Federal Register / Vol. 87, No. 38 / Friday, February 25, 2022 / Proposed Rules 10755 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2022–0093; Project 

Identifier AD–2021–00987–T] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: The FAA proposes to adopt a 

new airworthiness directive (AD) for 

certain The Boeing Company Model 

737–600, –700, –700C, –800, and –900 

series airplanes. This proposed AD was 

prompted by an evaluation by the 

design approval holder (DAH) 

indicating that certain web lap splices 

in the center dome apex of the aft 

pressure bulkhead are subject to 

widespread fatigue damage (WFD). This 

proposed AD would require a general 

visual inspection for existing repairs at 

the aft pressure bulkhead, repetitive 

detailed, high frequency eddy current 

(HFEC), and low frequency eddy current 

(LFEC) inspections, and repair if 

necessary. 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 11, 2022. 

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 at https://

www.regulations.gov by searching for 

and locating Docket No. FAA–2022– 

0093. 

Examining the AD Docket 

You may examine the AD docket at 

https://www.regulations.gov by 

searching for and locating Docket No. 

FAA–2022–0093; 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: Dirk 

Visser, Aerospace Engineer, Airframe 

Section, FAA, Seattle ACO Branch, 2200 

South 216th St., Des Moines, WA 98198; 

phone and fax: 206–231–3994; email: 

Dirk.J.Visser@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–2022–0093; Project Identifier AD– 

2021–00987–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 this 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 NPRM. 

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 Dirk Visser, Aerospace 

Engineer, Airframe Section, FAA, 

Seattle ACO Branch, 2200 South 216th 

St., Des Moines, WA 98198; phone and 

fax: 206–231–3994; email: 

Dirk.J.Visser@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 

Fatigue damage can occur locally, in 

small areas or structural design details, 

or globally, in widespread areas. 

Multiple-site damage is widespread 

damage that occurs in a large structural 

element such as a single rivet line of a 

lap splice joining two large skin panels. 

Widespread damage can also occur in 

multiple elements such as adjacent 

frames or stringers. Multiple-site 

damage and multiple-element damage 

cracks are typically too small initially to 

be reliably detected with normal 

inspection methods. Without 

intervention, these cracks will grow, 

and eventually compromise the 

structural integrity of the airplane. This 

condition is known as WFD. It is 

associated with general degradation of 

large areas of structure with similar 

structural details and stress levels. As 

an airplane ages, WFD will likely occur, 

and will certainly occur if the airplane 

is operated long enough without any 

intervention. 

An FAA final rule (‘‘Aging Airplane 

Program: Widespread Fatigue Damage;’’ 

75 FR 69746, November 15, 2010) 

became effective on January 14, 2011, 

and amended 14 CFR parts 25, 26, 121, 

and 129 (commonly known as the WFD 

rule). The WFD rule requires certain 

actions to prevent structural failure due 

to WFD throughout the operational life 

of certain existing transport category 

airplanes and all of these airplanes that 

will be certificated in the future. DAHs 

of existing and future airplanes subject 

to the WFD rule are required to establish 

a limit of validity (LOV) of the 

engineering data that support the 

structural maintenance program. 

Operators affected by the WFD rule may 

not fly an airplane beyond its LOV, 

unless an extended LOV is approved. 

The WFD rule does not require 

identifying and developing maintenance 

actions if the DAHs can show that such 

actions are not necessary to prevent 

WFD before the airplane reaches the 

LOV. Many LOVs, however, do depend 


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on accomplishment of future 

maintenance actions. As stated in the 

WFD rule, any maintenance actions 

necessary to reach the LOV will be 

mandated by airworthiness directives 

through separate rulemaking actions. 

In the context of WFD, this action is 

necessary to enable DAHs to propose 

LOVs that allow operators the longest 

operational lives for their airplanes, and 

still ensure that WFD will not occur. 

This approach allows for an 

implementation strategy that provides 

flexibility to DAHs in determining the 

timing of service information 

development (with FAA approval), 

while providing operators with certainty 

regarding the LOV applicable to their 

airplanes. 

The FAA has received an evaluation 

by the DAH indicating that certain web 

lap splices in the center dome apex of 

the aft pressure bulkhead are subject to 

WFD. During cycle tests of The Boeing 

Company Model 737–800 series 

airplanes’ Fatigue Test Article for the 

0.032 inch web (the configuration for 

The Boeing Company Model 737–600, 

–700, –700C, –800, and –900 series 

airplane having line numbers (LN) 1 

through 1166), cracks were found in 

three of the seven aft pressure bulkhead 

web lap splices in several of the fastener 

rows common to the center dome apex. 

The pull down stresses were caused by 

the single rivet located in the area where 

each of the webs transition up 0.032 

inches. Airplanes having LN 1167 

through 1755 inclusive have a different 

fastener pattern than airplanes having 

LN 1 through 1166 inclusive, but are 

subject to the same unsafe condition. 

There has been only one reported 

finding on airplanes having LN 1167 

through 1755 inclusive and cracking 

was found in five of the seven webs. 

The FAA issued AD 2021–21–09, 

Amendment 39–21769 (86 FR 61679, 

November 8, 2021) to address fatigue 

cracks in the webs of the aft pressure 

bulkhead on The Boeing Company 

Model 737–600, –700, –700C, –800, and 

–900 airplanes having LN 1 through 

1755 inclusive. 

The Boeing Company Model 737–600, 

–700, –700C, –800, and –900 airplanes 

having LN 1756 and subsequent (which 

are addressed in this proposed AD) have 

a 0.040 inch web thickness. Following 

the findings in the earlier LNs, 

supplemental testing showed an 

increase in the pull down stress for the 

0.040 inch aft pressure bulkhead 

configuration in the same transition area 

as seen in the 0.032 inch configuration. 

The aft pressure bulkhead web lap 

splice fasteners are subjected to fuselage 

pressurization fatigue cycles and 

additional clamp-up stress caused from 

the assembly process. The clamp up 

stresses, combined with the 

pressurization, cause the existing 

airworthiness limitations inspections for 

Principle Structural Element 53–80–01– 

3 (visible web rows) and 53–80–01–7 

(hidden web rows) to be inadequate. 

Therefore, the FAA determined that 

additional inspections of the 0.040 inch 

thick web lap splices at station 1016 aft 

pressure bulkhead center dome apex for 

any crack are necessary to mitigate the 

identified unsafe condition. This 

condition, if not addressed, could result 

in reduced structural integrity of the 

airplane. 

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 

Requirements Bulletin 737–53A1403 

RB, dated August 26, 2021. This service 

information specifies procedures for a 

general visual inspection for existing 

repairs at the aft pressure bulkhead, 

repetitive detailed, HFEC, and LFEC 

inspections for any crack, 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. 

Proposed AD Requirements in This 

NPRM 

This proposed AD would require 

accomplishing the actions specified in 

the service information already 

described 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–2022– 

0093. 

Costs of Compliance 

The FAA estimates that this AD, if 

adopted as proposed, would affect 1,187 

airplanes of U.S. registry. The FAA 

estimates the following costs to comply 

with this proposed AD: 

ESTIMATED COSTS

Action Labor cost Parts cost Cost per product Cost on U.S. operators 

Inspection for repairs ............. 1 work-hour × $85 per hour = 

$85.

$0 ..................... $85 ........................................ $100,895. 

Repetitive detailed, HFEC, 

and LFEC inspections.

Up to 9 work-hours × $85 per 

hour = $765 per inspection 

cycle.

Up to $0 ........... Up to $765 per inspection 

cycle.

Up to $908,055 per inspection cycle. 

The FAA has received no definitive 

data on which to base the cost estimates 

for the on-condition repairs 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 


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Federal Register / Vol. 87, No. 38 / Friday, February 25, 2022 / Proposed Rules 10757 

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 

■ 1. The authority citation for part 39 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701. 

§ 39.13 [Amended] 

■ 2. The FAA amends § 39.13 by adding 

the following new airworthiness 

directive: 

The Boeing Company: Docket No. FAA– 

2022–0093; Project Identifier AD–2021– 

00987–T. 

(a) Comments Due Date 

The FAA must receive comments on this 

airworthiness directive (AD) by April 11, 

2022. 

(b) Affected ADs 

None. 

(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 Requirements 

Bulletin 737–53A1403 RB, dated August 26, 

2021. 

(d) Subject 

Air Transport Association (ATA) of 

America Code 53, Fuselage. 

(e) Unsafe Condition 

This AD was prompted by an evaluation by 

the design approval holder (DAH) indicating 

that certain web lap splices in the center 

dome apex of the aft pressure bulkhead are 

subject to widespread fatigue damage (WFD). 

The FAA is issuing this AD to address fatigue 

cracks in the webs of the aft pressure 

bulkhead, which could result in 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 737–53A1403 RB, 

dated August 26, 2021, do all applicable 

actions identified in, and in accordance with, 

the Accomplishment Instructions of Boeing 

Alert Requirements Bulletin 737–53A1403 

RB, dated August 26, 2021. 

Note 1 to paragraph (g): Guidance for 

accomplishing the actions required by this 

AD can be found in Boeing Alert Service 

Bulletin 737–53A1403, dated August 26, 

2021, which is referred to in Boeing Alert 

Requirements Bulletin 737–53A1403 RB, 

dated August 26, 2021. 

(h) Exceptions to Service Information 

Specifications 

(1) Where the Compliance Time column of 

the table in the ‘‘Compliance’’ paragraph of 

Boeing Alert Requirements Bulletin 737– 

53A1403 RB, dated August 26, 2021, uses the 

phrase ‘‘the original issue date of the 

Requirements Bulletin 737–53A1403 RB,’’ 

this AD requires using ‘‘the effective date of 

this AD.’’ 

(2) Where Boeing Alert Requirements 

Bulletin 737–53A1403 RB, dated August 26, 

2021, specifies contacting Boeing for repair 

instructions or for alternative inspections: 

This AD requires doing the repair, or doing 

the alternative inspections and applicable oncondition 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: 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. 

(j) Related Information 

(1) For more information about this AD, 

contact Dirk Visser, Aerospace Engineer, 

Airframe Section, FAA, Seattle ACO Branch, 

2200 South 216th St., Des Moines, WA 

98198; phone and fax: 206–231–3994; email: 

Dirk.J.Visser@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 February 3, 2022. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2022–03968 Filed 2–24–22; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF HOMELAND 

SECURITY 

Coast Guard 

33 CFR Part 165 

[Docket No. USCG–2021–0345] 

Vessel Traffic Assessment: Near Point 

Mugu, San Francisco Bay, Humboldt 

Bay, and Morro Bay, CA 

AGENCY: Coast Guard, DHS. 

ACTION: Notification of inquiry; request 

for comments. 

SUMMARY: On July 28, 2021, U.S. Coast 

Guard (USCG) Pacific Area Command 

issued the Pacific Coast–Port Access 

Route Study (PAC–PARS) in the Federal 

Register directing USCG District Eleven 

and USCG District Thirteen to complete 

a PARS on the Pacific coast. In support 

of the PAC–PARS, USCG District Eleven 

has identified four areas to evaluate 

activities within its area of 

responsibility. USCG District Eleven 

requests public comments regarding 

vessel traffic patterns in the areas near 

Point Mugu and south of the Channel 

Islands in the Pacific Missile Range, San 

Francisco Bay, and the Bureau of Ocean 

Energy Management (BOEM) Humboldt 

Bay and Morro Bay offshore Wind 

Energy Areas (WEAs). Information 

received will be used to make 

recommendations regarding establishing 

safety routing measures to improve 

waterway operations and vessel 

movement along the California coast. 

DATES: Comments and related material 

must be received on or before May 26, 

2022. 

ADDRESSES: You may submit comments 

identified by docket number USCG– 


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