Dynamic propeller balancing a process whereby an electronic balancer is used to measure the vibration produced by the aircraft engine. Small trim balance weights are added to the propeller / crankshaft assembly to correct for errors and reduce the measured vibration to the lowest practical level. On average, 19 out of 20 fixed-wing aircraft can benefit from Dynamic Propeller Balancing.
In a flight ready state, the engine and propeller are balanced right on the aircraft. A small sensor called an accelerometer that measures vibration is attached to the engine, and a tach pickup (called a photo-tach) is 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)also provides a "phase angle" which corresponds to the location of the 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.
My aircraft runs fine.
The average airplane has a vibration level due to propeller / crankshaft mass imbalance of about .450 inches per second (IN/S) velocity which is more than four times higher than what is considered to be an acceptable vibration level. This average level is usually noticeable to the pilot and occupants. Your aircraft may be higher or lower than the average but only a mechanic with a vibration analyzer can tell for sure.
New or used, they need to be dynamically balanced, and actually, the best time to do this is right after overhaul when the everything is are fresh. In the DSS study, no appreciable difference was found between the vibration levels of recently overhauled and longer time propeller/engine combinations. Even brand-new aircraft with zero time engines and propellers should to be checked to see if they are dynamically balanced.
Why should I be concerned with vibration?
Aircraft with unwanted or excess vibration can cause discomfort and fatigue for the flight crew and passengers. Unwanted or excessive vibration can also shorten the life of your avionics and instruments, along with shortening the life of your engine.
An engine that might have an internal problem resulting in unusual vibration will not respond to balancing in the same way that an engine which only suffers from an imbalance will. Our qualified mechanics will use every bit of the information available to him regarding your aircraft to make a judgment about your engine, including the vibration response.
Call Kurt Singer, Director Of Maintenance to discuss further