System Dependency Analysis for Complex Aircraft Systems 2007-01-3852
This paper presents a method for analyzing complex aircraft system availability and minimum acceptable control requirements for multiple failures or event scenarios considering multiple relevant system properties. Aspects such as functional relationships and interdependencies, and system properties such as equipment, wiring, installation and (power) supply are included in the analysis.
The method covers most aspects of a system level common cause analysis (sourced in 14CFR/CS §25.1309 “Equipment, Systems and Installation” referencing ARP4761 (e.g. “Rotor/Tire Burst”)) and analyses required to show compliance to 14CFR/CS §25.671 “Control Systems”, especially for supply system failures (e.g. “single plus probable failure” and “all engine out”).
The method generates a system model from functional block diagrams. The interdependencies of resources that support functions are evaluated by the integrated analysis to determine if a function is operational. The analysis of the system in combination with the associated supply systems (e.g. hydraulic and electric power) allows determination of system controllability or fault propagation when these systems are subjected to failures. System redundancies are analyzed for their independence at a system function level as well as on the supply system level. The model also allows for evaluation of particular risks and zonal aspects of equipment installation and wiring.
The system model and analysis is developed using common desktop computer software packages. This technique allows for a collaborative analysis environment without additional software expense. Large and complex systems can be modeled to a sufficient level of detail in order to satisfy the system safety concerns for both, design and analysis program phases and complements the traditional suite of safety analyses recommended in SAE ARP4761.
The paper provides an overview of the system dependency analysis method and the modeling technique. A quad-redundant flight control system is used as an example.