Podcast
Questions and Answers
What is the main purpose of a propeller?
What is the main purpose of a propeller?
To convert the rotary power of the engine into thrust, which propels the aircraft through the air.
What are the two main types of propeller installations?
What are the two main types of propeller installations?
What is the primary function of a constant-speed propeller system?
What is the primary function of a constant-speed propeller system?
To maintain a constant engine speed regardless of changes in aircraft attitude or power settings.
What is the purpose of blade feathering in a propeller?
What is the purpose of blade feathering in a propeller?
Signup and view all the answers
A ground-adjustable propeller can be adjusted while in flight.
A ground-adjustable propeller can be adjusted while in flight.
Signup and view all the answers
What are the primary factors that influence the efficiency of a propeller?
What are the primary factors that influence the efficiency of a propeller?
Signup and view all the answers
What is the primary purpose of the slip ring system in a propeller deicing system?
What is the primary purpose of the slip ring system in a propeller deicing system?
Signup and view all the answers
What is the purpose of a propeller synchronization system?
What is the purpose of a propeller synchronization system?
Signup and view all the answers
An autofeathering system is typically used during an emergency landing.
An autofeathering system is typically used during an emergency landing.
Signup and view all the answers
During the inspection of a wooden propeller, what are some of the key areas that require careful attention?
During the inspection of a wooden propeller, what are some of the key areas that require careful attention?
Signup and view all the answers
What are some of the crucial aspects to consider when inspecting a metal propeller?
What are some of the crucial aspects to consider when inspecting a metal propeller?
Signup and view all the answers
How often should a propeller tachometer be inspected?
How often should a propeller tachometer be inspected?
Signup and view all the answers
What is the purpose of blade tracking in propeller maintenance?
What is the purpose of blade tracking in propeller maintenance?
Signup and view all the answers
What are some of the crucial steps involved in propeller removal and installation?
What are some of the crucial steps involved in propeller removal and installation?
Signup and view all the answers
What is the purpose of propeller balancing?
What is the purpose of propeller balancing?
Signup and view all the answers
What is the common method for addressing propeller hunting?
What is the common method for addressing propeller hunting?
Signup and view all the answers
What is the purpose of a propeller governor?
What is the purpose of a propeller governor?
Signup and view all the answers
What is the purpose of an autofeathering system?
What is the purpose of an autofeathering system?
Signup and view all the answers
What is the purpose of a propeller deicing system?
What is the purpose of a propeller deicing system?
Signup and view all the answers
Electric propeller deicing systems should only be operated when the propellers are rotating.
Electric propeller deicing systems should only be operated when the propellers are rotating.
Signup and view all the answers
Study Notes
Week 1 Complete
- Week 1 of AVIA-1052 is complete.
- Contact Matt C with any errors or improvements needed.
Previously On AVIA-1052
- This is the first class.
- Topics covered include propellers, propeller theory, and basic propeller controls.
Today On AVIA-1052
- Topics include propeller location, different types of propellers, including fixed-pitch, test club, ground-adjustable, controllable-pitch, constant-speed, feathering, reverse-pitch propellers, and propeller governor.
- FAA handbooks are relevant for this topic.
Where are we?
- Powerplant (Vol. 2).
- Start at section 7-2 to 7-6
- Topics include propeller location.
- Stop at section 7-6
- Relevant FAA handbooks are mentioned.
Propellers
-
The unit that must absorb the power output of the engine.
-
Propeller development has gone through many stages of development.
-
The first propellers were fabric-covered sticks designed to force air in a rearward direction.
-
Propellers have evolved from simple two-bladed wood propellers to complex turboprop aircraft systems.
-
More complex propeller systems have constant-speed and variable-pitch, feathering, and reversing systems. This allows the engine's rpm to be changed slightly for different flight conditions.
-
Constant-speed systems have a flyweight-equipped governor unit that controls the blade pitch angle to maintain constant engine speed.
-
Propeller efficiency ratios are often used in evaluation (thrust horsepower to brake horsepower).
-
The usual symbol for propeller efficiency use is the Greek letter "n" (eta).
-
Propeller efficiency varies widely depending on how much the propeller slips.
-
Pitch is not the same as blade angle; an increase or decrease in either is usually accompanied by an increase or decrease in the other.
-
Geometric pitch is the distance a propeller should advance in one revolution (with no slippage).
-
Effective pitch is the distance a propeller advances in one revolution (with slippage).
-
Geometric pitch - effective pitch = slip.
-
The chord line is an imaginary line drawn through the blade from the leading edge to the trailing edge.
-
The blade back is the cambered or curved side of the blade, similar to the upper surface of an aircraft wing
-
The blade face is the flat side of the propeller blade.
-
Most propellers are two-bladed.
-
Great increases in power output have resulted in the development of four- and six-bladed propellers.
-
Forces acting on propellers include centrifugal force, which tends to pull the blades out of the hub at high rpm.
-
Blade weight is important to propeller design.
-
Excessive blade tip speed can result in poor blade efficiency, fluttering, and vibration.
-
Aircraft speed is limited by propeller speed.
-
Propeller-driven aircraft have advantages, such as takeoff and landing being relatively short and less expensive to maintain.
Aircraft Propeller Theory
- The aircraft propeller consists of two or more blades; each blade is essentially a rotating wing.
- Propeller blades produce forces to create thrust.
- Engine power is needed to rotate the propeller blades.
Basic Propeller Principles
- Low- and high-horsepower engines are mounted on the shaft.
Propeller Aerodynamic Process
- Airplane movement generates a drag force.
- Thrust is needed to counteract the drag force for an airplane to move forward.
- The work performed by thrust is equivalent to multiplying the thrust by the distance the airplane moves.
- The power expended by thrust is the product of thrust and the velocity of the aircraft.
- Power = Thrust x Velocity
- Thrust horsepower is the expression for power expended when used in horsepower units.
- The engine produces brake horsepower for the propeller through a rotating shaft.
- The propeller converts brake horsepower into thrust horsepower.
- Some propeller power is lost in the conversion process.
- The propeller needs to be designed to reduce wasted power for maximum efficiency.
- Propeller efficiency is the ratio of thrust horsepower to brake horsepower.
- Propeller efficiency uses the Greek letter "n" (eta) as its symbol.
- Propeller efficiency varies from 50-87%.
- Pitch of the propeller is not the same as the blade angle, the blade angle is a part of determining the pitch.
- Geometric pitch is the distance the propeller advances during one full rotation, with no slippage.
- Slip is the difference between geometric and effective pitch.
- The chord line is an imaginary line extending from the propeller blade's leading edge to the trailing edge.
- The propeller blade's chord line is also how the blade element's chord thickness is determined.
Propeller Governor
- Constant-speed control consists of a gear pump, a pilot valve.
- The pump increases the pressure of the engine oil.
- Flyweights control the flow of oil.
- The position of the pilot valve controls the quantity of oil flowing from and to the propeller.
- A relief valve regulates the operating oil pressures in the governor.
Types of Propellers
- Types:
- Fixed-pitch
- Ground-adjustable
- Controllable-pitch
- Constant-speed
- Feathering
- Reverse-pitch
Propeller Location
- Propeller types are mounted on the upstream end of a drive shaft in front of the supporting structure. (tractor propeller)
- Propeller types are mounted on the downstream end of a drive shaft behind the supporting structure. (pusher propeller).
- Pusher propellers are more susceptible to damage than tractor propellers.
Wood Propeller Inspection
- Wood propellers should be inspected regularly.
- Inspect for cracks, dents, warpage, and glue failure.
- Inspect the trailing edge for delamination defects, and charring between the propeller and the flange.
- Check for cracks near the metal sleeve and the tightness of the lag screws.
Metal Propeller Inspection
- Inspect metal propellers for nicks, cuts, scratches, and other defects.
- Use a magnifying glass during the inspection.
- Inspect for the full length of the leading edge, especially near the tip.
- Inspect the full length of the trailing edge.
- Inspect the grooves and shoulders on the shank or other areas as needed.
Tachometer Inspection
- Ensure the engine tachometer is accurate.
- Accuracy should be measured every 100 hours or annually to avoid engine damage.
Aluminum Propeller Inspection
- Carefully inspect aluminum propellers for cracks or other flaws.
- Multiple deep nicks or gouges are cause for rejection.
Composite Propeller Inspection
- Visually inspect for nicks, gouges, loose material, erosion, cracks, debonds, and lightning strikes.
- Inspect for possible delamination and debonds.
- Use a metal coin to tap the composite blade (and cuff) to listen for an audible change that might indicate delamination.
Blade Tracking
- Blade tracking is the process of determining the positions of the propeller blades relative to each other.
Blade Angle Checking
- Obtain the blade angle setting and the blade station from the manufacturer's instructions.
- Do not use metal scribes to add markings to propeller blades, this can lead to blade failure.
- Use a bench-top protractor if the propeller is removed from the aircraft.
- Use a handheld protractor for on-aircraft propeller inspections.
Propeller Balancing
- Propeller unbalance can be either static or dynamic.
- Static unbalance occurs when the center of gravity does not coincide with the rotation axis.
- Dynamic unbalance occurs when the centers of gravity of the blades or counterweights do not lie in the same plane of rotation.
- Dynamic unbalance can be mitigated through inspection and correction.
Propeller Removal and Installation
- Remove the spinner dome and safety wire (if necessary).
- Support the assembly with a sling and make sure to check the engine and airframe manuals.
- Install the propeller, making sure to align the dowel studs with the corresponding engine mounting flange holes.
- Tighten the mounting nuts according to manufacturer's specifications.
Setting the Propeller Governor
- At the time of propeller, propeller governor, or engine installation, take the following steps:
- During ground run-up, adjust the throttle to the takeoff position, and note the resultant rpm and manifold pressure.
- If the obtained rpm is higher or lower than the prescribed takeoff rpm, reset the adjustable stop on the governor.
Servicing Propellers
- Propeller servicing involves cleaning, lubrication, and replenishing the operating parts.
Cleaning Propeller Blades
- Cleaning propeller blades should use a clean film of engine oil.
- Clean metal parts with clean engine oil or a suitable equivalent.
Charging the Propeller Air Dome
- Inspect the propeller to make sure it is positioned on the start locks and the proper control is used.
- Charge the piston with dry air or nitrogen.
- Use a temperature-based chart to determine the correct air pressure to charge.
Propeller Lubrication
- Some propeller types do not need lubrication, but others do.
- Follow the manufacturer's procedures, but use caution with any method to avoid damage.
Propeller Overhaul
- A work order must be prepared.
- A process document should be created to record each step of the process
- The records should include applicable ADs, current specifications, and manufacturer's sBs.
- Double-check the serial number and other details for proper accuracy.
Miscellaneous
- Autofeathering System, Unfeathering, and Propeller Auxiliary Systems are mentioned.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
