The use of the Open-Loop Onset Point (OLOP) to predict rotorcraft pilot-induced oscillations

Abstract

The Open-Loop Onset Point (OLOP) criterion has, for many years, been successfully used as a method to predict quasi-nonlinear pilot-induced oscillations (PIOs) for fixed-wing aircraft. Only limited research has been conducted using the criterion for prediction of PIOs occurring in rotorcraft. This paper details a study to extend the application of OLOP to rotorcraft, using the combination of control inputs appropriate for the task and a suitable pilot model. Results are compared between pilot subjective opinion and OLOP predictions, from tests performed in a ground-based simulation facility. Using task specific application of OLOP, results obtained in the investigation are encouraging, whereby the objective predictions reflect subjective pilot assessment. From results obtained, a modified boundary is presented.