DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2021-0788; Project Identifier AD-2021-00489-T]
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
for certain The Boeing Company Model 737-700, -800, and -900ER series
airplanes. This proposed AD was prompted by reports of incorrectly
installed fuselage skin fasteners. This proposed AD would require a
detailed inspection of a certain body station bulkhead, between certain
stringers, for any incorrectly installed fastener common to fuselage
skin, 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 November
ADDRESSES: You may send comments, using the procedures found in
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow
for submitting comments.
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
for and locating Docket No. FAA-2021-0788.
Examining the AD Docket
You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0788; 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: 206-231-3525; email: email@example.com.
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-2021-0788; Project Identifier
AD-2021-00489-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 Lu
Lu, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198; phone and fax: 206-231-3525;
email: firstname.lastname@example.org. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
The FAA has received a report indicating incorrectly installed
fasteners were found at the station (STA) 727 bulkhead between
stringers S-22 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 S-23 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 loads on the bulkhead chord that could cause chord failure and
adjacent skin failure, resulting in reduced control of the airplane.
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 737-53A1384 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 S-22 and S-27 on the left and right sides, and applicable on-
condition actions. In addition to repair and replacement, on-condition
actions include repetitive inspections for cracking of the fuselage
skin between stringers S-22 and S-27; 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.
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-2021-0788.
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:
||13 work-hours x $85 per hour
The FAA estimates the following costs
to do any necessary actions
that would be required based on the results of the proposed inspection.
The agency has no way of determining the number of aircraft that might
need these on-condition actions.
|Open hole HFEC inspections
||21 work-hours x $85 per hour
= $85 per inspection cycle
|$1,785 per inspection cycle
|HFEC and LFEC inspections
||36 work-hours x $85 per hour
= $3,060 per inspection cycle
|3,060 per inspection
The FAA has included all known costs
in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this proposed AD may be covered under warranty, thereby reducing the
cost impact on affected operators.
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.
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
(1) Is not a ``significant regulatory action'' under Executive
(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
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.
Sec. 39.13 [Amended]
2. The FAA amends Sec. 39.13 by adding the following new airworthiness