Relaxed Stability

In aviation, relaxed stability is the tendency of an aircraft to change its attitude and angle of bank of its own accord. An aircraft with relaxed stability will oscillate in simple harmonic motion around a particular attitude at an increasing amplitude.

This can be contrasted with the tendency of an aircraft with positive stability, which, when trimmed to fly at a certain attitude, will continue to do so in the absence of control input, and will oscillate in simple harmonic motion on a decreasing scale around the trimmed attitude, eventually returning to its trimmed attitude. A positively stable aircraft will also resist any bank movement. A Cessna 152 is an example of a stable aircraft. Similarly, an aircraft with neutral stability will not return to its trimmed setting without control input, but will oscillate in simple harmonic motion around the trimmed setting continuously and be susceptible to bank influences.

Read more about Relaxed Stability:  Early Aircraft, Methods of Decreasing Stability in Design, Unstable Aircraft, Vertical Wing Position, Advantages of Instability in Military Aircraft

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