Distributed Electric Propulsion (DEP) enables novel aero-propulsive interactions by exploiting propeller slipstream effects to modify the aerodynamic characteristics of lifting surfaces. Several numerical and wind-tunnel investigations have demonstrated the potential of distributed blowing for improving lift capability and aerodynamic efficiency in DEP aircraft configurations. However, experimental flight-test evidence at the full-aircraft scale remains limited. This work presents an experimental investigation of the trimmed aerodynamic characteristics of a DEP flying demonstrator, with specific focus on the impact of propeller-induced blowing on lift, drag, and overall aerodynamic efficiency.
The study is based on flight-test data collected during multiple automated maneuvers and processed through a dedicated identification framework that reconstructs aerodynamic coefficients from locally identified stability and control models. Trimmed lift and drag coefficients are evaluated for each maneuver and used to build CL–α, CD–α and trimmed aerodynamic polar CL–CD relationships. The dataset is clustered according to the propeller advance ratio at trim, adopted as a proxy for the intensity of distributed blowing, and second-order analytical fits are employed to highlight global trends across the explored operating conditions.
The results show a clear and consistent influence of distributed blowing on the aerodynamic characteristics of the aircraft. Increasing blowing intensity produces an upward shift and a steeper slope of the lift curve, a mild reduction in trimmed drag, and a noticeable improvement of the trimmed aerodynamic polar. These combined effects lead to a significant increase in aerodynamic efficiency over the investigated flight envelope.
Despite the inherent scatter of experimental flight data, the observed trends are robust and consistent with physical expectations and previous numerical findings. The present work provides original flight-test evidence of the aerodynamic benefits of distributed propulsion at the aircraft level and supports the potential of DEP configurations for low-speed and high-lift flight conditions.
