USDeportment ofTransportation FederalAviation Administration Office of Aviation Safety Washington , D.C. 20591



# g ;oo3! 

# f-0 &'ltif 

# LU:l\ f\ r

**r- ~r**  **o' /'**  - r.\1

**~**

**i ~**  FM-ASF-80-4



# Specia~ 

# Aviation Fire and Explosion Reduction (SAFER) Ad- visory Committee Final Report Volume I

June 26, 1978 through June 26, 1980 )

Document is available to the public through the National Technical Information Service, Springfield , Virginia 22161 .Technical Report Documentation Page 1.

**R~port** No. 2 . Government Accession No. 3. Recipient's Cotolog No. 

### FAA-ASF-80-4 4. Title ond Subtitle 

### FINAL REPI)RT OF THE SPECIAL AVIATION FIRE AND EXPLOSIOtl

**REDUCTIO!~** 

### (SAFER) A .f)V!SORY C0Mt1ITTEE S. Report Dote 

### June 26, 

### 1980 6. Perform ing Or11oni zotion Code 

### ASF-300

**h--:--.-~:----- ---**  **--------- ----~**  8 . Performing Organization Report No .

7 , Authorls)



### J . H. 

### Enctcrs (ChairMan), E. C. **\~oo<1** 

### (Executive Dir.} 9 . **P~rform in**  **g** Orgonizotoon Nome ond Address 10. Work Unot No. (TRAIS)



### SAFER Advisory

**Co~mittee** 11 . Contract or Gront No . t-:":::--:-----------,..,-- -------- -------11

**~.** Ty[f oRReport tnd Period Covered

12. Seonsoring Agency Nome ond Add o ess 1

### na ep0r Jftice of 

### AVli!tion Safety June 26 , 

### 1978- June 26, 

### 198C

**Fe~eral** 

### Aviation AdMinistration U

.S. DepartMent of Transportation

**Washingto~,** 

### O.C 

### ?0591 1S. Supplementary Notes

16. Abstract 14. P'onsoring Agency Code 

### AS, - 1



### Thc> Special Aviation Fire anti Explosion

**Re~uction** 

### (SAFER) Advisory Committee and its technical supporting groups spent nearl y 13 months from !'<lay 1979 through June 1980 examining the factors affecting the anility of the aircraft cabin occupant to survivE in the

**post eras~**  

### fire environment and the range of solutions available. Having onl' a li m ited amount of ti "le available, tre Committee confined its examination to large transport category aircraft, reasoning that recom mendations develooed could provide the necec;sary g11idance for the FAA to address the broader spectrum of airplane and rotorcraft fire safety improvem P.nt. Durin9 t he course of this assignment, certain

**to~ics** 

### that were

**ou~side** 

### the scope of the Committee, yet have some bearing on aircraft fire in

**gen~ral, wer~**  

### i oentified but not discussed by the Committee. Some of thesE:' topics \'Jere felt to be 

### worthy of further examination by the FAA or by some other borly of advisors constituted for that purpose. These topics are not addressed in this report. Presentations were made to the SAFER Committee by Committee members , technical surporting grou!'S, the FAA, citizens and private firms. The broadly-constituted bod' of information developed and presented to the Committee formed the basis for Comnittee Findings

**an~ Reco~l"lendations.**  

### The Committee focused i ts recommendations o solutions or interim **im~rovements.**

17 . Key Words



### Post Crash I 

### nfl i ght Fire SAFER Cabin Materials Fire Safetv Occupcnt Survival 18. Di s tribution Statement 

### Document is available to the U .S. public through the National Technical Information Service, Sorir.gfield, Virginia 22161.
19. Security Clauif. (of this report) 20. Securi ty Cloaalf. (of this poge) 21. No . of Poges 22. Price



### Uncl assified Unclassified 82 Form DOT F 1700.7 (8-72> R eproduction of completed pave authorized

### CONTENTS

1 PREFACE 12 

### SUMMARY 20 I - AIRCRAFT POST CRASH FIRE PROBLEM DEFINITION 28 II - GENERAL CONSIDERATIONS OF AIRCRAFT FIRE AND EXPLOSION HAZARDS 34 

### III - FIREWORTHY MATERIALS 

## 37 IV - TOXICITY AND SMOKE 46 V - FUEL SYSTEM FIRE HAZARD REDUCTION 63 VI - R 

### &D CONSIDERATIONS 

## 73 VII - CREW PROTECTION AND PASSENGER EVACUATION 

## 77 VIII - ASSESSMENT OF ADEQUACY OF CURRENT STANDARDS AND EXISTING TECHNICAL BASIS FOR NEAR TERM UPGRADING OF RULES

Distribution: A -W(VS/FO/SF/CS/WS)-2; A-X(FS)-3PREFACE Fire has always been a safety concern throughout history. In the aviation field, aircraft fires are similarly of concern to the designer, the operator, and of course , to the aircraft occupant . Since the advent of the jet transport aircraft , these larger structures have offered considerably improved occupant protection in the event of a crash . However, aircraft tires, ranging from small easily controlled events to intense post- crash fires resulting from large fuel spills, though rare , continue to account for some loss of life or injury to occupants in aircraft accidents . To examine the possibilities for further r educing the severity or occurrence of aircraft fires and explosions , the FAA established the Special Aviation Fire and Explosion Reduction (SAFER) Advisory Committee . This report is a

**sum~ation** of a year-long study of the problem by the Committee and supporting groups . The report consists of two volumes: Volume I contains a summary of the Committee ' s finding s and recommendations, along with discussions of the major factors affecting aircraft fire, occupant survivaLility, and prospects for safety improvements in the context of state-of- the-art understanding . Selected re fer ences to current technical literature pertaining to aircraft fires and explosions complete Volume I . Volume II contair.s SAFER-generated material, consisting of reports of technical support groups, briefings and the summary proceedings of the SAFER meetings . Events leading to the establishment of the SAFER Advisory Committee began with two FAA public hearings in 1977 . The fi rst, in June , considerec fire and explosion hazard reduction . The second, in tJovember, dealt with the fireworthiness of compar tment interior materials. As a consequence of the information developed at those hearings, the FAA concluded that the pending rulemaking actions on fuel tank explosion protection flammability, toxicity and smoke production concerning cabin materials were premature and subsequently withdrew in favor of a careful reexamination of the technologies involved in reducing those hazards . To focus advice from all interested segments of the community at large for this r eexamination , the FAA established the SAFER Advisory Committee on June 26 , 1978, with an Office of Hanagement 

### & Budget (OMB) approved term of 2 years .* The charter of the committee states that it shall "examine the facto rs affecting the ability of the aircraft cabin occupant to survive in the post-crash environment and the range of solutions available . " Selection and approval of committee members in accordance with the established Federal regulations took approximately 11 months . The committee met for the first time on May 10-11, 1979 , at FAA Headquarters in Washington D . C. In view of the remaining term of about 13 months, the scope of the committee ' s activities was limited to transport category aircraft and to design aspects of the ai rcraft relating to fire and explosion reduction . ** *SAFER was established in accordance with Public La\v 92- 463, Title V, U . S. Code, Appendix 1 . **FAA Agency Order 1110 . 88, April 6, 1978.
1Furthermore, the committee agreed to concentrate its attention on impact survivable accidents where control of fire and explosions might enhance occupant survival. The committee was charged with a request from the Administrator to report by October 1, 197Y, in an interim fashion on what rulemaking actions could be undertaken immediately to improve fire and explosion safety, and also on what additional actions are necessary for FAA to undertake for the improvement of fire safety . The Summary of Proceedings for the SAFER meeting of September 24-28, 1979, in Volume II, contains these interim recommendations. In addition to the chairman and executive director, the SAFER committee membership consists of 24 representatives spanning the spectrum of international aviation inter ests . Airlines , canufacturers, universities, public and pr ivate sector research establishments, flight and cabin crews, and consumer organization repre sentation is included as shown in the listing at the end of this section. To provide the detailed information needed by the broadly- constituted SAFER committee, two technical working groups were organized, one on compartment interior materials and the other on pose-crash fuel system fire hazard reduction. These working groups employed additional specialist sub-groups to: examine short-term rulemaking possibilities in materials, material systems, toxicology , materials evaluation and testing, cabin fire safety, and evacuation slide integrity; to review and identify research and development needs; to review the accident statistics data base; to review iuel tank inerting and explosion suppression concepts; to review crash-resistant fuel tank technology ; anu to examine the potential of antimisting kerosene concepts . Considering the totality of the committee, its technical support groups , and the additional people who were brought into the process of examining all of the data availabile , approximately 150 of the world's top experts in fire research, operations , accident investigation, materials development, systems design and aircraft fire and occupant safety were involved . The technical working groups met on June 26 and 27 , 1979 , at FAA' s Nat ional Aviation Facilities Experimental Center (NAFEC* ) to establish the procedures by which the speciality groups would convene and interact in order to respond to the Administrator's charge to the Committee .

**r~n y**  small meetings of the specialists followed in July , August, and September . The Technical G roups met on September 24- 26 , 1979, at NASA Ames Research Center to consolidate the sub-group information and prepare their reports to the parent SAFER Committee on September 27-28. Out of this week-long meeting emerged the interim recommendations to the Administrator . Those r ecommendations were considered by the FAA in preparation for the meeting in Los Angeles , March 4-6 , 1980, where formal responses to those recommendations were presented by the FAA. Positive action plans for all the recommendations were outlined by the FAA. In addition, arrangement of the final report was discussed and plans were made for the final SAFER meeting at the FAA Technical Center. This meeting took place on June 19- 20, 1980, where the draft report was discussed. Inputs were used for subsequent editorial review in Washington, D. C. on June 26, 1980 . 

### 2

### A listing of the membership of the SAFER Advisory Committee and the Technical groups on Compartment Interior materials and Post-Crash Fire Hazard Reduction follows: *NAFEC was renamed FAA Technical Center on June 1, 1980.



### 3

### SAFER Advisory Coomit tee MeJrbership J. 

### H. Enders, Chairman E. 

## c. Wbod , 

### Executive Director J . 

### A. Bert

, J. 

### Chavkin R.

**t~ .**  

### Clarke (Alternate) 

## s. Davis (Alternate) J. M. Del 

### Balzo

,J. 

### E. I))I.J)herty (Alternate) W. M. 

### F'annin:J M. 

### CJOland G• N. C':l)()dman 

## s . J . 

### Green G. Hartzell (Alternate) B. 

## v. Hewes 

## c. F. Hitchcock K . E . fiodge 

### Aviation COnsultant Federal Aviation Administration Office of Aviation Safety American Petroleum I. nstitute Federal Aviation Administration Chief, Aircraft Engineering Division , Office of Airworthiness Air Line Pilots Association Staff F.ngineer Nationa! Bureau of Standards Center for Fire Research Federal Aviation Administration Director, National Aviation Facilities Expedrnentol Center General Aviation Manufacturers Association Hational Business Aircraft Association Manager, Technical Services Southwest

**~search** 

### Institute President International Air Transport Association Director, Engineering &

### Environment General Aviation t1anufacturers Association Vice President-General Oounsel Southwest Research Institute Air Line Pilots Association Chairman, ALPA Rescue & 

### Fire Oommittee Aviation Oonsumer Action Project Attorney National Aeronautics and Space Administration Transport Aircraft Office 

### 4C. Huggett E. L. Hutcheson C. W. HcGuire L. R. Perkins E. Podolak
J . P. Reese S . H. Robertson J. Searl<.! J. D . Tanzilli (Alternate) E. L. Thomas A. R . Tobiason

**(Alternat~)**



### 5 National Bureau of Standards Deputy Director, Center for Fire Research Helicopter Association of America Safety Consultant Department of Transportation Office of Environment 

### & Safety E. I . DuPont de Nemours Representing the Society of the Plastics Industry Federal Aviation Administration Program Scientist, Office of Aviation Medicine Aerospace Industries Association Di. rec tor, Airworthiness Programs Arizona State University

**Dir~ctor ,**  Safety Center Association of Flight Attendants Coordinator, Fire 

### & Rescue

**Co~~ittee** B. F. Goodrich Company Chemical Division Air Transport Association Vice President - [ngineering National Aeronautics and Space Administration Transport Aircraft OfficeTechnical Group on Compartment Interior Naterials H . L \vilfert, Group Leader S . Davis, Deputy Group Leader R. Allen 

### B. R. Aubin 

### r. . Bara H. eraoting R. B ricker
C. R. Crane A. D . Delman J. J . Fargo R. G . E. Furlonger (Observer only) J . R . Gibson R. A . Kirsch

\.J. C. Long

6 Douglas Aircraft Company Senior E ngineer/Scientist National Bureau of Standards Center fo r

**Fir~** Research federal Aviation Administration Chief , Airframe

**~ranch,** Office of Airworthiness Ai r Canada General Nanaeer - Engineering Boeing Commercial Airplane Company Chief Engineer, Payload System Ft:!deral Aviation Administration

**A~rospace** Cnginter, Airframe Branch, Office of Airworthiness National Aeronautics and Space Admini.s l ration Lyndon B. Johnson Space Center, Structures Branch Federal Aviation Administration Civil AeromedicaJ Institute, Aviation Technology Lab The Wool Bureau Manager, Testing Services

**Lockh ~e**  **d** California Company British Embassy Civil Air Attache - Safety E. I . DuPont de Nemours 

### & Co. Manager of Toxicology Federal Aviation Administration Special Programs Division, Office of Aviation Safety E. I. DuPont de Nemours Man-made Fiber Producers Association

## ) R. **~adding** J . 

### C. Martin 

## c . ,J . 

### May K

. C. McAlister (Observer Only) M

. M . McCormick (Observer Only) C. W . McGuire G. L. Nelson D. G. Onderak 

## ) .J . 

### A . Parker



## c. Patterson J . D . Ray 

## c . Sarkos
M. J . 

### Sal kind H. 

## c. Schjelderup

7 

### Cessna Aircraft Company Manager, Aircraft Styling British Aerospace , Inc . Chief Design Engineer - Equipnent and Furnishing De1

### ta Airlines Vice President - Engineering Celenese Fibers Marketing Co. t1anager - Cornnercial Developnent Hational Transp::>rtation Safety Board Senior

**~ir** 

### Safety Investigator, Bureau of 'Iechnology Department of 'JXanspoctation Office of Ehviconment and Safety General Electric Company Tvlanager, Combustibility Technology John Schneller &

### Associates Technical Director National Aeronautics and Space Administration Chief, Chemical Research Projects , Ames Research Center Polyplastics International , Inc. United Technologies Corp ., Sikorsky Aircraft Division f1anager, Subsystem Design & 

### Developnent Federal Aviation Administration Progran Manager , Aircraft Systems Fire, National Aviation Facilities · Experi1 nental Center National

**~eronautics** 

### and Space Administration Project Manager, Composite Structures Ibuglas Aircraft Company Director , **~~terials** 

### &

### Process EngineeringJ . 

### D. Simon D. R. Spicer D. F . 

### 'Ihielke
G. Walhout (Observer Only) G. H. \'lear Gates Learjet Corp.:>ration Group Engineer, Materials & 

### Processes Jbckwell International Corp. Haterials & 

### Prcx...""esses Flight Engineers International Association Vice President - Air Safety & Engineecing Hational Transportation Safety 'Fbard Chief, Human Factors Division , Bureau of Technology

8 

### 'fue f'..eneral Tire &

**Rubb~r** 

### Co. r-tanager , Technical Sales ServicePost- Crash Fire Hazard Reduction Technical Group E. F . Versaw, Group Leader 

### R. D . Appleyard 

### B. 

### P. Botteri I. A . Burgess 

### R. 

## .c. Bywatf:!rs 

## w

. G . Dukek T . Eklund K. Fisher R. G . E. **Furlon~er** (Observer Only) J . D . Galloway G. 

### J . Grabowski L. Hebenstreit T . Horeff

C. C. Kimmel R. A. Kirsch Lockheed-California Co . Research 

### & Development Engineer ing Explosafe America, Inc. Air Force Propulsion Laboratory Chief, Fire Protection Branch Explosafe America, Inc. U.S. Army Research 

### & Technology Lab AircrafL Safety Specialist Exxon Research &

**~1anufactu ing**  Co. Federal Aviation Administration Project Engineer, National Aviation Facilities Experimental Center Lockhecd-California Co. SafE:ty Engineer British Embassy Civil Air Attache - Safety Uniroyal, Inc. Chiet Engineer, Fuel Cells Fenwal, Inc . Vice President - Protective Systems Division Walter Kidde 

### & Company New Products Research Specialist Federal Aviation Administration Chief , Propulsion Branch, Aircraft Engineering , Office of Airworthiness Parker Hannifin Corp. Program Manager , Fuel Tank Protection Systems Federal Aviation Administration Special Programs Division, Office of Aviation SafetyJ • 

### T. Leonard A. T. lDthrigel (Alternatt:) T . 

### Madgwick 

## s . A. . 

### Manatt R. J . 

### Mannheimec

**~1 .**  

### M . McCocr:ticl< (Obser-ver- Only) E. 

### Nichols H• 

### Nordermeec D . 

### C. Nordstcorn N. 

### R. Parmet A. . 't' . 

### Peacock 

## c. M.

**~riani** 

### T. 

## w . Reichenberger K . Rosen R. 

### Salm:>n ij . 

## w . Schmic1t Naval Research Laboratory Head , Special Project section Parker ijannifin Oorp. Senior Design Engineering Manager , Fuel Tank Protection Systems British Aerospace , Inc . AiRescarch Manufacturing Oo . 

### of California Senior PrograJn Specialist

**SouL~west** 

### Resear-ch Institute National Tt:'ansportation Safety Board Senior

**~ir** 

### Safety Investigator , Bureau of Technology Piper

**~ircraft** 

### Gorp. Chief Powerplant Fng

### ineec l<k\1 

### fbyal Dutch Airlines Bngineering &

### Manufacturing Division Boeing COmmercial Airplane Oo . Chief Engineer, Propulsion Techoology Tt:'ans WOrld Airlines , Inc. Vice Presic1ent - Engineecing & 

### Quality Assurance D:::>UJlas Aircraft Cbmpany Powerplant Engineering TJ. s . Army 

### Research & 

### Technology Labs Aer-ospace Engineer Gates

**r~arjet** 

### Corp. Chief of Powerplants United Technologies Cbrp. Sikorsky A ircraft D ivision Federal Aviation

**~ministra ion**  

### Project Engineer, National Aviation Facilit ies Experimental Center l-Jational Aeronautics and Space Administration Research Engineer - Safety, Lewis Resear-ch Center

### H. Skavdahl H. O. Smith 

### T . 

### Street D. 

### F. '!hielke R. 

### Volz G. Walhout (!Jbserver Only) E. P. vvebb A. Weisner 

## s. Weiss J. 

### H. Wivell 

### L. A. '-Kight

11 

### Boeing Oommerci al Airplane Oo . Chief, Prop..tlsion Research & 

### Prellininary Design Goodyear Aerospace Oor p . Manage r, Engineered Fabrics Developnent Gates tearjet Oorp. Flight Engineers International Association Vice President - Air Safety & 

### Engineering Scott Paper Cbmpany Manager, Oomnercial Developnent National Transport ation Safety Board Chief, Human Factors Division, Bureau of Technology Firestone Ooated Fabrics Oompany

**~iper** 

### Aircraft Cbmpany Power Plant Engineer NASA, Lewis Research Center British Airways D::n.ijlas 7\ircraEt Oompany Powerplant EngineeringSUNNARY The Special Aviation Fire and Explosion Reduction (SAFER) advisory Committee and its technical supporting groups spent nearly 13 months from Hay 1979 through June 1980 examining the factors affecting the ability of the aircraft cabin occupant to survive in the post- crash fire environment and the range of solutions available . Having only a limited amount of time available, the Committee confined its examination to large transport category aircraft, reasoning that recommendations arrived at would provide the necessary guidance for FAA to address the broader spectrum of aircraft and rotorcraft Eire safety improvement . During the course of this assignment, certain topics that were outside the scope of the Committee, yet had some bearing on air craft fire in general, were identified but not discussed by the Cor.unittee. Some of these topics were felt to be worthy of further examination by the FAA or by some other body of advisors constituted for that purpose. These topics are not addressed in this reporL. Presentotions were made to the

**~AFER** Committee by Committee members, by the Technical Supporting Groups, by the FAA, and by individual public citizens and private

**fir~s.** The broadly-constituted body of information

**dev~loped** and presented to the Committee formed the basis for Committee Findings and l<ecommendations . The Committee focused its recommendations on solutions or interim improvements . At the FAA Administrator ' s reques t the Committee has provided some background discussions of factors involved in aircraft fire and explosion safety assurance that would expand on the findings and recommendations to reflect not only the present understanding of the these factors, but also some view of the outlook for improvements. Individual Committee members who are expert in a given topical area were assisted by the technical support group members in providing the background di scussions that follow this summary . The SAFEK Advisory Committee's advice to the FAA is embodied in this final report in the form of consensus findings and recommendations, background discussions, pertinent technical bibliography affecting aircraft fi re and explosion safety improvements, and Technical Support Group reports to the Committee. FINDINGS On the basis of the information available to it and the subsequent discussion, the SAFER Advisory Committee finds that: o The overall safety record of U . S . scheduled air carrier aircraft shows a continuing reduction in the fire - involved accident rate since the advent of Jet transport service in 1958 . The accident and fatality rates per passenger mile, based on available data, show a steady decrease over the past 15 years. (See Part I)

12**Ov~r** the past iS yea rs,

**ia .1lit~ef**  **J~E** ro postcrash fire ur its effects in U. S . schE'dulcC. air carr1t t lper... L :on5 8\'era!;e ahout 32 per year . In addition, occupants have

**bee~** seriously 1njured in survivable accidents where postcrash fires occurred . Thr ; exact number of those injured and the extent of

**inj urie~**  an. not avoilAble . (Sec Part I) o Ignition of aircr&f t fuel s; il!ed dut t o structural breakup during a crash is the primary caust. oi

**n~::arly** all aircraft post-crash fires. The major hazard in !JOSLcra5L a1rcraft tires i s the aircraft fuel supply . o Though outside the scOpL o:- t:l.l' 

### s:.:-:.:1{ Co"'lmi ttec, in-flight cabin fires leading to fatalities w ere round tu be rare events . lxcept for three non-U . S . accidents, all i n-ilight C dhi n fires have been controlled by means o f des.ign , tire txti"'t:uit-:hi-lb equi'Jra,nt and crew training . (See Parts I, II, \' and VII) o Tht availabl€ dcHa

**bac:.~** 01. ;ti rt ra lire accidents and incidents is inadequate t (

**determinl ~,**  1-1tl

**~.-or.liaLnc**... , the c rit ical chain of events in many ai r.::ratl (ires . **r~L·** l·n n 1) The rolE: of combusti bh' c11bi !1 c1,nl•

**·n~** vi s - a-vis spilled fuel, in c on tributin!' to t l...: haz:c.t c' 1 • ,ms:- - dd5l. tir(::s is not adequat ely deri ned by

**rr~sentl\ ~vn1!~hl.**  **a~cid~nt** data or laboratory data to penni t a preL i.c;e jud,!m(.r. : r.t 1 111,

**tl•~gr~P** uf sarety improvement adde<'l by subs tituting inpr1nL·1: r.:atu .

**d~ .**  \'w,• Porr•. 1 a nd III) Ac cident dat a

**indic<~t<::** a

**rrl~<'ri:sl** , **tr~;; ,,.:~f<"L/**  benefit tror.l materials used in present ,,:idE>-bod . _ i<'t ·d r c r c:.rt compart::d with those used prior to the FAA' s 19i2 revtsL)T1 <'f 'rcr.JI.t i nterio r material flammability

**standar d~**  **.** The Comrll•.::t · r-ot••"' :. 1:11 

### nt'''• improved Claterial s a!ld designs, exceed

**in~ th~~**  **·~** r c•_.j

**r•"t.~ :1:.~** . . are o(ter. incorporattd into aircraft cabin int<J r iors

**a~** :rHy

**b~"rOmt!** a\-ailable . (See Part I and lll There is a lack of universal l y accepted tes t methodology that will reliably predicl large

**seal~** tire Lenavior of materials based on small scale te5t s . (See ParL 1.) Current burn and smoke test me thod s provide the designer with a guideline for selecting materials on a comparative basis . Since these methods do not permit the asse ssment of the effect of 

### a given oater ial on the overall cabin rire safe ty level, further study of this area is needed. (See Parts 11, II I a nd IV) o Cabin interior panels and insulati on

**~ith** improved fire resistance are coming into production . This development promises to improve resistance against penetrat ion of an external fi re into the cabin . Improved tire resistant windows and cabin wall insulation materials are being evaluated for possible application t o the

**o~~ec** 01 fire pene tration resistance . (See Parts II and Ill) Materials that passcnper,.

**e.ar** or carq aboard an aircraft represent an uncontrolled source cf tl .. · fur a pc•sL - cra5h fire, that may add to the cabin inte rio r f1re . **(~t:e** h• l<> lJ a ,•d Ill) 

### 13o t\ear-term improvements in cabin fire safety can only be accomplished by new designs employing currently-available materials . The work on

**fir~-blockin g**  **lay~rs** for seat cushions is an example . Improvements that depend on new polymers and other break-throughs will of necessity be further in

**th~** future . (See Parts II and III) o Current technology indicates that the FAA C-133 test facility , in conjunction with NA::,A and industry large scale test facilities is the most reasonable method for evaluating designs and systems effects . Acceleration of the C - 133 test

**sche dul**  **~s** at the

**ne~>.•** FAA Technica 1 Center fire facility will likely satisfy the Committee ' :. interim recommendation concerning these tests . (See Parts II and Vl)

**Th~** state of rire modeling capdbJlity is a major technical deficiency at present . **~xisting** surface 5tructure fire modeling is not readily appl1cable t, aircraft . Predictive capability of valid rire models would greatly short en

**th~** t Lne uow m•eded to

**~creen** and evaluate

**mat~rials** and designs . (See Part Ill) o The Bunsen burner test now specified 1n FAR Part

**~5,** Appendix F, is a valid flammability test except for those materials that melt and thereby shrink away when the flame continuous to be applied . (See Part Ill) The 

### FAA, with cooperation from industry , is making good progr('SS in evaluating improvements to escape slides for fire heat radiation reSi$tance . (See Parts II and III) o The Ohio State University

**(OS ~)**  calorimeter testing device provides estimates of flame spread and rate ot heat release rates under a realistic radiation flux and, it successfully modified for smoke and toxic gas measurements, offers promise for providing a data base for regulatory actions . (See Part II) o Since 1959, four accident situations were identified involving fuel tank explosions which are now

**prev~nted** or substantially delayed by subsequent suitable design chang0s . **(~ec** Parts I and II) o The concept \vhic:h has the greates t potential Lor reducing postcrash fire risk is anti-misting kerosene (ANK) . (See Part lV) o Fuel tank inerting would provide very limited benefits in a post-crash accident where only minor tank rupture occurs . If a tank is not ruptured, the likelihood of fire is reduced . (See Parts II and V) o Translation of military aircraft fuel tank fire quenching foams and foils to large, complex, civil transport tanks presents design/ r edesign weight and maintenance difficulties and adds excessive operational penalties . o Little is known concerning the performance of military foams and foil under external fi re conditions br post crash fire situations accompanied by significant wing break-up . (See Part V)


### 14

# ) o The compl exity of presently available vent f ire suppression systems, w

hen extended to complet e fuel system protection, would introduce excessive operating penalties . **(~ee** Part V and VIII) o It is feasible to install crash-resistant fuel cells in the fuselage. It may be

**f~asible** to incorporate some degree of crash resistance in critical wing fuel tank locations. It is not feasible, in most conventional transport aircraft, to install all wing fuel in crash resi s tent tuel cells . Current FAR's do not preclude incorporation 

### oi such design feotures. (See Part V) o Toxici t y t est standards do not exist for aircrait fi re situations. Further, there is no agreement among specialists on the approximate magnitude (statistical) of the toxic contribution from burning interior materials relative to t he contribution from burning turbine fuel or other fire related hazards . (See Part IV) o There is incomplete data on the hazards from exposures of humans to toxic gas mixtures likely to be emitted from aircraft cabin materials or fuel during a fire . (See Part IV) o Irritants (gases and smoke) may have a real but unquantified effect on slowing egress from an aircraft. (See Part I V) o

**~tile** certain w ell done toxicity research projec t s have been carried out, there has been no substantial effort devoted t o understanding the overall toxic threat environment in aircraft fire situations . (See Part IV) o Reduction of the potential toxic threat from thermal decomposition products by controlled selection of interior materials on the basis of r elativt performance in a small- scale toxicity test with experimental animals cannot be recommended at this time. (See Part IV) For the purpose of materi al selection , assessment of relative toxicity, solely f rom results of chemical analysis for selected components of thermal decomposition products cannot be recommended at this time . (See Part IV) o Consistent with overall aviation budgetary needs, aircraft fi re research has , with the exception of toxic hazards assessment, been r easonably well funded since the early- to mid-1970 ' s. Improvements expected within the next year or s o are products of research begun in that period. (See Part VI) The development and use of fire scenarios that depict real fire situations would focus engineering and regulatory improvements on aircraft fire and explosion reduction, and toward improvements in evacuation procedures . (See Part II , V, and VIII) There is good coordination of aircraft fire R&D between the U . S . and European research organizations , resulting in more rapid progress than there would have been without this exchange. (See Part VI)On the basis ot LhPse tindings and the discussions that led to them, the Special Aviation Fi re dnct

**~xplol:iion** Reduction Advisory Committee recommends the following actions to the fAA . The SAFER

**Committ~e** urges the FAA to implement these recommtndaLions as quickly as possible. A number of proposals involve research and developmenL that \.Jill tai<E: several years to complete and, unless the R&D is begun soon , the target dates fo r completion will be pushed even further into the tuture. Such delay could retard introduction of the safety benefits derived from prompt action on these recommendations.

POSTCRASH FIRE HAZARDS RJ:.COMNE1WATIONS (In order of Priority)

o Expedite the investigation and validation of antimisting kerosene

**(A}~)** as proposed in the FAA, ANK

**!:.ngin~ering** and Development with the NASA and the United Kingdom agencies . The propused AHK/E&D program plan presented to the committee in

**~~rch** 1980 incorporates the SAFLR Committee interim recommendations on this topic, made in September 1979 . The Committee suppOrll:i the FAA planned target date of 1984 ior the establishment of the data base for initiating rulemaking procedures. NOTE: The Commit tee is ot the view that, if successful, the A}1K technology could provide the single most significant safety improvement to reduce the post-crash tire hazard . o Amend FAR Part 25 to

**e4uir~** luel tank vent protection during ground fires ) by adding a ne1. • paragraph l5.975(a)(7) to read: "Each vent to atmospherl! must be

**design~d** to

**minimiz~ th~**  possibility of external ground fi res being propagated through the vent line to the tank vapor space, providing that the tanh. and venL structur..- remain intact . " The Committee recommends that this action to

**am~nd** FAk L) bt=gin immediately and be completed within 12 months . o Amend FAR Part 25 to require design practices that maximize the probability of engine

**fu~l** supply l:ihut- off in potential fire situations . o Investigate the effect on fi re safety of reduced flash point of kerosene fuels. These should be investigated concurrently with the AMK research . NOTE: Efforts must continue in this area prior to the use of

**M~** or in the event that

**A}~** additives are not practical . o The FAA should immediately request the NTSB to consider implementing the proposals by the Coordinating Research Council for improved accident reporting relevant to postcrash fuel fires . The Committee notes that the Coordinating Research Council made this recommendation in 1975 in their report No . 

### 482. (See Volume II) . The information obtained would gr eatly assist designers in reducing fire risk.



### 16o Continue and expedite FAA/NASA research to establish realistic airplane crash scenarios with increased emphasis on pos t crash fuel system failure modes and effects on cabin fire safety . o From the crash scenarios , develop fuel system design criteria for transport category aircraft in order to minimize postcrash fuel fires . 

### CABIN INTERIOR MATERIAL o The

**SAFE~** Advisory Committee, in developing the following cabin interior mater ials

**recoc~endations,** took cognizance of the proposed FAA Cabin Fire Safety research plans in terms of technical objectives , funding requirements, and milestones . The plan should develop the technical data base that would supporL rAA's decision on eventual rulemaking , targeted for 1984 , which will lead t o improved human survivability in post crash fires. Several of the following

**reco~mendations** are based on intermediate milestones of the FAA Cabin Fire &aiety kesearch Plan. o Establish the contribution of cabin interior materials to the postcrash fire hazard . The role of current materials, under fire conditions, should be established by mid-1981. o Develop for aircraft seats, fire blocking layers (e.g . , fire barriers) for polyurethane foam cushioning material, in order to retard fire spread . The initial development should be completed by early 1981 . o Expedite the development of the Ohio St

_ ate University (OSU) cham ber and evaluate its use. If successful, this would provide a standardized test for materials which would account for flammability, toxicity, and smoke . The

**Co~ittee** expects that this development could be completed by late 1982, at which time its use should be consider ed for incorporation in FAA's fire airworthiness rules . o Accelerate toxicity research efforts to identify and understand the biological, chemical, and physical factors that must be integrated into comprehensive fire risk assessments for materials in specific end- use configuration . Because of the s ta t e of technology , there is no near - t e rm solution to this

**pr~blem .**  The Committee recommends that , by early 1981 , FAA develop a detailed toxicity research program plan that will provide a basis for eventual regulatory action . o Amend the FAR Part 25, Appendix F, Flammability Test Method for

**~~te ials**  **,** after the American Society for Testing and Haterials (ASTM) has modified test (Bunsen Burner Test ASTM- F7 Method F- 501) to account for the melt and drip- away behavior of certain materials . The FAA should urge the ASTM to expedite this test procedure modification and should complete the incorporation of the Amendment within one year thereaft er . o Define postcrash aircraft fire scenarios and establish their applicability t o fire modeling, research, and design . The

**Co~ittee** recommends that this be accomplished by mid-1981. 

### 17o Continue to expedite and coordinate full-scale fire test pldns . 1\ote : The Co111ml t:tee support::; rt:cent FAA actions to expedite its C-133 full scale fire test program as part of the overall Cabin Fire Sa1ety Plan . The Committee supports the FAA's planned target date of late 1982 for completion of all major aspects of the C-133 program including correlation of small-scale with large- scale tests . o Coord'nare and accele rate aevelopment of analytical postcrash aircr art fire wodeling approach as a means of focusing on those physical fire test and evaluation mc:thod::> most likely to yield practical results in the earliest possible tirae. lSoth small and full-scale test results are required for fire modeling validation . o Based upon the FAA preliminary evaluation of the test procedures and present ma terials tor C:VdCUation slides compl.:>ted in

**~tay** 1980, the Committee

**recomm~nds** that FAA support continued re::;earch and establish radiant

**he<~t** resistance standards

**~nd** criteria cor inflatable evacuation devices at the earliest possible date. o

**Lxp~di e**  the development of improved (ire resi stant cabin windows to protect the cabi1 occupants from I;!Xt<:!rnal fuel fi res. Adaptation of such improved window materials will require further

**s~rvice** environment evaluation prior to aircraft useagL . 1 ) PromotEO open forums, documents and presentations to mak<' the complex subject of toxicology more und<'rstandable to regulatory bodies, flight c rews and the public . o Encourage on a continuing basis the development of a cabin interior material data bank co

**s~rve** as a central information source tor materials characteristics for aircraft de signs . o Support the

**ronti.nu~d** dev12lopment of advanced materials Lo accomplish long-term improvements in alrcraiL cabin fi re safety, including low smoking fire resistant seat foams. OThER AREAS OF CONCER:, The Committee recognized that there were many potentially worthwhile concepts for improving aircraft fi re safety that it simply did not have time to fully address or that were outside the scope of its review. Recommendations relating to such concepts are: o That FAA evaluate the use of self-contained smoke masks, gloves , clothing, or other personal protection equipment for c rewmembers in order that they can better complete emergency evacuation of occupants under the postcrash condition.

**~uch** protective equipment could be helpful in assisting the evacuation of infirm or handicapped persons . o The Committee strongly recommend s that NTSB and FAA jointly improve and standardize postcrash accident investigations with added emphasis on

**id~ntifying** the role of design features and materials that affect the 18development and spread of postcrash fi res . Features that contribute to fire safety as well as those that contribute to fire hazards should be identified . Likewise the precise cause of death and/or injuries in postcrash fire accidents should be determined where practicable. Recognizing that SAFER Committee's efforts are only a beginning in focusing the technical and regulatory attention necessary for rational aircraft fire safety imvrovement , the Committee further recommends that FAA move rapidly to establish a standing technical advisory committee **struc~ure** in the manner of the highly-successful NASA Research and Technology Advisory Committees and the Air Force Scientific Advisory Board. Such a body would provide regular and frequent specialist advice, over the long-term, to the FAA aircraft fire and explosion research program . In particular , the fire safety issues outside the scope of SAFER, or those needing more detailed examination than SAFER could ofier, could be addressed for all aircraft types . This recommendation is consistent with a recommendation expressed by the National Research Council ' s Committee on FAA Airworthiness Certification Procedures on June 26 , 1980.1 AIRCRAFT POST-CRASH FIRE PROBLEM DEFINITION Introduction: lt was determined at the first SAFER meeting : 1. That the Committee would confine itself to transport category airplanes . 2. That, with respect to such airplanes, the Committee would confine itself primarily to the post-crash fire issues discussed at the June 1977 public hearing on fire and explosion hazard reduction and at the November 1977 public hearing on compartment interior materials . 3. That, when considering compartment interior materials issues, the Committee would also consider the matter of carry-on materials (i . e . , baggage, clothes, periodicals , cabin supplies, etc . ) and the fuel fire heat radiation resistance of emergency evacuation slides. 4 . That other issues would be considered only if they are comparably significant and directly related to the post- crash situations . The tirst two of those in particular are important in defining the scope of the Committee ' s activities and are extremely important in defining the

**magni~~de** of the aircraft fire problem.

**Ther~** have been numerous surveys of

**air~lane** accidents, both in the US and world-wide (References 1 to 7) , which

**att~mpt** to put the airplane fire problem in perspective. All of these suffer from a lack of adequate information in one form or another and are thus subject to conjecture and interpretation . variations in the scope and definitions used in compiling the data base lead to further numerical differences, but there is general agreement among the various sources as to the magnitude of the aircraft post crash fire problem. In view of the fact that the basic purpose of the SAFER activity is to support the development of fi re safety regulatory requirements applicable directly to US airplanes and only indirectly to non-US airpl anes , it was expedient to limit the data in this report to the experience of US air carriers. Detailed data can be obtained directly from reports issued by the US National Transportation Safety Board (NTSB) (Ref . 8) which is reponsible for accident investigations of US operators . It is believed this experience is representative of world-wide scheduled air carrier operations . The vast majority of current

**U~** air carrier operations are conducted in turbine powered transport category airplanes and any new regulatory action which may evolve would no doubt be directed first towards that class of airplane. It is, therefore , appropriate to confine the scope of the investigations to that type of airplane . Two accidents to US turbine powered airplanes played important roles in initiating the activity SAFER is concerned with. The first of these was the Pan American 707 at Elkton ,

**~~ryland** in 1963. This was an inflight fuel tankexplosion and, although outside of the scope of SAFER as presently constituted , it led to the establishment of the FAA Advisory Committee on Fuel System Fire Safety and the promulgation of FAA Notice 74-16 on Transport Category Turbine Powered Airplanes Fuel Systems Explosion Prevention. The second accident which triggered interest not only in fuel system safety but in the fire safety of cabin interior materials as well, was the United 727 at Salt Lake City, Utah in 1965 . As the result of each of these accidents, regulatory action was taken by FAA to minimize the potential for recurrence . These changes involved lightning protection, fuel system fire protection and rules on cabin interior materials . These regulatory actions and further proposed rulemaking led to the establishment of SAFER to provide a forum for a comprehensive review of transport aircraft fire safety regulatory requirements. Based on the preceding, it is considered appropriate that any attempt to determine the scope of the airplane post-crash fire problem should not delve into "ancient history" but consider only more recent times. The data which follow are thus confined to post-crash fires involving: 1 . Transport category turbine powered airplanes in US air carrier service. 2. The period 1965-1979 inclusive. 3 . Accidents in which ratalities were attributed to post-crash fires . The Magnitude of the Aircraft Fire Problem As can be seen in figure 1, the safety record of the scheduled airlines is excellent when compared to other

**transpor~** modes . 1979 data are not available for the other transportation modes, however , for the US air carriers there were a total of six fatal accidents in 1979 (including one helicopter accident) of which three involved turbine powered transport category airplanes . The airlines

**fle~** a total of 280 billion passenger miles and the fatality rate was 0 . 115 per hundred million passenger miles . Figure 2 shows the five year average fatality rate per 100 million passenger miles for US certified route air carriers in scheduled domestic and international passenger service for the period 1959 through 1979. In spite of recent dramatic fatal accidents , the trend is still downward . Since we are concerned not only with scheduled passenger service but all operations of US carriers turbine powered airplanes, available NTSB statistical data covering such operations were reviewed . This indicates in the period 1965- 1979 inclusive there were a total of 605 accidents (as classifi ed by NTSB) involving turbine powered transport category airplanes. Of these 605, there were 96 fatal accidents or 16 percent . According to the NTSB r eport shown as Reference 5 , the following post-crash fire accidents accounted for all of the fatalities from fire in US air carrier operations of turbine powered airplanes for the period 1965-1974.

1 . November 8, 1965 2. November 11 , 1965 3 . November 20, 1970 American 727, Cincinnati , Ohio United 727, Salt Lake City, Utah Capital DC-8, Anchorage , Alaska 

### 21

# Safety Comparative Tran spo rt Safety Record Passenger Fatalities per 100 Million Passenger Miles U . S. Scheduled Airlines Domistic Interstate Fataliti es . . ..... . Rate . .. .. .... . . International and Territorial Fat aliti es . Rat e . . .. Total Fatalities . Rate ... Motor Buses Fatalities Rate .. . Railroads Fatalities Rate .. . Autos Fatalities .. . Rate ..... . 

## 1978 1 3 0 .007 

## 0 0 1 3 0 .006 2 .012 13 .017 

## 1977 64 0.038 0 * 0 64 * 0.031 

## 6 0.040 

### 4 .005 29 ,000 * * 28,685 1.6 ** 1 .4

• Does not include 321 passenger fatalities in nonscheduled international service. • • Estimated



## FIGURE 1
22 

## 1968 258 0 .30 47 0.18

305 0.18 31 0 . 16 13 0 . 10 36,500 2 . 3(I) w ...J

**~** .6 a: w (.!) z w (I) .5 (I)

**~** z 0 ...J ...J .4

**~** 0 0 

### .... 

# - (I)
.3 w 1- :i

**~** 1-

**~** u.. a: .2 w (.!) z w (I) (I) . 1

**~** n. 0 59 645 Year Average Fatality Rate/ 100 Million Passenger Miles U.S. Certified Route Air Carriers - Scheduled Domestic and International Passenger Service 1959-1979

69 74 Year 79



### 11Accidents such as Tenerife in 1977 and San Diego in 1978 did not involve scheduled service by U.S . certificated route carriers and are not included in these rates. However, the inclusion of such statistics would not significantly alter the downward trend.



# FIGURE 2 234. December 28 , 1970 5 . June 7, 1971 6 . May 3() ' 1972 7 . December 8 , 1972 8 . **Decemb~r** 20 , 1972 9 . January 3 , 1974 10 . September 11, 1974 Trans Caribbean 727, St . Thomas, Virgin Island Allegheny CV-580 , New Haven, Connecticut Delta DC-9, Fort Worth , Texas Uni t ed 737 , Chicago, Illinois

**~orth** Central DC-9, Chicago, Illinois Pan American 707 , Pago Pago Eastern DC- 9 , Charlotte , North Carolina 

### A revi ew of individual NTSB fatal acciden t reports for the years 1975 through 1979 indica t es that fatalit ies due to tire occurred in the tollowing post- crash fire accidents: ll. April 2 , 1970 12 . **~larch** 27 , 1977 13 . April 4, 1977 14. Narch 1, 1978 15. October 31,

**197~** American 727 , St . Thomas, Virgin I slands Pan American 747 , Teneriffe, Canary Islands Southern DC-9 , New Hope , Georgia Continen t al DC-10 , Los Angeles , California \.-.'es t ern OC-10 , i ·1exico C ity, Nexico There was a fire involved in the

**~estern** DC- 10 at

**~xico** City, however , firm data on whether any fatalities can be at tri buted to fire is unavailable at this time . It is surmised there were ratalities attributable t o fire . Fr om the above, it can be seen that fatal ities w er e attributed to fire in 15 of 96 fatal accidents or about 1 6 percent . ln no case was fire t he cause of the accident but rather the result . With the exception of accident number 15 above, for which final data

**ar~** not yet available, NTSB data shows approximately 1 , )27 persons were on board of which approximately 831 were fatally injured, of these approximately 480 died as a result of the postcrl'lsh fires . Exami nation of the NTSB data shows that during this same period there were several post-crash fire accidents to U . S. turbine powered transport category airplanes which did not re sult in fatalities attributed to fi re . **Ti~e** did not permit

**th ~**  determination of the reasons why no fatalities were attributed to fire in these accidents . Such a study would be useful in defining the e ffectiveness of existing fire safety

**r~quirements .**  While year-co-year variations occur, the average rate of approximately 32 fire deaths per year has been fairly constant despite the great increase in air travel during thi s period. This figure May be compared with the approximate ly 8,000 fire deaths which occur in the United States each year . (Exact comparisons cannot be made owing to varying conditions) . It is of interest to note that during this period (1965-1979) the US air carriers made over 73 million de partures and carried about 3 billion passengers. The vast majority of these operations involved turbine powered airplanes . A revi ew of background data fo r the period 1955- 1964 in Reference 5 indicates there were two post- crash fire accidents to US air carrier turbine

**power~d** transport airplanes in that period where fatalities were attributed to fire. Thus, in about 22 year s of operation of turbine power ed transport category airplanes, there have been approximately 17 post-crash fire accidents where fatalities have been attr ibuted to fire .



### 24While the emphasis in this discussion has been on fatalities, in part because the data on such occurrences are more precise, it is recognized that post-crash fires also frequently cause serious injury to survivors. We believe steps taken to reduce fatalities will also be effective in reducing injuries. Nature of Transport Aircraft Post-Crash Fire Accidents In all accidents listed, the initial fire was a fuel fed fire. Wing separation accompanied by massive fuel spillage occurred in about half the accidents. Fuselage fuel tank or fuel line rupture may contribute to fuel spillage in cases of severe fuselage breakage on impact. Fuel tank explosions occur less frequently but are particularly dangerous because they may terminate evacuation , fire fighting and rescue operations . Moderate fuel spills due to tank or fuel line damage are a less serious threat. It is of interest to note that the United DC-8 accident at Portland, December 28, 1978, also involved severe airplane break-up but the cause of the accident was total fuel exhaustion and there was no accompanying fire . The r ole of cabin interior materials in causing fatalities in a survivable crash fire is difficult to assess. The external fuel fire may penetrate the cabin through an impact created opening, through a door opened for evacuation, or a hot fire may burn through the relatively thin intact fuselage wall . Once the fire has penetrated into the cabin inte rior heat, smoke and toxic combustion products from ignited interior materials will mix with those from the external fire, leading to the rapid development uf untenable conditions . The rate at which the fire grows will depend on the quantity, disposition and flammability properties of the combustible cabin contents, as well as the ventilation of the fire . Tests have shown· that a fire within a typical aircraft cabin can develop untenable conditions in a time comparable to the normal evacuation time. Combustible materials within the aircraft cabin will consist of cabin interior finishes and furnishings, passenger clothing, passenger carry-on items and cabin supplies (Kef. 9, See Volume II) . Furnishings and finishes constitute the largest class of combustibles . Since they meet the requirements of FAR 25.853 they may be slow to ignite but

**~an** burn vigorously when exposed to a sizeable fire. Passenger clothing is present in smaller quantities but is more readily ignited. Carry-on items will usually be of low flammability and will be

**stor~d** under seats and in protected compartments where they are less vulnerable . Cabin supplies are a minor part of the fuel load and are stored in protected compartments. All combustibles may be displaced on impact and thus become more vulnerable to tire . Adequacy of Aircraft Accident Data A sound plan of attack on any safety problem must start with a careful analysis of the accident data in order to pinpoint the true causes of accidents and identify effective r emedies . Otherwise , we may devote large amounts of limited resources to solving the wrong problem.



### 25Aircraft accidents are among the most thoroughly and carefully investigated of all public events . Yet, available aircraft data cannot provide a guide, at this time , to a comprehensive regulatory solution to the aircraft fi re problem. A major effort is made to determine the cause of the crash. This is well done and has rnade an invaluable contribution to the reduction in the frequency of crashes and the number or casualties . SAFER, however, proceeds on the assumption that despite these efforts some crashes will occur . We are concerned with steps that can be taken to reduce the number of casualties in these cases . Much less effort is given to investigating the course of events following the crash than to the events pr eceding the crash . This may be due to the belief that the cause nf the crash is the cause of the casualties and that subsequent events are unimportant . It is probably also an indication that the investigators are not trained in the investigation of fires . The fire may destroy much of the evidence, making it difficult, even for the expert, to determine the course of events. As a first stPp, it is necessary to distlnguislt between casualties due to impact and those who might have survived if they had not subsequently been killed by firP. This js frequently a matter of subjective judgment based on aulopsy data. The investigator is (requently dependent on local medical personnel who are often inexperienced at making such judgments . As a result, we have only rough estimates of the number of fatalities due to fire and of the potential lives that could be saved through improved fi re safety regulations. The time sequence of events is critical to an understanding of the co•:rse of a fatal fire. \ie are concerned with the relative rates of the growth of the fire and the development o1 untenable conditions and with the rate of evacuation, perhaps aided by firefighting and rescue operations . Such information is difficult to obtain, but it is essential if we are to answer such questions as: whRt would be the value of more fire resistant seating materials; what would be the value of added insulation in the cabin wall; what would be the value of intumescent coatings? The exact cause of fi re deaths is difficult to determine in civilian fires (Ref . 1 0) and even more difficult to determine in nircraft fires . The relative importance of high temperatures, smoke obscuration and toxic gas inhalation is unknown. Without information on such questions available, it is not possible to estimate the effectiveness of proposed rules on the flammability , smoke producing potential or toxicity of combustion products of cabin interior materials . Cost

**Effectiven~ss** Economic analyses and cost-benefit studies are required in one form or another by the airframe/airtransport industries and the FAA in evaluating safety as well as other technical improvements . The fact that the next generation transport aircraft will have improved fire resistant materials demonstrates that airframe manufacturers include the safety element in the over all materials selection process. Cost and benefit studies will be required by the FAA to justify improvements to the certification standards whether they be applicable to future designs or newly manufactured or existing aircraft. However, such studies are 

### 26of limited quantitative accuracy and require the extensive employment of subjective judgement. It is important to recognize the current enviable airline safety record and the resultant relatively small number of fatalities . Any safety improvement will be small and incremental but they will save human lives. The resulting economic analyses in themselves may not fully rationalize a "blanket" requirement for safety improvement but may lead to decisions on parts of the solution and identify justified satety improvements. In conducting these analyses, it must be recognized that government and industry resources available for safety are finite and must be very carefully allocated to achieve the greatest benefits. Aircraft Fire Problem Definition The preceding is not an attempt to minimize the airplane fire problem but only to put it into perspective . The ract that post-crash fires have occurred is inescapable . The fact that fatalities due to fire occur relatively infrequently in the overall accident record ls also inescapable. We do not believe this is just l1appenstance but is attributable to the combined efforts of people in government and industry who, working together, have achieved the remarkable safety record ot the

**U~** air carriers . ln considering the total accident history, it is evident that the primary eftort should be expended in accident prevention - that is where the real payoff is in terms of safety and human life . In spite of dedicated etforts, however, it is evident that accidents will continue to occur and there will be

**~ost-crash** fi res. Thus efforts to improve the public ' s chances ot surviving a crasl1 and post-crash fire cannot be ignored and must

**continu~ .**  Now that

**th~** magnitude of the problem has been defined, we believe it appropriate to define the problem in its simplest terms . Recognizing that post- crash fires will occur, we believe the problem before the 

### SAFER Committee is: To determine what improvements can be made in fuel systems and in materials in aircraft cabins which are technologically achievable and economically reasonable and will result in significant improvement in post-crash fire safety. To make this determination, 

### SAFER found it necessary to explore many avenues which are discussed in following sections of this report.

?711

**RAL O~**  **SID TI**  **O~S** 

### OF AIRCRAFT FIRE 

### AND EXPLOSION HAZARDS A commercial jet transport carries large quantities of jet fuel and its cabin is lined and furni s hed wjth polyl'l\eric materials . Passengers and cr ew members occupy a confined environment whe re rapid movement and egress can be diificult . Although the overall safety record is excellent compared to other modes of transporta tion, t he potential dangers ari s ing from aircraft fire are great as e videnced by t he

**on ti**  **nujn~ ,**  ulthough ve ry infrequent, occurrence of fire a ccident s. Tht' prim ary conce rn ot the SAFCR Committee is directed toward minimizing the dangers a&s ocidted with burning fuel, burning cabin materials and tuel t ank

**xpl os**  **ons .** 

**n~ sign**  **Co nstr**  **nt~** The jJr i m clry guide lines coni rvnti llg thE:- airc ra ft designer , aside from tuncti on dre s a t e L y , econcmics,

**se rvi**  **ab llity**  and aesthettcs . C

abin m b t e rial s are

**uc t~d**  irom safety considerations based

**~rimarily** on regulatory flam m

a bility requirements 

### (FAk 25 . 853) and low- smoking tendency O.FPA 258 ) at t he d i sc ro.! tion or the ai r frame manufacturer . In rt:cent years , f

**lar.tr.-~ a**  bili ty pe rtorme1 nce , as indicated by large-scale t e sts or small-scale f lammability tes t s (e . g ., ASTr: 1:.-16 2 , O hio State University test chamber) has had a bea ring on ma t e ri al s<- l ec t ion . H owever, progress 1n the development and selecti on o f impr oved

**~a rials**  i s hand ica pped by the lAck uf test

**mcthod logi~&**  proven to rela t e to cabin f ire hazards, especially in the area of toxicity . C

abin r.ta t e rial!> ar e either sel ec t ed or furnished by the

**airfram~** manufAc tnr·· ··s or ai rlines . ThE' forme r select and ::ahricat e the lining m a tertalc; used i n component s surh as

**si de**  **alls ,**  SLow age bL ns,

**ccilin~s ,**  partitions and structutdl

**floorin ,**  while the latter select and r e place seaLing , tloor covers, and pas s engt: r sevi ce items . G enera lly , the state-of-the- art lining materials (panels ) used by t he maj or airfram e manu facturers are similar in design to one another . The panels are complex

**composit~s** cons isting of a honeycomb core , fiberglass sheet facings, and a thin plastic covering . Replacement of any component because of potential fire performance improvement should be compatible with existing processing equipment and weight allowances if the replacement is to be cost effective. Horeove r, the differential in raw material cost between the new and replaced mater ial must be reasonable. Function , appearance, and serviceability of a new panel de sign cannot be degraded. For these reasons , it is difficult to economically alte r current panel designs. These difficulties are not as pronounced for seating and tloor coverings . Horeover , seating and floor covering materials are replaced more frequently (6-12 months) because of service wear than the paneling (5-10 years) and thus offer greater opportunity for material changes. There have been cases in the past where material changes based on fire pe rformance considerations have caused service problems. For example, fabric of an inherently fire resistant and low- smoking fiber for seat covers and carpets was evaluated in the early wide body jets but exhibited pilling and poor dye retention after service usage. Potential problems of t his 28nature have discouraged the ai r frame manufacturers and airlines from undertaking material changes because of the questionable nature of the re sultant fire safety benefits. Unlike interior materials, safety fuel and fuel tank explosion protection devices have a direct bearing on the safe operation of an airplane. Ideally, safety fuels must be absolutely compatible with existing fuel storage, fuel transfer and propulsion systems. Similarly, fuel tank protection devices cannot be allowed to alter the tuel tank capacity, impose significant weight penalties, or introduce maintenance and inspection problems. Fire Scenarios
- The issue of aircraft fire safety must be analyzed in the context of survivable fire situations. By definition , a survivable accident is an accidental occurrence in which injuries received by passengers or crewmembers, not attributable to the effects of fire, are such that survival of all or most of rhose persons is probable . There are three types of survivable fire situations: the ramp fire, the in-flight fire, and the postcrash fire . Ramp fires have usually involved empty aircraft with no loss ot life, and are not of direct interest to the SAFER Committee, since losses have been entirely economic . Although there are many incidents of in-flight fires , except for two or three cases they have been controlled so that few fatalities have occurred. The overwhelming majority of aircraft fire fatalities occur as the resul t of postcrash fires . In-Flight Fires. This aspect is not part of SAFER's chartered scope , but is treated briefly because it does bear on the basic subject of fire sfety. Aircraft service records and engineering test data substantiate that current aircraft interior materials are adequately resisting the vast majority of in-flight fires to which they are exposed . Thus the current airworthiness rules are believed adequate. Supportive evidence of this is derived in the following typical items treated in these rules. 1. Flame arrestors or fire suppression systems in the wing tip surge tanks provide protection against fuel tank explosions caused by lightning strikes. 2. Accessibility to cargo compartments by crew members has virtually eliminated accidental fires as a serious hazard in such compartments . 3. For inaccessible compartment areas, the fire is successfully controllec by shutting off the normal ventilating air flow and by fire detection and extinguisrunent systems . 4 . Some 92 minor galley fires from 1959 - 1973 have been promptly extinguished with hand-held extinguishers. (Ref. 11 . ) S. Although less frequent, there have been a number of fires believed caused by cigarette ignitions which have also been promptly extinguished. However, there was one instnce of an inflight fire, believed caused by the discarding of a cigarette into a lavatory waste paper towel disposal compartment, which resulted in 124 fatalities . The FAA subsequently issued an Airworthiness Directive to fire-harden the waste paper towel disposal compartments, and later to ban smoking in lavatories. 

### 29The primary concerns o ( an accessible in-flight fire are earl y detection and prowpt extinguishmenL . Since the large mdjority of ignition sources are small, complete extinguishment usually can be effected. Passengers and crewmembers, visually or by smell, can usually detect the presence of a fi re i n its early stages. However, detecti on of a fire docs not always imply knowledge of its exact location to allow for effective extinguishment . There is a possibility, perhaps remote , that the exact location of a fire may remain undetectable for a danger ously long period of time in hidden areas such as behind sidewall paneling or above the drop cei ling. lf an accessible in- tl i ght fi re cannot be extinguished by hand, means must be provided for fire containment until the aircraft can be safely landed . For overwater flights, the time period involved may be several hours . Containment can be accomplished by use of fire barrier materials (e.g., materials which have high char formation charac t eri stics) in the compartment of interest . Resea rch has demonstrated that l avatories constructed of fi re barrie r materials can contain severe ser vice trash. extingui shment considerations fires resulting from burning plastic bags containing passenger By the same token, a lavatory fi re detection and total flooding system would als o be effec tive in this application . Similar exist fo r cargo compartment fi re containment or suppression . Some types of the afor ementioned in-flight fires will be ventilation controlled and thus will unde rgo nonflaming pyrolysis . Just as with flaming combustion, this mode can produce toxic combustion products and dense smoke . Except for a jet transport accident on July 11, 197 3 , ncar Paris, France there is no record of an occurrence of this sort . (Editor ' s No t e : As this report is

**submi ted,**  and additional in-fli ght fire accident occurred in the Midddle East, killing all aboard. Inves tigation is underway at thi s tine .) Pos tcrash Fire - Although postcrash aircraft fires encompass a multiplicity of scenario s , most result initially fr om fuel spillage caused by wing separation, engine separation and/or fuel tank rupture (ref. 12). Occurrence of fuel spillage does not necessarily result i n

**fir~ .**  However, as high velocity air f lows past liquid fuel emerging from l eaking 5tructures during a crash decelerdtion, fuel mist is readily formed . Clouds of fuel mist Qay be highly flammable, even with Lhe fuel temperature well below its flashpoi nt, and may be ignited from hot engine parts, friction sparks, electrical sparks , and hot electric wires . The resulting mi st fireball can then r eadi ly ignite a pool

**~f** released liquid fuel which may continue to burn if most of its surface is ignited . Once this happens, the temperature of the bulk fuel will prog ressively increase as burning continues, resulting in sel f-accele rating intensity of burning . Pool fire heating of intact fuel tanks may result in explosions leading to instantaneous fire intensification . A typical survivable postcrash fire scenario involves exposure of an essentially intact passenger compartment to a large external fuel fire. Crash damage to the cabin in the survivable crash is normally limited to cracks and one or more small , door-sized openings . Although convective and radiative transfer of heat from the fuel fire to the fuselage i s highly dependent on wind dir ection , a fully developed hydrocarbon pool fire can produce heat fluxes as high as 16-1 8 Btu/ft. 2- sec. Thus, cabin interior materials , cargo and passenger baggage


### .30may be subjected Lo rapidly increasing temperatures as well as to open flames penetrating fuselage openings . **Cot~mercial** aircraft contain a variety of organic/polymeric materials capable of both thermal decomposition and flaming combustion. These include urethane foam seat cushioning, various upholstery fabrics, carpeting; blankets; structural and decorative molded plastics; paneling and interior finishing; luggage; clothing materials; and a wide variety of paper products. Although most cabin interior finish materials are flame-resistant when exposed to a small ignition source, upon exposure to a major fire, they can undergo

**ther~al** decomposition and burn . Carry- on items, clothing and paper products are rarely fire-resistant . The major concern in the survivable postcrash fire is the ability of cabin occupants to evacuate rapidly. There are three principal factors preventing escape of occupants from a postcrash aircraft fi re which may be attributable to fire, rather than to the crash itself. These are heat , obscuration of vision due to smoke, and incapacitation due to inhalation of hot, irritant or toxic gases . All these factors will influence escape capabilities in varying degrees , depending on the nature, intensity, and extent of the postcrash fire . Thus, fire dynamics or the rates of development of flames, heat, smoke and hot toxic gases play significant roles in determining escape time. Fire dynamics and the resulting development of hazard depend on many factors , among which are the following: a . Resistance to flame penetration and fire barrier properties cf materials . (Note: Accident experience and large-scale fire tests indicate that the resistance of wide body aircraft to external fuel fire burnthrough is greater than that of the older standard body aircraft . ) b . Physio-chemical properties of materials; e . g., thermal diffusivity, ignition susceptibility, oxygen index, flash fire properties; c. Influences on flame spread rate of materials, including flame height, stoichiometry, buoyancy and entrainment (combustion aerodynamics); d. Heat, smoke, and combustion gas release rate of materials as a function of time and heat flux; e. Location of Qaterials relative to ignition source; f . Geowetry and configuration of flammable materials; g. Area and weight of flammable materials; h. Ventilation rate and direction; i . Radiation exchange; j . Wall and furnishings heat sink properties; and k. Burning ceiling

**drippi~gs** and collapsing ceiling materials possibly igniting seats and carpet or inflicting serious burns on escaping occupants. 

## 31The postcrash fire is an uncontrolled, unsteady-state reaction system characterized by high heat release rates and mass loss rates. Time to reach a hazard condition is a function of the accumulation (fire intensity) rate of the overall system. The time sequence of events from initiation of the fire plays an important role in determing the variation in fire intensity and hence the hazard level. In general, times to reach hazardous or untenable levels are quite short, usually a matter of a few minutes or less. Under the demands of rapid escape from a postcrash fire, the concepts of toxicological and behavioral incapacitation, rather than death, are extremely relevant. Escape from the aircraft in a postcrash fire scenario requires that personnel be neither incapacitated nor disoriented from exposure to toxic and noxious gases over a relatively short time period of 2 to 3 minutes. The current knowledge of smoke toxicity provides little information on the potentially incapacitating effects of smoke inhalation by humans involved in a rapidly developing fire scenario. Although it has been reported that approximately 15 percent of the fatalities in all jet transport accidents are attributable to fire or its effects (ref . 13), it is unclear as to what is the relative importance of burning fuel and burning materials on the ability of cabin occupants to escape. In order to answer this pressing question, full-scale and model experiments are underway using a fire scenario consisting of an intact fuselage with a door-size opening adjacc.lt to a large external fuel fire (ref. 15 and 16). Results obtained with the cabin devoid of interior materials characterize the cabin hazards when the fuel fire is dominant. The following summarizes the outstanding findings: a . Significant stratification of heat , smoke, and combustion gases; (some implications are the obscuration of ceiling mounted emergency lighting and exit signs and more severe heat exposure of materials at or near the ceiling in contrast to those materials located closer to the floor.) b. The overriding importance of wind speed and direction and location of door openings on the rate of cabin hazard development; c. Life threatening temperatures , dense black smoke but innocuous concentrations of carbon monoxide and minimal depletion of oxygen under conditions of penetration by fuel fire; and d. Under quiescent wind conditions, heat flux levels of 14 Btu/ft2-sec at the fire door rapidly dropping off away from the fire (less than 2 Btu/ft2-sec at a distance of about 10 feet). Other factors of undetermined significance are the materials on a fully boarded 270 passenger aircraft indicates that 17-25 percent are materials worn or carried on board by passengers (ref. 9, also see Volume II). Although this figure constitutes a significant percentage , it is unlikely, for several reasons, that these uncontrolled materials constitute a major fire threat on board a wide body jet. Foremost is that placement of passenger carry-on items inside overhead stowage bins, beneath seats, or inside closets makes it unlikely that these materials will experience significant fire involvement compared to regulated furnishing and lining materials. Secondly, because of the natural 

### 32instinct of cabin occupants to move away from fire, it is unlikely that combustion products produced by clothing worn by occupants overcome by and eventually engulfed in fire will affect the ability of any remaining occupants to escape. The contribution to the overall fire hazar d of passenger carry- on and airline-furnished passenger service items placed in open hat racks has not been documented.



### 33Ill FIREWORTHY NATERIALS Present Materials It is important to emphasize that over the years there have been improvements in cabin interior materials, some required by regulation, others incorporated voluntarily by the airframe manufacturers. Older transport airplanes, except the wide bodies, were designed to pre 1967 standards . When FAR Part 25 .853 was first adopted in September 1967, most narrow body airplanes manufactured after that date were manufactured at least to that standard . FAR Part 121 . 312 required that any airplanes not meeting that standard were to be upgraded at the first major cabin overhaul or refurbishmenL . FAR Part 25 . 853 was upgraded in 1972; however, these upgraded requirements had already been applied to the wide bodies voluntarily by the aircraft manufacturers and were reflected in related special conditions by the 

### FAA. Presently all narrow body aircraft meet or exceed the 1967 standards in FAR Part 25 . 853 .

**~ny** meet, partially meet, or exceed the so-called wide body standards of 1972 as now containec in FAR Part 25 . 853 . All wide body airplanes meet or exceed the 1972 standards in FAR Part 25 . 853. The materials used in wide body cabin interiors , based on accident data, are quite flame resistant. Wide-body lavatory configurations can and have contained fires both in test and in real situations; post- crash fires fueled only by the interior materials have not spread through the cabins; likewise there is no recent wide body accident evidence that any person has been adversely affected by smoke and toxic fumes from burning interior materials (See Editor's Note in Part II). Aircraft accident reco rds indicate that present regulations and voluntary upgrading have improved interior materials. This leads to two conclusions. First, current burn and smoke test methods provide the designer with a reasonable guideline for the selection of materials. A major difficulty lies in trying to judge the effectiveness of a particular candidate improvement relative to the overall safety of the aircraft. Current

**re~earch** programs will help to enlighten and resolve this question. Second , a definite improvement in materials has occurred and will continue to occur with each new generation of aircraft. To put the fireworthiness of current aircraft materials in proper perspective, most materials used in homes, offices and contemporary ground transportation vehicles would not be acceptable for use in aircraft despite their low cost and excellent performance characteristics. Acknowledging the Fuel Fire Interior construction materials exhibit substantial resistance to ignition. In a post-crash situation, the fire threat to the aircraft is the engine fuel


### 34that it carries. When fuel is not ignited, post-crash fires of significance do not occur . If fuel fires could be eliminated, further efforts to improve fireworthiness of interior materials would be less important. This has led to

**r~search** and development programs aimed at controlling fuel fires by employing fuel additives and improving the standard integrity of fuel tanks and fuel systems under crash loads. Advanced Haterials when considering material improvements, the severity of the fire threat must be

**tak~n** into account . The threat from interior in-flight fires is much less than from post- crash fuel fi r es. Aircraft service reco rds and engineering test data substantiate that current materials have rl:!sisted the in-flight fires (See [ditor ' s Note in Part Il) . Organic materials carried on- board the aircraft by the passengers are seldom

**flam~** resistant . A naterial which shows promise for itilprovcd fire properties cannot always

**b~** used because of other factors such as

**str~ngth,** cleanability, cost, density, rigidity, produceability , formability ,

**bondi~g** or

**attacl~~nt** characteristics, aging characteristics , thermal properties, sensitivity to solvents, and wear and abrasion characteristics . Incorporation of one new material may require developing an enti re new construction philosophy for the aircratt subsystem on which it will be employed (i.e ., sidewalls, ceiling and/or interior furnishings). In addition , FAA regulatory proceedings can stimulate e:iforts to advance the state-of-the-art . This has been demonstrated by the technical community ' s response to FAA rulemaking proposals with respect Lo the emission of smoke and toxic gases in post- crash fires. Until w e can significantly reduce the likelihood of a fuel-fed fire in a post-crash scenario, the ultimate goal for fire-resistant cabin materials would be to withstand high heat flux levels for extended periods of time . These flux levels can melt the aluminum outer skin of the aircraft, thus exposing the interior insul.ations and sidewalls . Recent accident and test data have

**be~n** shown that current insulation and cabin sidewalls are capable of withstanding burn- through for times commensurate with evacuation . But Eor the long term, materials and materials systems (i.e . ablative and paint systems) should be developed which minimize heat release , smoke production and toxic gas and also provide maximum fire ablation in the presence of the heating rates to which they might be exposed. Laboratory and full- scale tests indtcate that fire containment benefits can be derived from improvements in the fire hardness of transparent window materials . A new fire-resistant NASA-developed epoxy-borazene transparent material has been demonstrated to reduce the hazard of fire penetration resulting from the failure of conventional acrylic window materials . Additional development will be necessary to ready this new mate rial tor production. It will require the further preparation and study of composite transparencies, an improvement in edge attachment technology and a reduction of the material ' s sensitivity to production solvents .



### 35There

**appea~s ~o**  be

**li~tle pros?~C~**  

## G=

**:~~~c~u~i~; ~a::~**  **:a~~:~s :~~**  **ca ~?~:**  ar.d upholstery in the near future . **Alt~oug~ r.!C~e**  ::.a-::e

**::-esis~ ar.**  **~** :ibe::-s

**a~e** available, each has specific

**defi cte**  **~cie s**  **~~i:h :re**  **cl u~e**  use

**i~ ~~is**  application. **:::~** has been
**demons~ratec ::-9ce~:l::**  :ha::

**'..~'":'a~-** :,e

**?Ossi~ie ::**  achiev•.? a

**~t.:du :i**  **on** o:- **eli;.:i:1a~:o~** 

## c:

**:~e :~:-e~~**  **~= :::~**  **s:-~e.aC ~~=-**  **~ug.::~~~** :!.:e aircra:t by using a

**fi re**  **bloc~ing** laye::-

**cc-::=~~si~~** a 

### ti;h- :ha=

**y~e:e** elastomeric foan to protect the ?Olyurethane

**:?a~ i~**  **curre~t** ?assenger

**sea~s .**  This modification oay

**~roduce** a **subs::a~tial** recuctiQn i'

**:ir~ s~r~ari**  combustion ?roducts and would

**pro~ije ~or~**  **t~~e :~**  **~** egress . In summary , improvements withia the s :: ate-of-the- art

**~it~** windows , seats and escape slides that could

**reduc~** the threat to hur.t":ln life ia a post-crash condition are possible in the

**short to-~oderate**  term.

# ) IV TOXICITY AND SHOK.E Identification of the Problem Concerns over the life hazards f rom combustion products (radiant heat, heated atmosphere, oxygen depletion, visual obscuration and toxic components) from cabin interior materials are related to the impact-survivable accident that is accompanied, or immediately followed, by fire. The primary source of this fi re is the residual powerplant fuel that has spilled from one or more fuel tanks as a r esult of mechanical rupture during crash impact. This fire alone may seriously impede, or even prevent, the successful evacuation of individuals who have survived the impact in a functional state; in such cases the properties of interior materials may be of little significance to the overall survival rate. Therefore, it is only for the impact-survivable accident in which the size and intensity of the exterior fuel fire is not immediately life-threatening that the potential effect of interior materials on a successful evacuation is s i gnificant . Of these hazards, there is no general agreement on the approximate magnitude (statistical) of the toxic contribution from burning interior materials, nor even agreement that such a problem exists to any degree-- in the case of an aircraft postcrash fire. Previous attempts to assess the role of interior materials from accident investigation data have led to contradictory conclusions or to the impasse that no conclusion, one way or the other , could be justified. See Attachment in Volume II for an approach to resolving the problem. Reduction of the intensity of the fuel fire by fuel modification and the use of fuel containment systems would also greatly reduce the heat, smoke, and toxic hazard fo r an aircraft postcrash fire . Since this is a scenario in which the time available tor successful evacuation is usually limited to a few minutes , any action that would delay the i.nitiation, or the subsequent rate, of thermal decomposition of a material would obviously extend the escape time available before a toxic incapacitation environment is produced. Therefore, the use of materials with improved flammability and smoke characteristics may also accomplish the added dividend of reducing the toxic hazard for an aircraft postcrash fire. Projected Time Frame Needed to Deal With the Problem The key for resolution of this problem is the development of a valid and practical approach to life hazard evaluation. Work under way to define the toxic potential of cabin materials in a form useful in fire modeling efforts could lead to a valid toxic hazard evaluation technique. Similar efforts are underway in hazard evaluation using room fire and building fire modeling studies. Solution of this problem, if appropriate effort is applied, is about 5 to 10 years away. Work should continue on the definition of the potential of the other life hazards (listed**unde~** identification of the problem) for use in fire modeling. 

### 37Toxicity , Toxic Hazard, and Risk In today's world of sophisticated science, it is unfortunately common for public officials , the information media , and the general public to misunder
stand scientific findings . Historically, this has been the case in the area of toxicology . As a consequence, there is an increasing responsibility for scientists , and in particular for

**to~icologists,** to extend their active involvement into the arenas of public enlightnment and the formulation of laws or regulations that pertain to public health and safety. A prime concern for toxicologists is the apparent contusion that often exists for nonspecialists between the terms "toxicity" and "toxic hazard." Toxicity is a specific property of any , and all , chemical species --or of any more- or- less defined mixture of species . It is expressed as that quantity of the chemical (mixture) just sufficient to bring about some specific, undesireable change in the well-being of a living or ganism, when that chemical is administered over a defined interval of time and under specified condi tions. lt is almost a biological axiom , and one that is not always fully appreciated , that any chemical , natural or synthetic, is potentially toxic; it needs only to be administered in sufficient quantity over a sufficient period oi time and under appropriate circumstances to have detrimental effects on any organism . Some of the various ways in which the toxicity of a specific chemical could be stated are illustrated by the following : (a) 

### An approximate lethal oral dose of hydrogen cyanide (HCN) for a typical male adult human is 100 milligrams . (b) A lethal oral dose of HCN for an average rat is one- thi rd of a milligram , or 330 micrograms . (c) The concentration of carbon monoxide in air that would physically incapacitate a mouse in 5 minutes is approximately 2,000 parts- per- million. So , it is obvious that toxicity is a measure of how much of a substance would be required to produce some specified undesirable effect in a given biological speci es when administered in a particular manner . This brings us t o the concept of toxic hazard , the determination of which is simply an appplied "science" based on the accepted fact that any given chemical is potentially toxic . While this established toxicity is a property of the chemical under specified and controll ed conditions, its t oxic hazard is an evaluation of the degree of harm that could result t o the same organism from an exposure t o the maximum amount of the chemical reasonably expected to be present in some defined , but entirely different , set of circumstances. Normally t his new environment would be some natural setting such as the home, the workplace, a vehicle, etc . Thus an estimate of a toxic hazard is not onl y dependent on the factual knowledge of how toxic a chemical is under standard laboratory conditions , but must also take into account the effects of an entirely new set of environmental condit ions and cir cumstances as well as a probability estimate of how much chemical will he available as a function of the exposure time. 

### 38In a given environment the potential toxicity may not represent a hazard for any of several reasons; the quantity is inadequate; the time interval over which it is acquired is too long; or other existing conditions are sufficiently different from those for which the toxicity was defined that the chemical is prevented from exerting its harmful effect . Indeed , toxic effects result from only an infinitesimally small fraction of the daily encounters between living organisms and toxic agents; otherwise the myriad of chemicals we breathe, ingest , wear, touch , and otherwise immerse ourselves in would have exterminated us long ago! Theoretically, at least , assessment of toxicity for a given pair of chemical and biological species could be performed only once and never need repeating , except possibly for verification of the original results . This assessment would be an activity limited almost exclusively to scientific specialists and conducted in well-equipped laboratories under specifically defined and well-controlled conditions . Hazard assessments, on the other hand, could be required for each separate occasion for which that one chemical could possibly co-exist intimately with a living organism. Thus , toxic hazards are a potential threat in any and all environments , and the decision as to whether or not a hazard does exist is dependent on knowledge of the toxicity of the chemical , the nature of the organism, and the specifics of their mutual environment . The assessment of hazard is also an activity that should be the exclusive responsibility of the scientifically trained experts . The results can be no more meaningful than the scientific knowledge, the expertise, and the practical experience that can be brought to bear on the solution. The following are examples of the types of- excercises in logic that might be undertaken in distinguishing between the toxicity of a material and the potential degree of hazard associated with its use in a certain way in a specific environment. Hydrogen cyanide is a highly- toxic, gaseous chemical, as was noted above. This does not mean, however, that any situation in which a person might inhale some HCN, or ingest one of its solid salts , is automatically a highly hazardous one . The smoke from burning tobacco is known to contain HCN; there fore one might ask if any tobacco-containing products are cyanide hazards. Obviously there could be a host of proper responses to such a question, depending on the remaining, unspecified circumstances. How much of a hazard would a drying shed half-filled with 1000 pounds of tobacco represent? Absolutely no hazard from cyanide -- not as it stands . What are the chances that it could be unintentionally ignited, and what is the cyanide hazard for this new situation? Well, how far reooved are the nearest living organisms of any concern? What is the direction of the wind? Its velocity? Where is the smoke going and how rapidly is it being diluted? What would be the respective hazards for three individuals who enter ed the burning shed to fight the fire -- one breathing through a mask equipped wit h a particle (dust) filter , one wear ing a full-faced , self- contained breathing apparatus, and the third with no respiratory protection at all?
19The above are meant to illustrate mnre explicitly that a determination of hazard level encompasses the concepts of: hazard from what, specifically; under what circumstances ; and in what environment?--one last illustration may help clarify the element: hazard from what? Although the smoking of one cigar would not represent for the smoker, a significantly hazardous exposure to hydrogen cyanide , consider a slightly different question. How much of a hazard to oncoming traffic, at night on a two-lane highway, would you assign to the situation of a car driven by a newly- licensed teenager who had just finished smoking his very first cigar -- inhaling every draw? (For those who ever experienced those dramatic effects of their first cigar , or cigarette, the answer is**sur~ly** obvious.) There is, however , an additional judgraental activity in which the politician, the bureaucrat , the social expert, the economist, and even citizens generally should play an active role. This is the determination, for those areas controlled or regulated by government, of the level at which a predicated degree of hazard no longer represents an "acceptable risk" and becomes an unacceptable one. In reality , the assignment of a degree to a pre-dett:rmineJ hazard level is by far the most difficult and the least objective of the three types of evaluation. Yet, such an evaluation is important. The concept of absolute safety or zero risk is an artifical one And has not been**exp~rienced** by mankind , at least where natural £orces are involved . Horeover, not all situations can i)e rendered absolutory safe at any cost. It is useful to determine whether small-risk levels are achievable and, if so , at what cost, recongnizing that quantifying risks and benefits of pariticular courses is an exact science, although one which can be helpful to policy-makers in the exercise of**~1eir** judgement . Inhalation Toxicity Testing (1) Background . Over the years, a more-or-less standardized technique has evolved for evaluating the toxicity of a given agent . Under defined and repeatable conditions , a known weight or volume of the solid or liquid test substance is administered to an animal of known weight . The selected route of admi nistration can be one of several choices : (a) Oral (b) Parenteral (by injection or topically) (c) Inhalation Administration by the selected route will be repeated in a number of animals all at the same dose level, i . e. , quantity of substance per unit of body weight. Additional groups of animals will be given successively higher dose levels and then all will be observed for a prescribed period of time. From the observed responses to the different treatment levels a dose-response curve can be constructed. This curve, or plot, will reflect the percentage of each test group of**ani~ als**  that gave the required response when administered each of the dose levels . From such a plot can be derived an estimate of the quantity of toxic agent that produced the observed response in one-half of the tested subjects. This quantity is commonly called**~he** "effective dose for 50-percent response," or 

## EDso· 40 

## IAn i•"p0rtant requirement for determination of an EDso is knowledge of the**o•1~~t;ty ~nrl** **;~~ntity** of the toxic agent that the test subject received. This i.t; 'JC'l L')n r!.tff.ir.nlt to accomplish for a toxic substance that is either a &0].;d "t l iq·1irl, and that can be administered by one of the usual routes. But**C0~~·oe~ ~h~**  c?se of a gaseous agent that is acquired by inhalation. 

### A dH :ferPnt sl'!t 

### ot criteria must be formulated for this special situation, for obvjv•1sly oPe cannot administer a fixed, known amount of a gas to each subject . Of these**r~ e~**  of administration, inhalation effects are of primary concern**-~~** post-crash fires. The usual procedure in inhalation toxicology is to**e&~ab~ish** a knnMn concentration of the test agent in air and introduce the**tes ~** **2~ ~~ls**  into this atmosphere for a specified time interval. Repeated exposures of additional groups at different concentrations , but for the same**t~~e perio~,**  will supply the data for relating the percent of each exposed population that exhibits the desired response to that exposure concentration. Thus we obtain, not an effective dose, but an effective concentration for 50 percent response-- an ECso• In this case, however , we also must specify the duration of the exposure; therefore, if exposure were for 60 minutes we would obt::>in a "60-minute ECso·" It sho•lld be**imml'!di~** tely evident that the values for an ECso will change

- - t-l-."! dtl""ati 0n of the exposure changes . The atmospheric concentration**o11i.~e.-l** 'f' l(jll"' rat in a 5-minute exposure must surely be greater than that nr '"! rl"cl to r:i

_ ll. in 3n 0r 60 minutes . Thus the value of ECso is normally**'rv~· ~")y** **rpl~~ed** to the duration of the exposure, but not necessarily**.;11ver~~ly** propnrt:!on-"'l to it . f/) !Jf::e nf animals vs chemical analysis. Chemical analysis of · onb..**ct<~** or-**.::tt""'>~phere:::** iR an integral part of toxicity tesing and subsequent**~-"'~ard** an::>lysi::: . H0wever, analytical**proc~dures** should be used to enhance the V"'lllo of**~nirn<>l .**  d-"'t<>**r~th.:>r** than in lieu of animal data. l>.f" f'l' rnm,.,nnly**'1F~d ~n::>**  lyti**r.~** 1 procerlnres allow for identification and 1'""nl i_f.i.c-.::ttioTJ of frnm one to several of the principal off-gases that are g""':"!'"At<>rl**~**..ring cnTTJbllstion or pyrolysis of a material. In no case however ,

---**~ c"-~tc~{nn** **•tmo~phe e** **h~** completely characterized both qualitatively and**q··?~tit::>t-iuo~y .**  Tnvir.ity, in inhalation testing , is a function of exposure t-i-e**~~.-l cnn~nTJtr~tion** **~p~** iR**~anifest** in the whole animal. For atmospheres nf ci_nQ.lt', rnre gAses, toxicity may be predicted on the basis of analytical**~Rt ?**  once the toxicity of the pure gas has been determined. For atmosphere •."'l:::p:r:! ...**.,~** nf t•: 7" £P<="'\S, toxicity can often be predicted if the toxicity of r- - ' l-**.;..,~i vi~·!P~** **.** g:;!<= ;

_ ., knf"·'n**a~** a function of time and concentration. For**~~~~~r~~,.-o~ r.nn** **~ining hre~**  or m0re principal gases toxicity can rarely be**~~o,H t-~ti-**  0 V"'T\ .if t.h<>.**to~i city**  of all the principal gases is known. Since ,.. __.....,..";,._,.,**"'~""'"'=rh~r<><=** "'=''-"'lly consist of many components, identification and**'}'! ...,** t- .• 40i ""' t . ; ""! i**~** a l;:thoriouf: ancl costly procedure. By inhalation toxicology,**·:-•~o ~~** **;~ ~J~** **, ""** **~ ~RP**  evaluate the combined toxic properties of the entire -:**~**.. · :'. "'**,~~ ~ot-~rmin~** **•h~! her**  further component identification effort is

.; ::.-?T"'torl ..



## 41(3) Extrapolation of animal data t o humans . Animal toxicity data are almost always used as the basis for establishing safe exposure concentrations for humans . Quite obviously though , there are cases in which animal data are not predictive for the human. In general, it is safe to state that extrapolation of acute-lethal animal toxicity data is more reliable than is extrapolation of chronic effects data--even though there will be differences in susceptibility--or tolerance--among various species. Since exposure of humans to combustion/pyrolysis atmospheres is principally an acute situation, it should be reasonable to extrapolate actual animal results to the human s ituation, provided the appropriate scaling factors are utilized. Incapacitation vs Mortality as a Response Criterion The impact-survivable, postcrash aircraft fire presents a unique environment t o the surviving

**pas~engers** and crew who are attempting to evacuate to safer surroundings . ln most suclt accidents the time available for successful evacuat i on is in the range of possibly 2 to 5 minutes depending on the

**int~nsity** of the fuel fire . Even for accidents that occur on or near airports, this time is usually too brief tor crash rescue per sonnel to arrive at the scene and physically remove any individuals from inside the aircraft . Historical revi ew of these accidents also reveals that rarely is a passenger able to physically remove a fellow passenger who cannot, or will not, leave the aircraft on his own. Consequently , it appears that a passenger who does not get himself out , does not get out . The relevant toxicological question then becomes one of what physiological condition for a passenger most closely describes the loss of his ability to e xit the aircraft under his own power. Any incapacitation due to physical or

**m~chanical** trauma will not be considered since we are concerned in this instance with only those individuals who survive the impact in a functional stat e and are then rendered nonfunctional by exposure of toxic gases . Incapacitation could also result from the heat stress, loss of vision due to smoke , or sheer panic , as well as from toxicological effects. lt is surely obvious that at some physiologically-impaired state, short of death, a person would be physically incapacitated . An unconscious person would certainly

**b~** incapacitated; on the other hand, one might be still conscious and yet bl:! unable to muster the psychomotor coordination necessary to escape . Therefore, as was first proposed by CMli scientists, the desired e ndpoint for an anirnal toxicity test that would relate to loss of escape potential from a burning aircraft should measure the earliest occurrence of physical incapacitation . Further research is in progress to determine the most suitable methodology for measuring this incapacitation . There is an additional concept that is worth discussing . Interest in the toxicity of the combustion products present during evacuation is primarily a question of the relative toxic threat. Whatever the toxic threat from materials in current use, could that threat be justifiably reduced by substituting other materials? Therefore, we are interested in comparing the

1 .?relative toxic threat among two or more materials that could be used for the same pur pose . Fur thermore, this toxic thr eat should be in terms of t he t i me available for successful escape. So, we are really interested in measuring the relative times- to-incapacitation that result from exposure to smoKe from these materials . I t is obvious t hat for any toxic gas the lethal exposure time will be longer than the incapacitating exposure time , and as a consequence any relative mortality data might not properly reflect the relative times available fo r escape. The Relevance of Laboratory Test Results to Cabin Fires . Toxic hazard , as was discussed in an earlier sec t ion , is an evaluation that can be made only after some type of specific , quantitative toxicity information is available . In tlte context of combustion product toxicity , however, there are some unique difficulties in attempting to predict toxic hazard for a real fire environment , even from known toxicity measurements on the same materials, if those measurements were made with a small- scale test system. The type of information that one needs, in order to reduce the toxic element of the fire hazard from cabin interior materials , is whether or not there are differences among the toxic hazards of candidate materials for a given application , struc t ure or use . Several techniques are available for generating this information from small-scale laboratory tests . In a closed system of known volume (or a flowthrough system of known flow rate) one could determine the wei ght of each material that would have to be burned for . the resultant smoke to incapacitate one-half of the animals in 10 minutes (a 10-minute 

## EDso .

**wher ~**  D is "dose" and is synonymous with o,.1eight of material) . Alternatively one could

**ex~erimentally** define time to incapacitation as a function of weight of burned material. We would then know which of the three materials pr oduced t he most-t oxic smoke and which the least- toxic, but how do we relate these results to the real cabin fires? These values are only toxicity measurements , and we have already discussed the problems associated with converting trom toxicity data to toxic-hazard evaluations . Unfortunately, t here are even mor e probl ems than j ust t hose associat ed with these conver sions . Even if all parameters ot her than toxicity were assumed to be constant in the cabin fire , for each of the materials , we still might not be able to effect a reliable conversion for the following reason . If the composition of the toxic components in the smoke from the cabi n fire were the same as in the laboratory test smoke , then obviously knowl edge concerning one could be used to predic t effect s of the ot her . In reality , this is very unlikely to be the case .

I")Investigations with small-bcale tests have shown that the composition, and thus the toxicity, of the smoke from many thermally- decomposing materials is very sensitive to the test conditions . Two parameters that seem most influential are the environmental temperature, or the heat flux, at which the decomposition is effected , and the ventilation rate relative to the decomposition rate of the material . One obvious physical manifestation of the effect of these two parameters is whether a material decomposes with or without flaming. The resul tant combustion products, and therefore the toxicity , can vary with these parameters to the extent that under one set of conditions it is highly toxic and under another set is almost nontoxic . This potential lack of identity , or conformance , between the test combustion products and the cabin fire combustion products is a well-recognized problem, and one which sci entists have made several suggestions for solving . The most r ealistic and meaningful way is to measur e the toxic effects from larse-scale fires . However, this approach is the most expensive and, therefore , limited in use. Another possible approach is to "burn" the test material in small- scale tests under exactly the same thermal and ventilation conditions as would be found in the real fire . Unfortunately, there is no single real fi re; all fires are extremely variable, not onlj from fire to fire, but even within the time course of a single fire . One could probably observe the

**~ntire** spectrum of all possible conditions botlt among several fires and even within any specific fire . Some engineers

**hav~** suggested that a "standard fi re" simply be defined arbitrarily, then smo.ll-scale test conditions could be assigned fixed values based on that standard; others , however , have been

**r~luctant** to accept this approach for fear that material regulation based on such a philosophy could as eas ily increase the cabin fire toxic hazard as decrease it . A third approach utilizes the concept of a "wors t-case condition . " If the toxicity of smoke fro1n a given material can vary as a function of "how it is burned , " then obviously some one set of conditions will produce the mosttoxic smoke possible. The real fi re 111ay also, at some time, expose the materi al to this worst-case set of conditions . Therefore , the specific toxicity for each material, that would be util i zed for extrapolation to i t s potential toxic hazard in a fire , would be the maximum toxicity obtainable for t hat material by varying the conditions in the small- scale test over the range that could be expected in a real fire . The wor st case in specific toxicity , however, does not necessarily represent the worst case in toxic hazard . There has been no mutual agreement , to date, as to which approach, if any , could be utilized as a basis for material regul ation , but , no matter what technique might eventually be approved , there is an impor tant point that needs to be reemphasized . Materials should never be regul ated sol ely on the basis of the specific toxicity of their thermal decomposition products , but according to their toxic hazard , which includes ot her material property vari ables and specific use conditions in t he air craft cabin.**T~ere** is one additional controversy that is pertinent to this discussion . :-J .....ql._! t be toxic hazards for competing materials be expressed in absolute or re 1 ative terms? Would it be sufficient to know that material C has three tjmes the toxic hazard of material A, and that A has twice the toxic hazard of 

### B? Or must one be able to say that, as they are used in the cabin , 

### B would allow 12 minutes for escape before the average passenger would become i nc:apar.itated, while A would allow 6 minutes and C only 2 minutes? These are very different questions and the research required to obt ain the respective types of data is also quite different. The decision must be made, however, before the experimental research is designed. Visual Obscuration Due to Smoke In addition to the toxic effects of inhaled combustion products , there is another oroperty that can increase the evacuation time from a cabin. This is the visual impairment produced by the irritant properties of the smoke and the decreased transmission of light through the smoky atmosphere . Any increase in the**tim~?.** required for evacuation prolongs**tht.~** exposure to heat and toxic gases and therefore reduces the likelihood of escape .**Dect"t!a~ed** visual effectiveness can obscure aisles , exits , exit lights (partir.ularly those in the upper portion of the cabin), obstructions (such as rli&placed carry-on items, service items, cabin structures , or even bodies); c:.tn**p~oduced** disorientation sufficient to cause passengers to go in the wrong**dire~tion** or open the wrong exit; and could even induce panic in some .indjvid11als (Ref. 20).**4J~hough sue~**  etfects frmn smoke are obvious and would logically affect evacuation time , a dependable**corr~lati.on** between quantity (density and nature) of smoke and its quantitative effect on evacuation time has not been established experimentally. Such experiments are in**progr~ss ,**  however, and hP.tter information should become availahle--subject, or course, to the hazard limits that control the design of any research that utilizes human subjects .



### 45