Analysis of Structural Flexibility Effects on Handling Qualities Using Variable Stability Simulations

In recent years, economic and sustainability requirements have guided aircraft design toward high-aspect-ratio wings and lighter materials. These modifications have introduced more pronounced coupling between aeroelasticity and flight dynamics, leading to challenges concerning handling qualities. Current techniques for analyzing handling qualities, such as the Cooper–Harper and pilot-induced oscillation (PIO) rating scales, often rely on flowchart-based assessments susceptible to pilot bias. To address this issue, we propose maintaining the use of these rating scales while performing predefined tasks. We also suggest correlating the energy content of the input command power spectral density (PSD) with the respective Cooper–Harper and PIO ratings. The study uses the identified model of the SB-10 sailplane from the German Space Center (DLR), implemented in the Flight Test Simulator (FTS) of the Brazilian Air Force’s Institute of Research and Flight Test (IPEV). The analysis highlights a deterioration in handling qualities due to the increment of the number of structural modes explicitly modeled, emphasizing the importance of considering aeroelastic characteristics in the aircraft design phases before flight test campaigns. The findings suggest the necessity of advanced simulation tools that incorporate these factors to predict, assess, and mitigate handling quality deficiencies effectively during earlier phases of aircraft design.