# Presentation: 766551

## Ground-Based Inerting of a

- Boeing 737 Center Wing Fuel Tank

## Outline

- Background
- Work Distribution
- Instrumentation
- Inerting Data
- Ground Testing
- Flight Testing

## 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

## 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

## 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

## System Block Diagram

## Sample Port Location Diagram

## 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

## 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]

## 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

## Fuel Tank Inerting Data

## Nondimensional Data Comparison

## Ground Testing Data

- 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%

## Ground Testing Data

## Ground Testing Data

## Comparison Data

## Ground Testing Data

## Ground Testing Data

## Flight Testing Data

- 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.

## Flight Testing Data

## Flight Testing Data

## Comparison Data

## Flight Testing Data

## Flight Testing Data

## Flight Testing Data

## Flight Testing Data Comparison

- 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

## Comparison Data

## Comparison Data

## Comparison Data

## Summary

- 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