# How do the two Zero-Lift AOA compare to each other?

Concentrate for this exercise on the Cl/alpha (coefficient of lift vs angle of attack) plot. Start by de-cluttering the plot and leaving only the curve for the highest Reynolds-number (Re) selected (i.e. remove all checkmarks, except the second to last, and press the “Update plots” tab).

3. From the plot, find the CLmax for your airfoil (Tip: for a numerical breakdown of the plotted curve, you can select the “Details” link and directly read the highest CL value and associated AOA in the table – first two columns):

4. Find the Stall AOA of your airfoil (i.e. the AOA associated with CLmax in 6.):

5. Find the CL value for an AOA of 5° for your selected airfoil:

6. Find the Zero-Lift AOA for your airfoil (again, the numerical table values can be used to more precisely interpolate Zero-Lift AOA, i.e. the AOA value for which CL in the second column becomes exactly 0):

7. Compare your researched airfoil plot to the given NACA 4412 plot in Fig. 4.4. of your text book.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; a) How do the two CLmax compare to each other? Describe the differences in airfoil &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; characteristics (i.e. camber & thickness) between your airfoil and the given NACA 4412, &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; and how those differences affect CLmax. (Use your knowledge about airfoil designation &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; together with the airfoil drawings in the on-line tool to make conclusions about &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; characteristics.) &nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; b) How do the two Stall AOA compare to each other? Explain how the differences in &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; airfoil characteristics (i.e. camber & thickness) between your airfoil and the given NACA &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4412 affect Stall AOA.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; c) How do the two Zero-Lift AOA compare to each other? Evaluate how the differences in &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; airfoil characteristics between your airfoil and the given NACA 4412 affect Zero-Lift AOA.

8. Compare your researched airfoil plot to the given NACA 0012 plot in Fig. 4.4. of your text book.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; a) How do the two Zero-Lift AOA compare to each other? Evaluate how the differences in &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; airfoil characteristics between your airfoil and the given NACA 0012 affect Zero-Lift AOA.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; b) What is special about the design characteristics of NACA 0012? How and where could &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; this airfoil design type be utilized on your selected aircraft? Describe possible additional &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; uses of such airfoil in aviation.

For the second part of this assignment use your knowledge of the atmosphere and the Density Ratio, (sigma), together with Table 2.1 and the Lift Equation, Equation 4.1, in your textbook (remember that the presented equation already contains a conversion factor, the 295, and speeds should be directly entered in knots; results for lift will be in lbs):

L = CL * &nbsp;* S * V2 / 295