# Aerodynamics Questions and Answers – Airfoil Nomenclature

This set of Aerodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Airfoil Nomenclature”.

1. Who designed the nomenclature of airfoil?
a) NACA series
b) EULAR series
c) EPPLER series
d) CLARK series

Explanation: The nomenclature of airfoil is designed by the NACA series. The shape of the NACA airfoil is described using a series of digits following the word NACA. The NACA identified different airfoils shape with a logical numbering system, such as symmetric airfoil and cambered airfoil.

2. Purpose of camber in an airfoil is ____________
a) to increase maximum drag
b) to increase maximum lift
c) to decrease maximum lift
d) to decrease maximum drag

Explanation: The main purpose of camber is to increase the maximum lift in an airfoil. The maximum lift coefficient can get by increasing the camber in an airfoil. Some recent design use negative camber. That airfoil is called the supercritical airfoil. This type of airfoil is used in the supersonic flight and to produce a higher lift to drag ratio.

3. Is shape of the airfoil depends on thickness?
a) True
b) False

Explanation: The shape of the airfoil depends on the thickness of the airfoil. The thickness of an airfoil varies along the chord. The thickness is measured perpendicular to the chord line. In NACA series the last two digits indicate the percentage of thickness.

4. What is a chord?
a) Distance between leading edge and chord
b) Distance between chord and chamber
c) Distance between leading edge and trailing edge
d) Distance between trailing edge and chord

Explanation: Distance between leading edge and the trailing edge is called chord. Chord refers to the imaginary straight line joining the leading edge and trailing edge of an airfoil. The chord length is the distance between the trailing edge and the point on the leading edge, where the chord intersects the leading edge.

5. Purpose of leading edge is to ______________
a) allow the wing to operate at high angle of attack
b) allow the wing to operate at low angle of attack
c) allow the wing to operate at stall condition
d) allow the wing to operate in level condition

Explanation: Leading edge is a part of the airfoil. Leading edge allows the wing to operate at a high angle of attack. Slats are placed at the leading edge. These are aerodynamic surfaces on the leading edge of the wing. These are high lift devices used for short takeoff.
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6. What is the purpose of trailing edge?
a) Airflow rejoins
b) Airflow separated
c) Vortex are created
d) Stalling will created

Explanation: Trailing edge is a part of airfoil. Trailing edge of an aerodynamic surface such as awing is its rear edge. Where the airflow will separate at the leading edge and rejoins at the trailing edge. Ailerons are placed at the trailing edge of the wing and rudder, elevator is placed at the trailing edge of tail.

7. What is the shape of the airfoil at the leading edge?
a) Semi-circular
b) Curve
c) Straight
d) Circular

Explanation: The shape of the airfoil at the leading edge is usually circular with a leading edge radius of approximately 0.02c. The shape of all standard NACA airfoils are generated by specifying the shape of the mean chamber line and then wrapping specified symmetric thickness distribution around the mean camber line.

8. What is the thickness in NACA 2412 airfoil?
a) 12%
b) 24%
c) 41%
d) 2%

Explanation: The NACA 2412 airfoil has a maximum camber of 2% located at 40% from the leading edge with a maximum thickness of 12%. It was the first 4-digit NACA series and it was developed in 1930’s because of the 12% thickness the shape of the airfoil is symmetric.

9. What parameter is used to decrease the stall speed?
a) Chord
b) Chord line
c) Camber
d) Camber line

Explanation: Camber is generally used to increase the maximum lift coefficient. Which in turn it decreases the stall speed of the aircraft. Due to decrease in the stall there will be an increase in the lift. In supercritical airfoil. There will be a highly cambered curve after section which used in supersonic flight for their maximum lift.

10. What is the thickness in NACA 747A315 airfoil?
a) 15%
b) 25%
c) 30%
d) 7%

Explanation: In NACA 747A315 airfoil. The 7 denotes the series, 4 provides the location of minimum pressure on the upper surface in a tenth of chord, 7 provides the location of the minimum pressure on the lower surface in tenth of chord, the 4th character i.e. A indicates the thickness distribution and mean line form used. Again 5th digit 3 indicates the design lift coefficient in the tenth and the final two digits indicate the thickness of the chord 15%.

11. Why NACA 0012 airfoil is said to be symmetric airfoil?
a) Because of no camber
b) Because of camber
c) Because of no thickness
d) Because of chord line

Explanation: The NACA 0012 airfoil indicates the symmetric airfoil, because an airfoil with no camber, that is with the camber line and chord line co-incident in an airfoil is called a symmetric airfoil. For the NACA 0012 airfoil is with a maximum thickness of 12%.

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