Monolithic internal balance for scaled helicopter wind tunnel force measurements

Abstract This paper presents the design, manufacture, and calibration of a novel monolithic six-component internal balance developed by the National Institute for Aerospace Technology (INTA). Engineered specifically to address the spatial constraints of a 1:100 scale helicopter model, this instrument overcomes the challenges of measuring aerodynamic loads in highly restricted volumes. The study details the complete development of the aluminum-based monolithic structure, including electrical integration and rigorous calibration procedures. The resulting system is capable of resolving three forces (thrust, drag, and side force) and three moments (roll, pitch, and yaw). Finally, a verification process demonstrates the balance’s operational performance, showing measurement deviations generally below 5% of Full Scale (FS), with specific torque scenarios remaining within approximately 10% FS.