Document ID: FAA-2022-1240-0001
Agency: faa
Document Type: Proposed Rule
Title: Airworthiness Directives: General Electric Company Turbofan Engines
Posted Date: 2022-11-14T05:00Z

[Federal Register Volume 87, Number 218 (Monday, November 14, 2022)]
[Proposed Rules]
[Pages 68113-68116]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-23911]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1240; Project Identifier AD-2022-00683-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 certain General Electric Company (GE) GE90-76B, GE90-85B, GE90-90B, 
and GE90-94B model turbofan engines. This proposed AD was prompted by a 
commanded in-flight shutdown (IFSD) due to cracking and rockback of the 
high-pressure turbine (HPT) stage 2 nozzles resulting in blade 
liberation, severe rotor imbalance, and liberation of the exhaust 
centerbody. This proposed AD would require initial and repetitive 
borescope inspections (BSIs) of the forward platforms of the HPT stage 
2 blades or the leading edges of the HPT stage 2 nozzles and, depending 
on the results of the inspections, removal and replacement of the HPT 
stage 2 nozzles with a part eligible for installation. As a mandatory 
terminating action to the repetitive BSIs of the forward platforms of 
the HPT stage 2 blades or the leading edges of the HPT stage 2 nozzles, 
this proposed AD would require replacement of the HPT stage 2 nozzles. 
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 December 
29, 2022.

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 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.
    AD Docket: You may examine the AD docket at regulations.gov by 
searching for and locating Docket No. FAA-2022-1240; 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.
    Material Incorporated by Reference: For service information 
identified in this NPRM, contact General Electric Company, GE Aviation, 
Room 285, 1 Neumann Way, Cincinnati, OH 45215; phone: (513) 552-3272; 
email: [email protected]. 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 (817) 
222-5110.

FOR FURTHER INFORMATION CONTACT: Stephen Elwin, Aviation Safety 
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; 
phone: (781) 238-7236; 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-2022-1240; Project Identifier 
AD-2022-00683-E'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the

[[Page 68114]]

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 
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 
Stephen Elwin, 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 of a commanded IFSD of a GE90-85B model 
turbofan engine installed on a Boeing Model 777-200ER airplane that 
occurred on July 12, 2018. Subsequent investigation by the manufacturer 
found that cracking and rockback of the HPT stage 2 nozzles, due to 
thermal distress in the fillet radius of the leading edge, resulted in 
rotor-stator contact with the HPT stage 2 blade platform. This 
condition caused liberation of an HPT stage 2 blade and severe rotor 
imbalance, leading to liberation of the exhaust centerbody from the 
engine. This condition, if not addressed, could result in IFSD, failure 
of the engine and exhaust centerbody, and loss 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 GE90 Service Bulletin (SB) 72-1166, Revision 3, 
dated February 14, 2019. This service information specifies procedures 
for BSIs of the HPT stage 2 blade forward platforms for rub marks or 
evidence of contact (circumferential grooves on the HPT stage 2 blade 
platforms) with the HPT stage 2 nozzle angel wings. This service 
information also specifies procedures for performing a 360-degree BSI 
of the HPT stage 2 nozzles leading edges and specifies procedures for 
removal and replacement of HPT stage 2 nozzles.
    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.

Other Related Service Information

    The FAA reviewed GE GE90 SB 72-1071, Revision 1, dated January 16, 
2015. This service information specifies procedures for removal and 
replacement of HPT stage 2 nozzles with HPT stage 2 nozzles that 
incorporate a design change.
    The FAA also reviewed GE GE90 SB 72-1216, Initial Issue, dated 
August 22, 2022. This service information specifies inspection 
procedures for affected HPT stage 2 nozzles.

Proposed AD Requirements in This NPRM

    This proposed AD would require initial and repetitive borescope 
inspections of the forward platforms of the HPT stage 2 blades or the 
leading edges of the HPT stage 2 nozzles and, depending on the results 
of the inspections, removal and replacement of the HPT stage 2 nozzles 
with parts eligible for installation. As a mandatory terminating action 
to the repetitive BSIs of the forward platforms of the HPT stage 2 
blades or the leading edges of the HPT stage 2 nozzles, this proposed 
AD would require replacement of the HPT stage 2 nozzles.

Differences Between This Proposed AD and the Service Information

    GE GE90 SB 72-1166, Revision 3, dated February 14, 2019, specifies 
BSIs be performed upon reaching the threshold of the analytical model 
for the HPT stage 2 nozzles after GE Aviation issues a customer 
notification report for any engine that reaches the analytical 
threshold, while this proposed AD would require that BSIs be performed 
based on the flight hours accrued on the HPT stage 2 nozzles since new 
or since overhaul.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 8 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
----------------------------------------------------------------------------------------------------------------
BSI of HPT stage 2 nozzles or HPT       4 work-hours x $85 per                $0            $340          $2,720
 stage 2 blade interface.                hour = $340.
----------------------------------------------------------------------------------------------------------------

    The FAA estimates the following costs to do any necessary 
replacements that would be required based on the results of the 
proposed inspections. The agency has no way of determining the number 
of aircraft that might need these replacements.

[[Page 68115]]

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Replace full set of HPT stage 2 nozzles.......  8 work-hours x $85 per hour =           $918,650        $919,330
                                                 $680.
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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-2022-1240; Project 
Identifier AD-2022-00683-E.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by December 29, 2022.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to General Electric Company (GE) GE90-76B, GE90-
85B, GE90-90B, and GE90-94B model turbofan engines, excluding those 
engines with an installed full set of high-pressure turbine (HPT) 
stage 2 nozzles with part numbers 1847M47G23 and 1847M47G24.

(d) Subject

    Joint Aircraft System Component (JASC) Code 7250, Turbine 
Section.

(e) Unsafe Condition

    This AD was prompted by a commanded in-flight shutdown (IFSD) 
due to cracking and rockback of the HPT stage 2 nozzles resulting in 
blade liberation, severe rotor imbalance, and liberation of the 
exhaust centerbody. The FAA is issuing this AD to prevent failure of 
the HPT stage 2 nozzles, HPT stage 2 blades, and exhaust centerbody. 
The unsafe condition, if not addressed, could result in IFSD, 
failure of the engine and exhaust centerbody, and loss of the 
airplane.

(f) Compliance

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

(g) Required Actions

    (1) Within the compliance times specified in paragraphs 
(g)(1)(i) and (ii) of this AD, perform an initial borescope 
inspection (BSI) of the forward platforms of the HPT stage 2 blades, 
or perform a 360 degree BSI of the leading edges of the HPT stage 2 
nozzles (optional procedure) in accordance with the Accomplishment 
Instructions, paragraph 3.A.(3)(a) of GE GE90 SB 72-1166, Revision 
3, dated February 14, 2019 (the SB):
    (i) For engines with HPT stage 2 nozzles that have accumulated 
22,000 or more flight hours since new or since last overhaul as of 
the effective date of this AD, perform the initial BSI before 
accumulating 250 flight cycles (FCs) after the effective date of 
this AD.
    (ii) For engines with HPT stage 2 nozzles that have accumulated 
less than 22,000 flight hours since new or since last overhaul as of 
the effective date of this AD, perform the initial BSI before 
accumulating 22,000 flight hours since new or since last overhaul, 
or within 250 FCs after the effective date of this AD, whichever 
occurs later.
    (2) Thereafter, at intervals not to exceed 100 FCs from 
performance of the last BSI of the forward platforms of the HPT 
stage 2 blades, or at intervals not to exceed 500 FCs from the last 
BSI of the leading edges of the HPT stage 2 nozzles, as applicable, 
perform a repetitive BSI of the forward platforms of the HPT stage 2 
blades or the leading edges of the HPT stage 2 nozzles in accordance 
with the Accomplishment Instructions, paragraph 3.A.(3)(a) of the 
SB.
    (3) If, during any inspection required by paragraphs (g)(1) or 
(g)(2) of this AD, rub marks, evidence of contact on the HPT stage 2 
blade forward platform on three or more HPT stage 2 blades, or an 
unserviceable HPT stage 2 nozzle is found, before further flight, 
remove and replace the HPT stage 2 nozzles with a part eligible for 
installation.
    Note 1 to paragraph (g)(3): Serviceability criteria can be found 
in the GE90 Boeing 777 Aircraft Maintenance Manual, 72-00-00, 
INSPECTION/CHECK, Subtask 72-00-00-220-074-G00.

(h) Mandatory Terminating Action

    As a mandatory terminating action to the repetitive inspections 
required by paragraph (g)(2) of this AD, at the next engine shop 
visit after reaching 22,000 flight hours since new or since last 
overhaul, replace the HPT stage 2 nozzles with parts eligible for 
installation.

(i) Definitions

    (1) For the purpose of this AD, ``parts eligible for 
installation'' is a full set of HPT stage 2 nozzles with part 
numbers 1847M47G23 and 1847M47G24.
    (2) For the purpose of this AD, an ``overhaul'' is the complete 
refurbishment of the HPT stage 2 nozzle segments.
    (3) For the purpose of this AD, and ``engine shop visit'' is the 
induction of an engine into the shop for maintenance involving 
separation of pairs of major mating engine case flanges, except for 
the following situations, which do not constitute an engine shop 
visit:
    (i) Separation of engine flanges solely for the purposes of 
transportation of the engine without subsequent maintenance; or
    (ii) Separation of engine flanges solely for the purpose of 
replacing the fan or propulsor without subsequent maintenance.

[[Page 68116]]

(j) Credit for Previous Actions

    You may take credit for the initial inspection required by 
paragraph (g)(1) of this AD if you performed the inspection before 
the effective date of this AD using GE GE90 SB 72-1166, Revision 2, 
dated October 13, 2017, or earlier revisions.

(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 paragraph (l)(1) of this AD. 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.

(l) Related Information

    (1) For more information about this AD, contact Stephen Elwin, 
Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA 01803; phone: (781) 238-7236; email: 
[email protected].
    (2) GE service information identified in this AD that is not 
incorporated by reference is available at the addresses specified in 
paragraph (m)(3) of this AD.

(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 GE90 Service Bulletin (SB) 72-1166, Revision 3, dated 
February 14, 2019.
    (ii) [Reserved]
    (3) For GE service information identified in this AD, contact 
General Electric Company, GE Aviation, Room 285, 1 Neumann Way, 
Cincinnati, OH 45215; phone: (513) 552-3272; email: 
[email protected].
    (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 (817) 222-5110.
    (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: [email protected], or go to: www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on September 26, 2022.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2022-23911 Filed 11-10-22; 8:45 am]
BILLING CODE 4910-13-P