[Federal Register Volume 85, Number 88 (Wednesday, May 6, 2020)]
[Proposed Rules]
[Pages 26893-26896]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-09396]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0331; Product Identifier 2020-NM-019-AD]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain The Boeing Company Model 737-600, -700, -700C, -800, -900, 
and -900ER series airplanes. This proposed AD was prompted by a report 
that the

[[Page 26894]]

necessary sealant was not applied to the side of body (SOB) slot as a 
result of a production drawing that provided unclear SOB slot sealant 
application instructions. This proposed AD would require a general 
visual inspection for insufficient sealant in the SOB slot, and related 
investigative and corrective 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 June 22, 
2020.

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 on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-
0331.

Examining the AD Docket

    You may examine the AD docket on the internet at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-
0331; 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. Comments will be 
available in the AD docket shortly after receipt.

FOR FURTHER INFORMATION CONTACT: James Laubaugh, Aerospace Engineer, 
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3622; email: 
[email protected].

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 the ADDRESSES section. Include ``Docket No. FAA-2020-0331; 
Product Identifier 2020-NM-019-AD'' at the beginning of your comments. 
The FAA specifically invites comments on the overall regulatory, 
economic, environmental, and energy aspects of this NPRM. The FAA will 
consider all comments received by the closing date and may amend this 
NPRM because of those comments.
    The FAA will post all comments, without change, to https://www.regulations.gov, including any personal information you provide. 
The FAA will also post a report summarizing each substantive verbal 
contact received about this NPRM.

Discussion

    The FAA has received a report indicating that the necessary sealant 
was not applied to the SOB slot as a result of a production drawing 
providing unclear SOB slot sealant application instructions on certain 
The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER 
series airplanes. In 2019, an operator of a Model 737-800 airplane 
reported a fuel smell in the cabin, and the airplane was diverted. 
During post-flight inspection, insulation blankets in the air 
distribution mix bay (ADMB) were found to be soaked with fuel. The ADMB 
is located in the fuselage lower lobe immediately forward of the body 
station (BS) 540 front spar bulkhead. An investigation of this incident 
led to the finding that there was no sealant applied in the SOB slot. 
For any part of a fuel tank that is inside the pressurized boundary, a 
secondary fuel barrier is required. On The Boeing Company Model 737-
600, -700, -700C, -800, -900, and -900ER series airplanes, the areas 
requiring secondary barrier are the wing center section upper surface 
and the part of the wing center section front spar that is inside the 
pressure boundary. The secondary barrier is achieved by application of 
BMS 5-81 secondary fuel barrier sealant (commonly referred to as 
``vapor barrier''). On the reporting airplane, sealant inside the 
center fuel tank was repaired to correct the primary leak in the tank, 
and the SOB slot sealant was restored. The investigation concluded that 
the production drawing lacked clarity regarding the SOB slot sealant 
application. The drawing was revised beginning at line number (L/N) 
937, but production planning did not reflect the drawing change until 
L/N 1935. The ADMB is not a flammable fluid leakage zone and therefore 
does not have ignition prevention and fire detection features, and is 
also immediately adjacent to the passenger compartment. Fuel leaking 
into the ADMB, if not addressed, could possibly lead to an ignition of 
flammable fluid vapors, fire, or explosion, or fuel vapor inhalation by 
passengers and crew.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing Multiple Operator Message MOM-MOM-20-0049-
01B (R1), dated January 29, 2020. This service information describes 
procedures for a general visual inspection for insufficient sealant in 
the SOB slot. The service information also describes procedures for 
related investigative actions including a general visual inspection of 
the ADMB for fuel contamination, a check for external leaks of the 
center fuel tank external surfaces inside the pressure boundary, and an 
internal leak check of the center fuel tank to identify the leakage 
path(s). The service information also describes procedures for 
corrective actions including removal of all insulation blankets below 
the crease beam left side to right side, clean-up of all fuel 
contamination, repair of any leak, preparation of the SOB slot for 
sealing, application of sealant, and repair of the secondary fuel 
barrier. 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.

FAA's Determination

    The FAA is proposing this AD because the FAA evaluated all the 
relevant information and determined the unsafe condition described 
previously is likely to exist or develop in other products of the same 
type design.

Proposed AD Requirements

    This proposed AD would require accomplishing the actions specified 
in the service information described previously. For information on the 
procedures, see this service information at https://www.regulations.gov 
by searching for and locating Docket No. FAA-2020-0331.

[[Page 26895]]

Costs of Compliance

    The FAA estimates that this proposed AD affects 731 airplanes of 
U.S. registry. The FAA estimates the following costs to comply with 
this proposed AD:

                                                 Estimated Costs
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                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Inspection for sealant................  30 work-hours x $85 per               $0          $2,550      $1,864,050
                                         hour = $2,550.
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    The FAA estimates the following costs to do any necessary repairs 
that would be required based on the results of the proposed inspection. 
The FAA has no way of determining the number of aircraft that might 
need these repairs:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Repair of sealant.............................  2 work-hours x $85 per hour =               $129            $299
                                                 $170.
Insulation blanket replacement................  24 work-hours x $85 per hour =             6,312           8,352
                                                 $2,040.
Leak checks...................................  6 work-hours x $85 per hour =                  0             510
                                                 $510.
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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 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 
regulation:
    (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 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

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 (AD):

The Boeing Company: Docket No. FAA-2020-0331; Product Identifier 
2020-NM-019-AD.

(a) Comments Due Date

    The FAA must receive comments by June 22, 2020.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-600, -700, -
700C, -800, -900, and -900ER series airplanes, certificated in any 
category, line numbers 1 through 1934 inclusive.

(d) Subject

    Air Transport Association (ATA) of America Code 28, Fuel.

(e) Unsafe Condition

    This AD was prompted by a report that sealant was not applied to 
the side of body (SOB) slot inside of a pressurized boundary, which 
could lead to inconsistent application of the required secondary 
fuel barrier sealant (vapor barrier). The FAA is issuing this AD to 
address possible ignition of flammable fluid vapors, fire, or 
explosion, or fuel vapor inhalation by passengers and crew.

(f) Compliance

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

(g) Inspection Definition

    For the purposes of this AD, a general visual inspection is 
defined as: ``A visual examination of an interior or exterior area, 
installation, or assembly to detect obvious damage, failure, or 
irregularity. This level of inspection is made from within touching 
distance unless otherwise specified. A mirror may be necessary to 
enhance visual access to all exposed surfaces in the inspection 
area. This level of inspection is made under normally available 
lighting conditions such as daylight, hangar lighting, flashlight, 
or droplight and may require removal or opening of access panels or 
doors. Stands, ladders, or platforms may be required to gain 
proximity to the area being checked.''

(h) SOB Slot Inspection and Related Investigative and Corrective 
Actions

    Within 9 months after the effective date of this AD: Do a 
general visual inspection for insufficient sealant in the SOB slot, 
and do all applicable related investigative and corrective actions, 
in accordance with Boeing Multiple Operator Message MOM-MOM-20-0049-
01B (R1), dated January 29, 2020. Do all related investigative and 
corrective actions before further flight.

(i) Deferred Repair

    Repair of insufficient sealant as required by paragraph (h) may 
be deferred for 10 days

[[Page 26896]]

provided there is no fuel present in the center tank as specified in 
the procedures in item 28-02A of the operator's existing minimum 
equipment list, and there is no fuel contamination in the ADMB.

(j) Reporting Provisions

    Although the service information referenced in Boeing Multiple 
Operator Message MOM-MOM-20-0049-01B (R1), dated January 29, 2020, 
specifies to report inspection findings, this AD does not require 
any report.

(k) 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 local Flight Standards District 
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 (l)(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 local flight standards district office/certificate holding 
district 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.

(l) Related Information

    (1) For more information about this AD, contact James Laubaugh, 
Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3622; email: [email protected].
    (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 April 23, 2020.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2020-09396 Filed 5-5-20; 8:45 am]
 BILLING CODE 4910-13-P