RAMS- and mass- based optimization of aircraft on-board system architectures during preliminary aircraft design

In this work, various on-board system architectures have been analyzed in order to replicate existent long- and medium-haul aircraft system architectures and possible new architectures related to more and all electric concepts. All methods for designing and modelling the design space have been explored using an internal software for the System Architecture Design, from the most basic concepts to the most complex ones. In this phase of the work the on-board systems analyzed were mainly the Flight Control System and Landing Gear System. The design space was adapted to the necessity of the work including the possible choices for the range of aircraft of interest. The final design space included also Electric Power System and Hydraulic Power System for each aircraft on-board system, a concept introduced to make possible a deeper knowledge of the relations between power consuming systems and power generation and distribution systems. For the current work the focus was mainly on the on-board system itself Every possible architecture design has been evaluated through a multi-objective optimization tool whose objectives were two: operational reliability and system mass. For the optimization part the Flight Control System has been considered as on-board system case study evaluating a wide range of architectures including different actuation systems and actuator types for each aircraft case study chosen. The work was conducted mainly on Hydro-Static Actuators, Electro-Hydraulic Actuators, Electro-Mechanic Actuators and Ball-screw. Previous studies conducted to have a deeper knowledge of differences between these actuators highlighted that newer and more electric aircraft are usually heavier but more reliable than the Hydro-Static Actuators. Optimization evaluations were conducted to find the most optimal architectures and define the Pareto front between both objectives. Genetic algorithms were selected due to the nature of the problems and its design variables. The system sizing related to the Flight Control System has been realized integrating in the loop the sizing of the actuators and the components related to them based on the function of each one, according to hinge forces and moments to face. The operational reliability has been developed through a Reliability Block Diagram for the quantitative estimation. Each component time-variable reliability was calculated through a probability function to consider the non-constant failure rate of the components throughout their life cycle