Impact of Airframe-Propulsion System Modeling Strategies on Key Structural Performance Metrics

Whole-aircraft coupled aerodynamics, flight dynamics, and structural dynamics models are commonly employed during the aircraft design process, generally increasing in fidelity, and associatively accuracy, as the design matures. While literature acknowledges the impact of explicitly representing the propulsion system in such models, it does not address the impact of structural idealizations on key metrics that inform early conceptual design. This paper investigates the impact of a range of propulsion system structural modeling strategies and their attendant idealizations on the accuracy with which key structural performance metrics may be acquired. A conventional tube-and-wing airframe with under-wing-mounted, high-bypass-ratio, turbofan propulsion systems is employed as a verification case. The lowest-fidelity modeling strategies defined herein are capable of acquiring airframe loads and vertical power plant center-of-mass inertial loads within +/- 2%. Higher-fidelity, predominantly 2D strategies are necessary for acquisition of propulsion system displacements, deformations, and power plant swing frequency within +/- 10% of a global finite element model. However, sufficient data must be available to allow the construction of higher-fidelity strategies during early design stages.