DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2019-0568; Project Identifier 2019-NE-20-AD; Amendment
39-21542; AD 2021-10-09]
RIN 2120-AA64

Airworthiness Directives; CFM International, S.A. 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 all
CFM International, S.A. (CFM) CFM56-5B and CFM56-7B model turbofan
engines with a certain high-pressure turbine (HPT) inner stationary
seal installed. This AD was prompted by cracks found in the rotating
air HPT front seal. This AD requires removal, inspection, and
replacement of the affected HPT inner stationary seal and, depending on
the findings, replacement of the rotating air HPT front seal, HPT rotor
blades, and No. 3 ball bearing. The FAA is issuing this AD to address
the unsafe condition on these products.

DATES: This AD is effective June 24, 2021.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of June 24,
2021.

ADDRESSES: For service information identified in this final rule,
contact CFM International Inc., Aviation Operations Center, 1 Neumann
Way, M/D Room 285, Cincinnati, OH 45125; phone: (877) 432-3272; fax:
(877) 432-3329; email: aviation.fleetsupport@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. It is also available at https://www.regulations.gov by
searching for and locating Docket No. FAA-2019-0568.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2019-0568; 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 McGuire, Aviation Safety
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803;
phone: (781) 238-7120; fax: (781) 238-7199; email:
chris.mcguire@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 all CFM CFM56-5B and
CFM56-7B model turbofan engines with a certain HPT inner stationary
seal installed. The NPRM published in the Federal Register on September
20, 2019 (84 FR 49487). The NPRM was prompted by a report that two
cracks were discovered on a CFM CFM56-5B model turbofan engine rotating
air HPT front seal during a routine engine shop visit. After
investigation, CFM determined that the HPT inner stationary seal, part
number 1808M56G01, may not have received the correct braze heat treat
cycle at the time of the honeycomb replacement. As a result, the
affected HPT inner stationary seal could lead to a localized separation
of the replaced honeycomb, which may reduce the life of the rotating
air HPT front seal. In the NPRM, the FAA proposed to require removal,
inspection, and replacement of the affected HPT inner stationary seal
and, depending on the findings, replacement of the rotating air HPT
front seal, HPT rotor blades, and No. 3 ball bearing. 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 nine commenters. The commenters were
Air Line Pilots Association, International (ALPA); American Airlines
(AAL); Azur Aviation (Azur); The Boeing Company (Boeing); CFM; Delta
Air Lines, Inc. (Delta); United Airlines (UAL); MTU Maintenance Canada
(MTU) and Magnetic MRO. Four of the nine commenters requested changes
that resulted in updates to this AD. Three commenters requested
clarification on definitions. Two commenters requested updates to the
service information. Two commenters expressed support for the AD. The
following presents the comments received on the NPRM and the FAA's
response to each comment.

Request To Clarify Parts That Can Be Returned to Service

Azur requested that the FAA clarify the parts that can be returned
to service after removal. Azur reasoned that paragraph (g)(1) of this
AD requires that an HPT inner stationary seal be removed from service
and replaced with either a part that is not listed in the service
information or a repaired part identified in paragraph (h)(2),
Definitions, of this AD. In contrast, paragraphs (g)(3)(i) and (iii) of
this AD, respectively, indicate only to remove the rotating air HPT
front seal and No. 3 ball bearing from service and replace them with a
``part eligible for installation.''
Azur suggested adding one of the following to this AD to remove the
ambiguity: (1) Remove ``remove from service'' from paragraph (g)(1) of
this AD; (2) Identify rotating air HPT front seals and No. 3 ball
bearings that are not eligible for installation; (3) Add an
``Installation Prohibition'' paragraph for the removed rotating air HPT
front seal and No. 3 ball bearing; (4) Indicate what to do with the
removed rotating air HPT front seal and No. 3 ball bearing in
paragraphs (g)(3)(i) and (iii) of this AD, such as discard these parts;
or (5) Identify instruction for the removed rotating air HPT front
seals and No. 3 ball bearings.
Use of ``remove from service'' in this AD indicates that the
rotating air HPT front seal and No. 3 ball bearing should no longer be
installed on an engine. Therefore, neither the removed rotating air HPT
front seal nor the removed No. 3 ball bearing can be repaired and
returned to service. The FAA, however, updated paragraph (h),
Definitions, of this AD, to clarify that a part eligible for
installation for both a rotating air HPT front seal and a No. 3 ball
bearing refers to parts that were not removed from service based on the
findings of honeycomb separation of the HPT inner stationary seal. The
FAA also updated paragraph (g)(1) of this AD to remove ``remove from
service'' to clarify that the HPT inner stationary seal can be repaired
and returned to service. The FAA also moved the definition of an HPT
inner stationary seal that is eligible for installation from paragraph
(g)(1) to paragraph (h)(1) of this AD.

Request To Update the Definition of Engine Shop Visit

AAL, Delta, and UAL requested updates or clarification of the
definition of an ``engine shop visit'' provided in paragraph (h)(1) of
this AD.
AAL requested that the FAA update the definition of an engine shop
visit to clarify circumstances that are not an engine shop visit. AAL
reasoned that CFM Service Bulletin (SB) CFM56-7B S/B 72-0972 provides
guidance on when AD mandated actions can be accomplished to avoid undue
burden on operators, specifically in circumstances when engines are
inducted to the shop for quick corrective action, such as repair for
foreign object damage.
UAL requested that the FAA update the definition of an engine shop
visit to specify which major mating engine case flanges need to be
separated to be an engine shop visit as defined. UAL stated that the
ambiguity of the ``major mating engine case flange'' may result in an
inspection of the HPT inner stationary seal for honeycomb separation
when the core is not exposed, such as during fan case replacement.
Delta recommended that the manufacturer define ``engine shop
visit'' in its service information.
The FAA agrees that the definition of an engine shop visit in this
AD does not include the separation of engine flanges solely for the
purpose of transportation of the engine or replacing the fan or
propulsor without subsequent maintenance. All other separations of
major mating engine case flanges are an engine shop visit, as defined,
and require removal, replacement, and inspection of the HPT inner
stationary seal as required by paragraphs (g)(1) and (2) of this AD.
The FAA changed the definition of ``engine shop visit'' in paragraph
(h) this AD to clarify the definition of an engine shop visit.
The FAA did not revise this AD in response to Delta's comment. The
FAA notes, however, that in CFM Service Bulletin (SB) CFM56-5B S/B 72-
0952, Revision 01, and CFM SB CFM56-7B S/B 72-1054, Revision 01, both
dated January 15, 2020, the manufacturer updated the SBs to clarify
that the quick turn shop visit type is not included in the SB's
definition of ``shop visit.''
Request To Change Inspection of HPT Rotor Blade To Remove Debris
AAL requested that the FAA change paragraph (g)(3)(ii) of this AD
to ``Remove the HPT rotor blade from service and inspect per CFM56-7B
CFMI-TP.SM.10 Engine Shop Manual (ESM) 72-52-01-09 High Pressure
Turbine Rotor Blades--Inspection 001 or replace with parts eligible for
installation.'' AAL reasoned that the HPT rotor blade collects various
types of debris over its service life, so attempting to determine if
the debris is honeycomb material based upon a general visual inspection
is subjective and open to interpretation. Therefore, AAL suggested that
removing the HPT rotor blades would ensure that the repair facility
could remove the debris in the internal cavities and return the HPT
rotor blades to service.
Since the NPRM was published, the manufacturer revised the service
information, removing the inspection of the HPT rotor blade internal
cavities for honeycomb metal debris. As a result, the FAA changed
paragraph (g)(3)(ii) of this AD to eliminate the requirement to inspect
the HPT rotor blade internal cavities for honeycomb metal debris. The
FAA also removed the estimated cost associated with the inspection of
the HPT rotor blade internal cavities for honeycomb metal debris from
this AD.

Request To Clarify Reason To Replace No. 3 Ball Bearing

Magnetic MRO requested clarification for the reason to replace the
No. 3 ball bearing if metal debris is found in the HPT blade cavities.
In the NPRM, the FAA proposed to require replacement of the No. 3
ball bearing if honeycomb separation was found during the inspection
required by paragraph (g)(2) of this AD. The replacement of the No. 3
ball bearing is not linked to a finding of debris in the HPT rotor
blade internal cavities but is required if honeycomb separation is
found. Honeycomb separation results in increased secondary air flow
impinging on the rotating air HPT front seal, which increases the axial
load on the No. 3 ball bearing. This increased axial load impacts the
durability of the No. 3 ball bearing. The FAA did not change this AD
based on this comment.

Request To Add a Terminating Action

AAL requested that the FAA update paragraph (g)(1) of this AD to
include, ``Accomplishment of these instructions are considered
terminating action to this AD.'' AAL reasoned that this statement
provides specific closure since the corrective action has been clearly
defined and approved by the FAA. AAL suggested this maintenance action
is not recurring and, as such, would constitute an appropriate
terminating action.
The FAA disagrees with adding the terminating action statement.
Performing the actions required by this AD achieves compliance with
this AD. A statement of terminating action is unnecessary.

Request To Clarify Compliance

MTU commented that this AD describes actions to be performed if
damage is found, but does not describe actions to be performed when
damage is not found as specified in CFM SB CFM56-7B S/B 72-1054,
Revision 01, dated January 15, 2020. MTU asked if the AD could
reference action that needs to be performed when the engine is inducted
and disassembled for reasons other than HPT inner stationary seal issue
and damage (or no damage) is found.
The FAA disagrees with requiring actions that are not related to
the unsafe condition described in this AD. The HPT inner stationary
seal is not typically exposed unless the engine is undergoing an engine
shop visit. However, if damage to the HPT inner stationary seal is
found during inspections not related to this AD, the ESM provides
criteria to determine appropriate action.
Request To Incorporate AC 20-176A in Service Information
AAL and Delta requested that CFM incorporate AC 20-176A into both
CFM SB CFM56-5B S/B 72-0952, Revision 01, dated January 15, 2020, and
CFM SB CFM56-7B S/B 72-1054, Revision 01, dated January 15, 2020, for
the purpose of ``. . . distinguishing which steps in an SB will have a
direct effect on detecting, preventing, resolving, or eliminating the
unsafe condition identified in an AD.'' The commenters reasoned that
CFM should identify the steps required for compliance (RC) in the
service information. AAL added that the RC designation reduces global
AMOCs and streamlines the accomplishment of key tasks while meeting
strict regulatory compliance.
The FAA agrees that adding the RC designation to the required
service information steps provides clarity to the operators. CFM added
the RC designation to CFM SB CFM56-5B S/B 72-0952, Revision 01, dated
January 15, 2020, and CFM SB CFM56-7B S/B 72-1054, Revision 01, dated
January 15, 2020. The FAA did not change this AD.

Request To Update References to the ESM

Delta requested that the FAA update paragraphs (c)(2) and (h)(2) of
this AD to reference the CFM56-5B ESM and the CFM56-7B ESM entirely,
rather than specific repair tasks within the ESMs. Delta reasoned that
the CFM56-5B ESM and CFM56-7B ESM might change in future revisions.
The FAA disagrees with changing the references from the specific
repair tasks. Paragraph (c)(2), Applicability, and paragraph (h)(2),
Definitions, of this AD refer to specific repair tasks within CFM56-5B
ESM and CFM56-7B ESM that are required to return a HPT inner stationary
seal to service. The FAA did not change this AD, but will consider
requests for AMOCs if the repair tasks change in future revisions of
the ESM.

Comment on Revising Service Information

CFM stated that they would update CFM SB CFM56-5B S/B 72-0952 and
CFM SB CFM56-7B S/B 72-1054 based on feedback from operators. CFM
indicated it would update the definition of ``shop visit'' to clarify
that replacing a fan disk is not considered a shop visit. CFM further
indicated that it would clarify that if honeycomb separation is found,
then the HPT blades may be scrapped or overhauled. Finally, CFM noted
that it would revise the SBs by adding ``RC'' to those tasks required
for compliance.
The FAA notes that it has revised this AD by referring to CFM SB
CFM56-5B S/B 72-0952, Revision 01, dated January 15, 2020, and CFM SB
CFM56-7B S/B 72-1054, Revision 01, dated January 15, 2020. In addition,
the FAA has reviewed the changes included in Revision 01 of these SBs
and determined that these are clarifying changes only and impose no
additional burden to operators.
Request To Allow Use of Later Revisions of Service Information
AAL and Delta requested that the FAA add the phrase ``or later''
when referencing the service information in this AD. AAL stated that
specifying ``or later'' could prevent numerous requests for alternative
methods of compliance (AMOCs) if the manufacturer revises the service
information. AAL also stated that this request aligns with paragraph 2-
3.d of Advisory Circular No. 20-176A, ``Service Bulletins Related to
Airworthiness Directives and Indicating FAA Approval on Service
Documents,'' dated June 16, 2014 (AC 20-176A).
The FAA disagrees with adding language that allows the use of later
revisions of service information when performing the required actions
of this AD. Later revisions of the service information have not been
reviewed by the FAA. As noted, however, in a previous comment response,
the FAA has revised this AD by referring to the latest published
revisions of the referenced service information.
Support for No Reporting Requirement
AAL expressed support for the No Reporting Requirement in paragraph
(i) of this AD.

Support for the AD

ALPA and Boeing expressed support for the AD as written.

Conclusion

The FAA reviewed the relevant data, considered any comments
received, 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 and any
other changes described previously, this AD is adopted as proposed in
the NPRM. None of the changes will increase the economic burden on any
operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed CFM SB CFM56-5B S/B 72-0952, Revision 01, dated
January 15, 2020, and CFM SB CFM56-7B S/B 72-1054, Revision 01, dated
January 15, 2020. CFM SB CFM56-5B S/B 72-0952, Revision 01, describes
procedures for repairing the CFM56-5B turbofan engine HPT inner
stationary seal honeycomb. CFM SB CFM56-7B S/B 72-1054, Revision 01,
describes procedures for repairing the CFM56-7B turbofan engine HPT
inner stationary seal honeycomb. 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.

Costs of Compliance

The FAA estimates that this AD affects 210 engines installed on
airplanes of U.S. registry. Operators have the option to replace or
repair the affected HPT inner stationary seal. The part cost is for
replacement with a repaired HPT inner stationary seal.
The FAA estimates the following costs to comply with this AD:

Estimated Costs

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

On-Condition Costs

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.

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

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]

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