Product Tip of the Month May 2000

Product Tip of the Month

May 2000

All Analyzers

Balance Speeds

A common question the ACES Systems' customer support team has been hearing lately concerns balance speeds. There seems to be a common misconception that balancing should be done at the fastest speed the propeller or fan runs. That isn’t always the best advice, but it does have merit at times. The balance speed you select to use also depends on what type of analyzer you are using. The following are guidelines for choosing balance speeds.

Models 1000, 1010, or 2020 ProBalancers

Low cost units designed primarily for propeller balance are limited to a single-speed balance. In choosing which speed that should be, consider the following.

If the owner or operator of the aircraft reports vibration and noise a particular speed, then balancing at that speed will resolve the complaint. This, however, does not always produce the most desirable condition. Tell the customer that balancing at the speed of complaint will no doubt reduce the noise and vibration at that speed, but might actually worsen the same vibration and noise condition at other speeds.

The best speed for balancing with the single-speed limitation is a low-cruise power setting. This is the condition the engine and propeller will most likely be functioning in for the majority of time. If the vibration and noise is at its lowest point in this speed range, the passengers will experience the most comfort for the longest period of time. Overall, it’s a good trade off for one minute of higher vibration and noise at take-off or climb power.

Remember that you can only balance at one speed with these balancers, so choose the one that will give you the most bang for the buck. If the owner/operator wants a smooth, quiet propeller at maximum power, explain to him that you can provide that, but the resulting possible increase at other power settings might be a less desirable condition for him. Armed with that information, let him make the decision and then provide the service at the speed of his choice.

1700 Series and 4000 Series Analyzers

Most fan trim balance procedures provide the means to balance at multiple speeds. Three speeds are most common, but some procedures allow for up to nine speeds. Balancing at multiple speeds provides the most desirable conditions for multiphase (take-off, climb, and cruise) operation.

A single-speed balance is a trade off of higher vibration at other speeds for quiet and smooth at one speed in most cases. It’s like having five 10 oz. glasses and 25 oz. of water that must be contained within the five glasses. You can fill two glasses to capacity, one to half capacity, and have the remaining two empty. If the goal is pick up any one of the glasses at random and have a refreshing drink, would this be the best distribution of the water?

The multi speed balance distributes the vibration and noise over the full, in-flight engine speed range. The comfort at any one speed is not sacrificed to make the already acceptable vibration and noise level at another speed even better. Balancing at multiple speeds configures the engine to share the vibration and noise burden over all operational speeds and offers the best environmental and mechanical conditions.

If your procedure offers multiple speed balancing, ACES Systems recommends you use at least three. The time required to gather data is only slightly higher and the payback is well worth the time, effort, and gas expended.

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