A Convergence Study for a Longitudinal Maneuver by Using Various Tools

This work aims to understand whether the magnitude and time of occurrence of the absolute maximum and maximum oscillatory main rotor blade loads that is achieved in a nonlinear response analysis can be obtained by using a trim method. The latter does not require any controller and it requires less engineering effort and computational time than the former. The comparisons have been made for a pull-up maneuver of a conventional fictitious rotorcraft. Both trim and nonlinear response analyses have been performed by using two different tools, Flightlab® and Dymore®. Flightlab modelled a utility helicopter with rigid blades while Dymore modelled the elastic properties of the main rotor to calculate the detailed loads information on the rotor components by using the maneuver response obtained from Flightlab. After comparing the Dymore results, it has been concluded that the trim analysis is able to approximate the nonlinear response analysis for a cyclic pull-up maneuver for static, low-cycle, and high-cycle fatigue analyses of the blades. However, if higher accuracy is required, then nonlinear response analysis should be performed. After comparing the Flightlab results, it has been observed that one can perform nonlinear response analysis only on the critical flight condition(s) and helicopter configuration(s) chosen based on the blade loads obtained from the trim method.