C25 - Propellers

Question 1

Define Propeller Disc?

Answer 1

The circular area where the blades rotate.

Question 2

How is a Blade attached to the Hub of a Propeller System?

Answer 2

At the Blade Root.

Question 3

Define Blade Chord Line?

Answer 3

Imaginary straight line from the Leading to Trailing Edge of the Blade.

Question 4

Define Blade Angle?

Answer 4

Angle between Plane of Rotation and Chord Line

Question 5

True of False. The Blade Angle decreases from the Hub to the Tip?

Answer 5

True.

Question 6

What percentage is the Blade Angle measured between the Hub and Tip?

Answer 6

75%.

Question 7

Define Blade Angle of Attack?

Answer 7

Between the Relative Airflow and the Blade’s Chord Line.

Question 8

Define Helix Angle?

Answer 8

Between the Plane of Rotation and the Relative Airflow.

Question 9

What is the sum of the Blade Angle?

Answer 9

Helix Angle + Angles of Attack.

Question 10

Define Geometric Pitch?

Answer 10

The distance a Propeller would travel forward in one revolution.

Question 11

Define Effective Pitch?

Answer 11

The actual distance a Propeller would travel forward in one revolution.

Question 12

What is known as the difference between Geometric and Effective Pitch?

Answer 12

Slip.

Question 13

What are small pitch angles known as?

Answer 13

Fine Pitch.

Question 14

What are larger pitch angles known as?

Answer 14

Coarse Pitch.

Question 15

What is the term and angle for the largest positive angle of a Blade (2)?

Answer 15

• Fully Coarse / Feathered.

- 90°.

Question 16

What is the term and angle for the smallest positive angle of a Blade (2)?

Answer 16

• Fully Fine.

- 0°.

Question 17

Name four types of Propeller Systems?

Answer 17

• Fixed-Pitch.
• Two-Pitch.
• Adjustable Pitch.
• Constant Speed.

Question 18

What are the two forces acting on a Blade?

Answer 18

• Thrust.

- Torque.

Question 19

What two factors are linked to the direction of the Relative Airflow on a Blade?

Answer 19

• Rotational Speed of the Propeller (RPM).

- Inflow into the Propeller (TAS).

Question 20

With regards to Blade Angle of Attack, what happens when the Speed of an Aircraft reduces?

Answer 20

Blade AoA increases.

Question 21

With regards to Blade Angle of Attack, what happens when the Speed of an Aircraft increases?

Answer 21

Blade AoA decreases.

Question 22

With regards to Blade Angle of Attack, what happens when RPM is increased?

Answer 22

Blade AoA increases.

Question 23

What happens at low RPM on a Propeller Blade?

Answer 23

Negative Blade Angle of Attack.

Question 24

What happens at Negative Blade Angle of Attack?

Answer 24

The Aircraft experiences an increase in Drag.

Question 25

How is the Blade’s Angle of Attack kept constant?

Answer 25

The Blade is twisted by design.

Question 26

With Variable Pitch Propellers, what Pitch is selected during Take-off?

Answer 26

Fine Pitch.

Question 27

With Variable Pitch Propellers, what Pitch is selected as TAS increases during flight?

Answer 27

Coarsen Pitch.

Question 28

If an Engine Failure occurs, what condition is Propeller said to be in?

Answer 28

Windmilling.

Question 29

The Drag from a failed Propeller can be minimised by setting the Blades head-on to the Relative Airflow. This position is known as?

Answer 29

Feathered.

Question 30

Name one benefit of Windmilling after an Engine Failure?

Answer 30

It can assist in an Engine Restart in flight.

Question 31

How can reserve thrust be produced on a Blade?

Answer 31

Beyond Fully Fine Pitch (0°).

Question 32

What RPM does a Fan rotate at?

Answer 32

2700 RPM.

Question 33

What Relative Airflow speed can a Fan Tip experience?

Answer 33

780kt.