## v FUEL SYSTEN Fll<.E HAZARD k.EDUCilm\ The 1oa j()r ;>ourcl' of energy in post crash aircraft fires is the ••

**irvlal1~.:** it•, J supply . In

**ra~"t,** if there is no airplane fuel fi.re , aJmost i'1vari:'l.hly 

## •1•' fi•· of any signifi.ca•Ke devt:lops . Consequently, developing a l!lt!;)ns or mi

**.,;_~i** ··i

**~: .**  •Ill C.O'ltribtlti.o'l nf this fue-l to post crash

**fire~ i~**  nf pri"lP imporL.q;•'' - · do1 :1 b L:li .? , how· ver , the overall aircraft safety on the p,round ancl in fli ·

**t,~**

**mu"~ ut,~**  **·** bL r: 'l'(lrromi:::cd . The application of t!"lis philnb'>phy 'tn

**c: '~r""'~**  **:** ; 1

**ai :.:r.-:~ft**  d•.!Si;2n over the.! past three

**decade~** has res11lterl i•1 :l:1

**c.xcPll~·nL** ..

**~< .**  '".• record . It is incumhcnt upon the industry that this prarlico:: he

**co'1Li -:tt**  **d** "'.• 1 that it be the paramount consideration when evaluating Rystem designs

**intend~~** to

**~educe** the fire hazard i, survivable crashes . An assessment of curr-=:nr

**desi:~n** practices in this rep,ard is revie wed in li r,l-}t c-t opera tiona 1 experience in the following j)eir,J,grnphs . Al ternot i ve nppr•):-'!Chef: tn reduce the post c rash fire potential are described and

**ev~luated** in

**term~** nf an ov<..rd] 1 airplane safety eftectivenesb. Finally, the adequacy of currt.nr '1-r:ci••: ;l AvJ ·lti.on Reeulat ions and

**th( ~**  neen (or

**;nor~** (\:!SC-'lrdl and dl.!llclopment in !.pee I I i

**~r as**  **~re di~cussed**  **.**

**~~SC':.~~mcn t**  of

_ Curre

_ nt Design Adequacy Current Design Practice ThL

**dc ~-;**  **ign** rhiloc;o!)hy whic h has for :;o many years resulted i11 :111 P X(.I.

**lh~n~** r lr , safety record for the aircraft i.ndustry has been to isolate the ;OJi rcratt 

## 'u•: fro•n

**pot~ntial** ignition sources . This isolation ic; funcl-'lmcnt:l1 tn [i.re prr.v.·n tion . Very specific fire safety design requirement,.; are ::>tate<! in thL

**Fe ~r**  **r_,,** Avi.l'lti.on kegul.:ttions requiring the ..tircraft industry to expend a C01l*>idenld··· porli()n of it<; development effort to C01<1ply with

**thes ~**  regulati0., ., , **l!nw~:.:v• r,**  since an excellent safety record by the industry is mdndMtory tu mai.,t&ininn

**t~ r** 

**good~ill** of the traveling public , the design **rel'juir~mcnls di·~tatl**  d by Lhc rPgulRtions .:tr0 often exceeded . The application of these regulations fall into three major

**c~tcRnri~~:** powerplant fire protection, fuel system fire protection, and fuel

**tao~** crashworthiness . Powe:-plant fire protection putc; heavy

**eml'h~};it~** on tilt! isolation of ignition sources since the power source ar0as in"•)h·r.· h"t <:11c·i•1C' parts and c:ornponents that .:ire convert

**in~** fuel e nergy Lo us..- tul wori<. 1\t \ i-lt : t fires are locRlized by firewalls which isoL1te them from atij.H:er.t bll'l ·<!.,: are<1s . Lines and components contAining combustible fluid!:i

**H~ r~o:']**  **l•in::!** t ·- ·- fire-resistant materials to protect their contents from fire LnvoJ

**v<.mc•~L .**  Potential l eakage areas are shrouded and drained to

**ar ea~**  which

**~re tr~r**  "f ignition sources . Fuel supplied from the fuel tanks •nay hL· isol..ltl.!d fro•:t !"•:•' power source areas by means of shutoff valves in the

**~vl:!nt** o)f enr,jrH .'

**fire:~.** ·- re detection and

**~xtinguishing** systems dre used to control fires whJ..-.11

**n•-'~Y** sL HL h high fire potential areas . All of these cap<Jbilities •nLISt b•' rlcmonl-L rdU··d according to Federal Air Reeulations prior to eertificatiOP hy tlte FAA.In the multicomponent fuel system, each component receives fire protection consideration to achieve a high level of safety for the overall system. Spaces adjacent to fuel tanks incorporate drains protected by flame arrestors and are air purged to prevent the buildup of combustible mixtures. Component temperatures in fuel tanks are maintained at a low level and electrical parts are made explosion proof. In the event of a wheels-up landing, special design measures are taken to protect the fuel system components from damage which may release fuel. Components and fuel lines are located where they are protected by the basic aircraft structure. Where the relative motion of the aircraft structure in survivable crashes could cause fuel lines to part within the fuselage area, fuel lines capable of stretching as much as 50% of their installed length, are employed to absorb impact and relative motion without leaking . The capability of exhibiting a reasonable degree of deformation and stretching without leakage must be demonstrated during certification. Fuel shutoff valves, which are provided in the fuel lines to each engine and auxiliary power unit (APU), are often duplicated for increased reliability in the isolation of fuel from potential ignition sources . These valves are located at the fuel tank boundaries so that they are not affected by line damage. Open flow fuel tank vents are provided for each tank to maintain the tank vapor space at or near outside ambient pressure for all conditions of flight. The utilization of unpressurized tanks in commercial jet aircraft eliminates the potential of pressurization component failures which can subject the tanks to excessive burst and collapsing pressures in the event of failures during ascent or descent. Flame arrestors or other means are provided in most transport category aircraft to preclude external fires from entering the vent line and igniting vapors within the fuel tank. In the wing fuel tank areas, such hardware as landing gear, wing flaps, and engines are designed to fail in a break- away manner without compromising the wing structural integrity to maximize fuel tank crashworthiness. Fuel tanks within the fuselage receive special attention in this regard. While they are designed to withstand emergency landing loads, standard design practice dictates that they have greater than the minimum required strength. A heavy outer shell is provided in addition to the basic aircraft structure and an innerbag to contain the fuel . Break-away, self-sealing couplings, or stretchable hoses are used to minimize fuel spillage in the event the tank is displaced from the connecting fuel lines by impact loads in survivable crashes. By adhering to these design practices and incorporating new practices only after their worth has been proven by extensive testing , the industry has provided the traveling public a continuously decreasing rate of accidents involving fuel fires over the years.



### 47Operational Experience Before evaluating potential i mprove:ilents to fuel system desi,5n, it is appropriate to look at the accident record to define, if possible, the effectiveness of proposed design changes in

**r~ctucing** fatalities due to postcrash fuel fires. A summary of the

**accidenL~** involving post-crash fuel tank explosions for the
**worldwid~ turbine-~owered**  aircraft i s shown in Figure 3 . Note that these accidents include foreign carriers os well as two accidents for which there

**wer~** no fatRlities.

**Th~** tank explosion accidents listed on Figure 3 . are divided into two categories, those \vhlch involved Minor damage so that the fuel tanks were initially undamaged and those accidents which resulted in massive impact damage

**causi~g** tank rupture and subsequent massive ground fires . ln the first category of accidents, two

**involv d**  ground fires which propagated through the v-:nt systen, and two involvF::d failure to stop fuel tlow through a ruptured engine feed line . It is believed that the tank explosions could have been prevented or substantially d.dayed tor Lhese four c<-1ses by design changes which have since been developed . Propagation of fire through the fuel vent cRn be

**d~lay ed**  to permit passenger evacuation by the use of vent flamt! arrestors which have been developed for that purpose. Vent flame arrestors and suppressurs are
**offer~d** as standard or optional equipmenL on all large U . S. transports in currt:::nt production. Design changes in the fuel shutoff systems have been made to provide greater assurance of fuel cut<>ff under l:!rncrgency conditions . In the 707 case ,

**t" ~**  fuel fire, fed from the ruptured fuel line, continued to burn bec<'iuc.;e of failure to activate the spar fuel shutoff valve by pulling the fi re shutoff

**handl~ .**  The throttle had previously been rt!tiirded to the

**ertgi.n~:: off**  position . These airplanes now incorporate actuation of the spar (u('l shutoff valve by a fuel shutoff lever on the throttle quadrant as well AR on the fi.re handle , thus providing increased assurance of shuLoff

**valv ~**  actuatlon . Returning to Fig . 

### 3, the DC-8 accident at Anchorage involving fuselage breakup and ruptured fuel tanks occurred while overrunning the runway during an aborted takeoff. The fire started shortly before the airplane came to a stop . **Sometim~** thereafter two or more large explosions

**occurr~d .**  l!ost of the passengers and crew (182) evacuated the airplane. However, 46 passencers and one stewardess were unable to escape . Presumably if the
**ex~losions** (assumed to be fuel tank explosions) had not occurred , these 47 people could have also evacuated . It is possible that a fuel tank vent fire protection system or inerting system mieht have reduced the fatalities from this accident by delaying or preventing the explosions . A review of the remaining accident briefs does not indicate that any fuel tank anti-explosion system would have effectively reduced the fatalities in the remainder of the accidents which involved major airplane damage, large quantities of tuel spillage and subsequent fuel tank explosions . Design Alternatives The various design alternatives which

**l~ve** been considered tor potential improvement of the post- crash hazard including fuel tank inerting , quenching, suppression, crash-resistant fuel tanks, anti-misting fuels, and alternate fuels are discussed in the following paragraphs . lt should be noted that an evaluation of these alternatives inherently requires the consideration of their effect on the total airplane design and operation and is not limited to only post- crash considerations. 

### 48Ground Fire-M inor

Impact Damage Massive Ground Fire Wing Tank

Breakup Severe Body Damage World-Wide Turbine Powered Fleet Fuel Potential Reduced Fatalities Hull l oss or Hull Damage Survivors Fatahtoes 

### ~ Vent Improved Fuel Tank Arrester or Fuel Explosion (All Causes) Suppressor Cutoff Protection Year


### ~ Systems Model

**~**

**Rom~** oj 707 1964 48 25 y JP·4D X _X lnn<l<>n 707 1968 5 121 y Kero X X X Sll'lgapore I CMT 1964 0 68 y ) X X Stockton DC 8 1969 0 5 y ) X X X AnchOiage DC 8 1970 47 182 y Kero ) ? Monrovl8 DC 8 1967 51 39 y ) CII'ICiflnatr 880 1967 70 12 y Kero C1nC1nnat• 727 1965 58 4 y Kero St Thomas 727 1970 2 53 y Kero Pago Pago 707 1974 97 4 y Kero Na•obr 747 1974 59 97 y Kero TPnArlfP 747 1 1977 335 61 y Kero New Hope DC 9 1977 61 23 y Kero Wnghtstown l·382 1970 J 0 y Kero New Haven CV-580 1971 28 3 y Kero



## FIGURE 3 TAN K EXPLOSION ACCIDENT ASSESSMENT (POST CRASH FIRES) 49 l ow Probability

of Any System Benefit

7 X X X X X X X X X XFuel Tank Inerting Fires within the fuel tank can be prevented if the oxygen concentration in the vapor space above the fuel is maintained below combustible limits by displacing part of the oxygen with an inert gas. Nitrogen is the most logical inertant. Nitrogen extraction from the air requires a complex separation system if the nitrogen is extracted in flight , or a costly and complex distribution/ handling system if the nitrogen is obtained by a ground operation and then carried onboard as a cryogenic liquid. The tank system, which is pressurized above outside ambient to preclude air frow entering the tank, must accommodate vent relief valves and back up relief valves, pressure regulators , distribution lines, and a fuel "scrubbing" system. The latter is needed to remove the oxygen dissolved in the added fuel which would otherwise outgas oxygen during climb. The reliable functioning of these additional components must be assured if 

### a decrease in overall system safety is to be avoided. In the post-crash situation, a fuel tank inerting system could provide limited benefits depending upon the severity of the crash. In a massive wing breakup, little or no benefit would be available . In a minor wing breakup or no damage situation, the inerting system could provide some benefit . In either case, the system benefit would be reduced considerably if the source of agent were lost during the crash. In the case where little or no damage occurs to a particular tank, there has been considerable experimentation conducted to deter111ine whether or not inerting will protect against an explosion from an under-wing fire. These tests by NAFEC (Reference 14) showed that it is possible for a very**inte~se** under-wing fire applied to an intact, unwetted tank surface to initiate an explosion and that inerting could prevent such an explosion. Even in this most intense underwing fire, the tests showed that no explosion took place until 95 seconds had lapsed . They also showed that in a less severe fire, particularly with modest fuel loads, the tank would self-inert, i.e., a slow oxidation would take place and the tank would become inert . It was concluded that, except for the case where a small tank penetration had occurred, fuel tank inerting did not provide any significant additional protection over existing vent protection systems in a post-crash rire situation. At the 1977 Public Hearing, the Aerospace Industries Association of America projected that the cost of inerting, system acquisition and operation of the worldwide fleet would cost $19 billion through 1996, and would result in an additional 1 . 3 billion gallons of fuel usage over that period of time. Reference 13 presents a recent update of this evaluation which indicates the cost for a 20-year period has increased to $24 billion even though the system weight was decreased significantly from the original study (3460 lb to 1743 lbs for the 747 airplane, based on inputs from Parker-Hannifin Corporation) . This lighter weight system is problematical in that it eliminates the second 

### LNz storage tank system and therefore does not provide a fail safe operational system and would not meet the airlines' dispatch criteria. The projected cost increase mainly reflects an increase in fuel price (774/gal assumed vs 384) and inflation. Current estimates of jet fuel costs are far in excess of $1.00 per gallon, further escalating the cost of the inerting system. It should be noted that development and installation of certifiable , fail-safe operational systems for commercial aircraft requires at least S-6 year time span.



### 50The concept of onboard inert gas generation (IGG) offers potential reduction of cost dae to the elimination of the formidable logistic costs associated

**wit~** ground- produced LNz . The self-contained onboard generation of Nz would provide an operational inerting system worldwide , thus freeing the

**~irplane** fr0m dependence on LNz ground support equipment . The IGG system would use much of the component technology which has been developed for the LNz systems . Additional research and development would be needed in the area of onboard generation technology and systems application before it could be considered for comcercial application (Ref. 15). Fire Quenching 

### An alternative to fuel tank inertine is the installation of reticulated polyurethane foam or expanded metal foil i.n the fuel tanks . This passive system, depending on the porosity of the foam or foil, works by either flame arrestment and/or an energy absorption mechanism which

**pr~vents** an excessive over-pressure or explosion from developine . \.fhile an internal tank firt! is possible, the fire does not cause an explosion, and eventually **self-exling•tisl~e~** from

**l~ck** of oxygen. \fuile some degree of flame propagation is to be inherently expected, the reaction is of the low order, flash fi re variety . Foam by itself or in conjunction with flexible bladders has been applied t6 military aircraft over the last 

### 13 years for tank protection against lightning strikes, gun

**fir~,** and resulting explosions . Experience in combat situations is

**report~d** to be good. However, a translation of this military need to the commercial theater presents difficulties . Due to its susceptability to hydrolysis , earlier foams in some cases experienced degradation when exposed to extremes in humidity and high temperature environments. Some military aircraft have utilized the same original foam for over 

### 13 years. Development has continued and newer foams

**~re** not susceptible to hydrolytic degradation . t.1ater accumulation in the foam at the tank bottom provides a

**perf~ct** location for microbacteria! growth and subsequent tank corrosion in wet wing configurations . Foam removal for periodic structural inspection may prohibitively increase maintenance cost. System weight , weight of retained fuel from wetting and loss of fuel capacity displaced by the foam would present severe operating penalties on commercial aircraft. For a 

### B-747 , the combined weight penalty (foam and fuel wetting) is estimated at 

### 14,000 lbs . This penalty assumes a 

### 40%voided volume which is probably optimistic for the large size tanks . Lost fuel capacity varies from 

### 0. 75% to 

### 2. 0% , depending on the type of foam . The military services have temporarily removed foam in some of the 

### C-130 air planes for some of the above reasons although they are currently in the process of installing the new improved hydrolytically stable foams in the 

### C - 130 fleet . Reticulated foam is being utilized in the majority of new combat aircraft. In an accident situation , foam could provide protection in a "no or minor wing damage situation. Little is known about its performance under external fire conditions. 

### 51Although tesring has not been performed, it is assumed that in massive wing

**hrr.~~** up, foam would not help since flammable fuel mists would be formed and struct11ral damage would permit flame propagation around the foam and negate its effectiveness with respect to the damaged tanks. However, explosions in foam containing areas would be prevented. Foams are categorized as potentially useful only in limited circumstances and they would

**i~pose** a performance penalty and maintenance burden on the operators . Much of the preceding discussion applies to an expanded aluminum foil mesh and will not be repeated . However, there are some significant differences which are discussed below. Because of the higher melting point 

### (1100° F) of foil, its performance under external fire conditions has been proven to be excellent . It is also hydrolytically stable , and when installed, does not encourage electrostatic discharge during fuel operations . In small transports problems associated with installation and removal due to its semi-rigid and non-collapsible characteristics can likely be overcome with proper engineering; however in large transports , aluminum foil mesh may be impractical because of the additional weighr involved and possible need to redesign existing fuel systems . The hasic concept of this system is one in which the flame of an incipient

**explosio~** js

**sens d**  by a detector (IR or UV) which triggers the discharge of a fire extingnsing agent to extinguish the fire before a hazardous overpressure c..:1o develop . Evpansi.on of the c:•trrently applied surge tank flame suppression system to a

**f••ll-~cPle tAn~**  suppression system increases the system complexity by an order of magniturle or more . 

### A typical aircraft system will involve two to eight or nine tanks , each of which will have a large number of bays. Since each bay

**ul~ r~q11irP**  **nn ~**  nr more flame sensors , a typical system could have 

### 50 or more

**~-' C"**  **"' 0rs,**  **~nrl se**  **er e~**  **l** discharge bottles and distribution plumbing . This presents

**~** PYtrPmP.ly difficult system to install and maintain. The sensitivity of the

**det ~tors**  **~akes** the probability of inadvertent firing of the system likely during routine system maintenance or tank entry . The application of explosion

**S"ppres~ion** to

**co~mercial** transport fuel tanks has been studied on numerous

**A~ caslo~~**  **.** In Pll cPses, the complexity of the installation prompted by the """lP.ro11s

**ctr.tP.ctnr~** and suppressors overrode any potential value except in

**~ilitpry P)**  **r~raft.** f.ven recent state of the art improvements which would si.2nific<>ntly reduce the number of detectors has not shifted the balance in f<>vor of

**in~tallatio~ .**  Retrofit of the system to existing aircraft in

**Prlrlitio~** to the maintenance of the system after the one per aircraft per year

**actuatin~** that presently occurs, would be prohibitive from an operator's

**~tPn~point.** It iA therefore concluded that explosion suppression applied to the fuel

**ta~~** is not applicable for protection of commercial transports during

**cra~h** conditions.


### 52

# ) The above systems were evaluated

**i~** terus of weight, cost , maintenance, reliability, retrofit capability, and effectiveness . The results of this evaluation are shown

**i~** Figure 4. In every category the incorporation of a

**v~nt** line flame arrestor is rated as better than, or equivalent to, the h.Ore complex

**syst~ns** currently under discussion . Of tne more complex systems, only the inerting system appears to offer some improvement in the post- crash fire em•ironment. Again referring to Figure 3, of the 15 accidents involving post-c rash explosions, 1nerting hcd the potential of reducing fatalities or hull damage in five cases. In four of these five cases , it is believed that the relatively simple approach of vent flame arrestors or suppressors Dr improved fuel cutoff would have been as effective as the inerting system. These simple and reliable systems are presently installed in most commercial transports . They are typical of the tried and proven fire protection designs which the aircraft industry has ?Ursued throughout its history . Since 1962, this policy in jet transport

**desi~n** has resulted

**i~** a reduction

**i~** accidents

**i~volving** fuel vapor **explosi~ns** fro1J 

### 1. 4 to **B?proxi~ateli** 

### 0. 1 per
**~illion** departures (Figure 5) .

**Fro ~**  the above survey of existing and proposed methorls to elimi"late fi res inside jet transport fuel

**~anks,** the

**follo~ing** conclusions

**~ere** arrived at: o An analy&is of uccident hi.Hory i:1dicates that existing fuel

**;;yste::~** nrc protection oechods are as e ffec tive dS **quenchi~g a~d**  suppression

**syst~ ms**  and supply most of tne protection offered by

**i~erti,g** in

**~urvivable accide~t~**  where minor

**win~** tank daod3e occurs . o Although quenching, suppression , and inerting

**~ys**tefTls r:JdY

**~duc..:** the prvbability of explol>ions

**~here** intense externdl .5round

**fir~s** i:npact near empty but intact

**~ing** :anks, the incredsed conplexity oi these

**syste~s** can compromise the i.nflight safety of the airplane in comoer.:ial applications . o Quenching, suppressio,. , and i,erting

**syste~s repr~sent**  lar6e

**econo~ic,** operational, and maintenance penalties . Crash- Resistant Fuel Tanks The term "cr.•sh- resistdnt" fuel tank is

**~ener lly**  associ-ated 1,·ith fuel tanks that are capable of remaining reasonably intact during a crash event , thereby eliminating or minimizing fuel spillaee and the corresponding post- crash fire threat to surviving passengers . If achieved, this concept can eliminate nost destructive external fires and complement the simple measures discussed in the previous section. The highly visible success of crash-resistant fuel systems installed in

**Ar~y** helicopters makes direct application of this technology to jet transport aircraft tenpting. However , the

**obvi~us** differences in aircraft characteristics, crash scenarios, and accident experience may dictate another course of action.Concept Weight Liquid N 2 Moderate Onboard N 2 Moderate Generation Foam High Foil High Tank Suppresion Moderate System Vent Flame Low Arrestor Summary Evaluation of Concepts

Cost Maintenance Very High Moderate High Moderate - High
Not Known High Not Known High Moderate High Low Low ------ F,igure, 4: Elimination of 54 Reliability Satisfactory in Military Service Not Evaluated Good in Military Service Not Evaluated Not Evaluated Good Retrofit Capability Extremely Difficult Extremely Difficult Extremely Difficult Not Possible Extremely Difficult Yes

I

s Inside Fuel Tanks Effectiveness Good if Tank Not Initially Damaged Good if Tank Not Initially Damaged Good for Intact Tanks Good for Intact Tanks Not Evaluated Good if Tank Not Initially DamagedACC IDENTS INVOLVING FUEL VAPOR EXPLOSIONS PER M ILLION DEPARTURES 1.4 1 .2 1 .0 0.8

0.4 0.2 0 1 0 

### I 1958 60 

# •

0 0 1 

### I 62 

# • • 

# • TREND 

# • • NOTES:



# • 1 ) APPLIES TO FREE WOR LD TURBOJET FLEET 2)EXCLUDESSABOTAGE

AND M ILITARY ACT ION 3) INCLUDES INFLIGHT

AND GROUND CASES



# •
NUMBER OF ACCIDENTS 2 2 0 3 1 1 3 0 0 0 2 0 1 1 0 

### I I I I I 

# .I 64 66 68 70 72 74 76 78 YEAR 

# FIGURE 5. TANK EXPLOSION ACCIDENT RATE WORLD WIDE AIR CARRIERS - ALL OPERATORS
55lhe 0bvious

**1liff~rence** in fuel

**syst~m** and a i r craft design and the crash

**SCLn~r:** j

**~ f~·**  t i,.._r r:f'mp) ic"lted by the definition of "impact survivable . " TlH'

**\r·~! ~i**  i-2 its c!· 1 < • .•Ji,,t_i<)n. of whethe r or not an clceident is impact surv"ivablc ?n 111 dS.>t.:::.:,·:h .. '1L 'Jf" the inerti-'1 forces tr-:J.nsrnitted to the occupant thrnngh hie; 

### r, ,, : and

**rt~l r-::~in.t**  system and on whether or not the cAbi.1 struct•1re t.oll3p&ed ,.,il't· the o ... -, 11 J c nt ' s envelope . On the other ha:1d, the FAA considers d c:rds\1 !:>urvi·,rable if one occupant survives the impact event. 8ecan;;e ,)( tht

**d:~.:** t' T t ransport

**<~ircrd[t** And tht- correspondingly high energy ahsorbine

**ror~r:t** i :.1 , ,, is concei'J3ble that <;;oane occupants

**~..ill** :S11rvive very high

**cr~sh** imrdc t. vel<"t.i' i ':!s . On the father hand , because of the reL'Itively srn-3.1 1 :::i?.• ot ··· \ heli

**opter~ ,**  all occupants and systems <H.: exposed to approximatr>ly til' .. 4

**~1.d:c-:1 ~;..n•;i**  **ront" ~l"'t**  facilit"iting d n:lati.vely cleau definiti•)n ,,f 10

**~** ..
**,r~ ·**  

## • s.un·ivat>le crash . Tran.;port aircraft fuel t:.tnl<s fall oroacHy into two categories - inte[;r4l ·· 1.•..., tanl-..s and fuselage tanks. The application of crashworthy bladder tnnks tn integrol •

**.,rin~** tanks cannot be accompli sheri

**ithout** .-t complete redesign of

**th~** wint;

**b~caust:::** of its multi-cellul.'lr construction . **Furthentor~ ,**  it cAnnot 

## :.1-

**~~;** 1 with certai.'lty that c rash-rt!sist.-tnt [uel tanks

**~<IUulrl** pruviJe fire

**prntt~ t,**  '" ·'

**crd~h scen~rios**  that include wins

**sepdr~tion .**  feder al

**rt ·,s**  **ation~ ~q**  **u:re** that dar.1a.5e to the

**nir )lan·~**  a:Jclia l;:;w!: ,...

**~·** tr ··,
,tnri "..; tc.1keoff inri l3ndlng shall not cauS\:! :;;pillAg.'.! of

**~no 11**  **gh** fnel t•• c

**,, ~!'**  **it** ' a fire h'l! 'Hd . The fuel tank and landi"lg gear support stra1ct•Jre i.: rl, :1 n,..; :

**hi.;'~· r**  **~trt_ngth** thAn the gear to prevent fuel t::tnk rupturt2 duP. t•' -111 ·1• .:.: l· 

### v •' lAtllii.ng gcil.r

**OVt!rl~)"id ,**  This

**desi~n** requirement i.s fur ther t!xt::ended t. · i .• I ,-'

... tr·•ctur,.l] .'>tt"lchr.H!nt:-. to the \oling fuel t<Jnk which •:tight he nvc:rl•)'l·i '·l .;.,:·!.••

**whc~ls-uj·** or partial wheels- up landing . Flap hi"lges and

**l~ngint' mttm~L-;,**  t .r· examplo:: , .are desirined to fail without ruptur ing the t::tnk . 'Befr>r•-;: dic:.r•l&<;ing the application of crash- resist-lnt fuel tanks i 1 th· t

**J~··l,** • Arta, somcthi1g should be said abr>ut current fuselage design pl·.:tr;tir.·o:; .

**l•t ~!**  !•:· fuel "lnJ he carried in the center wing structnrc or 1.:1 "'

**pr.:!~<;uri** 2 1-•:

**tr ·~**  1 as a -:argo co:npartment. Fuel tanks in the

**c~nter** wing struct11re

**.Jr ~**  •k:·it-'1•"' 1 :

**l'lo::t t**  the "g" loads presc r ibed for e10ergency landings . In "'irplanes having :uel tanks located 1o1ithin the pressuriz:t::d at -1 , **ty~.-i.** -1 1 ly the cargo compartment, particular dtt ention is paid t o minimizi.n{ LiH r t ...,k · r fuel spillage . An example of one such design is sho"m on Fi,:>,Hr.- ; h , 1 · ·•

**L~n~** composed of an aluminum honeycomb out er shell with bladder

**cell~** insi1.;: . LIH t"inl<: is supported frotn the floor beams in such a manner -'iS 1n prrr I 11i·· f-., ...•:: structure deflections f rom loading the tank . Clear.-itlces from adjcll't 11 t ·lt•t• L :r.

**~** p roviJed nround the tank . The fuel "'nr! vent lines that connect the tank:> tu the main laa·l

**..;y·~te•** incnrpor.Ht!

**~r-dnr1hl~** ::tnd vented shrouds . These

**line~** .,rl':! either .lc· i ,,.,.. • • "hr... "lk -tw;:Jy" lrOlll t he n••xiliarj tank vr sufficiE-nt

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**.-~cc•u<r,J0dat:** tAnk nove1Jent without C"iusi'l£ fuel :::pi ll-'lt;t> . **J..J.o~ts** th,JI. 11 -. requ1red to str·Hch are subjected to whilt is normally ro.:ferrt·.l Ln

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# j Wing Center Section

Tank Forward Downward Upward Sideward

Additional tank protection obtained by keeping fuel heads within design limits during 1 radian/sec. roll and by using nacelle strut. Landing gear and trailing edge flaps attachments for controlled breakaway. 

### FiguTB 7: Fuel TankLoadFactoTs

Tank No.2 cargo door 

## <( 6 

## 9.0g 4.5g 

## 2.0g 1.5g

8.0 min 

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# • Rear view 15.30--.J at Sta. 9500 

### FiguTB 

### 6: CaTgo CompaTtmsnt Tank InstallationDuring the design of the tank installation, prior accident history is reviewed to ensure that likely crash scenarios are considered and that possible leakage of fuel is minimized. For example, accidents or incidents where the gear has separated are reviewed to insure that the tank will not be hit by a displaced gear. Also, incidents or accidents where the fuselage has been crushed are reviewed to insure that there is adequate clearance between the fuselage and the fuel tank. In addition, incidents or accidents where the fuselage

**ha~** broken fuselage has broken are reviewed to ensure that the auxiliary tank is not located where such breaks typically occur . In summary, it can be said that the fuselage fuel tank design: o Exceeds FAR requirements o Is mor·: rugged than center sectton tanks o Provides considerable

**clear~nce** o Allows tank displacement without fuel line breakage. o Location results in cinimal spillage exposure . Crash-resistant fuel tank (CRT) installations in wing and fuselage areas were evaluated. A summary of the results of this evaluation is shown in Figure 7. As anticipated, the wing installation shows excessively high penalties in almost every category evaluated . On the oLher hand, the fuselage installation results in only low to moderate penalties . One other source of potential fuel spillage is 

### a broken engine fuel supply line when nacelle damage occurs . An existing regulation, FAR 25 . 1189, requires that, "Each tank-to-engine shut- off valve must be located so that the operation of the valve not be affected by powerjJlant or engine mount structural failure . " However, in one incident where 

### a nacelle separation f rom the wing in flight could not be detected by visual means, the crew interpreted the instrument indications as an engine flameout . Since normal shutdown procedures only required that the engine fuel shutoff valve be closed, the tank-to-engine shutoff valve was not actuated. Consequently, excessive fuel spillage occurred after the aircraft came to rest resulting in a fire . Subsequently , the fuel system design was modified to include closure of this valve during normal shutdown. Incorporation of this feature or its equivalent in the fuel system design is shown in Figure 7, to have minimal impact on the airplane design and operation. The results of this brief evaluation indicate that a careful analysis of crash data history to explore modes of failure is essential to determine if improvement of fuel retention during transport airport crashes can be achieved. A research program involving the 3 domestic widebody airframe manufacturers was initiated in January 1980 for the purpose of developing crash scenarios and recommending a future test and analysis effort for the development of improved crashworthiness .



### 58SummaryEvaluationofConceptsConceptWeightVolumeCostReliabilityRetrofitEffectivenessCRTFeasibleNotvsAllModerateLow LowPassivePossibilitiesinFuselageCRTDifficultNotvs.AllHighHighHighPassivePossibilitiesinWingEmergencyLowLowFuelShut-offLowGoodYesGoodFigure7:FuelContainment59From the foregoing , it was concluded: o It is feasible to install crash-resistant fuel cells in fuselage cargo compartments . o lt is not feasible , in most conventional transport aircraft , to install all the wing fuel in crash-resistant fuel cells . o It may be feasible to install some degr ee of crash-resistance including break away fittings at criticAl locations in some

**state of-th~**  **-ar t**  aircraft wings, depending upon specific type

**d~si gn**  **.** o The existing Federal Aviation Regulations allow the use of crash-resistant fuel cells in transport aircraft . o Further definition of criteria should evolve from total aircraft crashworthiness considerations . The research contracts with the three widebody manufacturers should accomplish this objec tive . Anti-Misting Fuels The fundamental consideration in developi ng a crash- safe fuel is to produce

**~** fuel which will not burn in a crash environment and which will not compromise engine performance throughout the :tircraft operating envel ope . Ant"i- misting ker osene (A)OC) is the latest development in the search for such a fuel . An anti-misting additive prevents the fuel from breaking up into a fine, hi5hly combustible mist when subjected to the high shear rate expulsion of fuel from a small tank opening or by air shear breakup of the large fuel masses expelled from damaged t:tnks during crash decelerations . E liminating or preventing the rapid development of a l arge fire around an aircraft involved in an impact survivable

**accid ~n**  **t** where fuel tank rupture occurs will allow more time for passenger and crew evacuation and result in a higher rate of survivability in this type of accident . The anti-misting quality is imparted to the fuel by the addition o( low concentrations of shear-sensitive high molecular weight polymers . The additive currently being evaluated by the 

### FAA is a British-developed polymer known as FM-9 . AMK is in the early stages of its development. The current candidate has already demonstrated its ability to minimize, and in most cases eliminate entirely , the fireball frequently experienced when fuel is released during a crash although many factors are yet to be investigated . A}OC offers a tremendous potential for post-crash fi re hazard reduction. With development, it is expected to have a minimum impact on aircraft operation and maintenance. Major questions yet to be answered include the effects of the additive on static charge generation and relaxation, engine starting and relight characteristic s, heat transfer characteristics, filterability, materials compatability, fuel oxidative stability and storage stability, as well as c.osts. The most important property of AHK, its tendency to form large droplets when sheared, is not a desirable characteristic when the fuel reaches the engine combustor. Consequently , development of a degrader to restore the fuel ignitability just prior to entering the engine combustor, is high on the list of development priorities.Although no specifications for AMK exi sts as yet, the following properties have been established as targets: o Heat content equivalent to current fuels . o Anti-misting quality maintained during handling. o Minimum impact on engine start and relight. o Acceptable pumpability and flowability . o Compatable with existing materials and components . o Achievevable at reasonable cost. In spite of the many questions yet to be answered, the technical community's reaction to AMK is highly favorable at this stage of its development. Its fluidity has been improved significantly without compromising its anti-misting qualities. The development of 

### a suitable degradation process is encouraging. Test programs are continuing in the areas of engine and fuel systems compatibility , air shear and flammability, and rheology definition. In addition, large scale tests are being implemented. If no unacceptable aspects of A}OC develop in the continuing program, it is estimated that it could be introduced for commercial aircraft usage as early as 1984 but at least within 10 years . Alternate Fuels The current effort to develop new sources of crude oil such as synjet derived from coal or shale oil must not overlook their post-crash fuel fire hazard potential. Although the type of hydrocarbons may differ among synjet and petroleum Jet A fuels, these differences will not influence the probability or nature of fire in a crash situation if the fuels are produced to the same specification. The effect of broadened fuel properties and alternate fuels with completely different properties on fuel safety is discussed briefly in the following paragraphs. One alternative fuel being studied has a flash point specification 10° F to 20° F lower than the current commercial Jet A or Jet A-1 specification of 100° F minimum. The incentive for considering such a jet fuel is increased potential availability and more refinery flexibility in meeting other critical jet fuel quality requirements such as freezing point . The Canadian and Russian commercial jet fuel specifications (CAN 2-3 . 23-77 and GOST 10227, respectively) have 33° C (92° F) and 28° C (82° F) minimum flash point requirements. The recent reduction in flash point was adopted by the Canadians because trends showed 

### a reduced growth rate for gasoline and a healthy growth for distillates including jet fuel. Considering ambient temperatures in Canada, laboratory data, and other operational factors, it was concluded that the reduced flash point would have 

### a minimal effect on fire safety (Reference 16). 

### 61Although it is recognized that fuel types currently being studied will have a minor effect on the overall safety of turbine aircraft , it is known that large differences in flash point can influence fire safety . Consequently , decreases in flash point to increase jet fuel availability must be carefully considered before a decision is made. On the basis of laboratory data and its
**r~lationship** to the accident record , a fuel with a flash point of 80- 90° F would be expected to behave more like Jet A (100° F flash point) in crashes and inflight fires according to Reference 3 . Any difference in fire safety compared to Jet A would be expected to occur when the fuel temperature is at or near the flash point. It is recommended that FAA sponsor studies to quantify what effect reduced flash point fuels might have on aircraft fire safety in the U . S. A . Liquid hydrogen and liquid methane are being considered as aircraft fuels . The use of cryogenic

**fu~ls** involves the hazards arising from low temperatures as well as those of combustibles . Studies of safety problems that might arise from airline use of these cryogenic fuels should continue and keep pace with the overall aircraft development studies . Conclusions Any evaluation of systems for reducing the fuel fire hazard in impact survivable accidents must consider the effects of the system in all phases of the aircraft operation: on the ground, in- flight and at landing and takeoff . The tendency to consider the merits of the system in the impact survivable environment only can lead to erroneous conclusions which, if implemented, could be to the detriment of the traveling public . Consequently, the conclusions reached in this section may differ in some

**respects from**  those expected ror

**th~** crash situation only . The primary conclusion reached in evaluating both existing and proposed fire hazard reduction systems in that the use of anti-misting fuels has Lhe greatest potential for improved safety by essentially eliminating the development of fuel fires in a post- crash environment . While much further development work needs to be done to improve the currently promising anti-misting fuels for practical use in fuel systems, the research on such fuels sltould be expedited. The improvements introduced into existing designs in recent years which meet or exceed Federal Aviation Regulations have proven to be effective. The proposed more complex systems do not appear to offer significant additional protections in their present states of development. Furthermore , these more complex systems have an appreciable weight , complexity, and maintainability penalty which will degrade overall airplane performance and safety. Fuel tank inerting may have a potential for future aircraft safety improvements only if its weight and complexity can be significantly reduced through further development .



### 62

### VI R 

### & D CONSIDERATIONS Summary and Perspective Although there have been a recurrent number of in- flight fire incidents, all fatalities attributable to fire in

**.** air carriers have occurred in crash accidents . Therefore, it is imperative that research and development be conducted in the context of a postcrash fire. A postcrash cabin fire scenario is described in this chapter. This scenario has been utilized and analyzed in the FAA C - 133 full-scale fire test facility . The fire scenario was conceived to provide a realistic postcrash fire wherein the ignition and burning of interior materials would become a significant factor affecting the survivability of cabin occupants. Placement of the scenario within the spectrum of actual postcrash accidents will be an important task of the comprehensive FAA/NASA sponsored study by Boeing, Lockheed, and HcDonnel-Douglas of past transport accidents . Aircraft cabin materials fire safety technology has historically been focused on polymeric material development. Most of these materials, which are functional , comfortable, decorative, and economical , will burn under certain conditions . Past research has emphasized modifying these materials or developing alternative materials to reduce (but not necessarily eliminate) burning and the evolution of smoke and toxic gases. We are able to test these materials in the laboratory and provide relative data on burning (e.g., flame spread, heat release rate), and smoke evolution. The problem; however, is to relate such data to behavior in an aircraft fire and to assess its rel?tionship to survivability in a postcrash fire in the design of aircraft. It is simplistic to demand a continual change to materials that burn less readily or give off less smoke or toxic gas. Before there is a requirement for such changes, it should be possible to define, even approximately , the increase in survivability that would accrue. To do so one should be able to predict (analytically or empirically) the course of a fire in a real aircraft containing a mix of materials. The goal is to predict the additional escape time provided by improved materials. The leading organizations engaged in research and testing related to aircraft cabin fire safety are the FAA, NASA, and the three major airframe manufacturers (Boeing, Lockheed, and McDonnel-Douglas). Areas of responsibility between. FAA and NASA are defined in a memorandum of understanding (MOU) Reference 

### 21. Industry efforts have been supported by NASA as part of the past FIREMEN program or by internal funding as part of the IRAD (Independent Research and Development) program. The FAA program is described in detail in a recently published program plan document Reference 

### 21. A 3-year time framework is described for the comprehensive development of test methods and criteria for cabin materials. A longer range 6-year program has been prepared by NASA at JPL which focuses onthe development of a mathematical cabin fi re model. Of a shorter time period than either the FAA or NASA programs is an 18-month program prepared by Boeing to correlate full- scale and laboratory testing, culminating in an interim test methodology for cabin materials . The FAA program plan was endorsed by the SAFER Committee after the program was presented to the committee on

**~larch.** However, the NASA modeling plan and Boeing interim proposal m ust be integrated into the FAA progra1n plan. Prediction of Cabin Naterials and Human Response to Fire Hodeling The ability to analytically or empirically describe a fire and its progress is desirable for designing interior systetns and selecting materials, and relating small and full scale test data to materials performance in an accident . Fire modeling in government and industry is currently in the early stages of development and offers many

**advant~ges** in cost and time savings . A concerted effort should be made to accelerate the empirical correlation of laboratory and full scale tests and to advance analytical modeling development . Analytical modeling i s seen as a long-term eftort in cabin fire safety technology . The SAFER R&D Subgroup expended extensive effort in developing both short term and long term descriptions of modeling needs which are attached in Volume II . Modeling would intelligently predict cabin materials behavior for given fire scenarios and the resulting human survivability envelope, given the establishment of standards for l1uman tolerance limits. Each of these elements is now discussed. Aircraft Cabin Fire Scenario General In response to a SAFE!{ Recommendation, the FAA developed the following typical scenario. A wide body jet transport with a 57 percent passenger load factor crashed on the runway of a major airpor t following an abnormally high descent rate . The accident occurred on a sunny afternoon. This scenario will be refined, and perhaps other scenarios added , following analysis of NTSB accident reports and data relating to actual crash conditions . This activity is currently underway by the three 1.1ajor airframe manufacturers under ten.1s of NASA and FAA contract studies for improving structural integrity. Fire Description During the crash deceleration an integral tank in the right wing was penetrated by debris, spilling fuel which was immediately ignited by frictional sparking. A train of burning fuel was observed behind the decelerating airplane . As the airplane came to rest a large external fuel fire erupted immediately in the vicinity of a fuselage rupture . Except for this opening in the fuselage on the right side , the fuselage was otherwise intact. The size of the opening approximates a rectangle 76 inches high and 42 inches wide . The two forward doors on each side of the fuselage were jammed and passengers and crewmembers - none of whom were immobilized or traumatized - utilized the remaining six doors to evacuate the airplane . During the crash deceleration, the main and nose landing gears were sheared off and the airplane eventually came to rest on itsbelly in a level orientation . All emergency lighting systems operated properly. (Note: Based on past accident analyses , other plausible openings for the entry of fire are inadvertently opened doors or small ruptures beneath the cabin floor line.) Other door openings were not subjected to the pool fire, which involved several thousand gallons of fuel. The pool fire reached heights of approximately 75 feet, extended beneath the belly of the fuselage and completely covered the rupture. The pool fire flames were attached to the fuselage. Only those cabin materials very close to the rupture opening were subjectd to the intense heat and flames generated by the fuel fire . A relatively steady 3 mph wind was blowing in a direction perpendicular to and toward the fuselage. The pool fire was upwind of the fuselage. The radiative heat flux in

**~he** fire may have reached 14 BTU/ft2-sec and at the center of the cabin opposite the rupture the flux would have been at least 1.8 BTU/ft2- sec. There was moderate penetration of flames from the fuel fire primarily in the vicinity of the ceiling next to the opening. Evacuation Description At the first indication of fire at the ruptured fuselage location, those passengers nearby immdiately began moving away from the fire. Surviving passengers and crew utilized one-half of all the exits to evacuate the airplane . Estimates for the evacuation time ranged from 90 seconds to 3 minutes . The shell of the fuselage remained primarily intact during the evacuation although the cabin was eventually gutted. Design Fire Considerations 

### An important feature of an aircraft postcrash cabin fire is the possibility of intense thermal radiation from a large external fuel fire through a fuselage opening. In order to be representative of the large fuel fires characteristic of many aircraft accidents, a design fire should be "optically thick" to produce this intense radiation. The severity of the fire exposure to interior materials increases with the degree of flame penetration. Cabin hazards arising from the fuel fire are dependent on the amount of flame penetration into the cabin. The degree of flame penetration for the design fire must be selected to provide cabin hazard levels well within human survival limits over a prescribed time interval. Human Tolerance Limits Limited information is now available on the limits of human tolerance to heat, smoke, and some toxic gases; however, more work is needed in defining the effects of irritant gases and a definition of human tolerance from a systems point of view. The combined effects of heat, visual disorientation, and the presence of irritating or toxic gases on the behavior of passengers need to be evaluated relative to cabin egress design. Efforts along the line of the FAA Combined Hazard Index (CHI) program are needed. (CHI would account for the combined affects of heat, smoke and toxicity . )


### 65Egress , Lighting, Emergency Communications These items do not fall under the scope of SAFER; however, the design and development of technology must be done within an overall systems approach for evaluating survivability . Volume 11-B contains

**so~e** commentary on Egress lighting and emergency communication factors , even though the Committee did not discuss them in any detail, nor formulate any related recommendations . Fuselage Fire Resistance Whether the fuselage is a wide body type or a standard body type will have a crucial bearing on the development of the fire and its hazards . For example, compared to a standard body jet , a wide body jet is more resistant to burn through by an external fuel fire , furnished with more flame retardant cabin materials , and encompasses a large cabin volume with possibly greater dilution of combustion products . Nodeling In order to intelligently predlet human survivability,

**then~** is a need to relate material laboratory test results with aircraft cabin geometry , a fi re scenario, and human tolerance limits. It is necessary to have analytical or empirical tools to model the fire . There are two aspects to this issue which are complementary and integrated activities. They are: 1 . Short term analytical and empirical methods to correlate full scale, model , and laboratory testing . 2. Long term development of mathematical tools to predict the progress of burning , temperature , and gas species distributions in a defined geometry . These two aspects should not be considered as competitive activities; but rather both part of a continuum of activities from which increasingly valuable modeling tools emerge. Short- Term Plan The base for the development of such a methodology has been laid down with several programs including the FAA contract with McDonnell-Douglas for the "Combined Hazard Index" (CHr), Boeing fire test methodology program started in 1974 and the NASA- JSC contract on fi re test methods which Boeing completed in October 1978 . There are probably others, but these are notable because they developed within two of the three major airframe companies exceptional knowledge pertaining to the problems of material evaluation and fire threat definition . This background combined with the knowledge of airplane construction and parts fabrication provides a currently unique capability to develop a methodology to evaluate the fire performance of materials in a fashion both effective in materials control and practical in application.



### 66At the request of the SAFER R&D Subgroup, the program outlined on Figure 8 was proposed by Boeing to develop this capability in the shortest time possible. The correlation study in the proposal is similar in many respects to the FAA-sponsored CHI contract scheduled for completion in December 1980. Major similarities include the utilization of the OSU chamber for the measurement of rates of emissions of heat , smoke, and toxic gases , and large-scale tests on single materials as part of the test methodology development . Therefore , many of the provisions of the correlation study are contained in the CHI study . It i s recommended that the CHI contractor , McDonnel- Douglas, be requested to make a detailed presentation to a select group of FAA, NASA, and industry on the design, development, validation, and limitations of the CHI test methodology. In light of the degree of success of the CHI methouology , the FAA should request Boeing t o redefine and describe in detail the elements of their empirical correlation study . At that point in time, the FAA should be in a better position, taking into consideration suitable inputs and recommendations by NASA and industry, to consider the revised Boeing proposal. Much of the work required in Phases II-V of the proposed plan has already been started during the previously noted programs . The main ingredients for the success of such a short term program are : (1) a sense of urgency to resolve the material evaluation problem within the state-of-the-art , (2) recognition that in this case only the airframe companies have the test correlation, airplane design, material selection and laboratory test application background to develop the practical solution in a timely fashion , (3) a means of formally requesting and obtaining the participation of the industry in the effort, and (4) timely testing and analysis support by the NASA and FAA-CMli, and effective testing and program administration support by the FAA-TC. Long Term Modeling Plan General The SAFER R&D Subgroup requested that NASA' s Jet Propulsion Laboratory (JPL) develop a comprehensive long-term aircraft fire modeling technology plan. It is included in Volume II . The plan was designed to provide analytical modele which possess well- defined predictive capabilities with particular emphasis on user needs. Furthermore, since analytical methods should be developed in conjuncti on with related experiments , the long-term plan also includes test programs which are necessary to establish an effective and valid predictive technique. Preparation of the plan began in October 1979 and inputs were made by the air frame manufacturers, Federal Aviation Administration, National Bureau of Standards and the National Aeronautics and Space Administration. Phase I, Definition of Fire Modeling Technology Requirements, of the 6-phase plan has been substantially completed by NASA JPL and the phase 1

**re~~lts** are also included in Volume II . The overall objective of thi s Fire Modeling Technology Plan is to develop analytical and experimental methods for use in aircraft design and testing to r educe the post-crash fire hazard. Specific objectives developed in response to previously discussed needs are:



### 67FIGURE 8 PROJECT WORK TIME <DOES NOT INCLUDE CONTRACT NEGOTIATIO N S, ETC . >

l.lp:.S.. **~:.S.a ~:.s..**  l2..MQ.:,S , **JS.J1Q:~ l8..1~**  **:~**

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FIRE SCENARIO SINGLE MATERIALS i

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: l

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**~** t

II PLAN OSU OSU DEVELOPMENT FOR I l DEVELOP METHODOLOGY FOR I

O[V ELO PHENT AIRCRAFT MAT ERIALS MATERIAL EVALUATION

ll PLAN TOXIC THREAT DEVELOP POSITION FOR DEFINE H ETHOO TO ANALYTICALLY JASSESSMEN T TOXICITY SIGNIFICANCE MEASURE TO XICA NT RELEASE

i l PLAN FOR FLASH DEVELOP POS I TION ON NATURE AND DEFINE METHOD TO MEASURE **~**

POTENTIAL HEAS. SIG N IFICANCE OF FlASH POTENTIAL "FLASH" POTENT IA L

. !

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I J-101 . Determine the capabilities of existing modeling methodologies relative to user needs; and accelerate activities to improve these methodologies with regard to the stated needs . 2. Develop a detailed , analytical fire dynamics model that will describe the post-crash scenario; and develop other new modeling methodologies as required. 3. Determine the capabilities of existing small- and large- scale test methods for model application. 4. Develop and refine appropriate test methodologies which can be used with models to give well defined predictive capabilities . 5. Develop hazard evaluation modeling methodologies . For a number of years, the FAA has sponsored the development of a mathematical cabin fire model at the University of Dayton Research Institute (UDRI). Of necessity , development of the UDRI model must fit within the 3- year time framework of the FAA program plan. The FAA has identified "weak" portions of the UDRI model which require improvement. While SAFER has endorsed a long- range mathematical modeling endeavor , it is recommended that the long-range program be structured to provide "early'' products (subroutines) to upgrade the UDRI model. These "early" products include theoretical modeling of burning processes of aircraft mmaterials and of flame spread under superimposed radiation and ventilation, including scale and ventilation effects . During the entire Fire Modeling Technology program there should be close coupling and interactions between the activities associated with modeling , hazard evaluation, experimental/testing and existing aircraft design and design methods. The establishment of a government-industry Technical Working Group is intended to assist in furthering these interactions . Finally, the long-term plan would be complimentary to the short-range plan for the development of empirical correlation methods . Testing General Testing methodology was singled out as a technology requirement because of the lack of reliable predictive methods which are demonstrated to be correlated with performance in an accident. Near term focus should be on well instrumented full scale tests (e.g . , FAA's 

### C -133 tests and NASA' s 

### B-737 tests) to provide quantitative design requirements , contribu- tion of cabin interior materials to the post-crash fire hazard, and to realistically evaluate current and new materials systems. Mockup tests, similar to the concepts used in the McDonnell-Douglas Cabin Fire Simulator, should be employed to provide similar evaluations in the future at lower cost. Also, further development is needed to develop correlation between lab tests and full scale/accident performance. The SAFER R&D subgroup made the following findings and recommendations.Findings. 1. Full- scale and mockup testing are required because there is a lack of reliable predictive method$ . 2. Laboratory and full- scale test

**corr~lation** with accident performance needs extensive development. 3 . Correlation of laboratory tests with full-scale tests requires further effort. 4. The Ohio State University (OSU) Heat Release calorimeter methodology appears to provide the most promise for long-term laboratory test application. The OSU shows promise of providing correlation with additional work. Laboratory methods for weasuring toxic gases do not currently correlate with full-scale test results and require further work . Part of this effor should be conducted as an ASTM activity after the tests are proven to be valid indicators for at least ranking the various materials regarding their relative hazards. Recommendations . 1. Continue full- scale tests with the C-133 at the FAA Technical Center and B-737 at NASA, Houston test articles . These tests should utilize an agreed upon fire scenario and be completed in approximately 2 years . Additionally, the test program should include advanced material tests after testing of contemporary materials is completed. (Note: It is recommended that for technology development purposes, a 5-minute evacuation time be considered to represent the majority of cases.) 2. Mockup test configurations should be defined and the validity verified. This type of test is less expensive to conduct and provides more rapid turn- around times . 3. Further effort should be expended to correlate laboratory tests with full-scale and mockup tests. 4 . Expedite the development of the OSU Chamber Calorimeter and evaluate its use as a regulatory tool (within 3 years) . Establishment of an industry/government test

**develo~ment** advisory committee is essential . Coordination of R&D Between Domestic and International Groups 

### An important lesson learned during the SAFER proceedings is the strong desire by industry to establish a government-industry forum for exchanging technical information, coordinating research and technology planning and the development of materials and safety fuel standards . The R&D subgroup after exploring several alternatives , recommended that such activities be pursued by the ASTM Committee F - 7, Aerospace Industry Methods (Cabin Interior Materials) and ASTH Committee D-2, Petroleum Products and Lubricants (Modified Fuels) .

70

### The FAA in its response to the interim SAFER Recommendations briefed SAFER on April 5 on two draft parallel research and development plans designed to improve human survivability and reduce hull losses resulting from fires in otherwise crash survivable accidents . Both plans will develop the technical data base by 1984 which when coupled with other rationale , i.e ., economic analyses, will support FAA regulatory proposals. The Cabin Fire Safety Plan will evaluate current and improved cabin interior materials , determine means to retard the progress of cabin fires, improve evacuation systems, and improve crash-fire-rescue
**effectiven~ss .**  

### The Anti-Misting Kerosene (AMK) Plan will determine AMK feasibility, develop promising AMK additives, de1nonstrate

**~~** 

### effectiveness in large and full scale tests, and develop recommendations for the use of AMK in civil aviation operations. The draft program plans have subsequently been developed to a final form. The SAFER Committee has reviewed the Cabin Fire Safety, FAA-ED-18-7, and AntiMisting Kerosene, FAA-ED-18-4, Program Plans and recommends that the FAA vigorously pursue them in parallel until such data are available to determine if continued parallel research is required. Complementary to the SAFE R activity, the FAA, NTSB, and the aviation community are expanding the scope of accident investigations to fully develop the performance of cabin interior materials , fuels, and aircraft seats and airframe structures. In certain of these investigations experts from NASA will oe involved. At the time this report was prepared, NASA was developing long-term plans for · fireworthiness materials, modeling and safety fuels research. The planning includes specific research at each NASA Center (Ames, JPL, Johnson, and Lewis) based on technical expertise and facilities and uses draft FAA - TC Engineering and Development Program Plans for Cabin Fire Safety and Anti-Misting Kerosene in the 1981-1984 time frame as inputs for short-term requirements. The joint research is conducted under terms of a formal NASA-FAA agreement established during the Firemen Program. NASA and FAA are also establishing the details of coordinated research for improving transport aircraft structural integrity that would enhance crash survivability. International research coordination and cooperation is also required because of the potential for implementing more stringent airworthiness requirements for existing and future U.S. manufactured aircraft and the extent of the international accident statistics . The current trend in Europe is for adopting common airworthiness requirements in the form of Joint Airworthness Requirements (JARs) which are heavily influenced by the FAA airworthiness regulations. The FAA and UK-CAA meet annually to review operations and research activities and perhaps this mechanism would serve as a means to enhance international coordination of research and a more extensive, unified approach to fire safety improvement world-wide .



### 71Anti- Misting Kerosene

**(A}~)** Research A}OC has been previously discussed under Fuel System Fire Hazards and at this point, A}OC R&D and economics analysis requirements are discussed . NASA and FAA have been conducting AMK research using a British industry developed proprietary additive. Cooperative research between the FAA, NASA and the UK-CAA is conducted under terms of a government- to- government agreement. The AHK additive in jet fuel reduces the possibility of fuel pool fires in crash survival accidents because of the inhibition of the fine fuel mist which typically allows fire-propagation from an ignition source to the fuel pool. SAFER was briefed on the status of US/UK AMK research and the FAA' s Program Plan for continued research assuming sufficient rationale will be developed by October- November 1980 for further research . SAFER concurs with the need for further research to include alternate fuel additives to jet fuel and expansion to other fuels that could appear in the market place and where warranted for other aircraft classes, e . g ., commuters, corporate, general aviation . Sufficient concurrent research in both research areas , i.e . , fireworthy materials
**and~~** will be required to determine their relative effectiveness anci the costs and benefits to the various potential users . The FAA is faced with multiple research tasks , limited available research funds and pressures to resolve other high priority safety issues . Therefore, it would be reasonable to expect more sophisticated and timely FAA management techniques to determine the extent to which multiple solutions to safety problems should be pursued .



### 72

### VII CREW PROTECTION AND ?ASSENGER EVACUATION The scope and expertise of the SAFE R Advisory Committee was limited to transport category aircraft and the design aspects of such aircraft as they relate to fire and explosion reduction. B ecause of the relatively short time involved for the Committee's efforts , attention was focused primarily on impact survivable accidents where control of fire and explosions would enhance occupant survival. Certain of the discussi ons of the Committee were beyond this scope; however, since they did affect occupant survivability they are reflected here so they can be kept in view for regulatory activities outside SAFER. (See Volume Il-B for additional items in this category.) Protection and evacuation of aircraft occupants are the critical elements of safety in a postcrash fire environment. The FAA should work to attain these goals by (1) ensuring that effective escape m echanisms are built into the airframe and are present in the cabin i nterior, (2)

**en~u ri**  **ng** that the flight and cabin crewmembers are properly trained, protected, and able to direct and assist evacuation, and (3) improving passenger education efforts. In addition, the Committee sugges ts

**~alu io**  **n** of several measures to reduce the hazards present during an inflight fire. It should be noted that these issues, since they were beyond the scope and expertise of SAFER, w ere not discussed or evaluated by SAFER or its technical groups. Countermeasures for lnflight Fire Injury A. Lower Lobe Galley and Lavatory fi re Detectors Continuing attention to smoke/tire detectors in critical areas such as lower lobe galleys and lavatories is needed . Consideration should be given to being independently powered with a "press to test" feature for operability and activation indicated by an aural alarm and lights visible to flight attendants . In similar systems now used, very few false alarms have been reported, whil e several fires have been detected at an early stage. The lavatories are particularly vulnerable to fires because of: 1. the inability of cabin crew to monitor all passenger uses of the lavatory; 2. the design of the lavatory to provide forced air ventilation for odor prevention which could promote fire propagation; 3. the private nature of the lavatory even when unoccupied. With the door closed, there is little indication of fire to outside observers. In recent tests, two minutes had passed before even wisps of smoke w ere visible . By then a fire is hard to contain with onboard portable exti nguishers.After a warning, a means to combat an existing fire in a lavatory without opening the door should be developed (NTSB Recommendation) . Lower lobe galleys should have detectors with warning systems that activate in the lower galley as well as the main deck service center since there are times on the ground and in flight when the lower galley is not occupied by a crewmember. An alternative is designing for fire containment, as discussed earlier in this report. Countermeasures for Postcrash Fire Injury A. Aircraft Structure Based upon presentations made to the SAFER Committee and its technical groups, but not discussed or evaluated in detail, the following areas relating to the structure of the transport aircraft may be worthwhile for research, evaluation outside the SAFER Committee: 1 . Emergency Exits The design of aircraft exits should consider outside visibility as well as the ability to close off an exit inadvertently opened. a . Design aircraft door windows to provide flight attendants with sufficient visibility downward and outward to assess conditions on the ground. ("Assessment of evacuation condition," is the flight Rttendants first step in an evacuation.) b. Examples of alternate aids which should be considered are heat sensors or fiberoptic viewing devices which could be placed at exits. c. Once a door has been opened inadvertently due to lack of vision of the ground or a noncrew member opening an exit , there should be a means of closing the exit/opening to preclude venting of fire, heat and fumes into the cabin. Narrow-bodied aircraft doors have closing capability since they are manually operated. However, on wide-bodied aircraft the emergency door opening mode is pneumatic (DC- 10, 747) or springpowered (1011). Once the door handle is actuated in the emergency mode the door is opened and may not be closed in all cases . This is a factor which must be considered in protecting occupants from intrusion of flames from exterior fires. B. Aircraft Interiors Based upon presentations to the SAFER Committee and review by some members of design proposals being discussed in the industry , (but not discussed or evaluated in detail by SAFER or its Technical Groups) the following modifications or studies involving aircraft interiors should be evaluated beyond the SAFER Committee considerations:

7b1. Distribution of Emergency Lights Accident experience has shown that overhead emergency lights currently installed in cabin ceilings and over exits often become obsecured by smoke from burning fuel and aircraft components. This not only prevents rapid visual location of exits by passengers but also eliminates the light source necessary for illuminating an aircraft interior. In view of the potential for obscutation, additional emergency lighting placed at or below armrest level should be considered to provide emergency evacuation guidance and illumination in the relatively clear air found at lower cabin levels. 2. Firehardening of the upper cabin In addition to the hazard of smoke obscuration heated air also collects in the upper cabin. This stratification of smoke and heat means that the upper cabin can be rapidly subjected to high heat . While passengers and crewmembers have avoided the hazards of smoke and excessive heat by bending low or crawling when exiting the cabin, their egress and survival may be impeded by the effect of the heat on upper cabin materials and equipment. Tests and accident experience have demonstrated that ceiling panels sometims begin to deterioriate structurally while the lower level of the cabin may still be livable. Should deterioration of overhead panels occur, it can represent an impediment to successful evacuation and a source of injury. Further, equipment which is used to aid egress, such as lighting and public address systems, can be disabled by excessive heat . Electrical wiring in overhead areas may be equally vulnerable . For this reason, the upper area of the cabin should be protected to an appropriate level. Relocation of emergency equipment from upper areas may be appropriate, and regulatory attention should consider to the differing fire hazards of upper and lower cabin areas . 3. Tactile Placarding (signs read by feel or touch) Armrests and overhead compartments at rows associated with emergency exits should have a tactile system of identifying markings to facilitate location by crew and passengers whose vision has been debilitated by smoke and combustion. Such markings would be of critical importance to blind passengers. C. Crewmembers The effective intervention of crewmembers during a postcrash fire or any other emergency is necessary for the ultimate survival of the aircraft occupants. For this reason, certain protective measures should be taken on behalf of the highly trained crew to ensure their ability to provide leadership during the emergency .



### 751 . Training The subsequent discussion, also beyond the scope of the SAFER Committee is offered for consideration outside the SAFER Committee. All crewmember training should incorporate Qaterial derived from the latest industry and FAA testing which demonstrates the hazards of aircraft fires and suggests actions and procedures appropriate for the fire situation. Education regarding stratification of heat and gases , fire patterns, fiber fabric flammability, necessity for crawling or stooping during cabin egress, and the effects of smoke and gases on mental acuity and judgment should be incorporated in required crew training . 3 . Protective Equipment Any special protective equipment provided for crewmembers must be located at their stations and be immediately accessible. Crew ability to aid passengers ln evacuating an aircraft during a fire may be enhanced by protective breathing devices and gloves; however, tests should be conducted which address the specific problems of time required to don the equipment, ability to direct passengers and be understood, and freedom of
**move~aent .** 



### 76

### VIII

**ASSESS~~NT** 

### OF ADeQUACY OF CURKENT

**~TANDARDS** 

### AND EXISTING TECHNICAL BASIS FOR NEAR TE.ID\ UPGMDING OF RULES Interior l1aterials: An assessment of the adequacy of current standards begins with the issuance of

**~PRM** 

### 69-33 on August 

### 12, 1969. This notice considered amending many

**~P.~tions** covering emergency evacuation and operating procedures in addition to materials fire safety. It was the result of much study and testing by the FAA, materials producers , suppliers and the airframe industry. The pertinent sections of 

### 69-33 dealt with compartment interiors, cargo and baggage compartments and electrical system fire and smoke protection. Those sections, with relatively minor changes are current in todays 

### FAR Part 

### 25 Amendment 

### 25-32. The 

### 69-33 rules "-'ere prepared to be used in procurement specifications as acceptance criteria for materials as well as minimum standards for assemblies as installed in aircraft. ASU1 tests, nonstandard tests and other special t ests were devised such as for ceiling panels in an effort to simulate real f ire situations. In addition to test method development, all candidate aircraft materials that could be made available from a country-wide search were tested to determine the then current state- of-the- art flammability level . With this background some tests were found more

**suit~ble** for specific shapes or generic classes. All had various degrees of severity but were not correlatable with each other and none could measure how a material would burn in actual fire scenarios . With no technology available to relate lab test$ to actual tires the Bunsen burner test was selected as the most suitable materials test for industry needs. A significant improvement was made, however, from a horizontal burn rate requirement in prior rules to a self- extinguishing requirement for large area materials in a vertical position. This Bunsen burner test, was and still is , a very good measure of the materials flammability, as well as a good rating method for self- extinguishing material . **}~terial** improvements have been made to reduce flammability . This was usually done by adding self-extinguishing agents to existing materials which may increase both smoke and toxic . decomposition products . In an effort to continue improvement in aircraft fire safety the FAA requested comment s on two new proposed rules, one for smoke and another to measure toxicity . It was then recognized that fire , smoke and toxicity could not be considered individually , but must be combined so the proposed rules were properly withdrawn . The wide-body jets were then just being designed and FAA required that smoke data be submitted on interior materials to assure that smoke was considered in the normal material selection compromise. During this 10 year time period efforts were not lacking to increase safety by improving materials, laboratory and full size fire test methods and analytical modeling of fire . In retrospect , one of the largest programs relating to a single subject (i . e., fire safety) was undertaken in this country by involving representative groups from all organizations involved in


### 77fires . Specifically related to aircraft was the NASA FIREMAN program, the many FAA programs including construction of the new burn test facility at NAFEC, the many programs by trade organizations representing the material producers and their in- house and supplier work, the new courses and programs at universities as well as the aircraft industry itself. Concern was expressed by many persons and organizations that a test for a "self-extinguishing" or "fireproof" material by its title was misleading in the way it might react in an actual fire. In addition, a method urgently needs to be developed to

**r.te.lsur~** how "good" a material really needs to be since it was recognized that material improvement beyond 3ome point would do little to improve personnel survival but would be very costly. Design Goals and Mandated Standards : Industry design goals are to meet or exceed every FAk mandated requirement. Improvements in safety are a **never-endin~** design goal of government and industry. This is evidenced by periodic upgrading of FAR standards and incorporation of advances in aircraft design by industry . When considering advanced technology , Federal Air Regulations normally lag behind industry because of finite times required to revise existing regulations. Industry often incorporates newly developed technology during these periods . It would be difficult for government to eliminate this time lag since most new technology is the result of industry research and development programs . If new technology is produced by government, it is then necessary for industry to evaluate its full impact prior to FAK incorporation. When considering state-of- the- art improvements , federal regulations can, and often do, lead industry . This normally occurs when government decides to upgrade standards by incorporation of proven existing hardware or
**techno~ogy .**  Sometimes , this is a result of current aircraft accident investigations which may reveal facts not previously known or understood. In addition a review or accident data has shown that the major survival fire threat is not the in- flight fire but rather the survivable impact post-crash fire . Comments relative to the aircraft fuel ' s part in this accident scenario are contained in later paragraphs . Existing technology consists of many tests for flammability , smoke and toxicity . It is recognized that these three types of hazards cannot be rated individually to determine whether a material has been "improved" . For this reason a number of tests have been attempted in a series of "screens" to rank a material in the same sequence as a selected fire scenario in a fuselage test section. After considerable effort, this has been found largely unsuccessful because a material in the usual standard laboratory test does not "see" the same heat flux and oxygen flow present in a large fire . Toxicity and flash fire have not been included in this approach either and particularly toxicity has been considered necessary for rule making . Technology is only now being developed which can analytically relate laboratory data to cabin environments and eventually some form of this approach may be the basis of a new rule. Existing test facilities range trom those required for materials qualification to those useful in design evaluation and fire research.

**t~st** 

### 78concerns in the airplane material business have a capability to perform the standard Bunsen burner test for material qualification, some are able to perform the smoke test using the NBS chamber and a range of capability in toxic gas analysis. Most airrrame manufacturers have additional test and analysis capabilities including the Ohio State University Release Rate Calorimeter and various scales of Fire Simulation Facilities. A large Cabin Fire Simulator is available at McDonnell Douglas and a full scale C-133 fuselage simulator is at NAFEC. Other specialized aerospace facilities are located at NASA Ames , Johnson Space Center and Boeing. Standard tests have been established for flammability and smoke and are accepted by the testing community. No standards have yet been established for the Ohio State Calorimeter nor products of combustion. A major technical deficiency at the present time is the lack of a good modeling technique. Fire modeling for aircraft is different from general fire modeling such as for buildings. Building fire models includes more detailed physics principles than is needed for aircraft and these should be properly eliminated. Two fire models are needed for aircraft and both terminate at flashover rather than full destructive involvement of a structure. The first, for material rating, must predict the cabin environment from laboratory data. The second predicts flame propagation in a cabin and can be used in design and for evaluating safety. A second major deficiency is our lack of understanding of toxicity. Technology is lacking in the definition of the maximum time an occupant can breathe a given gas concentration in a cabin environment . This is further complicated by combining gases at elevated temperature. Psychological factors involve a level of understanding technology which is apparently beyond our current capability. · This understanding is needed for ultimate accuracy which may never be achieved, but a total understanding not needed for rulemaking. In the case of toxicity, panic or fear would increase breathing rate and therefore decrease escape time. It is believed that after approximately 10 years of attempting to develop coherent and useful rules, programs are now underway that will develop the technology, facilities , test methods and costs from which one or more of several approaches for rules may be selected and direct future research needs. Existing rules which employ the current FAR Part 25.853 , 25 .855 , and 25.1359 bunsen burner flammability tests, coupled with nonregulatory smoke testing and a knowledge of thermal decomposition products , provides the designer with reasonable input for the usual compromises in selection of materials. Fullsize component tests in simulated fire tests prove the suitability of new aircraft designs. 

### As there is no data or technique available to correlate th increase in cabin survivability with each improvement, experience is used to decide on the importance of employing newer materials and designs. Recent accident statistics indicate this procedure is reasonable even though it may not be the theoretical optimum. The Committee has identified an area where an improved test method should be quickly incorporated. The vertical Bunsen burner test (FAR Part 25, Annex F)should be modified to provide a better test for materials which drip and burn away from the burner flame. This change may evolve into a separate approach for materials required to be tested, e . g . , 1" thick (foam) and others , but is within the state-of- the-art and could be the subject of a near-term regulation change. A STN Subcommittee F- 7 is already charged with responsibility to recommend a revised test for regulatory purposes . Laboratory tests indicate that the radiant heat resistance of emergency escape slide material can be substantially improved. Materials have been developed which reflect radiant heat and extend the useful exposure life of the slide, and are now being evaluated by the FAA. For the long term, as discussed above, the OSU calorimeter device modified for smoke and toxic gas measurement, probably coupled with an analytical model to relate OSU test data to cabin environment , show promise for providing the basis for regulatory action. Standardizing tests to run in the unit and agreeing on personnel hazard limits is yet required to achieve a meaningful measure/correlation of human survivability in a postcrash fire situation. Full-scale cabin-fire testing in facilities such as the FAA and other government industry facilities provides for baseline data for cabin fires. It is not intended that regulations would be written around these tests; rather, the data provides guidance for more detailed design improvements . It is expected that full- size component testing (e . g., waste containers) in realistic fires will continue to provide rationale for improving both materials and designs, regardless of future rules for materials .

**RECO~lENDED** GOALS FOR FAA RULEMAKING Cabin Materials and Evacuation Slides The Committee perceives that the existing FAR 25 Bunsen burner test is adequate for separating burning from self-extinguishing materials and for measuring the flammabili ty of self- extinguishing materials except those which drip and melt away from the flame. For the materials that drip and melt away like polyurethane foam, a revised FAR test method should be developed. Development of a radiant panel test method and an improvement in the heat r esistance of evacuation slides will be completed in the near future . These improvements should be evaluated and implemented as soon as they are available . Fuel System The SAFER Committee believes that technology exists to support rulemaking to minimize the hazard of fuel tank explosions during post-crash fires . It is considered that fuel tank vent flame arrestors or explosion suppression systems used in some commercial production aircraft to protect against lightning-induced ignition at fuel vent outlets might also be able to delay propagation of ground fires through the vent system and the subsequent explosions in intact fuel systems to provide additional time for safe evacuation. 

# so

## • A flame arrestor consists of a web of quenching channels. When a flame front enters a relatively cold quenching channel, heat from the flame flows into the channel wall at a rate exceeding the rate of heat generation so that the temperature decreases and the combustion reaction ceases. If the total heat capacity of the arrestor is small, then the temperature of the arrestor will increase rapidly to a value where the arrestor fails. A flame stabilized on the flame arrestor surface could heat a normally quenching channel to a temperature where the flame can penetrate unless the cooling effect of the unburned gases approaching the flame arrestor maintain the quenching surfaces below the fuel ignition temperature. However, it is believed possible to design an arrestor to prevent flame penetration and propagation through the vent system for a period of time equal to the time required for an external fire to penetrate the undersurface of an empty wing tank. Testing of flame arrestors in a simulated crash fire environment has not yet been conducted and would be necessary to obtain basic data on their effectiveness in this environment. An explosion suppression system includes a flame radiation sensor in the vent outlet tube to detect the presence of an oncoming flame front and a fire extinguishant discharge system in a fuel tank for automatic early and rapid suppression of the combustion process when it reaches the tank. This system can provide fuel tank vent explosion protection similar to a properl y designed flame arrestor if provision is made for adequate extinguishant dispersion. This requires continued availability of electrical power to enable sensing of any internal combustion process induced by external fire effects and triggering of timely extinguishant dispersal . In addition the system must be capable of effective operation at elevated temperatures due to external heating effects . Data on explosi9n suppression system tests in a simulated crash fire environment are needed to substantiate their effectiveness in this environment . The SAFER Committee also believes that technology exists to minimize the post- crash fire hazard by providing means to shut off engine fuel supplies to further reduce fuel fire possibilities.REFERENCES AND BIBLIOGRAPHY l. Lucha, G . V. , Robertson, H.A., and Schooley, F. A . , "An Analysis of Aircraft Accidents Involving Fires , " National Aeronautics and Space Administration, Report NASA CR 137690 2. CRC Report No. 482, "Aviation Fuel Safety - 1975." November 1975 

### 3. Report No . FAA-RD-75-156, "A Crashworthiness Analysis with Emphasis on the Fire Hazard: U . S. and Selected Foreign Turbine Aircraft

**Accid~nts** 1964-1974 , " July 1976 4. Paper Prepared by A . F. Taylor , "An Evaluation of Worldwide Transport Aircraft Fire Experiences," September 1976 5 . Report No . NTSB- AAS-77-1, "Special Study -- U.S . Air Carrier Accidents Involving Fire 1965 through 1974 and Factors Affecting the Statistics , " February 1977 6 . Paper prepared by H . C. Black, "Transport Category Airplane Post- Crash Fuel Systems Fire and Explosion Hazard Reduction," June 1977 7. AGARD Report No. 132 , "Aircraft Fire Safety," November 1979 8 . Nationa! Transportation Safety Board, "Aircraft Accident Reports," Periodic 9 . SAFER Interior

**~Ia**terials Short-Term Action Sub- Group , "The Contribution of Cabin Supplies and Carry- On Items to a Post- Crash Fuel Fed Fire," September 1979 10. **NBS-GCR-7~-168 ,**  "Human Fatalities rrom Unwanted Fires," December 1978 11. "Special Study : U . S. Air Carrier Accidents Involving Fire 1965 through 1974 and Factors Affecting the Statistics," National Transportation Safety Board, keport NTSB- AAS-77-1 , February 17 , 1977 . 12. "Investigation of Aircraft Fuel Tank Explosion in Nitrogen Inerting Requirements During Ground Fire , " Richard Hill and George 

### R. Johnson, October 1975, FAA - RD-75- 119 13 . Boeing Commercial Airplane Company Hemo, B-9200- 3- 371 , "Cost Update of LN2 Fuel Tank lnerting Economic Study," dated Sept ember 14 , 1979 14. " Factors in Using Kerosene Jet Fuel of Reduced Flash Point , " Dukek, Strauss Editors; American Society for Testing and Materials Report , STP 

### 688, 1979

82

### 15. Hill , R. G., Johnson, G . R . , and Sarkos, C. P., "Postcrash Fuel Fire Hazard Measurements in a Wide Body Aircraft Cabin," Federal Aviation Administration, NAFEC, Report FAA-NA-79-42, December 1979 16. Eklund, T. I., 

### "Pool Fire Radiation through a Door in a Simulated Aircraft Fuselage," Federal Aviation Administration, NAFEC, Report FAA-RD- 78-135 , December 1978 17. "Aviation Safety (Aircraft Passenger Education-- The Missing Link in Air Safety)," Hearings before the Subcommittee on Investigations and Review, House Committee on Public Works and Transportation, 95th Cong. , 1st Sess . (1977) 18. See Federal Aviation Regulations, Parts FAR 121 . 571 , 121 . 573 19. U . S. Civil Aeronautics Board, "Fly-Rights: A 

### Guide to Air Travel in the United States," (5th Rev. Ed., July 1979) 20. "Special Study : Safety Aspects or Emergency Evacuations From Air Carrier Aircraft," National Transportation Safety Board; Report NTSB-AAS- 74-3, November 13, 1974. 21. Engineering and Development Program Plan Antimisting Fuel, FAA-ED-18-4, June 1980.