Archives: Theory Courses

12.6.4(c) chord;

12.6.4(c) . chord;

The length of a straight line joining the leading and trailing edges (Image)

12.6.4(b) trailing edge;

12.6.4(b) . trailing edge;

The edge at the downstream side (image)

Introduction Section 12.6

Describe what an aerofoil is and distinguish between different aerofoil designs.

(12.6.2)
Various designs include:
General Purpose
High lift
Pre-1916
High Speed (image)

Define:
(12.6.4)

(a) leading edge;
edge facing into the airstream

(b) trailing edge;
edge facing rearwards

(c) chord;
length of the chord line

(d) chord line;
A straight line joining the leading and trailing edges.

(e) thickness;
The depth of the aerofoil

(f) camber.
Is the curvature of an aerofoil surface

Explain Bernoulli’s Theorem in simple terms.

(12.6.8)
In the streamline flow of an ideal fluid
the sum of the
energy of position
plus the energy of motion
plus the pressure energy
will remain constant

Describe streamline airflow around an aerofoil.

(12.6.10)

Explain the changes which occur to dynamic and static pressure wherever the speed of the airflow is:
(12.6.12)

(a) increased;
increased the dynamic energy of motion
dynamic pressure Increase
static pressure Decrease
total constant to equal the Same

(b) decreased.
Decreased the dynamic energy of motion
dynamic pressure Decrease
static pressure Increase
total constant to equal the Same

With the aid of diagrams, explain:
(12.6.14)

(a) venturi effect;

(b) the pressure distribution around an aerofoil which is producing lift.

Define the terms:
(12.6.16)

(a) total reaction (TR);
Adding up a total of the pressures distributed all over an aerofoil.

(b) centre of pressure (CP).
is the point in the aerofoil which the total reaction (TR) is acting through.

Describe how TR and CP change with increasing angle of attack for a lifting aerofoil.

(12.6.18)

Show how movement of the CP varies between symmetrical and non-symmetrical aerofoils.

(12.6.20)

Define the Lift and Drag components of Total Reaction.

(12.6.22)

With respect to lift:
(12.6.24)

(a) State the lift formula;

(b) summarise the factors affecting lift. (i.e. angle of attack, aerofoil shape, IAS)

Identify the primary factors determining the coefficient of lift (CL) for an aerofoil.

(12.6.26)

Describe a typical CL versus angle of attack curve (graph).

(12.6.28)

On a typical CL versus angle of attack curve, identify the critical stalling angle.

(12.6.30)

State the precaution against flying with ice, frost, snow or other contamination of the aerofoil surfaces.

(12.6.32)

Distinguish between induced drag, parasite and profile drag.

(12.6.34)

List the elements of profile drag.

(12.6.36)

State the factors affecting parasite drag, and profile (form and skin friction) drag.

(12.6.38)

Explain how induced drag varies depending on:
(12.6.40)

(a) angle of attack of the aerofoil;

(b) aspect ratio.

Identify curves of parasite, profile, induced and total drag versus aerofoil airspeed.

(12.6.42)

Describe a typical curve of lift/drag (L/D) ratio versus angle of attack for a symmetrical aerofoil.

(12.6.44)

Identify the approximate angle for best L/D ratio.

(12.6.46)

12.6.4 Define (Aerofoil)

12.6.4. Define:





Aerofoil



Term
Description







(a) . leading edge;




 


Aerofoil - Edges
The edge facing into the airstream ( Image)














(b) . trailing edge;










 


The edge at the downstream side (image) 







(c) . chord; 







AreoFoil - Chord Line
The length of a straight line joining the leading and

        trailing edges (Image)







(d) . chord line




; 


A straight line joining the leading and trailing edges.














(e) . thickness;










The depth of the aerofoil 


On most aerofoils the point of maximum thickness is forward towards the leading edge 







(f) . camber. 




Aerofoil - Camber


Is the curvature of an aerofoil surface.


The curvature of a line drawn equidistant between the upper and lower surfaces of the aerofoil is the mean camber of the aerofoil.
(image) 

12.6.2 Describe what an aerofoil is and distinguish between different aerofoil designs.

12.6.2. Describe what an aerofoil is and distinguish between different aerofoil designs.

The wings and tail sections of an aircarft are aerofoils

Various designs include:
General Purpose
High lift
Pre-1916
High Speed (image)

12.4.16 State the approximate temperature lapse rate up to the tropopause.

12.4.16. State the approximate temperature lapse rate up to the tropopause.

The ISA temperature lapse rate up to the Troposhere is 1.98degC per 1000ft.

12.4.14 State the ISA sea level pressure and temperature conditions.

12.4.14. State the ISA sea level pressure and temperature conditions.

ISA Sealevel pressure = 1013.2hPa
ISA Sealevel temperature = +15deg C

12.4.12 Explain the basis for the International Standard Atmosphere (ISA).Sub Topic Syllabus Item






ISA



12.4.12. Explain the basis for the 
International Standard Atmosphere (ISA) 

- hypothetical set of atmospheric conditions which represents an average of the conditions experience worldwide

Sea level pressure = 1013.2hPa (hectopascals)
Sea level temperature +15 degrees C
Sea level density 1.225kg/m3 

Lapse rates 		






12.4.14. State the ISA sea level pressure 
and temperature conditions.


ISA Sealevel pressure = 1013.2hPa


ISA Sealevel temperature = +15deg C





12.4.16. State the approximate temperature lapse rate

up to the tropopause.		


The ISA temperature lapse rate up to the Troposhere is 1.98degC per 1000ft. 























12.4.12. Explain the basis for the International Standard Atmosphere (ISA).Sub Topic Syllabus Item 



– hypothetical set of atmospheric conditions which represents an average of the conditions experience worldwide


Sea level pressure = 1013.2hPa (hectopascals)
Sea level temperature +15 degrees C
Sea level density 1.225kg/m3 


Lapse rates

12.4.10 Describe how pressure, temperature and density normally vary within the atmosphere.

12.4.10. Describe how pressure, temperature and density normally vary within the atmosphere.

The pressure, temperature and density will normally all decrease with increasing altitude
Pressure decreases rapidly at lower levels and more slowly at higher levels.
Temperature decreases at a constant rate up to the troposphere.
Density decreases rapidly at lower levels and more slowly at higher levels.
(image)

12.4.8 State the relationship between pressure/temperature and the density of an air mass.

12.4.8. State the relationship between pressure/temperature and the density of an air mass.

Pressure and temperature affect the density of any parcel of air.
High temperature and low pressure will result in low density.
Low temperature and high pressure will result in high density.