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A A Technical Review Technical Review of Methodologies for of Methodologies for Calculating Firefighting Agent Quantities Calculating Firefighting Agent Quantities Needed to Combat Aircraft Crash FiresNeeded to Combat Aircraft Crash Fires
Hughes Associates, Inc.SRA , International
FAA, Hughes Technical Center
Summary
PurposePurpose• Large frame aircraft may pose new challenges
– Full length, multi‐deck passenger levels– Increased fuel loads– Widespread use of composite materials
• Is the current “critical area”
concept adequate for these new challenges?
THERE IS NO COMPELLING REASON TO SIGNIFICANTLY REVISE THE NFPA 403
QUANTITIES OR METHODOLOGY
ApproachApproach
• Review historical basis• Conduct airport accident
review
• Conduct hazard analysis• Assess methodology
Review Historical BasisReview Historical Basis
• Analysis– RFFP 1970‐1972– GBA 1971 – EASAMS 1972– ARAC 2004
• Regulatory– CFR Part 139– ICAO ANNEX 14– NFPA 403 ‐2009
• Guidance ‐
FAA AC 150/5210‐6D (NFPA 403)
TCA, PCA, & Concept of Q TCA, PCA, & Concept of Q ––
Agent Agent Needed to Protect OccupantsNeeded to Protect Occupants
Q1
– ControlQ2
– Continued fire control and/or completeextinguishment
Q3
– Combat interior aircraft fire (NFPA 403)QT
= Q1
+Q2
+Q3
QQ 11
• Q1
= PCA x R x T, where:– T = time of application
(1 min for control of the PCA)
• TVEH RESP
+ TControl
≤
TOCC EXP
• 2 min + 1 min = 3min
– R = foam application rate
(e.g., 0.13 gpm/ft2
for AFFF)
SummarySummary
ofof
CurrentCurrent
MethodologyMethodology• Technical Basis TCA/PCA Concept and “Q”
agent quantities
– Test data– Hazard analysis– Crash data
• AC Categories (Indexes) based on L X W• Q1
–
maintain fuselage integrity• Q2
– final extinguishment (not necessarily a rescue path)• Q3
– NFPA interior attack (NFPA 403 only)• FAA CFR – More than NFPA Q1
; less than Q1
+Q2– extinguish the aircraft footprint?
• FAA AR 150/5210‐6D = NFPA 403• ICAO – NFPA 403 Avg
Q1
+Q2
Airport Accident ReviewAirport Accident Review• ARFF Assisted Accidents are Infrequent but do Occur
– 73 ARFF Response to Actual Fire Incident (1230 reviewed
1992‐present)• 11 – non‐survivable• 33 ‐
occupants self evacuated (Unassisted)• 29 – ARFF assisted
– Passengers ambulatory –
most evacuate before ARFF arrival
– Fatal crashes – ARFF may assist in evacuating some occupants
HazardHazard
AspectsAspects
fromfrom
LossLoss
DataData
• Fuel Spill Size– Historical – 26 of 33 incidents
< 53% of L X W– No quantitative way to
predict the spill size and
growth –
assume unlimited
spill size potential in the
anaklysis• ARFF Response Times• ARFF Fire Control Times/Agent
Quantities• Interior firefighting ?
ReaffirmReaffirm
PerformancePerformance
ObjectivesObjectives
• Protect ambulatory occupants – prevent heat penetration to intact
aircraft
• Prevent thermal threat to evacuating passengers
• Have sufficient agent to:– Establish safe area for continuous rescue and recovery
efforts
– Affect final extinguishment of all exterior and interior fires
Fuel spill areaFuel spill area
Fuel spill areaFuel spill areaFuel spill area 2Fuel spill area 1 Fuel spill area 2Fuel spill area 1
Fuel spill areaFuel spill area
Fuel spill areaFuel spill area
Spill area at t1
Spill area at t2 Spill area at t3
Spill area at t4
Spill area at t5
Spill area at t1
Spill area at t2 Spill area at t3
Spill area at t4
Spill area at t5
Spill area at t1
Spill area at t2
Spill area at t3
Spill area at t4
Spill area at t5Spill area at t1
Spill area at t2
Spill area at t3
Spill area at t4
Spill area at t5
AB C
D
E
F G
LaLa La La
Initial spill offset distance, Si
Unlimited dimension
La La
Initial spill offset distance, Si
Unlimited dimension
Performance CriteriaPerformance Criteria• Intact fuselage !!!!• Performance criteria
– Prevent ignition of interior
• Melting of Al due to high
heat flux
• Skin/insulation heat
transfer ( data and
modeling)
– Prevent thermal threat to
occupants who have
exited the aircraft• Pain threshold ‐
2.5 kW/m2
Exposure Flux (kW/m2)
0 20 40 60 80 100 120 140 160
Pred
icte
d Ig
nitio
n Ti
me
(min
utes
)
0
1
2
3
4
5
6
7
8
Exposure Flux (Btu/s-ft2)
0 2 4 6 8 10 12 14
0.5 mm (0.02 in) thick skin1.0 mm (0.04 in) thick skin1.5 mm (0.06 in) thick skin2.0 mm (0.08 in) thick skin2.5 mm (0.10 in) thick skin
Low heat flux model
High heat flux model
Exposure Flux (kW/m2)
0 20 40 60 80 100 120 140 160
Pred
icte
d Ig
nitio
n Ti
me
(min
utes
)
0
1
2
3
4
5
6
7
8
Exposure Flux (Btu/s-ft2)
0 2 4 6 8 10 12 14
0.5 mm (0.02 in) thick skin1.0 mm (0.04 in) thick skin1.5 mm (0.06 in) thick skin2.0 mm (0.08 in) thick skin2.5 mm (0.10 in) thick skin
Low heat flux model
High heat flux model
AgentAgent
QuantityQuantity
• Volume 1 (Q1
)– Prevent interior aircraft ignition– Delivered over 60 seconds
• Volume 2 (Q2
)– Suppress fire to allow safe egress– Not time dependent
• The distance needed to be extinguished for a “favorable”
outcome
–
based on 0.13 gpm/1 ft2
burning area
La
La
Area suppressed betweent1 and t2 volume of agentapplied during time interval
OffsetSa(t) at t1 Offset
Sa(t) at t2
La
La
Area suppressed betweent1 and t2 volume of agentapplied during time interval
OffsetSa(t) at t1 Offset
Sa(t) at t2
ParametricParametric
EvaluationEvaluation• Aircraft Length
– Cat 9 ( 240 ft)– Cat 6 ( 159 ft)– Cat 4 (89 ft)
• Aircraft skin thickness– 0.02 and 0.1 in. thick
• Skin material– Aluminum and composite– Test 4 min burn through criteria
• Crash rescue arrival (response) time• Wind – 0–20mph
Initial Spill Offset (m)5 10 15 20
Tim
e to
Igni
te P
lane
Inte
rior (
min
)
0
2
4
6
8
10
12
14
16
Initial Spill Offset (ft)0 10 20 30 40 50 60
Time Region IV: fire department arrives afterinterior aircraft ignition
Time Region II: interior aircraft ignitionprevented by suppression fire beyond the 9.59 kW/m² (0.84 Btu/s-ft²) distance
Time Region III: Interior aircraft ignition unavoidable regardlessof suppression actions
Time Region V: interior aircraft ignitionnot predicted
Time Region I: interior aircraft ignitionprevented by suppressing fire to 9.59 kW/m²(0.84 Btu/s-ft²) distance
19.1
m (6
3 ft)
Incident heatflux is 9.59 kW/m²(0.84 Btu/s-ft²) at thisdistance
Initial Spill Offset (m)5 10 15 20
Tim
e to
Igni
te P
lane
Inte
rior (
min
)
0
2
4
6
8
10
12
14
16
Initial Spill Offset (ft)0 10 20 30 40 50 60
Time Region IV: fire department arrives afterinterior aircraft ignitionTime Region IV: fire department arrives afterinterior aircraft ignition
Time Region II: interior aircraft ignitionprevented by suppression fire beyond the 9.59 kW/m² (0.84 Btu/s-ft²) distance
Time Region II: interior aircraft ignitionprevented by suppression fire beyond the 9.59 kW/m² (0.84 Btu/s-ft²) distance
Time Region III: Interior aircraft ignition unavoidable regardlessof suppression actions
Time Region III: Interior aircraft ignition unavoidable regardlessof suppression actions
Time Region V: interior aircraft ignitionnot predicted
Time Region V: interior aircraft ignitionnot predicted
Time Region I: interior aircraft ignitionprevented by suppressing fire to 9.59 kW/m²(0.84 Btu/s-ft²) distance
Time Region I: interior aircraft ignitionprevented by suppressing fire to 9.59 kW/m²(0.84 Btu/s-ft²) distance
19.1
m (6
3 ft)
Incident heatflux is 9.59 kW/m²(0.84 Btu/s-ft²) at thisdistance
Initial Spill
Offset [ft]
Prevent Interior Ignition - Fire Department Arrival Time (min)
1.0 1.5 2.0 2.5 3.0 3.5 4.0
1.6 1,970 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P I.C.N.P
3.3 1,920 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P I.C.N.P
6.6 1,770 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P I.C.N.P
9.8 1,660 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P I.C.N.P
16.4 1,440 gal 2,400 gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P I.C.N.P
19.7 1,340 gal 1,690 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P I.C.N.P
26.2 1,140 gal 1,140 gal 3,500 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P
33 930 gal 930 gal 1,130 gal 5,000+ gal I.C.N.P I.C.N.P I.C.N.P
39 730 gal 730 gal 730 gal 1,300 gal 5,000+ gal I.C.N.P I.C.N.P
46 520 gal 520 gal 520 gal 520 gal 1,100 gal 5,000+ gal I.C.N.P
52 310 gal 310 gal 310 gal 310 gal 310 gal 440 gal 5,000+ gal
59 110 110 110 110 110 110 110
63 none none none none none none none
Initial Spill
Offset [ft]
Assure Occupant Safety Outside AC - Fire Department Arrival Time (min)
1.0 1.5 2.0 2.5 3.0 3.5 4.0
1.6 6,980 gal 8,900 gal‡ 8,900 gal 8,900 gal 8,900 gal 8,900 gal 8,900 gal
3.3 6,980 gal ,850 gal‡ 8,850 gal 8,850 gal 8,850 gal 8,850 gal 8,850 gal
6.6 6,980 gal 8,750 gal‡ 8,750 gal 8,750 gal 8,750 gal 8,750 gal 8,750 gal
9.8 6,980 gal 8,650 gal‡ 8,650 gal 8,650 gal 8,650 gal 8,650 gal 8,650 gal
16.4 7,000 gal 6,040 gal 8,440 gal 8,440 gal 8,440 gal 8,440 gal 8,440 gal
19.7 7,000 gal 6,650 gal 8,340 gal‡ 8,340 gal 8,340 gal 8,340 gal 8,340 gal
26.2 7,000 gal 7,000 gal 4,630 gal 8,140 gal‡ 8,140 gal 8,140 gal 8,140 gal
33 7,000 gal 7,000 gal 6,810 gal 7,930 gal‡ 7,930 gal 7,930 gal 7,930 gal
39 7,000 gal 7,000 gal 7,000 gal 6,420 gal 7,730 gal‡ 7,730 gal 7,730 gal
46 7,000 gal 7,000 gal 7,000 gal 7,000 gal 6,420 gal 7,520 gal‡ 7,520 gal
52 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal 6,880 gal 7,320 gal‡
59 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal
63 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal 7,000 gal
66 6,910 gal
Fuselage
2 min. ARFF Response 3 min. ARFF ResponseSpill
Offset (m)
Q1 (gal)
Q2 (gal)
QT (gal)
Spill Offset
(m)
Q1 (gal)
Q2 (gal)
QT (gal)
0.02 in Al 12 730 7000 7730 16 310 7000 73100.10 in Al 5 1440 7000 8840 10 930 7000 7930
Wind Conditions
2 min. Response 3 min. ResponseSpill
Offset (m)
Q1 (gal)
Q2 (gal)
QT (gal)
Spill Offset
(m)
Q1 (gal)
Q2 (gal)
QT (gal)
0 12 730 7000 7730 16 310 7000 731020 mph, fuselage downwind 22.5 940 8350 9290 27.5 690 8350 9040
20 mph, fuselage upwind 1.5 130 3150 3280 2.5 30 3150 3180
EffectsEffects
ofof
FuselageFuselage
andand
WindWind
Initial Spill Offset (m [ft])
ARFF Arrival Time (min)
1.0 1.5 2.0 2.5 3.0 3.5 4.00.5 (1.6) 7,200 L (1,900 gal)1 (3.3) 7,000 L (1,850 gal)2 (6.6) 6,620 L (1,750 gal)3 (10) 6,230 L (1,650 gal)5 (16) 5,450 L (1,440 gal)6 (20) 5,070 L (1,340 gal)8 (26) 4,300 L (1,140 gal)10 (33) 3,520 L (930 gal)12 (39) 2,750 L (730 gal)14 (46) 1,980 L (520 gal)16 (52) 1,180 L (310 gal)18 (59) 430 L (110 gal)
19.1 (63) none
44
MinMin
BurnthroughBurnthrough
Criteria Criteria –– Prevent IgnitionPrevent Ignition
Initial Spill Offset (m [ft])
ARFF Arrival Time (min)
1.0 1.5 2.0 2.5 3.0 3.5 4.0
0.5 – 19.1(1.6 – 63)
26592 L(7,000 gal)
20 (66) 26,110 L (6,910 gal)25(95) 24,180 L (6,400 gal)30 (98) 22,240 L (5,880 gal)35 (115) 20,310 L (5,370 gal)40 (131) 18,370 L (4,860 gal)45 (148) 16,440 L (4,350 gal)50 (164) 14,510 L (3,840 gal)60 (197) 10,640 L (2,810 gal)70 (230) 6,770 L (1,790 gal)80 (262) 2,900 L (770 gal)85 (279) 968 L (260 gal)
87.5 (287) none
4 Min 4 Min BurnthroughBurnthrough
CriteriaCriteria –
EgressEgress
to Safe Areato Safe Area
Response Region I, 2 min Arrival Time
CAT Est. Q1 +Q2
NFPA Q1 +Q2
NFPA - Est. NFPA QT
NFPA - Est. QT QT
FAA QT
FAA - Est. QT QT
9 7730 7070 -660 9570 1840 6000 -17306 3590 2500 -1090 3750 160 1500 -20904 1330 740 -590 1340 10 100 -1230
Response Region I, 3 min Arrival Time
CAT Est. Q1 +Q2
NFPA Q1 +Q2
NFPA - Est. NFPA QT
NFPA - Est. QT QT
FAA QT
FAA - Est. QT QT
9 7310 7070 -240 9570 2260 6000 -13106 3250 2500 -750 3750 500 1500 -17504 1250 740 -510 1340 90 100 -1150
Response Region II, 2 min Arrival Time
CAT Est. Q1 +Q2
NFPA Q1 +Q2
NFPA - Est. NFPA QT
NFPA - Est. QT QT
FAA QT
FAA - Est. QT QT
9 8130 7070 -1060 9570 1440 6000 -21306 3760 2500 -1260 3750 -10 1500 -22604 1400 740 -660 1340 -60 100 -1300
Response Region II, 3 min Arrival Time
CAT Est. Q1 +Q2
NFPA Q1 +Q2
NFPA - Est. NFPA QT
NFPA - Est. QT QT
FAA QT
FAA - Est. QT QT
9 7520 7070 -450 9570 2050 6000 -15206 3430 2500 -930 3750 320 1500 -19304 2160 740 -1420 1340 -820 100 -2060
CAT NFPA Q1
Est. Gal to Supp (L xW)
NFPA Q2
NFPA Q1+ Q2
FAA QT
9 2619 5957 4451 7070 6000
8 2095 4967 3185 5280 40007 1585 2864 2045 3630 30006 1245 1775 1245 2490 15005 863 1030 647 1510 CFR
4 468 807 247 740 CFR
Agent to Suppress Engulfed Aircraft Agent to Suppress Engulfed Aircraft (Gal of AFFF) (Gal of AFFF)
SummarySummary
ofof
HazardHazard
AnalysisAnalysis• If fire immediately ”immerses”
aircraft, ARFF may be
ineffective, – Even with quick (2 min) response– Benefit of new 4 min burn though criteria
• Q1
and Q2
conservatively estimated– Fuselage length is key parameter– Others factors are not predictive –
occupant and fuel
load • Other potential factors
– Composites– Debris field
• What about interior firefighting?
Composite Fire Hazard AssessmentComposite Fire Hazard Assessment
• Small scale –
0.56–0.91 gpm/ft2
• 4 gal/ft2@60 gpm
China Lake tests
• NFPA Class A material extinguishment– 16.4 MW/100 gpm– Efficiency –
25–50%
-or-
ARFF
Q1
ARFF
Q2
Extra Agent Required?
ARFF
Q1
ARFF
Q2
Q3 + mop upNo or minimal extra agent
Torch Ignition 1 minute after ignition 1.5 minutes after ignition
2.5 minutes after ignition 4 minutes after ignitionTorches Out
CFRP Exposed to Torch Burner with Insulation
Backing
15 seconds after torches
out
OngoingOngoingCompositeCompositeTestingTesting
What about InteriorWhat about Interior
Firefighting?Firefighting?
CAT Rep. AC
Est. Man. FFg Flow
(gpm)
Required NFPA 403 Q3
(gpm)5 BAE 146 43 1256 A320 81 1257 B727-200 88 1258 B787 258 2509 B747-200 416 250
45 = Q
Interior FirefightingInterior Firefighting• Indirect firefighting may be only
plausible quick attack– Personnel are unlikely to be able
to mount a quick, interior attack• Limitations of current boom piercing
technology• Agent for interior suppression should
be included in agent calcs• FAA interior materials fire properties
requirements• Conclusion on current Q3
– Cats 5–8 NFPA Q3
is sufficient– Large and multi deck AC (CATS 9–
10) may require additional agent
ExteriorExterior
FirefightingFirefighting
• Exterior Class A fire control
estimate
• Combustibility/contribution of
composites should be
determined
• Q3 quantities for large composite
aircraft ? Cat 10 for B787 until
answers are known?
• Does added debris contribute to
exterior firefighting
requirements?
• Impact of new 4 min burn though
criteria
ImplicationsImplications
ofof
aa
MajorMajor
CrashCrash
Summary of Agent Methodology AnalysisSummary of Agent Methodology Analysis
• NFPA Q1, Q2 and Q3 concepts – Confirmed and revalidated;
– Agent quantities appropriate • Q1 ‐
fuselage protection
• Q2 ‐
provide safe area ( plus secondary agents)
• Q3 – final exterior and interior– subject to validation of exterior firefighting requirements for
large composite AC ( CATS 9‐10)
• Categorization Based on Length is Appropriate
Methodology has been ValidatedMethodology has been Validated• Explicit goals and requirements should be
reestablished in NFPA 403– Assure
• Survivability of ambulatory occupants
• Ability of responders to perform interior fire attack, potential
rescue
of non‐ambulatory survivors, and recovery of victims
– Provide agent to :• Protect aircraft fuselage• Control fire exposing escaping occupants• Establish safe area for continued operations• Affect final extinguishment
• Prevent reignition
RecommendationsRecommendations• NFPA 403 potential modifications
– Clearly state performance goals in Annex B; add the new
FAA reports as updated information– Provide CAT 10 (500gpm/5000 gal ) NFPA Q3 for B787 until
there is test data ? Need for additional Q3 for CATs
9 & 10?
– Explicitly state that 2 deck aircraft (B747 & A380)are Cat 10– Provide an access vehicle and boom piercing nozzle where
multi‐deck aircraft operate• Consider boom technology for CAT 5 and above
– Provide handline
piercing nozzles for other CATS– Improve water resupply guidance/criteria