[Federal Register Volume 88, Number 47 (Friday, March 10, 2023)]
[Rules and Regulations]
[Pages 14874-14877]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-04848]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1058; Project Identifier AD-2022-00256-T; 
Amendment 39-22340; AD 2023-03-15]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2021-07-
09, which applies to all The Boeing Company Model 747-100, 747-100B, 
747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-400D, 
747-400F, 747SR, and 747SP series airplanes. AD 2021-07-09 required 
repetitively inspecting all trim air diffuser ducts or sidewall riser 
duct assemblies (collectively referred to as TADDs) for damage, 
including repetitive structural inspections of the center fuel tanks 
for damage, and performing applicable on-condition actions. Since the 
FAA issued AD 2021-07-09, the agency has determined that the existing 
requirements do not adequately address the unsafe condition. This AD 
continues to require repetitive inspections of the TADDs for damage, 
with revised compliance times, and repair if applicable. This AD also 
requires repetitive replacement of the TADDs and removes the structural 
inspections of the center fuel tanks. This AD also prohibits the 
installation of affected parts. This AD removes certain airplanes from 
the applicability. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective April 14, 2023.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in this AD as of April 14, 
2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2022-1058; or in person at Docket Operations between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD 
docket contains this final rule, any comments received, and other 
information. The address for Docket Operations is U.S. Department of 
Transportation, Docket Operations, M-30, West Building Ground Floor, 
Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
    Material Incorporated by Reference:
     For service information identified in this final rule, 
contact Boeing Commercial Airplanes, Attention: Contractual & Data 
Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 
90740-5600; telephone 562-797-1717; internet myboeingfleet.com.
     You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety Branch, 2200 South 
216th St., Des Moines, WA. For information on the availability of this 
material at the FAA, call 206-231-3195. It is also available at 
regulations.gov under Docket No. FAA-2022-1058.

FOR FURTHER INFORMATION CONTACT: Nicole S. Tsang, Aerospace Engineer, 
Cabin Safety and Environmental Systems Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-
3959; email: [email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2021-07-09, Amendment 39-21486 (86 FR 
17899, April 7, 2021) (AD 2021-07-09). AD 2021-07-09 applied to all The 
Boeing Company Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-
200C, 747-200F, 747-300, 747-400, 747-400D, 747-400F, 747SR, and 747SP 
series airplanes. The NPRM published in the Federal Register on 
September 8, 2022 (87 FR 54919). The NPRM was prompted by reports of 
sealant deteriorating on the outside of the center wing fuel tank and 
analysis showing that sealant may deteriorate inside the tank due to 
excess heat from TADDs. The NPRM was also prompted by reports 
indicating that the high temperature composite material TADD failed. AD 
2021-07-09 requires replacing original fiberglass fabric material with 
high temperature composite material TADDs, repetitively inspecting the 
TADDs for damage, and

[[Page 14875]]

as applicable inspecting the center wing fuel tank secondary fuel 
barrier coating and primary sealant for damage, and repairing damage. 
In the NPRM, the FAA proposed to continue to require repetitive 
inspections of the TADDs for damage, with revised compliance times, and 
repair if applicable. The NPRM also proposed to require repetitive 
replacement of the TADDs and remove the structural inspections of the 
center fuel tanks. In addition, this AD prohibits the installation of 
affected parts. The FAA is issuing this AD to address potential hot air 
leakage from original fiberglass fabric material or high temperature 
composite material TADD that can cause damage to the center wing fuel 
tank secondary fuel barrier coating and primary sealant, which can 
cause fuel leakage into an ignition zone, possibly resulting in a fire 
or explosion.
    For information on the procedures and compliance times, see the 
service information at regulations.gov under Docket No. FAA-2022-1058.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from four commenters. Commenters included 
Air Line Pilots Association, International (ALPA) who supported the 
NPRM without change, and an individual whose comment is outside the 
scope of this rulemaking. The FAA received additional comments from 
Boeing and another commenter. The following presents the comments 
received on the NPRM and the FAA's response to each comment.

Request for Clarification on Credit for Previous Actions

    A commenter asked if an operator can claim full credit against the 
proposed AD if the operator with Group 2 airplanes performed Boeing 
Service Bulletin 747-21A2577-00 and conducted the TADD replacement 
associated with certain comments from AD 2021-07-09 in order to extend 
the inspection interval.
    The FAA infers the commenter is referring to the FAA's response to 
a comment in AD 2021-07-09. That response states as follows:

    After initial installation of high temperature TADDs, operators 
may avoid repeat inspections at 1,200 FH intervals by installing new 
high temperature TADDs at each 16,000 FH interval, without an 
alternative method of compliance (AMOC) or additional rulemaking, as 
long as required actions are completed at that interval.

    The FAA infers the commenter is requesting the same allowance from 
the FAA's response to the comment in AD 2021-07-09 to replace the TADD 
in lieu of performing repetitive inspections of the TADD at 1,200-
flight-hour intervals. The FAA provides the following clarifications of 
the AD requirements. This AD requires operators to perform repetitive 
inspection of the TADD, report any TADD damages to Boeing, and replace 
the TADD at 16,000-flight-hour intervals. This AD does not provide an 
option for a TADD to continue in service after 16,000 flight hours.
    The proposed AD would have required Boeing Alert Requirements 
Bulletin 747-21A2577 RB, Revision 1, dated March 9, 2022. This AD has 
been revised to require Boeing Alert Requirements Bulletin 747-21A2577 
RB, Revision 2, dated February 10, 2023. However, paragraph (j) of this 
AD provides credit for actions done before the effective date of the AD 
using Boeing Alert Requirements Bulletin 747-21A2577 RB, dated February 
18, 2020; or Revision 1, dated March 9, 2022.

Request for Change in Applicability

    Boeing requested that the FAA revise paragraph (c), 
``Applicability,'' of the proposed AD to remove the following Model 747 
Large Cargo Freighters (LCF) airplanes: variable numbers RT631, RT743, 
RT876, and RT632. The listed LCF airplanes should not be applicable 
because the listed LCF airplanes do not have original fiberglass fabric 
material or high temperature composite material TADD.
    The FAA agrees with the request for the reasons provided by the 
commenter. The FAA notes that paragraph 1.A., ``Effectivity,'' of 
Boeing Alert Requirements Bulletin 747-21A2577 RB, Revision 2, dated 
February 10, 2023, specifically excludes line numbers 766, 778, 904, 
and 932 (variable numbers RT631, RT743, RT876, and RT632). The FAA 
revised paragraph (c) of this AD to limit the applicability to 
airplanes identified in Boeing Alert Requirements Bulletin 747-21A2577 
RB, Revision 2, dated February 10, 2023.

Request for Change to the Service Bulletins Cited

    Boeing requested the FAA to reference Revision 2 instead of 
Revision 1 of Service Bulletin and Requirements Bulletin 747-21A2577. 
Revision 2 of this service information will address the issue of 
Appendix A and Appendix B not being in the RB.
    The FAA agrees with Boeing's request. As stated previously, the FAA 
has revised this AD to require Boeing Alert Requirements Bulletin 747-
21A2577 RB, Revision 2, dated February 10, 2023. Revision 2 added the 
missing appendixes and introduces no other changes that affect 
compliance.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 747-21A2577 RB, 
Revision 2, dated February 10, 2023. This service information specifies 
procedures for repetitive detailed inspections for damage of TADDs made 
of original fiberglass fabric material and high temperature composite 
material, repetitive replacement of TADDs, and repair of damaged TADDs. 
This service information is reasonably available because the interested 
parties have access to it through their normal course of business or by 
the means identified in ADDRESSES.

Costs of Compliance

    The FAA estimates that this AD affects 104 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
             Action                   Labor cost          Parts cost       Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Retained repetitive inspections   Up to 44 work-      $0................  Up to $3,740 per    Up to $388,960 per
 (AD2021-07-09).                   hours x $85 per                         inspection cycle.   inspection cycle.
                                   hour = up to
                                   $3,740 per
                                   inspection cycle.

[[Page 14876]]

 
Repetitive TADD replacement.....  Up to 49 work-      Up to $12,000.....  Up to $16,165 per   Up to $1,681,160
                                   hours x $85 per                         inspection cycle.   per replacement
                                   hour = $4,165 per                                           cycle.
                                   replacement cycle.
----------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data on which to base the cost 
estimates for the on-condition repairs specified in this AD.
    The FAA has included all known costs in its cost estimate. 
According to the manufacturer, however, some or all of the costs of 
this AD may be covered under warranty, thereby reducing the cost impact 
on affected operators.

Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

    This AD will not have federalism implications under Executive Order 
13132. This AD 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.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Will not affect intrastate aviation in Alaska, 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.

List of Subjects in 14 CFR Part 39

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

The Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. The FAA amends Sec.  39.13 by:
0
a. Removing Airworthiness Directive (AD) 2021-07-09, Amendment 39-21486 
(86 FR 17899, April 7, 2021); and
0
b. Adding the following new AD:

2023-03-15 The Boeing Company: Amendment 39-22340; Docket No. FAA-
2022-1058; Project Identifier AD-2022-00256-T.

(a) Effective Date

    This airworthiness directive (AD) is effective April 14, 2023.

(b) Affected ADs

    This AD replaces AD 2021-07-09, Amendment 39-21486 (86 FR 17899, 
April 7, 2021) (AD 2021-07-09).

(c) Applicability

    This AD applies to The Boeing Company Model 747-100, 747-100B, 
747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747-400, 747-
400D, 747-400F, 747SR, and 747SP series airplanes, certificated in 
any category, as identified in Boeing Alert Requirements Bulletin 
747-21A2577 RB, Revision 2, dated February 10, 2023.

(d) Subject

    Air Transport Association (ATA) of America Code: 21, Air 
conditioning.

(e) Unsafe Condition

    This AD was prompted by reports of sealant deteriorating on the 
outside of the center wing fuel tank and analysis showing that 
sealant could deteriorate inside the fuel tank due to excess heat 
from trim air diffuser ducts or sidewall riser duct assemblies 
(collectively referred to as TADDs), and by the determination that 
existing requirements do not adequately address the unsafe 
condition. The FAA is issuing this AD to address potential hot air 
leakage from original fiberglass fabric material or high temperature 
composite material TADDs that can cause damage to the center wing 
fuel tank secondary fuel barrier coating and primary sealant, which 
can cause fuel leakage into an ignition zone, possibly resulting in 
a fire or explosion.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Required Actions

    Except as specified by paragraph (h) of this AD: At the 
applicable times specified in the ``Compliance'' paragraph of Boeing 
Alert Requirements Bulletin 747-21A2577 RB, Revision 2, dated 
February 10, 2023, do all applicable actions identified in, and in 
accordance with, the Accomplishment Instructions of Boeing Alert 
Requirements Bulletin 747-21A2577 RB, Revision 2, dated February 10, 
2023.

    Note 1 to paragraph (g):  Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
747-21A2577, Revision 2, dated February 10, 2023, which is referred 
to in Boeing Alert Requirements Bulletin 747-21A2577 RB, Revision 2, 
dated February 10, 2023.

(h) Exceptions to Service Information Specifications

    (1) Where the Compliance Time column of the tables in the 
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 747-
21A2577 RB, Revision 2, dated February 10, 2023, uses the phrase 
``the Revision 1 date of Requirements Bulletin 747-21A2577 RB,'' 
this AD requires using ``the effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 747-21A2577 RB, 
Revision 2, dated February 10, 2023, specifies contacting Boeing for 
repair instructions: This AD requires doing the repair before 
further flight using a method approved in accordance with the 
procedures specified in paragraph (k) of this AD.

(i) Parts Installation Prohibition

    As of the effective date of this AD, no person may install an 
original fiberglass fabric material TADD assembly, having a part 
number listed in Appendix A of Boeing Alert Requirements Bulletin 
747-21A2577 RB, Revision 2, dated February 10, 2023, on any 
airplane.

(j) Credit for Previous Actions

    This paragraph provides credit for the actions specified in 
paragraph (g) of this AD, if those actions were performed before the 
effective date of this AD using the service

[[Page 14877]]

information identified in paragraph (j)(1) or (2) of this AD.
    (1) Boeing Alert Requirements Bulletin 747-21A2577 RB, dated 
February 18, 2020, which was incorporated by reference in AD 2021-
07-09.
    (2) Boeing Alert Requirements Bulletin 747-21A2577 RB, Revision 
1, dated March 9, 2022, which is not incorporated by reference in 
this AD.

(k) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Seattle ACO Branch, FAA, has the authority to 
approve AMOCs for this AD, if requested using the procedures found 
in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request 
to your principal inspector or responsible Flight Standards Office, 
as appropriate. If sending information directly to the manager of 
the certification office, send it to the attention of the person 
identified in paragraph (l) of this AD. Information may be emailed 
to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by The Boeing Company Organization Designation 
Authorization (ODA) that has been authorized by the Manager, Seattle 
ACO Branch, FAA, to make those findings. To be approved, the repair 
method, modification deviation, or alteration deviation must meet 
the certification basis of the airplane, and the approval must 
specifically refer to this AD.
    (4) AMOCs approved for AD 2021-07-09 are approved as AMOCs for 
the corresponding provisions of Boeing Alert Requirements Bulletin 
747-21A2577 RB, Revision 2, dated February 10, 2023, that are 
required by paragraph (g) of this AD.

(l) Related Information

    For more information about this AD, contact Nicole S. Tsang, 
Aerospace Engineer, Cabin Safety and Environmental Systems Section, 
FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; 
phone: 206-231-3959; email: [email protected].

(m) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) Boeing Alert Requirements Bulletin 747-21A2577 RB, Revision 
2, dated February 10, 2023.
    (ii) [Reserved]
    (3) For service information identified in this AD, contact 
Boeing Commercial Airplanes, Attention: Contractual & Data Services 
(C&DS), 2600 Westminster Blvd., MC 110 SK57, Seal Beach, CA 90740-
5600; telephone 562-797-1717; internet myboeingfleet.com. You may 
view this referenced service information at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 2200 South 216th St., 
Des Moines, WA. For information on the availability of this material 
at the FAA, call 206-231-3195.
    (4) You may view this service information at the FAA, 
Airworthiness Products Section, Operational Safety Branch, 2200 
South 216th St., Des Moines, WA. For information on the availability 
of this material at the FAA, call 206-231-3195.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, email [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on February 25, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-04848 Filed 3-9-23; 8:45 am]
BILLING CODE 4910-13-P


