Designing Software to Aerospace Requirements
Choosing the right software development lifecycle is crucial to the successful implementation of any project. Developers have many choices to choose from such as Waterfall, V-model, Agile, and spiral, just to name a few. The life-cycle adopted can vary with the industry, scope of the software system, and product in mind. When safety and reliability are critical, however, requirements driven development is often the best choice given its long track record of success and it’s alignment with regulatory requirements.
The need for a requirements-based approach and adherence to DO-178 makes the V-model the development model of choice for the aerospace industry.
The V-model derives its name from the terms Verification & Validation and involves a sequence of phases with each phase completed in its entirety before the next phase is initiated. Each development phase also has a well-defined testing phase associated with it. Though it may not be as flexible as other potential methodologies out there, it is championed within aerospace for its top-down testing approach, support of requirements-driven design, and consequent suitability for the development of safety-critical software.
The V-model maintains the clean separation of requirements development and software development required by DO-178 and facilitates the early detection of defects. Further, traceability between requirements, design data, and test artifacts is made much easier. Good development practices suggest that every requirement should be tested, and every line of code should match to a requirement. In aerospace, this is not only good practice, it is obligatory. In complex projects, there can be many thousands of requirements, thousands of functions, thousands of test cases, and thousands of test result artifacts.
Tracking requirements traceability is no small task for a project of even moderate complexity, but adhering to the V-Model design makes it a more manageable task. Throughout the V-model lifecycle, Aversan employs the use of a requirement management system to record the relationship between various business requirements, system requirements, test cases, and design data.
Aversan has successfully utilized this approach in the past to develop products as diverse as:
A Multi-purpose HDD Controller
Aversan was responsible for the engineering of the requirements definition and system design of the controller to ARP4744 and ARP4761. In addition, Aversan performed hardware and software development to DO-178B and DO-254 DAL B.
A Complex Health and Usage Monitoring System
Aversan delivered a turn-key product development for a Specialized Data Acquisition system, and performed mechanical, hardware, FPGA, and software design & analysis, successfully satisfying commercial and military noise and environmental requirements.
A System Integration Lab for an Environmental Control System (A350)
Aversan developed and built a System Integration Lab (SIL) for an Environmental Control System (ECS). The facility is a closed-loop control test platform, integrating actual controller hardware with plant models to exercise the ECS controllers as if they were deployed on the target aircraft. By using hardware-in-the-loop testing and accurate simulation models, the SIL raised more internal problem reports than the legacy test methods, with a 95% legitimacy rate.
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