FAQ: MicroVib II Balancing: Rotor Protractor
 

 
  What Is The Rotor Protractor Used For?

The Rotor Protractor is used to identify the proper angle of rotor adjustment locations.

In order for the MicroVib II to learn the behavior of the rotor being worked, the user must provide the exact angle (location) of the adjustment. Therefore, proper use of the Rotor Protractor is crucial.

In order to properly use the Rotor Protractor, the user must accomplish the following steps:

  • Choose the appropriate Protractor side (BLUE or RED) to face the user.
  • Align the 0/360 Pointer with the rotor's phase reference.

Note: Once the protractor has been properly positioned, the user may read adjustment location angles from either side.
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1. How Does The User Choose The Correct Protractor Side?

In order to choose the correct side, the user must observe if the rotor turns Clockwise (CW) or Counter-Clockwise (CCW) from their point of view.

A propeller turns neither CW or CCW, it only moves forward in time. The propeller's apparent direction of rotation is determined soley by the position of the observer.

  • If the propeller appears to turn CCW, then the BLUE side of the protractor should face towards the observer.
  • If the propeller appears to turn CW, then the RED side of the protractor should face towards the observer.

Once the proper protractor side has been determined, double check that the direction of rotation arrows around the circumference of the protractor point in the direction of rotation.

If the above seems confusing, perform the following thought experiment:

  • Imagine the observer stands in front of a propeller looking aft and notes that the propeller appears to turn CCW. The protractor should be used with the BLUE side facing the observer.
  • If the observer changes position and views the propeller from the back looking forward, the propeller will now appear to turn CW and the protractor's RED side will now face the observer.
  2. How Does The User Align The 0/360 Pointer With The Phase Reference?

Once the proper protractor side has been selected, the protractor must be rotated until the 0/360 Pointer aligns with the adjustment location which is closest to the designated phase reference. Depending on the type of rotor, there are different methods of determining the phase reference to be used:
  • If working a propeller, driveshaft, fan, wheel, or tail rotor, treat the Reflective Tape or Interrupter as the Phase Reference.
  • If working a helicopter main rotor, the Target Blade will be the Phase Reference.
 

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