Federal Register / Vol. 86, No. 150 / Monday, August 9, 2021 / Proposed Rules 43451 

(c) Applicability 

This AD applies to He ́licopte`res Guimbal 

(HG) Model Cabri G2 helicopters, certificated 

in any category, the following aluminum 

cooling fan (cooling fan) part number (P/N) 

installed: 

(1) P/N G52–00–000, 

(2) P/N G52–00–001 or P/N G52–04–100, if 

it is or has previously been mounted on a 12- 

hole engine pulley P/N G52–10–100 or P/N 

G52–10–101. 

(d) Subject 

Joint Aircraft Service Component (JASC) 

Code: 7100, Powerplant System. 

(e) Unsafe Condition 

This AD was prompted by reports of inflight engine shutdowns due to a crack and 

subsequent failure of the cooling fan. The 

FAA is issuing this AD to prevent failure of 

the cooling fan. This condition, if not 

addressed, could result in an in-flight engine 

shut-down and loss of control of the 

helicopter. 

(f) Compliance 

Comply with this AD within the 

compliance times specified, unless already 

done. 

(g) Required Actions 

(1) For Model Cabri G2 helicopters with 

cooling fan P/N G52–00–000 installed, 

within 150 hours time-in-service (TIS) after 

the effective date of this AD: 

(i) Remove the cooling fan from service by 

following the Required Actions, Cooling Fan 

Removal, paragraphs (a) through (g), of 

Guimbal Service Bulletin SB 16–021, 

Revision E, dated August 27, 2019 (SB 16– 

021 Rev E), except you are not required to 

discard any parts. 

(ii) Install the improved cooling fan P/N 

G52–04–101 by following the Required 

Actions, Cooling Fan Installation, paragraphs 

(a) through (j), of SB 16–021 Rev E. 

(2) For Model Cabri G2 helicopters with a 

cooling fan P/N G52–00–001 or P/N G52–04– 

100 that is mounted or was previously 

mounted on a 12-hole engine pulley P/N 

G52–10–100 or P/N G52–10–101, and with 

1,500 or more total hours TIS, since first 

installation on a helicopter, within 150 hours 

TIS after the effective date of this AD: 

(i) Remove the cooling fan from service by 

following the Required Actions, Cooling Fan 

Removal, paragraphs (a) through (g), of SB 

16–021 Rev E, except you are not required to 

discard any parts, or remove the cooling fan 

by following the Required Actions, Cooling 

Fan Removal, paragraphs (a) through (g), of 

SB 16–021 Rev E and modify the cooling fan 

by following the Required Actions, Cooling 

Fan Retrofit, paragraphs (a) through (h) of SB 

16–021 Rev E. 

(ii) Install the improved cooling fan P/N 

G52–04–101 by following the Required 

Actions, Cooling Fan Installation, paragraphs 

(a) through (j), of SB 16–021 Rev E. 

(3) For Model Cabri G2 helicopters with a 

cooling fan P/N G52–00–001 or P/N G52–04– 

100 that is mounted or was previously 

mounted on a 12-hole engine pulley P/N 

G52–10–100 or P/N G52–10–101 and with 

500 total hours TIS but with less than 1,500 

total hours TIS, since first installation on a 

helicopter, within 500 hours TIS after the 

effective date of this AD, perform the actions 

required by paragraphs (g)(2)(i) and (ii) of 

this AD. 

(4) For Model Cabri G2 helicopters with a 

cooling fan P/N G52–00–001 or P/N G52–04– 

100 that is mounted or was previously 

mounted on a 12-hole engine pulley P/N 

G52–10–100 or P/N G52–10–101 and with 

less than 500 total hours TIS since first 

installation on a helicopter, within 1,000 

hours TIS after the effective date of this AD, 

perform the actions required by paragraphs 

(g)(2)(i) and (ii) of this AD. 

(5) As of the effective date of this AD, do 

not install any cooling fan listed in paragraph 

(c) of this AD on any helicopter. 

(h) Credit for Previous Actions 

This paragraph provides credit for the 

actions specified in paragraph (g) of this AD, 

if those actions were performed before the 

effective date of this AD using Guimbal 

Service Bulletin SB 16–021, Revision D, 

dated May 20, 2019. 

(i) Alternative Methods of Compliance 

(AMOCs) 

(1) The Manager, International Validation 

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 International Validation 

Branch, send it to the attention of the person 

identified in paragraph (j)(1) of this AD. 

Information may be emailed to: 9-AVS-AIR730-AMOC@faa.gov. 

(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. 

(j) Related Information 

(1) For more information about this AD, 

contact Andrea Jimenez, Aerospace Engineer, 

COS Program Management Section, 

Operational Safety Branch, Compliance & 

Airworthiness Division, FAA, 1600 Stewart 

Ave., Suite 410, Westbury, NY 11590; 

telephone (516) 228–7330; email 

andrea.jimenez@faa.gov. 

(2) For service information identified in 

this AD, contact He ́licopte`res Guimbal, Basile 

Ginel, 1070, rue du Lieutenant Parayre, 

Ae ́rodrome d’Aix-en-Provence, 13290 Les 

Milles, France; telephone 33–04–42–39–10– 

88; email basile.ginel@guimbal.com; web 

https://www.guimbal.com. You may view 

this referenced service information at the 

FAA, Office of the Regional Counsel, 

Southwest Region, 10101 Hillwood Pkwy., 

Room 6N–321, Fort Worth, TX 76177. For 

information on the availability of this 

material at the FAA, call (817) 222–5110. 

(3) The subject of this AD is addressed in 

European Union Aviation Safety Agency 

(EASA) AD 2019–0187, dated July 31, 2019 

and corrected August 2, 2019. You may view 

the EASA AD on the internet at https://

www.regulations.gov in Docket No. FAA– 

2021–0620. 

Issued on July 30, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–16684 Filed 8–6–21; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2021–0616; Project 

Identifier MCAI–2021–00256–T] 

RIN 2120–AA64 

Airworthiness Directives; Saab AB, 

Support and Services (Formerly 

Known as Saab AB, Saab Aeronautics) 

Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Notice of proposed rulemaking 

(NPRM). 

SUMMARY: The FAA proposes to adopt a 

new airworthiness directive (AD) for 

certain Saab AB, Support and Services 

Model SAAB 340B airplanes. This 

proposed AD was prompted by a report 

that the circuit breaker for the 

emergency cabin lighting tripped 

without fault in the system. This 

proposed AD would require replacing a 

certain circuit breaker with a part 

having a higher rating, as specified in a 

European Union Aviation Safety Agency 

(EASA) AD, which is proposed for 

incorporation by reference. 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: 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 material that will be incorporated 

by reference (IBR) in this AD, contact 

EASA, Konrad-Adenauer-Ufer 3, 50668 

Cologne, Germany; telephone +49 221 

8999 000; email ADs@easa.europa.eu; 


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internet www.easa.europa.eu. You may 

find this IBR material on the EASA 

website at https://ad.easa.europa.eu. 

You may view this IBR material 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 in the AD docket on 

the internet at https://

www.regulations.gov by searching for 

and locating Docket No. FAA–2021– 

0616. 

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–2021– 

0616; 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: 

Shahram Daneshmandi, Aerospace 

Engineer, Large Aircraft Section, 

International Validation Branch, FAA, 

2200 South 216th St., Des Moines, WA 

98198; telephone and fax 206–231– 

3220; email shahram.daneshmandi@

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. 

FAA–2021–0616; Project Identifier 

MCAI–2021–00256–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 the 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 proposed 

AD. 

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 Shahram 

Daneshmandi, Aerospace Engineer, 

Large Aircraft Section, International 

Validation Branch, FAA, 2200 South 

216th St., Des Moines, WA 98198; 

telephone and fax 206–231–3220; email 

shahram.daneshmandi@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 

EASA, which is the Technical Agent 

for the Member States of the European 

Union, has issued EASA AD 2021–0058, 

dated March 1, 2021 (EASA AD 2021– 

0058) (also referred to as the Mandatory 

Continuing Airworthiness Information, 

or the MCAI), to correct an unsafe 

condition for certain Saab AB, Support 

and Services Model SAAB 340B 

airplanes. 

This proposed AD was prompted by 

a report that the 2LN circuit breaker for 

the emergency cabin lighting on a SAAB 

340B airplane tripped without fault in 

the system. Investigation results found 

that the circuit breaker 2LN has too low 

a rating (5A) for maximum charging 

conditions. The FAA is proposing this 

AD to address the low rating of the 2LN 

circuit breaker during maximum 

charging conditions. This condition, if 

not corrected, could lead to an 

insufficiently charged emergency 

battery, with consequent loss of cabin 

emergency lighting, possibly resulting 

in injury to occupants during an 

evacuation. See the MCAI for additional 

background information. 

Related Service Information Under 1 

CFR Part 51 

EASA AD 2021–0058 describes 

procedures for replacing the 2LN circuit 

breaker having a rating of 5A with a new 

breaker having a current rating of 7.5A. 

This material 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 and Requirements 

of This Proposed AD 

This product has been approved by 

the aviation authority of another 

country, and is approved for operation 

in the United States. Pursuant to the 

FAA’s bilateral agreement with the State 

of Design Authority, the FAA has been 

notified of the unsafe condition 

described in the MCAI referenced 

above. 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 

EASA AD 2021–0058 described 

previously, as incorporated by 

reference, except for any differences 

identified as exceptions in the 

regulatory text of this AD. 

Explanation of Required Compliance 

Information 

In the FAA’s ongoing efforts to 

improve the efficiency of the AD 

process, the FAA developed a process to 

use certain civil aviation authority 

(CAA) ADs as the primary source of 

information for compliance with 

requirements for corresponding FAA 

ADs. The FAA has been coordinating 

this process with manufacturers and 

CAAs. As a result, EASA AD 2021–0058 

will be incorporated by reference in the 

FAA final rule. This proposed AD 

would, therefore, require compliance 

with EASA AD 2021–0058 in its 

entirety, through that incorporation, 

except for any differences identified as 

exceptions in the regulatory text of this 

proposed AD. Using common terms that 

are the same as the heading of a 

particular section in EASA AD 2021– 

0058 does not mean that operators need 

comply only with that section. For 

example, where the AD requirement 

refers to ‘‘all required actions and 

compliance times,’’ compliance with 

this AD requirement is not limited to 

the section titled ‘‘Required Action(s) 

and Compliance Time(s)’’ in EASA AD 

2021–0058. Service information 

specified in EASA AD 2021–0058 that is 

required for compliance with it will be 

available at https://www.regulations.gov 

by searching for and locating Docket No. 

FAA–2021–0616 after the FAA final 

rule is published. 


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Costs of Compliance 

The FAA estimates that this proposed 

AD affects 27 airplanes of U.S. registry. 

The FAA estimates the following costs 

to comply with this proposed AD: 

ESTIMATED COSTS FOR REQUIRED ACTIONS

Labor cost Parts cost Cost per 

product 

Cost on U.S. 

operators 

1 work-hour × $85 per hour = $85 .............................................................................................. $50 $135 $3,645

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 

■ 1. The authority citation for part 39 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701. 

§ 39.13 [Amended] 

■ 2. The FAA amends § 39.13 by adding 

the following new airworthiness 

directive: 

Saab AB, Support and Services (Formerly 

Known as Saab AB, Saab Aeronautics): 

Docket No. FAA–2021–0616; Project 

Identifier MCAI–2021–00256–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 Saab AB, Support and 

Services (Formerly Known as Saab AB, Saab 

Aeronautics) Model SAAB 340B airplanes, 

certificated in any category, as identified in 

European Union Aviation Safety Agency 

(EASA) AD 2021–0058, dated March 1, 2021 

(EASA AD 2021–0058). 

(d) Subject 

Air Transport Association (ATA) of 

America Code 33, Lights. 

(e) Reason 

This AD was prompted by a report that the 

circuit breaker for the emergency cabin 

lighting tripped without fault in the system. 

The FAA is issuing this AD to address the 

low rating of the 2LN circuit breaker during 

maximum charging conditions. This 

condition, if not corrected, could lead to an 

insufficiently charged emergency battery, 

with consequent loss of cabin emergency 

lighting, possibly resulting in injury to 

occupants during an evacuation. 

(f) Compliance 

Comply with this AD within the 

compliance times specified, unless already 

done. 

(g) Requirements 

Except as specified in paragraph (h) of this 

AD: Comply with all required actions and 

compliance times specified in, and in 

accordance with, EASA AD 2021–0058. 

(h) Exceptions to EASA AD 2021–0058 

(1) Where EASA AD 2021–0058 refers to its 

effective date, this AD requires using the 

effective date of this AD. 

(2) The ‘‘Remarks’’ section of EASA AD 

2021–0058 does not apply to this AD. 

(i) Other FAA AD Provisions 

The following provisions also apply to this 

AD: 

(1) Alternative Methods of Compliance 

(AMOCs): The Manager, Large Aircraft 

Section, International Validation 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 Large Aircraft 

Section, International Validation Branch, 

send it to the attention of the person 

identified in paragraph (j)(2) of this AD. 

Information may be emailed to: 9-AVS-AIR730-AMOC@faa.gov. Before using any 

approved AMOC, notify your appropriate 

principal inspector, or lacking a principal 

inspector, the manager of the responsible 

Flight Standards Office. 

(2) Contacting the Manufacturer: For any 

requirement in this AD to obtain instructions 

from a manufacturer, the instructions must 

be accomplished using a method approved 

by the Manager, Large Aircraft Section, 

International Validation Branch, FAA; or 

EASA; or Saab AB, Support and Services’ 

EASA Design Organization Approval (DOA). 

If approved by the DOA, the approval must 

include the DOA-authorized signature. 

(j) Related Information 

(1) For information about EASA AD 2021– 

0058 contact EASA, Konrad-Adenauer-Ufer 

3, 50668 Cologne, Germany; telephone +49 

221 8999 000; email ADs@easa.europa.eu; 

internet www.easa.europa.eu. You may find 

this EASA AD on the EASA website at 

https://ad.easa.europa.eu. You may view this 

material 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. This 

material may be found in the AD docket on 

the internet at https://www.regulations.gov 

by searching for and locating Docket No. 

FAA–2021–0616. 

(2) For more information about this AD, 

contact Shahram Daneshmandi, Aerospace 

Engineer, Large Aircraft Section, 


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43454 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 206–231–3220; email 

shahram.daneshmandi@faa.gov. 

Issued on July 29, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–16558 Filed 8–6–21; 8:45 am] 

BILLING CODE 4910–13–P 

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). 

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: 

• 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 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: 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. 

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: 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 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 


lotter on DSK11XQN23PROD with PROPOSALS1