31604 Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Rules and Regulations 

(j) Definitions 

(1) For the purpose of this AD, a ‘‘critical 

part’’ is an engine part listed in paragraph 

2.3.1, Table B—List of Critical Parts and the 

Accelerating Factor, of the ASB. 

(2) For the purpose of this AD, 

‘‘recalculated life’’ is the consumed life of the 

critical part using the recalculation required 

by (g)(1) of this AD. 

(3) For the purpose of this AD, where the 

ASB says the ‘‘applicable Airworthiness 

Limitation Section’’ use the following: 

(i) For affected model engines M601D–1, 

M601D–11, M601D–11NZ, M601D–2, 

M601Z: ‘‘the ALS section of GE Aviation 

Engine Maintenance Manual 0982309.’’ 

(ii) For affected model engines M601E–11, 

M601E–11S, M601E–11A, M601E–11AS, 

M601F, M601FS: ‘‘the ALS section of GE 

Aviation Engine Maintenance Manual 

0982302.’’ 

(k) Alternative Methods of Compliance 

(AMOCs) 

(1) The Manager, ECO 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. You may 

email your request to: ANE-AD-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. 

(l) Related Information 

(1) For more information about this AD, 

contact Barbara Caufield, Aviation Safety 

Engineer, ECO Branch, FAA, 1200 District 

Avenue, Burlington, MA 01803; phone: (781) 

238–7146; fax: (781) 238–7199; email: 

barbara.caufield@faa.gov. 

(2) Refer to European Union Aviation 

Safety Agency (EASA) Emergency AD 2021– 

0125–E, dated May 7, 2021, 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–2021–0499. 

(m) 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) GE Aviation Czech Alert Service 

Bulletin (ASB) ASB–M601F–72–00–00–0057 

[00], ASB–M601E–72–00–00–0106 [00], 

ASB–M601D–72–00–00–0075 [00], and ASB– 

M601Z–72–00–00–0057 [00] (single 

document; formatted as service bulletin 

identifier [revision number]), dated May 7, 

2021. 

(ii) [Reserved] 

(3) For GE Aviation Czech service 

information identified in this AD, contact GE 

Aviation Czech s.r.o., Beranovy ́ch 65, 199 00 

Praha 18, Letnany, Czech Republic; phone: 

+420 222 538 111; fax: +420 222 538 222. 

(4) You may view this service information 

at FAA, Airworthiness Products Section, 

Operational Safety Branch, 1200 District 

Avenue, Burlington, MA 01803. For 

information on the availability of this 

material at the FAA, call (781) 238–7759. 

(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: fedreg.legal@nara.gov, or go to: 

https://www.archives.gov/federal-register/cfr/ 

ibr-locations.html. 

Issued on June 10, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–12659 Filed 6–11–21; 11:15 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2020–0341; Project 

Identifier 2020–NM–017–AD; Amendment 

39–21586; AD 2021–11–24] 

RIN 2120–AA64 

Airworthiness Directives; The Boeing 

Company Airplanes 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final rule. 

SUMMARY: The FAA is adopting a new 

airworthiness directive (AD) for certain 

The Boeing Company Model 737–600, 

–700, –700C, –800, –900, and –900ER 

series airplanes. This AD was prompted 

by significant changes made to the 

airworthiness limitations (AWLs) 

related to fuel tank ignition prevention 

and the nitrogen generation system 

(NGS). This AD requires revising the 

existing maintenance or inspection 

program, as applicable, to incorporate 

the April 2019 or November 2020 

revision of the airworthiness limitations 

document. The FAA is issuing this AD 

to address the unsafe condition on these 

products. 

DATES: This AD is effective July 20, 

2021. 

The Director of the Federal Register 

approved the incorporation by reference 

of a certain publication listed in this AD 

as of July 20, 2021. 

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 on the internet at 

https://www.regulations.gov by 

searching for and locating Docket No. 

FAA–2020–0341. 

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–2020– 

0341; 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: 

Christopher Baker, Aerospace Engineer, 

Propulsion Section, FAA, Seattle ACO 

Branch, 2200 South 216th St., Des 

Moines, WA 98198; phone and fax: 206– 

231–3552; email: Christopher.R.Baker@

faa.gov. 

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 737–600, –700, –700C, –800, 

–900, and –900ER series airplanes. The 

NPRM published in the Federal 

Register on May 6, 2020 (85 FR 26888). 

The NPRM was prompted by significant 

changes made to the AWLs related to 

fuel tank ignition prevention and the 

NGS. The NPRM proposed to require 

revising the existing maintenance or 

inspection program, as applicable, to 

incorporate the April 2019 revision of 

the airworthiness limitations document. 

The FAA is issuing this AD to prevent 

the potential for ignition sources inside 

the fuel tanks and also to prevent 

increasing the flammability exposure of 

the center fuel tank caused by latent 

failures, alterations, repairs, or 

maintenance actions, which could result 

in a fuel tank explosion and consequent 

loss of an airplane. In addition, the FAA 

is issuing this AD to address the 

potential loss of engine fuel suction feed 


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capability, which could result in dual 

engine flameouts, inability to restart 

engines, and consequent forced landing 

of the airplane. 

Comments 

The FAA gave the public the 

opportunity to participate in developing 

this final rule. The following presents 

the comments received on the NPRM 

and the FAA’s response to each 

comment. 

Support for the NPRM 

The Air Line Pilots Association, 

International (ALPA), United Airlines, 

and an individual stated support for the 

NPRM. 

Request To Delay Issuance of Final 

Rule 

All Nippon Airways (ANA) requested 

that the FAA delay issuance of the final 

rule until Boeing releases the next 

revision of Boeing 737–600/700/700C/ 

800/900/900ER Special Compliance 

Items/Airworthiness Limitations, 

D626A001–9–04. The commenter 

explained that in the current revision of 

Boeing 737–600/700/700C/800/900/ 

900ER Special Compliance Items/ 

Airworthiness Limitations, D626A001– 

9–04, dated April 2019 (Boeing 

D626A001–9–04, dated April 2019), for 

Airworthiness Limitation (AWL) No. 

47–AWL–09, ‘‘Nitrogen Generation 

System—Oxygen Sensor,’’ operators 

must replace the NGS oxygen sensor 

with a new oxygen sensor because 

installation of an overhauled part is not 

approved at this time. The commenter 

stated that Boeing is working with the 

FAA to allow testing of the oxygen 

sensor using the component 

maintenance manual, and on-wing 

testing using the aircraft maintenance 

manual, and Boeing plans to revise 

AWL No. 47–AWL–09 to allow testing 

and installation of an overhauled part. 

The commenter anticipated that the 

next revision of Boeing 737–600/700/ 

700C/800/900/900ER Special 

Compliance Items/Airworthiness 

Limitations, D626A001–9–04, would 

include the revised AWL No. 47–AWL– 

09. 

The FAA acknowledges the 

commenter’s request. Since publication 

of the NPRM, Boeing has issued Boeing 

737–600/700/700C/800/900/900ER 

Special Compliance Items/ 

Airworthiness Limitations, D626A001– 

9–04, dated November 2020 (Boeing 

D626A001–9–04, dated November 

2020), which limits the applicability of 

AWL No. 47–AWL–09 to certain Model 

737 airplanes and states that an oxygen 

sensor can be replaced with a new 

oxygen sensor or an oxygen sensor 

repaired per AWL No. 47–AWL–10 

‘‘Nitrogen Generation System—Oxygen 

Sensor Repair.’’ This AD requires 

updating the existing maintenance/ 

inspection program to incorporate 

Boeing D626A001–9–04, dated April 

2019; or Boeing D626A001–9–04, dated 

November 2020. In addition, based 

upon requests from other commenters, 

the FAA has extended the initial 

compliance time for replacement of the 

oxygen sensor due to a parts availability 

issue. The FAA has revised the grace 

period for the initial ALI task in 

paragraph (g)(13) of this AD from 12 

months to 36 months. This extended 

grace period will still provide an 

acceptable level of safety. 

Request To Extend the Compliance 

Time 

Air China, ANA, China Eastern 

Airlines (CEA), Delta Air lines (DAL), 

Japan Airlines (JAL), Okay Airlines 

(OKY), Southwest Airlines (SWA), and 

Turkish Airlines (THY) requested that 

the initial compliance time for the 

replacement of the oxygen sensor as 

specified in paragraph (g)(13) of the 

proposed AD be extended because of a 

parts availability issue. The commenters 

contacted Boeing and determined that 

there would be a shortage of parts, 

which would prevent them from 

complying with the proposed 

requirement specified in paragraph 

(g)(13) of the proposed AD within the 

compliance time specified in the 

proposed AD. 

The FAA agrees with the commenters’ 

requests based on the information 

provided by the commenters. The FAA 

contacted Boeing and confirmed that 

there is a parts availability issue, which 

could create an undue burden on 

operators because it could prevent them 

from complying with the requirement 

specified in paragraph (g)(13) of this 

AD, subsequently grounding the 

affected airplanes. The FAA has revised 

the initial compliance time in paragraph 

(g)(13) of this AD from 12 months to 36 

months. 

Request To Add an Off-Wing Inspection 

for AWL No. 47–AWL–09 

SWA requested that the FAA consider 

coordinating this AD with Boeing to 

allow for an off-wing inspection of the 

oxygen sensor, and repair if necessary, 

as opposed to a mandated time-limited 

replacement. SWA stated that this 

would mitigate the parts availability 

impact across the industry as well the 

cost of complying with AWL No. 47– 

AWL–09. 

The FAA agrees that an off-wing 

inspection would reduce the burden on 

operators. This AD allows operators to 

optionally incorporate Boeing 

D626A001–9–04, dated November 2020, 

which includes an off-wing inspection 

as specified in AWL No. 47–AWL–10. 

Boeing modified the requirement of 

AWL No. 47–AWL–09 to allow the use 

of repaired parts and added AWL No. 

47–AWL–10 to describe the 

requirements for the method of 

inspection/repair in Boeing D626A001– 

9–04, dated November 2020. This AD 

still requires operators to use Boeing 

D626A001–9–04, dated April 2019, but 

provides an option for operators to 

incorporate Boeing D626A001–9–04, 

dated November 2020, into their 

maintenance program. In addition, the 

FAA has determined that an on-wing 

inspection is currently being developed 

by Boeing and that subject on-wing 

inspection is expected to be 

implemented in a future revision of the 

Boeing D626A001–9–04 document. 

Under the provisions of paragraph (k) of 

this AD, the FAA will consider requests 

for approval of an alternative method of 

compliance (AMOC) if sufficient data 

are submitted to substantiate that the 

change would provide an acceptable 

level of safety. 

Request To Clarify the Applicability of 

a Certain AWL Item 

CEA, DAL, JAL, OKY, Ryan Air, and 

THY requested clarification of the 

applicability specified in AWL No. 47– 

AWL–09, which addresses replacement 

of the oxygen sensor in the NGS. The 

commenters noted that in Boeing 

D626A001–9–04, dated April 2019, the 

other AWLs specific to the NGS show 

the airplane applicability in terms of the 

airplanes that have the NGS installed, or 

incorporation of the actions in Boeing 

Service Bulletin 737–47–1002 or Boeing 

Service Bulletin 737–47–1003. The 

commenters noted that all airplanes on 

the U.S. registry are required to have the 

NGS system installed, but the 

commenters expected the applicability 

of AWL No. 47–AWL–09 to be similar 

to the other AWLs included in Boeing 

D626A001–9–04, dated April 2019. In 

addition, OKY noted that the 

applicability in AWL No. 47–AWL–09 

was listed as all airplanes, but in Boeing 

Fleet Team Digest Document 737NG– 

FTD–47–19003, created on May 8, 2020, 

the applicability is Model 737NG 

airplanes delivered after June 2019 or 

modified with a new, improved ASM 

(air separation module) using the 

procedures in Boeing Service Bulletin 

737–47–1015. 

DAL and the other commenters 

explained that they contacted Boeing 

regarding this applicability issue. The 

commenters stated that Boeing 

confirmed that the applicability 


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specified in AWL No. 47–AWL–09 is 

incorrect and Boeing advised that in the 

next revision of Boeing D626A001–9– 

04, dated April 2019, the applicability 

specified in AWL No. 47–AWL–09 will 

be updated to include airplanes having 

L/Ns 1820, 1831, 2517, 2620, and 

subsequent, and all airplanes that have 

incorporated the actions specified in 

Boeing Service Bulletin 737–47–1003. 

Several of the commenters stated that 

paragraph (g)(13) of the proposed AD 

should include additional text to clarify 

the applicability of AWL No. 47–AWL– 

09. The commenters stated that by 

incorporating this information into the 

final rule, the FAA would prevent the 

need for operators to apply for an 

AMOC in the future. 

The FAA acknowledges the 

commenters’ requests. As mentioned 

previously, Boeing has published 

Boeing D626A001–9–04, dated 

November 2020, and in this revision the 

applicability specified in AWL No. 47– 

AWL–09 was updated and limited to 

specify only airplanes having L/Ns 

1820, 1831, 2517, 2620, and subsequent, 

and all airplanes that have incorporated 

the actions specified in Boeing Service 

Bulletin 737–47–1003. The FAA has 

changed the AD to allow the use of 

Boeing D626A001–9–04, dated 

November 2020, which correctly 

identifies the applicability for AWL No. 

47–AWL–09. 

Request To Clarify the Unsafe 

Condition 

Boeing, DAL, and CEA requested 

clarification of the unsafe condition 

specified in the Discussion section of 

the NPRM and paragraph (e) of the 

proposed AD. The commenters 

remarked that the wording implied that 

increased flammability in the center fuel 

tank leads to fuel tank explosion. The 

commenters explained that increased 

flammability alone does not lead to a 

fuel tank explosion; there must also be 

a concurrent ignition source in the 

center fuel tank. The commenters 

suggested that it would be more 

accurate to state that the increased 

flammability combined with an ignition 

source could lead to a fuel tank 

explosion. 

In addition, the commenters 

requested that the unsafe condition be 

revised to address the potential loss of 

engine fuel suction feed capability. The 

commenters pointed out that paragraph 

(g)(14) of the proposed AD specified 

AWL No. 28–AWL–101, ‘‘Engine Fuel 

Suction Feed Operational Test,’’ which 

would be required to protect the 

airplane from engine flameout during 

suction feed operations. The 

commenters observed that this proposed 

action is not associated with the 

prevention of fuel tank ignition. 

The FAA agrees with the commenters’ 

requests based on the reasons provided 

by the commenters. The FAA has 

revised the Background section in this 

final rule and paragraph (e) of this AD 

accordingly. 

Request To Account for Indirect Costs 

ANA, CEA, DAL, OKY, SWA, and 

THY expressed concern regarding the 

indirect financial burden associated 

with accomplishing the actual on-wing 

work resulting from the maintenance 

program or inspection program changes 

that would be required by the proposed 

AD. DAL specifically noted that 

accomplishment of the oxygen sensor 

replacement specified in AWL No. 47– 

AWL–09, would require replacement of 

approximately 130 oxygen sensors with 

new oxygen sensors, and based on price 

quotes from the manufacturer of the 

oxygen sensors, it would cost an 

additional $7,000,000 over the 

estimated $7,560 per operator specified 

in the Costs of Compliance section of 

the NPRM. DAL stated that once all 

airplanes have reached the threshold for 

replacing the oxygen sensor the 

recurring cost would be approximately 

$2,000,000 per year for this task. 

The FAA disagrees with changing the 

cost of compliance information for this 

AD. The cost information provided in 

this AD describes only the direct costs 

of the specific actions required by this 

AD. The FAA recognizes that, in doing 

the actions required by an AD, operators 

might incur incidental costs in addition 

to the direct costs. The extended 

compliance time previously mentioned 

could alleviate some of these indirect 

costs, as they would be spread out over 

36 months instead of occurring within 

12 months. Also, Boeing D626A001–9– 

04, dated November 2020, was revised 

to allow operators to use a repaired 

oxygen sensor in AWL No. 47–AWL–09 

and added AWL No. 47–AWL–10 to 

describe the requirements for the 

method of inspection/repair. As 

identified above in a previous comment, 

operators now have the option to 

incorporate Boeing D626A001–9–04, 

dated November 2020, into their 

maintenance and inspection program, 

thereby reducing the financial impact of 

these requirements. The AD has not 

been changed in this regard. 

Request for Clarification of Compliance 

Time Interval Units 

DAL and CEA requested that the FAA 

explain why paragraph (g) of the 

proposed AD expressed compliance 

time intervals in terms of months when 

Boeing D626A001–9–04, dated April 

2019, specifies these intervals in terms 

of years. The commenter mentioned it 

was unclear if an AMOC would be 

required if an operator incorporated the 

compliance intervals in years, as 

specified in Boeing D626A001–9–04, 

dated April 2019, instead of months, as 

specified in the proposed AD. 

The FAA disagrees that there is a 

difference in the calculated compliance 

times described by the commenters. The 

FAA uses compliance times defined in 

months for required AD actions. 

Operators have the capability of 

converting years to months when 

comparing the compliance times of 

required AD actions and the times 

specified in a manufacturer’s document. 

The FAA has determined that operators 

should not be confused when these 

conversions take place and an operator 

does not need to request an AMOC. 

Regardless of how an operator records 

the compliance time, within 36 months 

or within 3 years after the effective date 

of this AD, the compliance times in this 

AD, Boeing D626A001–9–04, dated 

April 2019, and Boeing D626A001–9– 

04, dated November 2020, end at the 

same time. The FAA has not changed 

this AD in regard to this issue. 

Request To Include Additional Affected 

AD in Paragraph (b) of Proposed AD 

DAL and CEA requested that AD 

2018–20–13, Amendment 39–19447 (83 

FR 52305, October 17, 2018) (AD 2018– 

20–13), be included in the list of 

affected ADs in paragraph (b) of the 

proposed AD. DAL and CEA noted that 

paragraphs (i)(1)(i) through (iii) of AD 

2018–20–13 require incorporation of 

AWL Nos. 28–AWL–21, 28–AWL–22, 

and 28–AWL–24 that are included in 

Boeing 737–600/700/700C/800/900/ 

900ER Special Compliance Items/ 

Airworthiness Limitations, D626A001– 

9–04, dated June 2018, into an 

operator’s maintenance or inspection 

program as applicable. DAL and CEA 

suggested that only the latter revision of 

these AWLs that are included in Boeing 

D626A001–9–04, dated April 2019, 

should be mandated. DAL and CEA 

stated that the requirements of 

paragraphs (i)(1)(i) through (iii) of AD 

2018–20–13 should be terminated when 

the requirements of the proposed AD 

become effective. 

The FAA agrees with the commenter’s 

request; paragraph (b) of this AD has 

been revised to include AD 2018–20–13 

in paragraph (b)(6) of this AD, and the 

subsequent paragraph has been 

redesignated as paragraph (b)(7) of this 

AD. In addition, this AD has been 

revised to include a new paragraph (j)(6) 

of this AD to terminate the requirements 

specified in paragraphs (i)(1)(i) through 


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(iii) of AD 2018–20–13, and the 

subsequent paragraph has been 

redesignated as paragraph (j)(7) of this 

AD. 

Request To Change the Subject in 

Paragraph (d) of the Proposed AD 

DAL and CEA requested that the 

Subject in paragraph (d) of the proposed 

AD be changed from Air Transport 

Association (ATA) of America Code 71, 

Powerplant, to ATA Code 28, Fuel. DAL 

and CEA noted that the unsafe 

condition specified in the proposed AD 

is associated with ignition sources in 

the fuel tanks and flammability 

exposure of the center fuel tank. The 

fuel system is the subject of ATA Code 

28. Previously issued ADs identified in 

paragraph (b) of the proposed AD, 

which are similar to the proposed AD, 

have specified ATA Code 28 as the 

subject in paragraph (d). 

The FAA agrees with the commenter’s 

request based on the reasons provided 

by the commenter. Paragraph (d) of this 

AD has been changed to ATA Code 28, 

Fuel. 

Effects of Winglets on Accomplishment 

of the Proposed Actions 

Aviation Partners Boeing stated that 

the installation of blended or split 

scimitar winglets per Supplemental 

Type Certificated (STC) ST008300SE 

does not affect compliance with the 

proposed actions. 

The FAA agrees that STC 

ST008300SE does not affect compliance 

with the actions required by this AD. 

The FAA has not changed this AD in 

this regard. 

Reduction of Applicable Airplanes 

Since NPRM Was Issued 

The FAA has updated the 

applicability, paragraph (c) of this AD, 

to remove airplanes that were delivered 

with Boeing 737–600/700/700C/800/ 

900/900ER Special Compliance Items/ 

Airworthiness Limitations, D626A001– 

9–04, dated April 2019, thereby 

reducing the scope of the affected 

airplanes in this final rule. 

Conclusion 

The FAA reviewed the relevant data, 

considered the comments received, and 

determined that air safety and the 

public interest require adopting this 

final rule with the changes described 

previously and minor editorial changes. 

The FAA has determined that these 

minor changes: 

• Are consistent with the intent that 

was proposed in the NPRM for 

addressing the unsafe condition; and 

• Do not add any additional burden 

upon the public than was already 

proposed in the NPRM. 

The FAA also determined that these 

changes will not increase the economic 

burden on any operator or increase the 

scope of this final rule. 

Related Service Information Under 1 

CFR Part 51 

The FAA reviewed Boeing 737–600/ 

700/700C/800/900/900ER Special 

Compliance Items/Airworthiness 

Limitations, D626A001–9–04, dated 

April 2019; and Boeing 737–600/700/ 

700C/800/900/900ER Special 

Compliance Items/Airworthiness 

Limitations, D626A001–9–04, dated 

November 2020. This service 

information describes AWLs that 

include airworthiness limitation 

instructions (ALIs) and critical design 

configuration control limitations 

(CDCCLs) tasks related to fuel tank 

ignition prevention and the NGS. 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 the ADDRESSES section. 

Differences Between This AD and the 

Service Information 

The ‘‘Description’’ column of AWL 

No. 28–AWL–20 identifies certain 

operational tests. However, the 

operational test for left center tank fuel 

boost pump relay R54 and right center 

tank fuel boost pump relay R55 is not 

required for airplanes on which the 

actions specified in paragraph (g)(2)(ii) 

of AD 2011–20–07, Amendment 39– 

16818 (76 FR 60710, September 30, 

2011), have been done, or airplanes that 

have installed STC ST02076LA. 

Paragraph (g) of this AD requires 

operators to revise their existing 

maintenance or inspection program by 

incorporating, in part, AWL No. 28– 

AWL–05, ‘‘Wire Separation 

Requirements for New Wiring Installed 

in Proximity to Wiring That Goes Into 

the Fuel Tanks’’ in Boeing D626A001– 

9–04, dated November 2020. Paragraph 

(h) of this AD allows certain changes to 

be made to the requirements specified 

in AWL No. 28–AWL–05 as an option. 

Costs of Compliance 

The FAA estimates that this AD 

affects 2,057 airplanes of U.S. registry. 

The FAA estimates the following costs 

to comply with this AD: 

The FAA determined that revising the 

existing maintenance or inspection 

program takes an average of 90 workhours per operator, although the agency 

recognizes that this number may vary 

from operator to operator. In the past, 

the FAA estimated that this action takes 

1 work-hour per airplane. Since 

operators incorporate maintenance or 

inspection program changes for their 

affected fleet(s), the FAA determined 

that a per-operator estimate is more 

accurate than a per-airplane estimate. 

Therefore, the FAA estimates the 

average total cost per operator to be 

$7,650 (90 work-hours × $85 per workhour). 

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. 

Adoption of the Amendment 

Accordingly, under the authority 

delegated to me by the Administrator, 

the FAA amends 14 CFR part 39 as 

follows: 


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31608 Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Rules and Regulations 

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: 

2021–11–24 The Boeing Company: 

Amendment 39–21586; Docket No. 

FAA–2020–0341; Project Identifier 

2020–NM–017–AD. 

(a) Effective Date 

This airworthiness directive (AD) is 

effective July 20, 2021. 

(b) Affected (Airworthiness Directives) ADs 

This AD affects the ADs specified in 

paragraphs (b)(1) through (7) of this AD. 

(1) AD 2008–06–03, Amendment 39–15415 

(73 FR 13081, March 12, 2008) (AD 2008–06– 

03). 

(2) AD 2008–10–10 R1, Amendment 39– 

16164 (75 FR 1529, January 12, 2010) (AD 

2008–10–10 R1). 

(3) AD 2008–17–15, Amendment 39–15653 

(73 FR 50714, August 28, 2008) (AD 2008– 

17–15). 

(4) AD 2011–18–03, Amendment 39–16785 

(76 FR 53317, August 26, 2011) (AD 2011– 

18–03). 

(5) AD 2013–15–17, Amendment 39–17533 

(78 FR 52838, August 27, 2013) (AD 2013– 

15–17). 

(6) AD 2018–20–13, Amendment 39–19447 

(83 FR 52305, October 17, 2018) (AD 2018– 

20–13). 

(7) AD 2018–20–24, Amendment 39–19458 

(83 FR 51815, October 15, 2018) (AD 2018– 

20–24). 

(c) Applicability 

This AD applies to The Boeing Company 

Model 737–600, –700, –700C, –800, –900, 

and –900ER series airplanes, certificated in 

any category, Line Numbers (L/Ns) 1 through 

7596 inclusive, except L/Ns 7352, 7362, 

7377, 7417, 7457, 7522, 7587, and 7592. 

(d) Subject 

Air Transport Association (ATA) of 

America Code 28, Fuel. 

(e) Unsafe Condition 

This AD was prompted by significant 

changes made to the airworthiness 

limitations (AWLs) related to fuel tank 

ignition prevention and the nitrogen 

generation system (NGS). The FAA is issuing 

this AD to address the development of an 

ignition source inside the fuel tanks and also 

to prevent increasing the flammability 

exposure of the center fuel tank, which could 

lead to fuel tank explosion and consequent 

loss of the airplane. The FAA is also issuing 

this AD to prevent increasing the 

flammability exposure of the center fuel tank, 

which together with an ignition source in the 

fuel tank, could lead to a fuel tank explosion 

and consequent loss of the airplane. In 

addition, the FAA is issuing this AD to 

address the potential loss of engine fuel 

suction feed capability, which could result in 

dual engine flameouts, inability to restart 

engines, and consequent forced landing of 

the airplane. 

(f) Compliance 

Comply with this AD within the 

compliance times specified, unless already 

done. 

(g) Maintenance or Inspection Program 

Revision 

Within 60 days after the effective date of 

this AD, revise the existing maintenance or 

inspection program, as applicable, to 

incorporate the applicable information 

specified in Section A, including Subsections 

A.1., A.2., and A.3, of Boeing 737–600/700/ 

700C/800/900/900ER Special Compliance 

Items/Airworthiness Limitations, D626A001– 

9–04, dated April 2019; or November 2020; 

except as provided by paragraph (h) of this 

AD. The initial compliance times for the 

airworthiness limitation instruction (ALI) 

tasks are within the applicable compliance 

times specified in in paragraphs (g)(1) 

through (14) of this AD. 

(1) For AWL No. 28–AWL–01, ‘‘External 

Wires Over Center Fuel Tank’’: Within 120 

months after the date of issuance of the 

original airworthiness certificate or the 

original export certificate of airworthiness, or 

within 120 months after the most recent 

inspection was performed as specified in 

AWL No. 28–AWL–01, whichever is later. 

(2) For AWL No. 28–AWL–03, ‘‘Fuel 

Quantity Indicating System (FQIS)—Out 

Tank Wiring Lightning Shield to Ground 

Termination’’: Within 120 months after the 

date of issuance of the original airworthiness 

certificate or the original export certificate of 

airworthiness, or within 120 months after the 

most recent inspection was performed as 

specified in AWL No. 28–AWL–03, 

whichever is later. 

(3) For AWL No. 28–AWL–19, ‘‘Center 

Tank Fuel Boost Pump Automatic Shutoff 

System’’: Within 12 months after the date of 

issuance of the original airworthiness 

certificate or the original export certificate of 

airworthiness, within 12 months after 

accomplishment of the actions specified in 

Boeing Service Bulletin 737–28A1206, or 

within 12 months after the most recent 

inspection was performed as specified in 

AWL No. 28–AWL–19, whichever is latest. 

This AWL does not apply to airplanes that 

have complied with paragraph (s) of AD 

2011–18–03. 

(4) For AWL No. 28–AWL–20, ‘‘OverCurrent and Arcing Protection Electrical 

Design Features Operation—Boost Pump 

Ground Fault Interrupter (GFI)’’: Within 12 

months after the date of issuance of the 

original airworthiness certificate or the 

original export certificate of airworthiness, 

within 12 months after accomplishment of 

the actions specified in Boeing Service 

Bulletin 737–28A1201, or within 12 months 

after the most recent inspection was 

performed as specified in AWL No. 28– 

AWL–20, whichever is latest. 

(5) For AWL No. 28–AWL–23, ‘‘Center 

Tank Fuel Boost Pump Power Failed On 

Protection System’’: Within 12 months after 

the date of issuance of the original 

airworthiness certificate or the original 

export certificate of airworthiness, within 12 

months after accomplishment of the actions 

specified in Boeing Service Bulletin 737– 

28A1248, or within 12 months after the most 

recent inspection was performed as specified 

in AWL No. 28–AWL–23, whichever is latest. 

This AWL does not apply to airplanes that 

have complied with paragraph (s) of AD 

2011–18–03. 

(6) For AWL No. 28–AWL–24, ‘‘Spar Valve 

Motor Operated Valve (MOV) Actuator— 

Lightning and Fault Current Protection 

Electrical Bond’’: Within 72 months after 

accomplishment of the actions specified in 

Boeing Service Bulletin 737–28A1207, or 

within 72 months after the most recent 

inspection was performed as specified in 

AWL No. 28–AWL–24, whichever is later. 

(7) For AWL No. 28–AWL–29, ‘‘Full 

Cushion Clamps and Teflon Sleeving (If 

Installed) Installed on Out-of-Tank Wire 

Bundles Installed on Brackets that are 

Mounted Directly on the Fuel Tanks’’: For 

airplanes having line numbers (L/N) 1 

through 1754 inclusive, within 120 months 

after accomplishment of the actions specified 

in Boeing Service Bulletin 737–57A1279. For 

airplanes having L/N 1755 and subsequent, 

within 120 months after the date of issuance 

of the original airworthiness certificate or the 

original export certificate of airworthiness, or 

within 48 months after the effective date of 

this AD, whichever is later. 

(8) For AWL No. 28–AWL–35, ‘‘Fuel 

Quantity Indicating System (FQIS)—Center 

Fuel Tank In-Tank Component and Wire 

Harness Protection Features-Separation from 

Center Tank Internal Structure’’: For 

airplanes that have incorporated Boeing 

Service Bulletin 737–28–1356, within 120 

months after accomplishment of the actions 

specified in Boeing Service Bulletin 737–28– 

1356, or within 120 months after the most 

recent inspection was performed as specified 

in AWL No. 28–AWL–35, whichever is later. 

(9) For AWL No. 28–AWL–37, ‘‘Fuel 

Quantity Indicating System (FQIS)—Built in 

Test Equipment (BITE) Test’’: For airplane 

L/Ns 6987 and 7000 and subsequent, within 

750 flight hours since the date the most 

recent BITE test was accomplished as 

specified in AWL No. 28–AWL–37, or within 

750 flight hours after the effective date of this 

AD, whichever is later. 

(10) For AWL No. 47–AWL–04, ‘‘Nitrogen 

Generation System—Thermal Switch’’: 

Within 22,500 flight hours after the date of 

issuance of the original airworthiness 

certificate or the original export certificate of 

airworthiness, within 22,500 flight hours 

after accomplishment of the actions specified 

in Boeing Service Bulletin 737–47–1003, or 

within 22,500 flight hours after the most 

recent inspection was performed as specified 

in AWL No. 47–AWL–04, whichever is latest. 

(11) For AWL No. 47–AWL–06, ‘‘Nitrogen 

Generation System (NGS)—Cross Vent Check 

Valve’’: Within 13,000 flight hours after the 

date of issuance of the original airworthiness 

certificate or the original export certificate of 

airworthiness, within 13,000 flight hours 

after accomplishment of the actions specified 

in Boeing Service Bulletin 737–47–1003, or 

within 13,000 flight hours after the most 


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Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Rules and Regulations 31609 

recent inspection was performed as specified 

in AWL No. 47–AWL–06, whichever is latest. 

(12) For AWL No. 47–AWL–07, ‘‘Nitrogen 

Generation System (NGS)—Nitrogen 

Enriched Air (NEA) Distribution Ducting 

Integrity’’: Within 6,500 flight hours after the 

date of issuance of the original airworthiness 

certificate or the original export certificate of 

airworthiness, within 6,500 flight hours after 

accomplishment of the actions specified in 

Boeing Service Bulletin 737–47–1003, or 

within 6,500 flight hours after the most 

recent inspection was performed as specified 

in AWL No. 47–AWL–07, whichever is latest. 

(13) For AWL No. 47–AWL–09, ‘‘Nitrogen 

Generation System—Oxygen Sensor’’: Within 

18,000 flight hours after the date of issuance 

of the original airworthiness certificate or the 

original export certificate of airworthiness, or 

within 18,000 flight hours after the most 

recent replacement was performed as 

specified in AWL No. 47–AWL–09, or within 

36 months after the effective date of this AD, 

whichever is latest. 

(14) For AWL No. 28–AWL–101, ‘‘Engine 

Fuel Suction Feed Operational Test’’: Within 

7,500 flight hours or 36 months, whichever 

occurs first, after the date of issuance of the 

original airworthiness certificate or the 

original export certificate of airworthiness; or 

within 7,500 flight hours or 36 months, 

whichever occurs first, after the most recent 

inspection was performed as specified in 

AWL No. 28–AWL–101; whichever is later. 

(h) Additional Acceptable Exceptions to the 

AWLs 

As an option, when accomplishing the 

actions required by paragraph (g) of this AD, 

the changes specified in paragraphs (h)(1) 

through (3) of this AD are acceptable. 

(1) Where AWL No. 28–AWL–05 identifies 

wire types BMS 13–48, BMS 13–58, and BMS 

13–60, the following wire types are 

acceptable: MIL–W–22759/16, SAE 

AS22759/16 (M22759/16), MIL–W–22759/32, 

SAE AS22759/32 (M22759/32), MIL–W– 

22759/34, SAE AS22759/34 (M22759/34), 

MIL–W–22759/41, SAE AS22759/41 

(M22759/41), MIL–W–22759/86, SAE 

AS22759/86 (M22759/86), MIL–W–22759/87, 

SAE AS22759/87 (M22759/87), MIL–W– 

22759/92, and SAE AS22759/92 (M22759/ 

92); and MIL–C–27500 and NEMA WC 27500 

cables constructed from these military or 

SAE specification wire types, as applicable. 

(2) Where AWL No. 28–AWL–05 identifies 

TFE–2X Standard wall for wire sleeving, the 

following sleeving materials are acceptable: 

Roundit 2000NX and Varglas Type HO, HP, 

or HM. 

(3) Where AWL No. 28–AWL–20 specifies 

the operational test for left center tank fuel 

boost pump relay R54 and right center tank 

fuel boost pump relay R55, for airplanes that 

have complied with paragraph (g)(2)(ii) of AD 

2011–20–07, Amendment 39–16818 (76 FR 

60710, September 30, 2011), or that have 

installed Supplemental Type Certificate 

(STC) ST02076LA, that action does not 

apply. 

(i) No Alternative Actions, Intervals, or 

Critical Design Configuration Control 

Limitations (CDCCLs) 

Except as provided in paragraph (h) of this 

AD, after the existing maintenance or 

inspection program has been revised as 

required by paragraph (g) of this AD, no 

alternative actions (e.g., inspections), 

intervals, or CDCCLs may be used unless the 

actions, intervals, and CDCCLs are approved 

as an alternative method of compliance 

(AMOC) in accordance with the procedures 

specified in paragraph (k) of this AD. 

(j) Terminating Action for Certain AD 

Requirements 

Accomplishment of the revision required 

by paragraph (g) of this AD terminates the 

requirements specified in paragraphs (j)(1) 

through (7) of this AD for that airplane. 

(1) The revision required by the 

introductory text to paragraph (h) and 

paragraph (h)(1) of AD 2008–06–03. 

(2) All requirements of AD 2008–10–10 R1. 

(3) The revision required by paragraph (g) 

of AD 2008–17–15. 

(4) The revision required by paragraph (k) 

of AD 2011–18–03. 

(5) All requirements of AD 2013–15–17. 

(6) The revisions required by paragraphs 

(i)(1)(i) through (iii) of AD 2018–20–13. 

(7) All requirements of AD 2018–20–24. 

(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 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 paragraph (l) of this 

AD. 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 local flight standards district office/ 

certificate holding district 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. 

(l) Related Information 

For more information about this AD, 

contact Christopher Baker, Aerospace 

Engineer, Propulsion Section, FAA, Seattle 

ACO Branch, 2200 South 216th St., Des 

Moines, WA 98198; phone and fax: 206–231– 

3552; email: Christopher.R.Baker@faa.gov. 

(m) 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 737–600/700/700C/800/900/ 

900ER Special Compliance Items/ 

Airworthiness Limitations, D626A001–9–04, 

dated April 2019. 

(ii) Boeing 737–600/700/700C/800/900/ 

900ER Special Compliance Items/ 

Airworthiness Limitations, D626A001–9–04, 

dated November 2020. 

(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 fedreg.legal@nara.gov, or go to: https:// 

www.archives.gov/federal-register/cfr/ibrlocations.html. 

Issued on May 21, 2021. 

Lance T. Gant, 

Director, Compliance & Airworthiness 

Division, Aircraft Certification Service. 

[FR Doc. 2021–12436 Filed 6–14–21; 8:45 am] 

BILLING CODE 4910–13–P 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2021–0314; Project 

Identifier MCAI–2020–00599–R; Amendment 

39–21592; AD 2021–12–05] 

RIN 2120–AA64 

Airworthiness Directives; Airbus 

Helicopters 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final rule. 

SUMMARY: The FAA is adopting a new 

airworthiness directive (AD) for certain 

Airbus Helicopters Model EC155B1 

helicopters. This AD was prompted by 

a report of difficulties when jettisoning 

the co-pilot door during non-scheduled 

maintenance. This AD requires a 

functional check of the pilot and copilot door jettisoning system and 

corrective actions if necessary, as 

specified in a European Aviation Safety 

Agency (EASA) AD, which is 

incorporated by reference. The FAA is 

issuing this AD to address the unsafe 

condition on these products. 

DATES: This AD is effective July 20, 

2021. 


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