34660 Federal Register / Vol. 86, No. 123 / Wednesday, June 30, 2021 / Proposed Rules 

Issued on June 6, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–13932 Filed 6–29–21; 8:45 am] 

BILLING CODE 4910–13–P 

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). 

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 


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Federal Register / Vol. 86, No. 123 / Wednesday, June 30, 2021 / Proposed Rules 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

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

Detailed, HFEC, and 

LFEC inspections.

Up to 10 work-hours × $85 per hour = Up to 

$850 per inspection cycle.

$0 Up to $850 per inspection cycle.Up to $632,400 per inspection cycle. 

General visual inspection (194 airplanes).1 work-hour × $85 per hour = $85 ..................... 0 $85 ............................... $16,490. 

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 

Repair ............... Up to 30 * work-hours × $85 per hour = Up to $2,550 ........................................... Up to $30,000 * ...... Up to $32,550 * 

* 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 


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34662 Federal Register / Vol. 86, No. 123 / Wednesday, June 30, 2021 / Proposed Rules 

(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: 

■ a. Removing Airworthiness Directive 

(AD) 2005–05–18, Amendment 39– 

14007 (70 FR 12410, March 14, 2005), 

and 

■ 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 oncondition 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-ANMSeattle-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 


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