[Federal Register Volume 65, Number 155 (Thursday, August 10, 2000)]
[Proposed Rules]
[Pages 48950-48953]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-20243]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NM-217-AD]
RIN 2120-AA64


Airworthiness Directives; Boeing Model 747, 757, 767, and 777 
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 747, 757, 
767, and 777 series airplanes. This proposal would require modification 
of certain drip shields located on the flight deck, and follow-on 
actions. This action is necessary to prevent 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. 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-217-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-217-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-217-AD.'' 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-217-AD, 1601 Lind Avenue, SW., Renton, Washington 
98055-4056.

Discussion

    The FAA has received a report that; on certain Boeing Model 747, 
757, 767, and 777 series airplanes; the airplane manufacturer found 
some drip shields 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.

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 material used to manufacture the 
drip shields that are 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. However, while AD 2000-11-01 and AD 2000-11-02 
require replacement of MPET insulation blankets with new blankets, this 
proposed AD would require isolation of the drip shields from all 
potential

[[Page 48951]]

ignition sources rather than replacement of the drip shields. The 
decision to mandate modification of the drip shields rather than 
replacement of the drip shields with new drip shields made of another 
material is based on the difficulties associated with removing the drip 
shields from the airplane (for example, disassembly of flight deck and 
disconnection of wiring for flight controls). The FAA finds that, in 
lieu of replacement of the drip shields, modification of the drip 
shields to isolate them from all potential ignition sources will ensure 
an acceptable level of safety.
    A similar unsafe condition exists related to fiberglass insulation 
installed on the ducts of the environmental control system (ECS) on 
certain Boeing Model 737, 747, 757, and 767 series airplanes. 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 fiberglass insulation 
in the ECS ducts, which could propagate a small fire and lead to a 
larger fire. A separate rulemaking action [notice of proposed 
rulemaking, Rules Docket No. 2000-NM-226-AD] is being issued to address 
that unsafe condition on affected airplanes.

Explanation of Relevant Service Information

    The FAA has reviewed and approved Boeing Service Bulletins 747-25-
3253, 767-25-0290, and 777-25-0164; all including Appendices A, B, and 
C; all dated June 29, 2000; and 757-25-0226 and 757-25-0228; both 
including Appendices A, B, and C; both dated July 3, 2000. These 
service bulletins describe procedures for modification of certain drip 
shields located on the flight deck, and follow-on actions. The 
modification involves installation of fire blocks in areas where the 
drip shields are exposed to potential ignition sources. The fire block 
consists of fire-resistant flexible cargo liner fabric as a primary 
barrier. For large gaps between the drip shield and structure, the fire 
block uses fire-resistant foam and glass fabric. As follow-on actions, 
the service bulletins describe procedures for a one-time functional 
test of any system disturbed during the modification of the drip 
shields, and installation of placards to inform maintenance personnel 
that the drip shields have been fire blocked and any modification must 
be accomplished in accordance with the applicable service bulletin. 
Accomplishment of the actions specified in the service bulletins is 
intended to adequately address the identified unsafe condition.
    In addition, Boeing Service Bulletins 747-25-3253 and 767-25-0290 
describe procedures to allow sampling of the insulation and adhesive of 
the drip shields on certain airplanes, in lieu of the modification 
described above. The service bulletins recommend that operators take 
samples of the drip shields on these airplanes and submit the samples 
to Boeing for testing. If the testing of all of the samples yields 
positive results, modification of the airplane with fire blocks is not 
necessary. If the testing is negative, the airplane must be modified in 
accordance with the applicable service bulletin.

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 bulletins described previously, except as 
discussed below. For Model 747 and 767 series airplanes listed in Group 
1 in the applicable service bulletins, the proposed AD would allow 
accomplishment of the optional sampling of drip shields described 
previously.

Differences Between Proposed Rule and Service Bulletins

    Operators should note that the service bulletins specify that the 
modification of the drip shields is to be accomplished at the next 
heavy maintenance check. The FAA finds that such a compliance time will 
not ensure that the modifications are 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.
    In addition, operators should note that the service bulletins 
specify that methods for modification of any areas of the drip shield 
where wires or equipment were added on the outboard surface of the drip 
shield (that is, between the drip shield and the airplane structure) 
``must be approved separately.'' However, the service bulletins do not 
specify who must approve these methods. Therefore, paragraph (b) of 
this proposed AD specifies that modification of these areas must be 
accomplished in accordance with a method approved by the Manager, 
Seattle Aircraft Certification Office, FAA.
    Operators also should note that, although Boeing Service Bulletin 
777-25-0164 does not direct operators to perform a functional test on 
any system disturbed during the modification of the drip shield, the 
FAA has determined that such a functional test is necessary. Therefore, 
the functional tests required by paragraph (a)(2) of this AD applies to 
all airplanes affected by this AD. The functional tests must be 
accomplished in accordance with the applicable chapter of the 
applicable Airplane Maintenance Manual (AMM). Also, none of the 
relevant service bulletins specify corrective actions if any functional 
test fails. Therefore, paragraph (a)(2) of this AD requires, if any 
functional test fails, isolation of the fault, correction of the 
discrepancy in accordance with the applicable AMM, and repetition of 
the failed test until it is successfully accomplished.

Cost Impact

    There are approximately 3,137 airplanes of the affected design in 
the worldwide fleet. The FAA estimates that 999 airplanes of U.S. 
registry would be affected by this proposed AD. The following table 
shows the estimated cost impact for airplanes affected by this AD. The 
average labor rate is $60 per work hour. The estimated maximum total 
cost for all airplanes affected by this proposed AD is $3,695,460.

[[Page 48952]]



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                                                 U.S.-                                            Maximum  fleet
                    Model                      registered   Work hours   Labor cost   Parts cost       cost
                                               airplanes   (estimated)  (estimated)  (estimated)    (estimated)
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747.........................................          194           39       $2,340    $2,300 to      $1,132,960
                                                                                           3,500
757.........................................          491           26        1,560        1,700       1,600,660
767.........................................          258           17        1,020        2,300         856,560
777.........................................           56            3          180        1,700         105,280
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    For Model 747 and 767 series airplanes listed in Group 1 in the 
applicable service bulletin, in lieu of accomplishment of the 
modification of the drip shields, this proposed AD provides an option 
to take samples of the drip shields to determine if the modification is 
necessary. Therefore, the cost impact of this proposed AD as presented 
above may be reduced if some airplanes do not need the modification. 
For airplanes that accomplish the sampling, it would take approximately 
18 work hours, at an average labor rate of $60 per work hour. Based on 
these figures, the cost impact of the sampling on affected U.S. 
operators is estimated to be $1,080 per airplane.
    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-217-AD.

    Applicability: Model 747, 757, 767, and 777 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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747............................  1 through 1234 inclusive..................  1174, 1216
757............................  2 through 895 inclusive...................  870, 886, 894
767............................  1 through 768 inclusive...................  758
777............................  2 through 254 inclusive...................  120, 219, 230, 235, 242, 245, 249
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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 (d) 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 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, 
accomplish the following:

Modification

    (a) Within 5 years after the effective date of this AD, 
accomplish paragraphs (a)(1), (a)(2), and (a)(3) of this AD; in 
accordance with Boeing Service Bulletin 747-25-3253, 767-25-0290, or 
777-25-0164; all including Appendices A, B, and C; all dated June 
29, 2000; or 757-25-0226 or 757-25-0228; both including Appendices 
A, B, and C; both dated July 3, 2000; as applicable; except as 
provided by paragraph (b) of this AD.
    (1) Modify drip shields located on the flight deck by installing 
fire blocks.
    (2) Prior to further flight following accomplishment of 
paragraph (a)(1) of this AD, perform a functional test of any system 
disturbed by the modification, in accordance with the applicable 
service bulletin or the Airplane Maintenance Manual (AMM), as 
applicable. If any functional test fails, prior to further flight, 
isolate the fault, correct the

[[Page 48953]]

discrepancy in accordance with the applicable AMM, and repeat the 
failed test until it is successfully accomplished.
    (3) Prior to further flight following the accomplishment of 
paragraphs (a)(1) and (a)(2) of this AD, install placards on all 
modified drip shields.
    (b) If any wires or equipment are installed on the outboard 
surface of the drip shield (that is, between the drip shield and the 
airplane structure), modify that area in accordance with a method 
approved by the Manager, Seattle Aircraft Certification Office 
(ACO), FAA.

Optional Sampling (Certain Model 747 and 767 Series Airplanes)

    (c) For Model 747 and 767 series airplanes listed in Group 1 in 
Boeing Service Bulletins 747-25-3253 and 767-25-0290: In lieu of 
accomplishment of paragraph (a) of this AD, within 5 years after the 
effective date of this AD, collect samples of the insulation and 
adhesive of the drip shields, and submit the samples to the 
manufacturer for testing, in accordance with Boeing Service Bulletin 
747-25-3253 or 767-25-0290; both including Appendices A, B, and C; 
both dated June 29, 2000; as applicable.
    (1) If the test on all samples is positive, no further action is 
required by this AD.
    (2) If the test on any sample is negative, accomplish paragraph 
(a) of this AD before the compliance time specified in that 
paragraph.

Alternative Methods of Compliance

    (d) 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 ACO. 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

    (e) 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.

    Issued in Renton, Washington, on August 4, 2000.
Donald L. Riggin,
Acting Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 00-20243 Filed 8-9-00; 8:45 am]
BILLING CODE 4910-13-P