Introduction to DO-178

Evolution of standard: DO-178 to DO-178C

DO-178 was developed in the late 1970s and originally released in 1982. The original standard provided a prescriptive set of design assurance processes for software developed for airborne systems and focused on testing and documentation.

DO-178 was updated to DO-178A in the 1980s, with the update for the first time defining different levels of activities depending on the criticality of the system for which the software was written.

In 1992, DO-178B was released and was a total re-write of the existing DO-178 standard. Rather than the previously prescriptive processes described, DO-178B detailed a combination of activities and objectives that a design assurance process must meet. By defining activities and objectives only, airborne software developers had more flexibility in terms of development approaches. DO-178B did, however, specify key attributes for a design assurance process, derived from airworthiness regulations. For example, identifying unintended function and specific verification of software behavior whilst running on the final target hardware.

History of DO-178
History of DO-178

DO-178B also introduced the concept of the Design Assurance Level (DAL). DAL categorization determines the amount of rigor required by the design assurance process. DAL categorization itself is determined by the impact that a specific system's failure could have in terms of Aircraft Safety. The more critical the DAL, the more activities and objectives are required. DAL categorization continues to be used in DO-178C.

Condition: Catastrophic Failure rate: ≤ 1x10-9 Objectives: 71
Condition: Hazardous Failure rate: ≤ 1x10-7 Objectives: 69
Condition: Major Failure rate: ≤ 1x10-5 Objectives: 62
Condition: Minor Failure rate: 1x10-5 Objectives: 26

*The final DAL is DAL E, which confers no failure rate condition or objectives.

In 2012, DO-178C was released, partly due to the advancement of software development technologies which were not accounted for in previous iterations of the standard. DO-178C clarified details, removed inconsistencies and included supplements to provide guidance for the use of specific technologies in DO-178C projects.

Design Assurance and Stages of Involvement

The basic structure of a Design Assurance process consists of three components:

  • Planning
  • Development
  • Integral processes

“Stage Of Involvement” (SOI) reviews are typically used by a certification authority to determine compliance to DO-178C guidance in a given project. The four review stages are:

  • SOI#1 or Planning Review
  • SOI#2 or Development Review
  • SOI#3 or Verification Review
  • SOI#4 or Certification review

For each of these review stages a specific aspect of the design assurance process followed is evaluated. Typically, certification authorities require that each SOI is completed in order. SOI stages represent key milestones in a DO-178C project.

Learn more about DO-178C by downloading your free 70-page DO-178C Handbook.

DO-178C Processes
DO-178C Process and Stages of Involvement

Choosing a testing tool

DO-178C guidance is designed to ensure that clear best practices are defined and followed by avionics system developers. DO-178C guidance also prescribes specific software testing measures that are dependent on the criticality of the system in question.

There are a wide range of embedded testing tools available to safety-critical software developers that make expensive software testing significantly more efficient and cost-effective. This whitepaper describes 5 key factors that should be taken into consideration when making the important decision on which embedded testing tool to use for your project.

DO-178C Handbook

Following DO-178C guidance when developing safety-critical avionics software can be complex, and there are many potential pitfalls along the way.

This handbook delivered by Rapita Systems and ConsuNova Inc. presents useful information for DO-178C beginners and experts alike, including a description of DO-178C processes and how objectives can be met, and insights from best practice.