How does DO-178C affect a program formerly created under DO-178B?

Small but subsequent changes in DO-178C explain modern technologies and methodologies in clear, concise terminology

DO-178B and DO-178C are two softwares that have been developed to use in the aerospace industry. First, DO-178B is a guideline that deals with the safety of safety-critical software employed in certain airborne systems. Next, DO-178C was created, adapting and refining important information from DO-178B. DO-178C is the current accepted standard that governs certification of all software for airborne systems in commercial aircraft. Below, we will define the differences between both documents in further depth.

DO-178B vs. DO-178C

DO-178C was created by SC-205 to revise DO-178B with current software development and verification technology changes. Although its text and structure remains mostly the same, adaptations include:

  • Clear, concise language and terminology
    • DOC-178B had consistent issues with the use of words, including, but not limited to, “guidance,” “purpose,” “goals,” and “objective.” These terms were clarified in a glossary, ensuring that they were being utilized correctly and consistently throughout the entire text
  • Addressing errors and inconsistencies
    • The new document addressed known errors from Annex A
  • An increased number of objectives for Levels A, B and C
  • Explicit clarification of hidden objectives listed in Level A of DO-178B
    • Assumed hidden objectives were added to Annex A
  • Addition of Parameter Data Item Files, providing new information that influences behaviour of an executable object code

DO-330/ED-215 “Software Tool Qualification Considerations” was initially added into the new document, then removed. Instead, DO-178C includes information on deciding when to apply DO-330 tool qualification.

The most major changes involved adding technological supplements to the new document. These supplements that add, delete or modify guidance of application to specific techniques or technologies were added instead of expanding DO-178B, to account for current and anticipated software development techniques. These supplements included:

  • DO-331: addressing model-based development (MBD) and verification, the document also acknowledges the ability to use modeling techniques to improve development and verification while avoiding common modeling pitfalls
  • DO-332: addressing object-oriented software and when it should be used
  • DO-333: addressing formal methods to complement testing

 

How these changes affect software development

The new standards adopted by DO-178C largely surpass former expectations of DO-178B. Its technological supplements now allow avionics professionals the tools and guidance to achieve cost-effective certification. DO-178B is outdated and lacks the ability to offer a near-zero software defect rate required to produce new developments that meet or exceed deadlines.
Have any more questions about the depth and scope of the differences between DO-178B and DO-178C that we did not address in this article? Let us know!