[Federal Register Volume 65, Number 103 (Friday, May 26, 2000)]
[Rules and Regulations]
[Pages 34322-34341]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-13149]



[[Page 34321]]

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Part V





Department of Transportation





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Federal Aviation Administration



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14 CFR Part 39



Airworthiness Directives; McDonnell Douglas Model DC-9-80 and MD-90-30 
Series Airplanes and Model MD-88 Airplanes; Final Rule



Airworthiness Directives; McDonnell Douglas Model DC-10-10F, DC-10-15, 
DC-10-30, DC-10-30F, and DC-10-40 Series Airplanes, and Model MD-11 and 
-11F Series Airplanes; Final Rule

Federal Register / Vol. 65, No. 103 / Friday, May 26, 2000 / Rules 
and Regulations

[[Page 34322]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NM-161-AD; Amendment 39-11749; AD 2000-11-01]
RIN 2120-AA64


Airworthiness Directives; McDonnell Douglas Model DC-9-80 and MD-
90-30 Series Airplanes, and Model MD-88 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to certain McDonnell Douglas Model DC-9-80 and MD-90-30 
series airplanes, and Model MD-88 airplanes, that requires a 
determination be made of whether, and at what locations, metallized 
polyethyleneteraphthalate (MPET) insulation blankets are installed, and 
replacement of MPET insulation blankets with new insulation blankets. 
This amendment is prompted by reports of in-flight and ground fires on 
certain airplanes manufactured with insulation blankets covered with 
MPET, which may contribute to the spread of a fire when ignition occurs 
from small ignition sources such as electrical arcing or sparking. The 
actions specified by this AD are intended to ensure that insulation 
blankets constructed of MPET are removed from the fuselage. Such 
insulation blankets could propagate a small fire that is the result of 
an otherwise harmless electrical arc and could lead to a much larger 
fire.

DATES: Effective June 30, 2000.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of June 30, 2000.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Aircraft Group, Long Beach Division, 
3855 Lakewood Boulevard, Long Beach, California 90846, Attention: 
Technical Publications Business Administration, Dept. C1-L51 (2-60). 
This information may be examined at the Federal Aviation Administration 
(FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, 
SW., Renton, Washington; or at the FAA, Transport Airplane Directorate, 
Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, 
Lakewood, California; or at the Office of the Federal Register, 800 
North Capitol Street, NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Robert Stacho, Aerospace Engineer, 
Systems and Equipment Branch, ANM-130L, FAA, Transport Airplane 
Directorate, Los Angeles Aircraft Certification Office, 3960 Paramount 
Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5334; 
fax (562) 627-5210.

SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to certain McDonnell Douglas Model 
DC-9-80 and MD-90-30 series airplanes, and Model MD-88 airplanes was 
published as a notice of proposed rulemaking (NPRM) in the Federal 
Register on August 12, 1999 (64 FR 43966). A second proposal that was 
identical to the NPRM, except that it affected additional airplanes, 
was published as a supplemental NPRM on November 17, 1999 (64 FR 
62613). Those actions proposed to require that a determination be made 
of whether, and at what locations, metallized polyethyleneteraphthalate 
(MPET) insulation blankets are installed, and replacement of MPET 
insulation blankets with new insulation blankets.
    Since the issuance of those NPRM's, the FAA has observed several 
prototyping exercises that involved the removal and replacement of MPET 
insulation blankets. The information obtained from these exercises 
assisted the FAA, operators, and manufacturer in understanding the 
technical details and impact of the requirements of this AD. Certain 
aspects of these prototype exercises will be discussed in the FAA's 
response to the comments received from the NPRM's.

Comments

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.
    The FAA has received comments in response to the NPRM's and 
supplemental NPRM's to Rules Docket No.'s. 99-NM-161-AD [applicable to 
certain McDonnell Douglas Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-
83 (MD-83), DC-9-87 (MD-87) series airplanes; Model MD-90-30 series 
airplanes; and Model MD-88 airplanes] and 99-NM-162--AD (applicable to 
certain McDonnell Douglas Model DC-10-30 and -30F series airplanes, and 
Model MD-11 and -11F series airplanes). Because in most cases the 
issues raised by the commenters are generally relevant to both NPRM's, 
each final rule includes a discussion of all comments received.

Support for Proposed AD's

    Several commenters support the intent of the proposed AD's; 
however, they request that some changes be made (discussed later).

Unsafe Condition

    One commenter states that, because the MPET insulation blankets 
only propagate the flame and are not the source of the flame, the 
proposed AD's should address the unsafe condition (i.e., source of the 
flame) rather than previously certified material (which met the 
flammability standard at one time) that is not creating the unsafe 
condition. The FAA does not concur. MPET insulation blankets, when 
ignited from a small ignition source, such as an electrical arc, can 
contribute to the spread of a fire. Such insulation blankets could 
propagate a small fire and lead to a much larger fire. Potential 
ignition sources exist in many areas of the affected airplanes. It is 
extremely difficult to determine where all potential ignition sources 
are. To provide the level of safety that is expected by the public for 
transport category airplanes, insulation blankets constructed of MPET 
must be removed. Therefore, the FAA finds that it has properly 
identified the unsafe condition (i.e., insulation blankets constructed 
of MPET) addressed by these AD's.
    The same commenter suggests that the subject blankets be handled as 
``attrition replacements,'' as intended in the original McDonnell 
Douglas service bulletins. The commenter states that, since cabin 
interior flammability has been addressed already to a large extent by 
the FAA, MPET insulation blankets could be treated comparably, and 
thus, integrated into the overall interior materials requirements. (The 
FAA infers that the commenter is referring to the provisions in 14 CFR 
section 121.312 related to ``substantially complete replacement of the 
cabin interior.'') These requirements not only mandate stricter new 
standards, but allow older airplane interiors to remain in service 
until a balanced decision is made to fully reconfigure the cabin. After 
that decision is made, the entire flammability rule must be met on 
these older airplane interiors, as well. The commenter argues that 
insulation blankets could be included, since the proposed requirements 
are in the same category of ``new flammability standards'' and do not 
address the actual ignition source.

[[Page 34323]]

    The FAA does not concur with the commenter's request to handle the 
subject blankets as ``attrition replacements.'' Attrition is 
appropriate for safety enhancements, not to correct identified unsafe 
conditions. There is a distinct difference between correcting an 
identified unsafe condition and enhancing safety. The intent of the 
interior material flammability enhancement was to provide occupants 
more time to evacuate an airplane before the cabin environment would 
become unsurvivable due to smoke and fire. The existing interior 
materials were not deemed unsafe, and therefore, could remain in 
service until the airlines needed to replacement them. With this 
action, as discussed above, the FAA finds that MPET-covered insulation 
material represents an unsafe condition that must be corrected. These 
AD's are a vehicle for ensuring that all affected operators perform the 
necessary actions that will address the identified unsafe condition. 
Therefore, these AD's are appropriate and warranted.
    One commenter expresses concern that, because the requirements of 
the proposed AD's are extremely costly and cumbersome, resources are 
being taken away from more effective measures for improving aviation 
safety. The commenter states that there are safety groups (both with 
wide aviation business basis) that have targeted the most important/
critical areas to be addressed. However, neither of these groups has 
fire on board as its top priority. The commenter interprets this to 
mean that the safety experts looking at statistical data would rather 
concentrate their efforts in other fields.
    While there may be groups that concentrate their efforts in other 
areas, the FAA has identified an unsafe condition that needs to be 
corrected (as discussed above). The activity referred to is primarily 
aimed at identifying areas for improved safety, and focusing resources 
on the most effective candidates. This is distinctly different from 
correcting an identified unsafe condition. Therefore, these AD's are 
appropriate and warranted.
    One commenter notes that in its experience most blankets are wet or 
soaking wet in a short time after coming out fairly dry (i.e., after 
extensive drying) during a heavy check. The commenter asks how it 
should explain to its mechanics that they have to replace wet blankets 
because of a fire hazard.
    The FAA infers from this comment that the wet blankets are a result 
of the atmospheric conditions in which the airplane is being operated 
or a result of moisture accumulation in the belly of the fuselage. As 
discussed above, the FAA has identified an unsafe condition on the 
affected airplanes that needs to be corrected. As addressed in the 
preambles of the NPRM's, the FAA has received reports of a number of 
in-flight and ground fires on in-service airplanes manufactured with 
insulation blankets covered with MPET, which can cause fire to spread 
from a small ignition source such as electrical arcing or sparking. The 
fact that insulation material itself may be wet may not prevent the 
MPET film material from propagating the fire to other combustible 
materials and causing a larger fire.
    One commenter states that the wording ``otherwise harmless 
electrical arcs'' in the Summary section in the preamble of the 
proposed AD's is misleading and requests that this wording be removed. 
The commenter reports that there has never been any Maintenance 
Steering Group (MSG) 3 testing on airplane wiring, and that no one 
other than the FAA has even evaluated the problems associated with 
momentary metal-to-metal contact of wires. In addition, the FAA has 
never evaluated the effects of spurious signals emitted from degraded 
wires that can affect flight control surfaces, autopilots, rudders, 
etc.
    The FAA does not concur with the commenter's request to revise the 
Summary section of the AD's. The term ``otherwise harmless arcs'' 
refers to an electrical arc that, on insulation films other than MPET, 
would not propagate a fire. In this case, the effect of the arc is 
negligible. In the case of MPET, an uncontrolled fire could develop. 
The FAA points out that these AD's do not address the aging wiring 
issues that can affect various systems. As discussed in the preamble of 
the NPRM's, the FAA is continuing to investigate various wiring 
problems on certain airplanes. In addition, the Aging System Task Force 
(ASTF) is continuing to investigate the need for specific aging wiring 
inspections and tests, as well as the potential effect on systems from 
degraded wiring. The actions required by this AD only address the 
identified unsafe condition (i.e., insulation blankets constructed of 
MPET). The FAA may consider additional rulemaking actions to address 
any other identified unsafe condition.

Risk Assessment

    Several commenters state that, in concert with the scheduled 
prototyping, a thorough risk assessment should be accomplished, 
particularly on the effects of replacing insulation blankets on the 
electrical (including wiring, cables, and installations), hydraulic, 
and mechanical systems. One commenter states that the risk assessment 
must be taken into account when mandating the scope and compliance of 
the proposed AD's. Several commenters state that a risk assessment is 
needed to determine whether areas exist where the risks associated with 
the replacement of MPET insulation blankets outweigh the benefits of 
replacing them. Risks inherent with disturbing airplane wiring and 
other permanently installed systems, particularly on the scale 
contemplated by the proposed AD's, are of primary concern. This and 
other related risks should be addressed using a structured method that 
considers the characteristics of MPET and alternative films, design and 
operation of overlying systems, susceptibility of those systems to 
damage during the replacement of insulation under proposed methods, and 
likely effects of any damage to those systems. One commenter states 
that the proposed AD's are not supported by such an analysis.
    The FAA does not concur that a formal risk assessment is necessary. 
If accomplished properly, the replacement required by this AD will not 
disrupt wiring in such a way as to adversely affect safety. Generally, 
the prototype exercises demonstrated that the required replacement can 
be accomplished safely. In addition, Boeing is revising the referenced 
service bulletins to provide additional guidance on techniques to 
ensure safe replacements. The primary reason for providing an extended 
compliance time for this AD, as discussed under the next heading, is to 
ensure that operators have adequate time to accomplish the replacements 
properly. On the other hand, MPET insulation blankets have been shown 
to create an unsafe condition that must be corrected. Furthermore, the 
FAA will require any operator/modifier that develops its own 
installation data to include specific instructions to ensure that any 
displaced wires, systems, and installations are in an airworthy 
condition after accomplishment of the required replacement. The FAA 
will monitor these areas of concern during the accomplishment of the 
insulation blanket installations. Finally, if operators can show that 
removal and replacement of MPET insulation blankets in certain areas of 
an airplane will create a greater risk of an unsafe condition than 
leaving the MPET blankets in place, the FAA will consider requests that 
provide an acceptable level of safety under the provision of paragraph 
(e) of the final rule. Any request to leave MPET insulation

[[Page 34324]]

blankets installed in an airplane must provide justification that the 
identified unsafe condition has been minimized and that an acceptable 
level of safety is maintained.
    One commenter states that the proposed AD's should be rewritten to 
limit the blanket replacement to areas of high risk, or conversely, 
retain existing blankets in areas with no wiring or with wiring deemed 
to pose little or no hazard.
    The FAA does not concur. No technical justification, criteria, or 
data were submitted to support the commenter's request. Potential 
ignition sources exist throughout the airplane and insulation blankets 
constructed of MPET film material are located throughout the airplane. 
It is, therefore, extremely difficult to identify high risk areas and 
areas of little or no risk. The FAA finds that MPET insulation blankets 
in all areas of the affected airplanes must be addressed.
    One commenter states that the requirements of the proposed AD's 
should be recast into phases so as to first respond across the 
worldwide fleet of affected airplanes to the areas of highest perceived 
risk. Thereafter, the areas of lesser perceived risk can be dealt with 
at a more appropriate pace. Targeting the highest perceived risk areas 
of the worldwide fleet of affected airplanes first would provide the 
greatest decrease in risk across the fleet most quickly. This approach 
also would make the best use of limited resources, lessen the 
substantial adverse impact to the traveling public of excessive fleet 
groundings, and somewhat reduce the substantial economic burden to the 
airlines.
    The FAA does not concur with the commenter's statement that the 
requirements of the final rule should be recast into phases. As 
discussed above under the heading ``Unsafe Condition,'' potential 
ignition sources exist in many areas of the affected airplanes. It is 
difficult to identify high risk areas and areas of little or no risk. 
Therefore, the FAA finds that MPET insulation blankets in all areas of 
the affected airplanes must be replaced. With the change in the 
compliance time from 4 to 5 years in this AD, excessive fleet grounding 
should not take place. Adequate maintenance facilities are available to 
complete this action within the required time period.

Compliance Time for Proposed Replacement of MPET Insulation 
Blankets

    Several commenters request that the compliance time for 
accomplishing the proposed replacement of the MPET insulation blankets 
be extended from the proposed 4 years to a range of 5 years to 8 years. 
The commenters state that such an extension will allow the replacement 
to be accomplished during a regularly scheduled ``D'' check or heavy 
maintenance visit, thereby eliminating any additional expenses that 
would be associated with special scheduling. The commenters express a 
concern about the availability of facilities and trained personnel, 
either domestically or offshore, to accomplish tasks of this magnitude.
    One commenter states that maintenance planning can only be done 
effectively once all details of the work to be accomplished and all 
downtimes needed to perform the work are known in detail. Therefore, 
the compliance time should only start once all these details have been 
clarified.
    One commenter states that the proposed AD's do not provide 
sufficient time for accomplishment of the prototyping effort. Wholesale 
removal or relocation of wiring not designed for removal in areas where 
access is difficult can lead to incidental damage even with the best 
maintenance practices. Given the problems of access, multiple blanket 
sections will now be required in many fuselage areas to replace a 
single original blanket. This will lead to new designs, templates, and 
part numbers. The commenter concludes that this cannot happen in an 
orderly fashion without completing a prototyping effort on at least one 
airplane.
    The FAA concurs that an extension to the compliance time is 
warranted. The FAA's intent was that the replacement be conducted 
during a regularly scheduled maintenance visit for the majority of the 
affected fleet, when the airplanes would be located at a base where 
special equipment and trained personnel would be readily available, if 
necessary. Based on the information supplied by the commenters, the FAA 
now recognizes that 5 years corresponds more closely to an interval 
representative of most of the affected operators' normal maintenance 
schedules. The FAA finds that a 4-year compliance time would have a 
significant impact on scheduling and cost and might result in hurried 
accomplishment of the required replacement, which could result in 
potential damage to associated wiring. This decision is supported by 
experience from the prototype installations, which demonstrated that 
the required replacement procedures are complex in some areas, and that 
adequate time and facilities are necessary to ensure that they are 
completed safely and correctly. Paragraphs (a) and (c) of the final 
rule have been revised to reflect a compliance time of 5 years. The FAA 
does not consider that this extension will adversely affect safety.
    One commenter supports the proposed 4-year compliance time for 
accomplishing the proposed replacement of the MPET insulation blankets. 
The commenter states that, while some operators feel it is not a 
practical time period, the proposed compliance time is reasonable and 
practical to retrofit all of the affected airplanes, utilizing airline 
and third party maintenance facilities. The commenter also states that 
it and other materials manufacturers are fully prepared and have the 
capacity to support this effort. Another commenter states that the 
proposed 4-year compliance time is a very generous allotment of time 
and would not want to see the proposed AD's delayed any further.
    The commenters did not provide any data to support their position. 
For the reasons described previously, the FAA finds that a 5-year 
compliance time is reasonable and practical to retrofit all of the 
affected airplanes rather than the 4-year compliance time proposed by 
the original NPRM and supplemental NPRM.
    Two commenters request that the compliance time for accomplishing 
the proposed replacement be shortened. One commenter states that the 
proposed compliance time of 4 years is too lengthy given the fire 
hazard introduced by MPET insulation blankets. The second commenter 
states that quicker action is necessary if the conditions of the wiring 
on affected airplanes are anything like what was discovered in the 
737's emergency grounding issue of May 98, wires found damaged on the 
Space Shuttle Columbia, or numerous instances of wire insulation 
failure coming out of the Aging Transport Systems Rulemaking Advisory 
Committee (ATSRAC)/ASTF inspections (15 service bulletins upgraded to 
alert status on Model MD-11 series airplanes alone) or alert service 
bulletins on the 727's.
    The FAA does not concur with the commenter's request to shorten the 
compliance time. As discussed previously, the FAA considered the safety 
implications, parts availability, and normal maintenance schedules for 
timely accomplishment of replacement of the MPET insulation blankets. 
In consideration of all of these factors, the FAA determined that the 
compliance time, as revised, represents an appropriate interval in 
which

[[Page 34325]]

replacement of the MPET insulation blankets can be accomplished in a 
timely manner within the fleet and still maintain an adequate level of 
safety. The FAA encourages operators to accomplish this modification as 
soon as possible. The commenter points out several incidents associated 
with airplane wiring. The FAA is addressing these issues as they are 
identified. The commenter is correct that these wiring incidents are 
the focus of ATSRAC and ASTF activity. However, these wiring issues are 
not the subject of this AD.
    One commenter requests that the FAA consider a 4-year compliance 
time to accomplish the proposed replacement only in areas that are 
readily accessible (i.e., areas where extraordinary means are not 
required to gain access). The MPET insulation blankets for certain 
defined areas of the cockpit and electronics bay(s) should not be 
replaced or should be replaced when those areas are made accessible. 
The commenter states that replacement of 98 percent of the insulation 
on the affected airplanes will provide an equivalent level of safety to 
those airplanes not affected by the proposed AD's. Considerable time 
will have to be added to the proposed compliance time to accommodate a 
complete replacement without forcing some airplanes to be grounded due 
to lack of maintenance capacity.
    The FAA does not concur with the commenter's request to require a 
compliance time of 4 years only for replacement areas that are readily 
accessible. Although the prototype installations have shown that 
accomplishment of the required replacement in the cockpit and 
electronic compartment is physically challenging, potential ignition 
sources and the identified unsafe condition exist in areas that are not 
readily accessible. Therefore, the FAA finds that MPET insulation 
blankets in all areas of the affected airplanes must be replaced. 
However, as discussed previously, the FAA has extended the compliance 
time for the required replacement from 4 years to 5 years. While not 
intended to address the issue of inaccessible areas, the extension of 
the compliance time by one year should help alleviate the concern for 
grounding of airplanes due to lack of maintenance capacity.
    Two commenters request that the FAA ensure that sufficient 
insulation material of appropriate quality is available. Supply 
shortages could create conditions in which the work needs to be 
performed under time pressure. One commenter notes that there is only 
one blanket covering material that is currently approved, and only one 
qualified test apparatus available for operators to perform American 
Society for Testing and Materials (ASTM) E648 tests on other products. 
The commenter also notes that the airplane manufacturer has stated that 
it has only one qualified supplier for manufactured blankets. The 
commenter is uncertain if the blanket manufacturer can meet replacement 
demands within the proposed 4-year compliance time. Furthermore, the 
commenter states that there are no dimensioned drawings available to 14 
CFR part 121 operators who might plan to fabricate their own blankets. 
Templates must be plotted and obtained from the airplane manufacturer, 
which is a time consuming process.
    Various insulation blanket material suppliers state that there is 
no cause for concern over the availability of the materials specified 
in the proposed AD's. Metallized Tedlar<SUP>TM</SUP> (i.e., 
polyvinylfluoride), polyimide film, Tedlar<SUP>TM</SUP> and polyimide 
tapes, and fiberglass are abundant and are readily accessible to 
support all retrofit requirements.
    The FAA has assessed the availability of materials required by this 
AD and has determined that required materials and manufacturing sources 
should be available for modification of the U.S. fleet within the 5-
year compliance time. The FAA encourages operators to review their 
airplanes to assess their individual needs for materials and plan 
accordingly. The FAA anticipates that operators will accomplish the 
requirements of this AD at the earliest practicable maintenance 
opportunity to lessen the burden toward the end of the compliance time. 
In addition, the airplane manufacturer is preparing installation kits 
that can be utilized to accomplish the required replacement. Also, 
operators and modifiers have developed and are continuing to develop 
their own data (templates and drawings) to accomplish this required 
replacement. While this may be a time consuming process for some, it 
can be accomplished.

Inadequate Procedures and Information in Referenced Service 
Bulletins

    Several commenters state that the replacement procedures and 
information specified in the referenced service bulletins (i.e., 
McDonnell Douglas Service Bulletins MD-90-25-015, Revision 01, dated 
November 5, 1997; MD80-25-355, Revision 01, dated November 5, 1997; 
DC10-25-368, dated October 31, 1997; and MD11-25-200, Revision 01, 
dated March 20, 1998) are inadequate for reasons discussed below.
    Several commenters state that the Accomplishment Instructions of 
the referenced service bulletins address the fabrication of insulation 
blankets but provide no instructions for installation. Detailed 
instructions for installation are essential to avoid risks during 
installation, particularly in crucial areas where wiring or other 
systems are densely concentrated. Damage to installed systems can 
result in latent failures of critical flight systems and generation of 
electrical ignition sources. The unprecedented scope of the work 
involved in moving and replacing wires and systems, and the fact that 
nothing similar has ever been attempted, introduce a new and 
unquantified amount of risk.
    One commenter states that Boeing has acknowledged that instructions 
to remove and reinstall some equipment racks and related structures, 
which are necessary to accomplish the proposed replacement, do not 
exist in current maintenance documents and will need to be developed. 
Specific aspects of the proposed replacement are beyond the scope of 
any currently authorized maintenance procedures. The members of the 
Boeing Recovery and Modification (RAM) Team are the only personnel 
trained and authorized to disassemble and reassemble certain critical 
areas. Several commenters state that Boeing is planning to issue 
revised service bulletins around June 2000. One commenter states that 
Boeing should issue detailed service bulletins to cover the scope of 
the NPRM's and all related test criteria and requirements associated 
with insulation blanket replacement and removal/installation of 
associated equipment/components. One commenter states that the service 
bulletins should be revised to include the above information.
    The FAA acknowledges that the instructions appear to be generic, 
without reference to specific locations in the airplane. However, it is 
still possible to complete the replacement required by this AD by 
developing the necessary installation data in conjunction with existing 
maintenance procedures. Since the issuance of the NPRM's, the 
manufacturer, in conjunction with operators, has completed prototype 
installations. Based on the results of the prototype, the manufacturer 
is developing revisions to the referenced service bulletins that will 
contain additional installation information and instructions. These 
revised service bulletins are scheduled for completion in June 2000. 
Any new or revised service bulletins will contain procedures to 
maintain/test the integrity

[[Page 34326]]

of the wiring after accomplishment of the replacement of any MPET 
insulation blanket. The FAA is planning to review and approve the 
revised service bulletins under the AMOC provision of paragraph (e) of 
the final rule.
    In addition, the FAA is aware that certain operators and modifiers 
are developing their own installation data. The FAA may approve 
requests for an AMOC under the provisions of paragraph (e) of this AD 
if sufficient data are submitted to substantiate that such a design 
change would provide an acceptable level of safety.
    The FAA does not concur with the commenter that the members of the 
Boeing RAM team are the only personnel that can address certain areas 
of the airplane. The FAA finds that many operators have the expertise 
to accomplish the required replacement. In addition, Boeing intends to 
include the necessary instructions in the revised service bulletins.
    Several commenters state that the referenced service bulletins not 
only refer to materials tested in accordance with Standard Test Method 
ASTM E648 and approved by the FAA as a method of compliance with the 
requirements of the proposed AD, but also refer to materials that do 
not meet the new requirements. Moreover, other materials acceptable for 
compliance with the requirements of the proposed AD are not listed in 
the referenced service bulletins.
    The FAA concurs that the referenced service bulletins refer to 
materials that do not meet the requirements of this AD. When the 
referenced service bulletins specified in the NPRM's were issued in 
1997, the insulation blanket film material listed in those service 
bulletins were considered acceptable for installation. Since the 
issuance of those service bulletins, however, only one of the two 
metallized Tedlar<SUP>TM</SUP> covers specified in the referenced 
service bulletins has been demonstrated to be acceptable for compliance 
with the replacement requirements of paragraph (c) of this AD (as 
indicated in NOTE 4 of the AD) based on flammability testing using the 
criteria specified in the final rule. The revised service bulletins 
will only list material that has been approved by the FAA. Under the 
provisions of paragraph (c) of this AD, the FAA may approve other film 
material that is shown to meet the flammability test method specified 
in the final rule. Also, under the provisions of paragraph (e) of this 
AD, the FAA may approve requests for approval of an AMOC for insulation 
blankets other than those specified in the service bulletins referenced 
in the final rule that are shown to meet the flammability test method 
specified in the final rule and all other airworthiness regulations.
    Several commenters state that, due to age, identification stamps on 
the MPET insulation blankets may be unreadable. The referenced service 
bulletins are missing instructions for determining whether such 
blankets are constructed of MPET.
    Although the referenced service bulletins are missing instructions 
for determining whether insulation blankets are constructed of MPET, 
the FAA finds that such a determination can be made without such 
instructions. MPET insulation blankets are extremely shiny when 
compared to all other insulation blanket cover material, and can be 
readily recognized by trained maintenance personnel. It is also 
possible to use known MPET material as a comparison sample to assist in 
the identification should the markings not be readable. Paragraph (a) 
of the final rule has been revised to clarify the method of identifying 
MPET. MPET insulation blankets can be identified by the following 
markings: (1) DMS 2072, Type 2, Class 1, Grade A; (2) DMS 2072, Type 2, 
Class 1, or (3) DMS 1996, Type 1. The FAA has revised NOTE 2 of the 
final rule to clarify these markings.
    Several commenters state that the referenced service bulletins 
specify the least effective method for the fabrication of new 
insulation blankets. Few operators are equipped or have the capability 
or capacity to manufacture their own blankets. Four sources of 
insulation blankets were evaluated in technical meetings with the 
manufacturer. Of these four sources, operators viewed blankets provided 
in kits by the manufacturer as the most efficient and practical. Such 
kits would facilitate the earliest completion date of a replacement 
program, would preserve the thermoacoustic characteristics of 
insulation systems and certificated configuration of affected 
airplanes, and can be supported according to the manufacturer. In 
addition, no dimensional blanket drawings and templates for making the 
blankets are available.
    Although the method for fabrication of new insulation blankets 
specified in the referenced service bulletins may not be the most 
efficient method for the commenters, the FAA finds that it is possible 
to develop the necessary data to manufacture blankets in accordance 
with the instructions of the referenced service bulletins. The FAA is 
aware that Boeing is developing replacement kits. The information 
necessary to purchase these kits will be included in the revised 
service bulletins (as discussed previously). However, the revised 
service bulletins are not scheduled to be completed until June 2000. 
The FAA has decided not to delay this action in anticipation of the 
service bulletins, since the release date is not absolute and this 
action is necessary to address an identified unsafe condition. 
Therefore, the FAA may approve requests for an AMOC under the 
provisions of paragraph (e) of this AD once the revised bulletins are 
issued.
    In addition, the FAA acknowledges that templates may not be 
available for operators to make new insulation blankets. However, the 
referenced service bulletins do describe procedures for removing the 
subject insulation blankets and using those blankets as templates for 
making new insulation blankets. While some operators may not be 
equipped or may decide not to manufacture the replacement blankets, 
there are adequate resources available in the industry to accomplish 
the manufacturing.
    Several commenters state that the referenced service bulletins 
provide no labor estimates. One commenter states that it is not aware 
of any large transport category airplane that has been removed from 
service, has had its insulation replaced, and has been returned to 
service. This lack of experience and labor estimates from the 
manufacturer would impair the planning required of operators and their 
ability to provide accurate comments to the proposed AD's.
    The FAA does not concur. The FAA acknowledges that the referenced 
service bulletins do not provide labor estimates. However, as indicated 
under the heading ``Regulatory Evaluation Summary'' in the preamble of 
the NPRM's and supplemental NPRM's, a Preliminary Cost Analysis and 
Initial Regulatory Flexibility Analysis to determine the regulatory 
impacts of the proposed AD's were included in the Rules Docket No.'s 
99-NM-161-AD and 99-NM-162-AD. A summary of those analyses was 
contained under that same heading in the preamble of the NPRM's and 
supplemental NPRM's. In addition, the manufacturer, operators, and 
modifiers have developed estimates based on the prototype installations 
completed to date. (The FAA discusses the comments to the cost estimate 
of the proposed AD's in more detail, below, under the heading 
``Regulatory Evaluation Summary.'')
    In response to the original NPRM's, several commenters state that 
the manufacturer has indicated that the airplane effectivity in the 
referenced service bulletins is currently being re-

[[Page 34327]]

evaluated and may be revised substantially. This lack of accurate 
airplane effectivity also would impair the planning required of 
operators and their ability to provide accurate comments.
    The FAA concurs that the effectivity listed in the service 
bulletins is not correct. As indicated under the heading ``Differences 
Between the Proposed AD and Service Bulletins'' in the preamble of the 
NPRM's, the FAA realizes that the effectivity listing of the referenced 
service bulletins not only includes airplanes manufactured with MPET 
insulation blankets, but airplanes equipped with other materials that 
are much more difficult to ignite than MPET. The FAA has determined 
that only airplanes manufactured with MPET insulation blankets are 
subject to the identified unsafe condition. Therefore, paragraph (a) of 
the AD's requires that a determination be made of whether, and at what 
locations, MPET insulation blankets are installed. In addition, the 
applicability specified in the final rules, based on the supplemental 
NPRM's, includes fewer airplanes than specified in the service 
bulletins. In addition, the applicability statement of the final rule, 
Rules Docket No. 99-NM-162-AD, has been revised to clarify the 
airplanes that are subject to the identified unsafe condition, which is 
discussed below, under the heading ``Revise Applicability of Proposed 
AD.''
    Several commenters state that some accessibility issues have not 
been addressed. One commenter requests that the removal/replacement 
requirements be re-evaluated to exclude replacement insulation blankets 
in those ``inaccessible places'' of the airplanes. Three to four 
percent of the MPET insulation blankets are buried beneath structure 
and wiring in areas like the electrical and equipment (EE) bay and the 
flight deck and will require as much as 70 percent of the total man 
hours to replace.
    The FAA does not concur that replacement of MPET insulation 
blankets should not be required in ``inaccessible'' areas. The areas 
identified by the commenters (i.e., the EE bay and flight deck) are 
areas where potential ignition sources (i.e., electrical arcing) are 
likely to exist and are, therefore, susceptible to the identified 
unsafe condition. During the prototype exercises and subsequent 
inspections of the EE bay and flight deck, the FAA learned that most 
Model DC-9-80 and MD-90-30 series airplanes do not have MPET insulation 
blankets in these areas. It is, however, the operator's responsibility, 
as required by paragraph (a) of this AD, to determine whether, and at 
what locations, MPET insulation blankets are installed in each 
airplane. Therefore, contrary to the commenters' assertion, the total 
labor costs associated with replacement of the MPET insulation blankets 
in the EE bay and flight deck will not be the most significant portion 
of the total cost of the AD.
    One commenter requests that the FAA revise the proposed AD to 
incorporate specific references to industry guidance material on wire 
inspection and disturbance. As a minimum, such references should 
include Advisory Circular 25-16, ``Electrical Fault and Fire Protection 
and Prevention.''
    The FAA does not concur. Operators and modifiers should be aware of 
the existing guidance and the revised service bulletin instructions 
(discussed above), which, based on the prototyping that has been 
accomplished, will specify wiring inspection information that may be 
needed.
    One commenter requests that the FAA develop and require post-
modification wiring inspections to verify the integrity of the wiring 
insulation. The FAA concurs that any damage done to wiring or other 
components in the course of the required replacement needs to be 
corrected. In fact, if maintenance personnel are aware of damage, 
whether or not caused by replacement of the MPET insulation blankets, 
they are obligated to document it and initiate appropriate corrective 
action. Operators are required by 14 CFR parts 91, 121, and 135 to 
maintain their airplanes in an airworthy condition after any alteration 
or repairs are made to the airplane. Also, based on the prototyping 
that has been accomplished, the revised service bulletins will provide 
any specific wire integrity inspection that may be needed. Therefore, 
no change to the final rule is necessary.

Coordination With Wiring AD's

    Several commenters state that they understand that other NPRM's are 
in the development phases, which would require inspection of airplane 
wiring, and would deal with the same issues that have brought about the 
subject proposed AD's. Some of these commenters state that these NPRM's 
should not be developed, mandated, and undertaken separately, but 
rather should be part of a carefully thought out and coordinated 
process and program. A properly developed plan must consider that each 
time such disruption of airplane wires/systems takes place, there is an 
increasing opportunity for collateral damage to those wire/systems with 
unknown future safety implications. Such a plan also should recognize 
that the insulation proposed to be changed is not really the source of 
any fire problem and that proper rectification of the issues being 
considered might better lie in a carefully thought out and researched 
wiring AD. One commenter states that it would be efficient to combine 
the requirements of the proposed AD's with the wiring requirements that 
will be proposed soon. One commenter states that Boeing is developing 
several service bulletins dedicated to the inspection and maintenance 
of airplane wiring. However, these service bulletins will not be 
available in time to coincide with the insulation blanket replacement 
should the current NPRM's, with their proposed timing, become law.
    The FAA does not concur that AD's addressing specific unsafe wiring 
conditions should necessarily provide for compliance times that are 
concurrent with this AD. In some cases, the corrective actions for 
those unsafe conditions are simple maintenance actions that can be 
accomplished quickly. It would be inappropriate to allow those unsafe 
conditions to continue during the extended compliance time allowed by 
this AD. The FAA does concur that any AD's addressing general wiring 
inspections for unsafe conditions would be best accomplished in 
conjunction with the replacement of MPET insulation blankets in 
affected areas. Such coordinated actions would certainly be most 
efficient for operators. The FAA does not concur with the commenters' 
request to combine the requirements of this AD with any proposed 
actions to address general wiring issues. Such action may delay 
correction of the unsafe condition of this AD by extending the 
compliance time further. The FAA will take into consideration the 
compliance time of this AD in any future action for general wiring 
inspection to minimize the duplication of aircraft downtime associated 
with accomplishing the actions of this AD.

Revise Applicability of Proposed AD

    One commenter notes that paragraph (a) of the proposed AD states 
``* * * determine whether, and at what locations, insulation blankets 
constructed of MPET are installed. This determination shall be made in 
a manner approved by the FAA.'' The commenter states that this wording 
is very unclear to operators and that the FAA should coordinate with 
Boeing to determine more precisely what the applicable airplanes are.
    Based on the commenter's statement that ``the FAA should coordinate 
with Boeing to determine more precisely

[[Page 34328]]

what the applicable airplanes are,'' the FAA finds that clarification 
is necessary. After inspecting in-service airplanes, the FAA has 
determined that all affected airplanes may not have MPET insulation 
blankets throughout the fuselage. Some airplanes may have very little 
MPET insulation blankets installed and others may have 100 percent 
installed. The FAA also has determined that, based on the 
manufacturer's records alone, it is not possible to determine precisely 
the configuration of each individual airplane. Therefore, paragraph (a) 
of the final rule requires that operators determine whether, and at 
what locations, insulation blankets constructed of MPET are installed. 
If MPET insulation blankets are not installed, no further action is 
required by this AD.
    The manufacturer states that it is continuing to verify the actual 
extent of MPET-covered insulation on airplanes delivered from the 
factory. In response to the original NPRM's, the manufacturer states 
that additional Model DC-9-87 (MD-87), DC-10, and MD-11 series 
airplanes, and KC-10A (military) airplanes need to be included in the 
applicability of the NPRM's, and at least some Model DC-9 series 
airplanes should be excluded. When that effort is complete, the 
manufacturer states that it will issue new service bulletin 
information. One commenter states that the applicability statement of 
NPRM, Rules Docket No. 99-NM-162-AD, is incorrect. The commenter states 
that the manufacturer has indicated that MPET insulation blankets were 
used on Model DC-10 series airplanes, fuselage numbers 359 through 381 
inclusive, and 432 through 436 inclusive, and Model MD-11 series 
airplanes, fuselage numbers 447 through 602 inclusive. In addition, 
MPET insulation blankets were used on ducting installed in Model MD-11 
series airplanes, fuselage numbers 603 through 632 inclusive.
    The FAA acknowledges that the applicability statement of the 
original NPRM's was incorrect. Following the issuance of the NPRM's, 
the FAA identified additional airplanes that were subject to the 
identified unsafe condition and issued supplemental NPRM's to reopen 
the comment period to provide additional opportunity for public 
comment. The applicability statement of the supplemental NPRM's 
included the fuselage numbers of the airplanes the commenter referred 
to above.
    One commenter states that the applicability statement of 
supplemental NPRM, Rules Docket No. 99-NM-162-AD, is incomplete. The 
commenter notes that it operates four Model DC-10-15 series airplanes, 
three of which fall within fuselage numbers 359 through 632 inclusive 
(i.e., fuselage numbers 362, 365, and 374), which were manufactured 
between June 1981 and January 1982. The commenter requests that the 
applicability statement of the supplemental NPRM be revised to include 
Model DC-10-15 series airplanes. The FAA concurs. The applicability 
statement of the subject supplemental NPRM correctly references the 
specific manufacturer's fuselage numbers of all affected airplanes, 
including those fuselage numbers for Model DC-10-15 series airplanes. 
Therefore, the FAA finds that it is necessary to revise the 
applicability statement of the subject final rule to include all 
affected series of Model DC-10 airplanes, specifically Model DC-10-10F, 
DC-10-15, and DC-10-40 series airplanes.
    One commenter requests that the applicability of NPRM, Rules Docket 
No. 99-NM-161-AD, be revised to ``[m]anufacturer's fuselage number 1011 
through 2241 inclusive; certified in common carriage operations.'' The 
commenter states that private operators were not considered when 
studying the effects of the proposed AD's. Private operators who 
operate under 14 CFR 91.501 need to be separately considered when they 
are faced with rules that are directed at air carriers. Transport 
category ``Private Carriage'' operators, who operate under 14 CFR 
91.501, are part of the general aviation population and do not offer 
service to the public or a segment of the public. General aviation 
operators' airplanes are not held (and are not expected to be held) 
accountable to the same regulation standards as ``Common Carriage'' 
operators. The commenter also states that significant differences in 
airplane utilization, interior, and operation make the likelihood of 
in-flight fire threat due to MPET insulation blankets on ``Private 
Carriage'' airplanes extremely remote. Therefore, the exclusion of 
``Private Carriage'' airplanes from the applicability of this NPRM 
would not jeopardize public interest.
    The FAA does not concur with the commenter's request to revise the 
applicability of the subject rule as stated. The identified unsafe 
condition and potential consequences addressed by this AD are not any 
different for airplanes utilized in private operation versus ones 
operated in common carriage.
    One commenter states that the proposed AD's do not address affected 
airplanes outside the noted applicability that may have been 
retrofitted with MPET insulation blankets during service. This implies 
that the FAA's investigation has determined that small amounts of MPET 
on those airplanes do not pose an unsafe condition.
    Regarding post-delivery installation of MPET, the FAA does consider 
that such insulation is unsafe. Most operators do not retain records 
identifying on what airplanes such insulation has been installed. 
Therefore, to address this unsafe condition, an AD would have to 
require that all operators inspect all airplanes of any type to 
identify the relatively small amount of such insulation that may have 
been installed during post-production maintenance. The FAA does not 
consider that such a requirement would be practical or cost effective. 
However, as with any other unsafe condition, when an operator becomes 
aware that MPET insulation blankets have been installed, the material 
should be removed to maintain the airplane in an airworthy condition.

Flammability Test Method Not Adequately Developed/Defined

    Several commenters state that the proposed test method seems 
insufficiently developed to be considered the new standard flammability 
test. The commenters addressed several issues, including:
    <bullet> The validity of the test method;
    <bullet> Qualification of the test method;
    <bullet> Details of the test procedures; and
    <bullet> Materials and approval process.

Validity of Test Method

    One commenter notes that it has built a test unit and conducted 
tests on it. The commenter has verified the results of the FAA 
Technical Center tests, but believes there are serious limitations on 
this test's utility for predicting how insulation coverings will burn 
when in place on an airplane. In addition, the commenter states that 
the mechanism by which films can pass the Radiant Panel Test is for the 
material to shrink away from the heat source. Other materials, such as 
polyimide film, pass the Radiant Panel Test by not igniting and 
shrinking away from the heat source. Two other commenters state that 
the best of Tedlar<SUP>TM</SUP> and Mylar<SUP>TM</SUP> (i.e., 3 
polyethyleneteraphthalate) films shrink away in the presence of flame 
and are no help at all in containing fire. The Tedlar<SUP>TM</SUP> 
material that passes the test shrinks away from the heat source before 
the ignition source can be applied to the surface of the test material. 
Thus, there is no material to ignite. The commenter states that the 
Radiant Panel Test may not replicate the condition on an airplane where 
blankets

[[Page 34329]]

are restrained and multiple layers are often part of the blanket 
construction.
    The commenter further states that it is possible for 
polyethyleneteraphthalate (PET), MPET, or other plastics that are more 
combustible than Tedlar<SUP>TM</SUP> to pass ASTM E648, if treated to 
have desirable heat shrink characteristics. The only other requirement 
for insulation coverings is the 12-sec vertical burn, which is 
recognized as inadequate because MPET materials can pass it. The 
commenter notes that the proposed standard may leave the door open in 
the future for combustible materials to be installed on airplanes.
    The FAA does not concur with the commenter's statement that films 
can pass the Radiant Panel Test by shrinking away from the heat source 
and are no help in containing a fire. The purpose of the test is to 
establish the flame spread characteristics of insulation blanket 
materials under realistic conditions. The results of this test have 
been correlated with full-scale testing, conducted by the FAA Technical 
Center, in which insulation was installed in fuselage sections in a 
representative fashion. Certain materials that shrink when exposed to 
heat have been shown to prevent propagation of a fire. In addition, for 
these same reasons, the FAA does not concur with the commenter that the 
FAA Technical Center tests have serious limitations. The FAA finds that 
the insulation material tested in accordance with the method specified 
in the AD will have much better flame spread characteristics than MPET, 
which was shown to comply with the current Bunsen Burner Test specified 
in the regulations, and subsequently, determined to have unsafe flame 
spread characteristics when ignited from a small ignition source.
    One commenter states that the best situation is to have insulation 
covering film that does not burn in the Radiant Panel Test. The 
commenter contends that the test should screen out material that does 
not perform as well as polyimide film.
    The FAA does not concur that the test method must screen out 
materials that do not perform as well as polyimide films. As discussed 
previously, materials, including polyimide films, that pass the Radiant 
Panel Test perform much better in full-scale testing than MPET 
insulation blankets that are the subject of this AD.

Qualification of the Test Method

    One commenter expresses concern that the FAA has not yet published 
updated flammability standards that will allow for the development and 
testing of materials other than those cited in previous McDonnell 
Douglas service bulletins, which specify the replacement of MPET with 
two types of metallized Tedlar<SUP>TM</SUP>. The commenter notes that 
the FAA has approved only one type of specified metallized 
Tedlar<SUP>TM</SUP> after it successfully passed an ASTM flame spread 
test. The commenter emphasizes that it is urgent that the FAA provide 
its own applicable test standard to facilitate the rapid replacement of 
MPET with other materials that will have superior fire resistant 
characteristics.
    One commenter requests that the FAA revise the proposed AD's to 
``more clearly require the FAA Radiant Panel Test, which was derived 
from ASTM E648,'' and to define the test before approving specific 
films. The commenter states that ASTM E648 is much different than the 
Radiant Panel Test developed by the FAA Technical Center. The Radiant 
Panel Test uses the same enclosure, a radiant panel, and the same basic 
concept as the ASTM E648 test. However, the Radiant Panel Test has had 
several modifications including a different heat flux, different 
ignition source, and a modified sample holder. The commenter notes that 
results of the Radiant Panel Test vary widely when test specifications 
are changed. Therefore, the specification of any film as passing the 
test prior to the completion of the test method is not warranted. It is 
possible for films that currently fail the existing test to pass when 
the test procedures or chamber is fully defined. Conversely, films that 
currently pass the test can fail.
    One commenter states that industry experts should discuss the 
success criteria of ASTM E648 further. This commenter notes that these 
changes to the standard and success criteria have not been subject to 
round robin testing and outside peer review, so various aspects of 
their merit are questionable. One commenter suggests that round robin 
testing with clearly identifiable/achievable pass/fail criteria be 
performed by the industry to validate the repeatability of the test 
procedures prior to release of the proposed AD's. Validated criteria 
would produce an equivalent level of safety to material currently in 
production and in use in the fleet, which is deemed acceptable.
    The FAA concurs with the commenters concerning the reference to 
ASTM E648 in the NPRM's and finds that clarification is necessary. The 
FAA has been developing for some time new flammability standards for 
insulation material. Research has been conducted on the various types 
of insulation material to determine their effectiveness on both flame 
spread and fuselage burnthrough. As a result, the FAA has developed a 
new flame spread test method. The flame spread test method specified in 
this AD is a modified version of the ASTM E648 flammability standard 
and test apparatus. Modifications to ASTM E648 test apparatus have been 
made to more closely reflect the fire conditions in an airplane 
environment. The FAA has prepared a document to reflect the flame 
spread test method to be used for testing of replacement insulation 
blankets for this AD. It is identified as ``Test Method to Determine 
the Flame Spread Characteristics of Thermal/Acoustic Insulation 
Material for Replacement of MPET.'' For the purposes of correcting the 
identified unsafe condition of this AD, the FAA finds that this flame 
spread test method is sufficiently developed.
    The FAA also has developed a procedure for utilizing the FAA 
Technical Center flame spread test apparatus to qualify materials for 
this AD. The procedure for utilizing the test apparatus of the FAA 
Technical Center is identified as ``Ground Rules for Use of Technical 
Center Facility for Testing.''
    The flame spread test method and procedure for using the FAA 
Technical Center test apparatus are both included in Appendix 1 of this 
AD.
    As paragraph (c) of the NPRM's is currently worded, some commenters 
may misinterpret that the replacement insulation blankets must be 
constructed of materials tested in accordance with the original ASTM 
E648 flammability standard, rather than tested in accordance with a new 
flame spread test using an apparatus derived from ASTM E648 in 
accordance with a method approved by the FAA. Paragraph (c) of the 
final rules has been revised to clarify the flame spread test method 
for replacement insulation blankets. The Los Angeles Aircraft 
Certification Office (ACO) will work closely with other FAA ACO's and 
the FAA Technical Center to assist operators/modifiers in qualifying 
new materials for compliance with the requirements of this AD.
    The FAA concurs that the method specified is not yet a 
``standard.'' However, the method is sufficiently developed for this AD 
and, before adoption as a standard, will undergo the kind of industry 
qualification proposed by one commenter. The FAA partially concurs with 
the commenter's statement that round robin testing is necessary and 
that the success criteria of the flame spread test method should be 
discussed further. Prior to incorporation of a new flame spread test 
method into the

[[Page 34330]]

Airworthiness Standards for transport category airplanes (14 CFR part 
25), the test method will be subject to round robin testing. In fact, 
this process is currently underway within the International Aircraft 
Materials Fire Test Working Group.
    With respect to changes in the flame spread test method that may 
cause certain materials to go from acceptable to unacceptable, or vice 
versa, the FAA does not agree that this is an issue. Refinements to the 
test method will be made to improve the repeatability of the test, not 
to change the test results. Materials that are marginal will perform 
marginally regardless of the details of the method.
    One commenter states that it understands that the FAA has plans to 
replace the standard gas-fired radiant panel with an electric panel, 
and that the flame ignition source is a single cone non-standard burner 
as opposed to the T-type burner method specified in ASTM E648. The 
commenter contends that differences between the FAA method and ASTM 
E648 are confusing to both testing labs wishing to provide services to 
FAA-regulated clients as well as suppliers of insulation who are 
unclear as to what the specification will be for the products they 
produce for the aerospace industry. The commenter states that 
``specification of a non-standard test apparatus and conditions by the 
FAA end up creating a whole other set of devices which must be 
fabricated and maintained separately from their standard `parent 
devices' removing the economic benefits which use of consensus 
developed public sector standards provide.''
    The FAA does not concur for the reasons noted previously. In 
addition, since the apparatus specified is not used for any other 
aviation application, there is very little potential for confusion. The 
number of facilities currently equipped to conduct these tests is 
extremely small, which further diminishes any problems associated with 
differences in the test method.
    One commenter states that, because of such a tremendously costly 
retrofit program, all further developments with regard to new testing 
methods must clearly avoid duplication or contradiction of actions as 
described in the proposed AD's.
    The FAA has revised paragraph (c) of the final rule to clarify the 
flame spread test method to be used to qualify replacement insulation 
blankets. As previously discussed, this test method is adequately 
refined to qualify these materials for this AD.

Details of the Test Procedures

    One commenter states that results of tests have shown that the 
thickness of the insulation has no impact on the performance of the 
film under test. Therefore, the commenter suggests that all samples be 
tested with two-inch thick insulation.
    One commenter requests that the FAA develop specifications for 
environmental conditioning of samples since the absence of such 
requirements will significantly alter test results, in particular for 
ignition and flame spread sensitive materials such as faced insulation.
    The commenter states that the proposed pass/fail criteria, 
including the minimum 2-inch burn length and 0 flame spread, are not 
easily measured or agreed upon. Several commenters state that clearer 
pass/fail criteria are needed. One commenter states that subjective 
assessment of test results in small scale fire testing is a constant, 
ongoing problem that should be avoided.
    One commenter claims that the ``pilot'' burner arrangement called 
out in the FAA specification does not result in reproducible test 
results. Likewise, the ``pre-heat'' time between specimens and the time 
between sample insertion and flame application have not been defined. 
The commenter prefers a standard design and operation conditions and is 
unclear why the standard design has been modified.
    The FAA does not agree that the current test method lacks 
reproducibility. Tests conducted at the FAA Technical Center and at 
other facilities indicate that the test is reproducible and repeatable. 
The FAA concurs with the commenter that a defined test protocol should 
be used when testing replacement material. The flame spread test method 
specified in the final rule does include the pass/fail criteria, 
environmental conditioning, and test specimen thickness. Issues such as 
the pilot burner arrangement will be the subject of further refinement 
before the test method is adopted as a regulatory standard, but are 
adequately defined for this AD.
    One commenter requests that the test procedures include 
contaminated insulation blankets to simulate real world conditions. The 
commenter states that testing of pristine material may not provide 
sufficient assurance when within a few years the thermal blankets will 
be contaminated with solvents and other material. The FAA does not 
concur. While ``contamination'' might result in either detrimental or 
improved flammability performance, incorporation of generic 
``contamination'' into a test requirement is not practical. 
Contamination is usually a localized phenomenon, and not spread 
uniformly throughout the airplane. Replacing the existing materials 
with materials that will not propagate a fire will confine a fire to 
the area of contamination and should prevent the fire from becoming a 
hazard. As with any material installed on an airplane, it is the 
operator's responsibility to ensure that the airplane remains in an 
airworthy condition.
    The commenter further requests that the test procedures include 
ignition ``by these so-called, otherwise harmless electrical arcs.''' 
The commenter states that the likelihood of thermal blankets 
propagating a fire will typically start with an electrical arc. 
Therefore, the resistance to an arc-tracking Kapton<SUP>TM</SUP> (i.e., 
polyimide) wire fire should be assessed. The commenter contends that 
this will give a clear indication of what the next flight crew might 
experience, rather than a Bunsen Burner or cotton swab test that 
doesn't relate to the real world conditions found on affected 
airplanes.
    The FAA does not concur with the commenter's request to include 
electrical arcing ignition in the test procedures. Electrical arc tests 
were used to identify the unsafe characteristics of MPET in the course 
of research. The test method required by this AD is, in fact, a more 
severe measure of the materials' performance. There are materials that 
are not susceptible to ignition by electrical arcing that will not pass 
the test required by this AD. Therefore, the replacement of MPET 
insulation blankets in accordance with this AD will address the 
commenter's concern.

Approved Materials

    Two commenters request that the FAA revise the proposed AD's to 
include an expanded list of approved films. Several commenters note 
that Kapton<SUP>TM</SUP> film installed 25 years ago on Model L-1011 
series airplanes has proven to outperform Tedlar<SUP>TM</SUP> and 
Mylar<SUP>TM</SUP> films in FAA tests, which measure the materials' 
ability to hold back flames. Two commenters state that all FAA testing, 
including burnthrough testing, have shown polyimide films to be 
superior. In addition, FAA Administrator, Jane Garvey, specifically 
mentioned Kapton<SUP>TM</SUP> film as being a material that would be 
``grandfathered in'' in an October 14, 1998, announcement.
    Two commenters state that the proposed AD's appear to preclude the 
use of polyimide (Kapton<SUP>TM</SUP>) insulation

[[Page 34331]]

covering film that has passed the new Radiant Panel Test.
    The FAA does not concur with the commenters' request to revise NOTE 
4 of the AD to include additional films. Except for the metallized 
Tedlar<SUP>TM</SUP> cover mentioned in NOTE 4 of the AD, currently, no 
other film has successfully passed the flammability testing in a manner 
approved by the Manager, Los Angeles ACO. However, the FAA is aware of 
various film materials that could be found to be acceptable replacement 
materials for MPET. Once these materials have successfully passed the 
flammability testing specified in the AD, they must be approved by the 
Manager, Los Angeles ACO. In addition to the flammability requirements, 
the material must be shown to meet all other applicable airworthiness 
requirements. The FAA Administrator did make an announcement in October 
1998 that Kapton<SUP>TM</SUP> would be ``grandfathered,'' and that the 
FAA would not require that material to be replaced once is was 
installed. However, that announcement was made prior to the issuance of 
the NPRM for this final rule. This AD does NOT require 
Kapton<SUP>TM</SUP> to be replaced once it is installed; however, it 
does require testing and approval of any material, including 
Kapton<SUP>TM</SUP>.
    One commenter requests that the FAA revise NOTE 4 of the proposed 
AD's to read ``[t]he metallized Tedlar covers specified in the service 
bulletins must be tested to demonstrate compliance with the 
requirements of paragraph (c) of this AD.'' The commenter disagrees 
with the characterization that a particular cover material is 
considered acceptable with the requirements of paragraph (c) of the 
proposed AD's. The commenter states that the Thermal Acoustic Task 
Group, which was organized by the Fire (Safety) Test Branch of the FAA 
Technical Center to develop the new flammability requirements, did not 
begin to discuss the procedures for demonstrating compliance until a 
seminar was held on September 13 and 14, 1999. Because the release date 
of the NPRM's was before the seminar, no material could have been 
specified to be in compliance with the requirements of paragraph (c) of 
the NPRM's. The commenter states that, at the time of publication of 
the proposed AD's, compliance materials and methods had not yet been 
submitted under a Test Plan, conformity inspection of samples had not 
been completed, and properly witnessed testing had not taken place.
    The FAA does not concur with the commenter's request to revise NOTE 
4 of the AD as it suggests. The material that is listed in the service 
bulletins has been found acceptable by the FAA and was tested at the 
FAA Technical Center in a manner approved by the FAA, prior to the 
September seminar. The purpose of the seminar was not to develop test 
methods, but to introduce the method to the interested segment of the 
industry. Therefore, the timing of the seminar has no bearing on the 
approval status of the material. No change to the final rule is 
necessary.

Replacement Material Approval Process

    One commenter notes that under the heading ``Differences Between 
the Proposed AD and Service Bulletins'' in the preamble of the NPRM's, 
it states ``* *  * Only one of the two insulation blanket film 
materials specified in the service bulletins has successfully passed 
the testing of the ASTM flammability standard and has been found to be 
an acceptable replacement material for the MPET-covered insulation 
blankets. Other film material, such as certain polyimide and 
fluoropolymer composites, also have been successfully tested to ASTM 
E648 and could be found to be acceptable for compliance with the 
requirements of this proposed AD if presented to the FAA for approval. 
These materials are not listed in the service bulletins described 
previously.'' The commenter claims that the original equipment 
manufacturer (OEM) and certain operators are interpreting this 
statement as requiring a full Part Manufacturing Approval (PMA) and 
Supplemental Type Certificate (STC) approval process for blankets using 
films not in the referenced McDonnell Douglas service bulletins.
    One commenter states that other new materials besides 
Kapton<SUP>TM</SUP> will become available in the near future for use as 
insulation coverings, and that the PMA/STC process is not designed for 
nor suited for purely materials testing. The commenter contends that 
using this process would add a great deal of unnecessary cost to the 
current approval process for new materials. Another commenter requests 
that the proposed AD be revised to include language describing a clear 
and abbreviated approval process for blankets utilizing new and less 
flammable materials.
    The FAA does not concur with the commenter's request to include 
language describing the process for approval of replacement insulation 
blankets utilizing new and less flammable materials. The FAA approval 
process of replacing materials/installations is well established and 
known. Design approval can be obtained by an STC or PMA. It is the 
responsibility of the operators and modifiers to obtain such approvals 
for any proposed materials under paragraph (c) of the AD. The FAA may 
approve requests for AMOC's, such as alternative blanket installation, 
under the provisions of paragraph (e) of this AD if sufficient data are 
submitted to substantiate that such a design change would provide an 
acceptable level of safety.
    The FAA has determined that an adequate supply of approved 
replacement materials will be available to comply with this AD in the 
time specified. Operators that choose to develop new or different 
materials must plan accordingly and obtain approval as previously 
stated. While the PMA or STC process may not seem to be cost effective 
for some operators, it is the proper approval method to assure all 
airworthiness standards are met.

Insulation Material on Other Aircraft

    One commenter is not clear if the material used today on other 
Boeing airplanes is able to pass ASTM E648. The same commenter also 
states that the proposed AD's require full replacement of only MPET. 
The commenter is not clear what the rationale behind this decision is.
    As discussed in the NPRM's, these AD's are intended to correct an 
unsafe condition by replacing MPET insulation blankets. MPET film 
differs from other films in use in that it is susceptible to 
propagation of a fire from a small ignition source. Other films, while 
not necessarily meeting the proposed test requirements, do not have 
this susceptibility. It is the susceptibility to small ignition sources 
that creates the unsafe condition. New standards for insulation 
materials in general may be similar to the requirements of this AD, but 
will be used to upgrade the level of safety, and not correct an unsafe 
condition.

Burnthrough

    Several commenters request that the FAA revise the proposed AD's to 
make clear that airlines are permitted to install insulation that meets 
a burnthrough protection standard. Two commenters state that the 
proposed AD's appear to preclude the use of Curlon as a substitute for 
fiberglass to achieve burnthrough performance. One commenter states 
that Curlon material and many other materials recently developed could 
easily and economically provide double the level of protection of the 
current burnthrough time (i.e., four minutes). Although the proposed 
AD's do not address the

[[Page 34332]]

burnthrough safety threat, the commenters want to take this opportunity 
to achieve this important safety advance when replacing the insulation. 
The commenters reemphasize that this would simply be reinforcing the 
October 1998 announcement that Curlon would be one of the materials 
``grandfathered in,'' if operators proceeded to install it voluntarily.
    Two commenters request that the FAA revise the proposed AD's to 
include requirements for burnthrough protection from fuel fires on the 
ground for all affected airplanes. The commenters state that 
replacement of flammable insulation is an opportunity to install 
burnthrough protection. One commenter states that this should be the 
time to push the industry, as was done with the heat release 
requirements for interior materials a few years ago. Materials were not 
even available to meet the new FAA requirements, but the industry 
``stepped up to the plate and we now are all safer as a result of this 
proactive approach.''
    The FAA does not concur with the commenters' requests to include 
burnthrough requirements in the AD. While burnthrough protection is 
important to the overall fire resistance of airplanes following an 
accident, the actions required by this AD are intended to correct a 
known unsafe condition--insulation blankets constructed of MPET. The 
FAA does not consider that the degree of burnthrough protection 
provided by currently installed insulation constitutes an unsafe 
condition. Therefore, it would be inappropriate to issue an AD to 
require improvement in burnthrough protection. The new replacement 
insulation blankets required by this AD meet the test method specified 
in the final rule, correct the identified unsafe condition, and provide 
the level of safety required by 14 CFR part 25. The FAA encourages the 
installation of materials that meet additional standards such as 
fuselage burnthrough protection.

Trade Names

    One commenter opposes the use of trade names in both the preamble 
and regulatory text of the proposed AD's and considers such references 
to trade names highly prejudicial to Chemfab, the manufacturer of 
Chemfilm. The commenter states that there is no need for brand name 
product identification and that this connotes not only FAA approval of, 
but also preference for, the identified product brand. Once the 
official ``seal of approval'' has been granted through the rulemaking 
process, other market entrants face a significant barrier in gaining 
customer acceptance simply because the identified product has been 
``officially'' sanctioned.
    Because of the publication and circulation of the proposed AD's, 
two commenters request that the FAA revise the proposed AD's to 
identify the manufacturer(s) and trade names of insulation blanket 
covering films that have met FAA requirements specified in the proposed 
AD's.
    The FAA does not concur with the commenters' request to reference 
other trade name products in the final rules or to eliminate all 
references. Tedlar<SUP>TM</SUP> and Mylar<SUP>TM</SUP> are common trade 
names and this is the clearest way for FAA to communicate with affected 
operators. Except for the one metallized Tedlar<SUP>TM</SUP> cover 
mentioned in NOTE 4 of the AD, currently, no other film has been 
approved by the Manager, Los Angeles ACO. In addition, the airplane 
manufacturer is planning to list materials, once they have been tested 
and approved by the FAA, in the revised service bulletins (discussed 
previously under the heading ``Inadequate Procedures and Information in 
Referenced Service Bulletin''). Furthermore, the FAA finds that trade 
names such as of Mylar<SUP>TM</SUP>, Kapton<SUP>TM</SUP>, and 
Tedlar<SUP>TM</SUP> are well known and are accepted terminology in 
industry. The reference of these trade names in the AD's are not, in 
any way, an FAA endorsement of those products. Therefore, no change to 
the final rule is necessary.

Wiring

    One commenter requests that flammability requirements for the 
sources of ignition (i.e., the wiring) for thermal blanket fires be 
stricter than the requirements for thermal blankets themselves. The 
commenter states that the 60-degree flame test--the only test required 
by the FAA for the wiring on commercial airplanes--should be replaced 
immediately with the vertical flame test as a minimum requirement, and 
that every type of wire insulation in all airplanes should have to meet 
it.
    The FAA does not concur. The current flammability standard for 
wiring has not been determined to be inadequate. The actions required 
by this AD are intended to address an identified unsafe condition, 
which is that MPET-covered insulation blankets can contribute to the 
spread of a fire when ignition occurs from a small ignition source such 
as electrical arcing or sparking. As noted previously, the FAA has a 
major program underway to address issues related to airplane wiring and 
problems are being addressed as they are identified.

Corrosion Protection

    One commenter states that for Model MD-11 series airplanes to be 
afforded the same corrosion protection offered by the OEM installation, 
any fabricated blankets must meet the original type design. The 
existing Corrosion Prevention and Control Program (CPCP) requirements 
are based on the performance of the insulation system. Any compromise 
or alteration will necessitate changes to the CPCP. Many insulation 
blankets cannot be installed as they originally were due to 
installation of overlying structure. Therefore, deviations to the type 
design will have to be approved by the OEM and FAA in the form of an 
AMOC. The burden of these approvals will stress the resources of the 
OEM and FAA over the duration of the compliance period.
    The FAA does not concur. The FAA is aware of the potential effects 
of changing insulation material has on the corrosion protection of the 
affected airplanes. The airplane manufacturer intends to take this into 
account so that no change to the CPCP is required. Any operator or 
modifier also will be required, under paragraph (e) of this AD, to 
address any ramifications to the CPCP in any request for an AMOC.

Add New Inspection

    One commenter requests that, if it is determined that an insulation 
blanket is not constructed of MPET during the action required by 
paragraph (a) of the proposed AD's, a visual inspection be conducted to 
detect fire damage, electrical arcing, discoloration, or other physical 
damage. The commenter also requests a visual inspection for possible 
ignition sources during routine maintenance on airplanes not affected 
by the proposed AD's.
    The FAA does not concur with the commenter's request to revise 
paragraph (a) of the final rule to include a visual inspection for 
possible ignition sources. If any evidence of fire damage is found 
during the subject inspection, operators are already required to 
investigate and determine the source of the problem. This is no 
different from any other maintenance action that is performed by the 
operators. It is not necessary to include any additional requirements 
in this AD to accomplish this action.

Alternative Method of Compliance

    One commenter states that it has developed a system whereby the 
existing bagged insulation can be removed from the airplane without the 
necessity of interfering with wiring

[[Page 34333]]

harnesses or other unrelated systems. The commenter claims that its 
system would reduce the installation time of the proposed AD's, reduce 
the cost of compliance, and reduce the remote chances of creating 
future related AD's caused by the method of compliance. Another 
commenter states that it also has developed an insulation system that 
works around existing equipment and thus eliminates the need to remove 
much of the equipment that is not normally removed during heavy 
maintenance checks. The commenter claims that its system is lighter in 
weight than the OEM insulation system and will result in fuel savings.
    One commenter agrees that the flammability/flame spread performance 
of the MPET-covered insulation blankets should be improved, but 
questions proposed AD's that would require blanket replacement. The 
commenter states that this approach may not be the only possible method 
of addressing the issue. This concept is especially important 
considering the potential negative consequences of required airplane 
disassembly to accomplish the blanket replacement. The commenter 
suggests that there may be other options such as spray coatings that 
offer virtually equivalent performance with little negative impact.
    From these comments, the FAA infers that the commenters are 
requesting that the final rules be revised to include the commenter's 
systems for replacing or modifying the MPET insulation blankets. The 
FAA does not concur. The commenters did not provide any technical 
details for the FAA to make a finding. Paragraph (e) of the final rule 
contains provisions for requesting approval of an AMOC to address these 
types of unique circumstances.
    One commenter requests that the FAA require installation of 
additional fire resistant material(s) between the insulation blankets 
and any adjacent wires, wire bundles, or other potential ignition 
sources instead of removing and replacing MPET insulation blankets. The 
commenter also requests that the FAA consider this approach on either a 
full or partial basis. Another commenter believes that fire resistant 
material(s) in such a location would better promote the overall safety 
of the affected airplanes.
    The FAA acknowledges that this suggestion may be a possible 
acceptable alternative to removing the existing insulation blankets. 
However, no change to the final rule is necessary. Under paragraph (e) 
of the AD, operators may apply for the approval of an AMOC or 
adjustment of the compliance time that provides an acceptable level of 
safety.

Communication

    One commenter requests that the FAA have a public meeting regarding 
the proposed AD's. The commenter states that, because many vendors are 
trying to develop materials that meet the new FAA requirements, and the 
market price of these materials seems to vary drastically at present, 
it just has insufficient information on new materials.
    The FAA does not concur that a public meeting regarding the 
proposed AD's is necessary. Through the FAA Technical Center, the FAA 
has provided a forum to develop flammability standards for insulation 
materials. In addition, the FAA is aware of a number of meetings hosted 
by the airplane manufacturer to provide information to operators 
affected by the requirements of this AD. The FAA is sensitive of the 
public's concern with the fire safety issues associated with this AD 
and is aware of the effects this AD will have on operators. The FAA has 
determined that an unsafe condition exists, and that the actions 
required by this AD are necessary in order to ensure the continued 
safety of the affected fleet.

Extend Comment Period of NPRM's, Delay Issuance of Final Rules, and 
Withdraw NPRM's

    For the reasons described above, several commenters request that 
the FAA do one or more of the following: (1) Extend the public comment 
period for the NPRM's and supplemental NPRM's; (2) delay issuance of 
the final rules; or (3) withdraw the NPRM's and combine them with the 
draft burnthrough NPRM. (The FAA infers that the commenters are 
referring to a draft NPRM relating to insulation blanket flammability. 
The FAA announced its intention to develop new flammability standards 
for thermal/acoustic insulation in October 1998. This announcement 
included mention of improved burnthrough protection.)
    One commenter states that it is not uncommon, in the case of an AD 
relating to issues not as complex as the proposed AD's, for the FAA to 
allow 90 days or more to comment. The 45-day comment period of the 
proposed AD's does not allow for proper understanding and evaluation on 
which to develop reasonable comments.
    The FAA does not concur with the commenters' request to extend the 
comment period. On November 10, 1999, the FAA issued supplemental 
NPRM's to reopen the comment period for an additional 25 days to 
provide opportunity for public comment (the comment period for the 
NPRM's was 45 days and closed on September 27, 1999). The FAA finds 
that the public has had a reasonable opportunity to comment on the 
substance of the AD's. The FAA does not concur with the commenter's 
statement that it is not uncommon for the FAA to allow 90 days or more 
for the public to comment on proposed AD's. The standard comment period 
is 45 days for NPRM's and 25 days for supplemental NPRM's in which the 
FAA has responsibility as the State of Design of the affected 
airplanes. A 90-day comment period would be uncommon.
    As discussed above in ``Inadequate Procedures in Referenced Service 
Bulletins,'' the FAA also finds that it is possible to accomplish the 
requirements of this AD. Since the issuance of the NPRM's, the airplane 
manufacturer, in conjunction with operators, has completed the 
prototype installations. Based on the results of these installations, 
the airplane manufacturer is developing revisions to the service 
bulletins referenced in the AD's to include detailed instructions for 
accomplishment of the required replacement. These revised service 
bulletins are scheduled for completion in June 2000. Any new or revised 
service bulletins, among other items, will contain procedures to 
maintain/test the integrity of the wiring after accomplishment of the 
replacement of any MPET insulation blanket. These revised service 
bulletins will be approved as an AMOC for the requirements of this AD.
    The FAA does not concur with the commenter's request to delay 
issuance of the final rules. These revised service bulletins are 
scheduled for completion in June 2000. The FAA has determined that, 
while physically challenging, the actions required by the AD can be 
accomplished within the 5-year compliance time, and that the actions 
are warranted to address an identified unsafe condition.
    In support of its request to withdraw the NPRM's, one commenter 
contends that other rulemaking in development by the FAA may eventually 
affect the airplanes covered by this AD, thereby requiring two 
extensive modifications.
    The FAA does not concur with the commenter's request to withdraw 
the NPRM's and combine them with the draft burnthrough NPRM. Any other 
regulatory action to raise the level of safety would have to be 
justified and subject to public comment. The FAA does not anticipate 
requiring airplanes to be modified twice as a result of future actions. 
The actions required by this AD are intended to correct an identified 
unsafe condition by removing MPET insulation blankets from airplanes

[[Page 34334]]

affected by these AD's. These actions are not intended to provide a 
general upgrade to the current level of safety specified in the 
airworthiness regulations. Therefore, the actions required by these 
AD's are warranted.
    One commenter disagrees that prototyping efforts are necessary to 
determine the feasibility of the requirements of the proposed AD's and 
disagrees that issuance of the proposed AD's should be delayed. The 
commenter states that it is in the process of prototyping the 
insulation retrofit on several affected airplanes. The commenter 
expects the prototyping to be completed in 6 weeks (the commenter's 
letter was received by the FAA on September 27, 1999). The FAA concurs 
with the commenter that issuance of the final rules should not be 
delayed. As discussed previously, the FAA has participated in the 
prototyping specified by the commenter, and that prototyping effort has 
been completed.

Cost Estimates

    Several commenters state that the FAA ``grossly'' underestimated 
the costs associated with accomplishing the requirements of the 
proposed AD and provided their cost estimates. Two other commenters 
provided cost estimates that were less than those provided in the 
NPRM's.
    The FAA concurs that the cost estimates specified in the NPRM's 
were underestimated. The FAA based its cost estimates on information 
that was available at the time the NPRM's were issued. Since the 
issuance of the NPRM's, the FAA has carefully reviewed the information 
and cost estimates provided by the commenters and the information 
obtained during the prototype exercises. The FAA has learned that most 
Model DC-9-80 and MD-90-30 series airplanes do not have MPET insulation 
blankets installed in the nose section of the airplane. Also, a number 
of airplanes do not have MPET insulation blankets in the fuselage, but 
have MPET insulation blankets only on the air conditioning ducting. The 
airplane manufacturer will be making this information available when 
the service bulletins are revised, as mentioned above. In light of 
these findings, the FAA has revised the cost estimates for the final 
rules, which is summarized below under the heading ``Regulatory 
Evaluation Summary.''
    Several commenters request that the FAA reevaluate the cost 
estimates once the prototype exercises are completed. As discussed 
previously, the FAA has revised the cost estimate of the final rules 
based on the prototype exercises.
    Several commenters state that the FAA should consider costs 
associated with accomplishing the requirements of both proposed AD's 
(i.e., Rules Dockets 99-NM-161-AD and 99-NM-162-AD) , under Title II of 
the Unfunded Mandates Reform Act of 1995.
    The FAA did consider the total costs associated with accomplishing 
the requirements of both NPRM's for all affected airplanes under the 
heading ``Regulatory Evaluation Summary'' in the preamble of the 
NPRM's. A copy of the Preliminary Cost Analysis and Initial Regulatory 
Flexibility Analysis also were included in each docket. These 
documents, along with the final documents, are available for the public 
to review.

Conclusion

    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes previously 
described. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.

Regulatory Evaluation Summary

    To determine the regulatory impact of this AD, the FAA conducted a 
Final Cost Analysis and a Final Regulatory Flexibility Analysis. In 
addition, the FAA assessed the impact of this AD on international trade 
and determined whether it must satisfy the requirements of the Unfunded 
Mandate Reform Act. While a summary of these findings is reported in 
this preamble, a more detailed discussion is included in the Rules 
Docket for this AD.
    Since the publication of the NPRM, the FAA has observed several 
prototype exercises that involved the removal and replacement of MPET 
insulation blankets. Information gained through these exercises has 
contributed to greater understanding by the FAA, operators, and 
manufacturer of the technical details and impacts of the requirements 
of this AD.
    The FAA took account of the results of the prototype exercises, 
comments to the NPRM's, and other additional information, and then 
adjusted its estimates of the costs attributable to this AD. Further, 
recent information indicates that the count of affected airplanes is 
621 Model DC-9-80 series airplanes and 21 Model MD-90-30 series 
airplanes. Specifics of these adjustments are discussed below.
    Several commenters indicate that the FAA underestimated the costs 
of the new insulation material, labor hours necessary for retrofitting, 
and lost passenger revenue from retrofitting downtime. With respect to 
labor and material costs, the FAA contacted the major material 
suppliers (one of which was the airplane manufacturer) and three 
carriers that together operate 75% of the affected fleet. Information 
and estimates from these sources support increases both in the level of 
detail and in the levels of labor and material costs for this adjusted 
estimate. Therefore, the labor cost calculation methods used in this AD 
differ from those used in the NPRM's. The FAA has developed the labor 
estimates for this AD using information supplied by the manufacturer 
and affected operators to arrive at average values specific to the 
requirements of this AD. The FAA considers these values conservative.
    The commenters express disagreement with the asset-based approach 
the FAA used in the Preliminary Cost Analysis to estimate the cost of 
the loss of service of the airplanes during their retrofits. The 
commenters suggest that the estimate be made on the basis of loss of 
per seat revenue. There are two reasons why the FAA uses the asset-
based approach. First, the FAA takes an industry-wide perspective in 
which a passenger who cannot be seated on an airplane that is out of 
service for compliance with this AD can be seated on an airplane that 
is in service. On an industry-wide basis, no revenue will be lost. 
Second, the contribution of a seat's revenue to corporate net income is 
subject to variations in accounting, financial, marketing, and 
operational practice.
    The FAA's asset-based approach centers on the financial ratio, 
overall corporate rate of return, which was reported by the operators 
and published by the Department of Transportation. This ratio is 
applied to the average value of the assets lost to the service of the 
operators and is adjusted for the average period of time for which they 
are lost because of compliance. This approach assumes that operators 
maximize the value of their firms by optimizing the mix and quantity of 
their assets.
    Even though the FAA uses essentially the same ``lost-revenue'' 
method as that in the supplemental NPRM's, the FAA nevertheless did 
increase its estimates of lost revenue by increasing the number of days 
out of service, reducing the operating base year from 365 days to 
approximately 320 days, and raising the rate of return (9% is an 
average of domestic passenger and cargo operators' profit rates as 
estimated by the Department of Transportation's Bureau of 
Transportation Statistics). All of these adjustments raise the value of 
the

[[Page 34335]]

variables applied to the airplane asset values (i.e., $16.2 million per 
DC-9-80/MD-90-30).
    The FAA has identified 621 Model DC-9-80 and 21 MD-90-30 series 
airplanes that will be subject to retrofitting. Four of these airplanes 
have MPET insulation installed throughout. Thirty-five of these 
airplanes have MPET insulation installed only around air conditioning 
ducts. Six hundred and three of these airplanes have MPET installed 
throughout except for the nose. These patterns of installation strongly 
affect the retrofitting costs for each individual airplane. The FAA 
final costs estimate reflects the cost of each airplane when averaged 
for the total DC-9-80/MD-90-30 affected fleet.
    The foregoing results in the following adjustments to the 
calculations presented in the supplemental NPRM.
    For Model DC-9-80 series airplanes, the preliminary estimates for 
labor, material, and lost service per airplane were as follows: labor, 
$335,988; material, $27,021; and lost service, $20,416. The 
corresponding MD-90-30 estimates were as follows: $385,560; $31,008; 
and $37,052.
    The components of this adjusted estimate per airplane, for both 
Model DC-9-80 and MD-9-30 series airplanes, are as follows: combined 
labor and material, $479,921 (averaged as $628,184 for 4 airplanes, 
$73,156 for 35 airplanes, and $502,547 for 603 airplanes, as discussed 
above); and lost service, $65,998. Overall, the adjusted estimates 
compare to the original estimates as follows:

------------------------------------------------------------------------
                 Original                             Adjusted
------------------------------------------------------------------------
625 DC-9-80, each $383,000................  621 MD80s, each $545,919.
22 MD-90-30, each $454,000................  21 MD90s, each $545,919.
------------------------------------------------------------------------

    The adjusted estimate of the total costs of this AD over the five-
year retrofit period for all 644 affected narrow-body airplanes is 
approximately $351.6 million or $288.6 million discounted to present 
value. The total impact for all affected airplanes (i.e., Model DC-9-
80, MD-90-30 , MD-11, and DC-10 series airplanes) is 449.3 million or 
368.4 million discounted to present value over the five year compliance 
time.
    With respect to effects on small entities, the Regulatory 
Flexibility Act (RFA) of 1980 establishes ``as a principle of 
regulatory issuance'' that agencies shall endeavor, consistent with the 
objective of the rule and of applicable statutes, to fit regulatory and 
informational requirements to the sale of the business, organizations, 
and governmental jurisdictions subject to regulation. To achieve that 
principle, the RFA requires agencies to solicit and consider flexible 
regulatory proposals and to explain the rationale for their actions. 
The RFA covers a wide range of small entities, including small 
businesses, not-for-profit organizations, and small governmental 
jurisdictions. Agencies must perform a review to determine whether a 
proposed or final rule will have a significant economic impact on a 
substantial number of small entities. If the determination is that it 
will, the Agency must prepare a regulatory flexibility analysis as 
described in the RFA. However, if an agency determines that a proposed 
or final rule is not expected to have a significant economic impact on 
a substantial number of small entities, section 605(b) of the RFA 
provides that the head of the agency may so certify and a regulatory 
flexibility analysis is not required. The certification must include a 
statement providing the factual basis for this determination, and the 
reasoning should be clear.
    Of the operators affected by this AD, all but three are air 
carriers, none of which is a small business. In two of the remaining 
cases, Model DC-9-80 series airplanes are owned for personal use. One 
Model DC-9-80 series airplane is operated for non-carrier business 
purposes by a large corporation. Although the small business size 
criterion is met in the cases of the two Model DC-9-80 series airplanes 
that are owned for personal use, two such entities do not constitute a 
``substantial number'' within the meaning of the RFA. Thus, pursuant to 
the Regulatory Flexibility Act, 5 U.S. C. 605(b), the FAA certifies 
that this AD will not have a significant economic impact on a 
substantial number of small entities.
    The provisions of this AD will have little or no impact on trade 
for U.S. firms doing business in foreign countries and foreign firms 
doing business in the United States.
    Finally, Title II of the Unfunded Mandates Reform Act of 1995 (the 
Act), enacted as Public Law 104-4 on March 22, 1995, requires each 
Federal agency, to the extent permitted by law, to prepare a written 
assessment of the effects of any Federal mandate in a proposed or final 
agency rule that may result in the expenditure by State, local, and 
tribal governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any one year. 
Section 204(a) of the Act, 2 U.S.C. 1534, requires the Federal agency 
to develop an effective process to permit timely input by elected 
officers (or their designees) of State, local, and tribal governments 
on a proposed ``significant intergovernmental mandate.'' A 
``significant intergovernmental mandate'' under the Act is any 
provision in a Federal agency regulation that would impose an 
enforceable duty upon State, local, and tribal governments, in the 
aggregate, of $100 million (adjusted annually for inflation) in any one 
year. Section 203 of the Act, 2 U.S.C. 1533, provides that before 
establishing any regulatory requirements that might significantly or 
uniquely affect small governments, the agency shall have developed a 
plan that, among other things, provides for notice to potentially 
affected small governments, if any, and for a meaningful and timely 
opportunity to provide input in the development of regulatory 
proposals.
    This AD does not contain any Federal intergovernmental or private 
sector mandate. Therefore, the requirements of Title II of the Unfunded 
Mandates Reform Act of 1995 do not apply.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends part 39 of 
the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

2000-11-01  McDonnell Douglas: Amendment 39-11749. Docket 99-NM-161-
AD.

    Applicability: Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 
(MD-83), DC-9-87 (MD-87) series airplanes; Model MD-90-30 series 
airplanes; and Model MD-88 airplanes; manufacturer's fuselage 
numbers 995 through 2243 inclusive; certificated in any category.

    Note 1: This AD applies to each airplane identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the

[[Page 34336]]

owner/operator must request approval for an alternative method of 
compliance in accordance with paragraph (e) of this AD. The request 
should include an assessment of this AD; and, if the unsafe 
condition has not been eliminated, the request should include 
specific proposed actions to address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To ensure that insulation blankets constructed of metallized 
polyethyleneteraphthalate (MPET) are removed from the fuselage, 
accomplish the following:

Inspection

    (a) Within 5 years after the effective date of this AD, 
determine whether, and at what locations, insulation blankets 
constructed of MPET, are installed. When markings are not visible, 
the determination shall be made by using known MPET material as a 
comparison sample to assist in the identification.

    Note 2: Insulation blankets that are marked with ``DMS 2072, 
Type 2, Class 1, Grade A;'' ``DMS 2072, Type 2, Class 1;'' or ``DMS 
1996, Type 1;'' are constructed of MPET.

Corrective Actions

    (b) For insulation blankets that are determined not to be 
constructed of MPET, no further action is required by this AD.
    (c) For insulation blankets that are determined to be 
constructed of MPET, within 5 years after the effective date of this 
AD, replace the MPET insulation blankets with new insulation 
blankets that have been approved by the Manager, Los Angeles 
Aircraft Certification Office (ACO), FAA, Transport Airplane 
Directorate. The blankets shall be replaced in accordance with the 
Accomplishment Instructions of McDonnell Douglas Service Bulletin 
MD-90-25-015, Revision 01, dated November 5, 1997 (for Model MD-90-
30 series airplanes); or McDonnell Douglas Service Bulletin MD80-25-
355, Revision 01, dated November 5, 1997 (for Model DC-9-80 series 
airplanes and Model MD-88 airplanes); as applicable. The replacement 
insulation blankets must be constructed of materials tested in 
accordance with Appendix 1 of this AD, or in accordance with a 
method approved by the Manager, Los Angeles ACO.

    Note 3: Although this paragraph allows up to 5 years for the 
required replacement, the FAA anticipates that operators will comply 
at the earliest practicable maintenance opportunity.


    Note 4: Only one of the two metallized Tedlar<SUP>TM</SUP> 
covers specified in the service bulletins has been shown to have 
successfully passed the testing of the American Society for Testing 
and Materials (ASTM) flammability standard and is considered 
acceptable for compliance with the requirements of paragraph (c) of 
this AD.

Spares

    (d) As of the effective date of this AD, no person shall install 
an MPET insulation blanket on any airplane.

Alternative Methods of Compliance

    (e) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Los Angeles ACO. Operators shall 
submit their requests through an appropriate FAA PMI, who may add 
comments and then send it to the Manager, Los Angeles ACO.

    Note 5: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Los Angeles ACO.

Special Flight Permits

    (f) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.

Incorporation by Reference

    (g) The blankets shall be replaced in accordance with the 
Accomplishment Instructions of McDonnell Douglas Service Bulletin 
MD-90-25-015, Revision 01, dated November 5, 1997; or McDonnell 
Douglas Service Bulletin MD80-25-355, Revision 01, dated November 5, 
1997; as applicable. This incorporation by reference was approved by 
the Director of the Federal Register in accordance with 5 U.S.C. 
552(a) and 1 CFR part 51. Copies may be obtained from Boeing 
Commercial Aircraft Group, Long Beach Division, 3855 Lakewood 
Boulevard, Long Beach, California 90846, Attention: Technical 
Publications Business Administration, Dept. C1-L51 (2-60). Copies 
may be inspected at the FAA, Transport Airplane Directorate, 1601 
Lind Avenue, SW., Renton, Washington; or at the FAA, Transport 
Airplane Directorate, Los Angeles Aircraft Certification Office, 
3960 Paramount Boulevard, Lakewood, California; or at the Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (h) This amendment becomes effective on June 30, 2000.

Appendix 1.--Test for Materials Replacing Metallized PET Thermal 
Acoustical Insulation, Film February 16, 2000

    This test method is used to evaluate the flammability and flame 
propagation characteristics of thermal/acoustic insulation when 
exposed to both a radiant heat source and a flame.
    (a) Definitions.
    (1) Thermal/Acoustic Insulation. Thermal/acoustic insulation is 
defined as a material or system of materials used to provide thermal 
and/or acoustic protection. Examples include a film-covering 
material encapsulating a core material such as fiberglass or other 
batting material and foams.
    (2) Radiant Heat Source. The radiant heat source is an air/gas 
fueled radiant heat energy panel.
    (b) Test Apparatus (as schematically shown in figure 1).
    (1) Radiant Panel Test Chamber. Tests will be conducted in the 
radiant panel test chamber as used in ASTM--Designation: E 648. It 
is suggested that the test chamber be located under an exhaust hood 
to facilitate clearing the chamber of smoke after each test. The 
radiant panel test chamber shall consist of an enclosure 55 inches 
(1400 mm) long by 19\1/2\ inches (500 mm) deep by 28 inches (710 mm) 
above the test specimen. The sides, ends, and top shall be insulated 
with a fibrous ceramic insulation such as Kaowool<SUP>TM</SUP> 
board. One side shall be provided with an approximately 48 by 6 inch 
(1219 by 152mm) draft tight, high temperature, heat resistant glass 
observation window, to facilitate viewing the sample during testing. 
On the same side and below the window is a door which, when open, 
allows the specimen platform to be moved out for mounting or removal 
of test specimens. The bottom of the test chamber shall consist of a 
sliding steel platform, which has provisions for securing the test 
specimen holder in a fixed and level position. The top of the 
chamber shall have an exhaust stack with interior dimensions of 4 
inches (102mm) wide by 15 inches (380 mm) deep by 12.5 inches 
(318mm) high at the opposite end of the chamber from the radiant 
energy source.
    (2) Radiant Heat Source. The radiant heat energy source will be 
a panel of porous refractory material mounted in a cast iron frame, 
with a radiation surface of 12 by 18 inches (305 by 457mm). It shall 
be capable of operating at temperatures up to 1500 deg.F (816 deg.C 
(Figure 1).

[[Page 34337]]

[GRAPHIC] [TIFF OMITTED] TR26MY00.023

    (i) Radiant Panel Fuel System. The radiant panel fuel will be 
propane (liquid petroleum gas--2.1 UN 1075). The panel fuel system 
shall consist of a venturi-type aspirator for mixing gas and air at 
approximately atmospheric pressure. Suitable instrumentation will be 
necessary for monitoring and controlling the flow of fuel and air to 
the panel. Instrumentation will include an air flow gauge, an air 
flow regulator, a gas pressure gauge, and a rotameter for measuring 
gas flow.
    (ii) Radiant Panel Placement. The panel will be mounted in the 
chamber at 30 degrees to the horizontal specimen plane.
    (3) Specimen Holding System.
    (i) The sliding platform serves as the housing for test specimen 
placement. A \1/4\ inch (6.35mm) sheet of Duraroc<greek-k>a, or 
other non-combustible base, measuring 43\1/4\ inches by 12\1/2\ 
inches (1098 by 317.5mm) will be placed in the open bottom (base) of 
the sliding platform. It is necessary to cut the non-combustible 
base into two pieces for placement in the bottom of the platform, 
since it will be supported by a \3/4\-inch (19.1mm) lip that extends 
around the bottom of the platform base. It is suggested that the 
shortest piece be placed at the end furthest from the radiant panel 
(figure 2). A \1/2\ inch (13mm) piece of 
Kaowoo<greek-l><SUP>TM</SUP> board or other high temperature 
material measuring 41\1/2\ by 8\1/4\ inches (1054 by 210mm) will be 
attached to the back side of the platform. This board will serve as 
a heat retainer and will protect the test specimen from excessive 
preheating. The height of this board must not be too high such that 
it will impede the sliding platform movement (in and out) of the 
test chamber.

[[Page 34338]]

[GRAPHIC] [TIFF OMITTED] TR26MY00.024

    (ii) The test specimen will be placed horizontally on the non-
combustible base. A stainless steel retaining frame (AISI Type 300 
UNA-NO8330), or equivalent, having a thickness of 0.078 inches 
(1.98mm) and overall dimensions of 44\3/4\ by 12\3/4\ inches (1137 
by 320mm) with a specimen opening of 40 by 7\7/8\ (1016 by 140mm) 
will be placed on top of the test specimen. The retaining frame will 
have two \1/2\inch (12.7mm) holes drilled at each end for 
positioning the frame to the two stud bolts at each end of the 
sliding platform (figure 3).
[GRAPHIC] [TIFF OMITTED] TR26MY00.025

    (iii) A securing frame (acting as a clamping mechanism) 
constructed of mild steel will be placed over the test specimen. The 
securing frame overall dimensions are 42\1/2\ by 10\1/2\ inches 
(1080 by 267mm) with a specimen opening of 39\1/2\ by 7\1/2\ inches 
(1003 by 190mm). Hence, the exposed area of test specimen exposed to 
the radiant panel is 39\1/4\ by 7\1/4\ inches (996 by 184mm). See 
figure 4. It is not necessary to physically fasten the securing 
frame over the test specimen due to the weight of the frame itself.
    (4) Pilot Burner. The pilot burner used to ignite the specimen 
is a commercial propane venturi torch with an axially symmetric 
burner tip having a propane supply tube with an orifice diameter of 
0.003 inches (0.076mm). The propane flow is adjusted to produce a 
pencil flame blue inner cone length of \1/2\ inch (13mm). There will 
be a means provided to move the burner out of the ignition position 
so that the flame is horizontal and at least 2 inches (50mm) above 
the specimen plane.
    (5) Thermocouples. Three 24 American Wire Gauge (AWG) Type K 
(Chromel-Alumel) thermocouples will be installed in the test chamber 
for temperature monitoring. All three are inserted into the chamber 
through three small holes drilled through the top of the chamber. 
One thermocouple is placed 2 inches (51mm) from the end of the 
radiant panel and approximately 16 inches (406mm) above the test 
specimen. The second thermocouple is placed 5 inches (127mm) from 
the first thermocouple and approximately 16 inches (406mm) from the 
sample. The third thermocouple is located in the chimney 
approximately 38 inches (965mm) above the specimen.
    (6) Calorimeter. The calorimeter will be a one inch cylindrical 
water-cooled, total heat flux density, foil type Gardon Gage that 
has

[[Page 34339]]

a range of 0 to 5 BTU/ft\2\-second (0 to 5.6 Watts/cm\2\).
    (7) Calorimeter Calibration Specification and Procedure.
    (i) Calorimeter Specification.
    (A) Foil diameter will be 0.25<plus-minus>0.005 inches 
(6.35<plus-minus>0.13mm).
    (B) Foil thickness will be 0.0005<plus-minus>0.0001 inches 
(0.013<plus-minus>0.0025mm).
    (C) Foil material will be thermocouple grade Constantan.
    (D) Temperature measurement will be a Copper Constantan 
thermocouple.
    (E) The copper center wire diameter will be 0.0005 inches 
(0.013mm).
    (F) The entire face of the calorimeter will be lightly coated 
with ``Black Velvet'' paint having an emissivity of 96 or greater.
    (ii) Calorimeter Calibration.
    (A) The calibration method will be by comparison to a like 
standardized transducer.
    (B) The standardized transducer will meet the specification 
given in paragraph (6).
    (C) It will be calibrated against a primary standard by the 
National Institute of Standards and Technology (NIST).
    (D) The method of transfer will be a heated graphite plate.
    (E) The graphite plate will be electrically heated, have a clear 
surface area on each side of the plate of at least 2 by 2 inches (51 
by 51mm), and be \1/8\ inch <plus-minus>\1/16\ inch thick (3.2 
<plus-minus>1.6mm).
    (F) The 2 transducers will be centered on opposite sides of the 
plates at equal distances from the plate.
    (G) The distance of the calorimeter to the plate will be no less 
than 0.0625 inches (1.6mm), nor greater than 0.375 inches (9.5mm).
    (H) The range used in calibration will be at least 0-3.5 BTUs/
ft\2\ second (0-3.9 Watts/cm\2\) and no greater than 0-5.6 BTUs/
ft\2\ second (0-5 Watts/cm\2\).
    (I) The recording device used must record the 2 transducers 
simultaneously or at least within \1/10\ second of each other.
    (8) Calorimeter Fixture. With the sliding platform pulled out of 
the chamber, install a 2-rail fixture that has a travel range of 
40\1/4\ inches (1022mm) over the sliding platform. The dimension 
between the 2 rails is 2\11/16\ inches (68mm). The rail fixture is 
screwed into the sliding panel, such that it is always directly 
under the geometric center of the radiant panel (figure 4). Push the 
platform into the chamber and insert the calorimeter. The 
calorimeter, which is mounted in an insulated housing, fits in the 
rail opening but has enough clearance such that it may be moved 
along the rail for heat flux readings. The top surface of the 
calorimeter must be level with the rails.
[GRAPHIC] [TIFF OMITTED] TR26MY00.026

    (9) Instrumentation. A calibrated recording device with an 
appropriate range or a computerized data acquisition system will be 
provided to measure and record the outputs of the calorimeter and 
the thermocouples. The data acquisition system must be capable of 
recording the calorimeter output every second.
    (10) Timing Device. A stopwatch or other device, accurate to 
<plus-minus>1second/hour, will be provided to measure the time of 
application of the pilot burner flame.
    (c) Test Specimens.
    (1) Specimen Preparation. A minimum of three test specimens will 
be prepared and tested.
    (2) Construction. Cut a piece of core material such as foam or 
fiberglass. If fiberglass is used, cut the material 43\1/2\ 
(<plus-minus>\1/4\) inches long (1093mm) (<plus-minus>6.3mm) by 
12\1/2\ inches (305.1mm) wide. If using foam, cut the material 41\1/
4\ inches (1039mm) by 11 inches wide (279mm) by 1\1/2\ inches 
(381mm) high. Cut a piece of film cover material (if used) large 
enough to cover the core material. It is permissible to staple the 
film cover at the ends, as they are not exposed to the radiant heat 
source. A piece or pieces of an inorganic/inert material such as 
Kaowoo<greek-l><SUP>TM</SUP> or Marinit<greek-e> <SUP>TM</SUP> board 
may be placed in the bottom of the sliding platform holder if the 
sample is not thick enough to be level with the top of the sliding 
platform. The specimen thickness must be of the same thickness as 
installed in the airplane.
    (d) Specimen Conditioning. The specimens will be conditioned at 
70 <plus-minus>5 deg.F (21 <plus-minus>2 deg.C) and 
55%<plus-minus>10% relative humidity for a minimum of 24 hours prior 
to testing.
    (e) Calibration.
    (1) With the sliding platform out of the chamber, install the 
rail fixture. Push the platform back into the chamber, install the 
calorimeter (in its housing), and move the calorimeter to the 
``zero'' position (figure 5). Close the bottom door located below 
the sliding platform. The centerline of the calorimeter is 1\7/8\ 
inches (46mm) from the end of the sliding platform. This will be the 
``zero'' position. The distance from the center of the calorimeter 
to the radiant panel surface at this point is 7.5 inches 
<plus-minus>\1/8\ (191 mm <plus-minus>3).
    (i) Prior to igniting the radiant panel, ensure that the 
calorimeter face is clean and that there is water running through 
the calorimeter.
    (2) Ignite the panel. Adjust the fuel/air mixture to achieve 1.5 
BTUs/ft\2\-second <plus-minus>0.025 BTUs/ft\2\-second (1.9 Watts/
cm\2\<plus-minus>0.025 Watts/cm\2\) at the ``zero'' position. Allow 
the unit to reach steady state (this may take up to 1 hour). The 
pilot burner is off during this time. The temperature as measured by 
the thermocouple closest to the panel (forward) is approximately 
1100 deg.F (600 deg.C). The temperatures recorded by thermocouples 2 
and 3 ( thermocouple 3 located in chimney) are approximately 
430 deg.F (230 deg.C) and 300 deg.F (135 deg.C), respectively.

[[Page 34340]]

[GRAPHIC] [TIFF OMITTED] TR26MY00.027

    (3) After steady-state conditions have been reached, move the 
calorimeter 2 inches (51mm) from the ``zero'' position and record 
the heat flux. Allow a minimum of 30 seconds at each position for 
the calorimeter to stablize. Record at least 10 positions. (Figure 6 
depicts a calibration profile.)
[GRAPHIC] [TIFF OMITTED] TR26MY00.028

    (4) It is not necessary to run a full heat flux calibration 
(minimum of 10 positions) each time the chamber is powered on. It is 
required that a heat flux measurement be taken at the ``zero'' 
position at the start of the test period (e.g., each morning) to 
ensure that the 1.5 BTU/ft\2\-second (1.9 Watts/cm\2\) requirement 
be met. A full calibration should be run periodically.
    (5) Open the bottom door, pull out the sliding platform, and 
remove the calorimeter and rail fixture.
    (f) Test Procedure.
    (1) Ignite the pilot burner. Ensure that it is at least 2 inches 
(51mm) above the top of the platform. The burner must not contact 
the specimen until the test begins.
    (2) Place the test specimen in the sliding platform holder. 
Ensure that the test sample surface is level with the top of the 
platform. At ``zero'' point, the specimen surface is 7\1/2\ inches 
<plus-minus>1/8 (191mm <plus-minus>3) below the radiant panel.
    (3) With film/fiberglass assemblies, it may be necessary to 
puncture small holes in the film cover to purge any air inside. This 
allows the operator to maintain the proper test specimen position 
(level with the top of the platform). The holes should be made in 
the sides and/or the corners of the test specimen using a needle-
like tool.
    (4) Place the retaining frame and the securing frame over the 
test specimen.
    (5) A small mark should be placed on the ``zero'' point.
    (6) Immediately push the sliding platform into the chamber and 
close the bottom door.
    (7) Bring the pilot burner flame into contact with the center of 
the specimen such that the center line of the flame impinges on the 
``zero'' point and simultaneously start the timer. The burner flame 
impinges the sample at an angle of approximately 20 degrees with the 
horizontal (front of the sliding platform).
    (8) Leave the burner in position for 15 seconds and then remove 
to a position at least 2 inches (51mm) above the specimen.
    (g) Report.
    (1) Identify and describe the specimen being tested.
    (2) Report any shrinkage or melting of the test specimen.
    (3) Report the Burn length
    (4) Report Extinguishing Time
    (h) Requirements.
    (1) During burner application, no flaming is allowed to 
propagate more than 2 inches (50.8mm) along the sample (to the left 
in figure 1) of the centerline of the flame.
    (2) There shall be no flaming of the test sample after pilot 
burner removal.


[[Page 34341]]


    Issued in Renton, Washington, on May 19, 2000.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.

[FR Doc. 00-13149 Filed 5-25-00; 8:45 am]
BILLING CODE 4910-13-P