The Fuel Tank Flammability Assessment Method

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The Fuel Tank Flammability Assessment Method
International Aircraft Systems Fire Protection
Working GroupAtlantic City, NJ
November 2, 2005
Steve Summer
Project Engineer
Federal Aviation AdministrationFire Safety
Branch
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Background

• The Fuel Tank Flammability Assessment Method is
  an Excel based macro originally developed by the
  1998 ARAC Fuel Tank Harmonization Working Group
  as a comparative tool to assist in determining
  the potential fleet wide flammability exposure of
  a given fuel tank.
• The program utilizes Monte Carlo statistical
  methods to determine several unknown variables,
  using standardized distributions.
• Fuel flashpoint temperature
• Flight mission length
• Ambient ground temperature
• Ambient cruise temperature

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Background (cont.)

• By Monte Carlo theory, generating these values
  over a sufficiently large number of trials will
  minimize the errors associated with the
  statistical analysis.
• Additional functionality of the program
• Single flight analysis (for troubleshooting)
• Random Number Freeze (for troubleshooting)
• Warm day analysis
• Flammability Reduction Method (FRM) effectiveness
  analysis
• For detailed information regarding the program,
  users should reference FAA document
  DOT/FAA/AR-05/8 (pending publication)

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Program Overview
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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Fuel Tank Usage Data
• Body Tank Input Data
• Tank Thermal Data
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Maximum range of aircraft
• Number of engines
• OAT cutoff temperature
• Flight Data
• Fuel Tank Usage Data
• Body Tank Input Data
• Tank Thermal Data
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Cruise Mach number
• Tank ram recovery
• Cruise altitude steps
• Fuel Tank Usage Data
• Body Tank Input Data
• Tank Thermal Data
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Fuel Tank Usage Data
• Tank full/empty times
• Engine/equipment start time
• Body Tank Input Data
• Tank Thermal Data
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Fuel Tank Usage Data
• Body Tank Input Data
• Is the tank in the fuselage?
• Is the tank pressurized?
• Pressure altitude of tank in cruise
• Temperature of compartment surrounding tank
• Tank Thermal Data
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Fuel Tank Usage Data
• Body Tank Input Data
• Tank Thermal Data
• Fuel temperature differentials relative to
  ambient
• Exponential time constants (define how fuel
  heats/cools in response to heat input)
• Multi-Flight Monte Carlo Data

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Program Overview User Inputs

• User inputs for the program are divided into six
  categories
• Airplane Data
• Flight Data
• Fuel Tank Usage Data
• Body Tank Input Data
• Tank Thermal Data
• Multi-Flight Monte Carlo Data
• Number of Flights
• Random number freeze? (y/n)
• Warm day analysis? (y/n)

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Program Overview User Inputs (cont.)

• Additional user inputs when performing an FRM
  analysis
• Reliability Effects
• MTBF - of hours that the FRM is functional
  between failure events
• Failure detection capability - of flights
  before a failure would be detected
• MEL Assumption Average time, in flight hours,
  for FRM system to be restored once failure is
  detected
• Performance Effects
• Performance aspects of the FRM must be programmed
  by the user into the existing code and shown to
  provide an accurate representation of the FRM

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Program Overview Main Calculations
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Program Overview Outputs

• Monte Carlo Flammability Analysis
• Table displaying the following
  
  data for each flight
• Preflight ground time
• Flight time
• Ambient temperature
• Cruise temperature
• Fuel flashpoint temperature
• Amount of time that the tank
  
  was flammable
• of flight time that the tank
  
  was flammable
• Table displaying warm day (ground ambient
  temperature gt 80?F) results
• Chart showing a summary of the Multi-Flight Monte
  Carlo Analysis

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Program Overview Outputs (cont.)

• Monte Carlo with FRM Analysis
• Table displaying baseline
  
  (i.e., no FRM) flammability
  
  data and corresponding
  
  flammability data due to
  
  reliability issues of the FRM
• Table displaying baseline flammability data and
  corresponding flammability data due to
  performance issues of the FRM for each phase of
  flight
• Table showing overall FRM effectiveness
  (reliability and performance issues)

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Program Overview Outputs (cont.)

• Single Flight Analysis
• Time-based and altitude-based plots of fuel
  temperature, TAT, LFL and UFL

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Screenshots User Inputs Results Page
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Screenshots FRM Page
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Screenshots Single Flight Page
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Current Status

• Program is complete and will be released for
  comment with the pending NPRM
• Visual Basic version of model is currently under
  development
• User manual is written and is undergoing internal
  review
• Will have FAA report number DOT/FAA/AR-05/8
• Will be released in draft format, for comment
  with the pending NPRM
• Current status of NPRM can be viewed online at
  http//regs.dot.gov/rulemakings/index.htm