FAA AC 20-115 Software Certification Testing (DO-178C)

The Federal Aviation Administration's Advisory Circular (AC) 20-115, titled "Software Design Assurance for Airborne Systems and Equipment," is a critical document that ensures the safety and reliability of avionics software used in civil aviation. This standard aligns with the broader aviation industry’s requirements as outlined by the International Civil Aviation Organization (ICAO). DO-178C, which is the latest version of this standard, provides guidelines for the development, integration, verification, and validation of safety-critical software.

The certification process under FAA AC 20-115 requires a comprehensive approach to ensure that avionics software meets stringent quality standards. This involves several key steps: initial risk assessment, software architecture design, code walkthroughs, peer reviews, static and dynamic analysis, integration testing, verification, validation, and finally, the issuance of a DO-178C Software Certification Package (SCP).

The process begins with a thorough understanding of the system’s requirements. This involves identifying all safety-critical functions that the software must perform. The next step is to design an architecture that ensures modularity and traceability between the software components and their functional requirements. Once designed, the software undergoes various levels of testing—unit tests, integration tests, and system-level tests—to ensure that it behaves as expected.

Static analysis tools play a crucial role in identifying potential defects before actual execution. Dynamic analysis involves running the software under controlled conditions to observe its behavior and performance. Verification ensures compliance with design specifications, while validation confirms that the software functions correctly within its operational environment. Compliance with DO-178C standards is critical for any aerospace company aiming to gain FAA certification.

The output of this process is a DO-178C Software Certification Package (SCP), which includes evidence demonstrating compliance with all aspects of the standard. This package serves as proof that the software meets the required safety and reliability criteria. The SCP must be submitted to the appropriate aviation authority for review, and once approved, it allows the software to be used in certified aircraft.

Given the complexity and critical nature of avionics systems, this certification process is essential. It ensures not only that the software functions correctly but also that it remains robust against potential failures or malfunctions under various operational conditions. This is particularly important given the high stakes involved in aviation safety.

International Acceptance and Recognition

The FAA AC 20-115 standard is widely recognized within the global aerospace industry as a benchmark for ensuring the safety of avionics software.
Many international civil aviation authorities, including those in Europe (EASA), Australia (JAA), and other regions, have adopted similar standards or reference DO-178C guidelines.

The widespread acceptance of this standard ensures that certified software is interoperable with systems from different manufacturers. This interoperability facilitates the integration of avionics components into complex aircraft platforms, streamlining the manufacturing process for aerospace companies and reducing certification timelines.

Competitive Advantage and Market Impact

Aircraft manufacturers can leverage DO-178C certifications to demonstrate their commitment to safety and quality, thereby enhancing their market reputation and attracting more business opportunities.
The standard also provides a competitive edge by ensuring that avionics software is robust and reliable, reducing the risk of in-flight failures or malfunctions, which are critical for maintaining public trust in aviation services.

By obtaining DO-178C certification, aerospace companies can differentiate themselves from competitors who may not adhere to such rigorous standards. This differentiation can lead to increased sales and market share, especially in regions with stringent safety regulations.

Frequently Asked Questions

What is the purpose of FAA AC 20-115?

The primary purpose of FAA AC 20-115 is to ensure that avionics software used in civil aircraft meets stringent safety and reliability standards. This ensures that the software can perform its intended functions safely, even under adverse conditions.

Does DO-178C apply only to new systems?

No, DO-178C applies not only to the development of new software but also to the modification and maintenance of existing avionics software. Compliance is required throughout the lifecycle of the system.

What are the key differences between DO-178A, B, and C?

DO-178C introduces more detailed requirements for software development, integration, verification, and validation. It provides a structured approach to ensure that all levels of safety-critical software meet the necessary standards.

How long does it take to complete DO-178C certification?

The duration can vary depending on the complexity and size of the software project. Typically, it can range from several months to over a year.

Is there any specific software that requires DO-178C certification?

DO-178C is applicable to all safety-critical avionics software used in civil aircraft. This includes flight control systems, navigation systems, and other critical components.

What are the penalties for non-compliance with DO-178C?

Non-compliance can result in significant delays in certification, financial penalties, or even the grounding of aircraft. The FAA may also issue warnings and take other enforcement actions.

How does DO-178C ensure software reliability?

DO-178C ensures software reliability through a structured approach that includes risk assessment, design reviews, static and dynamic analysis, integration testing, verification, and validation. This process helps identify and mitigate potential defects early in the development cycle.

Is there any exception to DO-178C?

Exceptions may be granted for specific cases where the software does not meet the criteria outlined by DO-178C. However, these exceptions must be justified and approved by the appropriate aviation authority.