17.6 - Propeller Maintenance Flashcards
How should a defect on the leading or trailing edge of an aluminium propeller be dressed out and at what angle shold it be sanded?
Damaged area on the leading or trailing edge should be blended x10 times the depth of defect
What is tracking a propeller?
The track of the propeller is defined as the path which the tips of the blades follow as they rotate with the aircraft stationary
(metal prop = 1/16 inch)
(wooden prop = 1/8 inch)
How is a propeller blade tracked?
Rotate the propeller by hand until one blade is pointing down at the paper, and mark this position on the paper. Now turn the propeller so that the track of the next blade can be marked on the paper, and repeat this for each blade. The maximum difference in track for all of the blades should not exceed the limits mentioned above.
(metal prop 1/16 inch)
(wooden prop 1/8 inch)
How is static balancing carried out, tool used and what is it?
suspension method or knife-edge method
mandrel used
Propeller static unbalance occurs when the centre of gravity of the propeller does not coincide with the axis of rotation. (static inbalance = not going in axis of rotation)
What is dynamic balancing and what is needed to carry it out (tools)?
Dynamic unbalance results when the centers of gravity of similar propeller elements, such as blades or counterweights, do not follow in the same plane of rotation.
Piezoelectric accelerometer (mounted on the engine or gearbox as close as possible to the propeller)
How is dynamic balancing carried out?
If a rotating disk is perfectly balanced, no vibration will be passed on to the supporting structure.
device needed to convert vibration into a measurable electronic signal => piezoelectric accelerometer
A photo cell, magnetic pickup or strobe light for sensing the angular position of the propeller; and an electronic instrument for fitting to convert vibration into measurable electronic signal
