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Federal Register / Vol. 86, No. 195 / Wednesday, October 13, 2021 / Proposed Rules 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: 2024932251.
Mail: U.S. Department of Transportation, Docket Operations, M30, West Building Ground Floor, Room W12140, 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 110SK57, Seal Beach, CA
907405600; telephone 5627971717;
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 206231
3195. It is also available at https
www.regulations.gov by searching for and locating Docket No. FAA2021
0788.

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Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210788; 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: Lu Lu, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198;
phone and fax: 2062313525; email:
lu.lu@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.
FAA20210788; Project Identifier AD
202100489T 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.

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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.

loads on the bulkhead chord that could cause chord failure and adjacent skin failure, resulting in reduced control of the airplane.

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 Lu Lu, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 2062313525; email: lu.lu@
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.

Related Service Information Under 1
CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 73753A1384
RB, dated September 10, 2020. This service information specifies procedures for a detailed inspection for incorrectly installed fasteners at the STA 727
bulkhead outer chord common to the fuselage skin between stringers S22
and S27 on the left and right sides, and applicable on-condition actions. In addition to repair and replacement, oncondition actions include repetitive inspections for cracking of the fuselage skin between stringers S22 and S27;
an open hole high frequency eddy current HFEC inspection for cracking at all incorrectly installed fastener locations; and external and internal general visual inspections for repairs of the STA 727 bulkhead. On-condition actions also include repetitive HFEC
and low frequency eddy current LFEC
inspections in unrepaired areas for cracking of the inner skin from the wheel well; of the outer, upper, and lower chords from the wheel well; and of the fail-safe chord from the cargo compartment.
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.

Background The FAA has received a report indicating incorrectly installed fasteners were found at the station STA 727
bulkhead between stringers S22 and S
27. The fasteners, installed with a gap under the fastener head, were found at the STA 727 bulkhead common to fuselage skin, including the S23 skin lap splice. Incorrectly installed fasteners are suspected to exist on airplanes delivered within a certain time period.
The FAA has confirmed that the fastener installation procedures were corrected on airplanes subsequently delivered. This condition was the result of incorrect procedures used to install affected fasteners during airplane production, which could result in incorrectly installed fasteners going undetected. Continuous operation of the airplane with incorrectly installed fasteners may generate fatigue cracking that could adversely affect the structural integrity of the airplane. Gaps under fastener heads will result in bending
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FAAs 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.

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. FAA2021
0788.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 78
airplanes of U.S. registry. The FAA
estimates the following costs to comply with this proposed AD:

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