[Federal Register Volume 86, Number 246 (Tuesday, December 28, 2021)]
[Rules and Regulations]
[Pages 73670-73673]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-27957]


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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; 
Amendment 39-21852; AD 2021-25-09]
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 737-200 and -200C series airplanes. 
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 that the activation was caused when the 
angle of attack (AOA) (also

[[Page 73671]]

known as angle of airflow) sensor vanes froze and malfunctioned due to 
insufficient heat in certain AOA sensors to prevent ice buildup. This 
AD requires 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 issuing this AD to address the unsafe condition on 
these products.

DATES: This AD is effective February 1, 2022.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of February 1, 
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-2021-0543.

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 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: 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; 
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 737-200 and -200C series airplanes. The NPRM published in 
the Federal Register on August 9, 2021 (86 FR 43454). The NPRM 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 that the activation was caused when the AOA 
sensor vanes froze and malfunctioned due to insufficient heat in 
certain AOA sensors to prevent ice buildup. In the NPRM, the FAA 
proposed to 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 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.

Discussion of Final Airworthiness Directive

Comments

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

Request for Clarification of Affected Airplane Model

    Boeing asked that clarification be added to the Summary, 
Background, and Unsafe Condition sections of the proposed AD to specify 
that the originating AOA vane immobilization report was not on a Model 
737 airplane. Boeing stated that this would clarify the service history 
and align the text with the language used in Boeing Alert Service 
Bulletin 737-27A1324, dated March 2, 2021.
    The FAA agrees to provide clarification, here in the comment 
section instead of throughout the body of this AD. Initially, AOA vane 
immobilization was reported on a Model 717 airplane; the associated 
design issues have been addressed for that airplane model. Although no 
Model 737-200 airplane has experienced an in-flight incident related to 
the identified unsafe condition, the design of the AOA sensor vanes is 
similar on Model 737-200 airplanes. Therefore, the FAA has determined 
that this AD is necessary to address the unsafe condition on these 
airplanes. The FAA has not changed this final rule as a result of this 
comment.

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 change 
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 Alert Service Bulletin 737-27A1324, dated 
March 2, 2021. This service information specifies procedures for doing 
a general visual inspection of the left- and -right-side AOA sensor 
vane shapes, 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.

Costs of Compliance

    The FAA estimates that this AD will affect 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
----------------------------------------------------------------------------------------------------------------
Inspection............................  1 work-hour x $85 per                 $0             $85            $935
                                         hour = $85.
----------------------------------------------------------------------------------------------------------------

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

[[Page 73672]]



                                               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

    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:

2021-25-09 The Boeing Company: Amendment 39-21852; Docket No. FAA-
2021-0543; Project Identifier AD-2021-00353-T.

(a) Effective Date

    This airworthiness directive (AD) is effective February 1, 2022.

(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 that the activation was 
caused when the angle of attack (AOA) (also known as angle of 
airflow) sensor vanes froze 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.

(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: [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, 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.

[[Page 73673]]

(k) Related Information

    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; email: [email protected].

(l) 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 Alert Service Bulletin 737-27A1324, dated March 2, 
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 https://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: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on December 2, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-27957 Filed 12-27-21; 8:45 am]
BILLING CODE 4910-13-P