Dynamic Propeller Balancing is the process whereby an electronic balancer is used to measure the vibration produced by the aircraft power plant. Small trim balance weights are added to the propeller/crankshaft assembly to correct for errors in mass distribution and to reduce power plant vibration due to mass imbalance to the lowest level practical.
The engine/propeller combination is balanced right on the aircraft, in a flight ready state. A small vibration sensor (accelerometer) is attached to the engine in a location where vibration due to mass imbalance is maximum. A small tach pickup (photo-tach) is also mounted to the cowl or engine to produce a propeller tach signal. The engine is operated and the vibration and tach signals are processed by the electronic balancer.
The balancer produces a vibration level (magnitude) which corresponds to the amount of mass imbalance which exists. The balancer also provides a "phase angle" which corresponds to the location of the mass imbalance on the propeller disk. The vibration level and phase angle are used to compute a balance solution (weight amount and location). The balance solution is added to the propeller and the measurement is repeated until the vibration level is found to be acceptable.
The average airplane which has not had a Dynamic Prop Balance has a vibration level due to propeller/crankshaft mass imbalance of about .450 inches per second (IN/S) velocity. This level is more than four times higher than what is considered to be an acceptable vibration level for propellers and represents a significantly higher level of wear and fatigue on engine components and accessories. This average level is usually very noticeable to the pilot and occupants. Yours may be higher or lower than the average but only a mechanic with a vibration analyzer can tell for sure. On the average, 19 out of 20 fixed-wing aircraft can benefit from Dynamic Prop Balancing yet many will never have it done.
