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Exercise4: Drag and Applications

Part 1: Drag Givens (Questions 1 – 6):

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)] CL2

CD = CDP + CDi CD = CDP + [1/ ( e AR)] CL2 Dp = CDpq S

Di = CDi q S = [1/ ( e AR)] CL2q 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?

Use Code; GET20