A GENERAL-THEORY OF ROTORCRAFT TRIM

In this paper we offer a general theory of rotorcraft trim. The theory is set in the context of control theory. It allows for completely arb itrary trim controls and trim settings for multi-rotor aircraft with t ests to ensure that a system is trimmable. In addition, the theory all ows for ''optimal trim'' in which some variable is minimized or maximi zed rather than set to a specified value. The theory shows that sequen tial trim cannot work for free flight. The theory is not tied to any p articular trim algorithm; but, in this paper, it is exercised with per iodic shooting to show how free-flying rotorcraft can be trimmed in a variety of ways (zero yaw, zero pitch, zero roll, minimum power, etc.) by use of the general theory. The paper also discusses applications t o harmonic balance and auto-pilot trim techniques.