[Federal Register Volume 86, Number 123 (Wednesday, June 30, 2021)]
[Proposed Rules]
[Pages 34660-34662]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-13930]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0503; Project Identifier AD-2021-00163-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 supersede Airworthiness Directive (AD) 
2005-05-18, which applies to certain The Boeing Company Model 737-600, 
-700, -700C, -800, and -900 series airplanes. AD 2005-05-18 requires 
repetitive inspections for cracking of the webs of the aft pressure 
bulkhead at a certain body station, and corrective action if necessary. 
Since the FAA issued AD 2005-05-18, cracking was found in that 
inspection area on airplanes not identified in the applicability of AD 
2005-05-18. This proposed AD would retain the requirements of AD 2005-
05-18, revise the applicability to include additional airplanes, and 
add an inspection for existing repairs on the newly added airplanes. 
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 August 16, 
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 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-2021-0503.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0503; 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: Wayne Lockett, Aerospace Engineer, 
Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3524; email: 
wayne.lockett@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2021-0503; Project Identifier 
AD-2021-00163-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 Wayne 
Lockett, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3524; email: wayne.lockett@faa.gov. Any commentary that the FAA 
receives which is not specifically designated as CBI will be placed in 
the public docket for this rulemaking.

Background

    The FAA issued AD 2005-05-18, Amendment 39-14007 (70 FR 12410, 
March 14, 2005) (AD 2005-05-18), for certain The Boeing Company Model 
737-600, -700, -700C, -800, and -900 series airplanes. AD 2005-05-18 
was prompted by a report of cracks found, during fatigue testing, at 
several of the fastener rows in the web lap splices at the dome apex of 
the aft pressure bulkhead. AD 2005-05-18 requires repetitive detailed, 
low frequency eddy current (LFEC), and high frequency eddy current 
(HFEC) inspections for cracking of the webs of the aft pressure 
bulkhead at body station (BS) 1016, and corrective action if necessary. 
The FAA issued AD 2005-05-18 to detect and correct fatigue cracks in 
the webs of the aft pressure bulkhead, which could result in rapid 
decompression of the airplane.

Actions Since AD 2005-05-18 Was Issued

    Since the FAA issued AD 2005-05-18, cracking has been found at apex 
webs on airplanes outside the applicability of AD 2005-05-18, which 
includes line numbers 1 through 1166 inclusive. Line numbers 1167 
through 1755 inclusive, which are included in this proposed AD, use a 
revised fastener pattern in the 0.032-inch webs that was intended to 
correct the cracking addressed by AD 2005-05-18. During the assembly 
process on line numbers 1167 through 1755, the fasteners in the apex 
dome region are subjected to

[[Page 34661]]

fuselage pressurization fatigue cycles and clamp-up stresses. Cracks in 
the inspection area of AD 2005-05-18 have now been found on airplanes 
within the range of line numbers 1167 through 1755 inclusive. At one 
location, the crack was linked from the first to the second fastener 
row. This cracking was identified during an inspection for cracking of 
the web lap splice of the aft pressure bulkhead, as required by AD 
2017-10-22, Amendment 39-18896 (82 FR 23507, May 23, 2017) (AD 2017-10-
22). The inspections and intervals specified in AD 2017-10-22 are not 
adequate to address the specific fatigue cracking occurring in the web 
apex area that is the subject of this NPRM.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Alert Service Bulletin 737-53A1251, 
Revision 2, dated January 20, 2021. This service information specifies 
procedures for a general visual inspection for existing repairs, 
repetitive detailed and HFEC inspections for cracks around the web 
fasteners, repetitive LFEC inspection for cracks around the hidden web 
lap splice fastener locations, and repair of cracks. 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.

Proposed AD Requirements in This NPRM

    Although this proposed AD does not explicitly restate the 
requirements of AD 2005-05-18, this proposed AD would retain all of the 
requirements of AD 2005-05-18. Those requirements are referenced in the 
service information identified previously, which, in turn, is 
referenced in paragraph (g) of this proposed AD. This proposed AD would 
revise the applicability to include additional airplanes, and add an 
inspection for existing repairs on those airplanes. This proposed AD 
would also require accomplishment of the actions identified as ``RC'' 
(required for compliance) in the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1251, Revision 2, dated January 20, 2021, 
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-2021-0503.

Differences Between This Proposed AD and the Service Information

    For Group 1 airplanes, the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1251 Revision 2, dated January 20, 2021, 
do not include any ``RC'' (required for compliance) steps. The RC 
tagging was inadvertently removed from Boeing Alert Service Bulletin 
737-53A1251 Revision 2, dated January 20, 2021. For Group 1 airplanes, 
this proposed AD would therefore require treating Step 3.B.2. of the 
Accomplishment Instructions of Boeing Alert Service Bulletin 737-
53A1251 Revision 2, dated January 20, 2021, as an RC step.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 744 airplanes of U.S. registry. The FAA estimates the following 
costs to comply with this proposed AD:

                                                 Estimated Costs
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                                                                                                 Cost on U.S.
             Action                     Labor cost          Parts cost     Cost per product        operators
----------------------------------------------------------------------------------------------------------------
Detailed, HFEC, and LFEC         Up to 10 work-hours x                $0  Up to $850 per      Up to $632,400 per
 inspections.                     $85 per hour = Up to                     inspection cycle.   inspection cycle.
                                  $850 per inspection
                                  cycle.
General visual inspection (194   1 work-hour x $85 per                 0  $85...............  $16,490.
 airplanes).                      hour = $85.
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    The FAA estimates the following costs to do any necessary repairs 
that would be required based on the results of the proposed 
inspections. The FAA has no way of determining the number of aircraft 
that might need these repairs:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
          Action                  Labor cost                 Parts cost                   Cost per product
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Repair....................  Up to 30 * work-hours  Up to $30,000 *...............  Up to $32,550 *
                             x $85 per hour = Up
                             to $2,550.
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* Repair costs will vary depending on size of the repair required.

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 has 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 that the proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and

[[Page 34662]]

    (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:
0
a. Removing Airworthiness Directive (AD) 2005-05-18, Amendment 39-14007 
(70 FR 12410, March 14, 2005), and
0
b. Adding the following new AD:

The Boeing Company: Docket No. FAA-2021-0503; Project Identifier AD-
2021-00163-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by August 16, 2021.

(b) Affected ADs

    This AD replaces AD 2005-05-18, Amendment 39-14007 (70 FR 12410, 
March 14, 2005) (AD 2005-05-18).

(c) Applicability

    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 Service Bulletin 737-53A1251 Revision 
2, dated January 20, 2021.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by a report of cracks found at several of 
the fastener rows in the web lap splices at the dome apex of the aft 
pressure bulkhead, and the determination that airplanes not affected 
by AD 2005-05-18 are subject to this unsafe condition. The FAA is 
issuing this AD to address fatigue cracks in the webs of the aft 
pressure bulkhead, which could result in rapid decompression 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 paragraph 1.E., ``Compliance,'' of 
Boeing Alert Service Bulletin 737-53A1251 Revision 2, dated January 
20, 2021, do all applicable actions identified as ``RC'' (required 
for compliance) in, and in accordance with, the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-53A1251 Revision 
2, dated January 20, 2021. For Group 1 airplanes, as defined in 
Boeing Alert Service Bulletin 737-53A1251 Revision 2, dated January 
20, 2021: Step 3.B.2. of the Accomplishment Instructions of Boeing 
Alert Service Bulletin 737-53A1251 Revision 2, dated January 20, 
2021, is an RC step, and the provisions of paragraphs (j)(5)(i) and 
(ii) of this AD apply.

(h) Exceptions to Service Information Specifications

    (1) Where Boeing Alert Service Bulletin 737-53A1251 Revision 2, 
dated January 20, 2021, uses the phrase ``the Revision 1 date of 
this service bulletin,'' this AD requires using ``the effective date 
of this AD.''
    (2) Where Boeing Alert Service Bulletin 737-53A1251, Revision 2, 
dated January 20, 2021, 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 (j) of this AD.

(i) Credit for Previous Actions

    (1) For airplanes having line numbers 1 through 1166 inclusive: 
This paragraph provides credit for the corresponding actions of 
Boeing Alert Service Bulletin 737-53A1251 Revision 2, dated January 
20, 2021, that are required by paragraph (g) of this AD, if those 
actions were performed before the effective date of this AD using 
Boeing Service Bulletin 737-53-1251, dated June 3, 2004, which was 
incorporated by reference in AD 2005-05-18.
    (2) This paragraph provides credit for the corresponding actions 
of Boeing Alert Service Bulletin 737-53A1251 Revision 2, dated 
January 20, 2021, that are required by paragraph (g) of this AD, if 
those actions were performed before the effective date of this AD 
using Boeing Alert Service Bulletin 737-53-1251, Revision 1, dated 
September 22, 2020, which is not incorporated by reference in 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 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 Related Information. Information may be emailed to: 9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by The Boeing Company Organization Designation 
Authorization (ODA) that has been authorized by the Manager, Seattle 
ACO Branch, FAA, to make those findings. To be approved, the repair 
method, modification deviation, or alteration deviation must meet 
the certification basis of the airplane, and the approval must 
specifically refer to this AD.
    (4) AMOCs approved for AD 2005-05-18 are approved as AMOCs for 
the corresponding provisions of Boeing Alert Service Bulletin 737-
53A1251 Revision 2, dated January 20, 2021, that are required by 
paragraph (g) of this AD.
    (5) Except as specified by paragraph (h) of this AD: For service 
information that contains steps that are labeled as Required for 
Compliance (RC), the provisions of paragraphs (j)(5)(i) and (ii) of 
this AD apply.
    (i) The steps labeled as RC, including substeps under an RC step 
and any figures identified in an RC step, must be done to comply 
with the AD. If a step or substep is labeled ``RC Exempt,'' then the 
RC requirement is removed from that step or substep. An AMOC is 
required for any deviations to RC steps, including substeps and 
identified figures.
    (ii) Steps not labeled as RC may be deviated from using accepted 
methods in accordance with the operator's maintenance or inspection 
program without obtaining approval of an AMOC, provided the RC 
steps, including substeps and identified figures, can still be done 
as specified, and the airplane can be put back in an airworthy 
condition.

(k) Related Information

    (1) For more information about this AD, contact Wayne Lockett, 
Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3524; 
email: wayne.lockett@faa.gov.
    (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 June 11, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-13930 Filed 6-29-21; 8:45 am]
BILLING CODE 4910-13-P


