Ground Based Fuel Tank Inerting

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OBIGGS Sizing Data for Transport Canada Trade
Study
William CavageAAR-440 Fire Safety BranchWm. J.
Hughes Technical CenterFederal Aviation
Administration
International Systems Fire Protection Working
Group Place de Ville Tower C Ottawa, Canada
February 14-15, 2005
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Outline

• Background
• Methods
• Baseline Data
• Results
• Summary

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Objective of Work

• Develop data on OBIGGS system performance to be
  used for a fire fighting trade study
• Must quantify the size of system needed in terms
  of the number of ASMs for several different size
  aircraft
• Must quantify fuel tank size and descent time at
  a minimum
• Base calculations on flight test data
• Use OBIGGS size data to develop fire fighting
  capability of the system

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Develop System Sizing Data

• Create 3 aircraft CWT sizes based on familiar
  aircraft
• Small (A320), Medium (747SP), and Large (747-400)
• Develop a spec missions (2) based on modified
  A320 flight test profiles
• Do analysis to size systems
• Base system performance on measured flight test
  data
• Use purity and flow measured on single ASM A320
  flight test
• Assume each CWT is a single bay box with a single
  deposit and vent
• Make calculations of resulting ullage oxygen
  concentration using developed FAA ullage inerting
  model
• Determine number of ASMs needed to land below 12
  for 2 different system methodologies (dual flow
  single high flow)

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Specified Low Descent Rate Mission
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Example of Ullage Model Results of System Sizing
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Example of Ullage Model Results of System Sizing
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Results of Analysis Low Descent Rate
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Results of Analysis High Descent Rate
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Summary

• FAA used developed tools to size systems for
  generic aircraft for trade study of OBIGGS fire
  fighting capability
• Developed a range of flows and maximum flows
  predicted for use in aircraft fire fighting given
  three generic single bay fuel tanks
• More work is needed to characterize specific
  volume flow and purities expected from each
  system give specific altitudes and bleed air
  pressures outside of observed flight test
  conditions
• More work needed to quantify the effects of a
  compartmentalized tank on system sizing
  requirements