DO-254
Modern aircraft systems are complex, interconnected, and essential to the safety of crew and passengers alike. When a single hardware design error can cost the lives of hundreds of people, it’s necessary to take all possible steps to prevent it from happening.
Aerospace manufacturers seeking to develop mission-critical airborne electronic hardware should take a verifiable approach during the design of the product and follow a relevant formal safety standard, namely DO-254.
What Is DO-254?
Also known as EUROCAE ED-80, DO-254 (Design Assurance Guidance for Airborne Electronic Hardware) is a safety standard used during the development of airborne systems.
The standard provides guidance to such electronic hardware as line replaceable units, circuit board assemblies, custom micro-coded components, integrated technology components, and commercial off-the-shelf components.
DO-254 can be described as the counterpart to DO-178C (Software Considerations in Airborne Systems and Equipment Certification), which deals with software-based aerospace systems.
Understanding the DO-254
DO-254 designates different Design Assurance Levels, or DALs, to various hardware systems of the aircraft based on their safety criticality:
- Level A (Catastrophic): The failure of a Level A hardware system will cause or contribute to a catastrophic failure of the aircraft and cause a crash and/or deaths. An example of a Level A hardware system is the flight control system.
- Level B (Hazardous): The failure of a Level B hardware system will cause or contribute to a hazardous/severe failure condition and potentially cause a crash and/or deaths. An example of a Level B hardware system is the braking system.
- Level C (Major): The failure of a Level C hardware system will cause or contribute to a major failure condition and potentially cause stress and/or injuries. Examples of Level C hardware systems include various backup systems.
- Level D (Minor): The failure of a Level D hardware system will cause or contribute to a minor failure condition and potentially cause inconvenience. An example of a Level D hardware system is the ground navigation system.
- Level E (No effect): The failure of a Level E hardware system will have no effect on the aircraft or on the pilot workload. Passenger entertainment systems fall in this category.
Being a process-oriented standard, DO-254 proposes a specific workflow:
- Planning: The goal is to comprehensively document the project upfront, including as much information as possible and clearly explaining how the DO-254 requirements will be met.
- Requirements capture and validation: Requirements are at the center of DO-254, and the entire hardware project revolves around them. As such, each requirement must be written, preferably using requirements management software.
- Conceptual design: Larger design is broken down into smaller components at this stage to implement the captured requirements.
- Detailed design: During this step, each component described during the previous stage is developed according to the captured requirements.
- Implementation: This stage is technology-specific. One advantage of DO-254 is that it enables the manufacturer to remain at a fairly high level when documenting activities during implementation.
- Production transition: After the design work and the devices are ready to begin larger volume production, the design is transferred over to manufacturing.
- Validation and verification: This supporting process occurs throughout the hardware design, ensuring that the requirements are correct, complete, and verifiable.
- Configuration management: The purpose of configuration management is to help ensure that the device is developed in a structured, repeatable, and controlled environment.
- Process assurance: Every Do-254 project plan should be accompanied by a document describing the steps that will be taken to ensure that the plan will be met.
- Certification liaison: To ensure DO-254 compliance during the development process, it’s important to engage with a certification authority, known as certification liaison.
How to Support DO-254?
Projects that aim to meet DO-254 typically end up being far more expensive than comparable projects without DO-254. The extra cost of DO-254 projects stems largely from poor requirements management techniques.
Requirements are at the core of DO-254, and the ability to efficiently document, analyze, trace, prioritize, and agree on them can be the difference between project success and project failure.
Fortunately, modern requirements management tools integrate in the same environment support for risk management, test management, issue and defect tracking, and change management, helping overcome the numerous challenges that may arise during the development of mission-critical airborne electronic hardware.
Selecting the Best Requirements Management Tool
When developing a complex electronic hardware system, an Excel spreadsheet simply isn’t an adequate solution for capturing requirements. However, not all requirements management tools are created equal, so it’s important to choose the right one for the job.
When selecting a requirements management tool to support DO-254, start by evaluating the tool’s ability to define requirements, specify relationships between them, and export the captured requirements to create documentation.
The ability to visualize requirements and the relationships between them can go a long way in creating alignment among stakeholders and developers. The tool should provide the ability to automatically establish relationships across requirements and run test cases.
Other important capabilities include team collaboration and integration with other software tools used during the development of the hardware system.
Visure Requirements meets all these criteria, offering an easy yet comprehensive Requirements Management ALM platform that supports an automatic capture of elements from MS Word, MS Excel, ReqIF and other sources.,
Visure Requirements features visual role-based workflows that make it possible to align the processes and the tools and follow the life of a requirement through its development and specification, to its subsequent deployment and use, and through periods of ongoing refinement and iteration in any of these phases.
Conclusion
Meeting DO-254 can be a difficult and costly process, but a capable requirements management tool, as well as sufficient upfront planning, can go a long way in achieving DO-254 approval. Visure Requirements ALM is an award-winning requirements management solution that all engineers and engineering managers that face the DO-254 process should strongly consider.
