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1、ANSI/AIAAANSI/AIAA S S- -102.2.5102.2.5- -20092009 American National StandardAmerican National Standard Performance-Based Sneak Circuit Analysis (SCA) Requirements Sponsored bySponsored by American Institute of Aeronautics and Astronautics Approved 17 November 2008Approved 17 November 2008 American
2、National Standards Institute Abstract Abstract This standard provides the basis for developing the analysis of sneak conditions. The sneak conditions may consist of hardware, software, operator actions, or combinations of these elements. The requirements for contractors, planning and reporting needs
3、, and analytical tools are established. The linkage of this standard to the other standards in the new family of performance-based reliability and maintainability standards is described, and all of the keywords for use in automating the SCA process are provided. Copyright American Institute of Aeron
4、autics and Astronautics Provided by IHS under license with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 ii Library of Congress cataloging-in-publication data on file Publi
5、shed by American Institute of Aeronautics and AstronauticsAmerican Institute of Aeronautics and Astronautics 1801 Alexander Bell Drive, Reston, VA 201911801 Alexander Bell Drive, Reston, VA 20191 Copyright 2009 American Institute of Aeronautics and Astronautics All rights reserved No part of this pu
6、blication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America Copyright American Institute of Aeronautics and Astronautics Provided by IHS under license with AIAA Licensee=HP Monitor
7、ing/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 iii ContentsContents Foreword v 1 Scope. 1 1.1 Purpose . 1 1.2 Application . 2 2 Applicable Documents . 2 2.1 Normative References . 2 2.2 Relationshi
8、p To Other S-102 Standards 3 3 Vocabulary . 4 3.1 Acronyms and Abbreviated Terms . 4 3.2 Terms and Definitions 4 4 General Requirements . 7 4.1 Contractor Responsibility . 7 4.2 Planning . 7 4.3 SCA Report 8 5 Detailed Requirements 8 5.1 Establish SCA Requirements and Define Analytical Ground Rules
9、. 8 5.2 Establish SCA Technical Performance Metrics 9 5.3 Collect System Design Data 9 5.4 Perform the Analysis 9 5.5 Sneak Condition Disposition 17 5.6 SCA Database . 18 5.7 Data Exchange Between SCA Process And Other Project Functions . 19 5.8 SCA Process Performance Evaluation 19 5.9 Lessons Lear
10、ned . 21 5.10 Structured Review . 21 Annex A AIAA S-102 Document Tree (normative) . 24 Annex B AIAA S-102 SCA Capability Level Requirements (normative) . 25 Annex C AIAA S-102 SCA Keyword Data Element Descriptions (normative) 28 FiFiguresgures Figure 1 S-102 Standardized Set of Functional Operators
11、12 Figure 2 Five Basic Sneak Circuit Analysis Topographs . 13 Figure 3 Sneak Condition Dataset Evaluation . 22 Figure 4 Sneak Condition Disposition Evaluation 23 TablesTables Table 1 Sample Sneak Circuit Analysis Topological Clue List . 14 Copyright American Institute of Aeronautics and Astronautics
12、 Provided by IHS under license with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 iv Table 2 AIAA S-102 Failure Severity Classification Criteria 16 Table 3 Sneak Condition
13、Dataset Maturity Rating Criteria 20 Table 4 Sneak Condition Disposition Maturity Rating Criteria . 20 Copyright American Institute of Aeronautics and Astronautics Provided by IHS under license with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or netwo
14、rking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 v ForewordForeword A performance-based Sneak Circuit Analysis (SCA) standard has been developed to aid organizations in assuring that their SCA tasking presents a “value-added” contribution to the product-development effort. The
15、 need for such a standard arises from the absence of an accepted methodology for assessing the capability of reliability and maintainability (R plan the activities necessary to achieve a level of R appraise the performance of an R and identify the activities necessary to improve the performance of a
16、n R sneak timing - Events occurring in an unexpected or conflicting sequence; sneak indications - Ambiguous or false displays of system operating conditions that may cause the system or operator to take an undesired action1 sneak labels - Incorrect or imprecise labeling of system functions (e.g., sy
17、stem inputs, controls, displays, and buses) that may cause an operator to apply an incorrect stimulus to the system. ; The SCA process assures that the likelihood of unwanted functions or inhibition of desired functions is minimized for all designed-for operating modes. In this context, an unwanted
18、function is a system response that violates a design requirement, and designed-for operating modes include all known states of system success. The analysis of sneak conditions can be considered static in nature because it does not involve stepping through all the possible combinations of inputs and
19、system states. Instead, the analysis applies a rule 1 An example of a potential sneak indication is when two identical failure indications (i.e., fault signatures) can be generated by different system functions. Copyright American Institute of Aeronautics and Astronautics Provided by IHS under licen
20、se with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 2 base (i.e., sneak clues) to topological or functional models of the system to uncover potential sneak conditions. Th
21、e models contain all possible connectivity paths; e.g., electrical current flow and data/signal flow. Because of its static nature, SCA is a good complement for simulation and testing, which are more dynamic in nature, but may be prone to overlook latent problems that occur only during unexpected op
22、erating modes. 1.21.2 ApplicationApplication This standard applies to acquisitions for the design, development, fabrication, test, and operation of commercial, civil, and military systems, equipment, and associated computer programs. This standard provides criteria for rating the capability of an ac
23、quisition projects SCA practices and assigning the practice to one of five predetermined levels of performance capability. The capability criteria provide the logical sequence of activities for improving the effectiveness of an existing SCA practice by advancing in stages. Organizations may evaluate
24、 their existing SCA practices against these minimum acceptable criteria to identify the features that need to be added to improve their existing SCA practices. This standard also applies to the integration of the SCA database with a project R (2) Hardware Reliability any undesired state of a compone
25、nt or system; (3) Components a defect or flaw in a hardware or software component, NOTE: (1) An accident may cause a fault. NOTE (2) A fault may cause a failure. NOTE (3) A fault does not necessarily require failure. maturity levelmaturity level measure of the degree of accuracy of a data product, a
26、s developed using a specified set of input data, in relation to what is considered the best achievable results mission assurance mission assurance project-wide identification, evaluation, and mitigation or control of all existing and potential deficiencies that pose a threat to mission success, thro
27、ughout the product life cycle NOTE Deficiencies include damage-threatening hazards, mission-impacting failures, and system performance anomalies that result from unverified requirements, optimistic assumptions, unplanned activities, ambiguous procedures, undesired environmental conditions, latent ph
28、ysical faults, inappropriate corrective actions, and operator errors. network forest network forest a higher-order network diagram depicting the interrelationships among the numerous network trees network treenetwork tree a functional, topologically oriented circuit segment that is analyzed for the
29、existence of sneak circuits and conditions. NOTE Numerous network trees are generated to describe the system under analysis. p partitioningartitioning subdivision of functions at the circuit or device level into separate, cross-referenced functions, to aid in the data reduction / pathfinding process
30、, as well as to facilitate the generation of topological network trees performanceperformance- -based R b) the SCA requirements as needed to support the project, including milestones for developing fault trees, or modifying existing fault trees; c) scope and ground rules of the SCA; 4 Failure compen
31、sation methods may include special design features, analyses, inspections, tests, controls, instructions, or operational corrective actions, such as replacement, reconfiguration, repair, or preventive maintenance. Copyright American Institute of Aeronautics and Astronautics Provided by IHS under lic
32、ense with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 8 d) detailed procedures for selecting the set of sneak conditions of concern; e) detailed procedures for establishi
33、ng the system level at which sneak conditions are identified; f) detailed procedures for constructing functional flow or network tree models, and samples thereof; g) detailed SCA process descriptions and flow diagrams that include the approach for applying sneak clues to identify sneak conditions; h
34、) detailed procedures for documenting and reporting the SCA data/results in a timely manner; and i) definitions of SCA data attributes; i.e., data characteristics and formats that accommodate the needs of other project functions, including those of reliability, maintainability, system safety, and ri
35、sk management. The SCA process shall be planned to support timely and cost-effective implementation of the R b) identifying the design data sources; Copyright American Institute of Aeronautics and Astronautics Provided by IHS under license with AIAA Licensee=HP Monitoring/1111111164 Not for Resale,
36、04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 9 c) selecting the types of sneak conditions to be identified and the analysis methods7 5.25.2 EstablishEstablish SCA Technical Performance MetricsSCA Technical Performance Metrics
37、to be used; d) describing how consistency will be achieved among independently performed SCA; e) defining the procedures and nomenclature by which sneak conditions will be documented; and f) describing the extent that sneak conditions due to external system interfaces and influences (e.g., human err
38、ors, operating environments, etc.) will be identified. The out-of-scope areas that require only interface analysis also shall be identified. Care shall be taken to ensure that the SCA effort is limited to those high-criticality areas where sneak conditions are considered most likely to occur. The co
39、ntractor shall establish SCA Technical Performance Metrics for purposes of tracking and reporting the progress of the SCA activities. 5.35.3 CollectCollect System Design Data System Design Data Prior to beginning the evaluation of possible undesired sneak conditions, the contractor shall collect suf
40、ficient system design information to identify all functional and physical dependencies in the system that fall within analytical ground rules to be specified by the contractor (see Reference 5). The system design information shall include the following: Schematics Indentured parts lists Wire lists a
41、nd interconnects Design specifications Descriptions of the mission phases, mission environments, and all normal, degraded, and contingency system modes that are applicable to each mission phase The statement of work If a Capability Level 3 or higher SCA is required, this information shall be entered
42、 in the SCA/FMECA database to allow cross-referencing of identified sneak conditions against official design drawings. 5.45.4 Perform the AnalysisPerform the Analysis Following the collection of system design information, the contractor shall perform a structured analysis approach that achieves the
43、following objectives: a) development of partitioned system models that are based on functional interrelationships (i.e., functional diagrams) or energy flow (i.e., network trees); b) identification of sneak conditions; c) evaluation of sneak condition severity; d) identification of sneak condition d
44、etection methods; e) if a Capability Level 4 or higher SCA is required, estimation of sneak condition probability of occurrence; and f) documentation of identified sneak conditions; 7 This is a process validation activity when it includes evaluation of the appropriateness of the SCA process prior to
45、 its use. Copyright American Institute of Aeronautics and Astronautics Provided by IHS under license with AIAA Licensee=HP Monitoring/1111111164 Not for Resale, 04/07/2009 05:37:36 MDTNo reproduction or networking permitted without license from IHS -,-,- ANSI/AIAA S-102.2.5-2009 10 5.4.15.4.1 Develo
46、pment of Partitioned System Models that are Based on Functional InterrelationshipDevelopment of Partitioned System Models that are Based on Functional Interrelationships s or Energy Flow or Energy Flow The contractor shall develop partitioned system models that are based on functional interrelations
47、hips or energy flow. The models shall be developed to a level of detail that allows a comprehensive analysis of possible sneak conditions. The models shall provide an accurate representation of the operating modes and time-based interrelationships of the systems functions. The contractor shall devel
48、op these models by partitioning the system-level or subsystem-level design into smaller, functionally related segments that permit efficient and effective application of the sneak clue list. Factors to be considered in the partitioning effort shall include, but are not limited to, mission time intervals, functional or energy inputs, functional or energy outputs, flow paths, switching functions, event sequences, modes and transitions, and feedback paths and controls Items t