Ground Based Fuel Tank Inerting

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Boeing 747SP CWT Inerting Efficiency
William M CavageProject Manager - Fuel Tank
Inerting FAA AAR-440, Fire Safety RD Branch
June 13th-14th, 2002International Systems Fire
ProtectionWorking Group CAA House - London, UK
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Vertical Mixing / Temperature Effects

• Quiescent Full-Scale Testing has Indicated that
  Inerting of the 747SP in the Optimal Deposit
  Method Developed with the Plywood Model can be
  Problematic (No ACMs Operating)
• Inerting Efficiency Different from Test to Test
• Measured Strong Vertical Effects in one Full
  Length Bay
• Bottom of Bay O2 Lags Behind Top of Bay on
  Quiescent Tests
• Complicated by the Fact that Sample System only
  Samples from Top
• Preliminary Data Shows Effect is Not NEA
  Temperature Dependant but is Effected by the NEA
  Temperature

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747SP Inerting Data with Different Vertical
Mixing
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Inerting Efficiency

• Due to Sample Lag Dont have a Good Picture of
  Inerting in the Tank During Test
• Sample Biased Due to Location of Sample Ports
• Know Beginning Point (20.9) and End Point After
  Run ACMs
• Want to Approximate the Progression of Tank
  Oxygen Concentration During the Testing
• Use Generic Inerting Equation to Develop
  Efficiency Factor K
• Solve for K and Redimensionalize to Get a Curve
  for Each Test Result
• Have Multiple Tests with Different Mixing

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747SP Calculated Inerting Curves with Different
Vertical Mixing
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Summary

• Although the Bay-to-Bay Distribution of NEA Was
  Predictable and Repeatable, Inerting Efficiency
  Varied from Test to Test due to Problems with
  Vertical Mixing
• When Vertical Mixing is Stimulated, Inerting of a
  Compartmentalized Tank with a Localized Deposit
  is very Repeatable
• Care will Need to be Taken During Deposit System
  Design to Ensure Good Vertical Mixing in Deposit
  Locations