- #1

greg_rack

Gold Member

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- 68

when dealing with longitudinal stability calculations of an aircraft/airfoil we are considering all aerodynamic forces relevant to the generation of moment around the c.g.(lift) as acting at a point we call aerodynamic centre which is, by definition, a point where the pitching moment of the wing stays constant with varying angle of attack.

Even though I'm not convinced of how such a point could exit, I might be okay with the definition and trust the professor who says this point just "exists"... but how can we approximate lift as acting there, when we know in reality it acts at the center of pressure? I know that the cp varies with varying angle of attack, so considering lift acting there would be a pain and involve integration and so on, so I'm wondering if maybe it is maybe just an approximation for small angle of attacks, since the cp is usually close to the ac for such values? Because, if not, how wouldn't this affect our moment calculations?