a small replica of an early flying wing desigh has an area o

a small replica of an early flying wing desigh has an area of 450 sq ft and a NACA 6321 airfoil. if the aspect ratio is 6. fid

a) at what angle of attack must the airplane fly to develop a lift of 6000 lb at 200 mph under standard sea level condition.

b) how much drag will the wing develop.

c) if the airplane is flying at an altitude of 12,000 ft what angle of attack is required?

Given,

Wing area, S = 450 sq ft

Noting that, Weight (W) = Lift = 6000 lb

V = 200mph = 293.333 ft/sec

angle of attack = W/V = 6000/293.333 = 20.45

Aspect ratio = (wing span)²/ wing area

so, wing span = sqrt(wing area x aspect ratio) = sqrt( 450 x 6) = 51.96 ft

C_l = 6000 / (0.5 x 0.002377 x 293.333² x 450) = 0.1304

Assuming, e=0.85

C_d= 0.1304² / (3.142 x aspect ratio x e) = 0.017 / (3.142 x 6 x 0.85) = 0.0011

Drag developed by wing = C_d x (1/2) x (density) x V² x S = 0.0011 x (0.5) x (0.002377) x 293.333² x 450 = 50.62 lb