1. Rotor Track and Balance.

2. Overview Rotor Balance Types of Balance Equipment Installation
Data Acquisition and Making Adjustments
Troubleshooting

3. Rotor Balance What is an imbalance? Advantages and disadvantages
Causes of imbalance
Other sources of vibration

4. Rotor Balance What is an imbalance?
A condition where there is more weight distributed on one side of a rotating component than on the other side

5. Rotor Balance Advantages
Simple
Cost efficient
Cost effective

6. Rotor Balance Disadvantages
Noise
Vibration

7. Rotor Balance Causes of Imbalance
Manufacturing tolerances
Shimming and alignment
Rotor track
Static track
Dynamic track

8. Rotor Balance Rotor Track
Static track
Perfect track if all blades produce the same lift
Assumes that blade twist, profile, and stiffness are equal on all blades
Assumed then to give equal lift on all surfaces of the blade

9. Rotor Balance Rotor Track
Dynamic track
How the rotors fly during operation
More important to sacrifice a perfect tip path track for a rotor that is perfectly balanced

10. Rotor Balance Other Sources of Vibration
Mechanical looseness
Misalignment
Track
Worn bearings

11. Types of Balance Dynamic track and balance Purpose of balancing
Types of imbalance

12. Types of Balance Dynamic Track and Balance
First introduced in the late 1950’s
Operators found that virtually all statically balanced rotors were out of balance dynamically when installed.

13. Types of Balance Purpose of Balancing
Static
Knife edge
Suspended arbor
Bubble balance

14. Types of Balance Purpose of Balancing
Dynamic
Performed during operation
All of the rotating components are balanced as an assembly

15. Types of Balance Types of Imbalance
Mass imbalance
Distribution of the mass
Spanwise or chordwise
Aerodynamic imbalance
Out-of-track condition exists

16. Types of Balance Benefits to Dynamic Balance
Enhance comfort
Reduce wear
Increase safety by reducing component stress
Lower operating costs

17. Equipment Sensors Tach sources Vibration measurements
Amplitude and phase

18. Equipment Sensors
Accelerometers
Displacement sensors
Velocity sensors

19. Equipment Accelerometers
Measure acceleration
Typically reported in g’s
More sensitive to higher frequencies
Directly related to force caused by unbalance
Used in balancing (after conversion to velocity or displacement)

20. Equipment Displacement Sensors
Measure change in position
Typically reported in mils (.001 of an inch) peak to peak
More sensitive to Low frequencies
Directly related to movements due to imbalance
Seldom used in balance (however, displacement units are often used)

21. Equipment Velocity Sensors
Measure velocity
Typically reported in IPS peak
More sensitive to medium frequencies
Directly related to energy from imbalance
Often used in balance

22. Equipment Sensor Construction
PEDESTAL
PIEZOELECTRIC
ELEMENT IN
COMPRESSION
SEISMIC MASS
OUTPUT CONNECTOR
AND AMPLIFIER
BASE
PRELOAD
SCREW

23. Equipment Tach Sources
Magnetic pickup
Phototach

24. Equipment Magnetic Pickup

25. Equipment Phototach

26. Equipment Vibration Measurements
Amplitude and phase
Correlation between the trigger of the tach source and the time until the sensor registers the maximum amplitude.
The result will be a phase angle in degrees or time (clock angle)

27. Installation
Sensor
Tach Source
Tip Targets

28. Installation Sensor

29. Installation Tach Source

30. Installation Tip Targets

31. Installation Optical Tracker
Optical devices obsolete tip targets

32. Data Acquisition and Making Adjustments
Polar plotting
Automated solutions
Rotor track and balance
Rules

33. Data Acquisition and Making Adjustments Polar Plotting
IPS and phase values are taken from the analyzer and manually plotted on charts to obtain a correction.

34. Data Acquisition and Making Adjustments Automated Solutions
The analyzer is used to collect the phase and IPS readings then calculates a solution
The calculated solution is then implemented by the user eliminating manual calculations

35. Data Acquisition and Making Adjustments Rotor Track and Balance
Pitch links
Tab
Sweep
Tip weight
Hub weight
Blade chordwise weight

36. Data Acquisition and Making Adjustments Pitch Links
Changes the lift of the blade by adjusting the angle of attack at the rotor hub
Characteristically changes the tip path plane throughout speed range
Characteristically has large drag changes resulting in a strong effect on lateral balance

37. Data Acquisition and Making Adjustments Tab
Changes the lift of the blade by adjusting the twist in the blade aerodynamically
Characteristically changes the tip path plane at higher airspeeds
Characteristically has small drag changes resulting in little affect on the lateral vibrations

38. Data Acquisition and Making Adjustments Sweep
Changes the balance of the rotor head by adjusting the center of mass
Characteristically changes the mass at all air speeds
Characteristically it has little effect on the lift of the rotor and the vertical vibration

39. Data Acquisition and Making Adjustments Tip Weight
Changes the mass of the rotor head by adjusting blade weight
Characteristically no change to tip path plane
Characteristically has a large effect on lateral vibration

40. Data Acquisition and Making Adjustments Hub Weight
Changes the mass of the rotor by changing rotor head mass
Characteristically has large effects on the lateral vibration
Characteristically has no effect on tip path plane

41. Data Acquisition and Making Adjustments Blade Chord Weight
Changes the center of gravity of the blade
Characteristically changes tip path with changes in collective force
Characteristically has large effects on verticals
Characteristically has large effects on laterals at ground/hover and in letdowns

42. Troubleshooting Polar Plotting - Human error Worn components
Structural resonance

43. Troubleshooting Polar Plotting
Human Error
The result of an adjustment increases the IPS or the moveline 180 degrees out

44. Troubleshooting Worn Components
A specific vibration level is achieved and continued adjustments result in IPS levels that do not change and phase angle walks around the chart.
A large amount of weight added to a location results in no change in IPS or phase

45. Troubleshooting Structural Resonance
Unrepeatable reading
Adjustments result in varying results
Phase angles and IPS levels are very erratic and unpredictable when known good solutions are implemented.

46. Contact