[Federal Register Volume 86, Number 133 (Thursday, July 15, 2021)]
[Rules and Regulations]
[Pages 37221-37224]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15029]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0981; Project Identifier AD-2020-00919-T; 
Amendment 39-21615; AD 2021-13-10]
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 
certain The Boeing Company Model 777 airplanes. This AD was prompted by 
reports indicating that during investigation of a fuel leak, fatigue 
cracking was found on the forward inboard side of the fuel tank access 
door cutouts on the left and right lower wing skin. The cause of the 
cracking is attributed to corrosion damage. This AD requires repetitive 
inspections for any existing repair of the wing lower skin fuel tank 
and dry bay access door cutouts on the left and right lower wing skin, 
and applicable on-condition actions. The FAA is issuing this AD to 
address the unsafe condition on these products.

DATES: This AD is effective August 19, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of August 19, 
2021.

ADDRESSES: 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 https://www.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 
https://www.regulations.gov by searching for and locating Docket No. 
FAA-2020-0981.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0981; 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.

FOR FURTHER INFORMATION CONTACT: Luis A. Cortez-Muniz, Aerospace 
Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th 
St., Des Moines, WA 98198; phone and fax: 206-231-3958; 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 certain The Boeing 
Company Model 777 airplanes. The NPRM published in the Federal Register 
on November 18, 2020 (85 FR 73430). The NPRM was prompted by reports 
indicating that during investigation of a fuel leak, fatigue cracking 
was found on the forward inboard side of the fuel tank access door 
cutouts on the left and right lower wing skin. The cause of the 
cracking is attributed to corrosion damage. In the NPRM, the FAA 
proposed to require repetitive inspections for any existing repair of 
the wing lower skin fuel tank and dry bay access door cutouts on the 
left and right lower wing skin, and applicable on-condition actions. 
The FAA is issuing this AD to address fatigue cracking, which could 
result in the inability of a principal structural element to sustain 
limit load, and consequent reduced structural integrity of the 
airplane.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from Boeing and United Airlines. Those 
commenters supported the NPRM without change.
    The FAA received additional comments from six commenters, including 
AeroLogic, Air France, American Airlines, Emirates, FedEx Express 
(FedEx), and one individual. The following presents the comments 
received on the NPRM and the FAA's response to each comment.

Request To Revise Compliance Time

    AeroLogic, Air France, American Airlines, and Emirates asked that 
the FAA re-evaluate and extend the initial and repetitive calendar-
based compliance times in the proposed AD to match heavy maintenance 
intervals. The commenters stated that the 1,125-day compliance time 
does not align with existing MPD intervals of 3,000 days and 4,500 days 
or the existing heavy maintenance intervals. One commenter stated that, 
as a long-range freight specialist it has an average flight hour/flight 
cycle ratio of 6.0 to 6.3, thus reaching the flight hour LOV of the 
Model 777F before reaching the flight cycle utilization that the 
aircraft with crack findings had at the time of crack detection. The 
commenters also stated that more frequent opening and closing of the 
access doors could increase the chance of corrosion. although the 
airplane with the initial crack finding was 19 years old at the time 
cracking was found, and Boeing reported that only minimal corrosion was 
found during lab testing of the cracking.
    The FAA does not agree with the requests to extend the compliance 
time. The compliance times were coordinated with the design approval 
holder based on its analysis and fleet findings. Additionally, the 
commenters did not provide substantiation data that shows that the 
proposed extended inspection intervals provide adequate crack 
detection. However, under the provisions of paragraph (i) of this AD, 
the FAA will consider requests for approval of an extension of the 
compliance time if sufficient data are submitted to substantiate that 
the extension would provide an acceptable level of safety. This AD has 
not been changed in this regard.

Request To Change Exception

    Air France stated that paragraph (h)(1) of the proposed AD would 
require using ``the effective date of this AD,'' except where Boeing 
Alert Requirements Bulletin 777-57A0118 RB, dated June 23, 2020, uses 
the phrase ``the original issue date of Requirements Bulletin 777-
57A0118 RB'' in a note or flag note. Air France noted that making the 
exception depend on a note or flag note is confusing. Air France asked 
that the FAA change the exception to apply throughout the proposed AD 
requirements instead of depending on

[[Page 37222]]

where the phrase ``the original issue date of Requirements Bulletin 
777-57A0118 RB'' is used.
    The FAA agrees to change the exception in paragraph (h)(1) of this 
AD. The exception specified in paragraph (h)(1) of the proposed AD was 
intended to apply only to certain dates referenced in Boeing Alert 
Requirements Bulletin 777-57A0118 RB, dated June 23, 2020. The 
exception applies to the associated date in the Effectivity paragraph 
and the Condition and Compliance columns of tables 1 through 10 of 
paragraph 1.E., ``Compliance,'' and not to flag note (c) in the tables. 
Repairs accomplished relative to the original issue date of 
Requirements Bulletin 777-57A0118 RB, as specified in flag note (c) in 
those tables, do not need an exception for compliance with this AD. The 
FAA has changed paragraph (h)(1) of this AD accordingly.

Request To Change Estimated Work Hours for Inspection

    FedEx stated that the hours estimated for ``the inspection'' in the 
Costs of Compliance section of the NPRM is lower than its forecast of 
80 work-hours and 60 elapsed hours. FedEx noted that the NPRM specified 
only 34 work-hours.
    The FAA infers that the commenter is asking to increase the work 
hours for the general visual inspections specified in the Costs of 
Compliance section of this AD to 80 work-hours. We do not agree. The 
estimate of 34 work-hours includes access and close for accomplishing 
the general visual inspections. The FAA recognizes that additional on-
condition inspections could be required, depending on the results of 
the general visual inspection. However, since the FAA has no way of 
determining the number of aircraft that might need these on-condition 
inspections, the hours and cost estimates for the additional 
inspections are provided in the on-condition actions table on a per-
airplane basis. This AD has not been changed in this regard.

Request To Allow Detailed Inspections for Certain Airplanes

    One individual asked that the FAA allow detailed and high frequency 
eddy current (HFEC) inspections for airplanes in Group 3, Condition 17 
(for the right wing), similar to the detailed and HFEC inspections 
allowed for airplanes in Group 3, Condition 14 (for the left wing). The 
commenter observed that Condition 14 specifies detailed and HFEC 
inspections, whereas Condition 17 specifies contacting Boeing. The 
commenter stated that these conditions are the same and symmetrical for 
the left- and right-hand wings.
    The FAA does not agree with the commenter's request. Configurations 
on Group 3 airplanes may be different on the left and right sides due 
to previously approved repairs or production changes. The inspection 
procedures were coordinated with the design approval holder regarding 
the airplane configurations. Therefore, this AD has not been changed in 
this regard.

Request To Clarify Cost Estimate

    AeroLogic stated that the proposed compliance time would result in 
an economic impact that was not considered in the operator burden 
provided in the cost estimate.
    The FAA provides the following clarification: The cost information 
describes only the direct costs of the specific actions required by 
this AD. Based on the best data available, the manufacturer provided 
the number of work hours necessary to do the required actions. This 
number represents the time necessary to perform only the actions 
actually required by this AD. We recognize that, in doing the actions 
required by an AD, operators might incur incidental costs in addition 
to the direct costs. The cost analysis in AD rulemaking actions, 
however, typically does not include incidental costs such as the time 
necessary for planning or time necessitated by other administrative 
actions. Those incidental costs, which might vary significantly among 
operators, are almost impossible to calculate.
    Aerologic also stated that the aircraft maintenance manual (AMM) 
recommends using new gaskets to prevent fuel leaks after each tank 
access. Therefore, the parts cost should be estimated with up to 240 
USD per gasket. At 18 Access Doors opened for every repeat inspection, 
this sums up to 4,320 USD per aircraft for each inspection cycle.
    The FAA does not agree to change the estimated parts costs, as the 
actions in the AMM are not required by this AD.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Except for minor editorial changes, 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 777-57A0118 RB, 
dated June 23, 2020. The service information describes procedures for 
repetitive general visual inspections for any existing repair of the 
fuel tank access door cutouts on the left and right lower wing skin, 
and applicable on-condition actions. On-condition actions include 
detailed and HFEC inspections for any corrosion, fretting, and 
cracking; a blend out of corrosion or fretting that meets certain 
criteria; and repair. 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 221 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                      Estimated Costs for Required Actions
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                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
General visual inspection........  Up to 34 work-hours              $0  Up to $2,890 per     Up to $638,690 per
                                    x $85 per hour =                     inspection cycle.    inspection cycle.
                                    Up to $2,890 per
                                    inspection cycle.
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    The FAA estimates the following costs to do any necessary on-
condition actions that would be required. The FAA has no way of 
determining the number of aircraft that might need these on-condition 
actions:

[[Page 37223]]



                                    Estimated Costs of On-Condition Actions *
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                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Blend out of corrosion or          2 work-hours x $85               $0  $170 per blend out.  $170 per blend out.
 fretting.                          per hour = $170
                                    per blend out.
Repair of crack 0.2 inch or less   2 work-hours x $85                0  $170 per crack.....  $170 per crack.
 with no blend repair or keyway     per hour = $170
 trim modification.                 per crack.
Detailed and HFEC inspections....  2 work-hours x $85                0  $170 per access      $170 per access
                                    per hour = $170                      door cutout.         door cutout.
                                    per access door
                                    cutout.
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* The FAA has received no definitive data on which to base the cost estimates for the on-condition repairs
  specified in this AD that require obtaining an alternative method of compliance (AMOC).

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:

2021-13-10 The Boeing Company: Amendment 39-21615; Docket No. FAA-
2020-0981; Project Identifier AD-2020-00919-T.

(a) Effective Date

    This airworthiness directive (AD) is effective August 19, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 777-200, -200LR, -
300, -300ER, and 777F series airplanes, certificated in any 
category, as identified in Boeing Alert Requirements Bulletin 777-
57A0118 RB, dated June 23, 2020.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by reports indicating that during 
investigation of a fuel leak, fatigue cracking was found on the 
forward inboard side of the fuel tank access door cutouts on the 
left and right lower wing skin. The cause of the cracking is 
attributed to corrosion damage. The FAA is issuing this AD to 
address such cracking, which could result in the inability of a 
principal structural element to sustain limit load, and consequent 
reduced structural integrity of the airplane.

(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 777-57A0118 RB, dated June 23, 2020, do 
all applicable actions identified in, and in accordance with, the 
Accomplishment Instructions of Boeing Alert Requirements Bulletin 
777-57A0118 RB, dated June 23, 2020.
    Note 1 to paragraph (g): Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
777-57A0118, dated June 23, 2020, which is referred to in Boeing 
Alert Requirements Bulletin 777-57A0118 RB, dated June 23, 2020.

(h) Exceptions to Service Information Specifications

    (1) Where the ``Effectivity'' paragraph, and the Condition and 
Compliance Time columns of the tables in the ``Compliance'' 
paragraph, of Boeing Alert Requirements Bulletin 777-57A0118 RB, 
dated June 23, 2020, use the phrase ``the original issue date of 
Requirements Bulletin 777-57A0118 RB,'' this AD requires using ``the 
effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 777-57A0118 RB, 
dated June 23, 2020, specifies contacting Boeing for repair 
instructions or for alternative inspections: This AD requires doing 
the repair, or doing the alternative inspections and applicable on-
condition actions using a method approved in accordance with the 
procedures specified in paragraph (i) of this AD.

(i) 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 (j)(1) 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,

[[Page 37224]]

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.

(j) Related Information

    For more information about this AD, contact Luis A. Cortez-
Muniz, Aerospace Engineer, Airframe Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 
206-231-3958; email: [email protected].

(k) 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 777-57A0118 RB, dated 
June 23, 2020.
    (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 https://www.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 [email protected], or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on June 10, 2021.
Ross Landes,
Deputy Director for Regulatory Operations, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-15029 Filed 7-14-21; 8:45 am]
BILLING CODE 4910-13-P