Civil Engineering Reference
In-Depth Information
Fig. 5.21
Network topology
5.3.4.10
Development Process
The safety philosophy in aviation defines quantitative safety objectives and assigns
acceptable probabilities. The overall probability for a failure with catastrophic con-
sequences must be extremely improbable. This must be demonstrated to the air-
worthiness authorities for certification. The demonstration is endorsed through a
complete, detailed and documented safety analysis, which is one of the integral
parts of the software development process.
Guidelines for development of aviation software in the USA are defined in the
DO-178B. Since its production by the RTCA, the DO-178B has become a de facto
standard. The FAA's Advisory Circular AC20-115B established DO-178B as the
accepted means of certifying all new aviation software.
DO178-B is primarily concerned with development processes. As a result, cer-
tification to DO178-B requires delivery of multiple supporting documents and re-
cords. The quantity of items needed for DO178-B certification, and the amount of
information that they must contain, is determined by the level of certification being
sought.
The higher the consequences of a potential failure of the software (catastrophic,
hazardous-severe, major, minor, or no-effect) are, the higher is the DO178-B cer-
tification level. The levels are from A for the highest certification level through B,
C and D to E.
This aviation-specific development process had to be followed on an equipment
and on a system level.
5.3.4.11
Conclusion
Through clever system design and network management, a CAN bus-based safety-
critical smoke-detection system with deterministic behaviour, capable of fulfilling
the safety and reliability requirements, was developed and approved by airworthi-
ness authorities. The robustness and reliability of CAN in this airborne application
