cargo bay fire protection with a fuel tank inerting system william cavage aar-440 fire safety branch...
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Cargo Bay Fire Protection with a Fuel Tank Inerting System
William CavageAAR-440 Fire Safety Branch
Wm. J. Hughes Technical CenterFederal Aviation Administration
International Systems Fire Protection Working Group
Tropicana Casino and Resort Atlantic City, NJ
November 1-2, 2005
AAR-440 Fire Safety R&D
Cargo Bay Inerting____________________________________
Outline• Background
• Test Article and Method
• Preliminary Results
• Summary
AAR-440 Fire Safety R&D
Cargo Bay Inerting____________________________________
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
Cargo Bay Inerting____________________________________
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
Cargo Bay Inerting____________________________________
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
Cargo Bay Inerting____________________________________
Rendering of Cargo Bay with Gas Sample Locations
- Gas Sample Locations
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AAR-440 Fire Safety R&D
Cargo Bay Inerting____________________________________
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
Cargo Bay Inerting____________________________________
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
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Analytical Inerting Model 747SP Ground Test Data Altitude
Comparison of Cargo Bay Inerting Test with Model Data - 110 SCFM Air Leak
68 SCFM of 8% NEA
OBIGGS Off
45 SCFM of 5% NEA
AAR-440 Fire Safety R&D
Cargo Bay Inerting____________________________________
• 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
Summary