1. 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 Section, AAR-422
Bldg 205
Atlantic City Int'l Airport, NJ USA
tel:
fax:
web page:
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

2. Major Topics for Review :
Project Progress
Difficulties With Hot Surface Ignition
Response To Hot Surface Ignition Difficulties
Near Term Plans
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

3. PROJECT PROGRESS April 1ST, 2002 - Nacelle Fire Testing
Five tests run against established Halon distribution
Five tests resulted in complete extinguishment
Ran fuel/air mixture through test article looking for hot surface IGNITION after the successful five test sequence
Hot surface did not IGNITE mixture
Forward motion halted and an investigation began
April 1ST, Test Conditions
Air flow : °F
Fuel : JP8, °F
Agent : Halon 5.2#, 100°F, 41 lbf/ft^3
Hot Surface Temperatures : Average of 4 thermocouples => °F
Single point maximums = °F
Preburn : 20 seconds
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

4. Massive Hot Plate Geometry
DIFFICULTIES WITH HOT SURFACE IGNITION
Massive Hot Plate Geometry
Located at 12:00 in the core beneath fuel spray
350 lb steel assembly
Electrically heated
APPROXIMATE
HOT PLATE
THERMOCOUPLE
POSITIONS
AIRFLOW
FASTENING
BOLTS
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

5. DIFFICULTIES WITH HOT SURFACE IGNITION
Reviewing Fire Test Requirements of the Minimum Performance Standard for the Engine and APU Compartments (MPSE)
Fire test requirements are a subset of the larger procedure
Run a minimum of five tests against the established Halon 1301 distribution
Demonstrate an extinguishment performance of %
Meaning that of 5 tests run, 4 result in complete extinguishment
The “failed” test requires that a hot surface IGNITE the fuel spray after the conditions of the initial flame extinguishment subside
Attain prescribed extinguishment performance by adjusting the fire intensity with the following parameters (in priority) :
Fuel flow rate
Hot surface temperature
Successful extinguishment is defined as an 8 second duration between initial flame extinguishment and the REIGNITION of the fire
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

6. Evaluating Non-existent Hot Surface Ignition
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Evaluating Non-existent Hot Surface Ignition
Reasoned two options as allowing inadequate hot surface IGNITION threat
Insufficient fuel flow rate
Insufficient hot surface temperature
Fuel flow Rate : Test fixture being run at highest desirable fuel flow rate
At 0.2 gpm, liquid fuel observed to roll off core surfaces
Resultant test fire observed having a flame length of roughly 10 feet
Prior fires fueled at higher flow rates resulted in damage to the test section
Increasing fuel flow is deemed an undesirable option
Hot Surface Temperature : Only remaining remedy for existing geometry
Ran 15 tests with the existing massive hot plates, April 5-15, 2002
Tests configured to favor hot surface IGNITION
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

7. Massive Hot Plate Testing, April 5-15, 2002
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Massive Hot Plate Testing, April 5-15, 2002
Tests run to maximize hot surface ignition
no agent released
removed agent cooling - although perceived as negligible against a massive hot plate
removed agent interactions potentially retarding/complicating hot surface IGNITION behavior
fuel flow turned off for 8 seconds
duration began when the agent was supposed to be released
simulated the initial extinguishment by stopping fuel flow
removed the cooling effects of the fuel on the massive hot plate - again perceived as negligible against a massive hot plate
fuel flow resumed at the expiration of the 8 seconds without electrical ignition while looking for hot surface IGNITION
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

8. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Time Line for Massive Hot Plate Tests Investigating Hot Surface Ignition
FIRE IGNITED
ELECTRICALLY
FUEL FLOW
TURNED OFF
RESUMED WITHOUT
ELECTRICAL IGNITION 8
SECONDS
PREBURN
COOL DOWN 30 5
BEGIN
TEST,
t = 0
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

9. Massive Hot Plate Testing, April 5-15, 2002 (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Massive Hot Plate Testing, April 5-15, 2002 (continued)
Test Parameters
Air flow : °F
Fuel : JP8, °F
Hot Surface Temperatures : Average of 4 thermocouples => °F
Single point maximums => °F
Preburn : seconds
Secondary Fuel Flow Duration : 5 seconds
Test Results
One hot surface IGNITION out of 15 tests
Pertinent conditions for the hot surface IGNITION; average = 1180°F, maximum single point = 1328°F, preburn = 10 seconds
Two tests run with higher maximum single point temperatures AND equivalent or longer preburn durations without hot surface IGNITION
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

10. Massive Hot Plate Testing, April 5-15, 2002 (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Massive Hot Plate Testing, April 5-15, 2002 (continued)
Anecdotal Experience
Massive hot plates formerly provided sufficient IGNITION energy to REIGNITE the fuel/air mixture
Improper fuel control operations during April test sequences resulted in sporadic hot surface IGNITION
Fastening bolts shown in previous photograph observed glowing red during testing
Hot surface behavior during experience did not produce 100% IGNITION
Conclusions
Current massive hot plates are incapable of reliable hot surface IGNITION threat
Hot surface IGNITION itself is an enigmatic phenomena
Begin looking deeper for a solution to this difficulty
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

11. Considerations Regarding the Hot Surface and the MPSE
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Considerations Regarding the Hot Surface and the MPSE
The concept of the MPSE relies on the hot surface IGNITION threat to push the established Halon 1301 distribution to near failure
This verifies that the fire is not too “weak” for a given agent distribution
“weak” fires can not withstand indirect extinguishment effects such as flame strain or other potentially unrecognized effects given new suppression technologies
A “weak” fire can be reasoned as a mechanism that would allow inadequate quantities of a replacement candidate/system to perform equivalently to Halon 1301
The current version of the MPSE will not allow an insufficient quantity of a replacement candidate/system to perform equivalently to Halon 1301, given the hot surface IGNITION threat
The hot surface IGNITION threat is a valid consideration for the engine application
The hot surface IGNITION threat is being used as a tool to verify the test fire is of sufficient intensity; not as a direct extinguishment goal
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

12. Review Experience/Literature Addressing Hot Surface Ignition
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Review Experience/Literature Addressing Hot Surface Ignition
Review experience of others by contacting :
FAA, WJ Hughes Technical Center, C. Sarkos, R. Hill, D. Blake, and H. Webster
USAF, Wright-Patterson Air Force Base (WPAFB), J. M. Bennett and J. Tucker
USN, USN Lakehurst, W. Leach and M. Tedeschi
NIST, A. Hamins
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

13. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Review Experience/Literature Addressing Hot Surface Ignition (continued)
Review Literature
AFRL-VA-WP-TR , “Aircraft Engine/APU Fire Extinguishing System Design Model (HFC-125),” J.M. Bennett, M.V. Bennett
WL-TR , “Halon Replacement Program for Aviation / Aircraft Engine Nacelle Application Phase I, Operational Parameters Study,” M.L. Kolleck, J.M. Bennett, J.A.Wheeler, G.M. Caggianelli
NIST SP 890, Volume II, “Suppression of Engine Nacelle Fires,” A. Hamins, et al
AFWAL-TR , Volume II, pt. I, “Vulnerability Methodology and Protective Measures for Aircraft Fire and Explosion Hazards / Fire Detection, Fire Extinguishment, and Surface Ignition Studies,” A.M. Johnson & A.F. Grenich
AFAPL-TR , “Dynamic, Hot Surface Ignition of Aircraft Fuels and Hydraulics Fluids,” D.J. Myronuk
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

14. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Results of Review
“weak” fire behavior observed in early work at FAA Technical Center
supports concept of challenging a given agent distribution; potentially to failure
MPSE addresses concept through hot surface IGNITION threat
Autoignition data produced via standardized test method DOES NOT relate to hot surface IGNITION phenomena
At a minimum, hot surface IGNITION alone is dependent upon multiple factors of :
aerodynamic characteristics of the compartment ventilation
the geometry of the fire zone
fuel volatility
characteristics of the material bathed in the fire - thermal conductivity, emissivity, etc.
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

15. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Results of Review (continued)
Hot surface IGNITION has a threshold tendency which is dependent upon the installation
Hot surface IGNITION was addressed during the development of the HFC-125 design model produced from the Survivability group at Wright-Patterson Air Force Base
Hot surface IGNITION was used by the USN during system development for the F-18 E/F to validate Halon 1301 replacement
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

16. Results of Review (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Results of Review (continued)
USAF/WPAFB experience
hot surface is 1” plate of 30” length and 100° arc on a 36” diameter
halon replacement effort was based on fire behavior (not gaseous concentration)
the “successful” replacement agent mass was a result of a minimum of 4 iterative cycles against the same test conditions
the test conditions were altered to represent a wide range of operational conditions
during phase one work, the significant fire dynamic parameters in an engine nacelle fire were uncovered by using the quantity of agent needed to extinguish any given fire as the control variable
during this work, hot surface IGNITION revealed itself as a problem that could alter the determination of the “successful” agent mass for a given test series
the final results :
hot surface IGNITION was found to be a MAJOR factor in determining how much agent was required to suppress a nacelle fire
if hydraulic fluid was used for testing, the spray was stopped at agent release
if JP8 was used for testing, the spray operated 5 seconds beyond agent release
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

17. Results of Review (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Results of Review (continued)
USN/USN Lakehurst experience
Hot surface was a particular geometry of 4 tubes subject to flame impingement
Fire intensity was observed to vary with preburn duration
Quantity of replacement candidate was based on a fire threat sized to the existing Halon 1301 fire extinguishing system installed on the airframe
The tube array had a finite lifetime with respect to reproducible test results
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

18. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Developed Plan to Alleviate Hot Surface IGNITION Difficulties
Desired to maintain a method to challenge the established agent distribution in the same spirit as the massive hot surface IGNITION threat
Conceived 3 options to potentially alleviate difficulties where each provides :
an IGNITION source to potentially REIGNITE the fuel/air mixture after initial extinguishment
better ability to characterize the performance of the established Halon 1301 gas distribution
Concept of “reignition delay” must now be defined as it is used as a metric for comparison
time between fuel/air mixture hitting a hot surface and its IGNITION OR
time between no-flame-observed (“fire extinguishment”) and the subsequent REIGNITION of the fuel/air mixture
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

19. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Developed Plan to Alleviate Hot Surface IGNITION Difficulties (continued)
Three options for evaluation; looking specifically for reliable secondary ignition
Tube array
heated strictly by preburn duration; tubes started at ambient temperature
expected increasing surface temperature (via increasing preburn) would decrease REIGNITION delay
ran through four versions before finding “reliable” configuration
Hot block
small block located in fuel/air flow field that was electrically heated
expected increasing surface temperature would decrease REIGNITION delay
ran through four versions before discontinuing effort
Continuously operating electrodes
used the electrical ignition source that initially starts the test fire
ran electrodes continuously throughout the length of the entire test
expected consistent reignition delay; agent mass and ventilation condition were reasoned as the sole impacts on any variation found in this concept
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

20. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array
Array located in an intense region of the spray flame; determined visually
Tube array positioned downstream from flame stabilizing rib between 8” - 10”
Tubes bent on an approximate radius of 14-1/2”; supported approximately 2-1/2” above core surface
FUEL NOZZLES
2” TALL FLAME
STABILIZATION
RIB
TUBE ARRAY
AIRFLOW
FWD UP
CORE
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

21. Tube Array (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array (continued)
All tubes were 1/2”OD, grade 304 stainless steel
Supported in place with structure not subject to flame impingement
Tubes positioned by the lowest, most forward tube in the array
AIRFLOW
FWD UP
VERSION #1
Singular tube
VERSION #2
Tube spaced horizontally on 1” centers
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

22. Tube Array - Horizontal Assembly (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Horizontal Assembly (continued)
AIRFLOW
FWD
FUEL NOZZLES
TUBE ARRAY
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

23. Tube Array (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array (continued)
VERSION #3
Tubes aligned on an axis and rotated
approximately 45° from horizontal
about the lower, forward tube
AIRFLOW
FWD UP
VERSION #4
Tubes stacked so centers
correspond to the corners of a rhombus
SURFACE TEMPERATURE
MEASUREMENT POINT
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

24. Tube Array - Diagonal Stack (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Diagonal Stack (continued)
FUEL NOZZLES
TUBE ARRAY
FWD UP
AIRFLOW
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

25. Tube Array - Rhombus Stack (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Rhombus Stack (continued)
FWD UP
CORE
TUBE ARRAY
FUEL NOZZLES
2” TALL FLAME
STABILIZATION
RIB
AIRFLOW
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

26. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Test Timeline
( identified in later discussion of the results as “NFN” fuel control )
FIRE IGNITED ELECTRICALLY;
ELECTRODES TURNED OFF AFTER
OPERATING FOR 5 SECONDS
FUEL FLOW
TURNED OFF
RESUMED WITHOUT
ELECTRICAL IGNITION 8
SECONDS
PREBURN
COOL DOWN 30
5 - 20
BEGIN
TEST,
t = 0

27. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Test Timeline (continued)
( identified in later discussion of the results as “Agent Released” )
FIRE IGNITED ELECTRICALLY;
ELECTRODES TURNED OFF AFTER
OPERATING FOR 5 SECONDS
AGENT
RELEASED
PREBURN
COOL DOWN 30
SECONDS
5 - 20
FUEL FLOW
TURNED OFF
BEGIN
TEST,
t = 0
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

28. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Observations
Reignition delay decreased with increased preburn
Threshold behavior observed but not consistent day-to-day
atmospheric conditions ( ?? )
tube material changing with increasing flame exposure ( !! )
Reignition delay values were scattered; occasionally, the same preburn time resulted in contradicting information
Reignition delay increased with increasing agent mass discharged
Agent storage behavior was erratic and may have affected test section air stream which then affected fire behavior preceding/during extinguishment
As tube array complexity increased, frequency of hot surface IGNITION increased
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

29. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Observations (continued)

30. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Tube Array - Observations (continued)
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

31. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly
Versions #1 & #2 supported on core surface loosely by angle iron (concept proof)
All versions located in the spray zone of the fuel nozzles in the spray fire scenario
Positioned the base of block between 1” - 2” above core surface
Forward face positioned downstream from flame stabilizing rib between 8” - 15”
FUEL NOZZLES
2” TALL FLAME
STABILIZATION RIB
HOT BLOCK
AIRFLOW
FWD UP
CORE
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

32. Hot Block Assembly (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly (continued)
VERSION #2
ADDED 1” x 1/2” x 1/8”
PIECE OF STEEL ANGLE IRON
VERSION #1
Basic features are :
1” x 2” x 6” mild steel block
Two 3/4”OD x 6” long cartridge heaters
Electrically heated
3 kW capability
SURFACE TEMPERATURE
MEASUREMENT POINT
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

33. Hot Block Assembly (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly (continued)
VERSION #3
VERSION #4
CHANGE STEEL ANGLE
IRON TO 2” x 1” x 1/8”
ADD STEEL
MOUNTING BRACKET,
2” TALL x 2-1/2” WIDE x 1/8”
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

34. Hot Block Assembly (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly (continued)
ELECTRICAL
CONNECTIONS FOR
THE HOT BLOCK
HOT BLOCK WITH
2” x 1” x 1/8”
ANGLE IRON
FUEL NOZZLES
CORE
FWD UP
AIRFLOW
2” TALL FLAME
STABILIZATION
RIB
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

35. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly - Test Timeline
BEGIN TEST, t = 0; HEATER BLOCK AT
DESIRED SURFACE TEMPERATURE
FUEL FLOW STARTED;
IGNITION ELECTRODES
WERE NOT ENERGIZED
FUEL FLOW
TURNED OFF 30
SECONDS
9 - 30
SECONDS
COOL DOWN
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

36. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly - Observations
Reignition delay decreased with increased surface temperature (time between initial fuel impingement and IGNITION)
Threshold behavior observed but not consistent day-to-day
atmospheric conditions ( ?? )
block material changing with increasing flame exposure ( !! )
aerodynamic flow around block very complex
Reignition delay values were scattered
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

37. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly - Observations (continued)
BLOCK SITTING
APPROXIMATELY 1”
ABOVE CORE SURFACE
BLOCK SITTING
ON 2” TALL
MOUNTING BRACKET

38. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Hot Block Assembly - Observations (continued)
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

39. Continually Operating Electrodes
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes
Operated electrodes throughout the entire fire test
Core surface beneath spray fire was uncluttered
Electrodes run off transformer; 120VAC primary and 10,000 VAC secondary
Geometry of nozzles/electrodes had to be rigidly maintained
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

40. Continually Operating Electrodes (continued)
RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes (continued)
ELECTRODE PAIR
FUEL NOZZLES
FWD UP
AIRFLOW
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

41. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes - Test Timeline
FIRE IGNITED ELECTRICALLY;
ELECTRODES CONTINUED
OPERATING
AGENT
RELEASED
PREBURN
COOL DOWN 30
SECONDS
FUEL FLOW &
ELECTRODES
TURNED OFF
BEGIN
TEST,
t = 0
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

42. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes - Observations
Reignition delay apparently not dependent upon preburn duration
Reignition delay not consistent day-to-day; atmospheric conditions suspected
Reignition delay increased with increasing quantity of agent released
Inconclusive behavior while keeping the discharged agent mass constant with varied fuel flow
REIGNITION occurred for every test run except one; the one that was not initially extinguished
Reignition delay times demonstrated scatter
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

43. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes - Observations (continued)

44. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes - Observations (continued)

45. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Continually Operating Electrodes - Observations (continued)

46. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Comparison of Tube Array and Continually Operating Electrodes
Due to larger scale scatter with the hot block, it was dropped from further consideration
Sequence of 10 tests spread over 3 days; May , 2002
Five tests run against each concept
Test Parameters
Air flow : °F
Fuel : JP8, °F
Agent : Halon 5.2#, 100°F, 41 lbf/ft^3
Evaluating performance of each
between different days
statistical spread (consistency)
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

47. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Comparison of Tube Array & Continually Operating Electrodes (continued)

48. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES
Conclusions.
Given the following :
testing occurred between April 1ST and May 30TH evaluating hot surface ignition based on difficulties experienced regarding this issue
ran 111+ tests in this period of time
discharged 220 lbf of HFC-125 and 80 lbf of Halon 1301
evaluated three potential ignition sources to produce a fire that could be used to characterize or challenge the established Halon distribution in agreement with the spirit of the MPSE, and doing so reliably
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

49. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES Conclusions (continued).
A recommendation is put forward to address the enigmatic problem of hot surface ignition with respect to the MPSE; this recommendation being to use continuously operating electrodes to relieve the difficulties associated with the hot surface IGNITION phenomena which would then permit forward motion in producing equivalency information for the relevant replacement candidates
the massive hot plates in the FAA simulator have exceeded their respective life spans
massive hot plates, based on the experience of personnel at WPAFB, are unreliable when considering hot surface ignition phenomena
hot surfaces are subject to degradation during continual fire exposure
the established Halon distribution profile called for in the MPSE must be challenged or characterized in some manner to acknowledge the peak ability of that very same Halon; circumstances otherwise would open the door to inadequate quantities of a replacement candidate/system as being labeled “equivalent” to the performance of Halon which would then lead to an imbalance in the “equivalent level of safety” concept
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

50. RESPONSE TO HOT SURFACE IGNITION DIFFICULTIES Conclusions (continued).
The basis for recommending continually operating electrodes over the tube array and hot block concepts
regardless of how specified in the MPSE, the challenge to the Halon distribution in the engine application is a turbulent diffusion combustion phenomena; upon initial extinguishment, this phenomena inherently becomes a forcibly ventilated maelstrom requiring a reliable ignition source to obtain full threat ability
hot surface IGNITION, based on previously provided information, simply and utterly complicates the IGNITION component that leads to the secondary combustion process that is specified in the MPSE
issues complicating hot surface IGNITION are not restricted to combustion dynamics alone, but include the materials and geometry actually encompassed in the combustion volume as well
the simple comparison of reignition delay times and their respective statistical behavior for the Halon tests run on May clearly suggests the continually operating electrodes are likely a better option to define the abilities of any associated Halon distribution
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA

51. NEAR TERM PLANS
Continue working with the continually operating electrodes while moving in the direction to provide equivalence data
continue evaluating the performance of this concept
begin rationalizing modifications of the MPSE to incorporate this recommendation
Submit data and other pertinent information to the engine task group for review
Wait for task group comments or plan activities as needed to accomplish the feedback portion of the cycle
International Aircraft Systems Fire Protection Working Group
London, England June 2002
Federal Aviation Administration
WJ Hughes Technical Center, Fire Safety Section, AAR-440
Atlantic City Int'l Airport, NJ USA