Upload
wesley-clarke
View
230
Download
5
Embed Size (px)
Citation preview
Creating better aviation maintenance solutions...
Rotor Track and Balance
.
Creating better aviation maintenance solutions...
OverviewRotor BalanceTypes of BalanceEquipmentInstallationData Acquisition and Making AdjustmentsTroubleshooting
Creating better aviation maintenance solutions...
Rotor BalanceWhat is an imbalance?Advantages and disadvantagesCauses of imbalanceOther sources of vibration
Creating better aviation maintenance solutions...
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
Creating better aviation maintenance solutions...
Rotor Balance
AdvantagesSimpleCost efficientCost effective
Creating better aviation maintenance solutions...
Rotor Balance
DisadvantagesNoiseVibration
Creating better aviation maintenance solutions...
Rotor Balance
Causes of ImbalanceManufacturing tolerancesShimming and alignmentRotor track
Static track Dynamic track
Creating better aviation maintenance solutions...
Rotor Balance
Rotor TrackStatic 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
Creating better aviation maintenance solutions...
Rotor Balance
Rotor TrackDynamic track
How the rotors fly during operation More important to sacrifice a perfect tip path track
for a rotor that is perfectly balanced
Creating better aviation maintenance solutions...
Rotor Balance
Other Sources of VibrationMechanical loosenessMisalignmentTrackWorn bearings
Creating better aviation maintenance solutions...
Types of BalanceDynamic track and balancePurpose of balancingTypes of imbalance
Creating better aviation maintenance solutions...
Types of Balance
Dynamic Track and BalanceFirst introduced in the late 1950’s
Operators found that virtually all statically balanced rotors were out of balance dynamically when installed.
Creating better aviation maintenance solutions...
Types of Balance
Purpose of BalancingStatic
Knife edge Suspended arbor Bubble balance
Creating better aviation maintenance solutions...
Types of Balance
Purpose of BalancingDynamic
Performed during operation All of the rotating components are balanced as an
assembly
Creating better aviation maintenance solutions...
Types of Balance
Types of Imbalance Mass imbalance
Distribution of the mass Spanwise or chordwise
Aerodynamic imbalance Out-of-track condition exists
Creating better aviation maintenance solutions...
Types of Balance
Benefits to Dynamic BalanceEnhance comfortReduce wearIncrease safety by reducing component stressLower operating costs
Creating better aviation maintenance solutions...
EquipmentSensorsTach sourcesVibration measurementsAmplitude and phase
Creating better aviation maintenance solutions...
Equipment
SensorsAccelerometersDisplacement sensorsVelocity sensors
Creating better aviation maintenance solutions...
Equipment
AccelerometersMeasure acceleration Typically reported in g’sMore sensitive to higher frequenciesDirectly related to force caused by unbalanceUsed in balancing
(after conversion to velocity or displacement)
Creating better aviation maintenance solutions...
Equipment
Displacement SensorsMeasure change in positionTypically reported in mils (.001 of an inch) peak to
peakMore sensitive to Low frequenciesDirectly related to movements due to imbalanceSeldom used in balance (however, displacement
units are often used)
Creating better aviation maintenance solutions...
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
Creating better aviation maintenance solutions...
Equipment
Sensor Construction
PEDESTAL
PIEZOELECTRICELEMENT IN
COMPRESSION
SEISMIC MASS
OUTPUT CONNECTOR AND AMPLIFIER
BASE
PRELOADSCREW
Creating better aviation maintenance solutions...
Equipment
Tach SourcesMagnetic pickupPhototach
Creating better aviation maintenance solutions...
Equipment
Magnetic Pickup
Creating better aviation maintenance solutions...
Equipment
Phototach
Creating better aviation maintenance solutions...
Equipment
Vibration MeasurementsAmplitude 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)
Creating better aviation maintenance solutions...
InstallationSensorTach SourceTip Targets
Creating better aviation maintenance solutions...
Installation
Sensor
Creating better aviation maintenance solutions...
Installation
Tach Source
Creating better aviation maintenance solutions...
Installation
Tip Targets
Creating better aviation maintenance solutions...
Installation
Optical TrackerOptical devices obsolete tip targets
Creating better aviation maintenance solutions...
Data Acquisition and Making AdjustmentsPolar plottingAutomated solutionsRotor track and balanceRules
Creating better aviation maintenance solutions...
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.
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Automated SolutionsThe analyzer is used to collect the phase and
IPS readings then calculates a solutionThe calculated solution is then implemented
by the user eliminating manual calculations
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Rotor Track and BalancePitch linksTabSweepTip weightHub weightBlade chordwise weight
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Pitch LinksChanges 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
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
TabChanges 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
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
SweepChanges 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
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Tip WeightChanges 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
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Hub WeightChanges 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
Creating better aviation maintenance solutions...
Data Acquisition and Making Adjustments
Blade Chord WeightChanges 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
Creating better aviation maintenance solutions...
TroubleshootingPolar Plotting - Human errorWorn componentsStructural resonance
Creating better aviation maintenance solutions...
Troubleshooting
Polar PlottingHuman Error
The result of an adjustment increases the IPS or the moveline 180 degrees out
Creating better aviation maintenance solutions...
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
Creating better aviation maintenance solutions...
Troubleshooting
Structural ResonanceUnrepeatable readingAdjustments result in
varying resultsPhase angles and IPS
levels are very erratic and unpredictable when known good solutions are implemented.
Creating better aviation maintenance solutions...
Contact
www.acessystems.com
1-865-671-2003