The non-technical beginner (and others) who want to understand what makes the airplane fly is often faced with too much complicated jargon. This article is non-technical, mathematics-free and, hopefully, easily understood owing to the use of familiar analogies. What is stability? It can be defined as a state of happiness. When things get bad, there is a longing for the good old days. On the other hand, instability can be characterized by "anything would be better than the way things are now." Putting this into physical terms, if we are on the playground swing we can comfortably swing ourselves with no problem. When we stop all effort, we return to a rest position which is exactly as it was when we started. Stability. Now suppose we are sitting in a chair and lean back on the two rear legs with the aid of an assistant. When the assistant steps away, we find that we cannot maintain this position for very long despite our best efforts. The two-legged chair position is unstable. If a stable airplane is disturbed by a gust or an inadvertent control input, it will return to the regular flight condition existing (more or less) before the disturbance with only little or no further pilot input. We say the airplane flies itself. When a beginner gets in trouble with a trainer-type airplane, often the best thing to do is nothing. Hands off! Interestingly, this often also applies when piloting the hottest full-scale jet fighters.
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