A Multidisciplinary Possibilistic Approach to Size the Empennage of Multi-Engine Propeller-Driven Light Aircraft

Abstract

In considering aircraft design, it is very important to effectively size the tail configuration for stability and control. Multidisciplinary design optimization (MDO) focuses on the use of numerical optimization in the design of systems with multiple subsystems or disciplines of consideration. However, MDO uses deterministic calculations, and does not consider the uncertainties that arise from the employed analyses, including errors due to linearization and simplification. For problems with inadequate input data, the possibility-based design optimization (PBDO) scheme can be implemented in its stead to achieve reliable designs using membership functions for epistemic uncertainties. A multidisciplinary, possibilistic approach is presented to define the sizing of the empennage configuration of a twin-engine propeller-driven aircraft by changing shape parameters while satisfying the design requirements given the tailless aircraft configuration, the flight conditions, and various uncertainties. The corresponding disciplines are aerodynamics, stability and control, propulsion and weight and balance. Herein, different design requirements are considered including longitudinal/lateral/directional trim and stability characteristics, manufacturing and controllability criteria, handling qualities, operational requirements, airworthiness and survivability. The resulting aerodynamic characteristics and flight dynamic stability outcomes show that the optimized tail configuration for the proposed aircraft fully complied with airworthiness requirements and predefined constraints while considering several uncertainties due to the use of early-stage statistical estimations. The proposed approach can be used to enhance the preliminary design of multi-engine propeller-driven light aircraft where only low-fidelity, statistical estimations are available. The resulting output is not only an optimized aircraft configuration, but one where the stability of the design has been ensured. In this work, the aerodynamic characteristics have been determined using a validated semi-empirical program called MAPLA, developed for light aircraft designs and development in the preliminary design phase. Furthermore, the optimization framework consists of a deterministic optimizer that runs sequentially with a possibility assessment algorithm.

EVTOL Tilt-Wing Aircraft Design under Uncertainty Using a Multidisciplinary Possibilistic Approach

“…The speed and stability of this method were also assessed by running the optimization procedure through 100 starting values. It was found to, on average, have an error below 10 4 %, and require less time than the double loop methods [43].…”

“…Validation of the implemented framework was completed previously [43]. Accordingly, the following nonlinear single-discipline PBDO test example was solved with various methods [51,52]:…”

“…For further validation of the MDO methodology, the following multi-discipline problem was solved and compared with different methods [43,53].…”

“…In a series of previous investigations, this tool was demonstrated to be capable of modelling the characteristics of small aircraft with acceptable precision [39][40][41][42][43]. In these cases, the modelled aircraft were all using conventional configurations, a requirement imposed by the semi-empirical methods which underpin many of MAPLA's analyses.…”

Stick-free Flight Stability Problem Revisited: A Modeling and Simulation Approach

“…Karpuk et al presented a design methodology, and the stick-free phenomenon is used in solely creating a CG envelope by considering neutral points [23]. Rostami et al proposed a probabilistic approach for the design of the empennage of the propeller-driven light aircraft, but without considering stick-free characteristics of the aircraft [24]. Silva et al studied multi-disciplinary design optimization of the general aviation aircraft, but at the elevator sizing stage, the stick-free condition is kept out of concern [25].…”