[Federal Register Volume 86, Number 88 (Monday, May 10, 2021)]
[Proposed Rules]
[Pages 24786-24789]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-09761]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0331; Project Identifier AD-2020-01703-T]
RIN 2120-AA64


Airworthiness Directives; The Boeing Company Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for all The Boeing Company Model 757 airplanes. This proposed AD was 
prompted by significant changes, including new or more restrictive 
requirements, made to the airworthiness limitations (AWLs) related to 
fuel tank ignition prevention and the nitrogen generation system. This 
proposed AD would require revising the existing maintenance or 
inspection program, as applicable, to incorporate new or more 
restrictive airworthiness limitations. 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 June 24, 
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 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.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0331; 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: Tak Kobayashi, Aerospace Engineer, 
Propulsion Section, FAA, Seattle ACO Branch, 2200 South 216th St., Des 
Moines, WA 98198; phone and fax: 206-231-3553; email: 
[email protected].

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.

[[Page 24787]]

FAA-2021-0331; Project Identifier AD-2020-01703-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 Tak 
Kobayashi, Aerospace Engineer, Propulsion Section, FAA, Seattle ACO 
Branch, 2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-
231-3553; email: [email protected]. 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 examined the underlying safety issues involved in fuel 
tank explosions on several large transport airplanes, including the 
adequacy of existing regulations, the service history of airplanes 
subject to those regulations, and existing maintenance practices for 
fuel tank systems. As a result of those findings, the FAA issued a 
final rule titled ``Transport Airplane Fuel Tank System Design Review, 
Flammability Reduction, and Maintenance and Inspection Requirements'' 
(66 FR 23086, May 7, 2001). In addition to new airworthiness standards 
for transport airplanes and new maintenance requirements that rule 
included Amendment 21-78, which established Special Federal Aviation 
Regulation No. 88 (``SFAR 88'') to 14 CFR part 21. Subsequently, SFAR 
88 was amended by: Amendment 21-82 (67 FR 57490, September 10, 2002; 
corrected at 67 FR 70809, November 26, 2002), Amendment 21-83 (67 FR 
72830, December 9, 2002; corrected at 68 FR 37735, June 25, 2003, to 
change ``21-82'' to ``21-83''), and Amendment 21-101 (83 FR 9162, March 
5, 2018).
    Among other actions, SFAR 88 requires certain type design (i.e., 
type certificate (TC) and supplemental type certificate (STC)) holders 
to substantiate that their fuel tank systems can prevent ignition 
sources in the fuel tanks. This requirement applies to type design 
holders for large turbine-powered transport airplanes and for 
subsequent modifications to those airplanes. It requires them to 
perform design reviews and to develop design changes and maintenance 
procedures if their designs do not meet the new fuel tank safety 
standards. As explained in the preamble to the final rule published on 
May 7, 2001, the FAA intended to adopt airworthiness directives to 
mandate any changes found necessary to address unsafe conditions 
identified as a result of these reviews.
    In evaluating these design reviews, the FAA has established four 
criteria intended to define the unsafe conditions associated with fuel 
tank systems that require corrective actions. The percentage of 
operating time during which fuel tanks are exposed to flammable 
conditions is one of these criteria. The other three criteria address 
the failure types under evaluation: Single failures, single failures in 
combination with another latent condition(s), and in-service failure 
experience. For all four criteria, the evaluations included 
consideration of previous actions taken that may mitigate the need for 
further action.
    The FAA issued AD 2012-12-15, Amendment 39-17095 (77 FR 42964, July 
23, 2012) (AD 2012-12-15), which applies to all The Boeing Company 
Model 757 airplanes. AD 2012-12-15 requires revising the maintenance or 
inspection program to incorporate new limitations for fuel tank 
systems. AD 2012-12-15 also requires the initial inspection of certain 
repetitive AWL inspections to phase-in those inspections, and repair if 
necessary. Since the FAA issued AD 2012-12-15, the Airworthiness 
Limitations Section (ALS) of the Instructions for Continued 
Airworthiness (Boeing document D622N001-9) has been significantly 
revised by the manufacturer to correct technical and editorial errors 
and also to add new or more restrictive requirements. Many of those 
changes are related to fuel tank ignition prevention and the nitrogen 
generation system. Incorporating the revision required by this proposed 
AD would terminate all the requirements of AD 2012-12-15.
    The FAA also issued AD 2018-20-13, Amendment 39-19447 (83 FR 52305, 
October 17, 2018) (2018-20-13), which applies to all The Boeing Company 
Model 757 airplanes; Model 737 airplanes, excluding Model 737-100, -
200, -200C, -300, -400, and -500 series airplanes; and Model 767-200, -
300, -300F, and -400ER series airplanes. For Model 757 airplanes, AD 
2018-20-13 requires, among other things, revising the maintenance or 
inspection program to incorporate AWLs No. 28-AWL-23, 28-AWL-24, and 
28-AWL-25. Since the FAA issued 2018-20-13, those AWLs have been 
revised, therefore, this proposed AD would require the incorporation of 
those revised AWLs. Incorporating the revision required by this 
proposed AD would terminate the requirements in paragraph (i)(2) of AD 
2018-20-13.
    The FAA has assessed the changes, including new or more restrictive 
requirements, that were made to the AWLs related to fuel tank ignition 
prevention and the nitrogen generation system. The FAA is issuing this 
AD to address ignition sources inside the fuel tanks and the increased 
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.

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 Section 9, Airworthiness Limitations (AWLs) and 
Certification Maintenance Requirements (CMRs), of Boeing 757 
Maintenance Planning Data (MPD) Document, D622N001-9, dated March 2020. 
This service information specifies airworthiness limitation instruction 
(ALI) and critical design configuration control limitation (CDCCL) 
tasks related to fuel tank ignition prevention and the nitrogen 
generation system.

[[Page 24788]]

    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.

Proposed AD Requirements in This NPRM

    This proposed AD would require revising the existing maintenance or 
inspection program, as applicable, to incorporate new or more 
restrictive airworthiness limitations.
    This proposed AD would require revisions to certain operator 
maintenance documents to include new actions (e.g., inspections) and 
CDCCLs. Compliance with these actions and CDCCLs is required by 14 CFR 
91.403(c). For airplanes that have been previously modified, altered, 
or repaired in the areas addressed by this proposed AD, the operator 
may not be able to accomplish the actions described in the revisions. 
In this situation, to comply with 14 CFR 91.403(c), the operator must 
request approval for an alternative method of compliance according to 
paragraph (k) of this proposed AD.

Differences Between This Proposed AD and the Service Information

    Paragraph (g) of this proposed AD would require 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,'' of 
Section 9, Airworthiness Limitations (AWLs) and Certification 
Maintenance Requirements (CMRs), of Boeing 757 Maintenance Planning 
Data (MPD) Document, D622N001-9, dated March 2020.
    Paragraph (h) of this proposed AD would allow certain changes to be 
made to the requirements specified in AWL No. 28-AWL-05 as an option. 
Where AWL No. 28-AWL-05 identifies certain wire types for routing and 
installation of any new wiring under certain conditions, paragraph (h) 
of this proposed AD provides acceptable alternative wire types. Where 
AWL No. 28-AWL-05 identifies certain wiring sleeve material for new 
wiring installed under certain conditions, paragraph (h) of this 
proposed AD provides acceptable alternative wire sleeve materials.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 493 airplanes of U.S. registry. The FAA estimates the following 
costs to comply with this proposed AD:
    The FAA has determined that revising the existing maintenance or 
inspection program takes an average of 90 work-hours per operator, 
although the agency recognizes that this number may vary from operator 
to operator. Since operators incorporate maintenance or inspection 
program changes for their affected fleet(s), the FAA has 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 x $85 per work-hour).

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

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by adding the following new airworthiness 
directive:

The Boeing Company: Docket No. FAA-2021-0331; Project Identifier AD-
2020-01703-T.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by June 24, 2021.

(b) Affected ADs

    This AD affects the ADs specified in paragraphs (b)(1) and (2) 
of this AD.
    (1) AD 2012-12-15, Amendment 39-17095 (77 FR 42964, July 23, 
2012) (AD 2012-12-15).
    (2) AD 2018-20-13, Amendment 39-19447 (83 FR 52305, October 17, 
2018).

(c) Applicability

    This AD applies to all The Boeing Company Model 757-200, -200PF, 
-200CB, and -300 series airplanes, certificated in any category.

(d) Subject

    Air Transport Association (ATA) of America Code 28, Fuel.

(e) Unsafe Condition

    This AD was prompted by significant changes, including new or 
more restrictive requirements, made to the airworthiness limitations 
(AWLs) related to fuel tank ignition prevention and the nitrogen 
generation system. The FAA is issuing this AD to address ignition 
sources inside the fuel tanks and the increased 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.

(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 information specified in Section E. ``Airworthiness 
Limitations--Systems,'' including Subsections E.1 and E.3, of 
Section 9, Airworthiness Limitations (AWLs) and Certification 
Maintenance

[[Page 24789]]

Requirements (CMRs), of Boeing 757 Maintenance Planning Data (MPD) 
Document, D622N001-9, dated March 2020; except as provided by 
paragraph (h) of this AD. The initial compliance time for doing the 
airworthiness limitation instruction (ALI) tasks is at the times 
specified in paragraphs (g)(1) through (12) of this AD.
    (1) For AWL No. 28-AWL-01, ``External Wires Over Center Fuel 
Tank'': Within 120 months after the most recent inspection was 
performed as specified in AWL No. 28-AWL-01.
    (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 most recent inspection was performed as 
specified in AWL No. 28-AWL-03.
    (3) For AWL No. 28-AWL-14, ``Main and Center Wing Tank Fueling 
Shutoff Valve Body and Actuator--Fault Current Bond'': Within 120 
months after the most recent inspection was performed as specified 
in AWL No. 28-AWL-14.
    (4) For AWL No. 28-AWL-20, ``Center Tank Fuel Override Boost 
Pump Automatic Shutoff System'': Within 12 months after 
accomplishment of the actions specified in Boeing Service Bulletin 
757-28A0081 or Boeing Service Bulletin 757-28A0082, as applicable; 
or within 12 months after the most recent inspection was performed 
as specified in AWL No. 28-AWL-20; whichever occurs later.
    (5) For AWL No. 28-AWL-21, ``Over-Current and Arcing Protection 
Electrical Design Features Operation--Boost Pump Ground Fault 
Interrupter (GFI)'': Within 12 months after accomplishment of the 
actions specified in Boeing Service Bulletin 757-28A0078 or Boeing 
Service Bulletin 757-28A0079, as applicable; or within 12 months 
after the most recent inspection was performed as specified in AWL 
No. 28-AWL-21; whichever occurs later.
    (6) For AWL No. 28-AWL-25, ``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 757-28A0088, or within 72 months after the 
most recent inspection was performed as specified in AWL No. 28-AWL-
25, whichever occurs later.
    (7) For AWL No. 28-AWL-26, ``Center Tank Fuel Boost Pump Power 
Failed On Protection System'': Within 12 months after accomplishment 
of the actions specified in Boeing Service Bulletin 757-28A0105, or 
within 12 months after the most recent inspection was performed as 
specified in AWL No. 28-AWL-26, whichever occurs later.
    (8) For AWL No. 28-AWL-30, ``AC Fuel Pump Fault Current Bonding 
Jumper Installation, Main and Center Tank'': Within 24 months after 
the effective date of this AD, or within 72 months after the most 
recent inspection was performed as specified in AWL No. 28-AWL-30, 
whichever occurs later.
    (9) For AWL No. 28-AWL-33, ``Full Cushion Clamps and Teflon 
Sleeving Installed on Out-of-Tank Wire Bundles Installed on Brackets 
that are Mounted Directly on the Fuel Tanks'': Within 24 months 
after the effective date of this AD; or within 144 months after 
accomplishment of the actions specified in Boeing Service Bulletin 
757-57A0064 (Part 2 through Part 10 of the Work Instructions); or 
within 144 months since the most recent inspection was performed as 
specified in AWL No. 28-AWL-33; whichever occurs later.
    (10) For AWL No. 47-AWL-04, ``NGS--NEA Distribution Ducting'': 
Within 17,300 flight hours after accomplishment of the actions 
specified in Boeing Service Bulletin 757-47-0001 or Boeing Service 
Bulletin757-47-0005, as applicable; or within 17,300 flight hours 
after the most recent inspection was performed as specified in AWL 
No. 47-AWL-04; whichever occurs later.
    (11) For AWL No. 47-AWL-05, ``NGS--Cross Vent Check Valve'': 
Within 17,300 flight hours after accomplishment of the actions 
specified in Boeing Service Bulletin 757-47-0001 or Boeing Service 
Bulletin 757-47-0005, as applicable; or within 17,300 flight hours 
after the most recent inspection was performed as specified in AWL 
No. 47-AWL-05; whichever occurs later.
    (12) For AWL No. 47-AWL-07, ``NGS--Thermal Switch'': Within 
48,000 flight hours after accomplishment of the actions specified in 
Boeing Service Bulletin 757-47-0001 or Boeing Service Bulletin 757-
47-0005, as applicable; or within 48,000 flight hours after the most 
recent inspection was performed as specified in AWL No. 47-AWL-07; 
whichever occurs later.

(h) Additional Acceptable Wire Types and Sleeving

    As an option, when accomplishing the actions required by 
paragraph (g) of this AD, the alternatives specified in paragraphs 
(h)(1) and (2) 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.

(i) No Alternative Actions, Intervals, or CDCCLs

    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 Actions for Certain AD Requirements

    Accomplishment of the revision required by paragraph (g) of this 
AD terminates the requirements specified in paragraphs (j)(1) and 
(2) of this AD for that airplane.
    (1) All requirements of AD 2012-12-15.
    (2) The requirements in paragraph (i)(2) of AD 2018-20-13.

(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: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the responsible Flight Standards Office.
    (3) An AMOC that provides an acceptable level of safety may be 
used for any repair, modification, or alteration required by this AD 
if it is approved by The Boeing Company Organization Designation 
Authorization (ODA) that has been authorized by the Manager, 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

    (1) For more information about this AD, contact Tak Kobayashi, 
Aerospace Engineer, Propulsion Section, FAA, Seattle ACO Branch, 
2200 South 216th St., Des Moines, WA 98198; phone and fax: 206-231-
3553; email: [email protected].
    (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 April 15, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-09761 Filed 5-7-21; 8:45 am]
BILLING CODE 4910-13-P