[Federal Register Volume 87, Number 178 (Thursday, September 15, 2022)]
[Rules and Regulations]
[Pages 56563-56566]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-19902]


-----------------------------------------------------------------------

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-1168; Project Identifier AD-2021-00825-T; 
Amendment 39-22138; AD 2022-16-09]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain The Boeing Company Model 737-8 airplanes. This AD was prompted 
by a report that, during production, a small number of fasteners in 
certain locations of the center fuel tank were cap sealed on top of a 
black stripe of ink with a clear overcoat. This clear overcoat is not 
an approved surface for sealing and can potentially compromise sealant 
adhesion. Compromised sealant adhesion can, over time, affect the 
lightning-protection properties of the airplane. This AD requires 
preparation of the affected surface areas to ensure that there is 
adequate sealant adhesion, and complete encapsulation of the discrepant 
fastener locations with the approved production sealant. The FAA is 
issuing this AD to address the unsafe condition on these products.

DATES: This AD is effective October 20, 2022.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of October 20, 
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 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 www.regulations.gov by 
searching for and locating Docket No. FAA-2021-1168.

Examining the AD Docket

    You may examine the AD docket at www.regulations.gov by searching 
for and locating Docket No. FAA-2021-1168; 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: Chris Baker, Aerospace Engineer, 
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3552; email: 
[email protected].

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 737-8 airplanes. The NPRM published in the Federal 
Register on February 23, 2022 (87 FR 10110). The NPRM was prompted by a 
report that, during production, a small number of fasteners common to 
upper wing panel stringers U-S1, U-S10, U-S12, U-S20, and U-S21 and 
lower wing panel stringer L-S14 were cap sealed on top of a black 
stripe of ink with a clear overcoat. The black stripe of ink and clear 
overcoat were applied during airplane assembly to certain interior 
areas of the center fuel tank to ensure proper alignment of components, 
and this discrepancy was not identified by Boeing prior to the delivery 
of certain airplanes. The purpose of cap sealing is to provide a 
secondary layer of lightning protection to the metal-to-metal rivet 
installation bond. The clear overcoat is not an approved surface for 
sealing and can potentially compromise sealant adhesion.
    Compromised sealant adhesion can, over time, affect the lightning 
protection properties of the airplane. In the NPRM, the FAA proposed to 
require preparation of the affected surface areas to ensure that there 
is adequate sealant adhesion, and complete encapsulation of the 
discrepant fastener locations with

[[Page 56564]]

the approved production sealant. This condition, if not addressed and 
combined with a flammable center tank ullage and an independent failure 
of the primary lightning protection feature, could result in ignition 
of the fuel vapors and subsequent explosion in the event of a lightning 
strike to that fastener.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from Air Line Pilots Association, 
International (ALPA) and an anonymous commenter, who supported the NPRM 
without change.
    The FAA received additional comments from two commenters, Boeing 
and Southwest Airlines (SWA). The following presents the additional 
comments received on the NPRM and the FAA's response to each comment.

Request To Add Alternative Methods of Compliance to the Final Rule

    SWA requested that the FAA provide an option to operators that 
would allow removal of the current application of BMS5-45 sealant in 
the affected areas and removal of the black stripe of ink in accordance 
with certain operator procedures (or other acceptable procedures), then 
allowing for refinishing and sealing of the affected area in accordance 
with certain other operator instructions. SWA reasoned that these 
additional methods would address the unsafe condition and would allow 
airworthiness limitation (AWL) inspections and standard maintenance to 
be accomplished as intended in the structural repair manual (SRM) and 
maintenance planning document (MPD).
    SWA explained that it is concerned that extending BMS5-45 sealant 
0.6 inches beyond the current production application area could prevent 
inspections performed in accordance with 737-7/8/8200/9/10 
Airworthiness Limitations (AWL) D626A011-9-04 and MPD principal 
structural element (PSE) 57-020-00. SWA went on to explain that 
extending the BMS5-45 sealant up to 0.6 inches beyond the current 
production application area to encapsulate the discrepant area 
contradicts the sealant restoration procedures outlined in 737-8MAX SRM 
51-80-01 which states, ``SEALANT MUST NOT EXTEND MORE THAN 0.125 INCH 
(3.18mm) ON TO THE SURFACE OF THE PART FOR DAMAGE TOLERANCE INSPECTION 
REASONS.'' SWA expressed concern that if an airplane requires repairs 
or maintenance actions in the affected area, or requires AWL/MPD 
required inspection 57-020-00, the BMS5-45 sealant will be stripped 
and, if the affected area is restored in accordance with 737-8MAX SRM 
51-80-01, could lead to an operator inadvertently undoing the actions 
specified in Boeing Special Attention Requirements Bulletin 737-57-1352 
RB, dated February 1, 2021.
    The FAA agrees that the service bulletin instructions could 
conflict with future actions required by the 737-7/8/8200/9/10 
Airworthiness Limitations (AWL) D626A011-9-04, in that the added 
sealant might impede the operator's ability to inspect the structure. 
The FAA also agrees that operators could use the existing sealant 
restoration procedures to remove the current application of BMS5-45 
sealant in the discrepant areas, remove the black stripe of ink in 
accordance with acceptable surface preparation procedures, and reseal 
the fasteners in accordance with standard sealing procedures of 
fasteners penetrating the fuel tank. The FAA has added an optional 
method of removing the existing sealant and black stripe of ink prior 
to reapplying a fastener seal in paragraph (h) of this AD and 
redesignated subsequent paragraphs.

Request for Additional Detail to the Unsafe Condition Statement

    Boeing requested that the unsafe condition statement found in the 
Background section of the preamble and paragraph (e) of the proposed AD 
include more detail of the conditions and failures required for a fuel 
tank ignition to occur. Boeing stated that in the proposed AD, the 
unsafe condition statement lists only compromised sealant adhesion as 
the condition needed for an ignition of fuel tank vapors in the event 
of a lightning strike. Boeing pointed out that ignition of fuel tank 
vapor requires an independent failure of the primary ignition 
prevention feature, a failed cap seal, a lightning attachment to the 
particular fastener, and that the fuel tank is flammable.
    Boeing requested that the FAA change the fifth sentence in the 
Background section of the proposed AD to state, ``This condition, if 
not addressed and combined with a flammable center tank ullage and an 
independent failure of the primary lightning protection feature, could 
result in ignition of the fuel vapors and subsequent explosion in the 
event of a lightning strike to that fastener.'' Boeing requested 
similar changes to the second sentence of paragraph (e) of the proposed 
AD.
    The FAA agrees with the request for the reasons provided. Boeing 
provided a more detailed description of the potential failure sequence. 
The FAA has revised the Background section of this final rule and the 
second sentence of paragraph (e) of this AD accordingly.

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, and any other changes 
described previously, 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 Special Attention Requirements Bulletin 
737-57-1352 RB, dated February 1, 2021. This service information 
specifies procedures for preparing the surface and completely 
encapsulating the black stripe of ink, the clear overcoat, and the 
existing sealant with the approved production (BMS5-45) sealant at 
upper stringer U-S1, U-S10, U-S12, U-S20, and U-S21, and lower stringer 
L-S14. The affected areas are all located on the portion of the 
stringers just outboard of the center wing box. 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 11 airplanes of U.S. 
registry. The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                    Cost per       Cost on U.S.
               Action                        Labor cost           Parts cost        product         operators
----------------------------------------------------------------------------------------------------------------
Apply Sealant.......................  106 work-hours x $85               $500           $9,510         $104,610
                                       per hour = $9,010.
----------------------------------------------------------------------------------------------------------------


[[Page 56565]]


                                      Estimated Costs for Optional Actions
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Remove Sealant and Black Stripe of Ink, and     118 work-hours x $85 per hour =             $500         $10,030
 Reapply Fastener Seal.                          $10,030.
----------------------------------------------------------------------------------------------------------------

    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

0
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]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

2022-16-09 The Boeing Company: Amendment 39-22138; Docket No. FAA-
2021-1168; Project Identifier AD-2021-00825-T.

(a) Effective Date

    This airworthiness directive (AD) is effective October 20, 2022.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-8 airplanes, 
certificated in any category, as identified in Boeing Special 
Attention Requirements Bulletin 737-57-1352 RB, dated February 1, 
2021.

(d) Subject

    Air Transport Association (ATA) of America Code 57, Wings.

(e) Unsafe Condition

    This AD was prompted by a report that, during production, a 
small number of fasteners in certain locations of the center fuel 
tank were cap sealed on top of a black stripe of ink with a clear 
overcoat. This clear overcoat is not an approved surface for sealing 
and can potentially compromise sealant adhesion. Compromised sealant 
adhesion can, over time, affect the lightning protection properties 
of the airplane. The FAA is issuing this AD to address compromised 
sealant adhesion within the center fuel tank, which, if combined 
with a flammable center tank ullage and an independent failure of 
the primary lightning protection feature, could result in ignition 
of fuel vapors and subsequent explosion of the fuel tank in the 
event of a lightning strike to that fastener.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Required Actions

    Within 10 years after the date of issuance of the original 
airworthiness certificate or the original export certificate of 
airworthiness, do all applicable actions identified in, and in 
accordance with, the Accomplishment Instructions of Boeing Special 
Attention Requirements Bulletin 737-57-1352 RB, dated February 1, 
2021, except as specified by paragraph (h) of this AD.
    Note 1 to paragraph (g): Guidance for accomplishing the actions 
required by this AD can be found in Boeing Special Attention Service 
Bulletin 737-57-1352, dated February 1, 2021, which is referred to 
in Boeing Special Attention Requirements Bulletin 737-57-1352 RB, 
dated February 1, 2021.

(h) Optional Method To Remove Previously Applied Sealant and Black 
Stripe of Ink, and Reapply Fastener Seal

    As an option to the sealant application required by paragraph 
(g) of this AD, it is acceptable to remove the existing sealant and 
the black stripe of ink prior to reapplying a fastener seal. Remove 
existing sealant and black stripe of ink as follows:
    (1) Remove existing sealant to expose the black stripe of ink.
    (2) Remove existing black stripe of ink using aluminum oxide 
cloth or paper, 150 to 220 grit.
    Note 2 to paragraph (h)(2): Take caution not to abrade through 
the existing oven cured BMS10-20 coating under the black stripe of 
ink. The BMS10-20 was previously applied during production.
    (3) Touch up exposed aluminum with Alodine 600 (Type I, II, or 
III) or Bonderite M-CR 600 Aero (Type I, II, or III).
    (4) Apply fastener seal (cap seal) with BMS5-45.
    (5) Apply BMS10-20 Type II fuel tank coating to any exposed 
alodine/bonderite surfaces not covered by the fastener seal; it is 
acceptable to extend BMS10-20 Type II coating over fastener seal.

(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: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.

[[Page 56566]]

    (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 Chris Baker, 
Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3552; email: [email protected].
    (2) Service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraphs (k)(3) and (4) of this AD.

(k) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (i) Boeing Special Attention Requirements Bulletin 737-57-1352 
RB, dated February 1, 2021.
    (ii) [Reserved]
    (3) 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 www.myboeingfleet.com.
    (4) 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.
    (5) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on July 29, 2022.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2022-19902 Filed 9-14-22; 8:45 am]
BILLING CODE 4910-13-P


