[Federal Register Volume 86, Number 150 (Monday, August 9, 2021)]
[Proposed Rules]
[Pages 43454-43456]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-16679]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0543; Project Identifier AD-2021-00353-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 737-200 and -200C series 
airplanes. This proposed AD was prompted by reports of nuisance stick 
shaker activation while the airplane was accelerating to cruise speed 
at the top of a climb. Investigation revealed the cause of the 
activation was the angle of attack (AOA) (also known as angle of 
airflow) sensor vanes had frozen and malfunctioned due to insufficient 
heat in certain AOA sensors to prevent ice buildup. This proposed AD 
would require inspecting the AOA sensors for certain part numbers or 
vane shapes, and replacing any affected AOA sensor with a new or 
serviceable sensor. 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 September 
23, 2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
    <bullet> Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the instructions for submitting comments.
    <bullet> Fax: 202-493-2251.
    <bullet> 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.
    <bullet> 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 by searching for and locating Docket No. FAA-2021-
0543.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0543; 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: Jeffrey W. Palmer, Aerospace Engineer, 
Systems and Equipment Section, FAA, Los Angeles ACO Branch, 3960 
Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5351; fax: 
562-627-5210; email: <a href="/cdn-cgi/l/email-protection#573d32313125322e79207927363b3a32251731363679303821"><span class="__cf_email__" data-cfemail="f9939c9f9f8b9c80d78ed7899895949c8bb99f9898d79e968f">[email protected]</span></a>.

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-2021-0543; Project Identifier 
AD-2021-00353-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 
Jeffrey W. Palmer, Aerospace Engineer, Systems and Equipment Section, 
FAA, Los Angeles ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 
90712-4137; phone: 562-627-5351; fax: 562-627-5210; email: 
<a href="/cdn-cgi/l/email-protection#d6bcb3b0b0a4b3aff8a1f8a6b7babbb3a496b0b7b7f8b1b9a0"><span class="__cf_email__" data-cfemail="c0aaa5a6a6b2a5b9eeb7eeb0a1acada5b280a6a1a1eea7afb6">[email protected]</span></a>. Any commentary that the FAA receives which is 
not specifically designated as CBI will be placed in the public docket 
for this rulemaking.

Background

    The FAA has received reports of nuisance stick shaker activation 
while the airplane was accelerating to cruise speed at the top of a 
climb. Investigation revealed the cause of the activation was the AOA 
sensor vanes had frozen and malfunctioned due to insufficient heat in 
certain AOA sensors to prevent ice buildup. This condition could be 
caused by heavy moisture conditions on the ground, leading to water 
entering the AOA vane pivot and freezing prior to or during flight. It 
was determined that the potential for AOA vane pivot freezing exists on 
certain AOA sensors having part numbers used on Model 737-200 
airplanes. This condition, if not addressed, could result in the AOA 
sensor vanes being immobilized, which could result in unreliable or 
inaccurate AOA sensor data being transmitted to airplane systems, and 
consequent loss of control of the airplane.

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 Alert Service Bulletin 737-27A1324, dated

[[Page 43455]]

March 2, 2021. This service information specifies procedures for doing 
a general visual inspection of the left and right side AOA sensor vane 
shape, or inspecting the left and right AOA sensors to determine the 
part number, and replacing any affected AOA sensor with a new or 
serviceable sensor.
    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 identified 
as ``RC'' (required for compliance) in the Accomplishment Instructions 
of Boeing Alert Service Bulletin 737-27A1324, dated March 2, 2021, 
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-2021-0543.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 11 airplanes of U.S. registry. The FAA estimates the following 
costs to comply with this proposed AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Inspection............................  1 work-hour x $85 per                 $0             $85            $935
                                         hour = $85.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary 
replacements 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 replacements:

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replacement...................................  3 work-hours x $85 per hour =            $54,000         $54,255
                                                 $255.
----------------------------------------------------------------------------------------------------------------

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-2021-0543; Project Identifier AD-
2021-00353-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by September 23, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to The Boeing Company Model 737-200 and -200C 
series airplanes, certificated in any category, as identified in 
Boeing Alert Service Bulletin 737-27A1324, dated March 2, 2021.

(d) Subject

    Air Transport Association (ATA) of America Code 27, Flight 
Control System.

(e) Unsafe Condition

    This AD was prompted by reports of nuisance stick shaker 
activation while the airplane was accelerating to cruise speed at 
the top of a climb. Investigation revealed the cause of the 
activation was the angle of attack (AOA) (also known as angle of 
airflow) sensor vanes had frozen and malfunctioned due to 
insufficient heat in certain AOA sensors to prevent ice buildup. The 
FAA is issuing this AD to prevent the AOA sensor vanes from being 
immobilized, which could result in unreliable or inaccurate AOA 
sensor data being transmitted to airplane systems, and consequent 
loss of control of the airplane.

[[Page 43456]]

(f) Compliance

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

(g) Required Actions for Group 2 Airplanes

    For airplanes identified as Group 2 in Boeing Alert Service 
Bulletin 737-27A1324, dated March 2, 2021: Within 120 days after the 
effective date of this AD, inspect the AOA sensor, using a method 
approved in accordance with the procedures specified in paragraph 
(j) of this AD.

(h) Required Actions for Group 1 Airplanes

    Except as specified in paragraph (i) of this AD: At the 
applicable times specified in paragraph 1.E., ``Compliance,'' of 
Boeing Alert Service Bulletin 737-27A1324, dated March 2, 2021, do 
all applicable actions identified as ``RC'' (required for 
compliance) in, and in accordance with, the Accomplishment 
Instructions of Boeing Alert Service Bulletin 737-27A1324, dated 
March 2, 2021.

(i) Exception to Service Information Specifications

    Where Boeing Alert Service Bulletin 737-27A1324, dated March 2, 
2021, uses the phrase ``the original issue date of this service 
bulletin,'' this AD requires using ``the effective date of this 
AD.''

(j) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, Los Angeles 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 Related Information. Information may be 
emailed to: <a href="/cdn-cgi/l/email-protection#c5fce8848b88e8898484868ae884888a86e897a0b4b0a0b6b1b685a3a4a4eba2aab3"><span class="__cf_email__" data-cfemail="d6effb97989bfb9a97979599fb979b9995fb84b3a7a3b3a5a2a596b0b7b7f8b1b9a0">[email protected]</span></a>.
    (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, Los 
Angeles 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.
    (4) For service information that contains steps that are labeled 
as Required for Compliance (RC), the provisions of paragraphs 
(j)(4)(i) and (ii) of this AD apply.
    (i) The steps labeled as RC, including substeps under an RC step 
and any figures identified in an RC step, must be done to comply 
with the AD. If a step or substep is labeled ``RC Exempt,'' then the 
RC requirement is removed from that step or substep. An AMOC is 
required for any deviations to RC steps, including substeps and 
identified figures.
    (ii) Steps not labeled as RC may be deviated from using accepted 
methods in accordance with the operator's maintenance or inspection 
program without obtaining approval of an AMOC, provided the RC 
steps, including substeps and identified figures, can still be done 
as specified, and the airplane can be put back in an airworthy 
condition.

(k) Related Information

    (1) For more information about this AD, contact Jeffrey W. 
Palmer, Aerospace Engineer, Systems and Equipment Section, FAA, Los 
Angeles ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-
4137; phone: 562-627-5351; fax: 562-627-5210; email: 
<a href="/cdn-cgi/l/email-protection#d9b3bcbfbfabbca0f7aef7a9b8b5b4bcab99bfb8b8f7beb6af"><span class="__cf_email__" data-cfemail="a0cac5c6c6d2c5d98ed78ed0c1cccdc5d2e0c6c1c18ec7cfd6">[email protected]</span></a>.
    (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 June 28, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-16679 Filed 8-6-21; 8:45 am]
BILLING CODE 4910-13-P


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