Aerofoil Terminology

Question 1

What is the purpose of the fuselage?

Answer 1

Purpose is to carry:

1. Passengers and freight (load).
2. Crew in the cockpit/flight deck.
3. Flight controls and instruments.
4. System equipment, avionics etc

Question 2

What type of construction is the CT4B’s fuselage?

a) monocoque
b) semi-monocoque
c) cantilever
d) Breaden

Answer 2

b)

Question 3

What is the basic purpose and other purposes of the wing?

Answer 3

Basic purpose: to produce lift. Also: 1. Fuel in integral tanks; 2. Lateral controls (ailerons); 3. Lift augmentation devices (flaps); 4. Under wing external stores; 5. Wing mounted engines

Question 4

What type of stability does the tail plane provide?

Answer 4

Longitudinal Stability

Question 5

What type of stability does the fin provide?

Answer 5

Directional Stability

Question 6

What are the primary flight controls?

Answer 6

Elevator; Ailerons; Rudder

Question 7

What are the secondary flight controls?

Answer 7

Trim tabs:

Elevator trim tab; rudder trim tab; aileron trim tab

Question 8

Define the term aerofoil.

Answer 8

1. Aerofoil is the cross-sectional shape of the wing;

2. It is specifically designed to produce the lifting forces necessary for flight;

Question 9

Define the chord line.

Answer 9

Chord line - the imaginary straight line joining the leading and trailing edges of an aerofoil.

Question 10

Define the chord of a wing.

Answer 10

Chord - Is the distance between the LE and TE of an aerofoil. It is given in feet or metres and can vary from root to tip in a tapered wing.

Question 11

Define the mean Camber Line.

Answer 11

Mean camber line - the imaginary line from LE to TE remaining equidistant between the upper and lower surfaces of the aerofoil.

Question 12

Define the Camber of an aerofoil.

Answer 12

Camber of an aerofoil is a measure of its curvature. It is measured as the maximum distance between the mean camber line and the chord line.

Question 13

Define the Thickness of an aerofoil.

Answer 13

Thickness is the maximum distance (measured perpendicular to the chord line) between the upper surface and lower surface of the aerofoil.

Question 14

Define the Thickness:Chord ratio.

Answer 14

The ratio of the thickness of an aerofoil to the chord of an aerofoil.

• Expressed as a % of Chord; and
• Position of maximum thickness expressed as a % of chord from the leading edge.

Question 15

Define the Leading Edge Radius.

Answer 15

The radius of curvature of a given leading edge shape.

• Sharp (small radius) for thin high speed aerofoils
• Blunt (large radius) for thick low speed aerofoils.

*Normally expressed as a % of chord.

Question 16

The line equidistant from upper and lower surface is termed as:

a) Camber
b) Chord Line
c) Chord
d) Mean Camber Line

Answer 16

d) *Mean camber line - the imaginary line from LE to TE remaining equidistant between the upper and lower surfaces of the aerofoil.

Question 17

Define the wing span.

Answer 17

The distance between the wingtips, measured in feet or metres.

Question 18

Define Wing Area. What is the equation for a rectangular wing?

Answer 18

The area of the wing projected on a plane perpendicular to the aircraft’s normal axis (plan view area).
S = b x c

Question 19

What is the equation for Aspect Ratio? What does this tell us?

Answer 19

AR = Span^2 / Area = (b^2)/ S

This ratio tells us how thin (chord) and long (span) the wings are or how thick (chord) and short (span) they are.

Question 20

What is the equation for Aspect Ratio of a RECTANGULAR wing?

Answer 20

AR = b/c = span/chord

Question 21

Do gliders have:

a) Low aspect ratio wings;
b) Medium aspect ratio wings; or
c) High aspect ratio wings.

Answer 21

c) Gliders have high aspect ratio wings (long and thin).

Question 22

Assuming a rectangular wing, find:

a) Wing Area, given span = 20 and chord = 4;
b) Aspect Ratio, given span = 20 and chord = 4;
c) Span and Wing Area, given AR = 10 and chord = 2;
d) Chord and AR, given wing area = 80 and span 20

Answer 22

a) 80
b) 5
c) 20 & 40
d) 4 & 5

*Just an example from Raj’s notes

Question 23

Define Wing Loading. What is the equation for it?

Answer 23

A measure of the gross weight supported by each unit area of the wings during straight and level flight.

Wing Loading (w) = Aircraft Weight (W) / Area of the wings (S)

Question 24

Define Load Factor. What is the equation for Load Factor (n)?

Answer 24

The ratio of lift generated by the wing over the aircraft’s weight (W) is termed the Load Factor (n)

n = Lift Produced (L) / Aircraft Weight (W)

Question 25

What is a typical load factor (n) during:

a) Straight and Level flight;
b) In a turn;
c) In a steep (60 AoB) turn;
d) Aerobatics (CT4 Loop);
e) Inverted flight.

Answer 25

a) n = 1 (1G)
b) n = >1 (>1G)
c) n = 2 (2G)
d) n = ~ 4 (approx 4G)
e) n = -1 (-1G)

Question 26

Define Relative Airflow.

Answer 26

The relative motion between an aircraft and the remote airflow (airflow far enough away from the aircraft and not disturbed by its presence).

Question 27

Define Angle of Attack (AoA).

Answer 27

Angle between the chord line and the relative airflow.

Question 28

What is the Total Reaction (TR) for an aerofoil and what are its two components?

Answer 28

TR is the resultant aerodynamic force acting on an aerofoil.

It is composed of the two ‘non-existant’ forces Lift & Drag

Question 29

Define Centre of Pressure (CP)

Answer 29

CP is the point on the chord line where the TR is considered to act.

Question 30

Lift is:

a) Perpendicular to the Relative Air Flow; or
b) Parallel.

Answer 30

a)

Question 31

Drag is:

a) Perpendicular to the Relative Air Flow; or
b) Parallel.

Answer 31

b)

Question 32

The Lift/Drag ratio is also known as?

Answer 32

The efficiency factor of an aerofoil.

Question 33

Define the Angle of Incidence (WING).

Answer 33

The angle between the Longitudinal axis and chord line. It is a fixed angle that does not change once the aircraft has been constructed.

Question 34

What is ‘Wash out’?

Answer 34

It is a decrease in incidence from root to tip.

Question 35

What is ‘Wash in’?

Answer 35

It is a increase in incidence from root to tip?

Question 36

Why is Wash Out good?

Answer 36

It increases LATERAL stability and allows greater aileron control during the stall (as the inboard part of the wing will stall first).

Question 37

Define Pitch Angle (Attitude).

Answer 37

The angle between the longitudinal axis and the horizontal plane.

Question 38

What is Dihedral and what is its purpose?

Answer 38

Dihedral is the upward inclination of the wing in relation to the lateral axis. It increases lateral stability.

Question 39

What is Anhedral and what is its purpose?

Answer 39

Anhedral is the downward inclination of the wing in relation to the lateral axis, generally used as a design feature to reduce excessive lateral stability caused by swept wing, high wing designs (i.e C-17)