[Federal Register Volume 87, Number 227 (Monday, November 28, 2022)]
[Proposed Rules]
[Pages 72902-72904]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-25722]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1063; Project Identifier AD-2021-01339-T]
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 737-8, 737-9, and 737-8200 
airplanes. This proposed AD was prompted by a determination that a new 
airworthiness limitation is necessary to require periodic replacement 
of the oxygen sensor of the nitrogen generation system (NGS). This 
proposed AD would require revising the existing maintenance or 
inspection program, as applicable, to incorporate the new airworthiness 
limitation. 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 January 12, 
2023.

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 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., 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.

Examining the AD Docket

    You may examine the AD docket at regulations.gov by searching for 
and locating Docket No. FAA-2022-1063; 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: 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:

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. FAA-2022-1063; Project Identifier 
AD-2021-01339-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 
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 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]. Any commentary that the FAA 
receives that is not specifically designated as CBI will be placed in 
the public docket for this rulemaking.

Background

    This proposed AD was prompted by the discovery of a safety issue 
related to the reliability of the oxygen sensor of the airplane's NGS.
    The NGS is an onboard inert gas system that reduces the 
flammability of the airplane's center fuel tank. The NGS uses an air 
separation module (ASM) to separate oxygen and nitrogen from the air. 
The ASM uses input from an oxygen sensor. After the ASM separates the 
oxygen-enriched air from the nitrogen-enriched air, the NGS returns 
nitrogen-enriched air to the fuel tank, and vents the oxygen-enriched 
air overboard. These actions reduce the flammability of the fuel tank.
    Boeing discovered that the oxygen sensor's reliability can degrade 
over time. Degraded performance by the sensor could result in the ASM 
failing to produce nitrogen-enriched air, and the fuel tank becoming 
more flammable due to excessive oxygen-enriched air. Such additional 
flammability, if coupled with an ignition source in the fuel tank, 
could lead to a fuel tank explosion. This proposed AD would require 
adding an airworthiness limitation to require periodic replacement of 
the oxygen sensor.
    This proposed AD would apply to airplanes with an original 
airworthiness certificate or original export certificate of 
airworthiness issued on or before April 1, 2021, as well as airplanes 
with line numbers 7668, 7678, and 7915. Boeing did not start delivering 
airplanes with Boeing 737-7/8/8200/9/10 Special

[[Page 72903]]

Compliance Items/Airworthiness Limitations, D626A011-9-04, dated 
January 2019, which addresses this issue, until after April 1, 2021, 
and delivered airplanes with line numbers 7668, 7678, and 7915 with an 
earlier revision of that document. The applicability in this proposed 
AD is therefore limited to airplanes that were delivered with a version 
of Boeing 737-7/8/8200/9/10 Special Compliance Items/Airworthiness 
Limitations, D626A011-9-04 dated prior to January 2019.

FAA's 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.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Boeing 737-7/8/8200/9/10 Special Compliance Items/
Airworthiness Limitations, D626A011-9-04, dated January 2019. This 
service information describes, among other airworthiness limitations 
(AWLs), airworthiness limitation instruction (ALI) AWL No. 47-AWL-09, 
``Nitrogen Generation System--Oxygen Sensor,'' for replacing oxygen 
sensors. 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.

Proposed AD Requirements in This NPRM

    This proposed AD would require revising the existing maintenance or 
inspection program, as applicable, to incorporate a new airworthiness 
limitation.
    This proposed AD would require revisions to certain operator 
maintenance documents to include new actions (replacements). Compliance 
with these actions is required by 14 CFR 91.403(c). For airplanes that 
have been previously modified, altered, or repaired in the areas 
addressed by this proposed AD, the operator may not be able to 
accomplish the actions described in the revisions. In this situation, 
to comply with 14 CFR 91.403(c), the operator must request approval for 
an alternative method of compliance according to paragraph (i) of this 
proposed AD.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 62 airplanes of U.S. registry. The FAA estimates the following 
costs to comply with this proposed AD:
    The FAA has determined that revising the existing maintenance or 
inspection program takes an average of 90 work-hours per operator, 
although the agency recognizes that this number may vary from operator 
to operator. Since operators incorporate maintenance or inspection 
program changes for their affected fleet(s), the FAA has determined 
that a per-operator estimate is more accurate than a per-airplane 
estimate. Therefore, the FAA estimates the average total cost per 
operator to be $7,650 (90 work-hours x $85 per work-hour).

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) 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 
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:

The Boeing Company: Docket No. FAA-2022-1063; Project Identifier AD-
2021-01339-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by January 12, 2023.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-8, 737-9, and 
737-8200 airplanes, certificated in any category, identified in 
paragraphs (c)(1) and (2) of this AD.
    (1) Airplanes with an original airworthiness certificate or 
original export certificate of airworthiness issued on or before 
April 1, 2021.
    (2) Airplanes with line numbers 7668, 7678, and 7915.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by significant changes made to an 
airworthiness limitation (AWL) related to the nitrogen generation 
system (NGS). The FAA is issuing this AD to prevent increasing the 
flammability exposure of the center fuel tank, which together with 
an ignition source in the fuel tank, could lead to a fuel tank 
explosion and consequent loss of the airplane.

(f) Compliance

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

(g) Maintenance or Inspection Program Revision

    Within 60 days after the effective date of this AD, revise the 
existing maintenance or inspection program, as applicable, to 
incorporate the information specified in AWL No. 47-AWL-09, 
``Nitrogen Generation System--Oxygen Sensor,'' of Boeing 737-7/8/
8200/9/10 Special Compliance Items/Airworthiness Limitations, 
D626A011-9-04, dated January 2019. The initial compliance time for 
the airworthiness limitation instruction (ALI) task is: Within 
18,000 flight

[[Page 72904]]

hours after the date of issuance of the original airworthiness 
certificate or the original export certificate of airworthiness, 
within 18,000 flight hours after the most recent replacement was 
performed as specified in AWL No. 47-AWL-09, or within 12 months 
after the effective date of this AD, whichever is latest.

(h) No Alternative Actions or Intervals

    After the existing maintenance or inspection program has been 
revised as required by paragraph (g) of this AD, no alternative 
actions (e.g., inspections) or intervals may be used unless the 
actions and intervals are approved as an alternative method of 
compliance (AMOC) in accordance with the procedures specified in 
paragraph (i) of this AD.

(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.
    (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) 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 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 August 19, 2022.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2022-25722 Filed 11-25-22; 8:45 am]
BILLING CODE 4910-13-P


