Supplements of DO 178C – Where do they come from and what is their content?

With the enhancement of the RTCA DO 178B to the RTCA DO 178C, four so-called supplements have been developed. These supplements of DO 178C define the conditions under which modern software development methods can be used in aerospace. If you look at the history of the RTCA DO 178, you will notice that changes to the standard are rarely made. For example, the RTCA DO178B was released in 1992. Nearly 20 years have passed before the RTCA DO178C was released. It can be assumed that the same period of time will elapse again until the standard is renewed. This is a measure of how profound and lasting the creation of the DO 330, DO 331, DO 332 and DO 333 supplements has been, which is the only way to meet this demand. The following article provides answers to the following questions:

• What modern development methods are the supplements of DO 178C concerned with?
• What are the first steps if you want to use one or more supplements?

What is the content of RTCA DO 330?

The standard defines the procedures for using tools in the development of safety relevant software. Tools can also contain errors and therefore it is useful and necessary to define certain guidelines for their use.

There was a chapter in the RTCA DO178B for this, which was extended and clarified in the course of the further development to DO178C. Tools can basically be divided into 3 categories:

1) Tool can introduce errors in the operational software

2) Tool automates parts of the verification process and the results from the tool are used to eliminate verification or development steps.

3) Tool can’t cause errors in operational software, but it can’t find errors

Most of the DO330 uses category 1 and 2 tools. These tools require a development process that is very similar to the development process for which the tool delivers a result. This means that the development effort can be huge. On the other hand, practical experience shows that most tools are to be classified according to category 3. Essentially, a documented functional verification must be provided, which significantly limits the effort.

What is the content of RTCA DO 331, RTCA DO 332 and RTCA DO 333?

The structure of the RTCA DO331, DO332 and DO333 supplements are very similar to the RTCA DO178C. This means that the philosophy of the RTCA DO178C is applied to the respective method and the requirements are almost inevitable.

What development methods were these 3 supplements concerned with?

The RTCA DO331 presents methods for model-based development and measures for the use of these methods in aerospace.

The RTCA DO332 introduces techniques for the application of object-oriented development approaches and defines measures to be able to use these techniques in aerospace.

The RTCA DO333 deals with formal methods and the corresponding conditions for the safe use of these methods in aerospace.

What are the first steps if you want to use one or more supplements of DO 178C?

The DO330 is probably the most frequently used standard, as tools play an important role in software development.

If you want to use one of the remaining 3 supplements, you need a clear strategy how to fulfill the requirements of the supplement. This happens in the planning phase of the project. The supplement will be taken into account in the preparation of the PSAC. Similar to the DO178C, a kind of traceability will be created for the supplement in order to ensure the correct and complete coverage of the required measures and enable a goal-oriented discussion with the authorities.

Conclusion

The supplements RTCA DO331, DO332 and DO333 now also allow the application of modern software development methods in aerospace. This is the main benefit of the supplements. At the same time, however, it should also be mentioned that the requirements to be met can be quite extensive, so that the classic development methods are still recommended in individual cases.

The RTCA DO 330 has its credit in clarifying the requirements for a tool qualification. New developments on the tool market have also been taken into account in the standard.

Overall, the supplements of DO 178C are part of a successful development of the RTCA DO 178B to DO 178C.

Related HEICON Blog posts

• RTCA DO 178C – Software quality in aerospace!
• RTCA DO 331 Model-Based Development and Verification in aerospace

The HEICON team will be pleased to support you with our services if you have individual questions regarding your project. Please send a mail to: info[at]heicon-ulm.de.