1. SYSTEMS FOR AIRCRAFT PREDICTIVE MAINTENANCE
CHADWICK - HELMUTH
SYSTEMS FOR AIRCRAFT PREDICTIVE MAINTENANCE
Propeller Balance

2. CHADWICK-HELMUTH DYNAMIC PROPELLER BALANCE
Presented By: Angel Colon
Field Service Department
Chadwick-Helmuth Co. Inc
El Monte, CA

3. Propeller Balance Balance Theory Equipment Installation
Data Acquisition
Making Adjustments
Troubleshooting

4. PROPELLERS
Advantages Simple
Efficient
Disadvantages Noise Vibration

5. SOURCES OF VIBRATION IMBALANCE MECHANICAL LOOSENESS MISALIGNMENT GEARS
BEARINGS

6. IMBALANCE
A condition where there is more mass on one side of a rotating device than on the other side causing an outward radial force in the direction of the additional mass when the object is rotated.

7. CAUSES OF IMBALANCE Manufacturing Tolerances
Spinners
Propellers
Crankshafts etc.
Stack up of rotating parts
Propeller Track

8. PROPELLER TRACK STATIC TRACK
PERFECT TRACK IF ALL BLADES PRODUCE THE SAME THRUST
ASSUMES BLADE TWIST, PROFILE AND STIFFNESS ARE EQUAL ON ALL BLADES
ASSUMED THEN TO GIVE EQUAL LIFT ON ALL BLADES

9. PROPELLER TRACK DYNAMIC TRACK How the prop tracks in operation
Propellers don’t do anything statically, it does its job in a dynamic environment
More important to sacrifice a statically perfect track for one that is dynamically perfect

10. DYNAMIC BALANCE First introduced in the late 50’s to early 60’s
FBO’s found 80% of static balanced props become out of balance when installed.
Advantage of dynamic balance is:
It takes place on the aircraft
Rotating components, such as spinners, propellers, crankshaft, etc. are all being balanced together as one assembly

11. PURPOSE of BALANCING Decrease Vibration Enhance Comfort Reduces Noise
Increases safety by reducing component stress
Lowers operating costs

12. WHAT IS BALANCING?
MASS BALANCE Distribution of the mass (weight) Spanwise Chordwise
AERODYNAMIC per revolution (1P) N per revolution (Harmonics or multiples)

13. BALANCE PROCEDURES Hartzell Standard Practices Manual 202A
Chadwick Helmuth Manual AW “The Smooth Propeller”
MaCauley Service Letter
Other propeller and equipment manufacturers manuals

14. TYPES OF BALANCING STATIC Marvel Balance Kit (suspension)
Knife Arbor
Roller Arbor
Bubble Balance
DYNAMIC BALANCE Will correct for weight stack up errors after buildup and installation of propeller on aircraft

15. STATIC BALANCE

16. VIBRATION MEASUREMENTS
Acceleration -- G’s
Displacement -- MILS (peak to peak)
Velocity -- IPS (inches per second)

17. VIBRATION TRANSDUCER and PHOTOCELL

18. Transducer OUTPUT CONNECTOR AND AMPLIFIER PRELOAD SCREW SEISMIC MASS
PEDESTAL
PIEZOELECTRIC
ELEMENT IN
COMPRESSION
SEISMIC MASS
OUTPUT CONNECTOR
AND AMPLIFIER
BASE
PRELOAD
SCREW
11/10/2018

19. INFORMATION REQUIRED
AMPLITUDE How Much??? Severity of the vibration (IPS)
PHASE ANGLE Where??? Reference Point

20. EQUIPMENT INSTALLATION
VELOCIMETER Close to propeller (4 in) for balancing Rear of engine (if desired, for troubleshooting)
TACH SIGNAL Photocell Mag pickup Reflective tape and strobe light

21. TYPICAL TRANSDUCER INSTALLATION

22. PHOTOCELL INSTALLATION

23. INSTALL THE REFLECTIVE TAPE

24. SAFETY TIP!!!!!
ROUTE ALL CABLING TO AVOID INTERFERENCE WITH MOVEMENT OF CONTROLS AND COCKPIT EGRESS

25. BALANCE METHOD LIGHT - HEAVY Trial Weight Addition
BALANCE CHARTS Vector Plotting Known Sensitivities

26. A
POLAR
CHART
THE
MAKING OF

27. POLAR
CHART

28. BALANCE CORRECTION ADDING WEIGHT Determine location Determine amount
WARNING!!! DO NOT ADD TOO MUCH WEIGHT
CHECK RESULTS Perform additional runs if required
UPDATE AIRCRAFT LOG BOOK

29. TEMPORARY WEIGHT INSTALLATION

30. PERMANENT WEIGHT INSTALLATION

31. BALANCE LEVEL TARGETS

32. TROUBLESHOOTING Transducers/Cables Balancer Strobe Light
Operator Error
Aircraft Installation Problems

33. CHADWICK - HELMUTH
CONCLUSION

34. DYNAMIC PROPELLER BALANCE
Improvement immediately noticeable
Smoother idle, smoother power applications
Annoying buzzes in panels and throbbing in floor significantly reduced
Two hours average time to accomplish the task.
UPDATE AIRCRAFT LOG BOOK

35. QUESTIONS ?