Propellers

Question 1

What is the primary role of propellers in aircraft?

Answer 1

To produce thrust for forward propulsion.

Question 2

What are the three types of propellers?

Answer 2

Fixed pitch, ground adjustable, and in-flight adjustable.

Question 3

Why is blade twist important in propeller design?

Answer 3

To manage different speeds along the propeller blade and optimize thrust.

Question 4

What are the advantages of fixed pitch propellers?

Answer 4

They are cheap, simple, reliable, and easy to learn.

Question 5

What are the disadvantages of fixed pitch propellers?

Answer 5

They are only efficient at one speed and RPM, requiring frequent throttle adjustments.

Question 6

What factors are considered in propeller design?

Answer 6

Materials, number of blades, diameter, face size, angle, aspect ratio, noise, and thrust production.

Question 7

What forces act on a propeller?

Answer 7

Centrifugal force, thrust bending force, and torque bending force.

Question 8

What is the significance of a DA 42 propeller blade’s cost?

Answer 8

It highlights the importance of understanding propeller materials and maintenance due to its $10,000 price.

Question 9

Why are fixed pitch propellers less versatile?

Answer 9

They are only efficient at one combination of true airspeed (TAS) and RPM.

Question 10

What will be covered in the next session regarding propellers?

Answer 10

The constant speed unit (CSU) and its differences from fixed pitch propellers.

Question 11

What is the role of the governor in a Constant Speed Unit (CSU)?

Answer 11

It adjusts the blade angle to maintain efficiency at varying airspeeds.

Question 12

What happens during an overspeed scenario in a CSU aircraft?

Answer 12

Flyweights move outwards, allowing oil to flow into the hub, coarsening the blade angle.

Question 13

What is the relationship between manifold pressure and RPM in a CSU aircraft?

Answer 13

The throttle controls manifold pressure, while the blue pitch lever controls propeller RPM.

Question 14

What are the two types of fixed pitch propellers?

Answer 14

Cruise prop (25-degree blade angle) and climb prop (15-degree blade angle).

Question 15

What happens during windmilling in an unpowered propeller?

Answer 15

Air forces the propeller to rotate, causing drag and reducing glide range.

Question 16

What is feathering, and why is it important in multi-engine aircraft?

Answer 16

Feathering sets the blade near 90 degrees to the airflow, reducing drag and asymmetric thrust, improving control.

Question 17

What causes the propeller to move to a coarse pitch in a CSU?

Answer 17

Loss of oil pressure or a speed of spring failure.

Question 18

What are the effects of carburetor icing on propeller performance?

Answer 18

It reduces manifold pressure without changing RPM, affecting engine performance.

Question 19

How does the CSU handle underspeed scenarios?

Answer 19

Flyweights move inwards, allowing oil to flow out of the hub, fining the blade angle.

Question 20

What is the function of auto feathering systems in multi-engine aircraft?

Answer 20

They detect engine failure and automatically feather the propeller to reduce drag and improve control.

Question 21

What is the importance of manifold pressure in CSU aircraft?

Answer 21

Manifold pressure allows for optimal performance and greater range by limiting engine speed while increasing power.

Question 22

What is the significance of the full forward pitch and idle mixture setting in CSU aircraft?

Answer 22

It aids engine startup and shutdown while reducing stress on the engine during flight.

Question 23

What are centrifugal and aerodynamic twisting moments in propellers?

Answer 23

Centrifugal force acts to straighten the blades, while aerodynamic force creates a finer angle of attack.

Question 24

What happens in beta mode for aircraft propellers?

Answer 24

The propeller creates drag instead of thrust, often used during landing.

Question 25

How does carburetor icing affect engine performance?

Answer 25

Manifold pressure decreases while RPM remains the same, indicating icing.

Question 26

What happens to manifold pressure when pulling the pitch lever back?

Answer 26

Manifold pressure increases as the pitch lever is pulled back.

Question 27

What is a noticeable symptom of magneto failure in flight?

Answer 27

Decreased manifold pressure and RPM.

Question 28

How does volumetric efficiency relate to carburetor fuel systems?

Answer 28

It measures the relationship between actual performance and engine efficiency.

Question 29

What is the purpose of the enrichment valve in high-power settings?

Answer 29

To minimize detonation and ensure smooth engine operation.

Question 30

What happens if the throttle is increased too rapidly during takeoff?

Answer 30

It can starve the engine of fuel, leading to performance issues.

Question 31

What role does the flyweight sensor play in a CSU system?

Answer 31

It responds to engine RPM changes and controls oil flow via the pilot valve.

Question 32

What are the recommended throttle and mixture settings during descent and landing?

Answer 32

Reduce power and richen the mixture to adjust for increased air density.

Question 33

What are the key steps for checking the CSU system during run-ups?

Answer 33

Monitor the governor’s response to changes in throttle and RPM settings to ensure proper function.