Rotor / Airframe Harmony

Part 3

By Greg Gremminger

The airframe and rotor both have inertia with forces and moments acting on them to cause movements against that inertia. All such physical systems with inertia and forces and moments, will have a natural frequency of oscillation. This means they may tend to oscillate in reaction to a disturbance - turbulence or pilot input. If the system is DYNAMICALLY stable, the oscillatory response to a transient will cause the transient to diminish or decay back to steady state. If the system is dynamically unstable, the oscillations will increase in amplitude - divergent. The goal of any control system, including an aircraft, is to be "damped" to such a degree that the oscillations quickly decay to zero.

When two or more components of a system, each having their own natural frequencies of oscillation and inertia, act on each other (as a rotor and airframe will do), the way these frequencies act together can be either "harmonious" or non- harmonious. (Think of the different strings on a guitar!). In a control system such as a gyroplane, the goal is to harmonize the natural reactions of these components so that they tend to act to reduce the effect of each other DYNAMICALLY. This means for instance that the inertial reaction of the rotor does not "feed" or resonate with the oscillations of the airframe so as to worsen or excite worse oscillations in the airframe, and vice-versa. The Magni rotor and rotor system is designed to act DYNAMICALLY in harmony with the airframe inertia and control system. In actuality, this is the major reason the Magni stands out in stability feel among all other gyros. Magni has achieved this result through careful and professional aeroDYNAMIC design, and lots of trial and error design iteration and flight testing.