HelicopterRTB

1.

Rotor Track and
Balance
Product Support
ACES Systems/TEC Aviation Division
support@acessystems.com
06/06/2011 #1

2. Overview

Rotor Balance
Types of Balance
Equipment
Installation
Data Acquisition and Making
Adjustments
Troubleshooting
06/06/2011 #2

3. Rotor Balance

What is an imbalance?
Advantages and disadvantages
Causes of imbalance
Other sources of vibration
06/06/2011 #3

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
06/06/2011 #4

5. Rotor Balance Advantages

Simple
Cost efficient
Cost effective
06/06/2011 #5

6. Rotor Balance Disadvantages

Noise
Vibration
06/06/2011 #6

7. Rotor Balance Causes of Imbalance

Manufacturing tolerances
Shimming and alignment
Rotor track
Static track
Dynamic track
06/06/2011 #7

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
06/06/2011 #8

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
06/06/2011 #9

10. Rotor Balance Other Sources of Vibration

Mechanical looseness
Misalignment
Track
Worn bearings
06/06/2011 #10

11. Types of Balance

Dynamic track and balance
Purpose of balancing
Types of imbalance
06/06/2011 #11

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.
06/06/2011 #12

13. Types of Balance Purpose of Balancing

Static
Knife edge
Suspended arbor
Bubble balance
06/06/2011 #13

14. Types of Balance Purpose of Balancing

Dynamic
Performed during operation
All of the rotating components are balanced
as an assembly
06/06/2011 #14

15. Types of Balance Types of Imbalance

Mass imbalance
Distribution of the mass
Spanwise or chordwise
Aerodynamic imbalance
Out-of-track condition exists
06/06/2011 #15

16. Types of Balance Benefits to Dynamic Balance

Enhance comfort
Reduce wear
Increase safety by reducing component
stress
Lower operating costs
06/06/2011 #16

17. Equipment

Sensors
Tach sources
Vibration measurements
Amplitude and phase
06/06/2011 #17

18. Equipment Sensors

Accelerometers
Displacement sensors
Velocity sensors
06/06/2011 #18

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)
06/06/2011 #19

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)
06/06/2011 #20

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
06/06/2011 #21

22. Equipment Sensor Construction

OUTPUT CONNECTOR
AND AMPLIFIER
PRELOAD
SCREW
SEISMIC MASS
PIEZOELECTRIC
ELEMENT IN
COMPRESSION
BASE
PEDESTAL
06/06/2011 #22

23. Equipment Tach Sources

Magnetic pickup
Phototach
06/06/2011 #23

24. Equipment Magnetic Pickup

06/06/2011 #24

25. Equipment Phototach

06/06/2011 #25

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)
06/06/2011 #26

27. Installation

Sensor
Tach Source
Tip Targets
06/06/2011 #27

28. Installation Sensor

06/06/2011 #28

29. Installation Tach Source

06/06/2011 #29

30. Installation Tip Targets

06/06/2011 #30

31. Installation Optical Tracker

Optical devices obsolete tip targets
06/06/2011 #31

32. Data Acquisition and Making Adjustments

Polar plotting
Automated solutions
Rotor track and balance
Rules
06/06/2011 #32

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.
06/06/2011 #33

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
06/06/2011 #34

35. Data Acquisition and Making Adjustments Rotor Track and Balance

Pitch links
Tab
Sweep
Tip weight
Hub weight
Blade chordwise weight
06/06/2011 #35

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
06/06/2011 #36

37. Data Acquisition and Making Adjustments Pitch Links

Eurocopter SA330 Puma
AW139
AgustaWestland
06/06/2011 #37

38. 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
06/06/2011 #38

39. Data Acquisition and Making Adjustments Tab

Eurocopter EC135
AgustaWestland AW139
06/06/2011 #39

40. 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
06/06/2011 #40

41. Data Acquisition and Making Adjustments Sweep

Bell 206 Series Sweep Adjustment
06/06/2011 #41

42. 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
06/06/2011 #42

43. Data Acquisition and Making Adjustments Tip Weight

M/R
MI 8/17/24 Tip Weight Adjustment
T/R
06/06/2011 #43

44. 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
06/06/2011 #44

45. Data Acquisition and Making Adjustments Tip Weight

BO 105 M/R Hub Weight - Hollow Bolt
EC155 M/R Hub Weight - Washer
06/06/2011 #45

46. Data Acquisition and Making Adjustments Hub Weight

Bell 407 T/R Irregular
Bell 206 Series T/R Regular
06/06/2011 #46

47. 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
06/06/2011 #47

48. Data Acquisition and Making Adjustments Blade Chord Weight

Bell 407 Chord/Product Weight
06/06/2011 #48

49. Troubleshooting

Polar Plotting - Human error
Worn components
Structural resonance
06/06/2011 #49

50. Troubleshooting Polar Plotting

Human Error
The result of an
adjustment increases
the IPS or the
moveline 180 degrees
out
06/06/2011 #50

51. 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
06/06/2011 #51

52. 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.
06/06/2011 #52

53.

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support@acessystems.com
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