17.6* Flashcards
What are the three different types of balancing?
. Static
. Dynamic
. Aerodynamic
What are static and dynamic imbalance caused from?
Caused by unequal mass distribution
Why do we aerodynamically balance?
To ensure each blade delivers an equal amount of thrust
What type of propeller needs all 3 types of balancing?
Large props or fast running props
Where is static balancing carried out?
Off the aircraft either at the manufacture, overhauled or approved prop repair facility
How would you correct horizontal imbalance on a wooden prop?
By applying small amounts of varnish or paint to the light blade
How is vertical imbalance corrected on a wooden props?
By adding weights to the hub
How would you statically balance a metal pitch prop?
By removing metal from the heavy side and then putting non anodic protective coating on
For aircraft up to 5700kg what is the permissible tolerance?
2gm
For minor balance adjustments on a metal or composite pitch prop what can be done?
Place lead wool into the balancing tube located within the hollow root of the blade
When must dynamic balancing be carried out?
On a running engine
Do small props need dynamically balancing?
No because any shift of centres of gravity is only small
What type of props is aerodynamic balancing only necessary on?
Props with high performance
After aerodynamic balancing where is the correction factor marked?
In the blade root
What do we use the universal blade prop tractor for?
To measure the prop blade angle at a specific blade station to determine if the prop is properly adjusted
On the universal blade protractor, what is the ring engraved with?
With index marks which allow readings as small as one tenth of a degrees
What is blade tracking?
The ability of one blade to follow the other in the same plane of rotation
When doing blade tracking, what should be distance of lines be?
No more than 3mm - if more then indication of bent blades
What are the two types of blade damage?
Airworthy and unairworthy
When examining a wooden prop what must you ensure?
That it is 100% intact so no moisture can penetrate it
Less significant damage to the trailing edge on a wooden prop can be corrected how?
By filling it with plastic
After installation of a new wooden fixed prop what must happen?
. The attachment bolts must be re tightened after 25 hours with the torque prescribed,
. Then after after the initial re tightening the torque must be checked at least every 50 hours as humidity will cause the wood to shrink and expand
What are metal propellers partially subject too?
Metal fatigue
Can you repair anything at the blade root?
No, no repair is permissible on the blade root
