US Deportment 

of Transportation 

Federal Aviation 

Administration 

Office of Aviation Safety 

Washington, D.C. 20591 

g; oo3! 

f-0 &'ltif 

LU:l\ f\r r-~ro' /' - 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. Enctc rs (ChairMan), E. C. \~oo<1 (Executive Dir.} 

9. P~rformin g Orgonizotoon Nome ond Address 10. Work Unot No. (TRAIS) 

SAFER Advisory Co~mittee 11 . Contract or Gront No. 

t-:":::--:-----------,..,-----------------11 ~. Ty[f oR Report tnd Period Covered 

12. Seonsoring Agency Nome ond Add oess 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 

1 S. 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 mited amount of ti "le available, tre Committee confined its examination to large 

transport catego ry aircraft, reasoning that recomme ndations develooed could provide 

the necec;sary g11idance for the FAA to address the broader spectrum of airplane and 

rot orcraft fire safety improvemP. 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 thes E:' topics \'Jere f elt 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 

surporti ng 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 gh t Fire 

SAFER 

Cabin Materials 

Fire Safetv 

Occupcnt Survival 

18. Distri bution 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 

Unc l ass i fi ed Unclassified 82 

Form DOT F 1700.7 (8-72> Reproduction 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)-3 
PREFACE 

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 aircra ft 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 r eport is a sum~ation of a year-long study of the problem by 

the Committee and supporting gr oups. 

The r eport 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 fe r 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 first, in June , considerec fire and 

explosion hazard r eduction. The second, in tJovembe r, dealt with the 

fireworthiness of compa r tment interior materials. 

As a consequence of the information developed at those hearings, the FAA 

conclud ed 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 aircraft r elating 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. 

1 
Furthermore, 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 inte r ests. Airlines , canufacturers, universities, public and pr ivate 

sector research establishments, flight and cabin crews, and consumer 

organization representation 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 r esea r ch 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 Na t ional 

Aviation Facilities Experimental Center (NAFEC* ) to establish the pr ocedures by 

which the speciality groups would convene and interact in order to respond to 

the Administrator's charge to the Committee . r~ny small meetings of the 

specialists followed in July , August, and September. The Technical Gr oups 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 t he 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 dra ft 

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 Coomi t t ee 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 

Na tiona! 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 

4 
C. 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. r ec 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 - [nginee ring 

National Aeronautics and Space 

Administration 

Transport Aircraft Office 
Technical Group on Compartment Interior Naterials 

H. L \vilfert, Group Leader 

S. Davis, Deputy Group Leader 

R. Allen 

B. R. Aubin 

r. . Ba ra 

H. eraoting 

R. Bricker 

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 Engineer/Scientist 

National Bureau of Standards 

Cente r 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:!de ral 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 

De 1 ta Airlines 

Vice President - Engineering 

Celenese Fibers Marketing Co. 

t1anager - Cornnerc ial Developnen t 

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 · Experi1nental Center 

National ~eronautics and Space 

Administration 

Project Manager, Composite Structures 

Ibuglas Aircraft Company 

Director, ~~terials & Process Engineering 
J . 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. 

Hater ials & 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 Service 
Post- 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-Califor nia 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-Cali fornia Co. 

SafE:ty Engineer 

British Embassy 

Civil Air Attache - Safety 

Uniroyal, Inc. 

Chiet Engineer, Fuel Cells 

Fe nwal, 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 Safety 
J • T. Leonard 

A. T. lDthrigel (Al ternatt:) 

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 Power plant 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 

Power plant Engineering 

TJ. s . Army Research & Technology Labs 

Aer-ospace Engineer 

Gates r~arjet Corp. Chief of Powerplants 

United Technol ogies Cbrp. 

Sikorsky Aircraft Di vision 

Federal Av iation ~ministra ion 

Project Engineer, National Av iation 

Facili t 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 . 

Manager, 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 Engineering 
SUNNARY 

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 

assignmen t, certain topics that wer e 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 request 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 

discussions 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 f i 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\'e r a!;e ahout 32 per year . In 

addition, occupants have bee~ se riously 1njured in survivable accidents 

where postcrash fir es 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 tt ec, in-flight cabin fires 

leading to fatalities were round tu be rare events . lxcept for three 

non-U . S. accidents, all i n-ilight Cdhi n fires have been controlled by means 

o f des.ign , tire txti"'t:uit-:hi-lb equi'Jra,n t and crew training. (See Parts I, II, 

\' and VII) 

o Tht availabl€ dcH a bac:.~ 01. ;ti rt r a lire accidents and incidents is 

inadequate t ( determinl~, 1-1tl ~.-or.liaLnc ... , the c rit ical chain of events 

in many air.::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 1111, 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 compa rt::d with those used prior 

to the FAA' s 19i 2 revtsL)T1 <'f 'rcr.JI.t i nterio r material flammability 

standard~ . The Comrll•.::t· r-ot••"' :.1:11 nt'''• improved Clate rials a!ld 

designs, exceed in~ th~~ ·~ r c•_.j r•"t.~ :1:.~ . . are o(ter. incorporattd into 

aircraft cabin in t<J r iors a~ :rHy b~"rOmt! a\-ailable . (See Part I and lll 

There is a lack of universall y accepted tes t methodology that will 

reliably predicl large seal~ tire Lenavior of materials based on small 

scale te5ts . (See ParL 1.) 

Current burn and smoke test me thod s provide the designer with a 

guideline for selecting mat e rials on a comparat ive basis. Since these 

methods do not permit the assessment of the effect of a given oater ial 

on the overall cabin rire sa fe ty level, furthe r study of this area is 

needed. (See Parts 11, III a nd IV) 

o Cabin interior panels and insulati on ~ith improved fire resistance are coming 

into production. This develo pment promises to improve resistance against 

penetrat ion of an external fi re into the cabin. Improved tire resistant 

windows and cabin wall insulation mate rials 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 

uncon trolled source c f tl .. · fur a pc•sL - cra5h f ire, that may add to the 

cabin int e rio r f1re . (~t:e h• l<> lJ a ,•d Ill) 

13 
o t\ear-term improvements in cabin fire safety can only be accomplished by 

new designs employing currently-available materials. The work on 

fir~-blocking 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 greatest 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 ava ilable vent f ire suppression systems, 

when extended to comple t 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 

resis tent tuel cells . Current FAR's do not preclude incorporation oi 

such design feotures. (See Pa rt V) 

o Toxici t y t est standards do not exist for aircrait fire 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 fue l or 

other fire r elated haza rds . (See Part IV) 

o There is incomplete data on the haza rds 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 we ll done toxicity resea rch projec ts have been ca rried 

out, there has been no substantial effort devoted t o understanding the 

overall toxic threat envir onment in aircraft f ire situations. (See 

Part IV) 

o Reduction of the potential toxic threa t 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 

anima ls cannot be recommended at this time. (See Part IV) 

For the purpose of mate rial selection , assessment of relative toxicity, 

solely f r om 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 budge tary needs, aircraft fi r e 

research has , with the exception of toxic hazards assessment, been 

r easonably well funded since the early- to mid-1970 ' s. Improvements 

expected within t he next year or s o are products of research begun in 

that period. (See Pa rt 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 requir e 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 us e 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 

Coor dinating Research Council made this recommendation in 1975 in their 

report No . 482. (See Volume II) . The information obtained would g r eatly 

assist designers in reducing fire risk. 

16 
o Continue and expedite FAA/NASA research to establish realistic airplane 

crash scenarios with increased emphasis on post crash fuel system failure 

modes and effects on cabin fire safety . 

o From the crash scenarios , develop fuel system design criter ia 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 

mate r ials recoc~endations, took cognizance of the proposed FAA Cabin Fire 

Safety research plans in terms of technical objectives, funding r equirements, 

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) chamber 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 

configu ration. Because of the st a t e of technology , there is no near - t e rm 

solution to this pr~blem . The Committee recommends that , by ea rly 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 yea r thereaft e r . 

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. 

17 
o 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 r esults are required for fire 

modeling validation . 

o Based upon the FAA preliminary evaluation of the test procedures and present 

ma t erials 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 resistant cabin windows to protect 

the cabi1 occupan ts from I;!Xt<:!rnal fuel fi res. Adaptation of such improved 

window materials will require further s~rvice e nvironment evaluation prior to 

aircraft useagL . 

1) Promo tEO 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 r e 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 postcr ash 

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 

18 
development 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, t o 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 a t 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 othe r 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 ca rrier 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 tank 
explosion 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 Tu r bine 

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 pr oposed 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 Transport Safety Record 

Passenger Fatalities per 1 00 Million 

Passenger Miles 

U.S. Scheduled Airlines 

Domistic Interstate 

Fatalities . . ..... . 

Rate . .. .. .... . . 

International and Territorial 

Fat alities . 

Rat e . . .. 

Total 

Fatalities . 

Rate ... 

Motor Buses 

Fatalities 

Rate .. . 

Railroads 

Fatalities 

Rate .. . 

Autos 

Fatalities .. . 

Rate ..... . 

1978 

13 

0 .007 

0 

0 

13 

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) 

(I) .5 

~ 

z 

0 

...J 

...J .4 ~ 

0 

0 

.... 

-(I) 

w .3 

1-

:i 

~ 

1-

~ 

u.. 

a: .2 

w 

(.!) 

z 

w 

(I) 

(I) .1 ~ 

n. 

0 

59 64 

5 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 

11 Accidents 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 

23 
4. December 28 , 1970 

5 . June 7, 1971 

6 . May 3() ' 1972 

7. December 8 , 1972 

8 . Decemb~r 20 , 1972 

9 . Janua r y 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 r eports for the years 1975 through 

1979 indica t es that fatalit ies due to tire occurred in the tollowing post- c rash 

fire accidents: 

ll. April 2 , 1970 

12 . ~larch 27 , 1977 

13 . April 4, 1977 

14. Narch 1, 1978 

15. October 31, 197~ 

Ame rican 727 , St . Thomas, Virgin Islands 

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 City, 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 t his 

time . It is surmised there wer e ratalities a ttributable t o fire . 

Fr om the above, it can be seen that fatalities we r e attributed to fire in 15 of 

96 fatal accidents or about 16 pe r cent . ln no case was fire t he cause of the 

accident but rather the result . With the exception of accident numbe r 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 fa tally injured, of these 

approximately 480 died as a r esult of the postcrl'lsh fires. 

Exami nation of the NTSB data shows tha t during this same period there were 

several post-cr ash fire accidents to U. S. turbine powered transport category 

airplanes which did not r e sult in fatalities attributed to fi re . Ti~e did not 

permit th ~ determination of the reasons why no fatalities were attributed to 

fir e 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 r ate of approximately 32 fire deaths per yea r has 

been f airly constant despite the great increase in air travel during this 

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 pa rtures and carried about 3 billion passenge rs. 

The vast majority of these operations involved turbine powered airplanes. A 

revi ew of background data fo r the pe riod 1955- 1964 in Reference 5 indicates 

there were two post- crash fire a ccidents to US air ca rrier turbine power~d 

transport airplanes in that period where fatalities were attributed to fire. 

Thus, in about 22 yea rs of operation of turbine powe r ed transport category 

airplanes, there have been approximately 17 post-crash fire accidents where 

fatalities have been attr ibuted to fire . 

24 
While 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 f ire 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. Othe rwis e , we may devote large amounts of limited 

resources to solving the wrong problem. 

25 
Aircraft 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 r e 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 t he 

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 r e deaths is difficult to determine in civilian fires 

(Ref . 10) 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 ove r all mate rials 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 

26 
of 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 s urviving 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. 

?7 
11 

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 furnis hed wjth polyl'l\ eric materials. Passengers and c r ew members 

occupy a confined environment whe r e rapid movement and egress can be diificult . 

Althoug h the overall safety r e cord is excellent compared to other modes of 

transporta tion, t he potential da ngers arising from aircraft fire are great as 

e videnced by t he on ti nujn~ , ulthoug h ve r y infrequent, occurrenc e of fire 

a cciden t s. Th t' primary conce rn ot the SAFCR Committee is directed toward 

minimizing the da ngers a&s ocidt ed with burning fuel, burning cabin materials and 

tuel t ank xpl os ons . 

n~ sign Co nstr nt~ 

The jJ r i mcl ry guide lines coni rvntillg thE:- airc ra f t designer , aside from 

tuncti on dre s a t e Ly , econcmics, se rvi ab llity and aesthettcs. 

Ca bin mb t e rials are uc t~d irom safety considerations based ~rimarily on 

r egulat or y flamma bility requireme nts (FAk 25 . 853) and low- smoking tendency 

O.FPA 258 ) at t he d isc r o.! tion or the a i r f r ame manuf acturer. 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 , Ohio State University test chamber) has 

had a bea ring on ma t e rial s<- l ec t ion . Howeve r, prog ress 1n the developme nt 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 haz ards, especially in the area of toxicity . 

Cabin r.ta t e rial!> a r e eithe r sel ec t ed or furnished by the airfram~ manufAc t nr·· ··s 

o r airlines. ThE' f o rme r select and ::ahrica t e the lining ma terta lc; used i n 

components surh as si de alls , SL owage bL ns, ccilin~s , partitions a nd structutdl 

floorin , while the latte r select and r e place seaLing , tloor covers, and 

pass engt: r sevi ce items . Genera lly , the state-of-the- art lining materials 

(panels) used by t he major airframe manu facturers are similar in design to one 

another. The pane ls are complex composit~s cons isting of a honeycomb core , 

fiberglass sheet facings, and a thin plastic covering . Replacement of any 

compone nt because of potential fire performance improvement should be compatible 

with existing processing equipme nt and weight allowances if the replacement is 

to be cost effective. Horeove r, the differential in raw material cost between 

the new and replaced mate r 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 mate rial 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 

28 
nature have discouraged the air frame manufacturers and airlines from undertaking material changes because of the questionable nature of the resultant fire safety 

benefits. 

Unlike interior materials, safety fuel and fuel tank explosion protection 

devices have a direct bearing on the safe ope ration 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 ana lyzed 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 f ire suppression systems in the wing tip surge tanks 

provide protection against fuel tank explosions caused by lightning strikes. 

2. Accessibility to cargo compa rtments 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 f rom 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. 

29 
The primary concerns o ( an accessible in-flight fire are earl y detection and 

prowpt extinguishme nL . Since t he large md jority 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 r e 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 ceiling. 

lf an accessible in- tli ght fi re cannot be extinguished by hand, means must be 

provided for fire containment until the aircr aft can be safely landed . For 

overwater flights, the time period involved may be several hours. Containmen t 

can be accomplished by use of f ire barrier materials (e.g., materials which have 

high char formation charac t e ristics) in the compartment of interest . Resea r ch 

has demonstrated that l avatories constructed of fi re barrie r materials can 

contain severe 

ser vice trash. 

extinguishment 

considerations 

fires resulting from burning plastic bags containing passenge r 

By the same token, a lavatory fi re detection and total flooding 

system would also be effec tive in this application . Similar 

exist fo r ca r go compartment fi r e containment or suppression. 

Some types of the afor ementioned in-flight fires will be ventilation controlled 

and thus will unde r go no nflaming pyrolysis . Just as with flaming combustion, 

this mode can produce toxic combustion products and dens e smoke . Except for a 

jet transport accident on July 11, 1973, ncar Paris, France there is no record 

of an occurrence of this sort . (Editor' s No t e : As this r eport is submi ted, 

a nd additional in-fli ght fire accident occurred in the Midddle East, killing all 

aboa rd. Investigation is underwa y at this tine .) 

Postcrash Fire - Although postcrash aircraft fires encompass a multiplicity of 

scenarios , most result initially f r 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~ . 

Howeve r, as high ve locity air f lows past liquid fuel emerging from l eaking 

5tructures during a crash decelerdtion, fuel mist is readily formed . Clouds of 

f uel mist Qay be highly flammable, even with Lhe fuel temperature well below its 

flashpoi nt, and may be ignited from hot engine pa rts, friction sparks, 

electrical sparks, and hot electric wires . The resulting mist fireball can t hen 

r eadily ignite a pool ~f released liquid fuel which may continue to burn if most 

of its surface is ignited . Onc e 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 exte rnal 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 hea t 

from the fuel fire to the f uselage is highly dependent on wind dir ection , a 

fully developed hydrocarbon pool fire can produce heat fluxes as high as 16-18 

Btu/ft. 2- sec. Thus, cabin interior materials , cargo and passenger baggage 

.30 
may 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 fire 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. 

31 
The 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 

32 
instinct 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. 

33 
Ill 

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 

refu rbishmenL. 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 ref lected 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 

34 
that 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 f rom interior in-flight fires is much less 

than from post- crash fuel fir 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 entir e 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 demonst rated 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 we 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 pr esence 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. 

35 
There 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 

fire 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 si 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. 

37 
Toxicity , 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 misunderstand scientific findings . Historically, this has been the case in the area 

of toxicology . As a consequence, the re 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 ove r 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 appropr iate 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 o f hydrogen cyanide (HCN) for a 

typical male adult human is 100 milligrams. 

(b) A lethal oral dose of HCN for an ave r age 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 r equired 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 hazar d is 

an evaluation of the degree of harm that could r esult 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 entir ely differ ent , set of circumstances. 

Normally t his new envir onment 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 

entir ely new set of envir onmental 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. 

38 
In 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. 

Haza rd 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- exce rcises 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 wea r ing a full-faced , self- contained breathing 

apparatus, and the third with no respiratory protection at all? 

19 
The 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 r eality , 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 

I 
An 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 

obvj v•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-. • 40 i ""' 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 f urther 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 

extra polation 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 

situation, 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 usua lly too brief tor c rash rescue pe r 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 t o 

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 

sta t 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 

dea th, 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 compa ring 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 a r e 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 Fir es. 

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 the r e are 

differences among the toxic hazards of candidate materials fo r 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 we i 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 a r e even mor e probl ems than 

j ust t hose associat ed with these conve rsions. Even if all pa r amete rs ot he r 

than toxicity were assumed to be constant in the cabin f ire , 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 f r om 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 he r . In r eality , 

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 mate r ial decomposes with or without flaming. The resul t ant 

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. 

Anothe r 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 r e; all fires are 

extremely variable, not onlj from fire to fire, but e ven 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 r e" simply be defined 

arbitrarily, then smo.ll-scale test conditions could be assigned fixed values 

based on that standard; others, howeve r , 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 "worst-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 r e 111ay also, at some time, expose the 

materi al to this worst-case set of conditions. Therefor e , the specific 

toxicity for each material, that would be utili 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 

t hat could be expected in a real fire . The wo rst case in specific toxicity, 

however, does not necessarily r epr esent 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 matte r 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 mate r ial 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 

re1 ative terms? Would it be sufficient to know that mate rial 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.ita ted, 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