# Presentation: 283220

## Auxiliary Tank Testing and 

- Auxiliary Tank Testing and
- In-Flight Facility Development

- Michael Burns Fire Safety Research Federal Aviation AdministrationWilliam J. Hughes Technical Center

**Notes:**
During this presentation, I would like to introduce the Development of the New FAA Auxiliary Tank Testing and In-Flight Facility
My name is Michael Burns and I am an engineering technician with the FAA at the WJHTC in NJ, USA

## Background

- Three major accidents involving center wing tanks (CWT)
- March 2001, Thai Airways International, Boeing 737-400
- July 1996, TWA flight 800, Boeing 747-100
- May 1990, Philippine Airlines, Boeing 737-300
- FAA seeks it’s flammability reduction rule since 1997
- Two unsuccessful industry rulemaking advisory committee working groups
- FAA developed a demonstration fuel tank inerting system
- Installed and operated on several test transport aircraft
- Uses air separation modules (ASM) and a dual / variable flow methodology
- Unique methodology allowed for simple, lightweight, reliable onboard nitrogen generation

**Notes:**
To date there have been 3 major accidents involving center wing tanks
Thai Airways International while sitting at the gate
TWA flight 800 while in-flight
Philippine Airlines while taxiing on the tarmac for take off
Since the accidents, significant emphasis has been placed on fuel tank safety research
In cooperation with industry, the FAA developed a demonstration nitrogen generating system that could easily be mounted on a commercial transport aircraft
The system was Installed and operated on the Boeing 747 aircraft as well as the airbus A320
The system uses air separation modules or ASM’s,  based on hollow fiber membrane technology, incorporating a dual / variable flow scheme
This Unique methodology allowed for simple, lightweight and reliable onboard nitrogen generation with very few moving parts and weighing only about 170 lbs
This allowed for additional fuel tank safety by lowering the oxygen content, defined as inerting, in the fuel tank thus reducing flammability

## Center Wing Tank Inerting Research

- Recent CWT testing with NASA, Airbus and The   Boeing Company
- FY01- FY04 testing and validation of CWT inerting methodology
- In-flight measurement of fuel tank flammability
- Excellent results but little work has been done to study the affect of auxiliary tank operations on CWT
- New research facility at FAA WJH Technical Center
- Construction scheduled for winter, 2005
- Facility being designed to study fuel tank inerting and flammability
- Real-time CWT operational simulation, full-scale testing, and model validation

**Notes:**
The FAA conducted research and testing in cooperation with NASA, Airbus, and Boeing over the coarse of a 3 year period
Such testing allowed for the validation of modeling, both computer based as well as small scale
Results of the testing allowed for a comparison of flammability between the cwt and the wing tank during a normal commercial flight scenario
Numerous reports were written by the FAA illustrating the results of testing however little work has been done to study the affect auxiliary tank operations may have on an aircraft with a Nitrogen Generating System
Presently there are plans for a new research facility to be built at the FAA WJHTC addressing these and possibly other issues
Construction of the facility is scheduled for the winter of 2005 
This Facility will be designed to study fuel tank inerting and flammability employing Real-time simulation, testing & validation

## Center Wing Tank Inerting Facility

**Notes:**
Some features depicted on this elevation drawing include:
14’ electrical roll up garage door
Ventilation or exhaust fan to safely remove any fuel vapor that may be present
And a Large Over pressure relief panel system

## Center Wing Tank Inerting Facility – cont.

- Initial use to further study the affect auxiliary fuel transfer has on an inert CWT
- Ullage oxygen concentration changes due to fuel transfer
- Purge cycle effects once the auxiliary tank is empty
- Auxiliary tank refueling effects
- Facility will house a full-scale CWT and auxiliary_ _fuel tank
- Simulate altitude as well as engine fuel burn
- Thermocouples, pressure transducers and gas sample ports for gas analysis to allow for testing
- Measure nitrogen generating system parameters

**Notes:**
Initial testing in the facility will study the affect auxiliary fuel transfer has on an inert CWT addressing issues such as:
Oxygen evolution due to the fuel transfer process
10 minute Time delay incorporated in the Purge cycle once the auxiliary tank is empty
And auxiliary tank refueling once the aircraft has landed
In either of these 3 cases there is a potential of introducing large amounts of air or oxygen into the CWT and therefore reducing the protection a Nitrogen Generating System may be providing
A full scale CWT and Auxiliary Fuel Tank will be housed in the facility
The facility will contain high volume pumps for simulating altitude as well as engine fuel burn
Several temperature measurements will be taken as well as gas analysis sample ports to measure percent oxygen concentration and total hydrocarbons
Instrumentation will be in place to measure CURRENT nitrogen generating system parameters as well as any future inerting technologies that may arise

## Facility Overview

**Notes:**
Here is an overview of the facility
CWT will be mounted on a base located in the center of the building
AUX will be coupled to the CWT via flexible braded line
Curbing with sump surrounding the CWT and the aux tank
Control Room with all the analyzers and controls
Vacuum Pump platform

## Facility Overview – cont.

- Approximately 26’ x 40’
- Interior Communication & Signal Raceways
- Pumps (3)
- Vacuum
- Hi-capacity  pump with closed loop cooling system
- Capable of simulating a 40,000 foot altitude (approx. 2 psia)
- Fuel (P1) – Electronically Controlled, Modulating
- Engine fuel burn simulator
- Variable frequency drive fuel flow controller simulates taxi, take off, climb, cruise & descent
- Fuel flow meter with digital output
- Capable of flowing 85 GPM maximum fuel flow.
- Fuel (P2) – Fixed
- Used to refuel the CWT / aux. tank when required
- Plumbed to a 10K gallon fuel vault

**Notes:**
The dimensions of the building will be approximately 26’ wide x 40’ long
It will contain Interior Communication & signal wiring raceways
It will have 3 pumps, one hi-capacity vacuum pump with a closed loop cooling system, capable of simulating altitude’s in the neighborhood of 40,000 feet
The other 2 pumps will be for fuel management.  P1 is an Electronically Controlled, Modulating pump with a variable frequency drive.
This will be used to simulate Engine fuel burn throughout all phases of flight
It will also employ a fuel flow meter with digital output
This pump will be capable of flowing 85 GPM maximum fuel flow which is the equivalent fuel consumption of a 737 aircraft at take off power
The third pump or P2 will be a fixed volume pump used to service the CWT or Aux. Tank when required
The 2 fuel pumps will be plumbed to a 10,000 gallon fuel vault located below ground

## Facility Overview – cont.

- Control Room
- Environmentally controlled
- Houses all the controls, analyzers, computer and data acquisition equipment
- 8’ x 8’, mounted on a raised concrete slab
- Safety Features
- Spill Protection – Containment pit with sump
- Foundation contains curbing that is approx. 14’ x 24 x 18”
- Approximately 500 cubic feet of volume to contain any accidental spillage of fuel
- Fire protection
- Over pressure relief panel system

**Notes:**
The facility will have an Environmentally controlled Room that will house all the controls, analyzers, computer & data acquisition equipment
This control room will be approximately 8’ x 8’ and mounted on a raised concrete slab for safety purposes
3 Additional Safety Features will be incorporated in this new facility:
Spill Protection 
Containment Pit with Sump
Approximately 500 cubic feet of curbing could contain any accidental spillage of fuel
Fire Protection will be provided by a carbon dioxide fire system able to be manually or automatically discharged in the event of a fire
For over pressure relief, there will be a 16’ x 8’ blow out panel on the side of the building

## Facility Overview – cont.

- Vacuum pump evacuates chamber
- Altitude controller
- PID Controller
- Modulating Valve
- Pressure Transducer

**Notes:**
The vacuum or altitude control system will be comprised of 3 components, a precision PID controller, modulating valve and a 0-1000 torr absolute pressure transducer which is not shown in this picture
The PID controller will be programmable to accept an unlimited number of set points simulating any flight scenario
Once the vacuum pump is turned on, the modulating valve will remain closed until the desired set point is reached
At this point it will open and modulate to hold the proper vacuum setting
The pressure transducer will send the PID controller the center wing tank vacuum or altitude readings instantly allowing for extremely fine control

## Facility Equipment 737 CWT

- Tank origin
- Salvaged from an Air Canada aircraft in March 2003
- Tank Dimensions / volume
- Approx 12’ x 14’ x 3’ (or 500 CuFt in volume)
- Reinforcing the CWT
- Exterior bracing was applied around the tank structure and fastened to the tank wherever possible
- Columns were installed in each bay internally to offset compression forces exerted on the tank while applying a vacuum

**Notes:**
The 737 CWT came from a salvaged Air Canada aircraft.  
It was cut away from the airplane and shipped to the FAA Technical center in March of 2003 
The compartmentalized tank is approximately 12’ wide, 14’ long and 3’ deep having a volume of about 500 Cubic feet
It is laterally divided into 3 bays
The Center Wing Tank is reinforced in the areas compromised by the removal process by exterior bracing applied around the tank structure and fastened wherever possible
Columns are installed in each bay internally to help offset compression forces exerted on the tank while applying a vacuum

## Facility Equipment – cont. 	737 CWT

- Facility Equipment – cont. 	737 CWT

**Notes:**
Here is an overview of the CWT and the Aux tank as they are coupled together 
Point out the following:
CWT 
Aux Tank
Hi level float valve which sends a signal to a controller to open or close the fuel transfer valves automatically until the auxiliary tank is empty
Fuel transfer and vent line
Vent system adapted to the facility vacuum plumbing
Engine fuel burn simulator pump 

## Facility Equipment – cont.737 CWT

- Vent configuration
- Internally the tank is vented in the most forward bay as well as the aft bay
- The left & right vent stringer was modified with a flange connection
- These 2 connections will be joined together with plumbing and routed to the facility vacuum system
- Engine burn simulation – fuel feed tubing
- Facility tubing will be tied into the fuel boost pump feeds on the tank

**Notes:**
The configuration of the vent system on this tank is such that the CWT stringers provide the conduit to the wing tip vents.
This allows for the equalization of pressure throughout the flight profile
Internally the tank vent stringer runs through the middle bay or bay 2  
Tubing attached to the right vent stringer runs to the most forward bay to a bell mouth tube, across to the left side of the tank, then turns aft and is routed to the rear bay
The left & right vent stringer external to the tank were modified with a flange connection
These 2 connections will be joined together with plumbing and routed to the facility altitude control system
During the center wing tank removal process from the aircraft, the fuel boost pumps which were mounted externally, were removed from the tank, however, the tubing within the tank remained in place.
The engine fuel burn simulator pump will be tied to this tubing to allow for the transfer of fuel to the fuel vault during testing

## Facility Equipment – cont.737 CWT 

- Left Fuel Feed Tubing
- (Bay 3)

- Right Vent Tubing
- (Bay 2)

## Facility Equipment – cont.Auxiliary Fuel Tank

- Tank origin
- US Airways surplus auxiliary fuel tank
- Tank Dimensions / volume
- Approx. 8’ x 4’ x 3’
- Approx. 475 Gallons of fuel
- Single tank configuration
- Also known as a “Master Fuel Cell”
- Contains a dry bay that houses all the valving associated with the system
- Cabin Tube
- The fuel cell is pressurized during flight using cabin pressure
- In facility, shop air used to simulate normal tank operation

**Notes:**
The FAA acquired the “PAT’S” auxiliary fuel tank from US Airways surplus
The Tank is approximately 8’ wide, 4’ long and 3’ deep and holds a quantity of 475 Gallons of fuel
The tank we acquired is a single tank configuration also known as a “Master Fuel Cell”
It contains a dry bay that houses all the valving associated with the system
The force used to transfer the fuel is the differential pressure between the cabin and atmosphere with the auxiliary tank being at cabin pressure and the center wing tank being at atmospheric pressure
The cabin pressure enters the auxiliary tank through a small tube located on the dry bay door
The cabin tube contains a series of check valves to prevent fuel & fuel fumes from back flowing into the cabin
If so desired the facility will have a shop air source that can be applied to obtain delta P and transfer fuel
It takes about 5 pounds per square inch differential to sufficiently begin the fuel transfer process

## Facility Equipment – cont.Auxiliary Fuel Tank

**Notes:**
Here is an overview of the auxiliary fuel tank
Recessed dry bay in the tank houses all the control valves
Redundant fuel pick up tubes incorporating float type shut off valves 
10 psi over pressure relief valve is located on the top surface and routed back to the CWT via the transfer line
The cabin tube is located on the dry bay access door

## Instrumentation  737 CWT / Auxiliary Tank

- Thermocouples
- All thermocouples are “T” type
- 25 total installed throughout the CWT
- 4 total installed throughout the Auxiliary Fuel Tank
- Gas sample tubes – (FAS, OBOAS)
- All sample tubing is made up of PFA material and  1⁄4” in diameter
- 6 total mounted throughout the CWT
- 2 total mounted throughout the auxiliary fuel tank
- NEA Inerting Manifold
- Single injection nozzle made of PFA tubing

**Notes:**
The Thermocouples or temperature probes used for this project are all type “T” which are made of copper / constantan wire
There are 25 thermocouples installed throughout the CWT tank and 4 in the auxiliary tank
The instrumentation used to measure total hydrocarbons as well as oxygen content was developed by the FAA for the purpose of flight testing
The Flammability Analysis System and the On Board Oxygen Analysis System will both be used in this facility.  
This equipment was the original instrumentation used throughout most of the flight testing previously mentioned
The gas analysis sample tubes are made of PFA material which is a type of plastic tubing and typically 1⁄4” in diameter
There are 6 sample fittings mounted in the top surface of the CWT, 2 in each bay and 2 sample tubes suspended in the auxiliary tank
The nitrogen enriched air or NEA, will enter the tank via a single injection nozzle mounted on top surface in the most forward bay, however, may be located anywhere for the purpose of testing 

## Instrumentation – cont.737 CWT / Auxiliary Fuel Tank

- CWT location of penetration fittings
- NEA
- Thermocouples
- Oxygen / FAS Sample Return Fitting
- Hi Level Float Valves
- Auxiliary Fuel Tank Transfer / Vent Flange
- Oxygen / FAS Sample Fittings (6)

**Notes:**
Here we have the location of penetrations on the CWT
NEA injection nozzle
Thermocouples which are routed to the desired location
Oxygen / FAS Sample Return fitting
Hi Level Float Valves and the transfer / vent flange which were previously discussed
Oxygen / FAS Sample Tubes (6)

## Instrumentation – cont.737 CWT

- Instrumentation – cont.737 CWT

**Notes:**
There are 12 suspended thermocouples, 4 in each bay, located 3-6 inches from the upper and lower surface
There are 4 surface mounted wall thermocouples, one on the forward and rear spar, as well as each of the tank side walls
There are 6 surface mounted floor thermocouples, 2 centered in each bay
There are 2 surface mounted ceiling thermocouples, one centered aft in bay 1, the other centered forward in bay 3
Finally there is a thermocouple located in the fuel sump area approximately 1/8th inch off the floor surface

## Instrumentation – cont.Auxiliary Fuel Tank

- Instrumentation – cont.Auxiliary Fuel Tank

**Notes:**
One of the wet bay doors has been modified with fittings to allow the thermocouples and sample tubes access into the auxiliary tank
There are 2 upper and lower thermocouples suspended about 6 inches from the top and bottom surface of the tank
There are 2 sample tubes suspended adjacent to the upper thermocouples

## Future Work

- Facility will be a key tool for continued fuel tank inerting and flammability research
- Study the affect varying surface temperatures have on flammability
- Potential industry tool to validate new inerting systems and methodologies
- Use facility to validate a variety of models for studying fuel tank inerting and flammability

**Notes:**
The FAA envisions the Facility to be a key tool for continued fuel tank inerting and flammability research
Some examples of future experiments include studying the affect changing surface temperatures may have on flammability
Potential industry tool to validate proto-type systems and methodologies 
Or to use the facility to validate a variety of models for studying fuel tank inerting and flammability

## The Fourth Triennial International Aircraft Fire and Cabin Safety 

**The Fourth Triennial ****International Aircraft Fire and Cabin Safety **
**Research Conference**

**The Fourth Triennial ****International Aircraft Fire and Cabin Safety **
**Research Conference**