Decoding DO-178C Software Levels: A Comprehensive Guide


DO-178C, also known as Software Considerations in Airborne Systems and Equipment Certification, is a crucial standard in the aviation industry. This guideline, utilized globally, focuses on the safety of software in airborne systems. Understanding its various software levels is paramount for anyone involved in developing or implementing aviation software. This article aims to provide a comprehensive guide to these software levels, elucidating their significance in ensuring aviation safety.

Understanding DO-178C

DO-178C, issued by the Radio Technical Commission for Aeronautics (RTCA) and the European Organisation for Civil Aviation Equipment (EUROCAE), is the bible for software development in the aerospace industry. It aims to ensure that software in airborne systems and equipment performs reliably and without causing any potential hazards. An essential part of DO-178C is the classification of software into levels based on the potential consequences of its failure. This classification impacts the rigor of software development, verification, and documentation processes, thereby making it a vital concept to grasp.

Overview of DO-178C Software Levels

The DO-178C standard classifies aviation software into five levels, from Level A (most critical) to Level E (least critical), based on the potential effects of a software failure.

Deep Dive into Each Software Level

Level A: Catastrophic

Software that, in case of failure, can prevent the continued safe flight and landing of an aircraft falls under this level. An example is the software controlling the aircraft’s Flight Control System (FCS). Such software undergoes the most stringent processes, including extensive reviews, analyses, and testing for compliance verification.

Level B: Hazardous-Severe

Level B software is one whose failure can lead to a large reduction in safety margins and serious or fatal injury to a small number of occupants, but which would not prevent continued safe flight and landing. An example would be the software controlling the auto-throttle. The verification processes are slightly less rigorous than Level A but still significantly robust.

Level C: Major

Software is categorized as Level C when its failure can lead to a significant reduction in safety margins or functional capabilities, discomfort to occupants, or possible injuries. An example might be the software controlling cabin pressure. The verification requirements for Level C software are less intensive than for Levels A and B.

Level D: Minor

This level includes software that, if failed, would only lead to a slight reduction in safety margins or functional capabilities, or slight discomfort to occupants. An example could be in-flight entertainment systems. The required rigor for Level D software verification is relatively low compared to the other levels.

Level E: No Effect

The least critical software falls under Level E. Its failure has no effect on aircraft operational capability or safety. An example could be a passenger’s reading light control software. This software undergoes the least rigorous verification process.

Determining the Appropriate Software Level

Several factors contribute to the classification of software into specific levels, such as system complexity, software functionality, and the potential impact of software failure on the aircraft and its occupants. An accurate failure condition classification is instrumental in defining the correct software level.

DO-178C Software Levels and Safety

The primary purpose of defining different software levels is to ensure aircraft safety. More critical systems undergo more rigorous verification and validation, minimizing the possibility of software-related hazards during flight operations. Accurate classification is vital to this process, ensuring that safety-critical software receives the attention it requires.

Challenges in Implementing DO-178C Software Levels

While implementing DO-178C software levels brings unquestionable benefits, it is not devoid of challenges. It requires a significant investment in time and resources. The rigorous verification process, especially for Level A and B software, demands extensive expertise. However, using tools that automate some tasks, following the guidelines closely, and seeking advice from experts can significantly simplify the process.


Understanding DO-178C software levels is integral to developing and managing software in the aviation industry. These levels guide the rigor required at each stage of software development, ensuring safety remains at the forefront. While the implementation of these guidelines may present challenges, the reward is aviation software that we can all trust.

Do you want to further explore DO-178C or discuss its software levels? Please feel free to reach out or comment below. As we navigate the complex landscape of aviation software, shared knowledge and experiences can only make us safer and more efficient.

Decoding DO-178C Software Levels: A Comprehensive Guide
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