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.

9.18.4 ACDp Estimation

Table 9.14 gives the Bizjet ACDp taken from Figure 9.8.

9.18.5 Induced Drag

The formula used for induced drag is Cm = Cl2/(3.14 x 7.5) = CL/23.55.

The Bizjet induced drag is given in Table 9.15.

9.18.6 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.

9.13 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 ACDp estimation

Cl

0.1

0.2

0.3

0.4

0.5

0.6

0.7

ACdp

0.00070

0.00030

0.00006

0

0.00060

0.00200

0.00400

Cl

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Cm

0.00170

0.00382

0.00680

0.01060

0.01530

0.02060

0.02720

in the civil aircraft drag estimation method. To avoid repetition, only the drag polar and other drag details of the AJT are shown in Figure 9.15. The drag polar at Mach 0.7 and at Mach 0.8 is tabulated in Table 9.17 and plotted in Figure 9.16.

To demonstrate the proper supersonic drag estimation method, a North Amer­ican RA-C5 Vigilante aircraft, shown in Figure 9.16, is used as an example here. Reference [3] provides the Vigilante drag polar for comparison. The subsonic drag estimation of a Vigilante aircraft follows the same procedure as in the civil aircraft example. Therefore, the results of drag at Mach 0.6 (i. e., no compressibility) and at Mach 0.9 (i. e., at Mcrit) are worked out briefly and tabulated. The supersonic drag estimation is worked out in detail using the empirical methodology described in [3].

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