SYSTEMS FOR AIRCRAFT PREDICTIVE MAINTENANCE CHADWICK - HELMUTH SYSTEMS FOR AIRCRAFT PREDICTIVE MAINTENANCE Propeller Balance
CHADWICK-HELMUTH DYNAMIC PROPELLER BALANCE Presented By: Angel Colon Field Service Department Chadwick-Helmuth Co. Inc El Monte, CA
Propeller Balance Balance Theory Equipment Installation Data Acquisition Making Adjustments Troubleshooting
PROPELLERS Advantages Simple Efficient Disadvantages Noise Vibration
SOURCES OF VIBRATION IMBALANCE MECHANICAL LOOSENESS MISALIGNMENT GEARS BEARINGS
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.
CAUSES OF IMBALANCE Manufacturing Tolerances Spinners Propellers Crankshafts etc. Stack up of rotating parts Propeller Track
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
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
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
PURPOSE of BALANCING Decrease Vibration Enhance Comfort Reduces Noise Increases safety by reducing component stress Lowers operating costs
WHAT IS BALANCING? MASS BALANCE Distribution of the mass (weight) Spanwise Chordwise AERODYNAMIC 1 per revolution (1P) N per revolution (Harmonics or multiples)
BALANCE PROCEDURES Hartzell Standard Practices Manual 202A Chadwick Helmuth Manual AW-9511-2 “The Smooth Propeller” MaCauley Service Letter 1989-4 Other propeller and equipment manufacturers manuals
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
STATIC BALANCE
VIBRATION MEASUREMENTS Acceleration -- G’s Displacement -- MILS (peak to peak) Velocity -- IPS (inches per second)
VIBRATION TRANSDUCER and PHOTOCELL
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
INFORMATION REQUIRED AMPLITUDE How Much??? Severity of the vibration (IPS) PHASE ANGLE Where??? Reference Point
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
TYPICAL TRANSDUCER INSTALLATION
PHOTOCELL INSTALLATION
INSTALL THE REFLECTIVE TAPE
SAFETY TIP!!!!! ROUTE ALL CABLING TO AVOID INTERFERENCE WITH MOVEMENT OF CONTROLS AND COCKPIT EGRESS
BALANCE METHOD LIGHT - HEAVY Trial Weight Addition BALANCE CHARTS Vector Plotting Known Sensitivities
A POLAR CHART THE MAKING OF
POLAR CHART
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
TEMPORARY WEIGHT INSTALLATION
PERMANENT WEIGHT INSTALLATION
BALANCE LEVEL TARGETS
TROUBLESHOOTING Transducers/Cables Balancer Strobe Light Operator Error Aircraft Installation Problems
CHADWICK - HELMUTH CONCLUSION
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
QUESTIONS ?