Exercise 4: Drag and Applications
The first part of this week’s assignment is to revisit our reciprocating engine powered (i.e. propeller type) aircraft from last week.
1. Selected Aircraft (from last week’s module):
Aero Commander 720 Shrike
Make sure to review your data and results from last week and any feedback that you may have received on your work, in order to prevent continuing with faulty data.
2. Main Wing Airfoil type & on-line database designator (from last week’s module):
3. Aircraft Maximum Gross Weight [lbs] (from last week’s module): 6750 lbs
4. Wing Span [ft] (from last week’s module): 49 ft 1 in = 49 ft
5. Average Chord Length [ft] (from last week’s module): 5.2 ft
6. Wing Area ‘S’ [ft2] (from last week’s module): 255 ft^2
7. Find the Aspect Ratio ‘AR’ for your selected aircraft wing. (Use the wing span and average chord length from last week’s module/from above. See also page 63 in your textbook.):
Span = 49 ft , average chord = 5.2 ft
AR = span/average chord = 49 / 5.2 = 9.42
8. CLmax for your airfoil (from last week’s module): CLmax = 1.5413 AOA = 15.75
9. Standard sea level Stall Speed ‘Vs’ for your aircraft [kts] (from last week’s calculation):
L = W = 6750 lbs Cl Max =1.5413 , =1 S =255 ft^2
V^2 = 295 * 6750 / 1.5413/ 255
V = 71.18 KTAS
Find the appropriate drag polar curve for your airfoil selection (2. above; from last week’s module). You can utilize any officially published airfoil diagram for your selected airfoil or use again the Airfoil Tool at http://airfoiltools.com/search .
Concentrate for this exercise on the Cl/Cd (coefficient of lift vs coefficient of drag) plot, i.e. the so called drag polar. Use again 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).
10. From the polar plot, find the CDmin value for your airfoil, i.e. the lowest value ...