Design of a Conceptual Rotorcraft Model Preparing Investigations of Sidestick Handling Qualities

Abstract

Fly-by-wire control systems offer a significant design freedom with respect to control laws and pilot inceptors. Especially, the use of ergonomically advantageous short-pole sidesticks combined with active inceptor technology is possible. So far, no requirements for the design of the force-displacement characteristics of sidestick inceptors can be found in the military rotorcraft handling qualities specification ADS-33E. As a basis to perform experiments in order to define appropriate criteria, a conceptual rotorcraft simulation model, called HELIFLY, is created. The simplest and still realistic model structure is chosen and configured to represent a cargo/utility type rotorcraft with {Level 1} handling qualities for the hover and low-speed flight regime according to the military handling qualities standard ADS-33. The modeled response types include rate command/attitude hold, attitude command/attitude hold and translational rate command. A vertical rate command height hold response type is implemented besides an unaugmented vertical control mode. A rate command/direction hold response type and a turn coordination mode are available in the directional axis. Handling qualities parameters of the model for its different response types are analytically derived. This allows a rapid and comprehensive analysis of the model dynamics in terms of handling qualities and a better understanding of the interdependencies between model and handling qualities parameters. It is shown that the ADS-33 requirements lead to unique values for the model parameters requiring only very few additional, but well justified assumptions. Preliminary piloted evaluations demonstrate the general agreement between predicted and assigned handling qualities.