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Aircraft Drag

 

Table 9.17. AJT total aircraft drag coefficient, CD

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CL

0.1

0.2

0.3

0.4

0.5

0.6

 

 

CDpmin

 

 

 

 

 

0.02120

 

 

CDp

0.0007

0.0003

0

0.00050

0.0014

0.0026

 

 

CDi = CL2 /(3.14 × 5.3)

0.0006

0.0024

0.0054

0.00961

0.0150

0.0216

 

 

Total aircraft CD @ 0.7 M

0.0226

0.0239

0.0266

0.03140

0.0376

0.0454

 

 

Wave drag, CDw

0.0016

0.0018

0.0020

0.00271

0.0033

0.0056

 

 

Total aircraft CD @ 0.8 M

0.0242

0.0257

0.0286

0.03411

0.0409

0.0510

 

 

 

 

 

 

 

 

 

 

H-tail

SH = 6.063 m2 (65.3 ft2)

span = 9.85 m (32.3 ft)

MAC = (9.73 ft)

t/c = 4%

Nacelle/pylon (the engine is buried in the fuselage – no nacelle pylon)

aircraft cruise performance, where the basic drag polar must be computed

drag estimated at cruise altitude = 36,152 ft

Mach number = 0.6 (has compressibility drag)

ambient pressure = 391.68 lb/ft2

Re/ft = 1.381 × 106

design CL = 0.365

design Mach number = 0.896 (Mcrit is at 0.9)

maximum Mach number = 2.0

9.19.2 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)

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