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More Integrated System Safety Assessment

Tags: Air

State of the Art - Background

The increase of aerospace systems complexity has led to an increasing time-to-market for new technologies, increasing costs to demonstrate safety, a greater demand for skilled resources and a limitation on design iterations, which means there is less time to optimise designs that are compliant with safety targets.

The FP6 ISAAC Specific Targeted Research Project and the SPEEDS Integrated Project represent the main source of the current state of the art in the fields of functional, architectural and implementation level contract and model-based safety specification, automated logical and spatial reasoning about the safety of discrete and hybrid systems architectures, implementation and installation specification, and image processing.

MISSA will advance the state of the art by developing and combining the above technologies to develop a seamless argumentation framework for specifying, and substantiating aircraft systems functional safety specification, and will look to optimise systems installation by accounting for safety assessment influence on systems installation and finally providing means to audit the physical installation against the safety-driven installation requirements. MISSA deliverables will reduce the time to analyse aircraft systems specification and its installation definition, and will provide more time for system optimisation.


The MISSA project has the following objectives:

- Develop an argumentation framework that is capable of linking every systems safety engineering activity that leads to an aircraft specification from Physical Testing Results, Design and Model Specification and Analysis through to In-Service Events Data;

- Develop the ability to carry out Installation Optimisation, driven by Safety Installation Requirements and some Performance Requirements;

- Develop the ability to check consistency of assumptions and specification 'laterally' between dependent systems within the aircraft level, systems architecture level and detailed systems implementation level, and 'vertically' including consistency between analysis results from the aircraft level, down through to the detailed systems implementation level;

- Devise a method for modelling the relevant aspects of specification at aircraft level, systems architecture and implementation level so that they can be analysed to demonstrate the adequacy of the relevant level of specification at addressing the airworthiness requirements;

- Develop the ability to include within the detailed systems implementation-level models, non-linear mathematical expressions to more accurately describe the behaviour of the systems;

- Develop the ability to abstract time in order to make time-dependent systems analysable with reasonable time and resources.

Description of Work

The work is divided into six technical work packages and two non-technical work packages (WP):

WP2: Clarify the detailed project requirements and train all the teams so they can work on the candidate modelling methods and analysis techniques. The resulting detailed requirements are used as key performance indicators to evaluate the project.

WP3: Focus on the optimisation of safety requirement allocation and installation at the aircraft level, mainly modelled thanks to formal requirement languages such as RAT and MathSAT.

WP4: Deal with the assessment of systems architecture by using mainly AltaRica models.

WP5: Handle the detailed design analysis by using mainly Simulink, Statemate and Scade models.

The correlation between consecutive levels is tackled by WPs 4 and 5.

WP6: Develop synthesis, argumentation and change-management methods and tools to support the justification of safety objectives.

WP7: Focus on platform evaluation. Several models are developed and used to test the platform, one of which is a leading case study that spans from aircraft down to detailed systems implementation level. Some models have sufficient detail to show what is needed to industrialise the tools.

WP8: Publicise the achieved objectives at industry working-group meetings and scientific conferences.

Expected Results

The aforementioned capabilities will lead to reducing the time taken to complete subsequent design iterations, offering either a reduction to the development costs, more time to have a greater level of performance and weight optimisation or an increase in the agility of design, and so will enable the design organisation to respond to changing market demand through the design life.

It will also improve the means to maintain and keep active the links between safety claims and the evidence used to substantiate it, by improving the maintenance of the complete chain of evidence.

It will provide one aspect of what is needed to produce affordable and better performing products that are better aligned to societal needs.

Some consortium members are active in the main industrial working groups that focus on aviation safety and participate in the day-to-day development of aerospace recommended practice. The methods developed within MISSA, along with the evaluation results, will be used to demonstrate the methods and potential gains they offer to the industry's working groups with the intention of gaining their support for the industrialisation of these methods.

The results from MISSA will improve the ability for industry to respond to market demand by making safety management more agile. Industrial organisations that implement this framework will be better placed to compete.

Scope and nature of models used in the model-based safety analysis framework
Scope and nature of models used in the model-based safety analysis framework