Principles of Flight

Question 1

How does a wing generate lift?

Answer 1

Air over the wing gets accelerated and has a lower pressure. Air under the wing gets decelerated and has a higher pressure. This difference in pressure is what causes the lift.

Question 2

What is ‘relative airflow’?

Answer 2

The movement of the glider through the air causes the air to flow past the glider in the opposite direction.

Question 3

What is the angle of attack?

Answer 3

The angle at which the airflow arrives.

Question 4

What is the chord of the wing?

Answer 4

A straight line from the leading edge to the trailing edge.

Question 5

The direction of the lift force produced is at what angle to the relative airflow?

Answer 5

Right angle

Question 6

When is total drag at a minimum?

Answer 6

When lift dependent drag is equal to zero lift drag.

Question 7

What will be the reading on the ASI if the Dynamic source of the ASI is blocked?

Answer 7

It will not respond

Question 8

What two quantities must be present for a glider to spin?

Answer 8

High AoA and yaw.

Question 9

What is meant by the aspect ratio of a wing.

Answer 9

Ratio of wing length to chord length.

Question 10

What is the purpose of the gliders fin?

Answer 10

To provide directional stability.

Question 11

On a silver duration flight, soarable conditions stop after four and a half hours. You are at 5000 ft. What is the best speed to fly in order to complete the flight?

Answer 11

Minimum sink.

Question 12

While maintaining the normal gliding attitude you notice that the air speed indicator is reading low and erratic. What is the most likely cause?

Answer 12

Water in the pitot system.

Question 13

Wash out’ is a term used to describe a particular design feature of a glider. What does it describe?

Answer 13

A twist in the wing, such that the inboard part of the wing stalls before the outboard, hence preventing wing drop at the stall.

Question 14

What is the approximate distribution of production of lift on a glider wing?

Answer 14

70 percent from above
30 percent from below

Question 15

What happens to induced drag as airspeed is increased from the stall towards Vne?

Answer 15

Induced drag reduces inversely as the square of the IAS.

Question 16

Three forces act on a glider in flight. Which force, or part of a force, causes a glider to turn?

Answer 16

Part of total lift acting in the direction of the turn.

Question 17

If the 1 ‘g’ stalling speed is 34 knots, what will be the stalling speed in a steep turn with the accelerometer reading 4 ‘g’?

Answer 17

68kts

Question 18

What is the importance of indicated airspeed (IAS) and true airspeed (TAS), when flying at altitude?

Answer 18

IAS is always less than TAS and the ASI under reads the true airspeed.

Question 19

What is the aerodynamic purpose of the gliders tailplane?

Answer 19

Provide longitudinal stability

Question 20

What is the definition of a Mean Camber line?

Answer 20

A line joining the centres of curvature between the Leading and
Trailing edges and equidistant from the upper and lower surfaces.

Question 21

What happens to profile drag as airspeed is increased from the stall towards Vne?

Answer 21

Profile drag increases approximately as the square of the IAS.

Question 22

In which direction does lift developed by the wing of an aircraft in flight act?

Answer 22

Perpendicular to chord line.

Question 23

What does the Barometric Pressure Scale enable the pilot to achieve?

Answer 23

To reset the altimeter datum.

Question 24

Why is the capacity flask insulated?

Answer 24

To prevent temperature changes affecting the variometer readings.

Question 25

What causes adverse yaw or aileron drag?

Answer 25

An increase in lift dependent drag on the up going wing.

Question 26

What is the purpose of a gliders dihedral?

Answer 26

To help increase lateral stability

Question 27

What does stagnation point refer to?

Answer 27

The point on a wing leading edge where air is brought to rest.

Question 28

What is the definition of Centre of Pressure?

Answer 28

The point on the chord line through which the force if lift acts

Question 29

As angle of attack increases, what direction will the Centre of pressure move?

Answer 29

Forward until the stalling angle, then rapidly back.

Question 30

The Pitot source is blocked on the Altimeter. What will the instrument read?

Answer 30

Fail to operate