Signal-Validated Two-Step Command Architecture for Fault Tolerant Safety in Analog Avionics

Analog avionics systems, prized for their determinism and resilience to electromagnetic interference, remain integral to legacy and specialized aircraft. However, their inherent susceptibility to single-point failures and spurious signal transients poses significant safety risks. This paper proposes and details a Two Step Command Architecture (TSCA) as a novel safety-enhancing retrofit for critical analog flight control systems. The TSCA interposes a validation layer between the pilot's control input and the final actuator command, requiring explicit confirmation before any high-authority command is executed. The architecture employs parallel signal validation, cross-channel monitoring, and fault logic to detect discrepancies, signal faults, and implausible commands. A detailed system design is presented, including functional block diagrams and state-based safety logic. A case study applying TSCA to a hypothetical analog pitch trim system demonstrates its efficacy in preventing runaway trim scenarios caused by hardware faults. A comparative analysis against traditional single-path analog systems shows a theoretical reduction in the probability of hazardous failure by at least an order of magnitude, introducing minimal latency and complexity. The research concludes that TSCA offers a viable, deterministic method to significantly improve the safety integrity level of existing analog avionics without necessitating a full transition to digital fly-by-wire systems, thereby extending the operational life and safety of legacy aircraft platforms

کلیدواژه ها:

analog avionics ، signal validation logic ، Guidance and Navigation System ، Hybrid control system