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Fritz Friedersdorf

Aircraft Corrosion Maintenance and Sustainment. Luna Innovations Incorporated  friedersdorf@lunainc.com Office 1.434.220.0148 www.lunainc.com. 5 October 2017. Fritz Friedersdorf. Issue of Corrosion for DoD Aviation. Corrosion increases costs and reduces availability of DoD aviation systems

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Fritz Friedersdorf

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  1. Aircraft Corrosion Maintenance and Sustainment Luna Innovations Incorporated  friedersdorf@lunainc.com Office 1.434.220.0148 www.lunainc.com 5 October 2017 Fritz Friedersdorf

  2. Issue of Corrosion for DoD Aviation • Corrosion increases costs and reduces availability of DoD aviation systems • $2.6 billion cost of corrosion for Navy and Marine Corps aviation (LMI 2011) • 25% of maintenance costs / 25 days of corrosion-related non-availability per year • $4.5 billion cost of corrosion for Air Force aircraft and missiles (LMI 2012) • 24% of maintenance costs / 15.9 days of corrosion-related non-availability per year • Corrosion management and sustainment for DoD aircraft is schedule based • Wash cycles are set by corrosion severity zones (TO 1-1-691) • Severe (30 days) / Moderate (90 days) / Mild (180 days) • There is a desire within DoD to implement CBM for improved corrosion prevention and control

  3. Aircraft Corrosion Health Monitoring • Individual Aircraft Tracking • Measure corrosion severity • Detect upset conditions • Predict time to next inspection • Schedule preventive maintenance • Establish long term trends • Manage inspections and maintenance processes • Perform load leveling among aircraft • Examine fleet wide trends for life cycle sustainment • Validate usage assumptions • Optimize availability and life cycle costs Fleet Management

  4. Aircraft Environment and Corrosivity Measurements • Corrosion prediction requires inputs, models, and actionable outputs that can be used by maintainers • Aircraft corrosion monitoring systems quantify: • Environmental parameters (environmental severity) • Corrosion rate of surrogate materials (corrosivity) • Sensors for use in environment and corrosivity measurements have been standardized • Electrochemical sensors are compliant with ANSI/NACE Standard TM0416-2016 • Currently a new work item within ISO

  5. Corrosion Prediction • Historically, environmental severity and corrosivity are measured by average environmental conditions and/or mass loss coupons • ISO 9223 - Corrosivity of atmospheres - Classification, determination and estimation • Environmental parameters of significance • Relative humidity • Time of wetness • Amounts of corrosive contaminants • Temperature • Location based average conditions have limited utility for individual aircraft tracking and fleet management • Recent efforts have focused on continuous, dynamic measurements and models to predict corrosion rate

  6. Aircraft Monitoring Systems • Aircraft sensor nodes include environmental and corrosivity sensors • RH and air temperature sensor • Combined sensing elements with digital output • Surface temperature sensor • RTD embedded within node enclosure material • Conductance (salt contaminants) • Gold IDE • Aluminum free corrosion rate • Aluminum alloy interdigitated electrode (IDE)

  7. Monitoring System Correlation to Mass Loss • Corrosion rate sensor output is strongly correlated to mass loss coupon measurements • AA7075-T6 mass loss coupons with / A286 SS fasteners • 45-day GMW14872 accelerated test • Both sensor and mass loss coupon response exhibit power law behavior

  8. Predictive Modeling • Instantaneous corrosion rate is dependent on environmental conditions • Non-linear / Interaction effects / Hysteresis • Environmental parameters can be used to predict corrosion rate ANN

  9. Upset Conditions • Deviation of aircraft environment from predicted conditions can be an indication of operational or maintenance issues • Isolated instances where aircraft humidity is much higher than expected humidity based on local NOAA data Corrosion monitoring system data within HH-60, Patrick AFB, FL

  10. Aircraft Operation • High altitude flight cold soaks the structure, and upon landing in a high humidity climate, condensation causes high corrosion

  11. Summary • The is a significant need for improved aircraft corrosion maintenance and sustainment • Standardized measurement methods for atmospheric corrosion monitoring are available • Machine leaning techniques may be useful for corrosion prediction • Individual aircraft monitoring can be used to quantify the effect of upset conditions and operations • Successful CBM will depend on the integration of monitoring systems, predictive models, and network systems • Output must be informative to maintainers

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