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

[Federal Register Volume 65, Number 251 (Friday, December 29, 2000)]
[Rules and Regulations]
[Pages 82898-82901]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-33018]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-226-AD; Amendment 39-12055; AD 2000-26-05]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 737, 747, 757, and 767 
Series 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 Boeing Model 737, 747, 757, and 767 series 
airplanes, that requires 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: Effective February 2, 2001.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of February 2, 2001.

ADDRESSES: The service information referenced in this AD may be 
obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, 
Washington 98124-2207. 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 Office of 
the Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.

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: 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 Boeing Model 737, 747, 
757, and 767 series airplanes was published in the Federal Register on 
August 10, 2000 (65 FR 48947). That action proposed to require rework 
of certain duct assemblies of the environmental control system (ECS) or 
replacement of the duct assemblies with new or reworked duct 
assemblies.

Comments Received

    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Support for the Proposal

    Two commenters support the proposed rule.

Requests to Revise Compliance Time

    Several commenters request an extension of the proposed compliance 
time. Generally, the commenters claim that the proposed five-year 
compliance time will result in a need to accomplish the proposed 
requirements on some airplanes before the next scheduled heavy 
maintenance visit, which would cause significant airplane down time, 
and would impose a substantial cost penalty. Individual comments are 
presented below.
    One of the commenters suggests that an extension of the compliance 
time to six years for all aircraft types would not compromise safety 
any further. Another commenter requests that the compliance time be 
stated as follows: ``* * * within five years after the effective date 
of the AD, or at the next scheduled heavy maintenance visit, whichever 
occurs later, not to exceed eight years after the effective date.'' 
This commenter performs segmented ``C'' checks approximately every two 
years, and it takes four such checks to reach all areas of the 
airplane. Therefore, under that commenter's maintenance program, access 
to the specific areas affected may not occur for eight years.
    The Air Transport Association (ATA) of America, on behalf of its 
members, states that the compliance time should be stated as follows: 
``* * * within five years after the effective date of this AD, or at 
the next scheduled heavy maintenance visit, whichever occurs later, not 
to exceed six years after the effective date.'' The ATA contends that 
this compliance time ``would preclude the press associated with 
significant, unscheduled maintenance visits''; in practical terms, this 
would affect the installation time of less than 20 percent of the 
applicable airplanes. The ATA believes that its suggested compliance 
time would achieve a level of safety equivalent to that intended by the 
proposed AD.
    Another commenter states that it participated in a Boeing-hosted 
meeting on the subject ECS ducting flammability concerns and asked 
Boeing to recommend to the FAA that the actions be required during a 
heavy maintenance visit. The commenter notes that Boeing did indeed 
make this recommendation to the FAA in the referenced FAA-approved 
service bulletins. The commenter says that six years would facilitate 
making use of the first heavy maintenance visit under current 
maintenance programs. The commenter adds that compliance periods that 
intend to make use of scheduled down time per an approved maintenance 
program should reflect an interval taking into account such approved 
maintenance programs.
    Another commenter states that a moderate escalation of the 
compliance time to 6 years would avoid burdening the operators with 
excessive costs, and would allow accomplishment of the modification at 
a heavy maintenance visit. Retaining the proposed 5-year compliance 
time for Model 757 series

[[Page 82899]]

airplanes would require that approximately 17 percent of the fleet (15 
airplanes) undergo the modifications at a light or special maintenance 
visit, which would impose an undue financial burden on some operators.
    The commenter adds that a comparison between the compliance time 
specified in this proposed rule to that given in two previously issued 
AD's that address similar unsafe conditions cannot be used as a basis 
for the choice of a compliance time for this proposed rule. [The AD's 
referenced by the commenter are AD 2000-11-01, amendment 39-11749 (65 
FR 34322, May 26, 2000), and AD 2000-11-02, amendment 39-11750 (65 FR 
34341, May 26, 2000). Those AD's require replacement of metallized 
Mylar insulation blankets with new blankets made of more flame-
resistant material on certain McDonnell Douglas airplanes.] Based on 
information about various heavy maintenance intervals provided by the 
commenter, the operators of airplanes affected by AD 2000-11-01 and AD 
2000-11-02 would not be subjected to excessive modification costs since 
all of the affected airplanes could be modified during a heavy 
maintenance visit within the 5-year compliance time specified in those 
two AD's.
    The FAA concurs that the compliance time can be extended somewhat. 
The FAA has closely reviewed the rationale presented by the commenters. 
In addition, the FAA has examined related comments to AD 2000-11-01 and 
AD 2000-11-02. In those AD's, the compliance time was extended from 
four to five years in the final rules.
    The FAA acknowledges that a compliance time of six years will more 
closely align with heavy maintenance visits. Paragraph (a) of the final 
rule has been revised accordingly. For any operator that performs 
segmented ``C'' checks every two years, the revised compliance time 
should allow enough time to schedule the ducting rework or replacement 
during one of the next three such checks. The extension of the 
compliance time also will minimize the amount of unscheduled work and 
associated down time. The FAA considers that this extension of the 
compliance time will not adversely affect safety.

Request for Sampling Program

    One commenter requests that a sampling program be incorporated for 
all fleet types affected to determine if BAC 5010, Type 97 adhesive was 
used on specific airplanes and to establish the requirements for 
replacing the ECS ducts. The commenter states that neither Boeing nor 
the FAA has provided concrete evidence that BAC 5010, Type 97 adhesive 
was used in the assembly of all the ECS ducts. The commenter adds that 
the applicable service bulletins and proposed rule are based purely on 
conjecture. The commenter suggests that negative findings in such a 
sampling program would offer terminating action for the proposed rule.
    The FAA does not concur. The FAA finds that there is a significant 
amount of evidence pointing to widespread use of unsafe adhesives (that 
is, material and adhesive combinations that are easily ignited and 
consequently able to propagate a small fire) on Model 737, 747, 757, 
and 767 series airplanes. Determining which ECS ducts are affected has 
already been accomplished to a great extent through the efforts of 
Boeing. The scope of the parts and airplanes affected by the final rule 
has been significantly reduced through Boeing's efforts in surveying 
its duct suppliers. Only airplanes having parts that were made by 
suppliers that used unsafe adhesives in their manufacturing processes 
have been included in the applicability of this final rule. Although it 
is possible that some parts may have been manufactured using compliant 
adhesives, the FAA expects that almost all were manufactured using the 
BAC 5010, Type 97 adhesive because it is much easier to apply than 
other types of adhesives. Therefore, the FAA has determined that an 
option for a sampling program would not provide sufficient value and 
has not included such an option in this final rule.
    However, an operator may request approval of an alternative method 
of compliance in accordance with the provisions of paragraph (b) of 
this final rule, provided that evidence is submitted to show that no 
unsafe adhesive was used in the construction of the ECS ducting on the 
airplanes in its fleet.

Request for Clarification of Discussion Section

    One commenter requests that certain portions of the Discussion 
section of the proposed rule be rewritten. The commenter specifically 
asks that this section include the FAA's actual safety concerns, which 
are that the material is too easy to ignite and is not self-
extinguishing. The commenter also asks that the section include a 
statement indicating that a small electrical arc would be sufficient to 
ignite the fiberglass insulation material, if this is indeed the case.
    Although the Discussion section of the proposed rule is not 
restated in the final rule, the FAA acknowledges that the commenter's 
statements are correct. The purpose for issuing this AD is to prevent 
ignition of insulation material by a small arc, which would then not 
self-extinguish, but would instead propagate a fire.

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.

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 will be affected by this AD. The following table shows the 
estimated cost impact of the required 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 AD is $2,552,996.

                                                   Cost Impact
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                                       U.S.-
              Model                 Registered    Estimated work     Estimated       Estimated       Estimated
                                     airplanes         hours        labor cost      parts cost      fleet cost
----------------------------------------------------------------------------------------------------------------
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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[[Page 82900]]

    The cost impact figures discussed above are based on assumptions 
that no operator has yet accomplished any of the requirements of this 
AD action, and that no operator would accomplish those actions in the 
future if this 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 are required by this 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 adopted herein will 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 final rule does not have federalism 
implications under Executive Order 13132.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

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:

2000-26-05  Boeing: Amendment 39-12055. 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 sries airplanes, 
certificated in any category, having the line numbers listed in the 
following table:

                                                  Applicability
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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,  N/A
                                        2733, 2734, 2736 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,...  522, 525, 718, 758 770
----------------------------------------------------------------------------------------------------------------


    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 6 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 
Secs. 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

    (d) The actions shall be done in accordance with Boeing Alert 
Service Bulletin 737-21A1129, including Appendices A and B; dated 
June 29, 2000; Boeing Alert Service Bulletin 747-21A2416, including 
Appendices A and B; dated June 29, 2000; Boeing Alert Service 
Bulletin 757-21A0084, including Appendices A and B; dated June 29, 
2000; Boeing Alert Service Bulletin 757-21A0085, including 
Appendices A and B; dated June 29, 2000; or Boeing Alert Service 
Bulletin 767-21A0158; including Appendices A and B; dated June 29, 
2000. 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 Airplane 
Group,

[[Page 82901]]

P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be 
inspected at the FAA, Transport Airplane Directorate, 1601 Lind 
Avenue, SW., Renton, Washington; or at the Office of the Federal 
Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Effective Date

    (e) This amendment becomes effective on February 2, 2001.

    Issued in Renton, Washington, on December 20, 2000.
John J. Hickey,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-33018 Filed 12-28-00; 8:45 am]
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