Seeley Aircraft Service
What is dynamic propeller balancing?
Dynamic propeller balancing is the process whereby an electronic
balancer is used to measure the vibration produced by the aircraft
powerplant. Small trim balance weights are added to the
propeller/crankshaft assembly to correct for errors and reduce the
measured vibration to the lowest level practical. On average, 19 out
of 20 fixed-wing aircraft can benefit from Dynamic Prop Balancing.
Dynamic propeller balancing is the process whereby an electronic
balancer is used to measure the vibration produced by the aircraft
powerplant. Small trim balance weights are added to the
propeller/crankshaft assembly to correct for errors and reduce the
measured vibration to the lowest level practical. On average, 19 out
of 20 fixed-wing aircraft can benefit from Dynamic Prop Balancing.
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How Is "Digital Dynamic Propeller Balancing" Done?
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.
Using ACES digital vibration analyzer equipment.
Performed by a ACES trained A&P mechanic with over 50 years of experience in
maintenance and operation, and is also an owner and pilot.
Tachometer reading to 0.01% accuracy.
Service averages 2-3 hours~while you wait.
Service is mobile and performed at your location.
The engine and propeller combination is balanced
in concert with each other.
Why be concerned with vibration?
Excess and unwanted aircraft vibration can cause discomfort and fatigue for the flight
crew and passengers. The service life of expensive avionics and instruments is
shortened considerably when the equipment is operated in a high vibration
environment. Excess vibration can also shorten the life of expensive engine.
My aircraft runs fine. Why should I have my prop dynamically balanced?
By all means, have your propeller balance checked. 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.
My engine and prop were overhauled recently. Should I have my prop
dynamically balanced?
Both new and used components need to be dynamically balanced. In fact, the best
time to dynamically balance a propeller/engine combination is right after overhaul
when components 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 need to
be dynamically balanced.
What level of propeller vibration is acceptable?
In most cases, the vibration level due to mass imbalance can be brought down to
under .100 IN/S very easily. In the DSS study, the average level seen post-propeller
balance was .039 IN/S. When propeller vibration levels are this low, the operator will
generally see a significant reduction in component wear and fatigue and will find that
the aircraft "feels" like a completely different machine.
In addition to that the mechanic now knows what all of the other engine vibration levels
are (Prop/crankshaft mass imbalance usually dominates them) and can utilize that
information if additional work is needed.
But won't having my propeller dynamically balanced "mask" other engine
problems?
NO! An engine with an internal problem which results in unusual vibration will not
respond to balancing in the same way that an engine which only suffers from mass
imbalance will. A qualified mechanic will use ALL of the information available to make
a judgment about your engine, including the vibration response.
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.
Using ACES digital vibration analyzer equipment.
Performed by a ACES trained A&P mechanic with over 50 years of experience in
maintenance and operation, and is also an owner and pilot.
Tachometer reading to 0.01% accuracy.
Service averages 2-3 hours~while you wait.
Service is mobile and performed at your location.
The engine and propeller combination is balanced
in concert with each other.
Why be concerned with vibration?
Excess and unwanted aircraft vibration can cause discomfort and fatigue for the flight
crew and passengers. The service life of expensive avionics and instruments is
shortened considerably when the equipment is operated in a high vibration
environment. Excess vibration can also shorten the life of expensive engine.
My aircraft runs fine. Why should I have my prop dynamically balanced?
By all means, have your propeller balance checked. 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.
My engine and prop were overhauled recently. Should I have my prop
dynamically balanced?
Both new and used components need to be dynamically balanced. In fact, the best
time to dynamically balance a propeller/engine combination is right after overhaul
when components 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 need to
be dynamically balanced.
What level of propeller vibration is acceptable?
In most cases, the vibration level due to mass imbalance can be brought down to
under .100 IN/S very easily. In the DSS study, the average level seen post-propeller
balance was .039 IN/S. When propeller vibration levels are this low, the operator will
generally see a significant reduction in component wear and fatigue and will find that
the aircraft "feels" like a completely different machine.
In addition to that the mechanic now knows what all of the other engine vibration levels
are (Prop/crankshaft mass imbalance usually dominates them) and can utilize that
information if additional work is needed.
But won't having my propeller dynamically balanced "mask" other engine
problems?
NO! An engine with an internal problem which results in unusual vibration will not
respond to balancing in the same way that an engine which only suffers from mass
imbalance will. A qualified mechanic will use ALL of the information available to make
a judgment about your engine, including the vibration response.
| Here are some frequently asked questions about propeller and rotor balancing. |
4825 Janes Rd
Saginaw, MI 48601
Saginaw, MI 48601
