Exercise 4: Drag and Applications
Part 1: Drag
Weight (W) 15,000 lb CDP 0.021
Wing Area (S) 230 ft2 CLmax at Stall 1.5
Aspect Ratio (AR) 5.3 Note: Assume the drag polar is a parabola
Span Efficiency (e) 0.85
Temperature Standard
Altitude Sea Level
Complete the following table for this particular typical transport jet. Start the table at stall speed, VS. Then answer the questions at the end using the values from the table. You can use an excel spreadsheet to create the answers for the table.
|
V (KTAS) |
q (psf) |
CL |
CD |
CL / CD |
DP (lb) |
DI (lb) |
DT (lb) |
|
VS |
|
|
|
|
|
|
|
|
120 |
|
|
|
|
|
|
|
|
140 |
|
|
|
|
|
|
|
|
160 |
|
|
|
|
|
|
|
|
180 |
|
|
|
|
|
|
|
|
190 |
|
|
|
|
|
|
|
|
200 |
|
|
|
|
|
|
|
|
220 |
|
|
|
|
|
|
|
|
240 |
|
|
|
|
|
|
|
|
260 |
|
|
|
|
|
|
|
Equations for Table:
q = CL = CDi =[1/ (πeAR)] CL 2
CD = CDP + CDi CD = CDP + [1/ (e AR)] CL 2 Dp = CDp q S
Di = CDi q S = [1/ (e AR)] CL2 q S Dt = Di + Dp = CD q S
1. Determine VSTALL (Stall speed in KTAS)
2. Determine DMIN (Minimum total drag in pounds)
3. Determine VDMIN (Speed in KTAS at minimum drag)
4. Determine the parasitic drag at DMIN (pounds)
5. Determine the induced drag at DMIN (pounds)
6. Find Glide Ratio at VDMIN
Part 2: Applications of Lift and Drag
Givens (Questions 7-11):
Weight (W) = 15,000 lb
Wing Area (S) = 230 ft2
Altitude = Sea Level
Temperature Standard
(The Given Figure below is not exactly the same aircraft as above, but close)
Figure 1.13 from Aerodynamics for Naval Aviators (1965).
7. What is the Angle of Attack at Stall for the aircraft in Figure 1.13?
8. What is the airspeed associated with initial onset of stall? (KEAS)
9. If the gross weight is increased by 10%, how would the stall speed change?
10. What Angle of Attack is associated with Best L/D?
11. What would be the best Glide Ratio for this aircraft?
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