The Fuel Tank Flammability Assessment Method

1. Federal Aviation Administration 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

2. 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

3. 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)

4. Program Overview

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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)

12. 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

13. Program Overview – Main Calculations

14. 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

15. 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)

16. Program Overview – Outputs (cont.) • Single Flight Analysis • Time-based and altitude-based plots of fuel temperature, TAT, LFL and UFL

17. Screenshots – User Inputs & Results Page

18. Screenshots – FRM Page

19. Screenshots – Single Flight Page

20. 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