[Federal Register Volume 86, Number 72 (Friday, April 16, 2021)]
[Proposed Rules]
[Pages 20094-20097]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-07550]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0273; Project Identifier AD-2021-00050-E]
RIN 2120-AA64


Airworthiness Directives; General Electric Company Turbofan 
Engines

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 General Electric Company (GE) GEnx-1B64, GEnx-1B64/P1, GEnx-
1B64/P2, GEnx-1B67, GEnx-1B67/P1, GEnx-1B67/P2, GEnx-1B70, GEnx-1B70/
75/P1, GEnx-1B70/75/P2, GEnx-1B70/P1, GEnx-1B70/P2, GEnx-1B70C/P1, 
GEnx-1B70C/P2, GEnx-1B74/75/P1, GEnx-1B74/75/P2, GEnx-1B76/P2, GEnx-
1B76A/P2, GEnx-2B67, GEnx-2B67/P, and GEnx-2B67B model turbofan 
engines. This proposed AD was prompted by an in-service occurrence of 
loss of engine thrust control resulting in uncommanded high thrust. 
This proposed AD would require revising the operator's existing FAA-
approved minimum equipment list (MEL) by incorporating into the MEL the 
dispatch restrictions listed in this AD. This proposed AD would also 
require initial and repetitive replacement of the electronic engine 
control (EEC) MN4 microprocessor. 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 1, 
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 General 
Electric Company, 1 Neumann Way, Cincinnati, OH 45215; phone: (513) 
552-3272; email: [email protected]; website: www.ge.com. 
You may view this service information at the 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.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0273; 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: Mehdi Lamnyi, Aviation Safety 
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; 
phone: (781) 238-7743; fax: (781) 238-7199; 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. FAA-2021-0273; Project Identifier 
AD-2021-00050-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 Mehdi 
Lamnyi, Aviation Safety Engineer, ECO Branch, FAA, 1200 District 
Avenue, Burlington, MA 01803. 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 from the manufacturer of an in-service 
loss of engine thrust control on a GE90-115B model turbofan engine on 
October 27, 2019, that resulted in uncommanded high thrust. Analysis by 
the manufacturer found accumulated thermal cycles of the MN4 integrated 
circuit in the EEC, through normal operation, causes the solder ball 
joints to wear out and eventually fail over time. Since the GE90 and 
the GEnx model turbofan engines share the same EEC hardware and 
experience similar thermal and vibratory environments, the manufacturer 
determined that GEnx model turbofan engines are susceptible to the same 
type of failure. This condition, if not addressed, could result in loss 
of engine thrust control and reduced control of the airplane.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed GE GEnx-1B Service Bulletin (SB) 73-0097 R01, 
dated January 29, 2021, and R00, dated December 17, 2020; and GE GEnx-
2B SB 73-0090 R01, dated January 28, 2021, and R00, dated December 17, 
2020. This service information specifies procedures for replacing the 
EEC MN4 microprocessor on GEnx-1B and GEnx-2B model turbofan engines, 
as applicable. 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 operator's 
FAA-

[[Page 20095]]

approved MEL by incorporating into the MEL the dispatch restrictions 
listed in paragraph (g) of this AD. This proposed AD would also require 
initial and repetitive replacement of the EEC MN4 microprocessor using 
an approved overhaul procedure.

Interim Action

    The FAA considers that this proposed AD would be an interim action. 
If final action is later identified, the FAA might consider additional 
rulemaking.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 308 engines installed on airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this proposed 
AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Revise operator's FAA-approved MEL....  1 work-hour x $85 per                 $0             $85         $26,180
                                         hour = $85
Replace EEC MN4 microprocessor........  1 work-hour x $85 per             25,200          25,285       7,787,780
                                         hour = $85
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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:

General Electric Company: Docket No. FAA-2021-0273; Project 
Identifier AD-2021-00050-E.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by June 1, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to General Electric Company (GE) GEnx-1B64, 
GEnx-1B64/P1, GEnx-1B64/P2, GEnx-1B67, GEnx-1B67/P1, GEnx-1B67/P2, 
GEnx-1B70, GEnx-1B70/75/P1, GEnx-1B70/75/P2, GEnx-1B70/P1, GEnx-
1B70/P2, GEnx-1B70C/P1, GEnx-1B70C/P2, GEnx-1B74/75/P1, GEnx-1B74/
75/P2, GEnx-1B76/P2, GEnx-1B76A/P2, GEnx-2B67, GEnx-2B67/P, and 
GEnx-2B67B model turbofan engines.

(d) Subject

    Joint Aircraft System Component (JASC) Code 7600, Engine 
Controls.

(e) Unsafe Condition

    This AD was prompted by an in-service occurrence of loss of 
engine thrust control resulting in uncommanded high thrust. The FAA 
is issuing this AD to prevent dispatch of the airplane when certain 
conditions caused by degradation of the MN4 microprocessor in the 
electronic engine control (EEC) are present. The unsafe condition, 
if not addressed, could result in loss of engine thrust control and 
reduced control of the airplane.

(f) Compliance

    Comply with this AD within the compliance times specified, 
unless already done.

(g) Required Actions

    (1) For all affected GEnx-1B model turbofan engines, within 120 
days of the effective date of this AD, revise the operator's 
existing FAA-approved minimum equipment list (MEL) by incorporating 
into the MEL the dispatch restriction specified in Figure 1 to 
paragraph (g)(1) of this AD, as a required operation or maintenance 
procedure.
    Note 1 to paragraph (g)(1): Specific alternative MEL wording to 
accomplish the actions specified in Figure 1 can be approved by the 
operator's principal operations or maintenance inspector.

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[GRAPHIC] [TIFF OMITTED] TP16AP21.000

    (2) For all affected GEnx-2B model turbofan engines, within 120 
days of the effective date of this AD, revise the operator's 
existing FAA-approved MEL by incorporating into the MEL the dispatch 
restriction specified in Figure 2 to paragraph (g)(2) of this AD, as 
a required operation or maintenance procedure.
    Note 2 to paragraph (g)(2): Specific alternative MEL wording to 
accomplish the actions specified in Figure 2 can be approved by the 
operator's principal operations or maintenance inspector.

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[GRAPHIC] [TIFF OMITTED] TP16AP21.001

    (3) For all affected engines, before the EEC reaches 11,000 
cycles since new, replace the EEC MN4 microprocessor using an 
approved overhaul procedure.
    (i) Thereafter, replace the EEC MN4 microprocessor before 
accumulating 11,000 cycles since the last replacement.
    (ii) [Reserved]

(h) Definition

    For the purposes of this AD, an approved overhaul procedure is 
one of the following:
    (i) Replacement of the EEC MN4 microprocessor using FADEC 
International-approved maintenance procedures; or
    (ii) Replacement of the EEC MN4 microprocessor using the 
Accomplishment Instructions, paragraph 3., as applicable, of GEnx-1B 
Service Bulletin (SB) 73-0097 R00, dated December 17, 2020, or R01, 
dated January 29, 2021; or GEnx-2B SB 73-0090 R00, dated December 
17, 2020, or R01, dated January 28, 2021.

(i) Installation Prohibition

    After the effective date of this AD, do not install onto any 
engine an EEC with a main channel board that was subject to more 
than three replacements of the EEC MN4 microprocessor.

(j) 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. 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 local flight standards district office/certificate holding 
district office.

(k) Related Information

    (1) For more information about this AD, contact Mehdi Lamnyi, 
Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA 01803; phone: (781) 238-7743; fax: (781) 238-7199; 
email: [email protected].
    (2) For service information identified in this AD, contact 
General Electric Company, 1 Neumann Way, Cincinnati, OH 45215; 
phone: (513) 552-3272; email: [email protected]; 
website: www.ge.com. You may view this referenced service 
information at the 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.

    Issued on April 7, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-07550 Filed 4-15-21; 8:45 am]
BILLING CODE 4910-13-P