EN 14514:2004

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Standardi v vesoljski tehniki – Analiza funkcij sistemaRaumfahrttechnik Normen - FunktionenanalyseNormes d'ingénierie spatiale - Analyse fonctionnelleSpace engineering standards - Functional analysis49.140Vesoljski sistemi in operacijeSpace systems and operationsICS:Ta slovenski standard je istoveten z:EN 14514:2004SIST EN 14514:2005en01-januar-2005SIST EN 14514:2005SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14514August 2004ICS 49.140English versionSpace engineering standards - Functional analysisNormes d'ingénierie spatiale - Analyse fonctionnelleRaumfahrttechnik Normen - FunktionenanalyseThis European Standard was approved by CEN on 21 February 2003.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, 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© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14514:2004: ESIST EN 14514:2005

EN-14514:2004 (E) 3 List of figures Figure 1 — Functional analysis implementation overview.9 Figure 2 — Function tree.12 Figure 3 — Function tree.13 Figure 4 — Functional matrix.14 Figure 5 — Functional block diagram.16 SIST EN 14514:2005

Foreword This document (EN 14514:2004) has been prepared by CMC. 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 February 2005, and conflicting national standards shall be withdrawn at the latest by February 2005. It is based on a previous version1) prepared by the ECSS Engineering Standard Working Group, reviewed by the ECSS Technical Panel and approved by the ECSS Steering Board. The European Cooperation for Space Standardization (ECSS) is a cooperative effort of the European Space Agency, National Space Agencies and European industry associations for the purpose of developing and maintaining common standards. This document is one of the series of ECSS Standards intended to be applied together for the management, engineering and product assurance in space projects and applications.
Requirements in this document are defined in terms of what shall be accomplished, rather than in terms of how to organize and perform the necessary work. This allows existing organizational structures and methods to be applied where they are effective, and for the structures and methods to evolve as necessary without rewriting the standards. The formulation of this document takes into account the existing ISO 9000 family of documents. 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, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
1) ECSS-E-10-05A SIST EN 14514:2005

EN-14514:2004 (E) 5 1 Scope This document defines the requirements to perform functional analysis and the information output of that analysis. It applies to all types and combinations of space systems, projects and products. It also applies to project phases 0, A, B and C and at all levels. When viewed from the perspective of a specific project context, the requirements defined in this document should be tailored to match the genuine requirements of a particular profile and circumstances of a project. NOTE
Tailoring is a process by which individual requirements of specifications, standards and related documents are evaluated and made applicable to a specific project by selection, and in some exceptional cases, modification of existing or addition of new requirements. 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 13701:2001, Space systems – Glossary of terms EN 13290-4, Space project management – General requirements – Part 4: Project phasing and planning 3 Terms, definitions and abbreviated terms 3.1 Terms and definitions For the purposes of this document, the terms and definitions given in EN 13701:2001 and following apply. 3.1.1 constraint characteristic, result or design feature which is made compulsory or has been prohibited for any reason NOTE 1 Constraints are generally restrictions on the choice of solutions in a system. NOTE 2 Two kinds of constraints are considered, those which concern solutions, and those which concern the use of the system. NOTE 3 For example constraints can come from environmental and operational conditions, law, standards, market demand, investments and means availability, organization’s policy. NOTE 4 Adapted from EN 1325-1. 3.1.2 function intended effect of a system, subsystem, product or part NOTE 1 Adapted from EN 1325-1. NOTE 2 Functions should have a single definite purpose. Function names should have a declarative structure (e.g. “Validate Telecommands”), and say “what” is to be done rather than “how”. Good naming allows design components with strong cohesion to be easily derived. 3.1.3
functional analysis technique of identifying and describing all functions of a system NOTE Adapted from EN 1325-1. SIST EN 14514:2005

operational mode manner or way of operating NOTE The mode is realized by a group of related functions or tasks required to accomplish a specific operation. 3.1.5 operational scenario summary of sequences of events and the environment for a specific operation 3.1.6 functional specification document by which the customer establishes the intended purpose of a product, its associated constraints and environment, the operational and performances features, and the permissible flexibility NOTE 1 This document contains a complete set of provisional technical requirements for a product. NOTE 2 This term is equivalent to functional performance specification as defined in EN 1325-1. 3.1.7 technical specification specification expressing technical requirements for designing and developing the solution to be implemented NOTE
The technical specification evolves from the functional specification and defines the technical requirements for the selected solution as part of a business agreement
3.2 Abbreviated terms The following abbreviated terms are defined and used within this document. Abbreviation Meaning FMECA failure modes effects and criticality analysis ROD review of design RAMS reliability, availability, maintainability and safety 4 Principles and methods of functional analysis 4.1 Principles In order to design, develop and prove any space engineering system, the mission and consequent functions, that the system shall perform, is clearly established. This functionality is distributed throughout the different design levels (e.g. systems, subsystems and units). This allocation of the system functions in a systematic way is an important step in establishing a design which meets all the design objectives. 4.2 Methods Functional analysis is the technique of identifying and describing all the functions of a system. The purpose of the analysis is to identify and partition all the functions of any system required to perform the intended mission.
The analysis is performed to establish the system functions and to control the distribution and maintenance of these functions in a systematic and useful manner. Three techniques: function tree, functional matrix and functional block diagram are described, although it is recognized that other representations can also prove suitable. SIST EN 14514:2005

EN-14514:2004 (E) 7 At the top system level, the required functions are derived from the mission statement and are the basis of the system functional specifications. All these functions can be considered ”external” functions.
The solution to meet these functions can lead to new lower level functions to be identified which are a result of the chosen solution. These new functions are either serviced at the system level where they were derived, in which case the function is satisfied, or passed to a lower level. A function, which is passed to a lower level, is a higher level function for the recipient level.
As the detail of the design progresses, each tier of the design add additional functions necessary to support the higher level functions. Both types of functions can be either solved internally within the system or refined into requirements and functions to be met at some lower level engineering unit. Thus, some functions have different levels of importance associated with them depending on how and where they originated. Some functions are readily achievable, while others are complex and expensive to meet. Often at the lower levels, solutions are available which readily meet most of the functions or during development it is established that a particular function is only met under specific conditions. The knowledge of the origins of any function allows to establish the consequences and impact of not meeting a requirement or to allow a function to be renegotiated.
Changes to requirements can arise at top system level, in which case the ”sub”-derived functions, which are affected at the lower tier level, are readily identifiable. A realistic example of top system level changes occurs when the launch vehicle is changed and as a consequence, the vibration spectrum or human factors can alter. Functional analysis includes different activities. The complexity of the analyses adapts considering the design maturity, the evolution of the design and the complexity of the mission. The ultimate aim is to achieve the simplest final design which meets all the system requirements and offers the best value by achieving that all the functions are met and also partitioned in a logical manner.
Functional analysis is performed in a systematic manner. Function are not passed from one system to another system of the same level, but are received from a higher level system and either serviced or further distributed (and divided if necessary) to lower level systems.
Functional analysis excludes the assessment of the criticality of the functions in terms of reliability and safety, but can serve as the basis of the functional failure analysis. Functional analysis also excludes any consideration of the engineering solution required to service an identified function, until ”internal” functions are identified as part of the required solution. By considering a system in terms of functions (being the problem to solve) and not in terms of technology (a possible solution), alternative technologies are not excluded, duplication can be avoided and components standardization can be improved.
4.3 Objectives The objectives of functional analysis are to: a) identify or update the functional requirements; b) ensure the functions are partitioned in an appropriate manner; c) allow the traceability of the functions; d) identify the interfaces between functions. This allows a complex engineering system to be understood and realized.
4.4 Logic and implementation overview 4.4.1 Performance Functional analysis is performed as part of the overall design development process.
4.4.2 Implementation The following functional analysis steps are implemented to: SIST EN 14514:2005

EN-14514:2004 (E) 9
Figure 1 — Functional analysis implementation overview SIST EN 14514:2005

A system shall be designed to conform to a given objective, i.e. satisfy the requirement of the users by performing a specified set of functions. It can be affected by the environment, acted upon by external systems or act itself upon the environment or external system. The users and the environment are outside the system. 1) The boundaries of a system or a product shall be defined by its relationship with the different external elements. External elements shall be users, the environment and the external systems. The system engineering process shall begin with the identification of the requirement, which is linked to a given user in a given situation and is conditioned by place, time and environment (e.g. humidity and ice). The given situation, the place, the environment and interfaces with external systems generate constraints.
2) The requirements and the constraints shall be described in terms of functions, not in terms of solutions. During its life cycle a system or a product is placed in different situations and environments, which in turn generate constraints. Situations and environments may be characterized as nominal, worst case or contingency as relevant. 3) The different constraints generated by the different encountered conditions of a system shall be taken into account. 4) The functions and the constraints shall be completed by performance criteria. 5.1.2 Definition of the level of detail The level of detail in performing functional analysis is determined by design maturity and normally increases during the project life cycle. To avoid a non-productive level of detail, the analyst shall have a clear understanding of the analysis objectives applicable to the specific project phase for which the design is considered current. 1) The level of detail of functional analysis shall be described and documented.
2) The level of detail shall be in accordance with the contractual requirements and with the design maturity. 5.1.3 Identification of functions A function may be decomposed into lower level functions. This division of the functions of a system, which shall start from the functional specification, is an essential part of functional analysis, and results in a hierarchical structure of functions. Functional analysis shall: 1) provide the identification of the functions of the system; 2) identify the functions required to be performed in the different operational scenarios of the analysed mission; 3) identify the functions required by the different operational modes of the system. Operational modes include contingency modes induced by failures, faults or operator errors; SIST EN 14514:2005

EN-14514:2004 (E) 11 4) provide a hierarchical decomposition of the functions of the system.
A hierarchical structure of the functions of a system pro
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