Stick-Free Flight Stability Problem Revisited: A Modeling and Simulation Approach

The stick-free flight stability is an old-fashioned and non-progressive issue; nevertheless, it is still existent and of significant importance to the design of aircraft whose control system is reversible. The existence of the problem necessitates a deep assessment of stick-free flight stability throughout the aircraft design. Up to now, this problem has been addressed using either analytical approaches, which are only related to the static stability evaluation, or performing flight tests. In this study, the problem is handled in its entirety, from static and dynamic flight stability assessment to design criteria with a comprehensive perspective. Moreover, it is also exhibited that, contrary to what has been generally proposed in the literature, the limitation of the problem of stick-free flight stability through static stability assessment is far from being the main challenge. As a brief scope, the derivation of the control surface dynamics, a stick-free trim algorithm, and assessment rationale of the stick-free static and dynamic flight stability using a simulation approach are proposed. As a consequence, the aim is to set a broad understanding for designers related to this phenomenon and add adjunct design criteria in the design optimization process by approaching it from a modeling, simulation, and flight test perspective.