Model coverage analysis methods for flight control software of civil aircraft

The flight control system is the core safety-critical system of civil aircraft. The flight control software must comply with the highest safety level requirements. A model-based development approach is adopted for flight control software. For model-based development, model coverage analysis must be performed during the software verification process, based on the requirements of DO-178C and DO-331. Model coverage analysis primarily includes two aspects: first, verifying the coverage of requirements by the software, i.e., ensuring the model covers all high-level requirements; second, verifying the structural coverage of the model, i.e., identifying any unintended functions within the model. Model coverage analysis for flight control software is a critical step in ensuring the software meets airworthiness requirements. It focuses on the extent to which the structure and behavior of the model itself are exercised during testing within the model-based design process. Therefore, dual verification of model coverage is required at both the model level and the code level. Based on the objectives of software model coverage analysis, this paper proposes a comprehensive method for unintended function identification and model coverage analysis. This ensures the design model is thoroughly verified, thereby achieving a high confidence level.