Stability Assessment of a Propeller-Wing Wind Tunnel Model Based on Analysis Using Measured Structural Data and Online-Monitoring

As part of the German research project “BNF: Buergernahes Flugzeug” , a wind tunnel model mainly for aerodynamic and acoustic investigation was designed and constructed. During the design stage, dynamic stability of the complete model was analyzed based on the data provided by the simulations (structural model, aerodynamic model). In this work, methods for the aeroelastic assessment and analysis of the constructed wind tunnel model based on measured structural data and online-monitoring will be presented. To determine the structural data experimentally, a Ground Vibration Test (GVT) for the whole model (propeller, electric motor and wing) was performed. The measurements from the GVT were used to provide the structural data needed for the flutter analysis with ZAERO (comprehensive code for flutter analysis). For the flutter analysis using ZAERO, propeller aerodynamic and gyroscopic effects of the rotating propeller were added to the flutter model. In general, the test of the model components (motor, propeller) and experimental assessment of the aeroelastic behavior of the wind tunnel model were performed in three steps: 1.Test of the motor and propeller suspended on a constructed test frame 2.Aeroelastic assessment of the propeller-wing model with rotating propeller, outside the wind tunnel 3.Aeroelastic assessment of the propeller-wing model with rotating propeller, inside the wind tunnel and with wind For the aeroelastic assessment of the model during these three test steps an online-monitoring procedure was defined and performed based on a predefined measurement technique. Finally, the results of the flutter analysis and experimental aeroelastic assessment of the wind tunnel model were used to define the global aeroelastic boundaries of the wind tunnel measurement program. Aerodynamic investigation of the model within a wide range of different parameters (for example angle of attack, propeller settings) was a main part of the wind tunnel measurements. In order to prevent/monitor any kind of unforeseen, aerodynamically induced excitations of the model or instabilities, online-monitoring of the model during all the wind tunnel measurements was deemed to be necessary. Here, besides introducing the methods of the aeroelastic assessment of the wind tunnel model, some aeroelastically related results of the wind tunnel measurements are presented and discussed.