DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-1169; Project Identifier AD-2021-01011-T;
Amendment 39-22008; AD 2022-08-05]
RIN 2120-AA64

Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain The Boeing Company Model 737-800 series airplanes. This AD was
prompted by the determination that insufficient sealing may allow water
to enter the lower lobe electronic equipment (EE) bay through the main
deck floor structure at the rigid cargo barrier (RCB), which could
cause damage to EE bay line replacement units (LRUs) in the E5 rack.
This AD requires detailed inspections for the presence and condition of
sealant at certain locations and applicable on-condition actions. This
AD also requires replacing the moisture barrier tape at a certain
location, replacing the weather seal at a certain location, and
installing seat track fillers. The FAA is issuing this AD to address
the unsafe condition on these products.

DATES: This AD is effective May 27, 2022
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of May 27,
2022.

ADDRESSES: For service information identified in this final rule,
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-2021-1169.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-1169; 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 final rule, any
comments received, and other information. The address for Docket
Operations is U.S. Department of Transportation, Docket Operations, M-
30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue
SE, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: Courtney Tuck, Aerospace Engineer,
Cabin Safety and Environmental Systems Section, FAA, Seattle ACO
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-
231-3986; email: courtney.k.tuck@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

The FAA issued a notice of proposed rulemaking (NPRM) to amend 14
CFR part 39 by adding an AD that would apply to certain The Boeing
Company Model 737-800 series airplanes. The
NPRM published in the Federal Register on January 26, 2022 (87 FR
3946). The NPRM was prompted by the determination that insufficient
sealing may allow water to enter the lower lobe EE bay through the main
deck floor structure at the RCB, which could cause damage to EE bay
LRUs in the E5 rack. In the NPRM, the FAA proposed to require detailed
inspections for the presence and condition of sealant at certain
locations and applicable on-condition actions. The NPRM also proposed
to require replacing the moisture barrier tape at a certain location,
replacing the weather seal at a certain location, and installing seat
track fillers. The FAA is issuing this AD to address water ingress in
the lower lobe EE bay, which could result in water damage to the air
data inertial reference units and flight management computers during
flight, leading to a complete loss of data to primary flight displays
and electronic navigation functions, which could prevent continued safe
flight and landing.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from Air Line Pilots Association,
International (ALPA), Boeing, and an individual, who supported the NPRM
without change.
The FAA received an additional comment from Aviation Partners
Boeing (APB). The following presents the comment received on the NPRM
and the FAA's response to the comment.

Effect of Winglets on Accomplishment of the Proposed Actions

APB stated that the installation of winglets per Supplemental Type
Certificate (STC) ST00830SE does not affect compliance with the
mandated actions in the proposed rule.
The FAA agrees with the commenter. Therefore, the installation of
STC ST00830SE does not affect the ability to accomplish the actions
required by this AD. The FAA has not changed this AD in this regard.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, and determined that air safety requires adopting this AD as
proposed. Except for minor editorial changes, this AD is adopted as
proposed in the NPRM. None of the changes will increase the economic
burden on any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1401 RB,
dated April 27, 2021. This service information specifies procedures for
detailed inspections of the forward main deck cargo compartment floor
to RCB, floor panel joints, drain troughs, seat track splices, and, for
some airplanes, the lower lobe E5 rack drain pan shroud for sealant
condition and application, and applicable on-condition actions. This
service information also specifies procedures for replacing the main
deck cargo door weather seal, replacing the moisture barrier tape on
the forward main deck cargo compartment floor, and installing seat
track fillers in the EE bay. On-condition actions include repair,
removing existing sealant, and applying new sealant. 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.

Costs of Compliance

The FAA estimates that this AD affects 7 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs

The FAA estimates the following costs to do any necessary
replacements that would be required based on the results of the
inspection. The agency has no way of determining the number of aircraft
that might need these replacements:

On-Condition Costs

The FAA has received no definitive data on which to base the cost
estimates for the on-condition actions specified in this AD.
The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this 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.

Regulatory Findings

This AD will not have federalism implications under Executive Order
13132. This AD will 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 this AD:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Will not affect intrastate aviation in Alaska, and
(3) Will 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 Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA amends 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
directive: