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But, there are still a few areas where a little extra knowledge helps out. One of those was brought to my attention by one of our valued customers, Mr. Ben Baker of Baker Flying Service. The situation he brought up is this:

When using a propeller balance setup for the first time, the analyzer directed that a test weight be added after the first run. The test weight was too much even for two screws according to the limits written in the ACES Guide to Propeller Balancing. What do you do?

The "test weight" is added to induce a change in the vibrating condition of the prop and engine assembly, nothing more. It is not intended to be a final solution for the balance job and in fact may make the vibration amplitude rise. This is not unusual and it’s important to remember that all we want to do here is induce a change so that the analyzer can measure and compare that changed condition with that collected on the initial run. The analyzer, according to the information you entered in the setup, calculates the amount of the test weight. Horsepower is a key player in the calculation which is ((Engine Horsepower/10)+30)x IPS. In a high horsepower engine and high IPS reading condition, this calculation may return some pretty hefty weight recommendations. Remember that an IPS reading in excess of 1.25 IPS requires that the propeller be removed and statically balanced. The limit in the ACES Guide to Propeller Balancing, 30 grams per screw, is established by the FAA and should be followed as closely as possible.

For example, let’s say the analyzer tells you to add 75 grams at 360 degrees. That’s far too much for a single screw. The obvious solution is to split the weights, which you can do by pressing the F1 (Split Weights) key. The analyzer will then ask you to enter the two available angles. For this example, we might say 350 and 10. The analyzer might then tell you, as an example, to add 36 grams @ 350 and 36 grams @ 10. This still exceeds the 30 grams per screw limit. Remember that all we hope to accomplish here is a change. Disregard the suggested weight and install the 30 grams per screw maximum so as not to exceed the limits. The important thing then is that you enter the exact amount of added weight and its location back into the analyzer. Complete the next run and the analyzer will calculate an influence, which is then used to provide you with a vibration reducing solution. When that solution is shown, try to apply it as near to the weight and angle as possible. This is the solution that should show positive improvement in the vibration condition. The influence is then stored in the setup and the next job will present you with a reasonable first weight, which may even be the final one.

If you have questions about any the procedure, call ACES Systems' Product Support.

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