[Federal Register Volume 86, Number 34 (Tuesday, February 23, 2021)]
[Rules and Regulations]
[Pages 10776-10780]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-03572]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0705; Product Identifier 2019-NM-098-AD; Amendment 
39-21396; AD 2021-02-13]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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[[Page 10777]]

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-600, -700, -700C, -800, and -900 
series airplanes. This AD was prompted by reports of cracks in the bear 
strap from station (STA) 290 to STA 296, and between stringers S-8R and 
S-9R, sometimes common to fasteners in the gap cover and emanating from 
rough sanding marks found on the surface of the bear strap. This AD 
requires inspections of the fuselage skin and bear strap at the forward 
galley door between certain stations for cracks, and applicable on-
condition actions. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective March 30, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of March 30, 
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; phone: 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 on 
the internet at https://www.regulations.gov by searching for and 
locating Docket No. FAA-2019-0705.

Examining the AD Docket

    You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2019-
0705; 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: Michael Bumbaugh, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3522; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Discussion

    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 737-600, -700, -700C, -800, and -900 series airplanes. 
The NPRM published in the Federal Register on October 1, 2019 (84 FR 
52047). The NPRM was prompted by reports of cracks in the bear strap 
between certain stations, sometimes common to fasteners in the gap 
cover and emanating from rough sanding marks found on the surface of 
the bear strap. The NPRM proposed to require inspections of the 
fuselage skin and bear strap at the forward galley door between certain 
stations for cracks, and applicable on-condition actions.
    The FAA issued a supplemental NPRM (SNPRM) to amend 14 CFR part 39 
by adding an AD that would apply to certain The Boeing Company Model 
737-600, -700, -700C, -800, and -900 series airplanes. The SNPRM 
published in the Federal Register on May 1, 2020 (85 FR 25348). The FAA 
issued the SNPRM to revise certain inspections to provide the correct 
thickness callouts for the fuselage skin and bear strap.
    The FAA is issuing this AD to address cracking of the bear strap, 
which could result in severing of the bear strap, possibly leading to 
uncontrolled decompression and loss of structural integrity of the 
airplane.

Comments

    The FAA gave the public the opportunity to participate in 
developing this final rule. The following presents the comments 
received on the SNPRM and the FAA's response to each comment.

Support for the SNPRM

    United Airlines stated that it has no technical objection to the 
SNPRM and that it concurs with the proposed rulemaking.

Request for an Alternative Method of Compliance for a Certain Repair

    Southwest Airlines (SWA) requested that the Boeing 737-700/-800 
Structural Repair Manual (SRM) 53-10-01, Repair 6, be approved as an 
alternative method of compliance (AMOC) to certain corrective actions 
specified in Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020. SWA contended that this repair 
covers the affected inspection zone, and that this SRM repair should be 
a terminating action to the inspections specified in Boeing Alert 
Requirements Bulletin 737-53A1383 RB, Revision 1, dated February 19, 
2020, because the entire inspection area covered is common to the 
repair given in Boeing 737-700/-800 SRM 53-10-01, Repair 6. SWA 
asserted that operators should be able to accomplish this SRM repair 
without contacting Boeing, provided there are no deviations and that 
the findings meet the criteria listed in the Boeing 737-700/-800 SRM 
53-10-01, Repair 6. SWA also noted that the SRM was published after 
Boeing Alert Requirements Bulletin 737-53A1383 RB, Revision 1, dated 
February 19, 2020, so there was no way to reference the SRM repair 
within it.
    The FAA disagrees with the request because the referenced SRM 
repair has not yet been approved for the specified conditions. However, 
under the provisions of paragraph (j) of this AD, the FAA will consider 
requests for approval of an AMOC if a proposal is submitted that is 
supported by technical data indicating that the proposed repair will 
provide an acceptable level of safety. If the referenced SRM repair is 
determined to be acceptable to address the specified conditions, the 
FAA may approve, and Boeing may issue, a global AMOC for the SRM 
repair. The FAA has not changed this AD as a result of this comment.

Request for an Altered Compliance Time for Condition 1, Action 1, of 
the Service Information

    Southwest Airlines requested that where table 1 of paragraph 1.E., 
``Compliance,'' of Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020, states a compliance time of 
``Before further flight'' for certain on-condition actions, the 
proposed AD should specify this compliance time as ``Before 15,000 
total flight cycles or within 6,000 flight cycles after the original 
issue of the AD, whichever occurs later.'' Southwest Airlines also 
requested that the FAA clarify the requirement of Condition 1, Action 
1, and Condition 3 and Condition 4.1.1, within Boeing Alert 
Requirements Bulletin 737-53A1383 RB, Revision 1, dated February 19, 
2020, paragraph 1.E., ``Compliance,'' in Tables 1 and 2, to do the 
alternative inspections and applicable on-condition action(s) before 
further flight. SWA asserted that there is an equivalent level of 
safety between an airplane without a repair reaching the compliance 
time threshold to perform the Boeing service bulletin inspection and an 
airplane with a repair reaching the compliance time threshold before an 
action is required. Therefore, the compliance times for obtaining the 
alternative inspection(s) for the existing repairs should align with 
the compliance times allowed for

[[Page 10778]]

the initial service bulletin general visual inspection in lieu of 
``before further flight.'' SWA proposed that this allowance be listed 
within paragraph (h) of the proposed AD, similar to the allowance 
provided by paragraph (i) of the proposed AD.
    The FAA agrees that allowing the AD compliance time for an airplane 
with an existing repair to be the same as an aircraft without an 
existing repair will provide an acceptable level of safety. Any 
alternative inspection program including compliance times must be done 
in accordance with an approved AMOC. The FAA has added paragraph (h)(3) 
of this AD to address this change.

Request To Clarify Authority for Approval of Alternative Inspection 
Programs

    Southwest Airlines requested that the FAA clarify who has the 
authority to approve an alternative inspection program for any repair 
found during Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020, paragraph 1.E, ``Compliance,'' 
Table 1, Condition 1, Action 1. Paragraph (j)(1) of the proposed AD 
clearly indicated that the manager of the Seattle ACO Branch has that 
authority; paragraph (j)(3) of the proposed AD provided the path to 
obtain an AMOC by The Boeing Company Organization Designation 
Authorization (ODA) as delegated only for a repair, modification, and 
alteration. SWA requested clarification whether paragraph (j)(3) of the 
proposed AD encompasses both existing repairs and repairs installed as 
a result of inspection findings. SWA asserted that it is unclear 
whether the reference to the repair is for an existing repair that is 
located in the inspection area or for a repair that is installed as a 
result of any crack finding.
    The FAA agrees to clarify. The Boeing Company ODA has authority to 
approve AMOCs as authorized and delegated for repairs installed prior 
to the AD and repairs due to a crack finding, as well as repairs not 
due to a crack finding. An operator would need to provide The Boeing 
Company ODA with all details and geometry needed to design and analyze 
the repair data.

Request To Clarify the Use of ``Covers'' in the Service Information

    SWA commented that Boeing Alert Requirements Bulletin 737-53A1383 
RB, Revision 1, dated February 19, 2020, paragraph 1.E., 
``Compliance,'' Table 1, note (b), omits the inspection in areas where 
a repair covers the affected zone, provided conditions 1 and 2 are met. 
A similar note is included in paragraph 1.E., ``Compliance,'' Table 2, 
note (c). SWA would like clarification of the word ``covers'' as it 
relates to repairs in the area. Since the configuration has changed 
because of the repair, SWA stated that the repair's damage tolerance 
program provides an equivalent level of safety for this area.
    The FAA has coordinated with Boeing to clarify the intent of the 
wording in this section. Note (b) in Table 1 and note (c) in Table 2 of 
Boeing Alert Requirements Bulletin 737-53A1383 RB, Revision 1, dated 
February 19, 2020, paragraph 1.E., ``Compliance,'' apply to the area 
``covered by'' a repair, but not for the area ``common to'' a repair. A 
repair that is ``common to'' the area, meaning physically in the same 
area as the NPRM-proposed repair, but that was not meant to address the 
issue specified in the NPRM (i.e., ``covered'' areas), could 
potentially be obscuring the inspections that would detect crack growth 
which this AD is meant to mitigate. Therefore, if a repair was not done 
as a corrective action for a crack in the bear strap, and the operator 
does not perform the inspections specified in the Boeing Alert 
Requirements Bulletin 737-53A1383 RB, Revision 1, dated February 19, 
2020, it may result in the unsafe condition. The FAA has not changed 
this AD as a result of this comment.

Request To Include Inspection Programs

    SWA commented that paragraph (j)(3) of the proposed AD (in the 
SNPRM) stated that an AMOC may be used for any required repair, 
modification, or alteration if approved by The Boeing Company ODA. SWA 
stated that inspection programs should be included in this list of 
conditions for which The Boeing Company ODA can provide an AMOC, as 
paragraph (h)(2) explicitly states it is acceptable to accomplish 
alternative inspections approved in accordance with the procedures 
specified in paragraph (j) of the proposed AD.
    The FAA agrees with the assertion that the inspection program may 
be part of the AMOC because the inspection program for the repaired 
area may be part of the repair, which in turn is part of the AMOC. 
However, the FAA disagrees with changing this AD because an AMOC issued 
for a repair will include the inspection program. The request to add 
certain inspection programs to The Boeing Company ODA-authorized list 
of AMOC approvals is outside the scope of this rulemaking. Therefore, 
the FAA has not changed this AD in this regard.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety and the public interest 
require adopting this final rule with the change described previously 
and minor editorial changes. The FAA has determined that these minor 
changes:
     Are consistent with the intent that was proposed in the 
SNPRM for addressing the unsafe condition; and
     Do not add any additional burden upon the public than was 
already proposed in the SNPRM.
    The FAA also determined that these changes will not increase the 
economic burden on any operator or increase the scope of this final 
rule.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020. This service information describes 
procedures for inspecting for cracks of the fuselage skin and bear 
strap at the forward galley door between certain stations, through the 
use of two alternative inspection methods for the initial inspections: 
(1) Internal and external general visual inspections and internal 
surface high frequency eddy current (HFEC) inspections, and (2) 
external general visual and external eddy current inspections. This 
service information also describes procedures for applicable on-
condition actions including inspections for cracks, HFEC inspections 
for cracks, low frequency eddy current (LFEC) inspections for cracks, 
and repair, depending on the inspection method selected. 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 the ADDRESSES section.

Costs of Compliance

    The FAA estimates that this AD affects 752 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

[[Page 10779]]



                                 Estimated Costs for Required Actions: Option 1
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                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Internal general visual            11 work-hours x $85              $0  $935...............  $703,120.
 inspection.                        per hour = $935.
External general visual            1 work-hour x $85                 0  85.................  63,920.
 inspection.                        per hour = $85.
Internal Surface HFEC inspections  3 work-hours x $85                0  255 per inspection   191,760 per
                                    per hour = $255                      cycle.               inspection cycle.
                                    per inspection
                                    cycle.
----------------------------------------------------------------------------------------------------------------


                                 Estimated Costs for Required Actions: Option 2
----------------------------------------------------------------------------------------------------------------
                                                                                                 Cost on U.S.
              Action                    Labor cost        Parts cost      Cost per product        operators
----------------------------------------------------------------------------------------------------------------
External general visual            1 work-hour x $85                $0  $85................  $63,920.
 inspection.                        per hour = $85.
External LFEC and HFEC             18 work-hours x $85               0  1,530 per            1,150,560 per
 inspections.                       per hour = $1,530                    inspection cycle.    inspection cycle.
                                    per inspection
                                    cycle.
----------------------------------------------------------------------------------------------------------------

    The FAA has received no definitive data that would enable the 
agency to provide cost estimates for the on-condition actions specified 
in this AD.

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.

Adoption of 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:

2021-02-13 The Boeing Company: Amendment 39-21396; Docket No. FAA-
2019-0705; Product Identifier 2019-NM-098-AD.

(a) Effective Date

    This airworthiness directive (AD) is effective March 30, 2021.

(b) Affected ADs

    None.

(c) Applicability

    (1) This AD applies to The Boeing Company Model 737-600, -700, -
700C, -800, and -900 series airplanes, certificated in any category, 
as identified in Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020.
    (2) Installation of Supplemental Type Certificate (STC) 
ST00830SE does not affect the ability to accomplish the actions 
required by this AD. Therefore, for airplanes on which STC ST00830SE 
is installed, a ``change in product'' alternative method of 
compliance (AMOC) approval request is not necessary to comply with 
the requirements of 14 CFR 39.17.

(d) Subject

    Air Transport Association (ATA) of America Code 53, Fuselage.

(e) Unsafe Condition

    This AD was prompted by reports of cracks in the bear strap from 
station (STA) 290 to STA 296, and between stringers S-8R and S-9R, 
sometimes common to fasteners in the gap cover and emanating from 
rough sanding marks found on the surface of the bear strap. The FAA 
is issuing this AD to address cracking of the bear strap, which 
could result in severing of the bear strap, possibly leading to 
uncontrolled decompression and loss of 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 737-53A1383 RB, Revision 1, dated 
February 19, 2020, do all applicable actions identified in, and in 
accordance with, the Accomplishment Instructions of Boeing Alert 
Requirements Bulletin 737-53A1383 RB, Revision 1, dated February 19, 
2020.

    Note 1 to paragraph (g):  Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-53A1383, Revision 1, dated February 19, 2020, which is referred 
to in Boeing Alert Requirements Bulletin 737-53A1383 RB, Revision 1, 
dated February 19, 2020.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020, uses the phrase ``the original 
issue date of Requirements Bulletin 737-53A1383 RB,'' this AD 
requires using ``the effective date of this AD,'' except where 
Boeing Alert Requirements Bulletin 737-53A1383 RB, Revision 1, dated 
February 19,

[[Page 10780]]

2020, uses the phrase ``the original issue date of Requirements 
Bulletin 737-53A1383 RB'' in a note or flag note.
    (2) Where Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 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 and compliance time 
approved in accordance with the procedures specified in paragraph 
(j) of this AD.
    (3) Where Boeing Alert Requirements Bulletin 737-53A13833 RB, 
Revision 1, dated February 19, 2020, in Tables 1 and 2, Condition 1 
(Action 1), Condition 3, and Condition 4.1.1 (Action 1), specifies a 
compliance time of ``before further flight'': This AD requires 
compliance before 15,000 total flight cycles or within 6,000 flight 
cycles after the effective date of this AD, whichever occurs later.

(i) 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 Boeing Alert Requirements Bulletin 
737-53A1383 RB, dated May 9, 2019, except for airplanes on which 
Option 2, Condition 4, has been done. For airplanes on which Option 
2, Condition 4, has been done, credit is given for Boeing Alert 
Requirements Bulletin 737-53A1383 RB, dated May 9, 2019, provided 
operators do the external low frequency eddy current (LFEC) 
inspection of the forward galley door bear strap and external high 
frequency eddy current (HFEC) inspection of the fuselage skin for 
any crack in accordance with Figure 4 of the Accomplishment 
Instructions of Boeing Alert Requirements Bulletin 737-53A1383 RB, 
Revision 1, dated February 19, 2020. The compliance time for 
accomplishing these actions is at the later of the times specified 
in paragraphs (i)(1) and (2) of this AD. Except as specified in 
paragraph (h)(3), do all applicable on-condition actions identified 
in, and in accordance with, the Accomplishment Instructions of 
Boeing Alert Requirements Bulletin 737-53A1383 RB, Revision 1, dated 
February 19, 2020, at the applicable times specified in the 
``Compliance'' paragraph of Boeing Alert Requirements Bulletin 737-
53A1383 RB, Revision 1, dated February 19, 2020.
    (1) Before 15,000 total flight cycles.
    (2) Within 6,000 flight cycles after the effective date of this 
AD.

(j) 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 local Flight Standards District 
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 (k)(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 local flight standards district office/certificate holding 
district 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, 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.

(k) Related Information

    (1) For more information about this AD, contact Michael 
Bumbaugh, Aerospace Engineer, Airframe Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 
206-231-3522; email: [email protected].
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (l)(3) and (4) of this AD.

(l) 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 737-53A1383 RB, Revision 
1, dated February 19, 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; phone: 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 January 14, 2021.
Gaetano A. Sciortino,
Deputy Director for Strategic Initiatives, Compliance & Airworthiness 
Division, Aircraft Certification Service.
[FR Doc. 2021-03572 Filed 2-22-21; 8:45 am]
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