[Federal Register Volume 86, Number 35 (Wednesday, February 24, 2021)]
[Proposed Rules]
[Pages 11186-11189]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-03577]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0026; Project Identifier AD-2020-01164-T]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for all The Boeing Company Model 737-100, -200, -200C, -300, -400, and 
-500 series airplanes. This proposed AD was prompted by a report 
indicating that a crack was found on the splice angle flange that is 
attached to the station (STA) 540 bulkhead in the area between certain 
stringers. This proposed AD would require repetitive surface high 
frequency eddy current (HFEC) inspections at the radius of the left- 
and right side of the STA 540 bulkhead splice angle for any cracking 
and applicable on-condition actions. The FAA is proposing this AD to 
address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by April 12, 
2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: 202-493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For service information identified in this NPRM, 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 referenced service information at the FAA, Airworthiness 
Products Section, Operational Safety Branch, 2200 South 216th St., Des 
Moines, WA. For information on the availability of this material at the 
FAA, call 206-231-3195. It is also available on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2021-
0026.

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-2021-
0026; 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 NPRM, any comments received, and other information. The street 
address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: George Garrido, Aerospace Engineer, 
Airframe Section, FAA, Los Angeles ACO Branch, 3960 Paramount 
Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5232; fax: 562-627-
5210; email: [email protected].

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send

[[Page 11187]]

your comments to an address listed under ADDRESSES. Include ``Docket 
No. FAA-2021-0026; Project Identifier AD-2020-01164-T'' at the 
beginning of your comments. The most helpful comments reference a 
specific portion of the proposal, explain the reason for any 
recommended change, and include supporting data. The FAA will consider 
all comments received by the closing date and may amend the proposal 
because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
https://www.regulations.gov, including any personal information you 
provide. The agency will also post a report summarizing each 
substantive verbal contact received about this proposed AD.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to 
George Garrido, Aerospace Engineer, Airframe Section, FAA, Los Angeles 
ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 
562-627-5232; fax: 562-627-5210; email: [email protected]. Any 
commentary that the FAA receives which is not specifically designated 
as CBI will be placed in the public docket for this rulemaking.

Discussion

    The FAA has received a report from Boeing indicating that a crack 
was found on the splice angle flange that is attached to the STA 540 
bulkhead in the area between stringer 21 to stringer 22. The crack was 
found during the accomplishment of Supplemental Structural Inspection 
Document (SSID) F-25A on a Model 737-300 airplane. The airplane had 
accumulated 80,634 flight hours and 62,768 flight cycles at the time of 
the crack finding. This condition, if not addressed, could result in 
the inability of a principal structural element to sustain limit load 
and could adversely affect the structural integrity of the airplane; in 
addition, such cracking could lead to adjoining parts cracking and a 
potential fuel leak and consequent fire.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Requirements Bulletin 737-57A1347 RB, 
dated July 29, 2020. The service information describes procedures for 
repetitive surface HFEC inspections at the radius of the left- and 
right side of the STA 540 bulkhead splice angle for any cracking and 
applicable on-condition actions. On-condition actions include repair or 
replacement.
    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.

Explanation of Applicability

    Model 737 airplanes having line numbers 1 through 291 have a limit 
of validity (LOV) of 34,000 total flight cycles, and the actions 
proposed in this NPRM, as specified in Boeing Alert Requirements 
Bulletin 737-57A1347 RB, dated July 29, 2020, would be required at a 
compliance time occurring after that LOV. Although operation of an 
airplane beyond its LOV is prohibited by 14 CFR 121.1115 and 129.115, 
this NPRM would include those airplanes in the applicability so that 
these airplanes are tracked in the event the LOV is extended in the 
future.

FAA's Determination

    The FAA is proposing this AD because the agency evaluated all the 
relevant information and determined the unsafe condition described 
previously is likely to exist or develop in other products of the same 
type design.

Proposed AD Requirements

    This proposed AD would require accomplishment of the actions 
identified in Boeing Alert Requirements Bulletin 737-57A1347 RB, dated 
July 29, 2020, described previously, except for any differences 
identified as exceptions in the regulatory text of this proposed AD.
    For information on the procedures and compliance times, see this 
service information at https://www.regulations.gov by searching for and 
locating Docket No. FAA-2021-0026.

Explanation of Requirements Bulletin

    The FAA worked in conjunction with industry, under the 
Airworthiness Directive Implementation Aviation Rulemaking Committee 
(AD ARC), to enhance the AD system. One enhancement is a process for 
annotating which steps in the service information are ``required for 
compliance'' (RC) with an AD. Boeing has implemented this RC concept 
into Boeing service bulletins.
    In an effort to further improve the quality of ADs and AD-related 
Boeing service information, a joint process improvement initiative was 
worked between the FAA and Boeing. The initiative resulted in the 
development of a new process in which the service information more 
clearly identifies the actions needed to address the unsafe condition 
in the ``Accomplishment Instructions.'' The new process results in a 
Boeing Requirements Bulletin, which contains only the actions needed to 
address the unsafe condition (i.e., only the RC actions).

Costs of Compliance

    The FAA estimates that this proposed AD affects 117 airplanes of 
U.S. registry. The FAA estimates the following costs to comply with 
this proposed AD:

                                      Estimated Costs for Required Actions
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                                                                                                 Cost on U.S.
             Action                      Labor cost          Parts cost    Cost per product        operators
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Repetitive surface HFEC           7 work-hour x $85 per              $0  $595 per inspection  $69,615 per
 inspections.                      hour = $595 per                        cycle.               inspection cycle.
                                   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 11188]]



                 Estimated Costs of On-Condition Actions
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           Labor cost                 Parts cost       Cost per product
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Up to 53 work-hour x $85 per      Up to $1,000......  Up to $5,505.
 hour = Up to $4,505
 (replacement).
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    The FAA has received no definitive data on which to base the cost 
estimates for the on-condition repair specified in this proposed 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

    The FAA determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would not 
have a substantial direct effect on the States, on the relationship 
between the national Government and the States, or on the distribution 
of power and responsibilities among the various levels of government.
    For the reasons discussed above, I certify this proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would 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 Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA proposes to amend 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:

The Boeing Company: Docket No. FAA-2021-0026 Project Identifier AD-
2020-01164-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by April 12, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all The Boeing Company Model 737-100, -200, -
200C, -300, -400, and -500 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 a report indicating that a crack was 
found on the splice angle flange that is attached to the station 
(STA) 540 bulkhead in the area between stringer 21 to stringer 22. 
The FAA is issuing this AD to address any cracking in the splice 
angle, which could result in the inability of a principal structural 
element to sustain limit load and could adversely affect the 
structural integrity of the airplane; in addition, such cracking 
could lead to adjoining parts cracking and a potential fuel leak and 
consequent fire.

(f) Compliance

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

(g) Required Actions

    (1) For airplanes identified as Group 1 in Boeing Alert 
Requirements Bulletin 737-57A1347 RB, dated July 29, 2020: Within 
120 days after the effective date of this AD, inspect the airplane 
and do all applicable on-condition actions using a method approved 
in accordance with the procedures specified in paragraph (i) of this 
AD.
    (2) For airplanes identified as Group 2 in Boeing Alert 
Requirements Bulletin 737-57A1347 RB, dated July 29, 2020: Except as 
specified by paragraph (h) of this AD, at the applicable times 
specified in the ``Compliance'' paragraph of Boeing Alert 
Requirements Bulletin 737-57A1347 RB, dated July 29, 2020, do all 
applicable actions identified in, and in accordance with, the 
Accomplishment Instructions of Boeing Alert Requirements Bulletin 
737-57A1347 RB, dated July 29, 2020.

    Note 1 to paragraph (g):  Guidance for accomplishing the actions 
required by this AD can be found in Boeing Alert Service Bulletin 
737-57A1347, dated July 29, 2020, which is referred to in Boeing 
Alert Requirements Bulletin 737-57A1347 RB, dated July 29, 2020.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Requirements Bulletin 737-57A1347 RB, 
dated July 29, 2020, uses the phrase ``the original issue date of 
Requirements Bulletin 737-57A1347 RB,'' this AD requires using ``the 
effective date of this AD.''
    (2) Where Boeing Alert Requirements Bulletin 737-57A1347 RB, 
dated July 29, 2020, specifies contacting Boeing for repair 
instructions: This AD requires doing the repair 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, Los Angeles 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, 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, Los 
Angeles 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

    (1) For more information about this AD, contact George Garrido, 
Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO

[[Page 11189]]

Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 
562-627-5232; fax: 562-627-5210; email: [email protected].
    (2) 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. You may view this referenced service 
information at the FAA, Airworthiness Products Section, Operational 
Safety Branch, 2200 South 216th St., Des Moines, WA. For information 
on the availability of this material at the FAA, call 206-231-3195.

    Issued on February 3, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.

[FR Doc. 2021-03577 Filed 2-23-21; 8:45 am]
BILLING CODE 4910-13-P