William M Cavage Advances in Aviation Safety Conference SAE Aerospace Congress & Exhibition September 10-14, 2001

Ground-Based Inerting of a Boeing 737 Center Wing Fuel Tank William M CavageAdvances in Aviation Safety ConferenceSAE Aerospace Congress & Exhibition September 10-14, 2001 Seattle, WA SAE Advances in Aviation Safety Conference

Outline • Background • Work Distribution • Instrumentation • Inerting Data • Ground Testing • Flight Testing SAE Advances in Aviation Safety Conference

Background • FAA is Seeking to Improve Upon Existing Fuel Tank Safety in Fleet in the wake of TWA800 Air Disaster • 1998 ARAC FTHWG Stated GBI is a Potentially Cost-Effective Method of Providing Fuel Tank Protection • Report Also States CWTs More Susceptible to Mishaps • Focus of the testing is to determine if the Existing Fleet Vented Fuel Tanks Will Maintain NEA Benefit for a Significant Amount of Time • Some CWTs in Fleet are Cross Vented • Also Attempted to Gage Practicality SAE Advances in Aviation Safety Conference

Testing Work Distribution • FAA Certification Office Proposed Testing to Examine Certain Key Assumptions. Formulated Test Plan • Boeing Offered Use a Boeing B-737NG as the Test Aircraft • Air Liquide Provided an NEA Generator with Delivery Equipment at Low Cost • Boeing also Provided Aircraft NEA Distribution System, Support Personnel, Data Acquisition, and Most Instrumentation • FAA Fire Safety R&D Provided Integrated Ullage Sample System with Oxygen Analyzers SAE Advances in Aviation Safety Conference

Aircraft Instrumentation • Oxygen Analysis System Provides 8 Channels of Continuous Oxygen Concentration Data • Actively Controls Sample Inlet and Outlet Pressure • Flow Through Sensor Design • Fluid Traps, Ejector/Evacuator, Flame Suppressors for Safety • Other Instrumentation • CWT Thermocouples • Flight Data (air speed, altitude, attitude) • Fuel Load • Wind Data SAE Advances in Aviation Safety Conference

System Block Diagram SAE Advances in Aviation Safety Conference

Figure 1 Nitrogen Distribution Manifold and Fuel Vapor Ports in Center Tank Sample Port Location Diagram SAE Advances in Aviation Safety Conference

Data Presentation • Calculated Average Oxygen Concentration in the Three Primary Areas in CWT; Center Section, Left Cheek, and Right Cheek • Marked Some Critical Events • Data Plotted Every 1/Second for Inerting Data, 1/Minute for Ground and Flight Tests • Inerting Data Nondimensionalized for Comparison SAE Advances in Aviation Safety Conference

Data Nondimensional Scheme • Want to Express Time in Terms of Volume Delivered or Volumetric Tank Exchange (VTE) • VTE = Time * Volume Flow Rate / Total Tank Volume • Want to Express Oxygen Concentration in Terms of Purity Delivered. Consider that Inerting Gas is Slowly Changing the Ullage Oxygen Concentration to that of the Gas (Purity) Call this the Tank Inerting Ratio • Inerting Ratio = Air[O2] - Tank[O2] / Air[O2] - NEA[O2] SAE Advances in Aviation Safety Conference

Fuel Tank Inerting • Only Inerted the CWT with Properly Operating Manifold 3 Times • Fuel Clogged Lines and Prevented Equal Distribution at Different Times • Data Looks Consistent with Lab Observations • Manifold not Balanced for Optimal Delivery Distribution • Performed Non-Dimensional Analysis and Compared with Existing Models • Volumetric Tank Exchange Measured at Approximately 1.8 Tank Volumes SAE Advances in Aviation Safety Conference

Fuel Tank Inerting Data SAE Advances in Aviation Safety Conference

Nondimensional Data Comparison SAE Advances in Aviation Safety Conference

Ground Testing Data • In Calm Conditions, Tank Oxygen Concentration Rose Very Little During Ground Operations, But some Wind Conditions Caused Sharp Increases in Local Oxygen Concentrations having an Overall Detrimental Effect • Did Not Quantify Wind Effects • Some Wind Conditions Generated, Some Natural • Fueling had a Notable Effect, but Did Not Cause the Oxygen Concentration to Rise Above 10% SAE Advances in Aviation Safety Conference

Ground Testing Data SAE Advances in Aviation Safety Conference

Comparison Data SAE Advances in Aviation Safety Conference

Ground Testing Data SAE Advances in Aviation Safety Conference

Flight Testing Data • Due to Profound Effect of Ground Winds and some Flight Conditions, Vent System was Modified to Prevent Cross Flow After First Flight Test • Effect of Cross-Flow Very Profound Over a Two Hour Flight • Plotted Altitude with Average Bay Oxygen Concentrations to Illustrate Effect of Flight • With Cross-Flow Eliminated The CWT Retained the Oxygen Concentration Fairly Well. SAE Advances in Aviation Safety Conference

Flight Testing Data SAE Advances in Aviation Safety Conference

Flight Testing Data Comparison • Compare Overall Fuel Tank Oxygen Concentration Average to Illustrate Effect of Certain Parameters • Fuel Load Effect Less Profound Then Predicted • Effect of Fuel Burn Appears to be the Primary Effect on CWT [O2] • Effect of Altitude Difficult to Discern SAE Advances in Aviation Safety Conference

Summary • GBI Was Easily Accomplished by Distributing NEA into a CWT with a Basic Distribution Manifold with Amount of NEA Consistent with Lab Tests • Fuel had a Small but Measurable Effect During Ground Operations • Wind Conditions Could Have A Profound Effect on the Ability of a Cross Vented Aircraft fuel Tank Staying Inert as do Some Flight Conditions • GBI Provided Significant Protection Through Takeoff and Most of Cruise to a Vented CWT Provided Cross Venting was Eliminated Even with Some Fuel Loads SAE Advances in Aviation Safety Conference

William M Cavage Advances in Aviation Safety Conference SAE Aerospace Congress & Exhibition September 10-14, 2001