Specializing in Propellor Balancing


PROPELLER BALANCING.

Propellers can become unbalanced during operation from mishandling, wear, damage and a variety of other causes. In some instances, the process of moving an aircraft by pushing or pulling on the propeller blades has bent or unseated the blades to an out-of-track condition or damages the blade preload system. Propeller wear and damage - and the repair of that damage - are also contributors to propeller imbalance. Unauthorized or improper repair of propeller spinners has also been identified as a cause of propeller imbalance.

 

Unbalance results when the mass of the propeller is not symmetrical around the center of rotation. When the mass is unsymmetrical, a radial force and/or out-of-plane moment couple is formed. Static and common dynamic balance procedures only correct the radial force unbalance by adding an equal force in the opposite direction with balance weights. Only trained, specially equipped, and authorized maintenance personnel should accomplish the dynamic balance procedures.

 

     Propellers that cannot be balanced or propellers that are difficult to balance on the aircraft using approved dynamic balancing procedures may have latent problems that should be investigated. Loose components, loose flange bolts, fractured components, such as hubs or blades, or blades that are out-of-track or angle, are some of the more likely problems that will cause balancing difficulties. These are problems that need to be addressed prior to further flight.

 

Balancing Methods. There are two methods of propeller balancing - static balancing and dynamic balancing. Neither method can replace the other because they are used for different purposes.

 

Text Box: Victory’s Dynamic Propeller Balancing

Kregg Victory  408-836-5122                 email:  kregg@balancemyprop.com

Propellers are statically balanced during overhaul and this is a good start.  As most aircraft components are manufactured to strict tolerances. however, test-stand balancing does not compensate for the unbalance caused by the prop spinner, spinner bulkheads, starter ring gear, aerodynamic loading and geometrical manufacturing errors.

If the center of the prop is one one-thousand of an inch out of alignment with the centerline of the crankshaft, this creates a 0.3 IPS imbalance which amounts to a ~40 lb oscillating side load at the front engine bearing.

The residual unbalance is wasted energy which eventually causes cracks and component failures. The repairs are usually costly and since the band aid approach is temporary, vibration continues to take its toll. Vibration also exacerbates pilot fatigue and can cause passenger discomfort and safety concerns.