Aerodynamic Forces: Drag and Stall

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Independent Project: Drag

For the speeds in the first column, start with your aircraft's stall speed, then continue in intervals of 20 or less knots (consider increasing the detail in the important portions near (L/D)max - see also this module's tutorial videos within the  3.2 Lectures and Tutorials ), and continue to at least a speed of 300kts or higher if required to allow for answering the questions and explaining all drag phenomena.

To create this table you can use the Excel Spreadsheet ASCI 309 Table Drag Table (XLSX) located under “Field and Presentation Resources”.

V (KTAS)	q (psf)	CL	CDP	CDI	CD	CL / CD	DP (lb)	DI (lb)	DT (lb)
VS
60
80
100
120
140
160
180
200
220
240
260
280
300

To fill out your table and subsequently create a diagram with the total drag curve, you will need to research a variety of variables, formulas, and components. Again, the emphasis in this project task is on explaining your methodology as if you attempted to instruct someone unfamiliar with the aerodynamic details and relationships. Therefore, make sure to detail all assumptions, all formulas used, and all steps that were taken. The following will give you some starting points for your search and consideration. 

1. Assumptions and conditions:

· Assumed atmospheric conditions

· Calculated dynamic pressure (second column; based on the assumed atmospheric conditions and KTAS)

2. Necessary aircraft information:

· Wing size and configuration (e.g., AR & efficiency factor - if you can't find an efficiency factor for your aircraft, you can make an assumption [i.e., pick a value] somewhere between 0.75 and 0.85)

· Weight (should, of course, fall between MTOW and empty weight of your aircraft)

· Airfoil information (e.g., CLmax from last module & CDP - if you can't find the CDP for your entire aircraft, you can utilize the minimum drag for your airfoil and add a value of 0.02, which will account for the parasite drag of your aircraft's fuselage) or if you are still having trouble, just use a Cdp of .021 which is a common Cdp.

3. Required formula (for inputs see the formula summary )

4. Resources and Inputs page)

· Dynamic pressure

· Lift equation (two forms: one solved for stall speed and the other solved for required CL)

· Drag coefficients (CDi & CD)

· Application of coefficients to find actual forces (Dp, Di, Dt)

· Possibly wing geometry conversions (e.g., wingspan and area into AR or wingspan and average chord into AR)

5. Do not forget to create the diagram.

Once created, utilize your derived table and diagram data to answer the following associated questions:

A. What are the minimum drag parameters for your aircraft?

· Minimum drag value  D(min)

· Speed  VD(min)  at which minimum drag occurs

· Relationship between  Dp  and  Di  at  D(min)  

B. What are the maximum lift to drag ratio  CL/CD  parameters for your aircraft?

· (CL/CD)max  value

· Speed at which  (CL/CD)max  occurs

C. Compare answers in A. and B. and comment on the findings.

D. Explain which of your derived values will allow glide performance predictions for your aircraft and quantify best glide conditions with specific values.

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