This set of Aircraft Design Multiple Choice Questions & Answers (MCQs) focuses on “Configuration Layout – Aerodynamic Considerations-1”.
1. Which of the following is correct?
a) Fuselage can affect aerodynamic efficiency
b) Fuselage cannot affect aerodynamic efficiency
c) Aerodynamic efficiency is not dependent on the fuselage at all
d) Aerodynamic efficiency will always be half if fuselage is long
Explanation: Fuselage is primary drag producing component. The overall smoothness and how fuselage is designed will affect the drag properties of the aircraft. As a result of which fuselage will affect the aerodynamic efficiency of the aircraft as well.
2. Poor wing fuselage will reduce lift loss.
Explanation: A poorly designed fuselage can lead to drag rise, flow separation etc. As a result of these adverse effects lift loss will increase. Fuselage is considered as one of the primary drags producing member in an aircraft. Hence, an adequate design should be provided to reduce the lift loss.
3. If an aircraft is not designed properly then __________
a) it can experience excessive flow separation
b) it will have more lift
c) it will have less drag
d) it will have higher aerodynamic efficiency
Explanation: Overall aircraft design will decide whether the aircraft is streamlined or not. An inadequate and poorly designed aircraft can suffer from drag increment, excessive flow separation etc.
4. ___________ can be considered as one of the most powerful aerodynamic consideration.
a) Wetted area
b) Number of spars
c) Number of ribs
d) Only wingspan
Explanation: Wetted area is considered as one of the most powerful aerodynamic tool. Wetted area is nothing but the actual area that will be in contact if fluid is flown over the body. Spar and ribs are structural members.
5. To reduce fuselage wetted area we can ___________
a) lower the fineness ratio
b) increase fineness ratio
c) always double the fineness ratio
d) always use long fuselage
Explanation: Wetted area can be used to determine the drag properties of an aircraft. Fineness ratio is nothing but the length of the fuselage divided by max diameter of the fuselage. Hence, if we lower the fineness ratio then the ratio of length to diameter will reduce which in turn reduces the wetted area.
6. Which of the following is incorrect?
a) Tightly packed fuselage will not affect maintainability
b) Waiting area can be minimized by lowering fineness ratio
c) Fineness ratio is division of length of fuselage to maximum diameter
d) Wetted area can affect the drag properties
Explanation: Tightly packed fuselage makes it difficult to access some vital components for maintenance. This will affect the maintainability of the aircraft. Wetted area can be reduced by tight packaging or by lowering the fineness ratio or by both.
7. Short and fat fuselage will have ___________
a) lower tail arm
b) higher tail arm
c) higher fineness ratio
d) higher wetted area
Explanation: Tail arm is nothing but the distance between cg of tail to cg of an aircraft, typically. Short and fat fuselage will have shorter tail arm or tail moment arm. Size of the fuselage will be reduced for such case and as a result of which the tail arm will be reduced.
8. What is the disadvantage of short and fat fuselage?
a) Higher supersonic wave drag
b) Higher incompressible wave drag
c) Lower supersonic wave drag
d) Lower wetted area
Explanation: Wave drag is the supersonic phenomena. Wave drag does not exist for incompressible flow. Short and fat fuselage will offer minimization of the wetted area. This gives advantage in terms of friction properties. However, it suffers from higher wave drag at supersonic speeds.
Explanation: Given, Free stream velocity V = 120knts. As shown in the figure fuselage has some deviation with free stream. For given speed of freestream air, a typical fuselage should be allowed up to 12.5° maximum. More than the given limit will affect the drag parameters. Hence, answer would be 10°-12°.
10. Determine the corrections or otherwise of the following assertion [A] and reason [R]:
Assertion [A]: Maintaining smooth longitudinal contour in fuselage will give better aerodynamic design.
Reason[R]: Longitudinal control lines are used to provide smoothness to the fuselage.
a) Both [A] and [R] are true and [R] is the correct reason for [A]
b) Both [A] and [R] are true but [R] is not the correct reason for [A]
c) Both [A] and [R] are false
d) [A] is false but [R] is true
Explanation: A good aerodynamic design of a fuselage will maintain smooth longitudinal contour to reduce the drag and other similar effects. This can be achieved by using longitudinal control lines. Smooth fuselage with lesser discontinuity will reduce the drag and as a result of which aerodynamic efficiency will improve. Hence, [A] and [R] both correct however, [R] is not correct reason.
Sanfoundry Global Education & Learning Series – Aircraft Design.
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