LDRA tool suite smooths DO-178C DAL A certification

The PCU manages hundreds of analogue and digital signals to allocate power sources (including external AC, external DC, and engines) and to switch smoothly between them. Its development was subject to DO-178C, the principal standard referenced by certification authorities in the approval of commercial software-based aerospace systems. Because failure of the PCU system would represent a catastrophic failure condition for the aircraft, the project was assigned Design Assurance Level A (DAL A).

Critical Software applied both the static and dynamic capabilities of the LDRA tool suite to the project.  Static analysis can be likened to an automated ‘inspection’ of the source code, comparing the code under review with the chosen software coding standard. Non-conformances are highlighted as required by DO-178C, along with other undesirable characteristics such as high complexity.

Dynamic analysis involves executing some or all of the code, showing that it has been exercised sufficiently and that it behaves in accordance with requirements. Vitor Conceição, Principal Engineer at Critical Software, said: “Change requests are common to almost all projects, and they are invariably frequent, unexpected, and demand a very short response time.

“The LDRA tool suite’s test case files store all the settings required for test re-execution, including test data and environment/target set-up. This makes regression testing in response to change much more efficient, especially once the project enters change control.”

The LDRA tool suite helps developers to build quality into their software development lifecycle. It is a suite of software standards compliance, testing, and verification tools that reflect industry best practices to help ease the development of high-quality safety- and security-critical products. Its open and extensible platform is unique in its integration of software lifecycle traceability, static and dynamic analysis, unit test, and system-level testing on virtually any host or target platform.

“Of all the safety-critical standards, DO-178C DAL A is arguably the most demanding,” added Ian Hennell, Operations Director, LDRA. “It is therefore especially pleasing that although the LDRA tool suite was their client’s tool of choice for this project, the Critical Software team’s experience with it has left them equally happy with that choice.”