Document ID: FAA-2022-1240-0005
Agency: faa
Document Type: Rule
Title: Airworthiness Directives: General Electric Company Turbofan Engines
Posted Date: 2023-04-05T04:00Z

[Federal Register Volume 88, Number 65 (Wednesday, April 5, 2023)]
[Rules and Regulations]
[Pages 20067-20070]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-07005]

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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; 
Amendment 39-22386; AD 2023-05-17]
RIN 2120-AA64

Airworthiness Directives; General Electric Company Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for 
certain General Electric Company (GE) GE90-76B, GE90-85B, GE90-90B, and 
GE90-94B model turbofan engines. This 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 
AD requires 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 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 AD requires replacing the HPT 
stage 2 nozzles. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective May 10, 2023.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of May 10, 
2023.

ADDRESSES: 
    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 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.
    Material Incorporated by Reference:
     For service information identified in this final rule, 
contact General Electric Company, GE Aerospace, 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. It is 
also available at regulations.gov by searching for and locating Docket 
No. FAA-2022-1240.

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: 

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 GE GE90-76B, 
GE90-85B, GE90-90B, and GE90-94B model turbofan engines. The NPRM 
published in the Federal Register on November 14, 2022 (87 FR 68113). 
The NPRM was prompted by 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. In the NPRM, the FAA proposed to 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, the FAA proposed to require replacement of the HPT 
stage 2 nozzles. The FAA is issuing this AD to address the unsafe 
condition on these products.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from 3 commenters. The commenters were 
Air France, The Boeing Company (Boeing), and United Airlines. Boeing 
supported the proposed AD without change. Air France requested changes 
to the proposed AD, and United Airlines requested confirmation on a 
calculation process. The following presents the comments received on 
the NPRM and the FAA's response to each comment.

Request To Revise Compliance Time

    Air France noted that affected engines with HPT stage 2 nozzles 
must be inspected whether or not they have reached the 22,000 hour 
threshold. The commenter requested that paragraphs (g)(1)(i) and (ii) 
be revised to both

[[Page 20068]]

require compliance before accumulating 250 flight cycles (FC) for all 
affected engines.
    The FAA disagrees with the request. Paragraph (g)(1)(ii) of this AD 
requires the operator to perform a borescope inspection before 
accumulating 22,000 flight hours (FH) since new or since last overhaul, 
or within 250 FCs after the effective date of this AD, whichever occurs 
later. This requirement provides the operator with an appropriate 
drawdown threshold for parts that are approaching 22,000 FHs since new 
or since last overhaul. The FAA did not change this AD as a result of 
this comment.

Request To Make Terminating Action Optional

    Air France requested that the Mandatory Terminating Action in 
paragraph (h) of this AD be revised to allow for the option to choose 
to replace the HPT Stage 2 nozzles when the engine is not in a 
performance restoration workscope shop visit or instead continue with 
the inspections required by this AD.
    The FAA disagrees with the request. The compliance time required by 
the mandatory terminating action is necessary to address the unsafe 
condition. The FAA did not change this AD as a result of this comment.

Request To Add GE Service Bulletin as a Difference Between This AD and 
the Service Information

    Air France noted that GE GE90 SB 72-1216, Initial Issue, dated 
August 22, 2022 (GE90 SB 72-1216) could have been referenced in the 
``Differences Between this Proposed AD and the Service Information'' 
paragraph of the NPRM because that service bulletin recommends to 
inspect affected engines when the HPT stage 2 nozzles have reached 
22,000 hours since new or overhaul.
    The FAA disagrees with the request. For affected engines with less 
than 22,000 FHs since new or overhaul, GE90 SB 72-1216 recommends 
performing the initial inspection before the engine accumulates 22,000 
FHs, whereas this AD requires performing the initial inspection before 
the engine accumulates 22,000 FHs or 250 FCs, whichever occurs later, 
to minimize unnecessary grounding of airplanes. This compliance time is 
not considered a major difference, and therefore, is not included 
within the ``Differences Between this AD and the Service Information'' 
section of the NPRM. The FAA did not change this AD as a result of this 
comment.

Request To Clarify Accepted FH Calculation

    United Airlines requested confirmation that calculation of FHs on 
HPT stage 2 nozzles based on shop records is acceptable for compliance 
with this AD. United Airlines noted that HPT stage 2 nozzles are not 
currently a tracked part and, therefore, the determination of 
accumulated FHs since new or since last overhaul would be based on shop 
records entered when the HPT stage 2 nozzles were either replaced or 
overhauled.
    The FAA agrees to clarify. The method of calculation presented by 
United Airlines, including the use of shop records when determining FHs 
on HPT stage 2 nozzles since new or since last overhaul, is acceptable 
for compliance with this AD. The FAA did not change this AD as a result 
of this comment.

Revision of Estimated Costs

    In this Final Rule, the FAA has moved the estimated costs 
associated with paragraphs (g)(3) and (h) from the on-condition costs 
section to the estimated costs section, since the replacement is 
required on-condition for a failed inspection and also as a mandatory 
terminating action. This revision does not increase the economic burden 
on operators.

Conclusion

    The FAA reviewed the relevant data and determined that air safety 
requires adopting this AD as proposed. Accordingly, the FAA is issuing 
this AD to address the unsafe condition on these products. Except for 
minor editorial changes, this AD is adopted as proposed in the NPRM.

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 the ADDRESSES section.

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.

Costs of Compliance

    The FAA estimates that this AD affects 8 engines installed on 
airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this 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.
Replace full set of HPT stage 2         8 work-hours x $85 per           918,650         919,330       7,354,640
 nozzles.                                hour = $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

[[Page 20069]]

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.

The Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 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:

2023-05-17 General Electric Company: Amendment 39-22386; Docket No. 
FAA-2022-1240; Project Identifier AD-2022-00683-E.

(a) Effective Date

    This airworthiness directive (AD) is effective May 10, 2023.

(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 parts 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, an ``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.

(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) 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

    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].

(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.

[[Page 20070]]

    (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 Aerospace, 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 March 9, 2023.
Christina Underwood,
Acting Director, Compliance & Airworthiness Division, Aircraft 
Certification Service.
[FR Doc. 2023-07005 Filed 4-4-23; 8:45 am]
BILLING CODE 4910-13-P