October 30-31, 2002 International Aircraft Systems Fire Protection Working Group Atlantic City, NJ Inerting of a Scale 747SP Center Wing Fuel Tank During a Typical Commercial Flight Profile William Cavage AAR-440 Fire Safety Research Federal Aviation Administration

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Outline Background Scale Tank Model Instrumentation Testing Scope Inerting Efficiency Test Data Summary

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Background FAA is Seeking to Improve Upon Existing Fuel Tank Safety in Fleet in the Wake of TWA800 Air Disaster Inerting of Fuel Tanks Could Provide Significant Fuel Tank Protection. Focus of the testing is to validate the ability of the FAA simplified fuel tank inerting system to inert the CWT of a 747SP Use modeling results to validate the modeling tools developed during GBI studies Study inert gas distribution during the commercial mission

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Description of Model Quarter-scale model of Boeing 747SP CWT was built from three-quarter inch plywood by scaling drawings from Shepherd report –24% length scale (1.4% Volume) –Spars and spanwise beams simulated with quarter-inch plywood installed in slats with scaled penetration holes –Vent system simulated with PVC tubing plumbed to an aluminum vent channel –Removable lid to allow for model maintenance and modification Model in 6x6x7 altitude chamber Model inerted with manual NEA mixer

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Photo of Model

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/ SP Bay Diagram with Volume Data Reported Volume = 1775 Percent Difference = 4.47 %

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Instrumentation Onboard oxygen analysis system (OBOAS) acquired bay oxygen concentration data –One sample port in each bay –Sample returned to tank through manifold Thermocouple in chamber gave temperature Altitude measured by absolute pressure transducer NEA Flow metered/measured with mass flow controller and oxygen concentration determined with flow through galvanic cell type oxygen analyzer

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Onboard Oxygen Analysis System Block Diagram

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Altitude Chamber NEA Mixer Oxygen Analyzer Flow Controller Scale Tank Testing Block Diagram DAS Nitrogen Compressed Air NEA Generator Computer T OBOAS Pressure Transducer Sample Return Scale Tank Model

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Scope of Testing to Date All testing involved single deposit in bay 6 All testing used generic flight profile with different cruise times and different holds at 5K feet All testing uses same predicted system performance in terms of NEA flow and purity All tests had same venting configuration –Right side (left wing tip) vent system blocked –Plans to block aft port on open vent side for some tests

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 OBIGG System Model

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Inerting Efficiency Based on perfect mixing solution Develop inerting efficiency equation Redimensionalize perfect mixing solution with

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Volume Inerting Results Inerted tank twice with similar, constant inerting conditions at two different altitudes Compared nondimensional results Results were similar, but not identical –Average Tank Inerting Close –Bay inerting trends good, but values can differ greatly –Some data trends unusual Inerting efficiency values very different

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Inerting Efficiency Results Constant inerting data inerting efficiency trends similar but values very different –Tend toward same value? When examining a complete simulation, k values vary greatly –Trends are not consistent –Makes prediction of inerting with perfect mixing solution difficult Some calculations respectable with a constant k –Good k value found by iteration –Can be very accurate in a narrow data band –Never examined descent data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Descent Inert Gas Distribution Results All descent tests had similar results regardless of hold times which was better then intuitively expected –Worst bays (bay 1 & bay 3) were typically 13-14% oxygen by volume –Other bays typically between 10% and 12% oxygen Test showed that sample system has small effect resulting distribution

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 5K Hold Results Performed several descent tests –Started at 39k feet, low tank oxygen concentration Examined the effect of holding at 5K on the resulting tank oxygen concentration as well as the worst bay oxygen concentration Results indicate short hold helps reduce tank oxygen concentration, but exhibits diminishing returns on longer holds –The resulting oxygen concentration of the tank was generally around 12%, which is the predicted NEA purity at the 5k feet Holds tend to improve distribution

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Run System After Touchdown Results Performed several descent tests –Started at 39k feet, low tank oxygen concentration –Obtained resulting tank oxygen concentration/distribution Ran “system” for 15 and 30 minutes at sea level in low flow mode (5% NEA) Results indicate running system in low flow mode decreases the average tank oxygen concentration well, but does little for bay 1 –Bay 3 is usually worst bay at touchdown, but generally decreases oxygen concentration quickly

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 747SP Scale Fuel Tank Inerting Data

Scale Fuel Tank Testing ___________________________________ ISFPWG Meeting - 10/30/02 Inerting the tank at altitude was consistent with previous GBI research Inerting efficiency calculations could be used to predict average tank inerting in limited cases only with manipulated k values Preliminary descent modeling illustrates good distribution of inert gas with resulting average tank oxygen concentrations of approximately 12% Short holds at 5K feet will improve the inert gas distribution in the tank and help lower the tank average oxygen concentration Running the system on the ground for 15 to 30 minutes in low flow mode will improve tank oxygen concentration but has little effect on the bay 1 oxygen concentration Summary