**Exercise 4: Drag and Applications **

**Part 1: Drag**

## Givens (Questions 1 – 6):

Weight (W) 15,000 lb C_{DP} 0.021

Wing Area (S) 230 ft^{2} C_{Lmax} 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, V_{S}. 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) |
C_{L} |
C_{D} |
C_{L} / C_{D} |
D_{P}
(lb) |
D_{I}
(lb) |
D_{T}
(lb) |

V_{S} |
|||||||

120 | |||||||

140 | |||||||

160 | |||||||

180 | |||||||

190 | |||||||

200 | |||||||

220 | |||||||

240 | |||||||

260 |

Equations for Table:

q = C_{L} = C_{Di} =[1/ (?eAR)] C_{L} ^{2}

C_{D} = C_{DP} + C_{Di} C_{D} = C_{DP} + [1/ ( e AR)] C_{L} ^{2} Dp = C_{Dp}q S

Di = C_{Di} q S = [1/ ( e AR)] C_{L}^{2} q S Dt = Di + Dp = C_{D} q S

1. Determine V_{STALL} (Stall speed in KTAS)

2. Determine D_{MIN }(Minimum total drag in pounds)

3. Determine V_{DMIN} (Speed in KTAS at minimum drag)

4. Determine the parasitic drag at D_{MIN} (pounds)

5. Determine the induced drag at D_{MIN} (pounds)

6. Find Glide Ratio at V_{DMIN}

**Part 2: Applications of Lift and Drag**

**Givens (Questions 7-11):**

Weight (W) = 15,000 lb

Wing Area (S) = 230 ft^{2}

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?