Effect of Torsional Flexibility on an Unmanned Helicopter Performance Including Compressibility Effect

Abstract

In this study, torsional deformation of an unmanned helicopter and its effect on the performance characteris-tics are examined. In the analyses, blade-element momentum theory is used for the calculation of the aero-dynamic loads by implementing compressibility corrections. For the interactions between the aerodynamic loads and torsional deformations, an iterative solution procedure is developed. To obtain the trim points of the helicopter, a trim code is written in which blade is modeled as either rigid or elastic in the torsional direc-tion. It is found that there occur some differences between the rigid and elastic blade in terms of the control inputs. However, since the aerodynamic center is close to the shear center of the reference blade, the differ-ence is found to be negligible small. Therefore, effects of the torsional deformations on the helicopter control and performance are minimal.