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Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Proposed Rules
International Validation Branch, FAA, 2200
South 216th St., Des Moines, WA 98198;
telephone and fax 2062313220; email shahram.daneshmandi@faa.gov.
Issued on July 29, 2021.
Lance T. Gant, Director, Compliance & Airworthiness Division, Aircraft Certification Service.
FR Doc. 202116558 Filed 8621; 8:45 am BILLING CODE 491013P

DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration 14 CFR Part 39
Docket No. FAA20210543; Project Identifier AD202100353T
RIN 2120AA64

Airworthiness Directives; The Boeing Company Airplanes Federal Aviation Administration FAA, DOT.
ACTION: Notice of proposed rulemaking NPRM.
AGENCY:

The FAA proposes to adopt a new airworthiness directive AD for certain The Boeing Company Model 737200 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:
Federal eRulemaking Portal: Go to https www.regulations.gov. Follow the instructions for submitting comments.
Fax: 2024932251.
Mail: U.S. Department of Transportation, Docket Operations, M30, West Building Ground Floor, Room W12140, 1200 New Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9 a.m. and 5

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SUMMARY:

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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 110SK57, Seal Beach, CA
907405600; telephone 5627971717;
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 206231
3195. It is also available at https
www.regulations.gov by searching for and locating Docket No. FAA2021
0543.
Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210543; 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
907124137; phone: 5626275351; fax:
5626275210; email: jeffrey.w.palmer@
faa.gov.
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.
FAA20210543; Project Identifier AD
202100353T 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.

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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 907124137;
phone: 5626275351; fax: 562627
5210; email: jeffrey.w.palmer@faa.gov.
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 737200
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.
FAAs 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 73727A1324, dated
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