Q: I’ve heard balancing can mask other problems in the engine. Is that true?

 A: No. In fact, there are very sound physical reasons you cannot balance something that has inherent faults. In addition, a balance that incorporates a vibration survey often identifies other vibrations that can pinpoint engine or airframe vibration. There are some cases where balancing outside the plane of the imbalance will cause a dynamic couple that makes the balance at the rear of the engine worse, and there are cases where blade angle (an aerodynamic imbalance) should be corrected first. Both cases are relatively easy to identify by an experienced  trained individual.

Q: Are holes drilled in the Spinner bulkhead?

 A: Seldom and only when necessary.  Some manufacturers provide holes pre drilled in the backing plate for trim balance. Other manufacturers endorse drilling the backing plate. Sadly, the poor work of others often needs to be remediated.  Under no circumstances are the washers to be left on the outside of the spinner as a permanent installation. Stick on weights are also forbidden – not to mention unsafe.

Q: I’ve heard you need to run the engine and prop a while after overhaul before you balance.

A: The concern here is not with the breaking in of the propeller. It will be as good as it will be from day one. The concern is with break in of the engine. The runs are done at moderate power settings, not hard enough to help seat the rings, and the lack of airflow is enough to cook not yet broken in cylinder bores. As soon as the engine oil consumption and temperatures have stabilized, it’s OK to proceed with the balance.  It is really more of a “be kind to your engine” issue.

Q: Can wood and metal fixed pitch props be balanced?

A: Every prop can benefit from a good dynamic balance. It doesn’t matter if it is wood, metal, fixed pitch, composite, 2,3,4,5,or 6 blade. Wood props are a little unique in that they should be flown and hour or two in the week previous to balancing to work out any moisture. Wood props are some of the best “out of the box” regarding balance – and some of the worst.

Q: Do you work on experimental and part 135 aircraft?

A: Of course. I’ve been a homebuilder (plans built) in the past, and helped some of the manufacturer’s with their installations on aircraft that are used for Part 135, mostly turboprop.

Q: Do you stand in front of the airplane to balance?

A: Only an idiot would stand in front of a propeller pulling power. I’m not an idiot. Most times I’m in the airplane.

Q: Can you take readings in flight?

A: This is part and parcel of helicopter main rotor smoothing. It can be done on fixed wing as well, usually for troubleshooting airframe or engine/airframe interface issues.