Cargo Bay Fire Protection with a Fuel Tank Inerting System

1. Cargo Bay Fire Protection with a Fuel Tank Inerting System William CavageAAR-440 Fire Safety BranchWm. J. Hughes Technical CenterFederal Aviation Administration International Systems Fire Protection Working Group Tropicana Casino and Resort Atlantic City, NJ November 1-2, 2005

2. Outline • Background • Test Article and Method • Preliminary Results • Summary AAR-440 Fire Safety R&D

3. Background • FAA developed a proof of concept inerting system to inert the CWT of classic style Boeing model 747 • FAA intends to make a rule requiring flammability control of some or all CWTS with an emphasis on inerting system technologies • Potential for using these systems to expand fire protection needs to be explored • E&E bays, wheel wells, dry bays, and hidden overhead areas for example • This project focuses on using the generated NEA to replace the cargo bay fire suppression make up agent AAR-440 Fire Safety R&D

4. Background – Cargo Bay Fire Suppression • Cargo bay fire suppression is done in two parts • First part dispenses large volume of agent rapidly to suppress fire • Second part dispenses a fixed amount of agent slowly, based on the aircraft operational capability, to make up for cargo bay leakage • It remains to be seen how useful an OBIGGS designed to inert the CWT of an aircraft would be for this purpose • Sizing would probably be different • Different design requirements, and certification requirements • Cert requirements still not firm AAR-440 Fire Safety R&D

5. Test Article • Used existing 747SP ground test article to study the issues associated with cargo bay inerting • Already has inerting system installed with associated instrumentation • Plumbed the OBIGGS to inert the aft cargo bay with a simple deposit system • Can deposit 1-6 ASMs amount of NEA of varying purity • Eight gas sample locations in cargo bay used to continually measure oxygen concentration during testing • Also can measure flow and purity of NEA being deposited • Multiple temperatures and pressure in aircraft available AAR-440 Fire Safety R&D

6. Rendering of Cargo Bay with Gas Sample Locations o o o o o o o o o - Gas Sample Locations AAR-440 Fire Safety R&D

7. Test Methods • Preliminary testing focused on finding air leak locations, rates, and effects • Discovered large bleed air leak which caused testing delay • Cargo bay heat leaked some even when off • Examining inert gas distribution issues • Previous work indicated rectangular bays have easy distribution requirements • Examine leakage effects on distribution • Focus of work is to determine the sizing (amount of NEA generated) of a CWT inerting system is relevant to cargo bay fire protection • Using static performance data and single bay inerting model to evaluate ability of inerting system given cargo bay fire conditions AAR-440 Fire Safety R&D

8. Results - Preliminary • Preliminary testing had difficult time reducing the oxygen concentration in the cargo bay below 12% • Found large bleed air leak due to cracked duct • Existing inerting models used to evaluate the problem and find size of leak • Model validated the size of the cargo bay and instruments found location of leak AAR-440 Fire Safety R&D

9. Summary • Test article is modified and ready to study cargo bay inerting • Bleed air leak has caused project delay but allowed us to develop a cargo bay inerting model that takes into account air leakage • Need information from industry to study feasibility of using an FRS for cargo bay fire protection • Need representative flight profile complete with bleed air pressure schedule of a cargo fire event • Testing will continue when air leaking issues are resolved AAR-440 Fire Safety R&D