DO- 178C Compliance — What All Should You Be Aware Of?
For any software-based aerospace system to be put into practical use, there is a certain certification process that it must go through under authorities like FAA, EASA or other state certification bodies. These different authorities acknowledge some common guidelines, which need to be followed by the aerospace software systems to be licensed as fit to use for commercial purpose.
DO-178C, Software Considerations in Airborne Systems and Equipment Certification is the chief document that is to be complied with for commercial certification of aerospace systems, acknowledged by FAA, EASA and Transport Canada. DO-178C compliance was developed as a successor of DO-178B, through a joint endeavor of RTCA and EUROCAE in 2011. The title of the new document is DO-178C (ED-12C) and has been in use since January 2012.
To put is precisely, DO-178C is a standard that needs to be complied with in both commercial and military aerospace industry, without which a flight is never happening.
Looking at the Safety Levels:
DO-178C categorizes the aerospace software systems into five different levels of security and criticality, judging by to what extent can the atypical software behavior can contribute to a system failure.
Level A: Software causing a catastrophic system failure. The associated structural coverage objectives are Modified Condition/Decision Coverage, Decision Coverage and Statement Coverage.
Level B: Software leading to a hazardous or severe failure of the system. The associated structural coverages are Decision Coverage and Statement Coverage.
Level C: Software causing major system failure. The associated structural coverage here is Statement Coverage.
Level D: Software causing minor failures of the system. There is no associated structural coverage here.
Level E: Software causing no safety effect on the system.
As evident, these levels indicate the risk involved for each software, and the more risk elements, the more safety objectives are there to be met. Level A software can lead to fatal consequences like plane crash, Level B may cause severe passenger injuries, while level C may result in passenger inconvenience. Level D has minimal effects like flight delay and Level E has no consequences on safety.
DO-178C Compliance: The guideline must be followed at every stage of the development cycle.
Planning: The planning stage is to determine exactly what type of a product you are going to sell in the market and compliance starts from this very phase.
While compiling requirements, it needs to be supervised that the requirements are in congruence with the standard. Managing the requirements depends on the approach of each company. It can be something as simple as a Microsoft Word document or more high-end, complex management tools.
Quality assurance should be an indispensable part of the planning process- the organization should have a clear view of how they are going to ensure that the codes are as per the standard and the testing is carried out properly to make sure the compliance guidelines are met.
Development: To ascertain that the standards are being maintained during the development process, few things need to be kept in mind:
a) Properly defined requirements
b) Development of test cases in accordance with requirements
c) Codes written to meet the requirements
d) The actual testing processes should be according to the test cases to show that the requirements are being maintained.
e) Every element should be linked through traceability.
Verification: The verification stage is to ensure that all the requirements set by the compliance standards are met properly. The process should validate three key elements:
a) Requirements
b) Code
c) Testing processes
The verification stage should substantiate that the software code meets the requirements both in terms of compliance and otherwise. To achieve this, a traceability matrix needs to be created to demonstrate how the requirements, codes and tests are linked and are according to the compliance guidelines. You should consider partnering with a reliable QA organization, with proven expertise in testing avionics software, to ensure you achieve compliance successfully.
DO-178C development tools help an organization produce systems that will sail through the verification process. To ensure that you have chosen the right tool, the basic things that need to be looked out for are intricate test coverage, traceability all throughout the development lifecycle and thorough quality assurance.
With the growing sophistications of the avionics industry, it is a given that the complications and sophistication of the guidelines like DO-178C will keep growing. For any organization to be well prepared to cope with this would require them to be able to isolate components at the software unit level, along with the LRU level, all the while replicating the rest of the interfaces.
