[Federal Register Volume 88, Number 39 (Tuesday, February 28, 2023)]
[Rules and Regulations]
[Pages 12550-12557]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-04024]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0810; Project Identifier AD-2021-01238-T; 
Amendment 39-22329; AD 2023-03-04]
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 adopting a new airworthiness directive (AD) for all 
The Boeing Company Model 777 airplanes. This AD was prompted by fuel 
system reviews conducted by the manufacturer.

[[Page 12551]]

This AD requires, depending on the airplane configuration, installation 
of Teflon sleeves, cap sealing of fasteners, detailed inspections, and 
corrective actions. This AD also requires revising the existing 
maintenance or inspection program, as applicable, to incorporate more 
restrictive airworthiness limitations (AWLs). The FAA is issuing this 
AD to address the unsafe condition on these products.

DATES: This AD is effective April 4, 2023.
    The Director of the Federal Register approved the incorporation by 
reference of certain publications listed in this AD as of April 4, 
2023.

ADDRESSES: 
    AD Docket: You may examine the AD docket at regulations.gov under 
Docket No. FAA-2022-0810; 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; website 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-2022-0810.

FOR FURTHER INFORMATION CONTACT: Kevin Nguyen, Aerospace Engineer, 
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3555; email: 
[email protected].

SUPPLEMENTARY INFORMATION: 

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 by adding an AD that would apply to all The Boeing Company 
Model 777 airplanes. The NPRM published in the Federal Register on July 
26, 2022 (87 FR 44285). The NPRM was prompted by fuel system reviews 
conducted by the manufacturer. In the NPRM, the FAA proposed to 
require, depending on the airplane configuration, installation of 
Teflon sleeves, cap sealing of fasteners, detailed inspections, and 
corrective actions. The FAA also proposed to require revising the 
existing maintenance or inspection program, as applicable, to 
incorporate more restrictive AWLs. The FAA is issuing this AD to 
address arcing inside the main and center fuel tanks in the event of a 
fault current or lightning strike, which, in combination with flammable 
fuel vapors, could result in a fuel tank explosion and consequent loss 
of the airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received a comment from The Air Line Pilots Association, 
International (ALPA), who supported the NPRM without change.
    The FAA received additional comments from seven commenters, 
including American Airlines (AAL), Boeing, Emirates, Royal Dutch 
Airlines (KLM), Air France Industries (AFA), FedEx, and United Airlines 
(UAL). The following presents the comments received on the NPRM and the 
FAA's response to each comment.

Request To Require a Later Revision of the Service Information

    AFA, KLM, and UAL requested that Boeing Alert Service Bulletin 777-
57A0050, Revision 7 (SB 777-57A0050, Revision 7), be mandated by the 
final rule instead of Boeing Alert Service Bulletin 777-57A0050, 
Revision 6, dated August 18, 2021 (SB 777-57A0050, Revision 6). AFA 
asserted that following release of SB 777-57A0050, Revision 6, they 
discussed with Boeing certain errors in SB 777-57A0050, Revision 6, 
that will be corrected in SB 777-57A0050, Revision 7.
    KLM explained that the NPRM contains technical detail that should 
not be included in a high level regulation such as an AD, and that it 
could possibly lead to confusion and mistakes by airline staff. KLM 
stated that, for example, in paragraphs (h)(2), (3), and (4) of the 
proposed AD, it does not specify exactly which seven fasteners should 
be inspected and sealed. KLM noted that according to Figures 172, 173, 
174, 175, 176, 179 and 180 of SB 777-57A0050, Revision 6, there are 
more than seven fasteners located on the inboard side of rib no. 9 and 
the proposed AD does not specify exactly which seven fasteners should 
be inspected/sealed. KLM requested that the FAA clarify which seven 
fasteners should be inspected/sealed exactly and recommend that the 
service information should first be revised by the original equipment 
manufacturer (OEM) and requested that the FAA allow the OEM to revise 
the service information before issuing the final rule.
    UAL requested that the final AD mandate SB 777-57A0050, Revision 7, 
to ensure an additional work package is included for airplanes that 
accomplished SB 777-57A0050, Revision 6, without the exceptions 
specified in paragraph (h) of the proposed AD. UAL explained that 
paragraph (h) of the proposed AD provides exceptions to SB 777-57A0050, 
Revision 6, for known errors within the service bulletin. UAL stated 
that since SB 777-57A0050, Revision 6, was an alternative method of 
compliance (AMOC) to paragraphs (g)(1), (i), (j), and (k)(1) through 
(3) of AD 2017-11-14, Amendment 39-18913 (82 FR 25954, June 6, 2017) 
(AD 2017-11-14), operators may have previously complied with it without 
the deviations or exceptions provided in paragraph (h) of the proposed 
AD. UAL stated this proposed AD does not address how to correct that 
condition. UAL noted that Boeing is developing SB 777-57A0050, Revision 
7, to address the exceptions in paragraph (h) of the proposed AD, and 
to include new Groups and Configurations for airplanes that have 
accomplished SB 777-57A0050, Revision 6. UAL further stated that an 
additional work package is required to inspect and/or correct the 
erroneous work instructions from SB 777-57A0050, Revision 6.
    The FAA does not agree with the request to refer to SB 777-57A0050, 
Revision 7, because it is not known when Revision 7 will be available. 
The FAA is aware of the errors of SB 777-57A0050, Revision 6, as 
identified by the commenters, and the exceptions specified in paragraph 
(h) of this AD address errors that affect addressing the unsafe 
condition. The FAA notes that paragraphs (h)(2) through (4) of the 
proposed AD provided adequate information to identify the location of 
the fasteners in Figures 172, 173, 174, 175, 176, 179 and 180 of SB 
777-57A0050, Revision 6. However, the FAA has added additional 
information to paragraphs (h)(2) through (4) of this AD to help clarify 
the location of the affected fasteners by specifying if the fasteners 
are adjacent to the right or left side of the identified fasteners. As 
specified in the comment responses that follow, other errors are 
addressed by the exceptions specified in paragraphs (h)(5) through (7) 
of this AD. The FAA

[[Page 12552]]

considers SB 777-57A0050, Revision 6, and the information provided in 
paragraphs (h)(2) through (7) of this AD as adequate accomplishment 
instructions to correct the unsafe condition. As specified in paragraph 
(l)(1) of this AD, accomplishment of the actions required by paragraph 
(g) of this AD terminates the requirements of paragraphs (g)(1), (i), 
and (j) of AD 2017-11-14. Therefore, the FAA considers that delaying 
this AD action until the availability of Revision 7 of SB 777-57A0050 
would not be warranted.

Request To Include Service Bulletin Revision Information

    AFA expressed that certain airplane maintenance manual (AMM) task 
instructions relating to ``POST-SB'' should include information about 
the revision of Boeing Alert Service Bulletin 777-57A0050 that was 
accomplished. As part of AFA's request to mandate SB 777-57A0050, 
Revision 7, AFA explained that the AMM TASK 28-22-00-210-801 
instructions, related to Airworthiness Limitations (AWLs) 28-AWL-31 and 
28-AWL-32, depend on the service bulletin status. However, AFA noted 
the AMM task is only marked ``POST-SB,'' and there is no mention of the 
service bulletin revision.
    The FAA does not agree with this request because AMM task 28-22-00-
210-801 is not required by this AD. AMM task 28-22-00 is referenced in 
AWLs 28-AWL-31 and 28-AWL-32, which specify in the applicability column 
``Airplanes that have incorporated Service Bulletin 777-57A0050.'' As 
required by paragraph (i) of this AD, operators must revise the 
existing maintenance or inspection program, as applicable, to 
incorporate the information for 28-AWL-31 and 28-AWL-32. However, AWLs 
28-AWL-31 and 28-AWL-32 do not specify the service bulletin revision in 
the applicability column; therefore, there is not a requirement to 
identify AMMs as ``POST-SB'' with a service bulletin revision. No 
changes have been made to this AD based on this request.

Request To Clarify Compliance Time

    AFA requested additional clarification of the compliance time. AFA 
stated that earlier revisions of SB 777-57A0050, have different 
scheduling rules, and that the instructions given in SB 777-57A0050, 
Revision 6, depend on the accomplished work.
    The FAA agrees with providing clarification regarding the 
compliance time. The FAA has previously issued AD 2011-26-03, Amendment 
39-16893 (76 FR 78138, December 16, 2011) (AD 2011-26-03), which 
mandated Boeing Alert Service Bulletin 777-57A0050, Revision 2, dated 
May 14, 2009 (SB 777-57A0050, Revision 2). Boeing Alert Service 
Bulletin 777-57A0050, Revision 3, dated February 18, 2014 (777-57A0050, 
Revision 3) was approved as an AMOC with the requirements of AD 2011-
26-03. That AD was superseded by AD 2017-11-14, which retained the 
requirements of AD 2011-26-03 and also mandated Boeing Alert Service 
Bulletin 777-57A0050, Revision 4, dated September 28, 2015 (SB 777-
57A0050, Revision 4) for certain groups of airplanes specified in that 
revision. After issuance of AD 2017-11-14, the FAA determined that a 
new AD would be necessary to mandate a later revision of Boeing Alert 
Service Bulletin 777-57A0050 because more airplanes are affected by the 
identified unsafe condition, and additional work is required for 
airplanes on which earlier revisions of the service information has 
been incorporated.
    Paragraph 1.E., ``Compliance,'' of SB 777-57A0050, Revision 6, 
specifies the compliance times for all groups and configurations, 
except as specified in paragraph (h)(1) of this AD. For example, for 
those airplanes in SB 777-57A0050, Revision 6, that have already been 
identified in SB 777-57A0050, Revisions 2, 3, or 4, the compliance 
times specified in AD 2017-11-14 would apply. Specifically, for 
airplanes identified in SB 777-57A0050, Revision 2 or 3, the actions 
specified in SB 777-57A0050, Revision 2 or 3 should have been 
accomplished within 60 months after January 20, 2011 (the effective 
date of AD 2010-24-12, Amendment 39-16531 (75 FR 78588, December 16, 
2010)). For airplanes identified in SB 777-57A0050, Revision 4 but not 
in earlier revisions, the actions specified in SB 777-57A0050, Revision 
4 should have been accomplished within 60 months after July 11, 2017 
(the effective date of AD 2017-11-14). For the rest of the airplane 
groups and configurations identified in SB 777-57A0050, Revision 6, the 
actions specified must be accomplished within 60 months after the 
effective date of this AD. Operators should also note that paragraph 
(l)(1) of this AD explains that accomplishment of the actions required 
by paragraph (g) of this AD terminates paragraphs (g)(1), (i), and (j) 
of AD 2017-11-14.

Request To Add Credit for Previous Actions

    FedEx requests the addition of a ``Credit for Previous Action'' 
paragraph to any final AD to ensure previous modifications per SB 777-
57A0050, Revision 5, or earlier revisions do not have to be repeated. 
FedEx stated that they are already doing the applicable added tasks 
from the SB 777-57A0050, Revision 6, which has been approved as an AMOC 
to AD 2017-11-14 and expressed concern that the required actions in 
paragraph (g) of the proposed AD do not account for prior maintenance 
actions done to comply with AD 2017-11-14.
    The FAA declines to provide credit for the accomplishment of an 
earlier service bulletin revision, because accomplishing the actions 
specified in a revision earlier than SB 777-57A0050, Revision 6, on an 
airplane does not necessarily mean that all applicable actions 
specified in SB 777-57A0050, Revision 6, were accomplished on that 
airplane to address the unsafe condition. The groups and configuration 
in SB 777-57A0050, Revision 6, are dependent on which actions have 
already been accomplished in accordance with earlier revisions. 
Operators are required to determine whether additional work is required 
by SB 777-57A0050, Revision 6, on each affected airplane that has 
incorporated the actions specified in an earlier revision of the 
service bulletin. If no additional work is required to address the 
unsafe condition, then that airplane is in compliance with this new AD. 
This AD has not been changed with regard to this request.

Request To Include a New Exception

    AAL requested that paragraph (h) of the proposed AD include an 
exception to exclude Group 1 through 4 from Work Package 28 of Boeing 
Alert Service Bulletin 777-57A0050, Revision 6, because that work 
package is not applicable to Groups 1 through 4. AAL stated that Boeing 
has confirmed this to be accurate. AFA also stated that Work Package 28 
is not applicable to Group 1 through 4.
    The FAA has confirmed with Boeing that the error described by the 
commenters exists in the service information. The FAA has added 
paragraph (h)(5) to this AD, which reads ``Where Boeing Alert Service 
Bulletin 777-57A0050, Revision 6, dated August 18, 2021, specifies Work 
Package 28 as applicable to Group 1 through 4, and Group 8, this AD 
does not require accomplishment of Work Package 28 for Group 1 through 
4.''

Request To Clarify Access Steps for Work Packages 37, 38 and 39

    AFA requested that the access steps for Work Packages 37, 38, and 
39 of Boeing Alert Service Bulletin 777-57A0050, Revision 6, be 
clarified. AFA stated that for Model 777-200, -200ER, and -300 series 
airplanes, the rib 9 cap

[[Page 12553]]

sealing location is located in the dry-bay. AFA stated that Boeing 
confirmed that access door 532AB for the dry bay should be used to 
access the location for Figure 172, and confirmed fuel tank purging is 
not necessary for Work Package 37. AFA also stated that for Model 777-
200LR and -300ER series airplanes, the rib 9 cap sealing location is 
located in the center fuel tank. AFA stated that Boeing confirmed that 
access door 531AB for the center fuel tank should be used to access the 
location for Figure 172, and confirmed the center fuel tank should be 
purged for Work Package 37.
    AFA also stated that for Group 12, 14 through 41, 44 through 48, 55 
through 57, 59-83, in Work Packages 38 and 39 of Boeing Alert Service 
Bulletin 777-57A0050, Revision 6, Boeing agreed that at the rib 9 front 
spar location, access door 531CB/631CB would be sufficient, and purge/
ventilation of the center tank would be necessary.
    The FAA acknowledges that different access doors might be used for 
certain airplanes for a given work package. As specified in Note 11. of 
paragraph 3.A. ``General,'' of Boeing Alert Service Bulletin 777-
57A0050, Revision 6: ``If it is necessary to remove more parts for 
access, you can remove those parts. If you can get access without 
removing identified parts, it is not necessary to remove all of the 
identified parts.'' The removal of access doors and purging of fuel 
tanks are not actions that address the identified unsafe condition. The 
FAA has determined delaying this final rule by adding exceptions to 
identity applicable access doors and corresponding fuel tanks, as well 
as corresponding procedures, is not warranted. The FAA has not changed 
this AD in this regard. However, in order to not purge a specific tank 
that is specified in a work package or purge the tank for a different 
access door, the FAA has added paragraph (h)(7) to this AD that 
specifies ``Where the Accomplishment Instructions of Boeing Alert 
Service Bulletin 777-57A0050, Revision 6, dated August 18, 2021, 
specifies to purge specific fuel tanks (right, left, or center), 
operators must purge the applicable fuel tank for which access inside 
the fuel tank is needed to apply cap sealing on the affected 
fasteners.''

Request To Not Require Work Package 38 for Certain Groups

    AFA stated that Boeing confirmed that for Group 1 through 4 
airplanes, Work Package 38 of Boeing Alert Service Bulletin 777-
57A0050, Revision 6, provides the same instructions as Work Package 37, 
and is not needed if Work Package 37 is accomplished.
    The FAA confirmed with Boeing that Work Package 38 is not necessary 
for Group 1 to 4 provided Work Package 37 has been accomplished. The 
FAA has added paragraph (h)(6) to this AD to clarify that for Group 1 
through 4 airplanes on which Work Package 37 has been accomplished, 
Work Package 38 is not required.

Request To Refer to Latest Maintenance Planning Document (MPD) or Delay 
Publication of the Final Rule

    Boeing, and Emirates requested that the proposed AD be revised to 
refer to the latest MPD. In addition, KLM, requested that the final 
rule be delayed until a later MPD is published that addresses certain 
discrepancies.
    Boeing requested that the final rule be issued after the latest MPD 
revision has been approved by the FAA and published, and that paragraph 
(j) of the proposed AD be deleted. Boeing requested that the AD be 
posted following the approval of the revised MPD. Boeing explained that 
paragraph (j) of the proposed AD refers to changes prescribed by the 
FAA within AWL No. 28-AWL-31 and 28-AWL-32. Since these changes will 
have likely been approved by the FAA and published in the 777 MPD prior 
to the AD being posted, Boeing asserted that there will be no need for 
these AWL sub-paragraphs to be specifically called out in the AD.
    Emirates requested that the Boeing MPD document D622W001-9, dated 
March 2022, referenced in paragraphs (i) and (j) of the proposed AD be 
replaced by the revision dated July 2022. Emirates explained that 
paragraphs (i) and (j) of the proposed AD refer to ``Airworthiness 
Limitations (AWLs) and Certification Maintenance Requirements (CMRs), 
D622W001-9, dated March 2022'' while the latest revision of this MPD 
document is dated July 2022.
    KLM requested that the AD not be issued until after the subject MPD 
is revised by the OEM or that the FAA explain the reason why it should 
not be delayed.
    The FAA agrees to refer to the latest MPD. Airworthiness 
Limitations (AWLs) and Certification Maintenance Requirements (CMRs), 
D622W001-9, dated August 2022, of Boeing 777 200/200LR/300/300ER/777F 
Maintenance Planning Data (MPD) Document, has been published, and it 
contains corrections that address the exceptions given in paragraph (j) 
of the proposed AD. Paragraph (i) of this AD has been updated to 
include this revision. Paragraph (j) of this AD has also been changed 
to give credit for the March 2022, June 2022, and July 2022 revisions 
of the MPD, provided that the corrections specified in paragraphs 
(j)(1) through (4) of this AD are met.

Request To Clarify Applicability for an AWL Task

    KLM requested that the FAA clarify an applicability for an AWL 
task. KLM stated paragraphs (j)(1) through (4) of the proposed AD 
provides details of changes to the content of the MPD document (ALI and 
CMR), which includes changes to the applicability for certain 
paragraphs of that document. KLM stated AWL 28-AWL-32 was already part 
of AD 2021-24-12, Amendment 39-21833 (86 FR 73660, December 28, 2021) 
(AD 2021-24-12), which has an applicability of ``The Boeing Company 
Model 777-200, -200LR, -300, -300ER, and 777F series airplanes, 
certificated in any category, having line numbers (L/Ns) 1 through 1609 
inclusive.'' KLM stated paragraphs (j)(1) through (4) of the proposed 
AD narrow this applicability down or widens it without AD 2021-24-12 
being superseded. KLM concluded this will lead to confusion.
    The FAA notes that paragraph (j) of the proposed AD does not affect 
any aspect of AD 2021-24-12. The applicability of AD 2021-24-12 
identifies the airplanes affected by the requirements of that AD. 
Paragraph (j) of the proposed AD clarifies information for certain 
steps within an AWL. Compliance with each AWL must be accomplished 
based on the applicability specified in the Applicability block of each 
AWL. The applicability of the AD affects whom must incorporate that AWL 
into their maintenance or inspection program. The applicability of an 
AWL neither affects nor is affected by the applicability of the AD that 
mandated the incorporation of that AWL into the maintenance or 
inspection program, unless specifically stated in an exception of the 
regulatory text of an AD.
    Paragraph (j) of the proposed AD does not change the applicability 
block of AWL No. 28-AWL-31 and No. 28-AWL-32. Paragraph (j) of the 
proposed AD is just intended to provide a clear definition of the 
affected models and affected airplane line number ranges for certain 
paragraphs or steps within AWL No. 28-AWL-31 and 28-AWL-32. Due to 
unclear title descriptions, there was confusion as to what the 
applicable affected models were for those paragraphs. As a result, 
paragraph (j) was added to the proposed AD to provide clarification on 
the affected models.

[[Page 12554]]

    As stated previously, the FAA has redesignated paragraph (j) of the 
proposed AD as a credit paragraph since the latest revision of the MPD 
incorporates those changes. The information in paragraph (j) of this AD 
will only be necessary if an MPD dated earlier than August 2022 is 
used. Compliance with the requirements of both paragraph (i) of this AD 
and paragraph (g) of AD 2021-24-12 can be accomplished by using 
Airworthiness Limitations (AWLs) and Certification Maintenance 
Requirements (CMRs), D622W001-9, dated August 2022, of Boeing 777 200/
200LR/300/300ER/777F Maintenance Planning Data (MPD) Document. 
Paragraph (l)(2) of this AD specifies that accomplishment of the 
revision required by paragraph (i) of this AD to incorporate the 
information for 28-AWL-31 and 28-AWL-32 terminates the requirements of 
paragraphs (g)(6) and (h) of AD 2021-24-12.

Request for Clarification of Compliance Time

    Emirates asked whether airplanes need to be inspected again within 
60 months after the effective date of the proposed AD per paragraph 
(i)(2) of the proposed AD when those airplanes have already been 
inspected in accordance with AWL No. 28-AWL-32 based on the initial 
compliance time specified in paragraph (g)(6) of AD 2021-24-12. 
Emirates did not ask for any specific change.
    Although the commenter did not ask for a change, the FAA notes that 
paragraph (i)(1) and (2) of the proposed AD should provide credit for 
the inspection that has already been performed under the initial 
compliance time specified in paragraph (g)(6) of AD 2021-24-12. Without 
this credit, an airplane inspected under the initial compliance time 
specified in paragraph (g)(6) of AD 2021-24-12 may need to be re-
inspected under the initial compliance time specified in paragraph 
(i)(1) or (2) of the proposed AD. This is not the intent of paragraphs 
(i)(1) and (2) of the proposed AD. To give credit for the inspection 
already accomplished under the initial compliance time specified in 
paragraph (g)(6) of AD 2021-24-12, the FAA has revised paragraphs 
(i)(1) and (2) of this AD to include ``within 3,750 days after the most 
recent inspection was performed as specified in AWL No. 28-AWL-32'' as 
part of the initial compliance time.

Request for Alternate Teflon Sleeve Solution

    Emirates stated that an alternate sleeve should be part of the next 
service bulletin revision, and accepted as an alternative in the 
proposed AD. Emirates stated that following release of SB 777-57A0050, 
Revision 6, there was a worldwide material shortage of TFE-2X Standard 
Wall--TEFLON SLEEVE 1 inch diameter. Emirates stated that Boeing 
identified M23053/12 Class 2 and M23053/12 Class 5 as suitable 
alternatives, depending on the diameter of the wire bundles.
    According to Emirates, Boeing stated the following: M23053/12 Class 
2 sleeves are a suitable alternative for the TFE-2X Standard Wall 
sleeve for wire bundles up to 1 inch in diameter and noted the sleeves 
are listed as an alternative in the standard wiring practices manual 
(SWPM) Section 20-00-11 Table 31. Boeing advised that they are working 
on a Global AMOC for alternative sleeve options for wire bundles 
greater than 1 inch in diameter. For the larger bundles, Boeing 
proposed using thinner M23053/12 Class 5 sleeves (for example M23053/
12-519-C) and wrapping them twice around the bundle, which provides the 
same wall thickness as the Class 2 Standard Wall sleeves. Boeing 
concluded that because this double-wrapped installation will require an 
FAA AMOC approval, Boeing needs to be notified of this deviation.
    The FAA does not agree to include alternative sleeving in this AD. 
The FAA will review alternative sleeving if it is included in the next 
service bulletin revision or if Boeing or an operator submits an AMOC 
request under the provisions of paragraph (m) of this AD. The FAA will 
consider requests for alternate sleeving if sufficient data are 
submitted to substantiate that the change would provide an acceptable 
level of safety.

Request To Remove ``Before Further Flight''

    FedEx objected to the last sentence of paragraph (g) of the 
proposed AD, ``Do all applicable corrective actions before further 
flight.'' The FAA infers that FedEx requested that the FAA remove the 
sentence. FedEx asserted that the last sentence of paragraph (g) of the 
proposed AD is ambiguous since SB 777-57A0050, Revision 6, does not 
specifically define what actions are ``corrective actions,'' and it has 
the potential to immediately ground aircraft. As an example, FedEx 
noted that for Work Package 23 of the Accomplishment Instructions of SB 
777-57A0050, Revision 6, requires installation of teflon sleeves in 
accordance with multiple figures without any prior inspection. Thus, 
Work Package 23 could be interpreted as a ``corrective action'' which 
is required prior to further flight. FedEx stated that the requirement 
in paragraph (g) of the proposed AD to ``do all applicable actions'' is 
sufficient since the associated service bulletin has specific actions 
to cap seal fasteners before putting the aircraft back to a serviceable 
condition.
    The FAA acknowledges that the last sentence in paragraph (g) of the 
proposed AD, ``Do all applicable corrective actions before further 
flight,'' is confusing as used in this AD. In certain ADs, the standard 
language, ``corrective actions,'' is defined in the preamble of the AD 
and those are typically ``on-condition'' actions required to be 
performed after the primary action (e.g., inspections). The ``before 
further flight'' compliance time is included to make sure that the 
corrective actions would be accomplished without any delay once the 
inspection is accomplished. The FAA has determined that this 
requirement is not necessary for this AD. The service information 
mandated by this AD requires an inspection for certain groups of 
airplanes to determine the installation configuration. Such an 
inspection is not required for certain other groups of airplanes since 
their installation configuration is already known. For all groups of 
airplanes, the FAA has determined that accomplishing all applicable 
actions within the compliance time would adequately address the safety 
concern. Therefore, the FAA has removed the sentence ``Do all 
applicable corrective actions before further flight'' from paragraph 
(g) of this AD. The ``applicable corrective actions'' are included in 
the ``all applicable actions (i.e., installation of Teflon sleeves, cap 
sealing of fasteners, detailed inspections, and corrective actions)'' 
language specified in paragraph (g) of this AD and therefore must be 
done within the applicable compliance time specified in Boeing Alert 
Service Bulletin 777-57A0050, Revision 6.

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.

[[Page 12555]]

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Service Bulletin 777-57A0050, 
Revision 6, dated August 18, 2021. This service information specifies 
applicable actions that vary depending on the airplane configuration, 
such as procedures for the installation of Teflon sleeves, cap sealing 
of fasteners, detailed inspections, and corrective actions. The 
detailed inspection of and installation of Teflon sleeves includes 
various locations, such as the rear spar wire bundles, inboard and 
outboard front spar wire bundles, wing-to-body fairing and 
environmental control system (ECS) bay wire bundles, front and rear 
spar bulkhead wire bundles, and wing rear spar wire bundles. The 
detailed inspection of and cap sealing of fasteners include fasteners 
in the center fuel tank, left and right main fuel tanks, and right 
cheek portion of the center fuel tank. Corrective actions include 
installing Teflon sleeve, installing clamp, and cap sealing fasteners.
    The FAA also reviewed Section 9, Airworthiness Limitations (AWLs) 
and Certification Maintenance Requirements (CMRs), D622W001-9, dated 
August 2022, of Boeing 777 200/200LR/300/300ER/777F Maintenance 
Planning Data (MPD) Document. This service information specifies, among 
other airworthiness limitations, 28-AWL-31 and 28-AWL-32 that address 
cushion clamps and Teflon sleeving installed on out-of-tank wire 
bundles installed on brackets that are mounted directly on the fuel 
tanks. 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 282 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
----------------------------------------------------------------------------------------------------------------
Installations, cap sealing, and   Up to 545 work-     Up to $3,510......  Up to $49,835.....  Up to $14,053,470.
 inspections.                      hours x $85 per
                                   hour = $46,325.
----------------------------------------------------------------------------------------------------------------
* Table does not include estimated costs for revising the existing maintenance or inspection program.

    The FAA has determined that revising the existing maintenance or 
inspection program takes an average of 90 work-hours per operator, 
although the agency recognizes that this number may vary from operator 
to operator. Since operators incorporate maintenance or inspection 
program changes for their affected fleet(s), the FAA has determined 
that a per-operator estimate is more accurate than a per-airplane 
estimate. Therefore, the FAA estimates the average total cost per 
operator to be $7,650 (90 work-hours x $85 per work-hour).
    The FAA estimates the following costs to do any necessary 
corrective actions that would be required based on the results of the 
inspections. The agency has no way of determining the number of 
aircraft that might need these actions:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
               Action                         Labor cost                Parts cost           Cost per product
----------------------------------------------------------------------------------------------------------------
Corrective actions.................  Up to 26 work-hours x $85    Up to $3,510..........  Up to $5,720.
                                      per hour = $2,210.
----------------------------------------------------------------------------------------------------------------

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 adding the following new airworthiness 
directive:

2023-03-04 The Boeing Company: Amendment 39-22329; Docket No.

[[Page 12556]]

FAA-2022-0810; Project Identifier AD-2021-01238-T.

(a) Effective Date

    This airworthiness directive (AD) is effective April 4, 2023.

(b) Affected ADs

    (1) This AD affects AD 2017-11-14, Amendment 39-18913 (82 FR 
25954, June 6, 2017) (AD 2017-11-14).
    (2) This AD also affects AD 2021-24-12, Amendment 39-21833 (86 
FR 73660, December 28, 2021) (AD 2021-24-12).

(c) Applicability

    This AD applies to all The Boeing Company Model 777-200, -200LR, 
-300, -300ER, and 777F series airplanes, certificated in any 
category.

(d) Subject

    Air Transport Association (ATA) of America Code 57, Wings.

(e) Unsafe Condition

    This AD was prompted by fuel system reviews conducted by the 
manufacturer. The FAA is issuing this AD to prevent arcing inside 
the main and center fuel tanks in the event of a fault current or 
lightning strike, which, in combination with flammable fuel vapors, 
could result in a fuel tank explosion and consequent loss of the 
airplane.

(f) Compliance

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

(g) Required Actions for Certain Airplanes

    For airplanes identified in Boeing Alert Service Bulletin 777-
57A0050, Revision 6, dated August 18, 2021: Except as specified in 
paragraph (h) of this AD, at the applicable times specified in 
paragraph 1.E., ``Compliance,'' of Boeing Alert Service Bulletin 
777-57A0050, Revision 6, dated August 18, 2021, do all applicable 
actions (i.e., installation of Teflon sleeves, cap sealing of 
fasteners, detailed inspections, and corrective actions) identified 
in, and in accordance with, the Accomplishment Instructions of 
Boeing Alert Service Bulletin 777-57A0050, Revision 6, dated August 
18, 2021.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Service Bulletin 777-57A0050, Revision 6, 
dated August 18, 2021, uses the phrase ``the revision 5 date of this 
service bulletin'' or ``the revision 6 date of this service 
bulletin,'' this AD requires using ``the effective date of this 
AD.''
    (2) Where circle symbol 1 of sheet 2 of Figures 172, 173, and 
174 of Boeing Alert Service Bulletin 777-57A0050, Revision 6, dated 
August 18, 2021, points to the outboard side of rib no. 9 for the 
locate and cap seal task or the inspection task, as applicable, in 
step 1 of sheet 3, for this AD, circle symbol 1 points to the seven 
fasteners located at the inboard side of rib no. 9 (adjacent to the 
right side of the identified seven fasteners).
    (3) Where circle symbol 1, next to the text ``7 locations,'' of 
sheet 2 of Figure 175 and Figure 176 of Boeing Alert Service 
Bulletin 777-57A0050, Revision 6, dated August 18, 2021, points to 
the outboard side of rib no. 9 for the locate and cap seal task or 
the inspection task, as applicable, in step 1 of sheet 3, for this 
AD, circle symbol 1, next to the text ``7 locations,'' points to the 
seven fasteners located at the inboard side of rib no. 9 (adjacent 
to the right side of the identified seven fasteners).
    (4) Where circle symbol 1, next to the text ``7 locations,'' of 
sheet 4 of Figure 179 and Figure 180 of Boeing Alert Service 
Bulletin 777-57A0050, Revision 6, dated August 18, 2021, points to 
the outboard side of rib no. 9 for the locate and cap seal task or 
the inspection task, as applicable, in step 1 of sheet 6, for this 
AD, circle symbol 1, next to the text ``7 locations,'' points to the 
seven fasteners located at the inboard side of rib no. 9 (adjacent 
to the left side of the identified seven fasteners).
    (5) Where Boeing Alert Service Bulletin 777-57A0050, Revision 6, 
dated August 18, 2021, specifies Work Package 28 is applicable to 
Group 1 through 4, and Group 8, this AD does not require 
accomplishment of Work Package 28 for Group 1 through 4 only.
    (6) For Group 1 through 4 airplanes identified in Boeing Alert 
Service Bulletin 777-57A0050, Revision 6, dated August 18, 2021, on 
which the actions specified in Work Package 37 of Boeing Alert 
Service Bulletin 777-57A0050, Revision 6, dated August 18, 2021, 
have been accomplished, the actions specified in Work Package 38 are 
not required.
    (7) Where the Accomplishment Instructions of Boeing Alert 
Service Bulletin 777-57A0050, Revision 6, dated August 18, 2021, 
specifies to purge specific fuel tanks (right, left, or center), 
operators must purge the applicable fuel tank for which access 
inside the fuel tank is needed to apply cap sealing to the affected 
fasteners.

(i) Maintenance or Inspection Program Revision

    Within 60 days after the effective date of this AD, revise the 
existing maintenance or inspection program, as applicable, to 
incorporate the information for 28-AWL-31 and 28-AWL-32 specified in 
Section D, ``Airworthiness Limitations-Systems,'' including 
Subsections D.1, of Section 9, Airworthiness Limitations (AWLs) and 
Certification Maintenance Requirements (CMRs), D622W001-9, dated 
August 2022, of Boeing 777-200/200LR/300/300ER/777F Maintenance 
Planning Data (MPD) Document. The initial compliance time for doing 
airworthiness limitation instructions (ALI) task 28-AWL-32 is at the 
applicable time specified in paragraph (i)(1) or (2) of this AD:
    (1) For airplanes having line number (L/Ns) 1 through 503 
inclusive: Within 3,750 days after accomplishment of the actions 
specified in Boeing Service Bulletin 777-57A0050; within 60 months 
after the effective date of this AD; or within 3,750 days after the 
most recent inspection was performed as specified in AWL No. 28-AWL-
32; whichever is latest.
    (2) For airplanes having L/Ns 504 and subsequent: Within 3,750 
days after the date of issuance of the original airworthiness 
certificate or the date of issuance of the original export 
certificate of airworthiness; within 60 months after the effective 
date of this AD; or within 3,750 days after the most recent 
inspection was performed as specified in AWL No. 28-AWL-32; 
whichever is latest.

(j) Credit for Previous Actions

    This paragraph provides credit for the maintenance or inspection 
program revision specified in paragraph (i) of this AD, if the 
revision was performed before the effective date of this AD using 
Section 9, Airworthiness Limitations (AWLs) and Certification 
Maintenance Requirements (CMRs), D622W001-9, dated March 2022, dated 
June 2022, or dated July 2022, of Boeing 777 200/200LR/300/300ER/
777F Maintenance Planning Data (MPD) Document; provided that the 
corrections specified in paragraphs (j)(1) through (4) of this AD 
were also incorporated. The following exceptions apply to 28-AWL-31 
and 28-AWL-32 of Section D, ``Airworthiness Limitations--Systems,'' 
including Subsections D.1 of Section 9, Airworthiness Limitations 
(AWLs) and Certification Maintenance Requirements (CMRs), D622W001-
9, of Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data 
(MPD) Document.
    (1) In paragraph 1.i., change ``Front Spar Bulkhead (Center 
Tank)'' to ``Front Spar Bulkhead (Center Wing Tank Fuel Quantity 
Greater than 12,400 Gallons).''
    (2) In paragraph 1.i.II, change ``For 777-200, 777-200LR, 777-
300, and 777-300ER airplanes, L/N 562 and on'' to ``L/N 562 and on, 
except 777F.''
    (3) In paragraph 1.i.III., change ``For 777F airplanes, L/N 718 
and on'' to ``For 777F airplanes.''
    (4) In paragraph 1.j., change ``Rear Spar Bulkhead (Center 
Tank)'' to ``Rear Spar Bulkhead (Center Wing Tank Fuel Quantity 
Greater than 12,400 Gallons).''

(k) No Alternative Actions, Intervals, or Critical Design Configuration 
Control Limitations (CDCCLs)

    After the existing maintenance or inspection program has been 
revised as required by paragraph (i) of this AD, no alternative 
actions (e.g., inspections), intervals, or CDCCLs may be used unless 
the actions, intervals, and CDCCLs are approved as an alternative 
method of compliance (AMOC) in accordance with the procedures 
specified in paragraph (m) of this AD.

(l) Terminating Action for Certain Requirements of AD 2017-11-14 and AD 
2021-24-12

    (1) Accomplishment of the actions required by paragraph (g) of 
this AD terminates the requirements of paragraphs (g)(1), (i), and 
(j) of AD 2017-11-14.
    (2) Accomplishment of the revision required by paragraph (i) of 
this AD terminates the requirements of paragraphs (g)(6) and (h) of 
AD 2021-24-12.

(m) 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

[[Page 12557]]

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 (n) 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.

(n) Related Information

    For more information about this AD, contact Kevin Nguyen, 
Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3555; email: [email protected].

(o) 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 Service Bulletin 777-57A0050, Revision 6, dated 
August 18, 2021.
    (ii) Section 9, Airworthiness Limitations (AWLs) and 
Certification Maintenance Requirements (CMRs), D622W001-9, dated 
August 2022, of Boeing 777 200/200LR/300/300ER/777F Maintenance 
Planning Data (MPD) Document.
    (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; website myboeingfleet.com.
    (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 protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on February 2, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-04024 Filed 2-27-23; 8:45 am]
BILLING CODE 4910-13-P


