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There is nothing more satisfying and reassuring than a smooth running engine. Much of the vibration we feel can be simply eliminated by balancing the propeller. Unlike most aviation procedures prop balance is very simple.

Adding a small weight to the prop spinner or prop hub takes only seconds but makes a big difference. Modern balance analysis equipment reports weight size and location. The term prop balance is a bit misleading because the process treats the rotating mass as a whole including engine imbalance too.

Traditionally helicopter diagnostic tools are used to measure propeller imbalance during a ground run. While widely accepted and better than nothing, this approach is flawed. I discovered first hand how important prop balance was at the Hartzel Factory. Not just any balance but balance done in flight.

The process involved temporarily installing various sensors and pickups and taping numerous wires to the airframe.

The technician carefully tuned the balance of the 8 ft diameter 4 blade props on my MU-2 on the ground first, to a reading below .1 IPS (inches per second). This is a good low reading by any standards.

From the front seat it felt very smooth. Moments later in a cruise flight test the reading grew to an annoying .4 IPS.

Even at identical RPM the flight and ground tests were significantly different. Aerodynamic loads, blade pitch angle and other in motion factors result in a vastly different balance solution.

Upon landing another adjustment was made based on the in flight readings.

The second test flight was shocking, I could not believe the difference. It was like leaving the props and engines behind. I was so enamored by the result I installed the sensors for helicopter balance gear in the airplane permanently.

By periodically checking and tuning prop balance I have always enjoyed the smoothest possible flight experience.

The new GEM Prop Balance function provides the best possible balance information on a dedicated screen without the hassle of a temporary setup.

So you can check it anytime.

Balance has diagnostic value and is good detector of prop ice too.

I hope everyone will take advantage of the amazing in flight balance procedure.

Here's one of my favorite ways of balancing a prop in-flight.