Summary of Parasite Drag

The wing reference area Sw = 700ft2, CDpmi„ = f/Sw. Table 9.20 summarizes the Vigilante parasite drag. As indicated in Section 9.16, [3] provides a correlated fac­tor of 1.284 to include all the so-called other effects. Therefore, the final flat-plate equivalent drag is faircraft = 1.284 x 8.87 = 11.39 ft2, 28.4% = 11.62ft2, to include military aircraft excrescence. This gives CDpmin at Mach 0.6 = 11.39/700 = 0.01627 ([3] uses 0.1645). This is the CDpmin at the flight Mach number before compressibil­ity effects begin to appear; that is, it is seen as the CDpmin at incompressible flow. At higher speeds, there is a CF shift to a lower value. The CDpmin estimation must be repeated with a lower CF at Mach 0.9 and Mach 2.0. To avoid repetition in account­ing for compressibility, a factor of 0.97 is used (i. e., a ratio of values at Mach 0.9 and Mach 0 in Figure 9.20b – a reduction of 3%) is taken at 0.9 Mach. A factor of 0.8 (i. e., a reduction of 20%) is taken at Mach 2.0, as shown in Table 9.16. At

the compressible flow, the wave drag is added. At supersonic speed, shock waves contribute to it.

To correlate with the methodology presented herein, the following values of ACDp were extracted from [3].