System Integration Testing for Unintended Behaviors in Flight-Critical Aerospace Applications

From the systems development planning phase all the way through aircraft-level implementation verification, a focus on monitoring for and detecting unintended behaviors (instead of solely trying to prevent them) can increase aircraft safety and improve product robustness. Through the lens of designing and verifying a modern Air Data System, a flight critical product, this case study delves into numerous Systems Engineering practices focused on identifying and addressing unintended behavior early in the product development lifecycle. The paper's focus will be highlighting methods for meeting the unintended behavior related objectives of SAE ARP4754A for an example system's Design Assurance Level A items/functions and will include an accepted framework for System Stages of Involvement (SOI) audit success. Specific, real world cases where engineering actions have prevented unintended behavior during Commercial, Regional, or Business Jet service will be highlighted and compared with the types of unintended behavior investigated during hardware/software integration and implementation verification. Additionally, the paper will provide evidence related to this topic which supports the common industry perception that issues found and fixed earlier in the development period incur less cost. Finally, the paper will include a discussion of fertile grounds for discovering unintended behavior considering a standard/common specification level.