To get initial estimation of the parasite drag, aircraft wetted area can be multiplied by _____

lift

weight

wing span

equivalent skin friction coefficient

Correct Answer : equivalent skin friction coefficient

Explanation : Initial estimation of parasite drag can be obtained by multiplying equivalent skin friction coefficient with wetted area of aircraft. Lift and weight will be in opposite direction to each other. Wing span is a typically length of the aircraft.

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Find the approximate value of wetted area Swet for given reference area of Sref=20 unit and parasite drag coefficient of 0.0028. Consider equivalent skin friction coefficient Cf as 0.003.

12 unit

18.67 unit

20 unit

65 unit

Correct Answer : Option (B) : 18.67 unit

Explaination : Wetted area Swet = Parasite drag coefficient*Sref/Cf
= 0.0028*20/0.003 = 18.67 unit.

Consider equivalent skin friction coefficient as 0.0025 and Swet/Sref = 0.6. Evaluate parasite drag.

02.34

1.23

0.0015

0.000025

Correct Answer : Option (C) : 0.0015

Explanation : Parasite drag = equivalent skin friction coefficient*(Swet/Sref)
= 0.0025*0.6 = 0.0015.

Determine the initial estimation of parasite drag coefficient if, equivalent skin friction coefficient is 0.004 and ratio of wetted area to the reference area is 0.8.

0.0032

0.04

1.2

4.2

Correct Answer : Option (A) : 0.0032

Explaination : Parasite drag coefficient = equivalent skin friction coefficient*area ratio
= 0.004*0.8 = 0.0032.