Podcast
Questions and Answers
What is the primary function of the governor in a constant-speed feathering propeller?
What is the primary function of the governor in a constant-speed feathering propeller?
How does the governor increase the blade angle of a constant-speed feathering propeller?
How does the governor increase the blade angle of a constant-speed feathering propeller?
What role do the counterweights play in feathering a propeller?
What role do the counterweights play in feathering a propeller?
What must a pilot do to feather the blades of a constant-speed feathering propeller?
What must a pilot do to feather the blades of a constant-speed feathering propeller?
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Which type of propellers commonly feature full feathering capability?
Which type of propellers commonly feature full feathering capability?
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What action occurs when the governor flyweights overcome the tension of the speeder spring?
What action occurs when the governor flyweights overcome the tension of the speeder spring?
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How does the governor maintain the required balance between control forces?
How does the governor maintain the required balance between control forces?
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In which condition is the governor considered to be operating in an underspeed condition?
In which condition is the governor considered to be operating in an underspeed condition?
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What happens to the flyweights during an underspeed condition?
What happens to the flyweights during an underspeed condition?
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What effect does the pilot valve being forced down by the speeder spring have?
What effect does the pilot valve being forced down by the speeder spring have?
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Which component is primarily responsible for maintaining engine speed in a governor mechanism?
Which component is primarily responsible for maintaining engine speed in a governor mechanism?
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What is the primary function of the propeller piston in the governor mechanism?
What is the primary function of the propeller piston in the governor mechanism?
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What results from increasing the load on the engine in a governor mechanism?
What results from increasing the load on the engine in a governor mechanism?
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What is the primary reason the shape of a propeller blade creates thrust?
What is the primary reason the shape of a propeller blade creates thrust?
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How does thrust relate to the mass of air handled and slipstream velocity?
How does thrust relate to the mass of air handled and slipstream velocity?
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What happens to engine RPM when the blade angle of a propeller is increased?
What happens to engine RPM when the blade angle of a propeller is increased?
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What aerodynamic factor contributes to lift above a wing?
What aerodynamic factor contributes to lift above a wing?
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Which of the following statements about thrust is NOT accurate?
Which of the following statements about thrust is NOT accurate?
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What is true about the area of decreased pressure in front of a propeller?
What is true about the area of decreased pressure in front of a propeller?
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What role does the blade angle play in controlling the load on the propeller?
What role does the blade angle play in controlling the load on the propeller?
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What is the result of changing the blade angle on a propeller during flight?
What is the result of changing the blade angle on a propeller during flight?
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What happens when the pilot selects a new rpm range through the propeller control?
What happens when the pilot selects a new rpm range through the propeller control?
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What condition results when the forces in the governor are unequal?
What condition results when the forces in the governor are unequal?
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What is the role of the governor in maintaining engine performance?
What is the role of the governor in maintaining engine performance?
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What happens when engine speed falls below the governor set rpm?
What happens when engine speed falls below the governor set rpm?
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What is the maximum range of the speeder spring propeller governing?
What is the maximum range of the speeder spring propeller governing?
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How does the pilot valve aid in controlling the propeller's blade angle?
How does the pilot valve aid in controlling the propeller's blade angle?
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What effect does a change in aircraft attitude have on the propeller governor's operation?
What effect does a change in aircraft attitude have on the propeller governor's operation?
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What is the consequence of the governor being unable to maintain the correct rpm beyond its specified range?
What is the consequence of the governor being unable to maintain the correct rpm beyond its specified range?
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What does a governor do when the engine rpm decreases?
What does a governor do when the engine rpm decreases?
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In a constant-speed propeller system, what happens in an overspeed condition?
In a constant-speed propeller system, what happens in an overspeed condition?
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What is a characteristic of a good constant-speed control system?
What is a characteristic of a good constant-speed control system?
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What is the primary purpose of the rear cone in a fixed-pitch wooden propeller assembly?
What is the primary purpose of the rear cone in a fixed-pitch wooden propeller assembly?
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Which of these forces contributes to moving the blades toward the high pitch direction?
Which of these forces contributes to moving the blades toward the high pitch direction?
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How does the propeller governor help maintain engine rpm?
How does the propeller governor help maintain engine rpm?
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Why might spacers be included with a splined-shaft propeller assembly?
Why might spacers be included with a splined-shaft propeller assembly?
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What occurs when the rpm of a constant-speed propeller falls below the governor's set value?
What occurs when the rpm of a constant-speed propeller falls below the governor's set value?
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What design feature allows the front cone to be fitted over a retaining nut flange?
What design feature allows the front cone to be fitted over a retaining nut flange?
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What eliminates the need for a rear-cone spacer in some hub types?
What eliminates the need for a rear-cone spacer in some hub types?
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What is the role of flyweights in a constant-speed propeller?
What is the role of flyweights in a constant-speed propeller?
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How does the front cone assist in detaching the propeller from the shaft?
How does the front cone assist in detaching the propeller from the shaft?
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What happens when a constant-speed propeller system maintains a constant blade angle?
What happens when a constant-speed propeller system maintains a constant blade angle?
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What material is used for the rear cone in the hub of the propeller?
What material is used for the rear cone in the hub of the propeller?
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What type of cone constitutes the front cone in a fixed-pitch wooden propeller assembly?
What type of cone constitutes the front cone in a fixed-pitch wooden propeller assembly?
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What specific function does the snap ring serve in relation to the front cone?
What specific function does the snap ring serve in relation to the front cone?
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Study Notes
Week 1 Complete
- AVIA-1052 course completed for week 1
- Contact Matt C if there are errors or needed improvements.
Week 1 of 1 Day 1
- AVIA-1052 course, week 1, day 1
Previously On AVIA-1052
- This is the first class
- Learning about propellers
Today On AVIA-1052
- Discussing propellers, including general propeller stuff, aircraft propeller theory, and basic propeller controls
Where are we?
- Powerplant (Vol. 2), pages 7-2 to 7-6
- Start at General
- Stop at Propeller Location
- FAA Handbooks referenced
Propellers
- The unit that absorbs the engine's power output
- Propeller development has progressed through many stages since the first fabric-covered sticks
- Development has led to complex propulsion systems
- Constant-speed systems, utilizing a flyweight-equipped governor, regulate blade pitch for consistent engine speed
Powerplant 7-2
- Propellers started as simple two-bladed wooden propellers
- Advanced to complex systems, including variable-pitch and constant-speed feathering systems
- These improve flying efficiency
Basic Propeller Principles
- An aircraft propeller consists of two or more blades
- Each blade is a rotating wing that creates thrust
- Engine power rotates propeller blades
Powerplant 7-3
- Propeller Aerodynamic Process
- Thrust horsepower is related to engine power output
- Different propeller types, including fixed-pitch, ground-adjustable, and controllable-pitch have various advantages
Propeller Aerodynamic Process
- Propeller efficiency is the ratio of thrust horsepower to brake horsepower
- Efficiency varies from 50-87% based on slippage.
- Pitch is not the same as blade angle, but an increase or decrease in one often corresponds to the other.
- Geometric pitch is the distance a propeller advances in one revolution with no slippage.
- Effective pitch is the distance a propeller advances during one revolution considering slippage.
Propeller Aerodynamic Process
- Chord line of a propeller blade is similar to an airfoil
- Blade back - the cambered side of the propeller blade
- Blade face - the flat side of the propeller blade
- Chord line - the imaginary line from the leading edge to the trailing edge of the blade
- Leading edge - the thick edge of the blade that meets the air as the propeller rotates
Propeller Aerodynamic Process
- Centrifugal forces tend to pull blades out of the hub at high rpm.
- Blade weight is important to propeller design
- Excessive blade tip speed may result in poor efficiency, fluttering, and vibration.
- Rotating the propeller too fast may lead to poor blade efficiency, fluttering, and vibration.
- Propeller speed is limited, which constrains aircraft speed.
Propeller Aerodynamic Process
- Propeller-driven aircraft are limited to approximately 400 mph (644 km/h)
- Turbofan engines were used for higher-speed aircraft as aircraft speed increased
Propeller Aerodynamic Process
- Propeller-driven aircraft have advantages like shorter takeoff and landing times, lower maintenance costs, and are used in various aviation applications
Propeller Systems
- Various types of propeller systems, including fixed-pitch, ground-adjustable, controllable-pitch, and constant-speed, have been developed for different applications.
- These types are for various aircraft installations like speed and operational needs.
Propeller Diagrams
- Basic nomenclature of simple fixed-pitch, two-bladed wooden propellers
- Aerodynamic cross-section of a blade (includes terms like blade tip, trailing edge, leading edge, hub, back of blade, etc.)
Aircraft Propeller Theory
- The aircraft propeller consists of two or more blades, each essentially a rotating wing.
- The blades produce forces to propel the airplane.
- The power needed to rotate propeller blades is furnished by the engine through a central hub.
Basic Propeller Principles
- Propeller assemblies are mounted on shafts.
- Low-horsepower engines have propellers which are an extension of the crankshaft.
- High-horsepower engines have propellers which are mounted directly on a propeller shaft and are geared to the engine crankshaft.
Propeller Aerodynamic Process
- An airplane moving through air produces drag, so forces are applied to counter the drag, this force is called thrust.
- The work done by thrust is equal to the thrust times the distance the airplane moves.
- Power expended by thrust is equal to the thrust times the velocity at which the airplane moves.
- Power = thrust x velocity
- Different propeller designs affect the amount of power and the efficiency of that transfer.
Propeller Aerodynamic Process
- Thrust horsepower is the measure of the power expended by thrust.
- Engine supplies brake horsepower, which is transferred through a rotating shaft to the propeller, then converted to thrust horsepower.
- Some power is lost in this conversion, thus, propeller design must try to minimize it, for maximum efficiency.
Propeller Aerodynamic Process
- Propeller efficiency is the ratio of thrust horsepower to brake horsepower, typically 50-87%.
- Efficiency is affected by the degree of propeller slip, defined as the difference between geometric pitch and effective pitch.
- Blade angle is not the same as pitch, with changes in pitch usually correlating to changes in blade angle.
- Geometric pitch is calculated to give the predicted advancement of a propeller in one revolution if no slippage occurred.
Propeller Aerodynamic Process
- Chord line is defined as the imaginary line running from the leading edge to the trailing edge of a blade section.
- Blade face is the flat side of the propeller that faces the air, useful for measuring blade angle.
- Blade back is the cambered side of the blade, which has a similar shape as the upper surface of an airfoil.
Propeller Aerodynamic Process
- Centrifugal force tends to pull the blades out of the hub.
- Blade weight is an important component to a propeller design to counter centrifugal force.
- Excessive blade tip speed can cause poor blade efficiency, fluttering, and vibration.
Propeller Aerodynamic Process
- Propeller driven aircraft have limits to their speed, due to the excessive blade speed of a propeller.
- Turbofan engines were used for higher-speed aircraft as aircraft speeds increased.
Propeller Advantages
- Propeller advantages include short takeoff and landing times, less expensive to maintain, and simple operation.
- These advantages make propellers preferable for various types of aircraft, mainly smaller aircraft.
Week 1 of 1 Day 2
- Types of propellers: fixed-pitch, test club, ground-adjustable, controllable-pitch, constant-speed and feathering
Propeller Location
- Tractor propeller - mounted on the upstream end of a drive shaft in front of the supporting structure.
- Pusher propeller - mounted on the downstream end of a drive shaft behind the supporting structure.
Fixed-Pitch Propeller
- Blade pitch is fixed – cannot be changed during flight
- Often used on low-power, lower-speed, and lower-altitude aircraft
- Simpler design compared to other propeller types, such as constant-speed or reversible-pitch propellers.
- Cheaper to manufacture compared to others
Test Club Propeller
- Used in test and break-in of reciprocating engines
- Made to provide correct amount of load on engine during test break-in period
- Provides extra cooling air flow during testing
Ground-Adjustable Propeller
- Pitch can only be changed when the propeller is not turning.
- A non-common type of propeller used in some applications
Controllable-Pitch Propeller
- Blade pitch can be changed while the propeller is rotating.
- Allows for better adjustments, as needed, for different flight conditions.
- Fewer types of these models compared to other propellers.
Constant-Speed Propeller
- Maintains a constant engine rpm despite changing flight conditions.
- Achieved by automatically adjusting blade pitch via a governor.
Feathering Propeller
- Blade pitch is changed to be parallel with the airflow when the engine fails or stalls, therefore reducing drag significantly.
- Necessary for multi-engine aircraft to prevent damage when one engine fails.
Reverse-Pitch Propeller
- Can reverse the thrust and deceleration of an aircraft.
- Useful for decreasing airspeed quickly during landing phases of flight.
Propeller Governor
- A device that automatically adjusts the pitch of the propeller blades in order to maintain a desired engine speed, regardless of the aircraft's attitude, by regulating or controlling the flow of oil pressure.
- Necessary to compensate for changes during flight, allowing for efficient operation.
Propeller Auxiliary Systems
- Auxiliary systems help propel an aircraft under difficult circumstances, such as when one or more engines fail
- Propeller auxiliary systems include ice control and anti-icing systems
Ice Control Systems
- Ice formations on blades and propellers may reduce their effectiveness and may even break blades.
- Anti-icing systems and fluid anti-ice systems are used to combat ice.
- These systems apply fluids at the right moments to stop ice from forming, before the ice build up becomes excessively hazardous.
- Systems include a tank, a pump, and a control system that regulates fluid quantity and permits changes in pumping rate under varying icing conditions.
Deicing System
- Electric propeller-icing control systems employ an electrical energy source in conjunction with a resistance heating element.
- These are placed inside of the propeller blades in order to heat and prevent ice build up and to melt frost.
Propeller Synchronization and Synchrophasing
- Systems for maintaining consistent speed in multi-engine aircraft, and to control and synchronize the engine rpm of each engine/propeller combination.
- Synchronization systems reduce vibration and eliminates the "beats" of the propeller due to the combined rotation.
- These systems are normally electronic.
Autofeathering System
- An auto-feathering system automatically feathers the propeller, if engine power is lost.
- It uses a solenoid valve and torque switches to sense low torque to quickly feather the blades to a reduced pitch through a fluid process.
Propeller Inspection and Maintenance
- Regular inspections for flaws, cracks, and corrosion are necessary.
- Various checks of defects should be performed as indicated in various manuals.
Wood Propeller Inspection
- Wood propellers must be inspected frequently to ensure reliability (airworthiness)
- Inspectiion should check for cracks, dents, and damage from corrosion.
Metal Propeller Inspection
- Metal propellers and blades may be affected more by fatigue failures than wood.
- Using a magnifying glass is helpful in checking surfaces and identifying cracks.
- Tachometer inspection is important to check to see that the propeller isn't moving faster than the rated speed.
Aluminum Propeller Inspection
- Examine aluminum for cracks and other flaws and make a note of it when it is observed.
- Multiple deep nicks or gouges are cause for replacement.
- Use dye penetrant testing to confirm suspected cracks.
Composite Propeller Inspection
- Visual inspections are important to detect nicks, gouges, and any signs of excessive wear.
- Tapping the blade with a coin can reveal if there are any internal defects.
Propeller Vibration
- Vibration can be caused by a lack of balance in the blades.
- Static unbalance occurs when the CG does not coincide with the rotation axis –
- Dynamic unbalance occurs when propeller elements, such as blades or counterweights, do not rotate in the same plane
- Tracking and blade angle settings can be checked to see if these are causing the vibration.
Propeller Removal and Installation
- Following the manufacturer's specific procedures is crucial.
- Steps for removal and reinstallation depend on the propeller type.
Setting the Propeller Governor
- Setting the governor requires moving the throttle to takeoff position and observing engine rpm and manifold pressure.
- Adjustments must be made to the governor according to the manufacturer’s instructions during ground run-up, or anytime the position is adjusted.
Servicing Propellers
- Propeller servicing includes periodic cleaning and lubrication.
- Keeping a record of the process is important to show compliance.
Propeller Lubrication
- Different types of propellers have differing lubrication needs; thus, the proper steps must be followed to keep them running at an acceptable capacity.
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Description
Test your knowledge of the operation and function of governors in constant-speed feathering propellers. This quiz covers key concepts, including how governors control blade angle and the role of counterweights. Perfect for aviation enthusiasts and pilot trainees alike.
