Module 17.6 Propeller maintenance Flashcards
When working with propellers three different types of balancing are of importance, what are these?
- Static
- Dynamic
- Aerodynamic
What are static and dynamic imbalances caused by?
Unequal mass distribution
Why is aerodynamic balancing done?
Ensure each blade delivers the same thrust
A body is in static balance when?
Centre of gravity lies at the centre of rotation
Static balance is checked in what planes?
Vertical and horizontal
Where is static balancing done?
Off of the aircraft
What is dynamic balancing?
Balancing the moment to reduce the moment of imbalance
How is the dynamic balancing checked?
While the engine is running
When is an object in aerodynamic balance?
When the aerodynamic forces acting on the blades result in no periodic vibrations in the mountings. This means each blade will produce equal thrust
What does vibration caused by the blades being unbalanced aerodynamically get worse with?
Becomes worse with increasing pitch and thrust
Aerodynamic correction factor is either done for what?
Thrust or torque
What will the blade be marked with for ACF, thrust and torque?
Thrust - T
Torque - Q
Aerodynamic balancing is only necessary for what propellers?
High performance
What is the universal blade protractor used to determine?
Used to measure the angle to a reference station. Done to ensure all blades are properly adjusted
Where is the reference station usually?(Universal Blade Protractor)
30 inch, 36 inch, 42 inch
What is blade tracking?
Ability of one blade to follow the other in the same plane of rotation
What are the two methods for checking blade tracking?
- Falt bench method
- Block or pointer method
How far should the pencil lines be apart in the flat bench method?
3mm
What should the tracking separation be in the block or pointer method?
+- 1/16 inch
Airworthy damage limits are described where?
Within AMM chapter 61
What methods can be used for inspecting the blades for damage?
- Visual
- Tap
- Dye penetrant
- Ultrasonic
- Eddy current
- Magnetic particle
The use of what dyes is not recommended?
Visible dyes
What 3 categories can the corrosion on the blade be classified into?
- Surface
- Pitting
- Intergranular
What are composite and wood propellers susceptible?
Delamination
Cracks in the paint are signs of what?
Flexural vibration
Less significant damage on the trailing edge or on the blade of wood propellers can be filled with what?
Plastics
How often should blades be inspected?
Every 100 hours or at annual check
How must nicks be repaired?
Blending
How much must the blend be on the TE and LE?
10 x depth of nick for the leading and trailing edges
How much must the blend be on the blade face and back?
30 x the depth for the blade face and back
What must the hub be checked for periodically?
Cracks and corrosion
Damage on composites is classified as what?
Acceptable or unacceptable
Sub-classification of damage may also be sub-divided as what?
- Skin perforated damage
- Skin not perforated damage
What pump is used to carry out static checks?
Electric feathering pump
What are some static checks?
- Flight Fine Pitch Stop (FFPS)
- Auto-coarsening
- Manual Feather
- Autofeather
- Unfeather
When are static checks usually carried out?
Prior to an engine ground run
What is the benefit to static checks?
The engine does not need to be run
Piston engines were further classified as what?
Normally aspirated and supercharged
The air pressure in the engine air induction manifold is known as what?
Manifold Air Pressure
How is the reference RPM checked?
Setting the propeller to a fine pitch, advancing the throttle until the manifold pressure reads zero boost
What is the reference RPM?
The RPM when it reaches 0 boost
What way should the aircraft face during an engine test?
Into the wind
Below what temperature must the anti-ice be on?
10℃
Turboprop engine power is measured in what?
Shaft horsepower
To determine that the engine is operating correctly then the engine exhaust gas temperature (EGT) and fuel flow (FF) must be monitored against the referenced what? (Piston)
Torque and RPM
What two pieces of formation are required to correct a propeller dynamic imbalance?
Vibration level and phase angle
What is the purpose of the steel wire mesh?
Inhibit blade tip erosion
When airspeed increases what happens to the brake moment?
Brake moment decreases
What does ACF stand for?
Aerodynamic Correction Factor
Where do fatigue failures occur?
Few inches from tip
