Computation of Wetted Areas, Re, and Basic CF

The aircraft is first dissected into isolated components to obtain the Re, wetted area, and basic 2D flat-plate CF of each component, as listed herein. There is no correc­tion factor for CF at Mach 0.6 (i. e., no compressibility drag). The CF compressibility correction factor (computed from Figure 9.19b) at Mach 0.9 and at Mach 2.0 is applied at a later stage.

Figure 9.16. North American RA-C5 Vigilante aircraft (no pylon shown)

Fuselage

• fuselage wetted area = Awf = 1,474 ft2

• fuselage Re = 69 x 1.381 x 106 = 9.53 x 107 (length trimmed to what is perti­nent for Re)

• use Figure 9.19b to obtain basic CFf = 0.0021 Wing

• wing wetted area = Aww = 1,144.08 ft2

• wing Re = 15.19 x 1.381 x 106 = 2.1 x 107

• use Figure 9.19b to obtain basic CFw = 0.00257

Empennage (same procedure as for the wing)

• V-tail wetted area = AwVT = 235.33 ft2

• V-tail Re = 8.35 x 1.381 x 106 = 1.2 x 107

• use Figure 9.19b to obtain basic CF_V-tail = 0.00277

• H-tail wetted area = Awht =

• H-tail Re = 9.73 x 1.381 x 106 = 1.344 x 107

• use Figure 9.19b to obtain basic CFh-tail = 0.002705

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