Basic Aerodynamic Theory

Question 1

The prevailing pressure at any point in the atmosphere is called ……………….pressure.

Answer 1

The prevailing pressure at any point in the atmosphere is called STATIC pressure.

Question 2

When moving air is brought completely to rest, an additional pressure called ……………….pressure is imposed.

Answer 2

When moving air is brought completely to rest, an additional pressure called DYNAMIC pressure is imposed.

Question 3

The atmospheric conditions existing well ahead of a moving body and as yet unaffected by its passage, are denoted by the term ……………….

Answer 3

The atmospheric conditions existing well ahead of a moving body and as yet unaffected by its passage, are denoted by the term FREESTREAM.

Question 4

The term 1/2pV2 stands for ……………….pressure, where p = ……………….and V = ……………….

Answer 4

The term 1/2pV2 stands for DYNAMIC pressure, where p = DENSITY and V = VELOCITY (TAS).

Question 5

Pitot (or total) pressure = ……………….pressure + ……………….pressure.

Answer 5

Pitot (or total) pressure = STATIC pressure + DYNAMIC pressure.

Question 6

The airspeed indicator is simply a pressure gauge that measures ……………….pressure, but is calibrated to read in ……………….

Answer 6

The airspeed indicator is simply a pressure gauge that measures DYNAMIC pressure, but is calibrated to read in KNOTS.

Question 7

Equivalent airspeed (EAS) is the exact measure of dynamic pressure (1/2pV2). In flight below about
250 kt, for practical purposes EAS can be taken to be the same as ..................., given that instrument, position and compressibility errors are usually small in that speed range.

Answer 7

Equivalent airspeed (EAS) is the exact measure of dynamic pressure (1/2pV2). In flight below about
250 kt, for practical purposes EAS can be taken to be the same as IAS, given that instrument, position and compressibility errors are usually small in that speed range.

Question 8

All aerodynamic forces are proportional to EAS and therefore to ……………….in low-subsonic speed
flight.

Answer 8

All aerodynamic forces are proportional to EAS and therefore to IAS in low-subsonic speed
flight.

Question 9

The wings and tail section of an aircraft that are designed produce useful aerodynamic forces, are called ……………….

Answer 9

The wings and tail section of an aircraft that are designed to produce useful aerodynamic forces, are called AEROFOILS.

Question 10

Draw a typical cambered general-purpose aerofoil section and annotate the trailing and leading edges, chord line, line of mean camber, and point of maximum thickness.

Answer 10

Refer to Fig 3-6.

Question 11

The relative airflow (RAF) vector (is/is not) equal and opposite to the aircraft’s flight path vector at any given moment.

Answer 11

The relative airflow (RAF) vector IS equal and opposite to the aircraft’s flight path vector at any given moment.

Question 12

Sketch a cambered aerofoil and show the relationship between the chord line, RAF and the angle of attack.

Answer 12

Refer to Fig 3-7.

Question 13

When applied to an airflow around an aerofoil shape, Bernoulli’s Theorem can be reduced to dynamic energy + static pressure = a ……………….

Answer 13

When applied to an airflow around an aerofoil shape, Bernoulli’s Theorem can be reduced to dynamic energy + static pressure = a CONSTANT.

Question 14

In accordance with Bernoulli’s Theorem:

a) Wherever the speed of an airflow is increased, static pressure will be (increased/decreased).
b) Wherever the speed of an airflow is decreased, static pressure will be (increased/decreased).

Answer 14

In accordance with Bernoulli’s Theorem:

a) Wherever the speed of an airflow is increased, static pressure will be DECREASED.
b) Wherever the speed of an airflow is decreased, static pressure will be INCREASED.

Question 15

A steady flow of air around a body, where successive particles of air follow the same smooth path, is called ……………….flow.

Answer 15

A steady flow of air around a body, where successive particles of air follow the same smooth path, is called STREAMLINED flow.

Question 16

A disturbed, unpredictable flow with eddying is called ……………….flow.

Answer 16

A disturbed, unpredictable flow with eddying is called TURBULENT (OR SEPARATED) flow.

Question 17

Sketch the different areas of pressure that will exist around a typical cambered general-purpose aerofoil, placed in an airflow:

a) At a low angle of attack (about 4 degrees).
b) At a moderately high angle of attack (about 12 degrees).

Answer 17

Refer to Fig 3-11 a, b and c.

Question 18

The point on the leading edge at which the flow around an aerofoil is brought completely to rest is called the ……………….point.

Answer 18

The point on the leading edge at which the flow around an aerofoil is brought completely to rest is called the STAGNATION point.

Question 19

At an angle of attack of about 16 degrees, the streamline flow around an aerofoil breaks down and separates from most of the upper surface. This angle is called the ……………….or ……………….angle.

Answer 19

At an angle of attack of about 16 degrees, the streamline flow around an aerofoil breaks down and separates from most of the upper surface. This angle is called the CRITICAL or STALLING angle.

Question 20

To produce lift, downwash must ……………….upwash.

Answer 20

To produce lift, downwash must EXCEED upwash.

Question 21

The resultant of all the aerodynamic forces acting on an aerofoil is called the ……………….(TR). It acts through a point within the aerofoil called the ……………….of ……………….

Answer 21

The resultant of all the aerodynamic forces acting on an aerofoil is called the TOTAL REACTION (TR). It acts through a point within the aerofoil called the CENTRE of PRESSURE.

Question 22

On a cambered aerofoil, the centre of pressure (CP) moves (forward/rearward) as angle of attack is increased until, passing the stalling angle, it moves more rapidly (forward/rearward).

Answer 22

On a cambered aerofoil, the centre of pressure (CP) moves FORWARD as angle of attack is increased until, passing the stalling angle, it moves more rapidly REARWARD.

Question 23

Over the normal operating range of speeds and angle of attack, the centre of pressure (CP) of a symmetrical aerofoil has (little if any/a lot of) movement.

Answer 23

Over the normal operating range of speeds and angle of attack, the centre of pressure (CP) of a symmetrical aerofoil has LITTLE IF ANY movement.

Question 24

The component of the TR:

a) That is perpendicular to the relative airflow (RAF) is called ……………….
b) That is parallel to the relative airflow (RAF) is called ……………….

Answer 24

The component of the TR:

a) That is perpendicular to the relative airflow (RAF) is called LIFT.
b) That is parallel to the relative airflow (RAF) is called DRAG.