Aerofoil Terminology

Question 1

The most forward point on the aerofoil is called?

Answer 1

The leading edge

Question 2

The most rearward point on the aerofoil is called?

Answer 2

The trailing edge.

Question 3

The top side on the aerofoil is called?

Answer 3

The upper surface

Question 4

The bottom side on the aerofoil is called?

Answer 4

Lower surface

Question 5

What is Relative Airflow?

Answer 5

Air in a region where pressure, temperature and relative velocity are unaffected by the passage of the aircraft through it, is known as the Relative Airflow (RAF).

Question 6

What is Effective relative Airflow?

Answer 6

the actual path the airflow takes due to the influence of the object, the aerofoil or aircraft, moving through the air is called Effective Relative Airflow. This is because air is a fluid and incompressible at low speeds.

Question 7

What is Lift?

Answer 7

Lift is the component of the Total Reaction that is perpendicular (90°) to the flight path or Relative Airflow (RAF).

Question 8

What is Drag?

Answer 8

Drag is the component of the Total Reaction that is in the same direction and parallel to the relative airflow (RAF). This is also the same as saying opposite and parallel to the direction of flight.

Question 9

What is Total Reaction?

Answer 9

The resultant of all the aerodynamic forces acting on the wing or aerofoil section.

Question 10

What is the Chord line?

Answer 10

It is a straight line drawn from the leading edge to the trailing edge of the aerofoil.

Question 11

What is the measurement of Chord line?

Answer 11

Chord

Question 12

What does Equidistant mean?

Answer 12

A equal distance.

Question 13

What does camber mean?

Answer 13

Camber is defined as the convexity of the curve of an aerofoil from the leading edge to the trailing edge

Question 14

What is the average mean camber line?

Answer 14

The average mean camber line is a line joining the leading and trailing edges of an aerofoil, which is equidistant from the upper and lower surfaces and will show the average camber.`

Question 15

When the Camber Line lies above the chord line, the aerofoil has which type of Camber?

Answer 15

A positive camber

Question 16

What is the maximum Camber?

Answer 16

The point where there is the maximum distance between the Mean Camber Line and the Chord Line.

Question 17

What is the Maximum thickness of an aerofoil?

Answer 17

It is the depth of the aerofoil.

Question 18

How is the Maximum thickness for a aerofoil expressed ? With an example.

Answer 18

d as a ratio of thickness to chord length. For example an aerofoil with a thickness/chord ratio of 1:10 would have a thickness one tenth of the chord length and this can also be expressed as a 10% aerofoil. Therefore a 1:20 would be a 5% aerofoil.

Question 19

What is Centre of Pressure?

Answer 19

he Centre of Pressure (CP) is the point, usually on the Chord Line, through which the Total Reaction (TR) may be considered to act.

Question 20

What is a tapered wing?

Answer 20

A wing planform in which the chord of the wing changes continuously from the center of the wing to the wing tip. In addition, this may be accompanied by a taper in the depth of the airfoil. A tapered wing has advantages from structural and aerodynamic points of view.

Question 21

What is Centre of gravity (CG)?

Answer 21

The Centre of Gravity (CG) is the point within the aircraft through which the weight can be said to act. It is very important that the CG is in the correct position so that the aircraft is balanced at that point otherwise the aircraft may be unstable and will be difficult to control.

Question 22

What is the Angle of Attack (α)?

Answer 22

Angle Of Attack (α)

The angle between the Chord Line and the flight path or Relative Airflow (RAF) is known as the Angle of Attack (α).

Question 23

What is a Aspect ratio (AR) ?

Answer 23

Aspect ratio is the relationship between the length and width of a wing. There are two methods that can be used to calculate the Aspect Ratio.

Question 24

Which Aspect Ratio(AR) method is used to calculate the AR of a tapered or elliptical wing?

Answer 24

AR= wing span^2
————-
Wing area
Therefore, the AR is calculated by dividing the wingspan squared by the wing area.

Question 25

Which Aspect Ratio(AR) method is used to calculate the AR of a simple rectangle wing?

Answer 25

AR= Wingspan
————-
Chord
Therefore, the AR is calculated by dividing the Wingspan by the Chord.

Question 26

What does a high aspect ratio indicate and give an example.

Answer 26

A high aspect ratio indicates long, narrow wings.

Eg. Gliders

Question 27

What does a low aspect ratio indicate? Give an example.

Answer 27

A low aspect ratio indicates short, wide wings. e.g fighter aircraft