FAQ: MicroVib II Balancing: Proposed Solutions

 

 

After the MicroVib II has collected Balance Readings, a Proposed Balance Solution, consisting of suggested adjustments, is computed and displayed. This solution is affected by several parameters.


  1. MV2 Proposed Balance Solution

Every MicroVib II Proposed Balance Solution is computed based on the following parameters:

  • Current Balance Readings
  • Current Aircraft Factors
  • Current Rotor Geometry

The Proposed Balance Solution that the MicroVib II presents is computed from the current Balance Readings in conjunction with the current Aircraft Factors (Influence Coefficients). The balance solution is then modified based on the Rotor Geometry

If you have set your MicroVib II up with Aircraft Factors which match your aircraft, then the solution presented after collecting a new set of Balance Readings will be appropriate to balance your machine.

If you have not set up the MicroVib II with Aircraft Factors which are appropriate for your aircraft, then the first solution may not be optimum. In this case, the vibration might improve somewhat with the implementation of the first Proposed Balance Solution, but the balance job may not be finished. When this is the case, the operator can take advantage of the MicroVib II's unique learning feature and utilize a more appropriate Proposed Balance Solution after the Run 2 measurement has been collected.


H 2. How Accurate Is My Proposed Balance Solution?
 
People reading MicroVib II operating instructions will find that DSS recommends the MV2 learning feature remain turned on for most balance jobs. Additionally, they will find that DSS refers to the changes made to the rotor balance as "trial" adjustments. From this the reader will sometimes erroneously assume that the first solution is somehow not appropriate and that they must throw away a run before balancing can begin. This is not generally correct, however as noted above, the appropriateness of the Proposed Balance Solution is dependant upon how well the current MicroVib II's setup matches the behavior of the machine under test.

 

3. How Can Less Than Optimum Setup Affect My First Proposed Solution?

Imagine performing prop balancing on a new aircraft. The default aircraft factors contained in the prop.grp file are:

  • Weight Sensitivity = 80 gm/ins (this is an average of many different fixed wing aircraft)

  • Tach Offset = 90 degrees  (this is the recommended Accelerometer to Photo-Tach installation offset of 90 degrees).

Weight Sensitivity Variance: A Piper Cub might have a sensitivity of 40 gm/ins and a Beech King Air might have a sensitivity of 120 gm/ins. Therefore, when using the default Aircraft Factors shown above, the initial Proposed Balance Solution would be larger than optimum for a Piper Cub and smaller than optimum for a Beech King Air.

Tach Offset Variance: The default setting for the Tach Offset above assumes the recommended installation relationship of 90 degrees between the Accelerometer and the Photo-Tach activation point. If you install your sensors with a 45 degree T/O, then your move will miss by about 45 degrees, and so on.

A less than optimum setup and the solution that follows is perfectly normal given that very often we will balance aircraft for which the ideal Aircraft Factors are not yet known.
 


  4. How Are Later Proposed Solutions Different From The First?

Once the MicroVib II has an oportunity to "learn" the behavior of the machine under test, the Aircraft Factors will be re-computed and a Proposed Balance Solution will be presented that is ideal for the machine under test.


 

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