33576 Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Proposed Rules 

(c) Applicability 

This AD applies to The Boeing Company 

Model 777–200, –200LR, –300, and –300ER 

series airplanes, certificated in any category, 

as identified in Boeing Special Attention 

Service Bulletin 777–25–0649, Revision 2, 

dated October 8, 2020. 

(d) Subject 

Air Transport Association (ATA) of 

America Code 25, Equipment/furnishings. 

(e) Unsafe Condition 

This AD was prompted by a report that 

showed a non-compliance exists on some inservice galley attendant seat fitting 

installations, and a determination that 

additional airplanes are subject to the unsafe 

condition. The FAA is issuing this AD to 

address non-compliant flight attendant seats, 

which could fail in a high-G crash and result 

in potential injury to flight attendants and 

consequent inability of the flight attendants 

to assist with passenger evacuation in a 

timely manner. 

(f) Compliance 

Comply with this AD within the 

compliance times specified, unless already 

done. 

(g) Required Actions 

Except as specified by paragraph (h) of this 

AD: At the applicable times specified in 

paragraph 1.E., ‘‘Compliance,’’ of Boeing 

Special Attention Service Bulletin 777–25– 

0649, Revision 2, dated October 8, 2020, do 

all applicable actions identified as ‘‘RC’’ 

(required for compliance) in, and in 

accordance with, the Accomplishment 

Instructions of Boeing Special Attention 

Service Bulletin 777–25–0649, Revision 2, 

dated October 8, 2020. 

(h) Exception to Service Information 

Specifications 

Where Boeing Special Attention Service 

Bulletin 777–25–0649, Revision 2, dated 

October 8, 2020, uses the phrase ‘‘the 

Revision 2 date of this service bulletin,’’ this 

AD requires using ‘‘the effective date of this 

AD.’’ 

(i) No Reporting Requirement 

Although the service information 

referenced in Boeing Special Attention 

Service Bulletin 777–25–0649, Revision 2, 

dated October 8, 2020, specifies to submit 

certain information to the manufacturer, this 

AD does not include that requirement. 

(j) 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 Boeing Special 

Attention Service Bulletin 777–25–0649, 

Revision 1, dated October 6, 2017 (which is 

incorporated by reference in AD 2019–01– 

08). 

(k) 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 Related Information. 

Information may be emailed to: 9-ANMSeattle-ACO-AMOC-Requests@faa.gov. 

(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. 

(4) AMOCs approved for AD 2019–01–08 

are approved as AMOCs for the 

corresponding provisions of Boeing Special 

Attention Service Bulletin 777–25–0649, 

Revision 2, dated October 8, 2020, that are 

required by paragraph (g) of this AD. 

(5) For service information that contains 

steps that are labeled as Required for 

Compliance (RC), the provisions of 

paragraphs (k)(5)(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. 

(l) Related Information 

(1) For more information about this AD, 

contact Brandon Lucero, Aerospace Engineer, 

Cabin Safety and Environmental Systems 

Section, FAA, Seattle ACO Branch, 2200 

South 216th St., Des Moines, WA 98198; 

phone and fax: 206–231–3569; email: 

brandon.lucero@faa.gov. 

(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 May 28, 2021. 

Gaetano A. Sciortino, 

Deputy Director for Strategic Initiatives, 

Compliance & Airworthiness Division, 

Aircraft Certification Service. 

[FR Doc. 2021–13407 Filed 6–24–21; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2021–0502; Project 

Identifier 2018–CE–043–AD] 

RIN 2120–AA64 

Airworthiness Directives; B–N Group 

Ltd. 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 B–N Group Ltd. Models BN–2, 

BN–2A, BN–2A–2, BN–2A–3, BN–2A–6, 

BN–2A–8, BN–2A–9, BN–2A–20, BN– 

2A–21, BN–2A–26, BN–2A–27, BN–2B– 

20, BN–2B–21, BN–2B–26, BN–2B–27, 

BN–2T, and BN–2T–4R airplanes. This 

proposed AD results from mandatory 

continuing airworthiness information 

(MCAI) originated by an aviation 

authority of another country to identify 

and correct an unsafe condition on an 

aviation product. The MCAI identifies 

the unsafe condition as failure of the 

rudder final drive rod because of cracks 

in the region of the taper pins. This 

proposed AD would require repetitively 

inspecting the rudder final drive rod 

assembly and replacing the rudder final 

drive assembly, if necessary. 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 August 9, 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. 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Proposed Rules 33577 

For service information identified in 

this NPRM, contact Britten-Norman 

Aircraft Limited, Commodore House, 

Mountbatten Business Centre, Millbrook 

Road East, Southampton SO15 1HY, 

United Kingdom; phone: +44 20 3371 

4000; fax: +44 20 3371 4001; email: 

info@bnaircraft.com; website: https://

britten-norman.com/approvalstechnical-publications/. You may view 

this service information at the FAA, 

Airworthiness Products Section, 

Operational Safety Branch, 901 Locust, 

Kansas City, MO 64106. For information 

on the availability of this material at the 

FAA, call (816) 329–4148. 

Examining the AD Docket 

You may examine the AD docket at 

https://www.regulations.gov by 

searching for and locating Docket No. 

FAA–2021–0502; 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: 

Penelope Trease, Aviation Safety 

Engineer, General Aviation & Rotorcraft 

Section, International Validation 

Branch, FAA, 26805 E 68th Avenue, 

Denver, CO 80249; phone: (303) 342– 

1094; email: penelope.trease@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–2021–0502; Project Identifier 

2018–CE–043–AD’’ 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 Penelope Trease, 

Aviation Safety Engineer, General 

Aviation & Rotorcraft Section, 

International Validation Branch, FAA, 

26805 E 68th Avenue, Denver, CO 

80249. 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 European Aviation Safety Agency 

(EASA), which is the Technical Agent 

for the Member States of the European 

Union, has issued EASA AD 2018–0153, 

dated July 19, 2018 (referred to after this 

as ‘‘the MCAI’’), to correct an unsafe 

condition for B–N Group Ltd. (BrittenNorman Aircraft Ltd., or ‘‘BNA’’) 

Models BN–2, BN–2A, BN–2B, BN–2T, 

BN–2T–2, BN–2T–2R, and BN–2T–4R 

airplanes. The MCAI states: 

Occurrences have been reported of failures 

of the rudder final drive rod, [part number] 

P/N NB–45–0991. Cracks were found in the 

region of the taper pins. There is evidence 

that replacing the taper pins could be a 

significant factor contributing to the failure of 

this rod. 

This condition, if not detected and 

corrected, could lead to failure of the affected 

part, possibly resulting in reduced control of 

the aeroplane. 

To address this potential unsafe condition, 

BNA issued the applicable SB [service 

bulletin], providing inspection instructions. 

Prompted by operator comments, BNA 

revised the applicable SB (issue 3) to 

introduce repetitive inspections. 

For the reason described above, this 

[EASA] AD requires repetitive inspections of 

the affected part and, depending on findings, 

replacement. This AD also prohibits 

replacement of taper pins on an affected part. 

BNA will amend the applicable Maintenance 

Manuals accordingly. 

You may examine the MCAI in the 

AD docket at https://

www.regulations.gov by searching for 

and locating Docket No. FAA–2021– 

0502. 

Related Service Information Under 1 

CFR Part 51 

The FAA reviewed Britten-Norman 

Aircraft Limited Service Bulletin 

Number SB 363, Issue 3, dated May 23, 

2018, and Service Bulletin Number SB 

364, Issue 3, dated May 23, 2018. For 

the applicable airplane models 

identified on each document, this 

service information contains procedures 

for repetitively inspecting the rudder 

final drive rod assembly and replacing 

the rudder final drive assembly, if 

necessary. 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. 

FAA’s Determination 

This product has been approved by 

the aviation authority of another 

country and is approved for operation in 

the United States. Pursuant to our 

bilateral agreement with this State of 

Design Authority, it has notified the 

FAA of the unsafe condition described 

in the MCAI and service information 

referenced above. The FAA is issuing 

this NPRM after determining the unsafe 

condition described previously is likely 

to exist or develop on other products of 

the same type design. 

Proposed AD Requirements in This 

NPRM 

This AD requires accomplishing the 

actions specified in the service 

information already described. 

Costs of Compliance 

The FAA estimates that this AD, if 

adopted as proposed, would affect 76 

airplanes of U.S. registry. The FAA also 

estimates that inspecting the rudder 

final drive assembly would take about 1 

work-hour at the average labor rate of 

$85 per work-hour. 

Based on these figures, the FAA 

estimates the cost of this proposed AD 

on U.S. operators to be $6,460, or $85 

per product, each inspection cycle. 

In addition, the FAA estimates that 

any necessary follow-on actions to 

replace the rudder final drive assembly 

would take about 5 work-hours and 

require parts costing $1,200, for a cost 

of $1,625 per product. The FAA has no 

way of determining the number of 

airplanes that may need these actions. 

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 


lotter on DSK11XQN23PROD with PROPOSALS1
33578 Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Proposed Rules 

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: 

B–N Group Ltd.: Docket No. FAA–2021– 

0502; Project Identifier 2018–CE–043– 

AD. 

(a) Comments Due Date 

The FAA must receive comments on this 

airworthiness directive (AD) by August 9, 

2021. 

(b) Affected ADs 

None. 

(c) Applicability 

This AD applies to B–N Group Ltd. Models 

BN–2, BN–2A, BN–2A–2, BN–2A–3, BN–2A– 

6, BN–2A–8, BN–2A–9, BN–2A–20, BN–2A– 

21, BN–2A–26, BN–2A–27, BN–2B–20, BN– 

2B–21, BN–2B–26, BN–2B–27, BN–2T, and 

BN–2T–4R airplanes, all serial numbers, 

certificated in any category, with a rudder 

final drive rod part number (P/N) NB–45– 

0991 installed. 

(d) Subject 

Joint Aircraft System Component (JASC) 

Code 2720, Rudder Control System. 

(e) Unsafe Condition 

This AD was prompted by mandatory 

continuing airworthiness information (MCAI) 

originated by an aviation authority of another 

country to identify and correct an unsafe 

condition on an aviation product. The MCAI 

describes the unsafe condition as failure of 

the rudder final drive rod because of cracks 

in the region of the taper pins. The FAA is 

issuing this AD to detect and correct defects 

on the rudder final drive rod assembly to 

prevent failure of the assembly. The unsafe 

condition, if not addressed, could result in 

loss of rudder control and reduced airplane 

control. 

(f) Compliance 

Comply with this AD within the 

compliance times specified, unless already 

done. 

(g) Inspection and Corrective Action 

(1) Inspect the rudder final drive rod 

assembly for loose taper pins, loose end 

connections, bending, and cracks within the 

applicable compliance times for your 

airplane specified in paragraph (g)(1)(i) or (ii) 

of this AD. 

(i) For Models BN–2, BN–2A, BN–2A–2, 

BN–2A–3, BN–2A–6, BN–2A–8, BN–2A–9, 

BN–2A–20, BN–2A–21, BN–2A–26, BN–2A– 

27, BN–2B–20, BN–2B–21, BN–2B–26, and 

BN–2B–27 airplanes, within 100 hours timein-service (TIS) after the effective date of this 

AD and thereafter at intervals not to exceed 

1,000 hours TIS. 

(ii) For Models BN–2T and BN–2T–4R 

airplanes, within 200 hours TIS after the 

effective date of this AD and thereafter at 

intervals not to exceed 1,000 hours TIS. 

(2) If a loose taper pin, a loose end 

connection, any bending, or a crack is found 

during any inspection required by paragraph 

(g)(1) of this AD, before further flight, replace 

the rudder final drive rod assembly by 

following section 7, Removal and Installation 

Instructions for Unserviceable Units, of 

Britten-Norman Service Bulletin Number SB 

363, Issue 3, dated May 23, 2018 (SB 363, 

Issue 3) or Britten-Norman Service Bulletin 

Number SB 364, Issue 3, dated May 23, 2018 

(SB 364, Issue 3), as applicable to your model 

airplane. 

(3) If no loose taper pins, no loose end 

connections, no bending, and no cracks are 

found during the initial inspection required 

by paragraph (g)(1) of this AD, review the 

airplane maintenance records to determine 

whether any taper pins have been replaced 

or reworked on the rudder final drive rod 

assembly. 

(4) If a taper pin has ever been replaced or 

reworked, without exceeding the initial 

compliance time in paragraph (g)(1)(i) or (ii) 

of this AD, replace the rudder final drive rod 

assembly by following section 7, Removal 

and Installation Instructions for 

Unserviceable Units, of SB 363, Issue 3 or SB 

364, Issue 3, as applicable to your model 

airplane. 

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

not install a rudder final drive rod assembly 

P/N NB–45–0991 on any airplane unless: 

(i) The rudder final drive rod assembly is 

unused (zero hours TIS); or 

(ii) The taper pins in the rudder final drive 

rod assembly have never been replaced. 

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

not replace any taper pin on a rudder final 

drive rod assembly P/N NB–45–0991 

installed on any airplane. 

(h) 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 certification office, 

send it to the attention of the person 

identified in Related Information or email: 9- 

AVS-AIR-730-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. 

(i) Related Information 

(1) For more information about this AD, 

contact Penelope Trease, Aviation Safety 

Engineer, General Aviation & Rotorcraft 

Section, International Validation Branch, 

FAA, 26805 E 68th Avenue, Denver, CO 

80249; phone: (303) 342–1094; email: 

penelope.trease@faa.gov. 

(2) Refer to European Aviation Safety 

Agency (EASA) AD 2018–0153, dated July 

19, 2018, for more information. You may 

examine the EASA AD in the AD docket at 

https://www.regulations.gov by searching for 

and locating it in Docket No. FAA–2021– 

0502. 

(3) For service information identified in 

this AD, contact Britten-Norman Aircraft 

Limited, Commodore House, Mountbatten 

Business Centre, Millbrook Road East, 

Southampton SO15 1HY, United Kingdom; 

phone: +44 20 3371 4000; fax: +44 20 3371 

4001; email: info@bnaircraft.com; website: 

https://britten-norman.com/approvalstechnical-publications/. You may review this 

referenced service information at the FAA, 

Airworthiness Products Section, Operational 

Safety Branch, 901 Locust, Kansas City, MO 


lotter on DSK11XQN23PROD with PROPOSALS1
Federal Register / Vol. 86, No. 120 / Friday, June 25, 2021 / Proposed Rules 33579 

64106. For information on the availability of 

this material at the FAA, call (816) 329–4148. 

Issued on June 11, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–13463 Filed 6–24–21; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2021–0511; Project 

Identifier AD–2020–01229–E] 

RIN 2120–AA64 

Airworthiness Directives; Williams 

International Co., L.L.C. Turbofan 

Engines 

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 Williams International Co., 

L.L.C. (Williams) FJ44–2A, FJ44–2C, 

FJ44–3A, and FJ44–3A–24 model 

turbofan engines. This proposed AD was 

prompted by a report of cracks in highpressure turbine (HPT) disk posts and 

failure of an HPT disk post. This 

proposed AD would require the removal 

and replacement of the affected HPT 

disk before reaching its new life limit. 

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 August 9, 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 Williams 

International Co., L.L.C., Product 

Support, 2000 Centerpoint Pkwy., 

Pontiac, MI 48341; phone: (800) 859– 

3544; website: http://www.williamsint.com/product-support. You may view 

this service information at the Chicago 

ACO Branch, 2300 East Devon Avenue, 

Des Plaines, IL 60018. For information 

on the availability of this material at the 

FAA, call (781) 238–7759. 

Examining the AD Docket 

You may examine the AD docket at 

https://www.regulations.gov by 

searching for and locating Docket No. 

FAA–2021–0511; 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: Kyle 

Bush, Aviation Safety Engineer, Chicago 

ACO Branch, FAA, 2300 East Devon 

Avenue, Des Plaines, IL 60018; phone: 

(847) 294–7870; fax: (847) 294–7834; 

email: kyle.bush@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–2021–0511; Project Identifier AD– 

2020–01229–E’’ 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 Kyle Bush, Aviation 

Safety Engineer, Chicago ACO Branch, 

FAA, 2300 East Devon Avenue, Des 

Plaines, IL 60018. 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 received a report that 

Williams discovered cracks in one HPT 

disk post during a scheduled inspection 

of an FJ44–2A model turbofan engine. 

An operator also discovered that one 

HPT disk post failed, while the engine 

was in service, resulting in the release 

of an HPT blade. 

Williams initiated an investigation to 

understand the root cause of the cracks 

and to determine the necessary 

corrective action. Williams found that, 

between August 2018 and July 2019, 

nine FJ44–2A HPT disks were rejected 

during inspection after discovery of 

cracks in the HPT disk post. As part of 

its investigation, Williams conducted 

several tests and analysis to determine 

the failure mechanism. Engine tests 

confirmed that FJ44–2A and FJ44–2C 

model turbofan engines operate at a 

higher temperature than most recently 

certified engines. Metallurgical 

evaluation showed cracking is intergranular with oxidation attack near and 

around the crack, with no fatigue 

striations. Metallurgical evaluation and 

comparison of HPT disk, part number 

(P/N) 67093, installed on both FJ44–2A 

and FJ44–3A model turbofan engines, 

showed cracking of the HPT disk. 

As a result of this investigation, 

Williams determined the root cause of 

this cracking was due to higher 

temperatures and a difference in 

manufacturing processes (electrical 

discharge machining vs. broaching). 

Williams determined that these cracks 

have only occurred on HPT disks with 

P/N 67093. Williams subsequently 

issued service information to instruct 

operators to remove the HPT disk, P/N 

67093. This condition, if not addressed, 

could result in failure of the engine, inflight shutdown of the engine, and loss 

of control of the aircraft. 

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. 


lotter on DSK11XQN23PROD with PROPOSALS1