verfahren auf die auf die Unterstützung des Kabelbaums während dessen gesamter Lebensdauer.
Série aérospatiale - Systèmes des fibres optiques - Manuel d'utilisation - Partie 003 : Règles de l'art pour la fabrication et l'installation des harnais
Aeronavtika - Sistemi iz optičnih vlaken - Priročnik - 003. del: Postopki za izdelavo in namestitev vezalnega pasovja
General Information
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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: Verfahren 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 systemsICS:Ta slovenski standard je istoveten z:EN 4533-003:2006SIST EN 4533-003:2009en,de01-junij-2009SIST EN 4533-003:2009SLOVENSKI
STANDARD
SIST EN 4533-003:2009
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 4533-003July 2006ICS 49.060 English VersionAerospace series - Fibre optic systems - Handbook - Part 003:Looming and installation practicesSérie aérospatiale - Systèmes des fibres optiques - Manueld'utilisation - Partie 003 : Règles de l'art pour la fabricationet l'installation des harnaisLuft- und Raumfahrt - Faseroptische Systemtechnik -Handbuch - Teil 003: Praktiken zur Fertigung undInstallation von LeitungsbündelnThis European Standard was approved by CEN on 28 April 2006.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 4533-003:2006: ESIST EN 4533-003:2009
EN 4533-003:2006 (E) 2 Contents Page 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.6 3.2.1 Connectorisation and available power budget.6 3.2.2 The use of redundancy.7 3.2.3 Spare cabling.7 3.2.4 Dormant fibres.7 3.3 Harness routing considerations.8 3.3.1 General.8 3.3.2 Drip loops.8 3.3.3 Circular paths.9 3.4 Securing and attachment mechanisms.9 3.5 Protection mechanisms.11 3.5.1 General.11 3.5.2 Conduit.11 3.6 Installation mechanisms.13 3.7 Through life support.13 4 Manufacturing issues.15 4.1 General.15 4.2 Handling.15 4.2.1 General.15 4.2.2 Minimum bend radii.15 4.2.3 Forming the loom.16 4.3 Cable identification methods.16 4.3.1 Identifications.16 4.3.2 Heatshrink identification sleeves.16 4.4 Installation of fibres in conduit.17 4.4.1 General.17 4.4.2 Connectors and conduit.17 5 Looming and installation on aircraft.17 5.1 Termination, protection of the end-face.17 5.1.1 General.17 5.1.2 Free connectors.18 5.1.3 Fixed connectors.18 5.2 Pulling of fibre optic cables/harnesses through conduits during installation.19 5.3 Routing of fibre optic cables through pressure bulkheads.19 5.4 Electrical/optical.19 5.5 Additional considerations.19 5.5.1 Cable marking.19 5.5.2 Cable storage.20
SIST EN 4533-003:2009
EN 4533-003:2006 (E) 3 Foreword This European Standard (EN 4533-003:2006) has been prepared by the European Association of Aerospace Manufacturers - Standardization (AECMA-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 AECMA, 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 January 2007, and conflicting national standards shall be withdrawn at the latest by January 2007. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 4 Introduction a) The handbook The handbook draws on the work of the Fibre-Optic Harness Study, part sponsored by the United Kingdom’s Department of Trade and Industry, plus other relevant sources. It aims to provide general guidance for experts and non-experts alike in the area of designing, installing, and supporting multi-mode 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 and inspection b) Background It is widely accepted in the aerospace industry that photonic technology offers a number of 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). To date, the latter 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 in sensing many of the physical phenomena on-board aircraft. 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, vibrations, 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.
c) The fibre-optic harness study The Fibre-Optic Harness Study concentrated on developing techniques, guidelines, and standards associated with the through-life support of current generation fibre-optic harnesses applied in civil and military airframes (fixed and rotary wing). Some aspects of optical system design were also investigated. This programme has been largely successful. Guidelines and standards based primarily on harness study work are beginning to emerge through a number of standards bodies. Because of the aspects covered in the handbook, European prime contractors are in a much better position to utilise and support available fibre optic technology. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 5 1 Scope 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 harness installation is designed for reliability and maintainability. This concept holds true for both copper based and fibre optic harnesses.
The objective of this part of EN 4533 is to provide technical advice and assistance to designers and engineers on the incorporation of fibre optic harnesses into an airframe, while maintaining maximum compliance with current aircraft electrical harness procedures. This part considers the looming and installation aspects during initial design, throughout the manufacture and installation of the fibre optic harness and how the practices chosen affect through life support of the harness. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 4533-001, Aerospace series — Fibre optic systems — Handbook — Part 001: Termination methods and tools. 3 Initial design considerations 3.1 General The installation of fibre optic harnesses 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; 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. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 6 Copper installations are prone to electrical interference and their use is restricted in “volatile” zones. Fibre optic cables are virtually 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: c) Areas where there are high levels of electrical, field strength; d) Areas where electric fields need to be kept to a minimum, e.g. compass deviation; e) Routing through and close to fuel tanks; f) 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: g) System criticality; h) Harness accessibility, improves on-aircraft repair and maintenance, but should not degrade system protection; i) System segregation and redundancy, maximisation of damage limitation; j) Accessibility of connectors; k) System and component repair and maintenance issues; l) 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 Connectorisation and available power budget Careful attention should be made to the number and placement of connectors in the optical harness. The final choice and location of connectors needs to consider the required performance, reliability and maintenance aspects 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 harness 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 connector 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 connector breaks will facilitate a quick and simple replacement of damaged cable. This in turn has to be traded off against the possibility that the additional connectors may themselves fail, reducing the reliability of the system. Experience has shown that failures at or near to the connector are not an uncommon failure mode, particularly where loads placed on the harness are easily transferred to the connector backshell. Careful placement of the connector and the use of appropriate harness tie-down mechanisms will reduce the likelihood of this type of failure. In summary the introduction of additional connectors should be considered if the loss increase induced by the introduction is within the power budget of the system, and the additional connectors improve maintainability without causing impact on the reliability of the system.
SIST EN 4533-003:2009
EN 4533-003:2006 (E) 7 3.2.2 The use of redundancy Redundancy can be utilised in a fibre optic application without excessively diminishing the weight savings attained by using fibre optic cable. However, the introduction of additional cables will inevitably increase initial cost and system complexity, together with the additional problems of cable end/ferrule protection and stowage. In addition, any spare or redundant fibres would be subject to the same or similar environmental conditions as the 'live' fibre it is duplicating. Clearly, the more in-built redundancy the increased survivability of the system. Deciding on the level of redundancy and depth required, should be based on a number of factors, these include: Criticality
How important is the system to the operation of the aircraft? This may mandate that 2 (duplex) or 3 (triplex) levels of system redundancy are required for highly critical systems such as flight controls. In this case all paths are fully connected as part of the system to allow the system to function even if a failure occurred. Complexity/Maintainability
The introduction of additional 'spare' fibre would inevitably increase the complexity of system design, which in turn would directly affect the weight and space envelope factors, cost, and to a lesser degree, the maintainability of the system.
Weight and space envelope
Careful consideration would have to be taken into account during the design phase to ascertain the depth of redundancy required against weight and space envelope restrictions and limitations. Repair
Repair of systems can be improved with the incorporation of redundancy and/or dormant fibre, depending on the system damage sustained. The ability to transpose damaged fibres with 'spare' fibres, negating the need to remove and replace harnesses may prove beneficial, however, the question raised is 'how many spare fibres do you include in each harness?
The time taken to replace the damaged fibre should also be recognised as an important issue, especially in a commercial application where aircraft down time needs to be kept to a minimum. Therefore it may be easier, and quicker to remove a complete harness assembly (complete with connectors) and replace with a pre-assembled unit. 3.2.3 Spare cabling Inclusion of additional spare/redundant fibres is probably the easiest method to improve the survivability or maintainability of any airborne fibre optic installation. It provides a system capability that will allow continued operation even if damage has been sustained, or a failure to an element of that system has occurred.
Current copper systems do not incorporate dedicated spare cables or dedicated lines of redundancy. However, they include elements of back up in their design [secondary systems, Line Replacement Items (LRI), etc]. 3.2.4 Dormant fibres Redundancy also encompasses ‘dormant’ fibre in harnesses. The use of dormant fibres would allow replacement of damaged fibres within a harness without the need for removal of the harness or introduction of new fibre into the harness. However, including dormant fibres within a harness would also introduce a number of technical problems, including: Un-terminated fibre would require end protection to prevent contamination (including fluid wicking). Un-terminated fibre would require termination 'on-aircraft' when required for use. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 8 Pre-terminated single way connector ferrules require safe stowage to prevent damage/contamination of the end face. Pre-terminated ferrules of multi-way connectors, stored in spare receptacles require the dismantling of connectors at each end of the affected harness, removal from the connectors of the faulty and spare fibre contacts and transposition of the contacts to their relevant receptacles and re-assembly of the connectors. Possible weight penalties depending on number of fibres/contacts/connectors required. Damage to a harness could extend into the dormant fibre rendering it unusable. A reduction in the number of listed problems could be achieved, such as routing spare fibre external to, and away from the original harness, weight penalties may be minimal due to the overall weight savings of fibre optic installations over copper installations.
Further constraints including the limitation of operational maintenance facilities, length of repair time and limitations of available tooling may make the use of dormant fibres untenable. Therefore the advantages/disadvantages for the introduction of dormant fibres in a system needs to be carefully considered during the design phase. 3.3 Harness routing considerations 3.3.1 General Studies within the Harness Study have shown avionic fibre cables to be very tolerant of conventional electrical looming and installation methods and indeed, routing fibre optic harnesses along/within existing copper looms/harnesses is, in many cases, advantageous. The hybrid harness will provide additional mechanical support and strain relief, without the need for specialized, additional clamping or routing requirements. In general terms it is considered that sufficiently ruggedised ‘avionic’ cables can be routed using exactly the same design criteria as electrical cables. 3.3.2 Drip loops Drip loops are incorporated where there is a probability that fluids will affect a harness or system component. The harness or cable should be routed in such a manner that the fluid cannot migrate along the harness or cable into the rear of the connector (see Figure 1).
Figure 1 — Typical types of drip loop When installing fibre optic harnesses careful consideration needs to be taken into account when introducing drip loops. The fibre should not exceed the long term minimum bend radius, therefore, if routing along existing copper looms with a smaller minimum long-term bend radius it may be necessary to adjust the copper installation to allow for the fibre bend radius, or route the fibre harness separate to the copper loom and introduce another drip loop. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 9 3.3.3 Circular paths With the introduction of system segregation and separate routing the problem arises of multiple fibre optic cables routed from varying locations terminating into a single-point multi-way connector. During the design stage it is important that the routing of fibre optic harnesses takes into account the accessibility of routing terminated/connectorised fibres through the airframe structure, to prevent the requirement for end termination in the airframe. 3.4 Securing and attachment mechanisms As with any harness installation, methods of cable support and retention are important factors in order to guide and retain the harness, while at the same time limiting the effects of stress on the cables. The use of dedicated, special-to-type fibre optic harness routing and clamping methods maintain controlled conditions on the fibres. However these methods encroach on the airframe space envelope while increasing weight and cost. Providing the performance of the fibre optic cable is not compromised, it is recommended that cables be routed in the same way as existing electrical cables. Work was performed as part of the Fibre Optic Harness Study into how conventional methods of attaching and retaining electrical cable harnesses may affect the performance of the cable and ultimately the transmission of light. It was felt that if current electrical support and retention techniques could be applied this would make the introduction of the technology much more acceptable to the installer by reducing training and installation costs. Many of the results highlighted that far from being a special case, the fibre-optic cable types tested exhibited a performance that allowed existing retention and support methods to be used that could not be applied to high bandwidth electrical cables, such as co-axial cables. The current methods of cable support and retention used on airborne applications harnesses include: Cable ties; Lacing cord; Raceway harpoons; ‘P’ clips; Raceway clamps; Bobbins. The effects of these retention devices on multi-fibre open harnesses and raceways and associated temperature variation effects were investigated. The results obtained indicated that the losses introduced by the retention methods on current generation avionic fibre optic cables were minimal. SIST EN 4533-003:2009
EN 4533-003:2006 (E) 10
Figure 2 — Typical far-field scan results (power (W) vs N.A) obtained after applying cable ties onto an open bundle fibre optic harness (100/140 µm graded index fibre) As shown in Figure 2, the power losses were minimal. These results being similar for all the cable types tested. To achieve minimal losses, it is important that the correct components and tooling are used, the procedure, for a number of securing mechanisms, is outlined below: Cable ties - the use of correct cable ties for the size of cable bundle and the appropriate cable tie tool (set to the required tension). The ties need to be correctly positioned to maximise the retention, and support along the length of the harness; Raceway harpoons – A similar installation procedure applies to raceway harpoons as that of cable ties, the correct cable tie tool shall be used to install the harpoon retainer (Figure 3);
Figure 3 — Harpoon tie with associated spacers and retainer SIST EN 4533-003:2009
EN 4533-003:2006 (E) 11 The use of ‘P’ clips as cable retainers present no particular problem of cable crush as long as the correct size ‘P’ clips are used and installation procedures are followed; Cables routed in raceway clamps should lie side by side and not cross under the clamp; Special to type retainers such as bobbins may be used if single fibre installations are routed separately from multi-harnesses or previously installed cable runs; Lacing cord ties can be used on these avionic cables without causing additional losses. The ties should be applied in the same way as for conventional electrical cables. 3.5 Protection mechanisms 3.5.1 General In certain areas along the route that a fibre optic cable or harness takes along the aircraft, special additional protection over and above that afforded by the rugged cable design may be required. Generally the same protection components that are used for electrical components can be used for optical or hybrid cable looms, although if only optical cables are to be routed they do not require any metallic screening for EMI purposes. Over the length of the loom one or a combination of protection devices may be required. Examples of acceptable protection mechanisms are: Conduit (Rigid and/or flexible); Sleeving;
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