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Everywhere I look I'm only able to find information about airfoils.

How do I find out the location of the Aerodynamic centre of an arbitrary aircraft irrespective of its type or shape?

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  • $\begingroup$ Do you mean center of lift perhaps? Or center of gravity? There can't really be an aerodynamic center because aerodynamics is a reference to flow not force. $\endgroup$ – Jay Carr Jun 13 '14 at 14:08
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    $\begingroup$ @JayCarr From Wikipedia: "The aerodynamic center is the point at which the pitching moment coefficient for the airfoil does not vary with lift coefficient (i.e. angle of attack), so this choice makes analysis simpler." I personally had never heard of the term and was surprised to find so much on it when I Googled "aerodynamic center." Live and learn, or maybe in my case live, learn, forget, learn again? $\endgroup$ – Terry Jun 13 '14 at 15:25
  • $\begingroup$ @Terry or! Or I could be wrong! lol, not the first time, probably not the last. I should have just google it like you, this is what I get for being lazy ;). $\endgroup$ – Jay Carr Jun 13 '14 at 17:30
  • $\begingroup$ @Gaurang are you talking about how you could find it for an arbitrary aircraft or a specific aircraft like the Boeing 737? $\endgroup$ – HardcoreBro Jun 14 '14 at 1:15
  • $\begingroup$ Yes.A method for any arbitrary aircraft irrespective of its type or shape. $\endgroup$ – Gaurang Gatlewar Jun 14 '14 at 4:52
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What you refer to as the aerodynamic centre is also called the neutral point, the point where pitch moments do not change at all angles of attack with attached airflow.

If you ask for an unswept body of high aspect ratio, the answer would be easy: At the quarter chord point in subsonic flow and at the half chord point in supersonic flow. Unfortunately, the neutral point shifts forward with decreasing aspect ratio until it sits right at the leading point (not edge) of a slender body, a body with infinitesimally small aspect ratio. It shifts slightly backwards with positive sweep, so you normally have to calculate correction factors which depend on

  • Sweep angle
  • Taper ratio
  • Ratio of fuselage width and span
  • Lengthwise position of the wing-fuselage intersection
  • High wing or low wing configuration (negligible influence)

If you don't have good wind tunnel data or a validated CFD model, you would use a collection of formulas and diagrams like DATCOM (see this link for a computerized version) to approximate a solution. Sorry, but I cannot give you a simple formula which would work out of the box.

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