Wing Twist

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  Wing twist is of two types named as geometric twist and aerodynamic twist:- Geometric Twist Different angles of attack at wing root and tip. Wash in Tip chord has a higher angle of attack than that of root chord. Wash out Angle of attack at tip is lower than that at wing root. It is useful in reducing tip vortices. Aerodynamic Twist Difference between zero-lift lines of airfoils at wing root and near the tip. Airfoils at root and near the tip have different zero lift angles of attack.

How to calculate Mean Aerodynamic Chord?



Mean Aerodynamic Chord 

The distance between leading and trailing edge of the wing, measured parallel to the normal airflow over the wing, is known as the chord. If the leading edge and trailing edge of the wing are parallel then, chord is constant along the span. Most commercial or fighter aircrafts have swept or delta wings in which chord length is greater at the root than at the tip. Consequently, chord changes along the span of the wing. The average length of Chord is known as Mean Aerodynamic Chord. 

It has a geometrical importance as CG should be located at certain point of the MAC in percentage of its length. So, the location of MAC is specific and it can be found out as:

Locating MAC

Measure the root and tip chord and draw following points on plane :

  • At the root of the wing, draw a line parallel to the fuselage centerline extending forward from leading edge and rearward from the trailing edge. Both lines should be the length of tip chord.
  • Do the same thing at the tip but drawing the lines, the length of root chord.
  • Connect the ends of the lines so that they make an 'X' over the wing panel, where the two lines intersect is the spanwise location of the mean aerodynamic chord. 


Calculating MAC

The following formula will give the measurement of the Mean Aerodynamic Chord:


where, Ct = tip chord
              Cr = root chord      












 

Comments

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