Lift

Question 1

Select the correct statements regarding the Coefficient of Lift (CL)

Select one or more:

a. It represents the lifting capability of the wing
b. It depends on condition of the wing
c. It is a multiplier
d. It is a number
e. It has no units
f. It varies with angle of attack
g. It depends on shape of the wing

Answer 1

The correct answers are: It has no units, It is a multiplier, It depends on shape of the wing, It depends on condition of the wing, It varies with angle of attack, It represents the lifting capability of the wing

Question 2

Aspect ratio is the ratio of __(a)__ to __(b)__.

Answer 2

(a) = Wing Span, (b) = Chord

Question 3

Complete the simplified lift formula below assuming that in flight the wing area remains constant and the flap setting remains unchanged:

Lift = (a) x (b)

a = _____ __ ______

b = ________

Answer 3

The correct answer is: (a) → Airspeed, (a) → Angle of Attack, (b) → Airspeed, (b) → Angle of Attack

Question 4

In cruise flight, low speed is associated with a low angle of attack and therefore a low C_{L}.

Select one:
True
False

Answer 4

In cruise flight, HIGH speed is associated with a low angle of attack and therefore a low C_{L}.

The correct answer is ‘False’.

Question 5

A highly cambered aerofoil will have a greater lifting ability and will be more manoeuvrable at slower speeds.

Select one:
True
False

Answer 5

Yes! This is why aircraft designed for slow speed operations (Like top dressing aircraft) have aerofoils with a high camber.

The correct answer is ‘True’.

Question 6

Match the statements with the missing words:

A contaminated aerofoil will have a _____ CL max compared to an uncontaminated aerofoil.
A contaminated aerofoil will have a _____ stalling angle compared to an uncontaminated aerofoil.

Answer 6

reduced

reduced

Question 7

An aerofoil with an increased camber will have a ______ CL max compared to a symmetrical aerofoil.

An aerofoil with an increased camber will have a ______ stalling angle compared to a symmetrical aerofoil.

Answer 7

increased,

practically unchanged

Question 8

Assuming that other factors remain equal, an aircraft with an increased coefficient of lift over the entire range of angle of attack means the aircraft can:

Select one or more:

a. Fly at higher speeds
b. Achieve the stall angle of attack at a faster speed
c. Take off and land from longer runways
d. Fly level with a higher angle of attack and the same speed
e. Achieve the stall angle of attack at a slower speed
f. Take off and land from shorter runways
g. Fly level with a lower angle of attack and the same speed
h. Fly at slower speeds

Answer 8

The correct answers are: Fly at slower speeds, Take off and land from shorter runways, Fly level with a lower angle of attack and the same speed, Achieve the stall angle of attack at a slower speed

Question 9

On a typical CL graph for a conventional aerofoil, what is the value of CL that corrosponds to CL max?

(Enter the value only)

Answer 9

1.4

Question 10

On a typical CL graph for a conventional aerofoil, what is the angle of attack that corrosponds to CL max?

(Enter the value only)

Answer 10

The correct answer is: 16

Question 11

An aerofoil with a increased aspect ratio will have a ______ CL max compared to a lower aspect ratio aerofoil.
An aerofoil with an increased aspect ratio will have a ______ stalling angle compared to a lower aspect ratio aerofoil.

Answer 11

→ increased,

→ decreased

Question 12

What two factors can be varied to control Coefficient of Lift (C_{L})?

Select one or more:

a. True Airspeed
b. Aspect Ratio
c. Air Density
d. Camber
e. Engine power
f. Angle of Attack
g. Surface area
h. Contamination

Answer 12

Camber, Angle of Attack

Question 13

A highly cambered aerofoil will have a greater lifting ability and will be more manoeuvrable at slower speeds.

Select one:
True
False

Answer 13

Yes! This is why aircraft designed for slow speed operations (Like top dressing aircraft) have aerofoils with a high camber.

The correct answer is ‘True’

Question 14

An aerofoil with an increased camber will have a ______ CL max compared to a symmetrical aerofoil. → An aerofoil with an increased camber will have a ______ stalling angle compared to a symmetrical aerofoil.

Answer 14

increased,

→ practically unchanged

Question 15

For a typical cambered wing at zero degrees angle of attack, CL is zero and so lift is zero.

Select one:
True
False

Answer 15

CL is zero at zero degrees angle of attack only for SYMMETRICAL aerofoils, not cambered ones.

The correct answer is ‘False’

Question 16

The area of the aerofoil that is most sensitive to contamination is:

Select one:

a. The underside of the aerofoil
b. From the leading edge to about 20% - 30% of the chord
c. From the trailing edge to about 20% - 30% of the chord
d. From the trailing edge to about 60% - 70% of the chord
e. 30% - 70% of the chord

Answer 16

The correct answer is: From the leading edge to about 20% - 30% of the chord

Question 17

At low to a moderately high angle of attack, the coefficient of lift increases in a more or less direct proportion to angle of attack. This linear relationship from low to reasonably high angles of attack applies to most aerofoil shapes.

Select one:
True
False

Answer 17

The correct answer is ‘True’.

Question 18

On a CL graph for a SYMMETRICAL aerofoil, what is the angle of attack that will produce zero lift (the zero lift angle)?

(Enter the value only)

Answer 18

The correct answer is: 0

Question 19

On a typical CL graph for a conventional aerofoil, what is the angle of attack that will produce zero lift (the zero lift angle)?

(Enter the value only)

Answer 19

The correct answer is: -4

Question 20

A highly cambered aerofoil will have a greater lifting ability and will be more manoeuvrable at slower speeds.

Answer 20

The correct answer is ‘True’.

Question 21

A contaminated aerofoil will have a _____ CL max compared to an uncontaminated aerofoil.

A contaminated aerofoil will have a _____ stalling angle compared to an uncontaminated aerofoil.

Answer 21

reduced

reduced

Question 22

In cruise flight, low speed is associated with a low angle of attack and therefore a low C_{L}.

Select one:
True
False

Answer 22

In cruise flight, HIGH speed is associated with a low angle of attack and therefore a low C_{L}.

The correct answer is ‘False’.

Question 23

In cruise flight, high speed is associated with a low angle of attack and therefore a low C_{L}.

Select one:
True
False

Answer 23

The correct answer is ‘True’.

Question 24

An aerofoil with a decreased aspect ratio will have a ______ CL max compared to a higher aspect ratio aerofoil.

An aerofoil with a decreased aspect ratio will have a ______ stalling angle compared to a higher aspect ratio aerofoil.

Answer 24

decreased,

increased

Question 25

An aerofoil with a increased aspect ratio will have a ______ CL max compared to a lower aspect ratio aerofoil.

An aerofoil with an increased aspect ratio will have a ______ stalling angle compared to a lower aspect ratio aerofoil.

Answer 25

increased,

decreased