Propellers Flashcards
What is the primary role of propellers in aircraft?
To produce thrust for forward propulsion.
What are the three types of propellers?
Fixed pitch, ground adjustable, and in-flight adjustable.
Why is blade twist important in propeller design?
To manage different speeds along the propeller blade and optimize thrust.
What are the advantages of fixed pitch propellers?
They are cheap, simple, reliable, and easy to learn.
What are the disadvantages of fixed pitch propellers?
They are only efficient at one speed and RPM, requiring frequent throttle adjustments.
What factors are considered in propeller design?
Materials, number of blades, diameter, face size, angle, aspect ratio, noise, and thrust production.
What forces act on a propeller?
Centrifugal force, thrust bending force, and torque bending force.
What is the significance of a DA 42 propeller blade’s cost?
It highlights the importance of understanding propeller materials and maintenance due to its $10,000 price.
Why are fixed pitch propellers less versatile?
They are only efficient at one combination of true airspeed (TAS) and RPM.
What will be covered in the next session regarding propellers?
The constant speed unit (CSU) and its differences from fixed pitch propellers.
What is the role of the governor in a Constant Speed Unit (CSU)?
It adjusts the blade angle to maintain efficiency at varying airspeeds.
What happens during an overspeed scenario in a CSU aircraft?
Flyweights move outwards, allowing oil to flow into the hub, coarsening the blade angle.
What is the relationship between manifold pressure and RPM in a CSU aircraft?
The throttle controls manifold pressure, while the blue pitch lever controls propeller RPM.
What are the two types of fixed pitch propellers?
Cruise prop (25-degree blade angle) and climb prop (15-degree blade angle).
What happens during windmilling in an unpowered propeller?
Air forces the propeller to rotate, causing drag and reducing glide range.
What is feathering, and why is it important in multi-engine aircraft?
Feathering sets the blade near 90 degrees to the airflow, reducing drag and asymmetric thrust, improving control.
What causes the propeller to move to a coarse pitch in a CSU?
Loss of oil pressure or a speed of spring failure.
What are the effects of carburetor icing on propeller performance?
It reduces manifold pressure without changing RPM, affecting engine performance.
How does the CSU handle underspeed scenarios?
Flyweights move inwards, allowing oil to flow out of the hub, fining the blade angle.
What is the function of auto feathering systems in multi-engine aircraft?
They detect engine failure and automatically feather the propeller to reduce drag and improve control.
What is the importance of manifold pressure in CSU aircraft?
Manifold pressure allows for optimal performance and greater range by limiting engine speed while increasing power.
What is the significance of the full forward pitch and idle mixture setting in CSU aircraft?
It aids engine startup and shutdown while reducing stress on the engine during flight.
What are centrifugal and aerodynamic twisting moments in propellers?
Centrifugal force acts to straighten the blades, while aerodynamic force creates a finer angle of attack.
What happens in beta mode for aircraft propellers?
The propeller creates drag instead of thrust, often used during landing.
How does carburetor icing affect engine performance?
Manifold pressure decreases while RPM remains the same, indicating icing.
What happens to manifold pressure when pulling the pitch lever back?
Manifold pressure increases as the pitch lever is pulled back.
What is a noticeable symptom of magneto failure in flight?
Decreased manifold pressure and RPM.
How does volumetric efficiency relate to carburetor fuel systems?
It measures the relationship between actual performance and engine efficiency.
What is the purpose of the enrichment valve in high-power settings?
To minimize detonation and ensure smooth engine operation.
What happens if the throttle is increased too rapidly during takeoff?
It can starve the engine of fuel, leading to performance issues.
What role does the flyweight sensor play in a CSU system?
It responds to engine RPM changes and controls oil flow via the pilot valve.
What are the recommended throttle and mixture settings during descent and landing?
Reduce power and richen the mixture to adjust for increased air density.
What are the key steps for checking the CSU system during run-ups?
Monitor the governor’s response to changes in throttle and RPM settings to ensure proper function.
With the constant speed unit, what happens if there is a loss of oil pressure?
