[Federal Register Volume 65, Number 155 (Thursday, August 10, 2000)]
[Proposed Rules]
[Pages 48947-48950]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-20244]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-226-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737, 747, 757, and 767 
Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Boeing Model 737, 747, 
757, and 767 series airplanes. This proposal would require rework of 
certain duct assemblies of the environmental control system (ECS) or 
replacement of the duct assemblies with new or reworked duct 
assemblies. This action is necessary to prevent potential ignition of 
fiberglass insulation material installed on the outside of the ECS 
ducts, which could propagate a small fire and lead to a larger fire. 
This action is intended to address the identified unsafe condition.

DATES: Comments must be received by September 25, 2000.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Transport Airplane Directorate, ANM-114, 
Attention: Rules Docket No. 2000-NM-226-AD, 1601 Lind Avenue, SW., 
Renton, Washington 98055-4056. Comments may be inspected at this 
location between 9:00 a.m. and 3:00 p.m., Monday through Friday, except 
Federal holidays. Comments may be submitted via fax to (425) 227-1232. 
Comments may also be sent via the Internet using the following address: 
[email protected]. Comments sent via fax or the Internet must 
contain ``Docket No. 2000-NM-226-AD'' in the subject line and need not 
be submitted in triplicate. Comments sent via the Internet as attached 
electronic files must be formatted in Microsoft Word 97 for Windows or 
ASCII text.
    The service information referenced in the proposed rule may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. This information may be examined at the FAA, 
Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, 
Washington.

FOR FURTHER INFORMATION CONTACT: James Cashdollar, Aerospace Engineer, 
Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 
1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (425) 
227-2785; fax (425) 227-1181.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications shall identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Submit comments using the following format:
     Organize comments issue-by-issue. For example, discuss a 
request to change the compliance time and a request to change the 
service bulletin reference as two separate issues.
     For each issue, state what specific change to the proposed 
AD is being requested.
     Include justification (e.g., reasons or data) for each 
request.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NM-226-AD.''

[[Page 48948]]

The postcard will be date stamped and returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Transport Airplane Directorate, ANM-114, Attention: Rules 
Docket No. 2000-NM-226-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received reports that fiberglass insulation material 
installed on the outside of the ducts of the environmental control 
system (ECS) on certain Boeing Model 737, 747, 757, and 767 series 
airplanes does not meet fire safety requirements. During fire testing, 
samples of fiberglass insulation from the ECS ducts, with BMS8-142 
vapor barrier bonded to the outer surface of the insulation with 
BAC5010 Type 97 adhesive, burned at a rate faster than allowed by 
section 25.853 (``Fire Protection: Compartment Interiors'') of the 
Federal Aviation Regulations (14 CFR 25.853). This condition, if not 
corrected, could result in potential ignition of the fiberglass 
insulation installed on the ECS ducts, which could propagate a small 
fire and lead to a larger fire.

Other Relevant Rulemaking

    On May 19, 2000, the FAA issued AD 2000-11-01, amendment 39-11749 
(65 FR 34322, May 26, 2000), which is applicable to certain McDonnell 
Douglas Model DC-9-80 and MD-90-30 series airplanes and Model MD-88 
airplanes; and AD 2000-11-02, amendment 39-11750 (65 FR 34341, May 26, 
2000), which is applicable to certain McDonnell Douglas Model DC-10-
10F, DC-10-15, DC-10-30, DC-10-30F, DC-10-40, MD-11, and MD-11F series 
airplanes. These AD's require determination of whether, and at what 
locations, insulation blankets made of metallized 
polyethyleneteraphthalate (MPET) are installed, and replacement of any 
MPET insulation blankets with new blankets made of metallized Tedlar or 
equivalent blanket material. Those AD's were prompted by reports of 
fires (in flight and on the ground) on certain airplanes equipped with 
MPET insulation blankets. Such insulation blankets could propagate a 
small fire that is the result of an otherwise harmless electrical arc, 
and could result in a much larger fire.
    The unsafe condition addressed by those AD's is similar to that 
addressed in this proposed AD. The fiberglass insulation with BMS8-142 
vapor barrier bonded to the outer surface with BAC5010 Type 97 
adhesive, which is the subject of this AD, can be ignited by a small 
ignition source and propagate a fire in a manner similar to the MPET 
insulation blankets. AD 2000-11-01 and AD 2000-11-02 require 
replacement of MPET insulation blankets with new blankets; this 
proposed AD would require rework of the ECS duct assemblies or 
replacement of the duct assemblies with new or reworked duct 
assemblies. The FAA finds that rework of the duct assemblies will 
ensure an acceptable level of safety for the affected airplanes 
addressed in this proposed AD.
    A similar unsafe condition exists in drip shields on certain Boeing 
Model 747, 757, 767, and 777 series airplanes. Some drip shields are 
assembled with the moisture barrier cover bonded to the insulation and 
multiple insulation layers bonded together using a non-flame-resistant 
adhesive. Such assembly of the drip shield reduces the fire resistance 
of the moisture barrier cover and insulation. As a result, the drip 
shield assemblies do not meet the requirements of section 25.853 
(``Fire Protection: Compartment Interiors'') of the Federal Aviation 
Regulations (14 CFR 25.853). This condition, if not corrected, could 
result in potential ignition of the moisture barrier cover of the drip 
shield, which could propagate a small fire that results from an 
otherwise harmless electrical arc, leading to a larger fire. A separate 
rulemaking action [notice of proposed rulemaking, Rules Docket No. 
2000-NM-217-AD] is being issued to address that unsafe condition on 
affected airplanes.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Alert Service Bulletins 
737-21A1129, 747-21A2416, 757-21A0084, 757-21A0085, and 767-21A0158; 
all including Appendices A and B; all dated June 29, 2000. Those 
service bulletins describe procedures for rework of certain ECS duct 
assemblies or replacement of the duct assemblies with new or reworked 
duct assemblies. The rework involves replacement of existing fiberglass 
insulation with new insulation. Accomplishment of the actions specified 
in the service bulletins is intended to adequately address the 
identified unsafe condition.

Explanation of Requirements of Proposed Rule

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require accomplishment of the actions specified in 
the applicable service bulletin described previously, except as 
discussed below.

Differences Between Proposed Rule and Service Bulletins

    Operators should note that the service bulletins specify that the 
rework or replacement of the ECS ducts is to be accomplished at the 
next heavy maintenance check. The FAA finds that such a compliance time 
will not ensure that the rework or replacement is accomplished in a 
timely manner. In developing an appropriate compliance time for this 
AD, the FAA considered not only the manufacturer's recommendation, but 
the degree of urgency associated with addressing the subject unsafe 
condition, as well as the compliance time for the actions required by 
the previously described AD 2000-11-01 and AD 2000-11-02. AD 2000-11-01 
and AD 2000-11-02 require replacement of MPET insulation blankets on 
affected airplanes within five years after June 30, 2000 (the effective 
date of those AD's). In light of all of these factors, and especially 
the similarity of the unsafe condition addressed in this proposed AD to 
that addressed in the AD's described previously, the FAA finds a 
compliance time of five years after the effective date of this AD for 
initiating the proposed actions to be warranted, in that it represents 
an appropriate interval of time allowable for affected airplanes to 
continue to operate without compromising safety.

Cost Impact

    There are approximately 1,162 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 403 airplanes of U.S. 
registry would be affected by this proposed AD. The following table 
shows the estimated cost impact of the proposed actions for airplanes 
affected by this AD. The average labor rate is $60 per work hour. The 
estimated total cost for all airplanes affected by this proposed AD is 
$2,552,996.

[[Page 48949]]



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                                                    U.S.-
                     Model                        registered   Work hours   Labor cost   Parts cost   Fleet cost
                                                  airplanes   (estimated)  (estimated)  (estimated)  (estimated)
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737............................................          113           32       $1,920         $732     $299,676
747............................................           23          336       20,160        2,800      528,080
757............................................          199           47        2,820          360      632,820
767............................................           68          238       14,280        1,785    1,092,420
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    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the proposed requirements 
of this AD action, and that no operator would accomplish those actions 
in the future if this proposed AD were not adopted. The cost impact 
figures discussed in AD rulemaking actions represent only the time 
necessary to perform the specific actions actually required by the AD. 
These figures typically do not include incidental costs, such as the 
time required to gain access and close up, planning time, or time 
necessitated by other administrative actions.
    The manufacturer has advised the FAA that warranty remedies may be 
available for parts and labor costs associated with accomplishing the 
actions that would be required by this proposed AD. Therefore, the 
future economic cost impact of this rule on U.S. operators may be less 
than the cost impact figures indicated above.

Regulatory Impact

    The regulations proposed herein would not have a substantial direct 
effect on the States, on the relationship between the national 
Government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, it 
is determined that this proposal would not have federalism implications 
under Executive Order 13132.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
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:

Boeing: Docket 2000-NM-226-AD.

    Applicability: Model 737-300, 737-400, 737-500, 747, 757-200, 
757-300, 767-200, 767-300, and 767-300F series airplanes having the 
line numbers listed below; certificated in any category.

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               Model                           Affected line numbers (L/N)                    Except L/N
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737-300, -400, -500................  2591, 2601, 2720, 2723, 2730, 2733, 2734, 2736   N/A
                                      through 2850 inclusive, 2852 through 3126
                                      inclusive.
747................................  1011 through 1233 inclusive....................  1012, 1174, 1216.
757-200, -300......................  580 through 895 inclusive......................  581, 583 through 586
                                                                                       inclusive, 589, 595, 609,
                                                                                       613, 615, 622, 624, 626,
                                                                                       669, 674.
767-200, -300, -300F...............  521 through 767 inclusive, 770.................  522, 525, 718, 758.
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    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 owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (b) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by 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 prevent potential ignition of fiberglass insulation in the 
environmental control system (ECS) ducts, which could propagate a 
small fire and lead to a larger fire, accomplish the following:

Rework or Replacement

    (a) Within 5 years after the effective date of this AD, rework 
ECS duct assemblies or replace existing duct assemblies with new or 
reworked duct assemblies, in accordance with Boeing Alert Service 
Bulletins 737-21A1129, 747-21A2416, 757-21A0084, 757-21A0085, or 
767-21A0158; all including Appendices A and B; all dated June 29, 
2000; as applicable.

Alternative Methods of Compliance

    (b) 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, Seattle Aircraft Certification 
Office (ACO), FAA. Operators shall submit their requests through an 
appropriate FAA Principal Maintenance Inspector, who may add 
comments and then send it to the Manager, Seattle ACO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Seattle ACO.

Special Flight Permits

    (c) 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.


[[Page 48950]]


    Issued in Renton, Washington, on August 4, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-20244 Filed 8-9-00; 8:45 am]
BILLING CODE 4910-13-P