Module 17.6 Propeller Maintenance Flashcards
What are the three types of balancing?
Static
Dynamic
Aerodynamic
What are static and dynamic imbalances caused by?
Unequal mass distribution
Why is aerodynamic balancing done?
To ensure each blade delivers an equal amount of thrust.
When would dynamic balancing be needed?
With larger or fast moving propellers.
In most cases, what type of balancing is sufficient?
Static balancing
When is a body capable of rotating about a fixed point said to be in static balance?
When its centre of gravity lies on the axis of rotation.
Where is static balancing carried out?
Off the aircraft.
Where is static balance checked?
In the horizontal and vertical planes.
What is dynamic balancing?
Balancing the propeller to reduce the moment of imbalance.
When must dynamic balancing be carried out?
When the engine is running.
What may cause propellers to vibrate?
Different aerodynamic loads of the blades due to the different blade angles.
When is a propeller described as aerodynamically balanced?
When the aerodynamic forces acting on the blades result in no vibrations.
This means that each blade will be producing an equal value of thrust.
Propellers with high performance use what type of balancing?
Aerodynamic
What is blade tracking?
The ability of one blade to follow the other in the same plane of rotation.
Why is tracking held in reasonable limits?
To prevent roughness and vibration.
What are the two methods to check a blades tracking?
Flat bench
Block or Pointer
What does the flat bench tracking method require?
A smooth board placed just under the tip of the lower blade and paper taped to it.
The line should not be separated by no more than ____ during the flat bench method?
3 mm (1/8 inch) or by the measurements designated in the maintenance manual.
What is a blade protractor used to do?
Measure the propeller blade angle at a specific blade station to determine if the propeller is properly adjusted.
Describe the Block or Pointer method?
Place a solid object next to the propeller tip so that it just touches or attach a pointer/indicator to the cowling itself.
What is used when doing a propeller visual inspection?
Touch and other senses, as well as visual cues.
During a visual inspection, what may indicate the propeller isn’t airworthy
Changes in surface roughness, unusual free play, and odd sounds.
What type of material use the tap test?
Composites
What do tap tests look for?
Delaminations and debonds
What is used for the tap test?
A metal coin
What may hint at a delimitation or debond during a tap test?
If an audible change is apparent.
What type of penetrant is used for a Penetrant Inspection?
Fluorescent penetrant
What is Fluorescent penetrant used to do?
Detect small surface cracks on propeller blades.
Who can conduct ultrasonic inspections?
Appropriately certified engineers
How does an eddy current inspection work?
It generates and measures an electric field that detects flaws at or slightly below the surface
How does an ultrasonic inspection work?
Sound waves are used to detect flaws on or below the surface.
What can eddy current inspections be used on?
Ferrous and non-ferrous metals.
What is used to repair damage to wooden propellers?
A wood filler or a mix of sawdust and aero glue (casein).
What would render a wooden propeller unusable?
Cracks in the hub.
When must metal propellers be inspected?
Every 100 hours or at least once a year.
During periodical inspections of a steel propeller, what should the hub be checked for?
Cracks
What are two types of damage on composite propellers?
Skin perforated damage
Skin not perforated damage
What are the two types of skin perforated damage?
Lightning strike
Holes
What would make a composite propeller unacceptable?
Any evidence of a lightening strike on the hub.
How is the power developed by piston engines measured?
Manifold Air Pressure (M.A.P)
What is needed to determine if a turboprop engine is running correctly?
Exhaust Gas Temp (EGT) and Fuel flow against the reference torque and rpm.
