"The Safety Critical technical area addresses the analysis, development, verification and validation of software and systems that are classified as either safety- or mission-critical.
Systems classified as safety-critical are those where failure may lead to personal injuries, fatalities or harmful effects to the environment. Airborne systems in aircraft and signalling systems in railway are traditionally the best-known cases of safety-critical systems. Systems controlling industrial processes in chemical, petrochemical and nuclear plants are also in this category.
Mission-critical systems are those where failure may lead to either loss or major degradation of the mission performance. Traditionally the best known cases of mission-critical systems are unmanned space missions such as telecommunications and scientific satellites, and the energy production and distribution infrastructure.
Enterprise systems in banking, retail and other industries may also be considered mission-critical though we prefer to designate them ‘business-critical’.
The services delivered by the Safety Critical technical area aggregate a set of disciplines and technology that is closely related to international safety standards. These standards are a daily reference in the work performed by the Safety Critical technical area. The most common standards used are for aerospace: ARP-4754, ARP-4761, DO-178B and DO-178C, and DO-254; for railway: EN-501216, EN-50128 and EN-50129; for space ECSS-E-ST-40C and ECSS-Q-ST-80C; for automotive the ISO 26262 and for industrial systems in general IEC 61508.
The work performed by the Safety Critical technical area is characterised by the rigour of the engineering processes. The main challenge faced is to comply with that rigour in the most economically efficient way. The projects and activities developed by the Safety Critical technical area fall into the following categories:
- • Development of real-time embedded software in either full life-cycle, from requirements to final acceptance, or in partial life-cycle. Often the development entails close co-operation with the customer and in some cases members of the project team may work at the customer’s premises while interacting with the project team at home. The SW will typically be developed in either C or Ada and requires knowledge of real-time operating systems, microprocessor architectures and low-level communication protocols.
- • Verification and validation of real-time embedded software, from requirements and code reviews, to unit tests, integration and system tests. A full life-cycle embedded software development also includes V&V but this type of service is often delivered as specific projects, where we verify and validate software developed by the customer or a third party. The V&V services include not only testing software but also testing with hardware-in-the-loop. Typical tools used include VectorCAST, LDRA and bespoke validation facilities.
- • Development of integrated electronic systems comprising the software and the hardware that supports it. This requires competencies in both software and electronics, including the ability to procure and integrate COTS components. Typical systems developed include validation facilities with HW-in-the-loop and solutions for military C&C systems.
- • Functional safety assessment and reliability prediction (known as RAMS). This entails analysing the failure modes of systems using techniques such as Fault Tree Analysis (FTA) and Failure Mode Effects Analysis (FMEA). This analysis may contribute to both allocate criticalities to components and to reformulate the system design to minimise the number of critical components.
- Certification support to help our customers comply with safety-critical standards and training on those standards. This implies a wide body of knowledge in the technical, normative and application domain.
Typical projects include certification support for railway signalling systems, support for airborne software and hardware certification and training on standards such as DO-178C. The work in the Safety Critical technical area requires interest in safety aspects, the ability to analyse systems as a whole, to know that there is more than just software development and, of course, good reading and writing skills."
[INTERNAL] Source: CSW-QMS-2000-CPD-0174, VERSION: 13, 2017-08-09, Annex B.
