Helicopter track and balance theory

There are certain flags that may be noticed during the rotor smoothing process that will certainly save you the time and frustration of attempting to correct for a mechanical problem present in the rotor system. For every adjustment on the rotor system, there is an associated influence. For example, the Bell 206 main rotor head balance utilizes approximately 220 grams to correct for a span-wise imbalance of 1.00 IPS. Let's say that in the course of an otherwise normal balance job, you make a very small weight addition of 20 grams and the vibration level changes by 0.5 IPS. The "flag" in this case would be the resulting change in vibration of 0.5 IPS. This much change would, under normal circumstances, require the addition of 110 grams of weight. This should indicate that other factors are involved which may not be correctable by a normal track and balance procedure. Additionally, anytime the maximum corrections or combinations of corrections are applied without acceptable results, the mechanical condition of the systems must be suspect. The outcome is always the same. An aircraft, which is not mechanically sound, will not balance. Track and balance is not a substitute for proper maintenance or a cure-all for mechanical failures.

Finally, don't forget the human factor. If everything seems correct, but you still can't achieve the desired results, consider that you may have made a miscalculation or misadjustment in the process. It is easy enough to return the aircraft to its initial configuration and start over. Your equipment should have recorded the conditions of each run for review and verification. If values are not similar to the original data taken, a mechanical condition may exist which will prevent an acceptable result.