wrote:

I have checked the vibe level in-flight on numerous occasions, on
aircraft that acted "strange" after a standard dy-bal.

How do you get the wire from the accelerometer/position pickup into the
cabin during flight?

The newer balancing equipment can log the vibe signature through a
wide frequency range and is useful in these cases also. The older CH
spectrum analyzer could also do a survey of a range of frequencies.

Since the only place that you can put a weight is on the prop spinner
backing plate, can Prop balancing do anything except cancel the "first
order" mass imbalance (usually called a "static" balance)?

Wouldn't you have to have access to the other end of the crankshaft to
add weights there in order to be able to do a true multi dimensional
"dynamic balance"?

I'm not trying to be argumentative; just trying to understand the claims
made by the purveyors of prop balancing services.

It would seem to me (and forgive me, it's been a few years) that on a
constant-speed propeller that achieving cruise rpm is quite do-able.
I'm thinking that we useta set the rpm approx. 100 rpm over the
desired "cruise" setting using the throttle, and retarded it using the
prop control.

I have wondered that during a ground run, doesn't the buffeting caused
when the prop tip swings within a couple of inches of the ground induce
wierd vibrations in the moving propeller that might not be there if
the prop where swinging in free air? In other words, wouldn't it be
preferrable to record vibration data during an actual flight, and
then postprocess it into a "where and how much weight" solution later?

A proper dy-bal job performed by a knowledgeable technician is a
decent value. We did all the company aircraft mainly because we owned
the box...

What is a typical charge for this service?

Thanks,

MikeM