Propeller Maintenance Flashcards
What are the 3 types of propeller balancing? What is imbalance caused by?
Static balancing and dynamic balancing - unequal mass distribution. Aerodynamic balancing - unequal amount of thrust
What is dynamic balancing? When is this done? After checking vibration levels what is installed to reduce vibration?
Balancing the propeller to reduce the moment of imbalance. Engines running. Balance weights
How can you tell if a body is in static balance? Where is static balancing carried out? What 2 planes is the balance checked in?
Each time the blade is rotated it comes to a stop in a random position. Off the a/c. Horizontal and vertical
What propellers must be aerodynamically balanced? What is the process called?
High performance propellers. Blade indexing
How do you tell if a blade is aerodynamically balanced for torque? Thrust? What does ACF stand for?
ACF Q. ACF T. Aerodynamic correction factor
What is a universal blade protractor? What is the smallest reading it can take? What must be determined before measuring the angle of a propeller blade?
Measure the propeller angle at a specific blade station. 1/10 degree. Reference blade station
What is blade tracking? What does it prevent?
Ability of one blade to follow to follow the other in the same plane of rotation. Roughness and vibration
Where measurement for blade tracking taken from? How do you tell if the track is not within limits?
Master station. Difference between highest and lowest readings between blade and pointer is within specific tolerance stated in AMM chapter 61
What are the 2 main methods used to check a blades tracking?
Flat bench method and block or pointer method
What do you use to carry out the flat bench tracking method? Wha it’s the maximum separation of the lines?
Requires a smooth board placed just under the tip of the lower blade and paper taped to it. 3mm or refer to AMM
How do you carry out the block or pointer tracking method? What is the tolerance?
Place a solid object next to the propeller blade tip then rotate blades slowly to determine if the next blade tracks through the same point. +-1/16 inch
What can damage to a propeller be divided into? What is the difference?
Airworthy damage - can be repaired in the field. Unairworthy damage - damage that exceeds the limits of airworthy damage
Does airworthy damage affect flight safety characteristics of the blade? What do you use to check if damage is airworthy?
No. Blade repair manual
What do you use for a tap test? What are you inspecting for? What type of blades is it used on?
Metal coin. Delaminations and debonds. Composite
What type of blades is eddy current inspection used on?
Ferrous and non ferrous
What is penetrant inspection used for detecting? What is the best penetrant to use?
Cracks. Fluorescent
Who can conduct ultrasonic inspections?
Appropriately certified engineers
Where is a magnetic particle inspection carried out? What type of damage is it used to find? What type of blades is it used for?
Appropriately approved maintenance facility. Cracks, inclusions and imperfections. Ferrous blades
Where is blade failure most common? Where can you find additional guidance on blade damage?
Tip region. Manufacturers service documents
What are the 3 types of corrosion on metal propeller components? What are they? How are they identified?
Surface corrosion - loss of surface metal due to chemical or electro-chemical action with visible oxidation products, contrasting colour to base metal. Pitting - visible corrosion cavities extending inward from metal surface. Intergranular corrosion- continued moisture presence or where pain protective barriers have been lost. ,teal falling or leading edge cracks
Are wood and composite propellers susceptible to corrosion?
No
What are cracks in the paint across the blade a sign of on wooden propellers? What is the urgency?
Flexural vibration. Tipping replaced immediately
What are loose rivets on the tipping a sign of on wooden propellers? What is the urgency?
Wood beneath is damaged. Propeller removed from service immediately
How can surface damage to wooden propeller blades be repaired?
Using wood filler or a mix of sawdust and aero glue
Are repairs permitted on a wooden blade if the root/shank is damaged?
No
How often should a metal propeller be inspected for damage?
Every 100hrs
How much bigger should the leading and trailing edge be compared to the depth of the nick? How much bigger should the blade face and back be compared to the depth of the nick?
10x. 30x
Why must all repairs to steel propellers be performed at an approved repair facility?
All repairs are major as steel is brittle
Is anything above the graph line on a bend chart repairable? What do you do if you don’t have access to a chart?
No. Contact an overhaul facility for a decision before sending the propeller for straightening
What are grease leaks a sign of when inspecting the hub? What are oil leaks a sign of when inspecting the hub?
Damage to blade attachment seals. Damage to seals in pitch change cylinder or damage to blade attachments
What must the hub be inspected for? What can be sprayed to the hub after cleaning as corrosion protection?
Cracks and corrosion. Lubricant spray
Can a propeller hub be repaired if there are signs of a lightning strike? Do you have to replace the entire propeller?
No. Yes
What are static checks? When are they carried out?
Checks carried out without the engine running. Before an engine run
What is MAP (Manifold Air Pressure)? What type of a/c is MAP specific to?
Power developed is related to air pressure in engine air induction manifold. Piston engines (supercharged engines)
How do you check a reference RPM? How do you carry out a reference power check?
Carry out a reference power check. Set propeller to fine pitch, advance throttles until manifold pressure reads 0 then check that RPM matches the reference RPM
If engine throttle advances and RPM increases what happens to MAP and overall performance of the engine?
Increases
When do fixed pitch propellers not attain max RPM? Why?
If nil wind conditions. Prevent overspending during takeoff
What is monitored to ensure the engine is running correctly for a turboprop engine?
Exhaust Gas Temp and Fuel Flow
What does a piston engine use to determine RPM? What does a turboprop use to determine RPM?
Boost pressure. Produces a selected RPM for a given torque
At what temp must the air inlet icing be turned ON to prevent moisture?
Below 10 degrees
What direction should an engine be facing for an engine ground test?
Into the wind
