engine nacelle halon replacement, faa, wj hughes technical center

Engine Nacelle Halon Replacement,FAA, WJ Hughes Technical Center

Point of Contact : Doug Ingerson

Department of Transportation

Federal Aviation Administration

WJ Hughes Technical Center

Fire Safety Branch, AAR-440

Bldg 205

Atlantic City Int'l Airport, NJ 08405 USA

tel: 609-485-4945

fax: 609-485-7074

email: [email protected]

web page: http://www.fire.tc.faa.gov/

International Aircraft Systems Fire Protection Working GroupAtlantic City, NJ USA 30-31 October 2002

Federal Aviation AdministrationWJ Hughes Technical Center, Fire Safety Section, AAR-440


Major Topics for Review :

brief overview

revision to minimum performance standard for engine/apu (mpse)

foundation test plans and results

near term plans




BRIEF OVERVIEW April - July 2002, Testing

Encountered difficulty with hot surface ignition (HSI) during initial MPSE tests

Ran series of tests and observed HSI behavior - determined phenomena is unreliable

Reviewed a sample of reported HSI behaviors

Results indicated current version of the MPSE was faulted by HSI unreliability

Ran 100+ plus tests to find a way to circumvent HSI unreliability

23 & 24 July 2002, Task Group Meeting

Convened and discussed issues involving MPSE and HSI

Agreed MPSE required revision

Conceived method to track Halon 1301 suppression performance using HSI reliably

Formulated rough revision of MPSE (revision 3)

Planned foundation testing to resolve potentially complicating issues

August 2002 - Present

Produced a crude flowchart of MPSE revision 3

Partially completed the foundation testingInternational Aircraft Systems Fire Protection Working Group

Atlantic City, NJ USA 30-31 October 2002



REVISION OF THE MPSE Evaluating the Basis for the Agent Comparison in the MPSE

MPSE process will have error in results due to environmental behaviors observed to date - conservatism is required, yet error must be minimized where possible

Experienced/reported difficulty with reliable HSI behavior would lead to greater expected error in final results

Equivalence method must represent the associated application in a reliable manner

Equivalence method relies on the occurrence of HSI as it is a threat in this application

Testing during :

April - June 2002; the continually operating electrodes (COE) or a tube array of particular geometry reliably reignited JP-8

June - July 2002; primary ignition difficulty with low volatility fuel (oil) in the spray fire scenario - suspected impact on HSI behavior using the COE alone

July - August 2002; a combination of the COE and the tube array provided reliable HSI behavior for any fuel type evaluated




REVISION OF THE MPSE The Significant Change to the MPSE

Former version of the MPSE

reliance upon the definition of a “robust” fire

equivalence process required finding a minimum of 3 robust fires

the robust fire was a mixture of test conditions that would be extinguished by Halon 1301 for a portion of a fixed number of duplicate tests (80-90%)

a successful quantity of the replacement candidate was to repeat Halon 1301 behavior against the same conditions

HSI in this geometry is an imprecise behavior and was “buried” in the robust fire

Version 3 of the MPSE

robust fire eliminated

changed performance measure to “Reignition Time Delay” - the time between fire extinguishment and reignition which is based on a video review of the test

“Reignition Time Delay” (RTD) is based on a minimum of 5 tests at like condition

a successful quantity of a replacement candidate will be required to repeat or exceed the RTD for Halon 1301 at the same test conditions

HSI is provided for with intentional secondary ignition sourcesInternational Aircraft Systems Fire Protection Working Group




REVISION OF THE MPSE Items of Concern for MPSE revision 3

Concerns are included for consideration in MPSE revision 3 to improve on the body of work to date

Concerns are reasoned as impacts on the credibility of the final results

compartment ventilation conditions

agent storage, release, and distribution

sufficient severity of the fire threat

variation in the RTD must be observed and understood

Concerns will be addressed with foundation testing and review of others’ work

Retain portions of previous MPSE revision to minimize loss of time




REVISION OF THE MPSE Spray Fire Zone Configuration, MPSE revision 3

FUEL NOZZLES

2” TALL FLAME

STABILIZATION

RIB

TUBE ARRAY

AIRFLOW

FWD

UP

CORE

Section A-A

AIRFLOW

SURFACE TEMPERATURE

MEASUREMENT POINT

FWD

UPSection A-A




REVISION OF THE MPSE Spray Fire Zone Configuration, MPSE revision 3

AIRFLOW

FWD

UP

FUEL NOZZLES

2” TALL FLAME

STABILIZATION

RIB

TUBE ARRAYCORE

ELECTRODES

sta

502

sta

510




REVISION OF THE MPSE Process Overview

Parameter for comparing agent suppression performances is RTD; not robust fire

RTD is the duration of time between fire extinguishment and reignition

RTD requires a test fixture which includes RELIABLE secondary ignition sources

Primarily, a single RTD will represent a group of duplicate agent suppression tests

Basis for success : RTD Halon 1301 RTD Candidate replacement

Testing will account for representative :

ventilation conditions

agent storage and discharge considerations

fuels types in a nacelle/APU

fire scenarios

Process will allow for rational test planning

test against the most challenging condition(s)

run verification tests against conditions not explicitly evaluated

attempting to separate fire suppression and agent distribution performancesInternational Aircraft Systems Fire Protection Working Group




REVISION OF THE MPSE Process Overview (continued)

FIND CERTIFICATIONDISTRIBUTION FOR

HALON 1301 IN SIMULATOR

SELECT FIRECONDITIONS IN

SIMULATOR

RUN SPECIFIEDNUMBER OF FIRE

EXTINGUISHMENT TESTS

CALCULATE RTD FORHALON 1301 FIRE

EXTINGUISHMENT TESTS

RUN FIREEXTINGUISHMENT

TESTS

CALCULATE RTDFOR REPLACEMENT

CANDIDATE

CHANGETO REPLACEMENT

CANDIDATE

CONTINUE

START

END

CHARACTERIZEDISTRIBUTION OF THE

REPLACEMENT CANDIDATE

IS RTDACCEPTABLE

?

ALTER QUANTITYOF REPLACEMENT

CANDIDATE

SELECT VENTILATIONCONDITIONS

IN SIMULATOR

NO YES




FOUNDATION TESTING Test Results - Purpose and General Comments

Testing to :

answer questions conceived during initial discussions of MPSE revision 3

provide data to observe behaviors and uncover issues not initially recognized

Focused on previously stated concerns

List of issues to be addressed by this testing

verify the fire threats are sufficiently severe

minimize/understand varying RTD behavior

fuel type - observe/compare combustion behaviors

agent discharge - consistent preburn or tube array temperature

material changes in the tube array - determine its life span

explore residual fire scenario - determine :

which fuel types can burn in this configuration

the significance of HSI phenomena

the effect of the orientation of the pan geometry on fire intensity




FOUNDATION TESTING Test Results (continued) - Spray Fire Zone Orientation

AIRFLOW

FWD

UP

TUBE ARRAY

STA

527

STA

510

STA

518

STA

532

STA

532




FOUNDATION TESTING Test Results (continued) - Varying RTD/Decision to Release Agent

Run a series of spray fire tests and evaluate resulting RTDs

Purposes :

determine if RTD variation can be better controlled by releasing the agent after :

a consistent preburn duration expires

a consistent temperature in the tube array is attained

use results to refine MPSE version 3

Current test procedure relies on preburn duration

Control of the test article changed for the trials involving tube array temperature

Conditions :

air flow 2.2 lbm/s @ 100°F

JP-8 0.25 gpm

agent HFC-125 @ 5.2 lbm

Fixed preburn duration 45 seconds

Fixed tube array temperature 1440°F




FOUNDATION TESTING Test Results (continued) - Varying RTD/Fuel-Spray Fire Intensity

Ran spray fire tests and recorded temperature profiles

Purposes :

observe fire behaviors

compare energy signature for each fuel type/ventilation condition

use data in refining MPSE revision 3

Thermocouples spaced longitudinally in the flame path to provide representative picture of combustion behavior

Each individual test condition was repeated 3 times

Fixture cooled down to near ambient condition between tests

Test conditions :

fuels : JP-8, oil (Mobil Jet Oil II), & hydraulic fluid (Skydrol LD-4)

fuel flow rates : 0.25 gpm +/- 0.03gpm

ventilation conditions : 2.2 lbm/s@100°F & 1.0 lbm/s@300°F

no fire suppression agent released




FOUNDATION TESTING Test Results (continued) - Varying RTD/Fuel-Spray Fire Intensity

Created averaged temperature profile from data for each set of 3 tests

8 thermocouples, sta 453, 4” (102 mm) & 8” (204 mm) above core, 2@01:30, 04:30, 07:30, & 10:30

1 thermocouple buried in tube array, approximately sta 510 (“515”), 12:00

1 thermocouple mounted on door exterior, sta 514, 11:30

2 thermocouples, sta 518, 4” & 8” above core, 12:00

4 thermocouples, sta 532, 4” & 8” above core, 2@01:00, 11:00

6 thermocouples, sta 551 upper, 4” & 8” above core, 2@01:30, 10:30, 12:00

Calculated a relative “heat” production reference to compare combustion intensity

calculated areas under the averaged temperature traces from 30 to 80 seconds

summed all areas for thermocouples affected by fire (sta’s 510, 514, 518, 532, 551)

subtracted area for sta 453 thermocouples to remove “heat” present in air stream




FOUNDATION TESTING Test Results (continued) - Residual Fire Investigation/Fuel Ignition

Ran pool fire tests and recorded temperature profiles

Purposes

determine which fuels can be ignited in the residual fire scenario

use data to refine MPSE revision 3

Fixture geometry :

master fuel pan in the simulator filled to make a water bath

smaller stainless steel fuel pan located in the water bath

Test conditions :

fuels : JP-8, oil (Mobil Jet Oil II), & hydraulic fluid (Skydrol LD-4)

fuel quantity : 0.47 gallon (1” deep puddle) in 10.5” x 10.3” x 1.5” deep pan

fuel temperature prior to test : 150°F+ (by thermocouple submerged in fuel)

ignition exposure : 10 - 30 seconds intermittently for 3 minutes

ventilation conditions : 2.2 lbm/s@100°F & 1.0 lbm/s@300°F

no fire suppression agent released




FOUNDATION TESTING Test Results (continued) - Residual Fire Orientation

AIRFLOW

FWD

UP

These assemblies not

present during testing

STA 502

MASTER

FUEL PAN

CH4 NOZZLE & ELECTRODES

(shown out of position)

INSERT FOR FUEL PAN

S

TA

527

CORE




FOUNDATION TESTING Test Results - Conclusions

Fire intensity

clean simulator cross section was an insufficient threat

secondary ignition elements required to maintain sufficient threat

Varying RTD

no significant difference noted between releasing agent based on consistent preburn or tube array temperature

fuel types have varying energy signatures - expect impact on RTD to be noticeable

JP-8 worst case for 2.2 lbm/s air flow@100°F

oil selected as worst case for 1.0 lbm/s air flow@300°F

tube array has a life span of 10 fire tests

variation in environmental conditions observed as a noticeable impact

Residual fire scenario

JP8 was the only fuel ignited - oil and hydraulic fluid were not

remaining tests are incompleteInternational Aircraft Systems Fire Protection Working Group




NEAR TERM PLANS Complete foundation testing

Determine the impact/relevance of HSI on the residual fire scenario

Determine the impact of altering the fuel surface geometry in the residual fire scenario on combustion intensity

Ultimately, need to “bench-mark” Halon 1301 in this scenario in some manner

Finalize MPSE revision 3

Discuss/resolve issues

incorporate results of foundation testing completed to date

agent - storage/distribution criteria

final process - need to methodically evaluate replacement candidates without excessive test counts

Commit process to paper

Complete Testing for the replacement candidates by Jun 2003




engine nacelle halon replacement, faa, wj hughes technical center

Documents

reliable hsi behavior

hsi unreliability23

occurrence of hsi

hsi unreliabilityran

hsiagreed mpse

hot surface ignition

imprecise behavior

robust firesthe robust