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9.19 Coursework Example: Subsonic Military Aircraft

 

299

Table 9.13. Bizjet parasite drag buildup summary and CDpmin estimation

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Wetted

 

 

 

 

 

 

 

area, Aw ft2

Basic CF

CF

Total CF

f – ft2

CDpmin

Fuselage + U/C fairing

670

0.00220

0.000906

0.003106

2.080

0.006440

 

Canopy

 

 

 

 

0.100

0.000310

 

Wing

552.3

0.00300

0.000780

0.003784

2.090

0.006470

V-tail

81

0.00300

0.000786

0.003786

0.302

0.000950

H-tail

132.2

0.00320

0.000800

0.004000

0.529

0.001640

2 × nacelle

2 × 79

0.00290

0.002414

0.005314

0.840

0.002600

 

2 × pylon

2 × 28.35

0.00295

0.000767

0.003720

0.210

0.000650

 

Rough (3%)

Eq. 9.27

 

 

 

0.182

0.000560

 

Air-conditioning

 

 

 

 

0.100

0.000310

 

Aerial, lights

 

 

 

 

0.050

0.000155

 

Trim drag

 

 

 

 

0.130

0.000400

 

Total

 

 

 

 

6.610

0.020500

 

 

 

 

 

 

 

 

 

9.18.4 Summary of Parasite Drag

Table 9.13 provides an aircraft parasite drag buildup summary in tabular format. The surface roughness effect of the 3% increase (see Equation 9.27) in f is added in the table for all surfaces. The wing reference area Sw = 323 ft2; the CDpmin = f/Sw ; ISA day; 40,000-ft altitude; and Mach 0.65.

9.18.5 CDp Estimation

Table 9.14 gives the Bizjet CDp taken from Figure 9.8.

9.18.6 Induced Drag

The formula used for induced drag is CDi = CL2/(3.14 × 7.5) = CL2 /23.55. The Bizjet induced drag is given in Table 9.15.

9.18.7 Total Aircraft Drag at LRC

The drag polar at LRC is summarized in Table 9.16. The drag polar at HSC (Mach 0.74) requires the addition of wave drag from Figure 9.8b. (As discussed in Section 9.7.1, the CDpmin at only LRC is sufficient.) This drag polar is plotted in Figure 9.2. The CL2 versus the CD is plotted in Figure 9.14; the nonlinearity at low and high CLis of interest.

9.19 Coursework Example: Subsonic Military Aircraft

The coursework example of military aircraft was conducted for the subsonic AJT/CAS-type aircraft of the class BAe Hawk, which uses the same procedure as

Table 9.14. Bizjet CDp estimation

C L

0.1

0.2

0.3

0.4

0.5

0.6

0.7

CDp

0.00070

0.00030

0.00006

0

0.00060

0.00200

0.00400

 

 

 

 

 

 

 

 

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