Analyse des défaillances et suivi de la validation du logiciel d'un équipement de télécommunication

International audienceL'article présente les résultats de I'analyse et de L'évaluation de la fiabilité du logiciel d'un équipement de télécommunications au cours de sa validation. Un filtrage des 2 146 relevés de défaillance collectés sur le logiciel a permis d'ecarter environ 45% des relevés; ces relevés correspondent essentiellement à des informations redondantes ou inutilisables. Une analyse statistique des releves retenus a permis d'identifier les différents types de défauts et d'étudier leur répartition par fonction et par degré de criticité. L' évaluation des mesures de fiabilité du logiciel a été précédée par une analyse de la variation de la croissance defiabilaé basée sur le test de Laplace. Enfin, L'application du modéle hyperexponentiel a permis, d'une part, de suivre Lévolution du nombre de défaillances du logiciel au cows de sa validation, et d'autre part, d'estimer le taux de défaillance du logiciel avant sa mise en service en tenant compte d'abord de toutes les défaillances toutes consequénces confondues et puis des défaillances les plus critiques uniquement

AIRCRAFT SAFETY MODEL DEVELOPMENT AND INTEGRATION IN A RISK OBSERVATORY

International audienceThe Future Sky Safety project 4 (FSS P4) aims at developing a prototype Risk Observatory (RO) that will assist in the safety assessment of the total aviation transport system. The Risk Observatory is based on the interaction between safety models covering various domains of the aviation transport system: Aircraft, Air Traffic Management, Airline Operation. In this paper we describe the development of the Aircraft domain safety model and its integration within the RO thanks to the specification and the implementation of a dedicated interface between the Aircraft Operation Safety Model described in this paper and a backbone model developed in cooperation with the other partners of the FSS project. The main inputs used to develop the aircraft safety model are the Aircraft Functional Hazard Assessment (FHA) and the Standard Operating Procedures (SOP). The FHA is used to assess the impact of the aircraft function failures on the aircraft and its occupants considering existing or assumed mitigation means and derive safety requirements for the aircraft design. In the context of FSS, the FHA is used to infer a severity level for each considered failure scenario and the ensued occurrence probability targets as per the European Aviation Safety Agency regulations. The SOP describes the main actions to be performed by the flight crew during each flight phase in order to ensure a safe flight and landing. The Aircraft safety model computes, for each operation procedure, a qualitative safety performance measure that is based on crew errors, aircraft system failures, safety performance measure of previous relevant procedures and external actor errors. Integration of the Aircraft Safety Model in the RO is performed via a Backbone model that has been developed with other domains. The Backbone model manages in a consistent way generic contributors and influencing factors like the environmental conditions, leading to a global risk such as Runway Excursion. The Aircraft Safety Model is used to verify that the preliminary aircraft system architecture is able to fulfil the safety objectives resulting from the FHA. The Aircraft Safety Model contributes to refine the aircraft system architectures and flight crew contributors operations. It provides safety outcomes to the Backbone model

EXPERIMENTS IN MODEL BASED SAFETY ANALYSIS: FLIGHT CONTROLS

investigating failure propagation models and more specifically AltaRica model-based safety analysis. This paper presents results and lessons learnt from an industrial system architecture modeling experiment: rudder control system of the Airbus A340-500/600 aircraft. After introducing failure propagation model construction and analysis, the paper focuses on modeling the reconfigurations, the command/monitoring architecture and finally the latent failures. The main advantage of this approach is the improved readability of safety analysis results that facilitates a quick understanding of the system behaviour. This improves the communication between the safety and design communities. Copyrigh

Reliability analyses of workstation failure data

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Safety Assessment with Altarica - Lessons Learnt Based on Two Aircraft System Studies

Abstract: AIRBUS and ONERA used the AltaRica formal language and associated tools to perform safety assessments. Lessons learnt during the study of an electrical and hydraulic system are presented. Key words: dependability, aircraft, formal methods AIRBUS and ONERA were recently involved in the ESACS (Enhanced Safety Assessment for Complex Systems) European project. This project aimed at developing safety assessment techniques based on the use of formal specification languages and associated tools. We used the AltaRica (Arnold et al. 2000) formal language that is supported by Cecilia OCAS workshop developed by Dassault Aviation. Two case-studies based on AIRBUS aircraft electrical and hydraulic systems were used to validate the approach (Kehren et al. 2004b). In this paper we present lessons we learnt during ESACS. Lessons are sorted in three categories: Advantages are situations where the use of AltaRica was clearly positive, Difficulties are situations where the use of AltaRica was not directly positive but we found out how to circumvent the difficulties and the remaining situations are considered to be Limitations

Fractional Flow Reserve to Guide Treatment of Patients With Multivessel Coronary Artery Disease

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