# Presentation: 217638

## The Fuel Tank Flammability Assessment Method

- Steve Summer                               Project Engineer                                     Federal Aviation AdministrationFire Safety Branch

- International Aircraft Systems Fire Protection Working GroupAtlantic City, NJ                                 November 2, 2005

## 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

## 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)

## Program Overview

## 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

## 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

## 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

## 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

## 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

## 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

## 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)

## 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

## Program Overview – Main Calculations

## 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 > 80F) results
- Chart showing a summary of the Multi-Flight Monte Carlo  Analysis

## 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)

## Program Overview – Outputs (cont.)

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

## Screenshots – User Inputs & Results Page

## Screenshots – FRM Page

## Screenshots – Single Flight Page

## 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