September 20, 2000

Wednesday,

September 20, 2000

Part II

Department ofTransportationFederal Aviation Administration

14 CFR Part 25, et al.Improved Flammability Standards forThermal/Acoustic Insulation MaterialsUsed in Transport Category Airplanes;Proposed Rule

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56992 Federal Register / Vol. 65, No. 183 / Wednesday, September 20, 2000 / Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Parts 25, 91, 121, 125, and 135

[Docket No. FAA–2000–7909; Notice No. 00–09]

RIN 2120–AG91

Improved Flammability Standards forThermal/Acoustic Insulation MaterialsUsed in Transport Category Airplanes

AGENCY: Federal AviationAdministration (FAA), DOT.ACTION: Notice of proposed rulemaking(NPRM).

SUMMARY: This document proposesupgraded flammability standards forthermal/acoustic insulation materialstypically installed behind interiorpanels in transport category airplanes,by adopting new flammability testmethods and criteria that specificallyaddress flame propagation and entry ofan external fire into the airplane(burnthrough) under realistic firescenarios. This proposed rule change isconsidered necessary because thecurrent standards do not realisticallyaddress situations in which thermal/acoustic insulation materials maycontribute to the propagation of a fire.The proposed standards are intended toreduce the incidence and severity ofcabin fires, particularly those ignited ininaccessible areas where thermal/acoustic insulation materials aretypically installed. In addition, theseproposed standards are also intended toprovide an increased level of safety withrespect to post-crash fires by delayingthe entry of such a fire into the cabin,thereby providing additional time forevacuation and enhancing survivability.These new standards, in addition tobeing proposed for new type designs,are also proposed for newlymanufactured airplanes entering part121 service. Additionally, the proposedflame propagation standards are alsoproposed for newly manufacturedairplanes entering parts 91, 125, and 135service.DATES: Comments must be received onor before January 18, 2001.ADDRESSES: Comments on thisdocument should be mailed ordelivered, in duplicate, to: U.S.Department of Transportation Dockets,Docket No. FAA–2000–7909, 400Seventh Street SW., Room Plaza 401,Washington, DC 20590. Comments alsomay be sent electronically to thefollowing Internet address: [email protected]. Comments may be filedand examined in Room Plaza 401

between 10 a.m. and 5 p.m. weekdays,except Federal holidays, In addition, theFAA is maintaining an informationdocket of comments in the TransportAirplane Directorate (ANM–100),Federal Aviation Administration,Northwest Mountain Region, 1601 LindAvenue SW., Renton, WA 98055–4056.Comments in the information docketmay be examined between 7:30 a.m. and4 p.m. weekdays, except Federalholidays.

FOR FURTHER INFORMATION CONTACT: JeffGardlin, FAA Airframe and Cabin SafetyBranch, ANM–115, Transport AirplaneDirectorate, Aircraft CertificationService, 1601 Lind Avenue SW.,Renton, Washington 98055–4056;telephone (425) 227–2136, facsimile(425) 227–1149, e-mail:[email protected].

SUPPLEMENTARY INFORMATION:

Comments InvitedInterested persons are invited to

participate in the making of theproposed action by submitting suchwritten data, views, or arguments asthey may desire. Comments relating tothe environmental, energy, federalism,or economic impact that might resultfrom adopting the proposals in thisdocument are also invited. Substantivecomments should be accompanied bycost estimates. Comments must identifythe regulatory docket or notice numberand be submitted in duplicate to theDOT Rules Docket address specifiedabove.

All comments received, as well as areport summarizing each substantivepublic contact with FAA personnelconcerning this proposed rulemaking,will be filed in the docket. The docketis available for public inspection beforeand after the comment closing date.

All comments received on or beforethe closing date will be considered bythe Administrator before taking actionon this proposed rulemaking. Commentsfiled late will be considered as far aspossible without incurring expense ordelay. The proposals in this documentmay be changed in light of thecomments received.

Commenters wishing the FAA toacknowledge receipt of their commentssubmitted in response to this documentmust include a pre-addressed, stampedpostcard with those comments on whichthe following statement is made:‘‘Comments to Docket No. FAA–2000–7909.’’ The postcard will be datestamped and mailed to the commenter.

Availability of NPRMs

An electronic copy of this documentmay be downloaded using a modem and

suitable communications software fromthe FAA regulations section of theFedworld electronic bulletin boardservice (telephone: 703–321–3339), orthe Government Printing Office’s (GPO)electronic bulletin board service(telephone: 202–512–1661).

Internet users may reach the FAA’sweb page at http://www.faa.gov/avr/arm/nprm/nprm.htm or the GPO’s webpage at http://www.access.gpo.gov/narafor access to recently publishedrulemaking documents.

Any person may obtain a copy of thisdocument by submitting a request to theFederal Aviation Administration, Officeof Rulemaking, ARM–1, 800Independence Avenue, SW.,Washington, DC 20591, or by calling(202) 267–9680. Communications mustidentify the notice number or docketnumber of this NPRM.

Persons interested in being placed onthe mailing list for future rulemakingdocuments should request from theabove office a copy of Advisory CircularNo. 11–2A, Notice of ProposedRulemaking Distribution System, whichdescribes the application procedure.

BackgroundInsulation is installed, typically

behind airplane interior panels, in orderto protect the occupants, cargo, andequipment of an airplane from thermaland acoustic extremes associated withenvironmental conditions and enginenoise sources. This insulation istypically located in the passenger orcargo compartments of an airplane,although it may be located in any othercompartment where insulation may bedesired.

Insulation is usually constructed inthe form of what is commonly referredto as a ‘‘blanket.’’ These insulationblankets are typically composed of: (1)A batting, of a material genericallyreferred to as fiberglass (or glass fiber, orglass wool, with Owens Corning’sFiberglas being one example); and (2)a film covering to contain the battingand to resist moisture penetration,usually metalized or non-metalizedpolyethylene terephthalate (PET), withDuPont’s Mylar being one example, ormetalized polyvinyl fluoride (PVF),with DuPont’s Tedlar being oneexample. Another type of film, used oncertain specific airplanes, is polyimide.It should be noted that, irrespective ofthe type of film, there are variationsassociated with its assembly formanufacture that result in differences inperformance from a fire safetystandpoint. These variations include thedensity of the film, the type andfineness of the scrim bonded to the film,and the adhesive used to bond the scrim


56993Federal Register / Vol. 65, No. 183 / Wednesday, September 20, 2000 / Proposed Rules

to the film. The scrim is usuallyconstructed of either nylon or polyesterand is bonded to the backside of thefilm to add shape and strength to thesurface area. The scrim resembles ascreen, and the mesh can vary infineness. The type of adhesive used tobond the scrim to the film also varies.Adhesive is frequently the repository ofany fire retardant in the assembledsheet.

Current Regulations Pertinent toThermal/Acoustic Insulation Materials

The current regulations pertaining tothermal/acoustic insulation addressneither the thermal nor acousticperformance aspects, but rather thematerials’ tendency to propagate flame.The intent of the requirement is toensure that insulation materials do notrepresent a significant fuel source in theevent of a fire, or provide a medium fora fire to spread inside the airplane. Theexisting FAA regulations have focusedon ensuring that insulation blanketscomply with the basic ‘‘Bunsen burner’’flammability requirements describedbelow.

In addition to performing theiroriginally intended functions, thermal/acoustic blankets have also been shownto delay what is termed fuselageburnthrough. (Fuselage burnthroughrefers to the penetration of a post-crashexternal fire through the fuselage skinand insulation into an interiorcompartment.) This delay ofburnthrough serves to increase the timeavailable for occupants to evacuate anairplane. However, this valuableattribute, which is believed to be acharacteristic inherent to some degree inall existing insulation blankets, has notbeen addressed or required in theregulations.

The FAA has adopted a number ofregulations that address flammabilityconcerns on airplanes. The currentflammability requirements pertinent todiscussions in this notice are as follows:

Section 25.853(a), ‘‘Compartmentinteriors,’’ requires that materials incompartments occupied by crew orpassengers must meet the applicable testcriteria of part I of appendix F to 14 CFRpart 25.

Section 25.855(d), ‘‘Cargo or baggagecompartments,’’ requires that for cargoand baggage compartments not occupiedby crew or passengers, materials used inthe construction of said compartmentsmust meet the applicable test criteria ofpart I of appendix F to part 25.

The applicable test criteria referencedin the requirements listed above aredefined in paragraph (a)(1)(ii) of part Iof appendix F to part 25, and prescribethat insulation materials must be self-

extinguishing after having beensubjected to the flame of a Bunsenburner for 12 seconds, in accordancewith the procedures defined inparagraph (b)(4) of part I of appendix F.The average burn length may not exceed8 inches, and the average flame timeafter removal of the flame source maynot exceed 15 seconds. Drippings fromthe test specimen may not continue toflame for more than an average of 5seconds after falling. These criteria wereadopted in 1972 and are those in usetoday. The purpose of these test criteriais to ensure that materials be self-extinguishing when exposed to likelyignition sources under actualconditions. Based on the service recordat the time these criteria were adopted,these criteria appeared to provide thelevel of protection intended.

Section 91.613, ‘‘Materials forcompartment interiors,’’ requires thatairplanes certificated in accordancewith SFAR No. 41, with a maximumcertificated takeoff weight in excess of12,500 pounds, comply within 1 year ofissuance of the airworthiness certificatewith the requirements of §§ 25.853(a),(b), (b–1), (b–2), and (b–3), in effect onSeptember 26, 1978.

Section 121.312(c), ‘‘All interiormaterials, airplanes type certificated inaccordance with SFAR No. 41 of 14 CFRpart 21,’’ requires that affected airplaneswith a maximum certificated takeoffweight in excess of 12,500 pounds musthave interior materials that comply with§ 25.853(a), in effect on March 6, 1995(formerly § 25.853(a), (b), (b–1), (b–2),and (b–3) in effect on September 26,1978). Section 121.312(d), ‘‘All interiormaterials; other airplanes,’’ requires thatmaterials must comply with theapplicable requirements under whichthe airplane was type certificated.

Section 125.113(a)(1) & (2), ‘‘Cabininteriors,’’ requires that upon the firstmajor overhaul of an airplane cabin orrefurbishing of the cabin interior, allmaterials in each compartment used bythe crew or passengers that do not meetthe following requirements must bereplaced with materials that meet theserequirements: § 25.853 in effect on April30, 1972, for airplanes for which thetype certificate application was filedprior to May 1, 1972; and the materialsrequirement under which the airplanewas type certificated for airplanes forwhich the type certificate applicationwas filed on or after May 1, 1972.

Section 135.170, ‘‘Materials forcompartment interiors,’’ specificallyapplies to airplanes that conform to anamended or supplemental typecertificate issued in accordance withSFAR No. 41 for a maximum certificatedtakeoff weight in excess of 12,500

pounds. Paragraph (a) of this sectionrequires that, one year after issuance ofthe initial airworthiness certificateissued in accordance with SFAR No. 41,the airplane must meet the compartmentinterior requirements set forth in§ 25.853(a) in effect on March 6, 1995[formerly § 25.853(a), (b), (b–1), (b–2),and (b–3) in effect on September 26,1978]. This section also requires certainadditional airworthiness requirementsconcerning the use of particularmaterials for various cabin interiorcomponents on airplanes other thancommuter category airplanes andairplanes certificated under SFAR No.41.

Incidents Involving InsulationMaterials

The FAA is aware of at least sixevents in which the flammabilitycharacteristics of thermal/acousticinsulation material may have been acontributing factor. In November of1993, a fire occurred in a McDonnellDouglas MD–87 airplane while it wastaxiing in from a landing atCopenhagen, Denmark. The fire wasfound to have been initiated by anelectrical fault behind a sidewall, butinvestigators later determined that theinsulation materials contributed to thepropagation of the fire. In November of1995, a cabin fire occurred in aMcDonnell Douglas MD–82 airplaneprior to takeoff at Turin, Italy. The causeof the fire was attributed to a rupturedlighting ballast. In that case, otherinterior materials played a moresignificant role in propagating the fire,but there was evidence that the fire alsopropagated on the film of the insulation.

In June of 1996, the FAA received aletter from the Civil Aviation Authorityof China (CAAC), which described threeincidents of interior fires that occurredin China in 1994 and 1995. Thoseincidents involved McDonnell Douglasand Boeing airplanes and were causedby electrical problems or inappropriatemaintenance actions. In each of thosecases, physical damage to the airplanewas minimal, but there was clearevidence that the fires had propagatedon the insulation.

The FAA had been doing research todevelop a new standard and had issuedseveral reports on evaluations of testmethods. The FAA initiatedinvestigations and research, describedlater in this notice, to determine theappropriateness of applying existingBunsen burner flammability criteria tothermal/acoustic insulation, as typicallyinstalled in concealed and inaccessibleareas, and to develop more suitablecriteria if considered necessary.



On September 2, 1998, an MD–11airplane experienced a catastrophicaccident as the result of an inflight fire.Although the cause of the accident hasnot been determined, the FAA considersthat it is likely that the fire spread onthe thermal/acoustic insulation, and haspublished proposed airworthinessdirectives to address the affectedmaterial (64 FR 43966, August 12,1999). Those airworthiness directivesare applicable to certain model DC–9–80(MD–80), MD–90, DC–10–30/30F, andMD–11/11F airplanes and requireremoval of the worst performingmaterial (metalized Mylar).

Fire Safety Research—GeneralThe FAA has adopted an aggressive

program to improve airplane fire safety.As a result, stringent new test methodswere adopted that significantlyupgraded the flammability standards forairplane materials associated with seatcushions, large interior panels, cargocompartment liners, and fire detectionand suppression equipment for themajority of cargo compartments in thefleet. In order to maximize the safetybenefit, the most significant areas wereaddressed first, with subsequentrulemaking addressing additional areasaccording to their relative priority in firesafety.

Those improvements addressed whatthe FAA considered to be the mostsignificant areas of airplane interiors,from a flammability standpoint, andprovided improved design requirementsfor new airplanes, as well as upgradedrequirements for the existing fleet. All ofthese improvements were supported byresearch conducted, for the most part, atthe FAA William J. Hughes TechnicalCenter.

Fire Safety Research—Thermal/Acoustic Insulation Materials

As an initial response to the incidentsdescribed above, the FAA conducted areview of both the part 25, appendix F,required test method, and a test methodused by certain segments of the industryto assess the flammability of thermal/acoustic insulation. That test methodinvolves the use of alcohol-soakedcotton swabs that are ignited and thenplaced on a 16- × 24-inch sample ofinsulation material. Tests utilizing thismethod were conducted at the FAATechnical Center in 1997, and at othertest facilities around the world. (Ref.FAA Report DOT/FAA/AR–97/58,‘‘Evaluation of Fire Test Methods forAircraft Thermal Acoustical Insulation,’’dated September 1997, a copy of whichis available in the docket for thisrulemaking.) This multi-facility testprogram showed that the ‘‘cotton-swab’’

test did provide better discriminationamong materials than did the existingBunsen burner certification test method.

During 1997 and 1998, the AerospaceIndustries Association (AIA) conductedadditional testing at the FAA TechnicalCenter, using a full-scale fuselage framesection. The purpose of these tests wasto determine whether the cotton-swabtest method was an adequatecertification test method. The results ofthese tests showed that there werematerials that could pass the cotton-swab test but would still propagate aflame in a large-scale environment. Inaddition, because the ignition sourceused was limited to a large cotton swab,the test did not simulate other sourcesof ignition, specifically any otherburning material or electrical arcing.Based on these results, the FAAconcluded that there was no effectivetest method that represented materialbehavior under full-scale testconditions. It was determined that anew test method was required.

Thermal/acoustic insulation impactsfire safety in two ways. First, due to itsconcealed location behind interiorpanels, if not sufficiently fire resistant itcan provide a path for undetected firepropagation. As noted earlier, thecurrent certification test requires thatthese materials be self-extinguishingafter exposure to a Bunsen burner flame.Second, the insulation blankets canprovide protection against fuselageburnthrough.

The FAA has been studying fuselageburnthrough since the late 1980’s andhas determined that by improvingthermal/acoustic insulation, the timebefore an external fire penetrates thefuselage can be extended. Inconjunction with the Civil AviationAuthority (CAA) of the United Kingdom(UK), and the Direction Generale del’Aviation Civile (DGAC) of France,research was undertaken to assess thecurrent capability of airplane fuselagesto resist burnthrough from an externalfuel fire. That research demonstrated theimportance of thermal/acousticinsulation in the burnthrough processand is documented in the followingreports: ‘‘Fuselage Burnthrough fromLarge Exterior Fuel Fires,’’ FederalAviation Administration final reportDOT/FAA/CT–90/10, July 1994; ‘‘Full-Scale Test Evaluation of Aircraft FuelFire Burnthrough ResistanceImprovements,’’ Federal AviationAdministration report DOT/FAA/AR–98/52, January 1999; and ‘‘BurnthroughResistance of Fuselages: FurtherInvestigation,’’ CAA Paper 95003, CivilAviation Authority, London 1995. (Acopy of each report is in the docket forthis rulemaking.) Findings as a result of

that research indicate that withoutmaking any other change to theairplane, improved thermal/acousticinsulation can delay the entry of a post-crash fuel fire by several minutes, thusprolonging the time available for escape.Conversely, the absence of thermal/acoustic insulation can allow earlierentry of a fire into the airplane.Although there are other factors thataffect fuselage burnthrough (e.g.,fuselage skin and floor panelcharacteristics, ventilation systems,etc.), research demonstrated that thesimplest and most effective approach toimproving burnthrough resistance wasto improve the fire resistance of theinsulation.

In the course of carrying out thisresearch, a medium-scale test methodthat could be correlated with full-scaletesting was developed in the UK. Thistest method was valuable in reducingthe number of full-scale tests required toestablish baseline data, but the size andcomplexity of the apparatus made itimpractical for regulatory purposes.Consequently, smaller-scale testing,using a modified apparatus of the typecurrently used for certification testing ofseat cushions and cargo compartmentliners, was developed in France. Thiswork was coordinated with theInternational Aircraft Materials Fire TestWorking Group (IAMFTWG). TheIAMFTWG consists of experts in thematerials and fire testing specialtieswho help refine and support thedevelopment of test methods used inaviation, and includes representativesfrom the airlines, airframemanufacturers, material suppliers, andregulatory authorities, among others. Arepresentative from the FAA TechnicalCenter chairs this group. The IAMFTWGis a participative technical peer groupthat contributes to FAA research, but itsactivities are not regulatory in nature.

In July of 1997, the FAA determinedthat the separate investigative work onburnthrough and on flame propagationshould be combined, with the aim ofproducing a single test method. Thereason for this decision was tomaximize the benefit from anyrequirements that resulted from the testmethod. However, during the testdevelopment period, it became clearthat a single test was not practical. Thisis because the two phenomena aredistinctly different, and performance inone area does not predict performancein the other. Therefore, the FAA hasdeveloped two tests, which arediscussed below. (These tests aredocumented in draft FAA Report DOT/FAA/AR–99/44, ‘‘Development ofImproved Flammability Criteria forAircraft Thermal/Acoustic Insulation,’’



a copy of which will be placed in thedocket when finalized. Additionally,Internet users may access the FAATechnical Center’s web page at http://www.fire.tc.faa.gov for additionalresearch relating to the test methods.)

Flame PropagationIn order to address the issue of fire

propagation, the FAA conducted aseries of small, medium, and full-scaletests with various insulation materials.These tests identified variouscharacteristics of these materials thatwere significant as to whether or not thematerials would spread a fire from anotherwise small ignition source. Inparticular, the FAA found that a pilotedcontrolled ignition under conditions ofradiant heat tends to predict thematerials’ performance in a full-scalefire. The influence of thesecharacteristics is further dependent onthe fire threat, and much of the FAA’swork was aimed at identifying a realisticthreat.

In conducting small-scale tests, theFAA found that many of the materialscurrently used tend to shrink or, insome cases, melt away from a flamefaster than the flame can propagate onthe material. That is, the mechanicalproperties of the material tend todominate its combustion properties.However, the FAA also found that thesame materials could behave differentlyif they were pre-heated, such as mightoccur in a confined space. In that case,some materials that self-extinguishwhen tested as a small test specimen atroom temperature exhibit flamepropagation tendencies that suggest thepotential to grow into a large fire. Thesize of the ignition source and degree towhich heat can be trapped determinewhether the material will exhibit thisbehavior. If the ignition source is largeenough, and the space confined, evenhighly fire-resistant materials willpropagate a fire. However, confinedspaces and potential ignition sources ofvarying sizes exist throughout theairplane.

The FAA has adapted AmericanSociety of Testing and Materials(ASTM) test method E 648, which usesa modest ignition source combined withexposure to radiant heat, to determinefire propagation performance. This testwas developed to qualify flooring, butlends itself very effectively to insulationmaterials. (A copy of the ASTM testmethod is in the public docket for thisrulemaking.) The FAA has developed acalibration method that will imposerepresentative heat flux, as derived fromfull-scale tests, on the insulationmaterials. This test is considered torepresent a realistic fire threat, and at

the same time imposes reasonablesuccess criteria, considering the state-of-the-art of insulation materials. The testsconducted by the FAA to qualify thisstandard indicate that some of thematerials currently used will pass thenew standard. This method is describedin detail in proposed part VI toappendix F of part 25.

BurnthroughThis test method involves use of a

kerosene burner apparatus, modifiedslightly from its configuration as used inother certification testing, thatrealistically simulates the thermalcharacteristics of a post-crash fire. Thetest stand and specimen are configuredto simulate a small section of fuselageframes and stringers, with insulationmaterial mounted over them. Fuselageskin is not represented in this test, sincethe delay in burnthrough afforded bythe skin is not directly related to theperformance of the insulation. The testis intended to measure the performanceof the insulation itself. This test methodis described in detail in proposed partVII to appendix F of part 25.

Discussion of the ProposalBoth service history and laboratory

testing demonstrate that the currentflammability requirements applicable tothermal/acoustic insulation materialsmay not be providing the intendedprotection against the spread of fires.Additionally, the FAA considers thatincreased protection against externalfire penetrating the fuselage can beprovided by proper selection of thesame material. The FAA considers thatthe new test methods described earlierwould not only provide for increased in-flight fire safety, by reducing theflammability of thermal/acousticinsulation blankets, but would alsoprovide increased time for evacuationduring externally fed, post-crash fires byincreasing fuselage burnthroughresistance. The FAA therefore proposesto amend the current regulations asfollows:

Proposed Part 25 RequirementsThe FAA proposes to adopt the new

test methods described earlier as newpart VI and part VII requirements toappendix F. One aspect of the proposedrequirements is a test to measure thepropensity of the insulation to spread afire. This test method is specified inproposed part VI to appendix F. Thesecond aspect of the proposal is a testto measure the fire penetrationresistance of the insulation, and isspecified in proposed part VII toappendix F. The proposed requirementsare new flammability test standards that

would be applied to thermal/acousticinsulation in lieu of the currentstandard.

In addition, in view of the fact thatcurrent flammability requirements focusalmost exclusively on materials locatedin occupied compartments (§ 25.853)and cargo compartments (§ 25.855), thisproposal includes the adoption of a new§ 25.856, which would address thermal/acoustic insulation materials whereverinstalled. This aspect of the proposalrecognizes the role that thermal/acousticinsulation in other areas may have ineither flame propagation and/or fuselageburnthrough protection, and wouldsubject the thermal/acoustic materials inthose compartments to the proposedflammability standards.

In accordance with § 21.17, these newstandards would apply to new typecertificates for which application ismade after the effective date of the finalrule.

Flame PropagationThe FAA proposes a new standard to

address flame propagation of thermal/acoustic insulation, regardless of whereit is installed in the airplane. Thecurrent flammability requirements focusalmost exclusively on materials locatedin occupied compartments (§ 25.853)and cargo compartments (§ 25.855).However, the FAA considers that thepotential for an inflight fire is notlimited to those specific compartments.Thermal/acoustic insulation is installedthroughout the airplane in other areas,such as electrical/electronic (E/E)compartments or surrounding air ducts,where there is the potential for materialsto spread a fire as well. By applying thestandards only to certain compartments,the intended safety benefit would not berealized for materials installed in otherareas of the airplane. The proposalwould therefore account for insulationinstalled in areas such as equipmentbays and wrapped around ducts thatmight not otherwise be consideredwithin a specific compartment. Theflame propagation provisions of thisproposal would apply to all transportcategory airplanes, regardless of size orpassenger capacity, since theconsequences of an inflight fire are notrelated to those factors.

BurnthroughLower Half: The FAA has considered

whether to make the burnthroughrequirement applicable to only certainareas of the fuselage; that is, those areasconsidered to be most susceptible topenetration by an external fire. Thelower portion of the fuselage is the mostsusceptible to burnthrough from anexternal fuel fire because flames from



such a fire would typically impinge onthe fuselage from below. Therefore, thelower portion would derive the mostbenefit from enhanced burnthroughprotection. Although the additionalcosts associated with providing thissame protection to the remainder of theairplane are not great, the benefitswould be negligible. Therefore, theproposed requirement for burnthroughprotection would apply only toinsulation materials installed in thelower half of the fuselage. It should benoted that the ‘‘lower half’’ is above thecabin floor for most airplanes. Thispoint was chosen based on full-scale firetest data, as documented in thepreviously referenced reports, and thepotential for the airplane to be off itslanding gear. That is, in conditions oflanding gear collapse, the airplane canroll significantly and the area mostsusceptible to burnthrough can becorrespondingly higher on the fuselagethan when the airplane is on its gear. Byproviding burnthrough protection forthe lower half of the fuselage, thissituation is also accounted for.

Applicability: The FAA considers thatthe requirement for burnthroughprotection should be made applicableonly to airplanes with a passengercapacity of 20 or greater. This effectivelyexcludes the smaller transport categoryairplanes, as well as airplanes operatingin an all-cargo mode. The primaryreason for this is that airplanes withsmall passenger capacities are notexpected to realize a significant benefitfrom enhanced burnthrough protectionowing to their very rapid evacuationcapability; that is, they have a favorableexit-to-passenger ratio. Since it isexpected that enhanced burnthroughprotection will impose additional cost,there must be a commensurate benefit tojustify such a proposal. The FAA doesnot consider that such benefits aresubstantial for airplanes with lowpassenger capacities. The specificdiscriminant of 20 passengers waschosen to be consistent with otheroccupant safety regulations, such asthose for interior materials and cabinaisle width. The FAA considers that theevacuation capability of airplanes with20 or more passengers, regardless of theexit arrangement, could be improved byenhanced burnthrough protection. TheFAA invites comments on this aspect ofthe proposal.

Installation Details: For new designs,the proposed new burnthrough testmethod would apply to the insulation asinstalled on the airplane. Thus,consistent with similar flammabilitytesting of other installed materials, themeans intended to be used for fasteningthe insulation to the fuselage would

have to be accounted for whenperforming tests. For consistency, thetest method would impose a standardmethodology for fastening. In additionto this proposal, the FAA is developingadvisory material concerning theinstallation of insulation that wouldenable the installer to avoid a specifictest on the fasteners, etc. Althoughfailures of fasteners or seams during thistest may not exacerbate flamepropagation characteristics, suchfailures could adversely affect theburnthrough protection capability.Since research has shown practicalfastening means are available forensuring that the insulation materialremains in place, it is proposed thatfastening means be considered fornewly manufactured airplanes.

Fuselage Burnthrough Alternative:This proposed rule would establish astandard for thermal/acoustic insulationthat addresses that material’s ability toresist penetration of an external flame,rather than a rule for fuselageburnthrough per se. This distinction isimportant, since fuselage burnthrough isa complex process, dependent on manyvariables. For example, the ability of thefuselage to resist penetration from anexternal fuel fire is directly related tothe thickness and material of the skin.Skin thickness varies considerably, andessentially means that each airplanetype has different burnthroughresistance. In addition, factors internalto the airplane can also affectpenetration of an external fire into theoccupied areas. For example,differences in the air return grills caninfluence the time required for anexternal fire to penetrate the occupiedarea. Therefore, establishing a minimumstandard for fuselage burnthroughresistance and identifying possiblemeans of compliance would be a highlycomplex undertaking.

This notice proposes a simplestandard that has been shown toincrease the time it takes for a fire topenetrate the airplane beyond whatcurrently exists, regardless of thespecific capability that currently exists.Since this increase in time can beachieved by addressing thermal/acoustic insulation material, and sincethis proposal would revise the standardfor insulation to address flamepropagation anyway, it is in the publicinterest to incorporate criteria thatenhance the overall level of safety andthat can be achieved with reasonablecost. Therefore, the standards proposedin this notice address two aspects of firesafety related to insulation material.

Although this proposal does notrequire that insulation be installed, itwould enhance the overall level of

safety of the airplane when insulation isinstalled. Because of the need to providea suitable thermal and acousticalenvironment inside the airplane, theFAA considers it extremely unlikelythat insulation would be removed as ameans to avoid compliance with thisrule. In fact, the removal of insulationmaterial was considered as an option toaddress the flame propagation issues,but was rejected since it wouldeffectively diminish the burnthroughcapability that currently exists. Shouldremoval of insulation become a commonpractice, the FAA will revisit the needfor a specific fuselage burnthroughstandard.

Equivalency (Applies to BothBurnthrough and Flame Propagation)

The proposed changes to appendix Finclude a provision for FAA-approvedequivalent methods. This provision,which is included in other parts ofappendix F, is intended to allow for theincorporation of improvements to thetest methods as they are identified,without requiring specific findings ofequivalent level of safety under 14 CFR21.21. Experience has shown that suchimprovements frequently originate withthe IAMFTWG and are readily adoptedby the industry. It should be noted thatthe proposed standards of appendix Fconstitute the basic requirement, andthat such equivalent methods that mightbe developed would have to be adoptedin total. It would not be acceptable toselectively adopt portions of a modifiedtest method that has been found to beequivalent and not all of the modifiedmethod. The determination of anacceptable equivalent method would bemade by the FAA.

Proposed Operating RequirementsIn addition to changing the design

standards for future type certificateapplications, the FAA considers that thebenefits from improved flammabilitystandards can be realized for existingdesigns, as well. The technology existstoday so that these benefits can beobtained in a cost effective manner byapplying the standards under somecircumstances to newly manufacturedairplanes and to existing airplanes wheninsulating materials are replaced. TheFAA’s means for obtaining benefitsearlier than would be provided bychanging design standards is to revisethe operating rules. Requirements fornewly manufactured airplanes become abasic airworthiness requirement forthose airplanes and apply throughouttheir service life. Requirementsproposed for the existing fleet relate tomaterials that are replaced in service.This latter aspect of the proposal would



not affect newly manufacturedairplanes, since they would already berequired to comply by virtue of theirdate of manufacture.

Flame PropagationNew Production: The FAA proposes

that newly manufactured airplanesentering the fleet in parts 91, 121, 125,and 135 service be required to complywith the new standards relative to flamepropagation. Since there are materialscurrently available that will meet theproposed standards, this requirementwould impose minimal additional costs.This requirement would apply toairplanes manufactured more than twoyears after the effective date of the finalrule. Two years is considered sufficienttime to allow for material productioncapacity to be developed anddisposition of existing inventory.

It should be noted that this proposaldiffers from previous rulemaking relatedto flammability of materials in that theapplicability to newly manufacturedairplanes is not limited to operationsunder part 121. However, in this casethe proposal would effectively add nocost, and the potential for an inflight fireis not limited to air carrier operations.The FAA invites comments on thisaspect of the proposal.

Replacement: Amendments to parts91, 121, 125, and 135 are proposed torequire that insulation materials, wheninstalled as replacements, meet the newflame propagation test requirements of§ 25.856. This proposal would providefor the gradual attrition of earliermaterials. Since there are existingmaterials that meet the proposedstandards, and since those materialscost and weigh no more than othermaterials, this should result in noadditional cost to operators.

As with newly manufacturedairplanes, it is appropriate to addressnot only those airplanes operated in part121 air carrier service, but otheroperations as well, since the flamepropagation portion of this proposalwould enhance safety over the currentregulatory requirements, and can bedone at no cost. The language inproposed changes to part 121 differsfrom that in other parts to make it clearthat the replacement aspect of thisproposal does not in any way providerelief from the basic requirements fornewly manufactured airplanes. Asdiscussed below, part 121 differs fromother parts in that airplanesmanufactured after a specified date (fouryears after the effective date of the finalrule) would have to comply with theburnthrough protection standard, aswell as the flame propagation standard,and these requirements would also

apply to replacement materialssubsequently installed in thoseairplanes. To avoid possible confusion,the requirement for replacementmaterials to comply only with the flamepropagation standard would apply toairplanes manufactured before thespecified date.

Although it is difficult to quantify thebenefits of piecemeal replacement ofmaterials, in this case the benefit iswithout cost and adds no burden. Inorder to allow for attrition of currentinventories and acquisition of the newmaterials, the FAA is proposing a 2-yearcompliance time, after which insulationmaterials that are replaced would haveto be replaced with materials meetingthe new flame propagation standards.This requirement is expected to apply toa relatively small amount of materialsthat are replaced every year. As withnewly manufactured airplanes, twoyears is considered sufficient time toallow for material production capacityto be developed and disposition ofexisting inventory.

Burnthrough ProtectionNew Production: The FAA also

proposes that newly manufacturedairplanes entering the fleet in part 121operations be required to comply withthe new standards relative toburnthrough protection. Thisrequirement would apply to airplanesmanufactured more than 4 years afterthe effective date of the final rule.Although there are materials currentlyavailable that will meet the proposedstandards, these materials are notwidely used. Therefore, the burnthroughportion of the proposal is expected torequire both material and, in manycases, design changes to implement. Asdiscussed in the context of the proposedpart 25 changes, these design changesrelate primarily to the means offastening the insulation to the fuselagestructure. For those airplanes thatrequire design changes, the FAArecognizes that adequate time isnecessary to perform the necessaryengineering and to obtain approval forthe changes. Four years is considered areasonable time to implement anydesign changes and configurationcontrol measures required to account forthe new standard, and to allow formaterial availability.

Generally, airplanes operated underparts 91, 125, and 135 carry fewerpassengers than airplanes operatingunder part 121 and can, as a result, beevacuated more quickly. Therefore, theFAA considers that the additionalevacuation time provided by enhancedfuselage burnthrough protection wouldnot provide the same increase in safety

for these airplanes. In light of the costsassociated with requiring compliancewith the burnthrough standard,imposing the requirement would not becost effective. This conclusion is similarto the conclusion, discussed in thecontext of the proposed part 25burnthrough standard, not to impose thenew standard for airplanes with fewerthan 20 passengers. However, sincetransport category airplanes can beoperated under different regulatoryrequirements throughout their servicelife, it is likely that most, if not all,affected newly manufactured transportcategory airplanes would comply, inorder to account for potential future part121 operations. The FAA invitescomments on this aspect of theproposal.

Replacement: This proposal does notinclude a requirement to use materialscomplying with the burnthrough teststandards because the FAA considersthat such a requirement would not becost effective. If the fuselage is subjectedto an external fire, it is unlikely thatinsulation complying with this standardthat has been installed in a portion ofthe fuselage would significantly delayburnthrough if the rest of the fuselagecontains insulation that does notcomply with the new standard. Asdiscussed previously, in order to beeffective against burnthrough, newinsulation materials would also have tobe installed in a manner that wouldallow them to remain in place whenexposed to an external fire. Requiringthat the means of fastening, and theassociated engineering necessary toincorporate design changes, beaccounted for on a material replacementbasis would not be cost effective.

Date of Manufacture

For the purposes of this proposal, thedate of manufacture is considered to bethe date on which inspection recordsshow that an airplane is in a conditionfor safe flight. This is not necessarily thedate on which the airplane is inconformity with the approved typedesign, or the date on which a certificateof airworthiness is issued, since someitems not relevant to safe flight, such aspassenger seats, may not be installed atthat time. It could be earlier, but wouldbe no later, than the date on which thefirst flight of the airplane occurs. Thisdefinition has been used in previousrulemaking, including the preamble toAmendment 121–247, ImprovedFlammability Standards for MaterialsUsed in the Interiors of TransportCategory Airplanes, (60 FR 6616),§ 121.312 and § 121.343, Flightrecorders.



1 These estimates include airplanes producedunder new type certificates.

2 There would be no costs attributable to theproposed rule for airplanes of new type designs,because these engineering costs are for changes todrawings.

Paperwork Reduction Act

In accordance with the PaperworkReduction Act of 1995 (44 U.S.C3507(d)), the FAA has determined thatthere are no requirements forinformation collection associated withthis proposed rule.

International Compatibility

In keeping with U.S. obligationsunder the Convention on InternationalCivil Aviation, it is FAA policy tocomply with International CivilAviation Organization (ICAO) Standardsand Recommended Practices to themaximum extent practicable. The FAAhas determined that there are no ICAOStandards and Recommended Practicesthat correspond to these proposedregulations.

Regulatory Evaluation Summary

Changes to Federal regulations mustundergo several economic analyses.First, Executive Order 12866 directs thateach Federal agency shall propose oradopt a regulation only upon a reasoneddetermination that the benefits of theintended regulation justify its costs.Second, the Regulatory Flexibility Actof 1980 requires agencies to analyze theeconomic effect of regulatory changeson small entities. Third, the UnfundedMandates Reform Act of 1995 (Pub. L.104–4) requires each Federal agency toprepare a written assessment of theeffects of any Federal mandate in aproposed or final agency rule that mayresult in the expenditure by State, local,or tribal governments, in the aggregate,or by private sector, of $100 million ormore annually (adjusted for inflation).These analyses have been completed,are summarized below, and fullydiscussed in the full regulatoryevaluation. The FAA invites the publicto provide comments and supportingdata on the assumptions made in thisevaluation. All comments received willbe considered in the final regulatoryevaluation.

Costs of Proposed Rule

Testing results at the FAA’s TechnicalCenter show that insulation materialsare commercially available that willmeet the FAA’s proposed requirementsfor both flame propagation andburnthrough. The estimates presentedbelow are preliminary and mayoverstate the actual material costs toaffected operators, because other, lessexpensive materials may be developedas the proposed tests become known.The FAA solicits information frommanufacturers, air carriers, andinsulation blanket manufacturers torefine these estimates.

Insulation Material Unit Costs andWeights

Insulation material costs are afunction of the size of the airplane andits thermal and acoustical needs, which,in turn, depend on the configuration ofthe airplane, its performancecharacteristics, and its utilization. Basedon dimensional, material weight, andcost information received from airplanemanufacturers, air carriers, andinsulation blanket manufacturers, andthe results of testing by the FAA’sTechnical Center, the FAA hasdetermined that some materials thatwould meet the proposed testrequirements cost and weigh no morethan materials currently being installedin newly-produced airplanes. Becausethe proposed rule would apply tonewly-produced airplanes (i.e., noairplanes would be removed fromservice for retrofit), only the incrementalcosts of these improved blankets andengineering costs to effect any designchanges are attributable to the rule.

The FAA estimates that insulationblankets currently installed in transportcategory airplanes are composed of anaverage of 3 inches of fiberglass battingcovered with a film. Under the proposedrequirements for affected part 121airplanes with 20 or more passengerseats, the FAA assumes that the blanketsin the lower half of the fuselage wouldbe composed of an average of 2 inchesof fiberglass batting and 1 inch ofCurlon batting (a material that wouldmeet the proposed requirements forburnthrough protection), and theblankets in the upper half would becomposed of an average of 3 inches offiberglass. Blankets would be enclosedin metalized PVF, a film shown to meetthe proposed flame propagationrequirements. Airplanes with fewer than20 passenger seats would continue tohave an average of 3 inches of fiberglassbatting covered with metalized PVFfilm.

Other materials may also be used, butthese may be more expensive or addsubstantial weight to the blankets. TheFAA solicits information concerning thematerials that would be used to complywith the proposed requirements.

The FAA has determined that therewould be no incremental cost (for eithermaterials or weight) of installinginsulation in airplanes with fewer than20 passenger seats, because somematerials that are currently used wouldmeet the proposed requirements forflame propagation. For airplanes with20 or more passengers, the additionalcost would be that of replacing 1 inchof fiberglass with 1 inch of Curlon.Because Curlon and fiberglass are

comparable in weight, there would beno weight penalty associated withCurlon’s use.

Part 121 Airplanes Produced Between2000 and 2019

In order to determine the number andtypes of transport category airplanesadded to the U.S. air carrier (part 121)fleet during the years 2000–2019, theFAA reviewed its own forecast as wellas those of Boeing and Airbus. The FAAestimated the number of airplanes thatwould be affected by the proposed ruleand manufactured between 2000 and2019.1

Of the estimated 10,943 newlyproduced N-registered transportcategory airplanes expected to join thepart 121 fleet during that 20-year period,8,781 would be required to havefuselage burnthrough protection. Anestimated 2,162 newly-producedtransport category airplanes with fewerthan 20 seats would be exempt from thisproposed requirement.

The FAA has determined that someinsulation materials that are currentlyused would meet the proposedrequirements for flame propagation;therefore, the FAA attributes noincremental costs from this requirement.The total discounted cost for these 8,781airplanes that would be required to haveburnthrough protection over 20 years is$52.6 million, or $22.6 milliondiscounted to present value at sevenpercent. The annualized cost over 20years is $2.1 million.

The proposed requirement fortransport category airplanes operatingunder parts 91, 125, and 135 would beonly for improved insulation meetingthe proposed flame propagationstandards, and the FAA has determinedthat there would be no incrementalcosts from this requirement.

Engineering CostsManufacturers would incur costs of

changing installation drawings andproduction part numbers for the newinsulation blankets of newly producedcurrently certificated airplanes.2Estimates of the time to accomplishthese changes are a function of the sizeof the airplane and whether or not theblanket configuration would have to bechanged. The process of accomplishingthese tasks would involve a series ofsteps, including changing the drawings(part numbers and, when necessary,blanket configurations) and reviews and



approvals by various groups (e.g.,engineering, weight and balance, stressgroups).

The FAA estimates that there wouldbe 15 models of currently certificatedairplanes in operation under part 121 atthe time the proposed rule would beeffective. (The FAA assumes therewould be six models of two-enginenarrowbody airplanes, six models oftwo-engine widebody airplanes, two ofwhich would be cargo models, and threemodels of four-engine widebodyairplanes.) The FAA estimates theburdened hourly rate for an engineer is$130. If only blanket materials change,the FAA estimates costs would total$13.8 million. If both blanket materialsand their configurations change, theestimated costs would be $48.9 million.These costs would occur in the first 2years after the effective date of the rule.Discounted costs, assuming half the costwould be incurred in 2000 and half in2001, would range from $12.5 million to$44.2 million. The FAA solicitsinformation concerning the engineeringcosts to part 121 airplanemanufacturers, including informationconcerning the need for blanketconfiguration changes.

Because airplane models operatedunder part 125 are typically the sameairplane models that are operated underpart 121, there would be no additionalengineering costs to those models.Manufacturers of other transportcategory airplanes, that is, thoseoperating under parts 91 or 135, wouldalso incur engineering costs. The FAAestimates these costs to be $750,000, or$678,000 discounted to present value.

Testing EquipmentManufacturers of insulation blankets

or blanket components would incurcosts to test blankets or blanketcomponents. Two tests are proposed: aflame propagation test and aburnthrough test.

The flame propagation test (alsocalled the critical radiant flux test) isbased on a test method developed forfloor-covering systems, Standard TestMethod ASTM E 648 for CriticalRadiant Flux of Floor-Covering Systemsusing a Radiant Head Energy Source.The FAA’s Technical Center hasmodified the test method for purposesof measuring flame propagation oninsulation materials. A rig that is usedfor ASTM E 648 testing costs about$50,000. The FAA expects that airplanemanufacturers, insulation blanketfabricators, and chemical companymanufacturers would purchase orconstruct 12 of these modified rigs. Thecosts, therefore, would be $720,000. TheFAA assumes that these costs would be

incurred in the first year of the rule.Based on the assumption that theproposed rule would become effectivein the year 2000, the costs of flamepropagation testing equipment would be$673,000 discounted to present value.

The proposed burnthrough test wasdeveloped through the joint sponsorshipof the FAA, the Civil Aviation Authorityof the United Kingdom (UK), and theDirection Generale de l’Aviation Civile(DGAC) of France, with the FAA’sTechnical Center providing the teststandardization. The equipment wouldinclude a gun-type test burner that useskerosene for a fuel source and variouscomponents that measure heat flux,temperature, air velocity, and time. Thetest rig would be provided with anexhaust system to remove combustionproducts. The FAA estimates that thetest apparatus would cost about$10,000. Again, the FAA expects thatairplane manufacturers, insulationblanket fabricators, and chemicalcompanies would purchase 12 rigs. Thecosts, therefore, would be $120,000 for12 rigs, or $112,000 discounted topresent value.

Manufacturers currently havefacilities and personnel that conductblanket certification testing; therefore,the FAA has attributed no other costs totesting materials.

Total Costs of the Proposed Rule

If only blanket material changes aremade, the total costs over the years2000–2019 are $68.0 million, or $36.5million discounted to present value.Improved insulation costs account forabout 77 percent of total nondiscountedcosts, while engineering costs accountfor 21 percent and testing equipmentaccounts for 1 percent.

If manufacturers need to makeconfiguration changes as well asmaterial changes to their drawings, theFAA estimates that total costs would be$103.1 million over the years 2000–2019, or $68.2 million discounted topresent value. In this scenario,engineering costs account for 51 percentof total nondiscounted costs, improvedinsulation costs account for 48 percent,and testing equipment accounts for 1percent.

In both scenarios, the greatest costswould be incurred during the first 2years after the effective date, whenairplane and insulation blanketmanufacturers and testing labs wouldincur costs. On a per airplane basis, thecosts would average between $6,200 and$9,400, depending on whether or notconfiguration changes were needed.

Benefits of the Proposed Rule

On September 2, 1998, Swissair Flight111 crashed off the coast of Nova Scotia,Canada, with a loss of 229 lives.

Although the Transportation SafetyBoard of Canada has not released itsreport of the probable causes of theSwissair accident, preliminary evidencepoints to burning thermal/acousticalinsulation above the cockpit ceiling ascontributing to the crash. The airplane,a McDonnell Douglas MD–11, usedinsulation blankets composed offiberglass covered with metalizedMylar. The FAA considers thatreplacement of metalized Mylar maybe necessary and is proceeding toaddress the affected material byairworthiness directive.

There have been other reports of firesin which the flammability of thethermal/acoustical insulation was acontributing factor. These accidents andincidents indicate that the flammabilityof the thermal/acoustic insulation canbe a significant factor in contributing tothe spread of a fire, either inflight orafter a crash. The proposed rule wouldreduce those threats by requiring newlyproduced airplanes to use improvedinsulation that passes the proposedrequirements for flame propagation andfuselage burnthrough.

The FAA, in conjunction with theCAA–UK and the DGAC of France,conducted research to assess the currentcapability of airplane fuselages to resistburnthrough from an external fuel fire.That research demonstrated theimportance of thermal/acousticinsulation in the burnthrough process.Without making any other change to theairplane, these studies showed thatimproved thermal/acoustic insulationcan delay the entry of a post-crash fuelfire by several minutes, thus prolongingthe time available for escape. Althoughthere are other factors that affectfuselage burnthrough, it wasdemonstrated that the simplest andmost effective approach to improvingburnthrough resistance was to improvethe fire resistance of the insulation.

A study by R.G.W. Cherry &Associates Limited examined theInternational Cabin Safety ResearchTechnical Group’s Survivable AccidentsDatabase to identify and extract data forairplane accidents where fuselageburnthrough was an issue in thesurvivability of the occupants. Aburnthrough accident was defined as:‘‘An aircraft accident where the fuselageskin was penetrated by an external firewhile live occupants were on board.’’ Asurvivable accident is one ‘‘where therewere one or more survivors or there waspotential for survival.’’ Only survivable



or potentially survivable accidents inwhich there were fire injuries wereselected for analysis.

Seventeen accidents involving 2,201occupants and occurring between 1966and 1993 were identified by Cherry &Associates. In analyzing accidents,Cherry & Associates took into accountimprovements that might have beenmade to numbers of fatalities andinjuries if the airplanes had beenconfigured to later requirements. Theselater requirements were:

• Floor proximity lighting/marking• Seat cushion flammability• Reduced heat release of cabin

interior materials• Improved access to type III exitsCherry & Associates derived benefits

based on the airplane standards at thetime of the accident and on airplanesassumed to be configured to laterrequirements. Because the proposedrule would apply to newly producedairplanes, the results based on laterrequirements are those used in theFAA’s benefits analysis.

Of the 140 worldwide fire related fatalaccidents in the International CabinSafety Research Technical Group’sSurvivable Accidents Database at thetime of Cherry & Associate’s study, only54 percent had sufficient data to assesswhether burnthrough occurred.Assuming the accidents that did nothave sufficient data have a similarbenefit potential to those that do, theactual benefits would be 1.85 times (1/0.54) the analyzed benefits.

The FAA’s Technical Center hasdetermined that the burnthroughprotection requirements of thisproposed rule would provide anadditional 4 minutes for occupants toexit an airplane. Cherry & Associates’analysis shows that an additional 4minutes would result in 10.1 lives savedper year worldwide. Because theproposed rule would apply only tonewly produced airplanes of U.S.registry, the FAA has adjusted thisestimate downward.

The Cherry report states that theauthors do not believe that ‘‘* * * thenumber of fatalities and injuries willchange markedly for the near future.’’The FAA disagrees. Based on FAA andindustry forecasts, the number oftransport category passenger airplanesin the world fleet is expected to grow by109 percent over the years 2000—2019,while the number of airplanes in theU.S. fleet is expected to grow by 97percent. The number of passengersenplaned by U.S. carriers is expected togrow by 107 percent. Therefore, theFAA has estimated that Cherry’sestimate of 10.1 lives saved per year

would increase by about 2.157 percentper year or by 50 percent by 2019.

The FAA estimates that 37.2 fatalitiesthat would have occurred on airplanesof U.S. registry would be avoided over20 years by the proposed rule’srequirement for burnthrough protection.Assuming society is willing to pay $2.7million to avoid a fatality, burnthroughprotection for the newly producedairplanes in the U.S. fleet would resultin a nondiscounted total benefit of$100.5 million over the 20-year period,or $37.7 million discounted to presentvalue.

There would also be benefits from theproposed flame propagationrequirement. As several of the incidentsand accidents reviewed for this analysisand described in the completeregulatory evaluation show, thepotential for ignition from electricalarcing or other sources can be high. Theproposed flame propagationrequirements would ensure that, ifignition occurred, the resultant flamewould not spread on the thermal/acoustic insulation.

The FAA is unable to quantify thesebenefits. However, preventing the lossof one airplane and its passengers overthe 20-year period is not unlikely.Assuming such a loss would occur atthe midpoint of the analysis, or in 2009,with 169 passengers, the nondiscountedloss would be $455.5 million, or $231.5million discounted to present value(again, assuming society’s willingness topay $2.7 million to avoid a fatality).This loss does not include the value ofthe airplane. Even without loss of life,as several of the incidents show, a hullloss could exceed tens of millions ofdollars. The FAA therefore hasdetermined that this proposed rulewould be cost beneficial.

Initial Regulatory FlexibilityDetermination

The Regulatory Flexibility Act of 1980(FRA) establishes ‘‘as a principle ofregulatory issuance that agencies shallendeavor, consistent with the objectiveof the rule and of applicable statutes, tofit regulatory and informationalrequirements to the scale of thebusinesses, organizations, andgovernmental jurisdictions subject toregulation.’’ To achieve that principle,the RFA requires agencies to solicit andconsider flexible regulatory proposalsand to explain the rationale for theiractions. The RFA covers a wide-range ofsmall entities, including smallbusinesses, not-for-profit organizations,and small governmental jurisdictions.

Agencies must perform a review todetermine whether a proposed or finalrule will have a significant economic

impact on a substantial number of smallentities. If the determination is that itwill, the agency must prepare aregulatory flexibility analysis (RFA) asdescribed in the RFA. However, if anagency determines that a proposed orfinal rule is not expected to have asignificant economic impact on asubstantial number of small entities,section 605(b) of the 1980 act providesthat the head of the agency may socertify and an RFA is not required. Thecertification must include a statementproviding the factual basis for thisdetermination, and the reasoning shouldbe clear.

The FAA conducted the requiredreview of this proposed rule. Theengineering costs would be incurred bymanufacturers of transport categoryairplanes, none of whom is a smallentity. Testing equipment costs wouldbe incurred by airplane manufacturers,insulation blanket fabricators, andchemical companies. The FAA hasdetermined that none of these entitiesthat are expected to conduct testing issmall. Finally, the cost of a newlyproduced passenger airplane outfittedwith burnthrough protection would begreater because of the proposed rule.The FAA cannot determine who wouldpurchase these airplanes, but theincremental cost of burnthroughprotection would not exceed $11,000 (ina four-engine widebody), an amountthat would represent an insignificantpercentage of the total cost of a newairplane.

Accordingly, pursuant to theRegulatory Flexibility Act, 5 U.S.C.605(b), the Federal AviationAdministration certifies that thisproposed rule would not have asignificant economic impact on asubstantial number of small entities.

International Trade Impact AssessmentThe provisions of this proposed rule

would have little or no impact on tradefor U.S. firms doing business in foreigncountries and foreign firms doingbusiness in the United States.

Unfunded Mandates Reform ActTitle II of the Unfunded Mandates

Reform Act of 1995 (the Act), enacted asPublic Law 104–4 on March 22, 1995,requires each Federal agency, to theextent permitted by law, to prepare awritten assessment of the effects of anyFederal mandate in a proposed or finalagency rule that may result in theexpenditure by State, local, and tribalgovernments, in the aggregate, or by theprivate sector, of $100 million or more(adjusted annually for inflation) in any1 year. Section 204(a) of the Act, 2U.S.C. 1534(a), requires the Federal



agency to develop an effective processto permit timely input by electedofficers (or their designees) of State,local, and tribal governments on aproposed ‘‘significant intergovernmentalmandate.’’

A ‘‘significant intergovernmentalmandate’’ under the Act is anyprovision in a Federal agency regulationthat would impose an enforceable dutyupon State, local, and tribalgovernments, in the aggregate, of $100million (adjusted annually for inflation)in any 1 year. Section 203 of the Act, 2U.S.C. 1533, which supplements section204(a), provides that before establishingany regulatory requirements that mightsignificantly or uniquely affect smallgovernments, the agency shall havedeveloped a plan that, among otherthings, provides for notice to potentiallyaffected small governments, if any, andfor a meaningful and timely opportunityto provide input in the development ofregulatory proposals.

This proposed rule does not containany significant Federalintergovernmental or private sectormandate. Therefore, the requirements ofTitle II of the Unfunded MandatesReform Act of 1995 do not apply.

Executive Order 13132, FederalismThe FAA has analyzed this proposed

rule under the principles and criteria ofExecutive Order 13132, Federalism. TheFAA has determined that this actionwould not have a substantial directeffect on the States, on the relationshipbetween the national Government andthe States, or on the distribution ofpower and responsibilities among thevarious levels of government. Therefore,the FAA has determined that this noticeof proposed rulemaking would not havefederalism implications.

Environmental AnalysisFAA Order 1050.1D defines FAA

actions that may be categoricallyexcluded from preparation of a NationalEnvironmental Policy Act (NEPA)environmental assessment orenvironmental impact statement. Inaccordance with FAA Order 1050.1D,appendix 4, paragraph 4(j), thisrulemaking action qualifies for acategorical exclusion.

Energy ImpactThe energy impact of the proposed

rule has been assessed in accordancewith the Energy Policy andConservation Act (EPCA) and Public

Law 94–163, as amended (42 U.S.C.6362). It has been determined that it isnot a major regulatory action under theprovisions of the EPCA.

Regulations Affecting IntrastateAviation in Alaska

Section 1205 of the FAAReauthorization Act of 1996 (110 Stat.3213) requires the Administrator, whenmodifying regulations in Title 14 of theCFR in a manner affecting intrastateaviation in Alaska, to consider theextent to which Alaska is not served bytransportation modes other thanaviation, and to establish suchregulatory distinctions as he or sheconsiders appropriate. Because thisproposed rule would apply to thecertification of future designs oftransport category airplanes and theirsubsequent operation, it could, ifadopted, affect intrastate aviation inAlaska. The FAA therefore specificallyrequests comments on whether there isjustification for applying the proposedrule differently to intrastate operationsin Alaska.

List of Subjects

14 CFR Part 25

Aircraft, Aviation safety, Reportingand recordkeeping requirements.

14 CFR Part 91


14 CFR Part 121

Aircraft, Aviation safety, Reportingand recordkeeping requirements, Safety,Transportation.

14 CFR Part 125


14 CFR Part 135


The Proposed AmendmentsIn consideration of the foregoing, the

Federal Aviation Administrationproposes to amend parts 25, 91, 121,125, and 135 of Title 14 of the Code ofFederal Regulations as follows:

PART 25—AIRWORTHINESSSTANDARDS: TRANSPORTCATEGORY AIRPLANES

1. The authority citation for part 25continues to read as follows:

Authority: 49 U.S.C. 106(g), 40113, 44701–44702, and 44704.

2. Amend § 25.853 by revisingparagraph (a) to read as follows:

§ 25.853 Compartment interiors.

* * * * *(a) Except for thermal/acoustic

insulation materials, materials(including finishes or decorativesurfaces applied to the materials) mustmeet the applicable test criteriaprescribed in part I of appendix F of thispart, or other approved equivalentmethods, regardless of the passengercapacity of the airplane.* * * * *

3. Amend § 25.855 by revisingparagraph (d) to read as follows:

§ 25.855 Cargo or baggage compartments.

* * * * *(d) Except for thermal/acoustic

insulation materials, all other materialsused in the construction of the cargo orbaggage compartment must meet theapplicable test criteria prescribed in partI of appendix F of this part or otherapproved equivalent methods.* * * * *

4. Add § 25.856 to read as follows:

§ 25.856 Insulation materials.

Thermal/acoustic insulation materialmust meet the flame propagation testrequirements of part VI of appendix F ofthis part, or other FAA-approvedequivalent test requirements. Inaddition, for airplanes with a passengercapacity of 20 or greater, insulationmaterials (including the means offastening the materials to the fuselage)installed in the lower half of theairplane fuselage must meet the flamepenetration resistance test requirementsof part VII of appendix F of this part, orother FAA-approved equivalent testrequirements.

5. Amend appendix F to part 25 asfollows:

a. In part I, paragraph (a)(1)(ii), byremoving the words ‘‘thermal andacoustical insulation and insulationcovering’’ and ‘‘insulation blankets’’from the first sentence.

b. In part I, by removing and reservingparagraph (a)(2)(i).

c. By adding parts VI and VII to readas follows:



Appendix F to Part 25

* * * * *

Part VI–Test Method to Determine theFlammability and Flame PropagationCharacteristics of Thermal/AcousticInsulation Materials

This test method is used to evaluate theflammability and flame propagation

characteristics of thermal/acoustic insulationwhen exposed to both a radiant heat sourceand a flame.

(a) Definitions—(1) Thermal acousticinsulation. Thermal/acoustic insulation isdefined as a material or system of materialsused to provide thermal and/or acousticprotection. Examples include a film-coveringmaterial encapsulating a core material such

as fiberglass or other batting material andfoams.

(2) Radiant heat source. The radiant heatsource is an air-gas fueled radiant heat energypanel or equivalent.

(b) Test apparatus (as schematically shownin figure 1).



(1) Radiant panel test chamber. Tests shallbe conducted in a radiant panel test chamber(see figure 1). The test chamber shall belocated under an exhaust hood to facilitateclearing the chamber of smoke after each test.The radiant panel test chamber shall consistof an enclosure 55 inches (1400 mm) long by19.5 (500 mm) deep by 28 (710 mm) to 30inches (maximum) (762 mm) above the testspecimen. The sides, ends, and top shall beinsulated with a fibrous ceramic insulation

such as Kaowool M TM board. The front sideshall be provided with an approximately 52-by 10-inch (1321 by 254mm) draft free, hightemperature, glass observation window, tofacilitate viewing the sample during testing.Below the window is a door, which providesaccess to the movable specimen platformholder. The bottom of the test chamber shallconsist of a sliding steel platform, which hasprovisions for securing the test specimenholder in a fixed and level position. The

chamber shall have an internal chimney withexterior dimensions of 5.1 inches (129mm)wide, by 16.2 inches (411 mm) deep by 13inches (330mm) high at the opposite end ofthe chamber from the radiant energy source.The interior dimensions are 4.5 inches(114mm) wide by 15.6 inches (395mm) deep.The chimney extends to the top of thechamber (see figure 2).



(2) Radiant heat source. The radiant heatenergy source shall be a panel of porousrefractory material mounted in a cast ironframe or equivalent. The panel shall have a

radiation surface of 12 by 18 inches (305 by457mm). The panel shall be capable ofoperating at temperatures up to 1500°F(816°C). See figure 3. An equivalent panel

must satisfy the calibration conditions andproduce test results equivalent to the air-gaspanel, for any material tested.



(i) Radiant panel heating system. Theradiant panel fuel shall be propane (liquidpetroleum gas—2.1 UN 1075). The panel fuelsystem shall consist of a venturi-typeaspirator for mixing gas and air atapproximately atmospheric pressure.Suitable instrumentation will be necessaryfor monitoring and controlling the flow offuel and air to the panel. Instrumentation

shall include an air flow gauge, an air flowregulator, and a gas pressure gauge.

(ii) Radiant panel placement. The panelshall be mounted in the chamber at 30§ to thehorizontal specimen plane.

(3) Specimen holding system. (i) Thesliding platform serves as the housing for testspecimen placement. Brackets may beattached (via wing nuts) to the top lip of theplatform in order to accommodate various

thicknesses of test specimens. A sheet ofrefractory material may be placed andsupported by the lip in the open bottom(base) of the sliding platform for samples thatdo not require height compensation. Therefractory material may be placed on thebottom of the brackets to hold the testspecimen (for height requirement) ifnecessary. See figure 4.



(ii) A 1⁄2 inch (13mm) piece of KaowoolM TM board or other high temperaturematerial measuring 411⁄2 by 81⁄4 inches (1054by 210mm) shall be attached to the back sideof the platform. This board will serve as aheat retainer and will protect the testspecimen from excessive preheating. Theheight of this board must not be too high

such that it impedes the sliding platformmovement (in and out) of the test chamber.

(iii) The test specimen shall be placedhorizontally on the refractory base (orbrackets). A stainless steel retaining frame(AISI Type 300 UNA–NO8330), orequivalent, having a thickness of 0.078inches (1.98mm) and overall dimensions of

44 3⁄4 by 123⁄4 inches (1137 by 320mm) witha specimen opening of 40 by 77⁄8 inches(1016 by 140mm) shall be placed on top ofthe test specimen. The retaining frame shallhave two 1⁄2 inch (12.7mm) holes drilled ateach end for positioning the frame to the twostud bolts at each end of the sliding platform.See figure 5.



(iv) A securing frame (acting as a clampingmechanism) constructed of mildsteel may beplaced over the test specimen. The securingframe overall dimensions are 421⁄2 by 101⁄2inches (1080 by 267mm) with a specimen

opening of 391⁄2 by 71⁄2 inches (1003 by190mm). Hence, the exposed area of testspecimen exposed to the radiant panel is391⁄4 by 71⁄4 inches (996 by 184mm). Seefigure 6. It is not necessary to physically

fasten the securing frame over the testspecimen due to the weight of the frameitself.



(4) Pilot burner. The pilot burner used toignite the specimen is a Bernzomatic TM

commercial propane venturi torch with anaxially symmetric burner tip having apropane supply tube with an orifice diameterof 0.006 inches (0.15mm). The length of the

burner tube is 27⁄8 inches (71mm). Thepropane flow is adjusted via gas pressurethrough an in-line regulator to produce a blueinner cone length of 3⁄4 inch (19mm). A 3⁄4inch (19mm) guide (such as a thin strip ofmetal) may be spot welded to the top of the

burner to aid in setting the flame height.There shall be a means provided to move theburner out of the ignition position so that theflame is horizontal and at least 2 inches(50mm) above the specimen plane. See figure7.

(5) Thermocouples. A 24 American WireGauge (AWG) Type K (Chromel-Alumel)thermocouple shall be installed in the testchamber for temperature monitoring. It shallbe inserted into the chamber through a smallhole drilled through the back of the chamber.The thermocouple shall be placed such thatit extends 11 inches (279mm) out from theback of the chamber wall, 111⁄2 inches(292mm) from the right side of the chamberwall, and is 2 inches (51mm) below theradiant panel. The use of otherthermocouples is optional.

(6) Calorimeter. The calorimeter shall be aone inch cylindrical water-cooled, total heatflux density, foil type Gardon Gage that hasa range of 0 to 5 BTU/ft 2-second (0 to 5.6Watts/cm2).

(7) Calorimeter calibration specificationand procedure.

(i) Calorimeter Specification.(A) Foil diameter shall be 0.25 ±0.005

inches (6.35 ±0.13mm).(B) Foil thickness shall be 0.0005 ±0.0001

inches (0.013 ±0.0025mm).(C) Foil material shall be thermocouple

grade Constantan.(D) Temperature measurement shall be a

Copper Constantan thermocouple.

(E) The copper center wire diameter shallbe 0.0005 inches (0.013mm).

(F) The entire face of the calorimeter shallbe lightly coated with ‘‘Black Velvet’’ painthaving an emissivity of 96 or greater.

(ii) Calorimeter calibration.(A) The calibration method shall be by

comparison to a like standardized transducer.(B) The standardized transducer shall meet

the specification given in paragraph (b)(6) ofthis part of this appendix.

(C) It shall be calibrated against a primarystandard by the National Institute ofStandards and Technology (NIST).

(D) The method of transfer shall be aheated graphite plate.

(E) The graphite plate shall be electricallyheated, have a clear surface area on each sideof the plate of at least 2 by 2 inches (51 by51mm), and be 1⁄8 inch ±1⁄16 inch thick (3.2±1.6mm).

(F) The 2 transducers shall be centered onopposite sides of the plates at equal distancesfrom the plate.

(G) The distance of the calorimeter to theplate shall be no less than 0.0625 inches(1.6mm), nor greater than 0.375 inches(9.5mm).

(H) The range used in calibration shall beat least 0–3.5 BTUs/ft 2 second (0–3.9Watts/cm2) and no greater than 0–5.6 BTUs/ft 2

second (0–5 Watts/cm2.(I) The recording device used must record

the 2 transducers simultaneously or at leastwithin 1⁄10 of each other.

(8) Calorimeter Fixture. With the slidingplatform pulled out of the chamber, installthe calorimeter holding frame. The frame is131⁄8 inches (333mm) deep (front to back) by8 inches (203mm) wide and rests on the topof the sliding platform. It is fabricated of 1⁄8inch (3.2mm) flat stock steel and has anopening that accommodates a 1⁄2 inch(12.7mm) thick piece of Kaowool MTM board,which is level with the top of the slidingplatform. The board has three 1 inch(25.4mm) diameter holes drilled through theboard for calorimeter insertion. The distancefrom the outside frame (right side) to thecenterline of the first hole (‘‘zero’’ position)is 17⁄8 inches (47mm). The distance betweenthe centerline of the first hole to thecenterline of the second hole is 2 inches(51mm). It is also the same distance from thecenterline of the second hole to thecenterline of the third hole. See figure 8.





(9) Instrumentation. A calibrated recordingdevice with an appropriate range or acomputerized data acquisition system shallbe provided to measure and record theoutputs of the calorimeter and thethermocouple. The data acquisition systemmust be capable of recording the calorimeteroutput every second during calibration.

(10) Timing device. A stopwatch or otherdevice, accurate to ±1 second/hour, shall beprovided to measure the time of applicationof the pilot burner flame.

(c) Test specimens.(1) Specimen preparation. A minimum of

three test specimens shall be prepared andtested.

(2) Construction. Test specimens shallinclude all materials used in construction ofthe insulation (including batting, film, scrim,tape etc.). Cut a piece of core material suchas foam or fiberglass, 43 inches long(1092mm) by 11 inches (279mm) wide. Cuta piece of film cover material (if used) largeenough to cover the core material. There area number of ways to prepare the sample.These include stapling the film cover aroundthe ends (as the ends are not exposed to theradiant heat source), wrapping the corematerial and taping it at the bottom, and heatsealing the sample. The specimen thicknessmust be of the same thickness as installed inthe airplane.

(d) Specimen conditioning. The specimensshall be conditioned at 70 ±5 °F (21 ±2 °C)and 55% ±10% relative humidity, for aminimum of 24 hours prior to testing.

(e) Calibration. (1) With the slidingplatform out of the chamber, install thecalorimeter holding frame. Push the platformback into the chamber and insert thecalorimeter into the first hole (‘‘zero’’position). See figure 8. Close the bottom doorlocated below the sliding platform. Thecenterline of the calorimeter is 17⁄8 inches(46mm) from the end of the holding frame.The distance from the centerline of thecalorimeter to the radiant panel surface atthis point is 7.5 inches ±1⁄8 (191 mm ±3).Prior to igniting the radiant panel, ensurethat the calorimeter face is clean and thatthere is water running through thecalorimeter.

(2) Ignite the panel. Adjust the fuel/airmixture to achieve 1.5 BTUs/ft 2-second ±5%(1.8 Watts/cm2 ±5%) at the ‘‘zero’’ position.If using an electric panel, set the powercontroller to achieve the proper heat flux.Allow the unit to reach steady state (this maytake up to 1 hour). The pilot burner is offduring this time.

(3) After steady-state conditions have beenreached, move the calorimeter 2 inches(51mm) from the ‘‘zero’’ position (first hole)to the second position and record the heatflux. Move the calorimeter to the thirdposition and record the heat flux. Allowenough time at each position for thecalorimeter to stabilize.

(4) Open the bottom door, remove thecalorimeter and holder fixture. Use cautionas the fixture is very hot.

(f) Test procedure. (1) Ignite the pilotburner. Ensure that it is at least 2 inches

(51mm) above the top of the platform. Theburner must not contact the specimen untilthe test begins.

(2) Place the test specimen in the slidingplatform holder. Ensure that the test samplesurface is level with the top of the platform.At ‘‘zero’’ point, the specimen surface is 71⁄2inches ±1⁄8 inch (191mm ±3) below theradiant panel.

(3) With film/fiberglass assemblies, it maybe necessary to puncture small holes in thefilm cover to purge any air inside. Thisallows the operator to maintain the propertest specimen position (level with the top ofthe platform). The holes should be made inthe sides/ and or the corners of the testspecimen using a needle-like tool.

(4) Place the retaining frame over the testspecimen. The securing frame may be usedif the samples have been stapled and tend toshrink away from the radiant heat source. Itmay be necessary (due to compression) toadjust the sample (up or down) in order tomaintain the distance from the sample to theradiant panel (71⁄2 inches ±1⁄8 inch(191mm±3) at ‘‘zero’’ position).

(5) Immediately push the sliding platforminto the chamber and close the bottom door.

(6) Bring the pilot burner flame intocontact with the center of the specimen at the‘‘zero’’ point and simultaneously start thetimer. The pilot burner shall be at a 27° anglewith the sample and be 1⁄2 inch (12mm)above the sample. See figure 8. A stop, asshown in figure 9, allows the operator toposition the burner in the correct positioneach time.



(7) Leave the burner in position for 15seconds and then remove to a position atleast 2 inches (51mm) above the specimen.

(g) Report. (1) Identify and describe thespecimen being tested.

(2) Report any shrinkage or melting of thetest specimen.

(3) Report the flame time.(4) Report the after flame time.(h) Requirements. (1) No flaming beyond 2

inches (51mm) to the left of the centerline ofthe point of pilot flame application isallowed.

(2) Of the 3 specimens tested, only 1specimen may have an after flame. That afterflame may not exceed 3 seconds.

Part VII—Test Method to Determine theBurnthrough Resistance of Thermal/AcousticInsulation Materials.

The following test method is used toevaluate the burnthrough resistancecharacteristics of aircraft thermal-acousticinsulation materials when exposed to a highintensity open flame.

(a) Definitions—(1) Burnthrough time. Theburnthrough time is measured at the inboardside of each of the insulation blanketspecimens. The burnthrough time is definedas the time required, in seconds, for theburner flame to penetrate the test specimen,and/or the time required for the heat flux toreach 2.0 Btu/ft2sec on the inboard side, ata distance of 12 inches from the front surface

of the insulation blanket test frame,whichever is sooner.

(2) Specimen set. A specimen set consistsof two insulation blanket specimens. Bothspecimens must represent the sameproduction insulation blanket constructionand materials, proportioned to correspond tothe specimen size.

(3) Insulation blanket specimen. Theinsulation blanket specimen is one of twospecimens positioned in either side of thetest rig, at an angle of 30° with respect tovertical.

(b) Apparatus—(1) The arrangement of thetest apparatus is shown in figures 1 and 2and shall include swinging the burner awayfrom the test specimen during warm-up.



(2) Test burner. The test burner shall be amodified gun-type such as the Park Model

DPL 3400. Flame characteristics may beenhanced with the optional use of a static

disc turbulator or a temperaturecompensation fuel nozzle.



(i) Nozzle. A nozzle is required to maintainthe fuel pressure to yield a nominal 6.0 gal/hr (0.378 L/min) fuel flow. A Monarchmanufactured 80° PL (hollow cone) nozzlenominally rated at 6.0 gal/hr at 100 lb/in2

(0.71 MPa) has been found to deliver a properspray pattern. Minor deviations to the fuel

nozzle spray angle, fuel pressure, or othersimilar parameters are acceptable if thenominal fuel flow rate and temperature andheat flux measurements conform to therequirements of paragraph (e) of this part ofthis appendix.

(ii) Burner cone. A 12 ±0.125-inch (305 ±6mm) burner extension cone shall be installedat the end of the draft tube. The cone shallhave an opening 6 ±0.125-inch (152 ±6 mm)high and 11 ±0.125-inch (280 ±6 mm) wide(figure 3).BILLING CODE 4910–13–U



BILLING CODE 4910–13–C



(iii) Fuel. JP–8, Jet A, or their internationalequivalent has been found to satisfactorilydeliver a 6.0 ±0.2 gal/hr flow rate. If this fuelis unavailable, ASTM K2 fuel (Number 2grade kerosene) or ASTM D2 fuel (Number 2grade fuel oil or Number 2 diesel fuel) areacceptable if the nominal fuel flow rate,temperature and heat flux measurementsconform to the requirements of paragraph (e)of this part of this appendix.

(iv) Fuel pressure regulator. A fuel pressureregulator, adjusted to deliver 6.0 gal/hr (0.378L/min) nominal, shall be provided. Anoperating fuel pressure of 100 lb/in2 for a 6.0gal/hr 80° spray angle nozzle (such as a PL

type) has been found to be satisfactory todeliver 6.0 ±0.2 gal/hr (0.378 L/min).

(3) Calibration rig and equipment. (i) Acalibration rig shall be constructed toincorporate a calorimeter and thermocouplerake for the measurement of both heat fluxand temperature. A combined temperatureand heat flux calibration rig enables a quicktransition between these devices, so that theinfluence of air intake velocity on heat fluxand temperature can be analyzed withoutnecessitating removal of the calibration rig.Individual calibration rigs are alsoacceptable.

(ii) Calorimeter. The calorimeter shall be atotal heat flux, foil type Gardon Gage of an

appropriate range such as 0–20 Btu/ft2-sec(0–22.7 W/cm2), accurate to ±3% of theindicated reading. The heat flux calibrationmethod shall be in accordance with appendixF, part VI, paragraph (b)(7).

(iii) Calorimeter mounting. The calorimetershall be mounted in a 6- by 12- ±0.125 inch(152- by 305- ±3 mm) by 0.75 ±0.125 inch (19mm ±3 mm) thick insulating block which isattached to a calibration rig for attachment tothe test rig during calibration (figure 4). Theinsulating block shall be monitored fordeterioration and replaced when necessary.The mounting shall be adjusted as necessaryto ensure that the calorimeter face is parallelto the exit plane of the test burner cone.





(iv) Thermocouples. Seven 1⁄8-inch ceramicpacked, metal sheathed, type K (Chromel-alumel), grounded junction thermocoupleswith a nominal 24 American Wire Gauge

(AWG) size conductor shall be provided forcalibration. The thermocouples shall beattached to a steel angle bracket to form athermocouple rake for placement in the

calibration rig during burner calibration(figure 5).



(v) Air velocity meter. A vane-type airvelocity meter must be used to calibrate thevelocity of air entering the burner. An OmegaEngineering Model HH30A has been shownto be satisfactory. A suitable adapter used toattach the measuring device to the inlet sideof the burner is required to prevent air fromentering the burner other than through thedevice, which would produce erroneouslylow readings.

(4) Test specimen mounting frame. Themounting frame for the test specimens shall

be fabricated of 1⁄8-inch thick steel as shownin figure 1, except for the center verticalformer, which should be 1⁄4-inch thick tominimize warpage. The specimen mountingframe stringers (horizontal) should be boltedto the test frame formers (vertical) such thatthe expansion of the stringers will not causethe entire structure to warp. The mountingframe shall be used for mounting the twoinsulation blanket test specimens as shownin figure 2.

(5) Backface calorimeters. Two total heatflux Gardon type calorimeters shall bemounted above the insulation test specimenson the back side (cold) area of the testspecimen mounting frame as shown in figure6. The calorimeters must be positioned alongthe same plane as the burner cone centerline,at a distance of 4 inches from the centerlineof the test frame. The heat flux calibrationshall be in accordance with appendix F, partVI, paragraph (b)(7).



(6) Instrumentation. A recordingpotentiometer or other suitable calibratedinstrument with an appropriate range shallbe provided to measure and record theoutputs of the calorimeter and thethermocouples.

(7) Timing device. A stopwatch or otherdevice, accurate to +/-1%, shall be providedto measure the time of application of theburner flame and burnthrough time.

(8) Test chamber. Tests should beperformed in a suitable chamber to reduce oreliminate the possibility of test fluctuationdue to air movement. The chamber musthave a minimum floor area of 10 by 10 feet.

(i) Ventilation hood. The test chambermust be provided with an exhausting systemcapable of removing the products ofcombustion expelled during tests.

(c) Test specimens—(1) Specimenpreparation. A minimum of three specimensets of the same construction andconfiguration shall be prepared for testing.

(2) The insulation blanket test specimen. (i)For batt-type materials such as fiberglass, theconstructed, finished blanket specimen

assemblies shall be 32 inches wide by 36inches long, exclusive of heat sealed filmedges.

(ii) For rigid and other non-conformingtypes of insulation materials, the finished testspecimens shall fit into the test rig in sucha manner as to replicate the actual in-serviceinstallation.

(3) Construction. Each of the specimenstested shall be fabricated using the principalcomponents (i.e., insulation, fire barriermaterial if used, and moisture barrier film)and assembly processes (representativeseams and closures).

(i) Fire barrier material. If the insulationblanket is constructed with a fire barriermaterial, the fire barrier material shall beplaced in a manner reflective of the installedarrangement (e.g., if the material will beplaced on the outboard side of the insulationmaterial, inside the moisture film, it must beplaced accordingly in the test specimen).

(ii) Insulation material. Blankets thatutilize more than one variety of insulation(composition, density, etc.) shall havespecimen sets constructed that reflect the

insulation combination used. If, however,several blanket types use similar insulationcombinations, it is not necessary to test eachcombination if it is possible to bracket thevarious combinations.

(iii) Moisture barrier film. If a productionblanket construction utilizes more than onetype of moisture barrier film, separate testsmust be performed on each combination. Forexample, if a polyimide film is used inconjunction with an insulation in order toenhance the burnthrough capabilities, thesame insulation with a polyvinyl fluoridemust also be tested.

(iv) Installation on test frame. The blankettest specimens must be attached to the testframe using 12 steel spring type clamps asshown in figure 7. The clamps must be usedto hold the blankets in place in both of theouter vertical formers, as well as the centervertical former (4 clamps per former). Placethe top and bottom clamps 6 inches from thetop and bottom of the test frame,respectively. Place the middle clamps 8inches from the top and bottom clamps.



3 The calibration rig must incorporate ‘‘detents’’that ensure proper centering of both the calorimeter

and the thermocouple rake with respect to theburner cone, so that rapid positioning of these

devices can be achieved during the calibrationprocedure.

Note: For blanket materials that cannot beinstalled in accordance with figure 7 above,the blankets must be installed in a mannerapproved by the FAA.

(v) Conditioning. The specimens shall beconditioned at 70° ±5°F (21° ±2°C) and 55%+/-10% relative humidity for a minimum of24 hours prior to testing.

(d) Preparation of apparatus. (1) Level andcenter the frame assembly to ensurealignment of the calorimeter and/orthermocouple rake with the burner cone.

(2) Turn on the ventilation hood for the testchamber. Do not turn on the burner blower.Measure the airflow of the test chamber usinga vane anemometer or equivalent measuringdevice. The vertical air velocity just behind

the top of the upper insulation blanket testspecimen shall be 100 ±50 ft/min. Thehorizontal air velocity at this point shall beless than 50 ft/min.

(3) If a calibrated flow meter is notavailable, measure the fuel flow rate using agraduated cylinder of appropriate size. Turnon the burner motor/fuel pump, afterinsuring that the igniter system is turned off.Collect the fuel via a plastic or rubber tubeinto the graduated cylinder for a 2-minuteperiod. Determine the flow rate in gallons perhour. The fuel flow rate shall be 6.0 ±0.2gallons per hour.

(e) Calibration. (1) Secure the calibrationrig to the test specimen frame. Position theburner so that it is centered in front of thecalibration rig, and the vertical plane of the

burner cone exit is at a distance of 4 ±0.125inches (102 ±3 mm) from the calorimeterface. Ensure that the horizontal centerline ofthe burner cone is offset 1 inch below thehorizontal centerline of the calorimeter(figure 8). Without disturbing the burnerposition, slide the thermocouple rake portionof the calibration rig in front of the burner,such that the middle thermocouple (number4 of 7) is centered on the burner cone. Ensurethat the horizontal centerline of the burnercone is also offset 1 inch below thehorizontal centerline of the thermocoupletips.3 If individual calibration rigs are used,swing the burner to each position to ensureproper alignment between the cone and thecalorimeter and thermocouple rake.



(2) Position the air velocity meter in theadapter, making certain that no gaps existwhere air could leak around the air velocitymeasuring device. Turn on the blower/motorwhile ensuring that the fuel solenoid andigniters are off. Adjust the air intake velocityto a level of 2150 ft/min, then turn offblower/motor.

(3) Rotate the burner from the test positionto the warm-up position. Prior to lighting theburner, ensure that the calorimeter face isclean of soot deposits, and there is waterrunning through the calorimeter. Examineand clean the burner cone of any evidence ofbuildup of products of combustion, soot, etc.Soot buildup inside the burner cone mayaffect the flame characteristics and causecalibration difficulties. Since the burner conemay distort with time, dimensions should bechecked periodically.

(4) While the burner is still rotated out ofthe test position, turn on the blower/motor,igniters, and fuel flow, and light the burner.Allow it to warm up for a period of 2minutes. Move the burner into the testposition and allow 1 minute for calorimeterstabilization, then record the heat flux onceevery second for a period of 30 seconds. Turnoff burner, rotate out of position, and allowto cool. Calculate the average heat flux overthis 30-second duration. The average heatflux should be 16.0 +/¥0.8 Btu/ft2 sec.

(5) Position the thermocouple rake in frontof the burner. After checking for properalignment, rotate the burner to the warm-upposition, turn on the blower/motor, ignitersand fuel flow, and light the burner. Allow itto warm up for a period of 2 minutes. Movethe burner into the test position and allow 1minute for thermocouple stabilization, thenrecord the temperature of each of the 7thermocouples once every second for aperiod of 30 seconds. Turn off burner, rotateout of position, and allow to cool. Calculatethe average temperature of eachthermocouple over this 30-second period andrecord. The average temperature of each ofthe 7 thermocouples should be 1900°F +/¥100°F.

(6) If either the heat flux or thetemperatures are not within the specifiedrange, adjust the burner intake air velocityand repeat the procedures of paragraphs (4)and (5) above to obtain the proper values.Ensure that the inlet air velocity is within therange of 2150 ft/min +/¥50 ft/min.

(7) Calibrate prior to each test untilconsistency has been demonstrated. Afterconsistency has been confirmed, several testsmay be conducted with calibrationconducted before and after a series of tests.

(f) Test procedure. (1) Secure the twoinsulation blanket test specimens to the testframe. The insulation blankets should beattached to the test rig center vertical formerusing four spring clamps positioned asshown in figure 7 (according to the criteriaof paragraph (c)(4) or (c)(4)(i) of this part ofthis appendix).

(2) Ensure that the vertical plane of theburner cone is at a distance of 4 +/¥0.125inch from the outer surface of the horizontalstringers of the test specimen frame, and thatthe burner and test frame are both situatedat a 30° angle with respect to vertical.

(3) When ready to begin the test, direct theburner away from the test position to the

warm-up position so that the flame will notimpinge on the specimens. Turn on and lightthe burner and allow it to stabilize for 2minutes.

(4) To begin the test, rotate the burner intothe test position and simultaneously start thetiming device.

(5) Expose the test specimens to the burnerflame for 4 minutes and then turn off theburner. Immediately rotate the burner out ofthe test position.

(6) Determine (where applicable) theburnthrough time, or the point at which theheat flux exceeds 2.0 Btu/ft2-sec.

(g) Report. (1) Identify and describe thespecimen being tested.

(2) Report the number of insulation blanketspecimens tested.

(3) Report the burnthrough time (if any),and the maximum heat flux/temperature onthe back face of the insulation blanket testspecimen, and the time at which themaximum occurred.

(h) Requirements. (1) Neither of the twoinsulation blanket test specimens shall allowfire/flame penetration in less than 240seconds

(2) Neither of the two insulation blankettest specimens shall allow more than 2.0 Btu/ft2-sec on the cold side of the insulationspecimens at a point 12 inches from the faceof the test rig.

PART 91—GENERAL OPERATING ANDFLIGHT RULES

6–8. The authority citation for part 91continues to read as follows:

Authority: 49 U.S.C. 106(g), 40103, 40113,40120, 44101, 44111, 44701, 44709, 44711,44712, 44715, 44716, 44717, 44722, 46306,46315, 46316, 46502, 46504, 46506–46507,47122, 47508, 47528–47531.

9. Amend § 91.613 by redesignatingthe existing text as paragraph (a), andadding paragraph (b) to read as follows:

§ 91.613 Materials for compartmentinteriors.

* * * * *(b) Thermal/acoustic insulation

materials. For transport categoryairplanes type certificated after January1, 1958:

(1) For airplanes manufactured before[2 years after the effective date of thefinal rule], when thermal/acousticinsulation materials are installed asreplacements after [2 years after theeffective date of the final rule], thosematerials must meet the flamepropagation requirements of § 25.856 ofthis chapter, effective [insert final ruleeffective date].

(2) For airplanes manufactured after[2 years after the effective date of thefinal rule], thermal/acoustic insulationmaterials must meet the flamepropagation requirements of § 25.856 ofthis chapter, effective [insert final ruleeffective date].

PART 121—OPERATINGREQUIREMENTS: DOMESTIC, FLAG,AND SUPPLEMENTAL OPERATIONS


Authority: 49 U.S.C. 106(g), 40113, 40119,44101, 44701–44702, 44705, 44709–44711,44713, 44716–44717, 44722, 44901, 44903–44904, 44912, 46105.

11. Amend § 121.312 by addingparagraph (e) to read as follows:


* * * * *(e) Thermal/acoustic insulation


(1) For airplanes manufactured before[2 years after the effective date of thefinal rule], when thermal/acousticinsulation materials are installed asreplacements after [2 years after theeffective date of the final rule], thosematerials must meet the flamepropagation requirements of § 25.856 ofthis chapter, effective [insert final ruleeffective date].


(3) For airplanes manufactured after[4 years after the effective date of thefinal rule], thermal/acoustic insulationmaterials must meet the flamepenetration resistance requirements of§ 25.856 of this chapter, effective [insertfinal rule effective date].

PART 125—CERTIFICATION ANDOPERATIONS: AIRPLANES HAVING ASEATING CAPACITY OF 20 OR MOREPASSENGERS OR A MAXIMUMPAYLOAD CAPACITY OF 6,000POUNDS OR MORE


Authority: : 49 U.S.C. 106(g), 40113,44701–44702, 44705, 44710–44711, 44713,44716–44717, 44722.

13. Amend § 125.113 by addingparagraph (c) to read as follows:

§ 125.113 Cabin interiors.

* * * * *(c) Thermal/acoustic insulation


(1) For airplanes manufactured before[2 years after the effective date of thefinal rule], when thermal/acoustic



insulation materials are installed asreplacements after [2 years after theeffective date of the final rule], thosematerials must meet the flamepropagation requirements of § 25.856 ofthis chapter, effective [insert final ruleeffective date].


PART 135—OPERATINGREQUIREMENTS: COMMUTER ANDON-DEMAND OPERATIONS ANDRULES GOVERNING PERSONS ONBOARD SUCH AIRCRAFT


Authority: 49 U.S.C. 106(g), 40113, 44701–44702, 44705, 44709, 44711–44713, 44715–44717, 44722.

15. Amend § 135.170 by addingparagraph (c) to read as follows:


* * * * *(c) Thermal/acoustic insulation


(1) For airplanes manufactured before[2 years after the effective date of thefinal rule], when thermal/acousticinsulation materials are installed asreplacements after [2 years after theeffective date of the final rule], thosematerials must meet the flamepropagation requirements of § 25.856 of

this chapter, effective [insert final ruleeffective date].


Issued in Washington, DC, on September 8,2000.

Elizabeth Erickson,Director, Aircraft Certification Service.[FR Doc. 00–23550 Filed 9–19–00; 8:45 am]

BILLING CODE 4910–13–U


Documents

September 20, 2000