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Q1. With reference to aerofoil section terminology, which of the following statements are true? 1. The chord line is a line joining the centre of curvature of the leading edge to the centre of the trailing edge, equidistant from the top and bottom surface of the aerofoil. 2. The angle of incidence is the angle between the chord line and the horizontal datum of the aircraft. 3. The angle between the chord line and the relative airflow is called the aerodynamic incidence or angle of attack. 4. The thickness/chord ratio is the maximum thickness of the aerofoil as a percentage of the chord; the location of maximum thickness is measured as a percentage of the chord aft of the leading edge.
Ans: – C. 2, 3 and 4.
Q2. The definition of lift is:
Ans: – d. the aerodynamic force which acts at 90° to the relative airflow.
Q3. An aerofoil section is designed to produce lift resulting from a difference in the:
Ans: – C. higher air pressure below the surface and lower air pressure above the surface.
Q4. On an aerofoil section, the force of lift acts perpendicular to, and the force of drag acts parallel to the:
Ans: – a. flight path.
Q5. When the angle of attack of a symmetrical aerofoil is increased, the centre of pressure will:
Ans: – C. remain unaffected.
Q6. Why does increasing speed also increase lift?
Ans: – b. The increased speed of the air passing over an aerofoil’s upper surface decreases the static pressure, thus creating a greater pressure differential between the upper and lower surface.
Q7. The point on an aerofoil section through which lift acts is the:
Ans: – C. centre of pressure.
Q8. The angle between the chord line of the aerofoil section and the longitudinal axis of the aircraft is known as:
Ans: – b. the angle of incidence.
Q9. The angle between the chord line of an aerofoil section and the relative wind is known as the angle of:
Ans: – C. attack.
Q10. A line drawn from the leading edge to the trailing edge of an aerofoil section and equidistant at all points from the upper and lower contours is called the:
Ans: – C. mean camber line..
Q11. At zero angle of attack, the pressure along the upper surface of a symmetrical aerofoil section would be:
Ans: – C. less than atmospheric pressure.
Q12. The angle of attack of an aerofoil section directly controls:
Ans: – C. the distribution of positive and negative pressure acting on the section.
Q13. When the angle of attack of a positively cambered aerofoil is increased, the centre of pressure will:
Ans: – b. move forward along the chord line.
Q14. The term “angle of attack” is defined as the angle:
Ans: – b. between the section chord line and the relative wind.
Q15. Which of the following statements is true? 1. Relative airflow, free stream flow, relative wind and aircraft flight path are parallel. 2. Aircraft flight path, relative airflow, relative wind and free stream flow are parallel, but the aircraft flight path is opposite in direction. 3. The pressure, temperature and relative velocity of the free stream flow are unaffected by the presence of the aircraft. 4. The relative wind is produced by the aircraft moving through the air. 5. The direction of flight is parallel with and opposite to the relative airflow.
Ans: – d. 1, 2, 3, 4 and 5.
Q16. Which of the following statements are correct? 1. Maximum camber is the maximum distance between the top and bottom surface of an aerofoil section. 2. The thickness/chord ratio is expressed as a percentage of the chord. 3. It is easier for air to flow over a well-rounded leading edge radius than a sharp leading edge. 4. Two dimensional airflow assumes a wing with the same aerofoil section along its entire span, with no spanwise pressure differential. 5. Air flowing towards the lower pressure of the upper surface is called upwash.
Ans: – C. 2, 3, 4 and 5.
Q17. When considering an aerofoil section at a constant angle of attack, which of the following statements is true?
Ans: – a. If the static pressure on one side is reduced more than on the other side, a pressure differential will exist.
Q18. Considering an aerofoil section subject to a constant dynamic pressure, which of the following statements is correct?
Ans: – b. Up to about 16°, increasing the angle of attack will increase the pressure differential between the top and bottom surface of the aerofoil.
Q19. When considering the effect of changing angle of attack on the pitching moment of an aerofoil, which of the following statements is correct? 1. At ‘normal’ angles of attack the pitching moment is nose-up. 2. The pitching moment about the aerodynamic centre (AC) is constant at normal angles of attack. 3. The aerodynamic centre (AC) is located approximately at the 25% chord point. 4. The moment about the aerodynamic centre (AC) is a product of the distance between the aerodynamic centre (AC) and the centre of pressure (CP) and the magnitude of the lift force.
Ans: – d. 2, 3 and 4.
Q20. Ice contamination of the leading portion of the aerofoil has which of the following consequences? 1. The profile of the leading portion of the surface can be changed, preventing normal acceleration of the airflow and substantially reducing the magnitude of the lift force. 2. Form (pressure) drag will be increased because of the increased frontal area of the aerofoil section. 3. Loss of lift will have a greater effect than an increase in form (pressure) drag. 4. At ‘normal’ angles of attack lift can be lost entirely if enough ice accumulates.
Ans: – a. 1, 2, 3 and 4
