Aircraft Design Questions and Answers – Aerodynamics – Parasite (Zero-Lift) Drag and Drag due to Lift

«
»

This set of Aircraft Design Question Bank focuses on “Aerodynamics – Parasite (Zero-Lift) Drag and Drag due to Lift”.

1. Which of the following is a method for estimating the potato drag?
a) Equivalent skin friction method
b) Mach number
c) Weight only
d) Conceptual design
View Answer

Answer: a
Explanation: Equivalent skin friction method is one of the typical method used to estimate parasite drag. Mach number is defined as the ratio of the speed of object to the speed of sound. Weight is force due to gravity.
advertisement

2. Equivalent skin friction coefficient can be used to provide initial estimation of the parasite drag.
a) True
b) False
View Answer

Answer: a
Explanation: Yes, it is true. Equivalent skin friction coefficient can be used to provide information about the initial estimation of parasite drag. In this method, we estimate the parasite drag based on equivalent skin friction coefficient and wetted area of the aircraft.

3. Equivalent skin friction coefficient may include ______________
a) skin friction and separation drag
b) only wave drag
c) only skin friction drag
d) only thrust loading
View Answer

Answer: a
Explanation: Equivalent skin friction coefficient includes both skin friction and separation drag. Wave drag is supersonic phenomenon. Wave drag occurs when aircraft is traveling with speeds greater than the speed of sound. Thrust loading is defined as the ratio of the thrust and weight.

4. To get initial estimation of the parasite drag, aircraft wetted area can be multiplied by _____
a) equivalent skin friction coefficient
b) weight
c) lift
d) wing span
View Answer

Answer: a
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.

5. 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.
a) 0.0032
b) 1.2
c) 4.2
d) 0.04
View Answer

Answer: a
Explanation: Parasite drag coefficient = equivalent skin friction coefficient*area ratio
= 0.004*0.8 = 0.0032.
advertisement

6. Consider equivalent skin friction coefficient as 0.0025 and Swet/Sref = 0.6. Evaluate parasite drag.
a) 0.0015
b) 02.34
c) 1.23
d) 0.000025
View Answer

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

7. 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.
a) 18.67 unit
b) 12 unit
c) 20 unit
d) 65 unit
View Answer

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

8. Determine the value of form factor for fuselage if fuselage fineness ratio f is 1.2.
a) 35.725
b) 12
c) 100
d) 423.2
View Answer

Answer: a
Explanation: Form factor = 1 + (60/f3) + (f/400)
= 1 + (60/1.23) + (1.2/400)
= 1+34.722+0.003 = 35.725.

9. Flat plate skin friction coefficient depends upon _____________
a) mach number only
b) reynolds number only
c) mach number, reynolds number etc
d) weight of the aircraft
View Answer

Answer: a
Explanation: Flat plate skin friction coefficient depends upon number of factors including Mach number, Reynolds number, type of flow etc. Mach number is used to provide information about speed of the object with respect to the speed of sound.
advertisement

10. Determine Flat plate skin friction coefficient if Reynolds number is 123500. Consider flow to be laminar.
a) 0.0038
b) 1.234
c) 0.045
d) 123500
View Answer

Answer: a
Explanation: Laminar flow flat plate skin friction coefficient = 1.328 / (Reynolds number0.5)
= 1.328 / (1235000.5) = 0.0038.

11. Which of the following is correct for nacelle form factor (FF)?
a) FF = 1+(0.35/f)
b) FF = 1*(0.35/f)
c) FF = 1-(0.35/f)
d) FF = 1/(0.35/f)
View Answer

Answer: a
Explanation: Form factor will be different for different components of an aircraft. For nacelle, form factor can be estimated as follows: Form factor FF = 1 + (0.35/f). Where, f = length/maximum diameter = fineness ratio.

Sanfoundry Global Education & Learning Series – Aircraft Design.

To practice Aircraft Design Question Bank, here is complete set of 1000+ Multiple Choice Questions and Answers.

advertisement

advertisement
advertisement
advertisement
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn