DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0511; Project Identifier AD-2020-01229-E]
RIN 2120-AA64

Airworthiness Directives; Williams International Co., L.L.C.
Turbofan Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

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SUMMARY: The FAA is revising a notice of proposed rulemaking (NPRM)
that applied to certain Williams International Co., L.L.C. (Williams)
FJ44-2A, FJ44-2C, FJ44-3A, and FJ44-3A-24 model turbofan engines. This
action revises the NPRM by expanding the applicability, updating the
estimated costs information, updating the compliance time, and adding
an installation prohibition. This action also revises the NPRM by
updating the service information references. The FAA is proposing this
airworthiness directive (AD) to address the unsafe condition on these
products. Since these actions would impose an additional burden over
those in the NPRM, the agency is requesting comments on this SNPRM.

DATES: The FAA must receive comments on this SNPRM by May 31, 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 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 SNPRM, contact Williams
International, Product Support, 2000 Centerpoint Parkway, Pontiac, MI
48341; phone: (800) 859-3544; website: http://www.williams-int.com/product-support.
You may view this service information at the FAA,
Chicago ACO, 2300 East Devon Avenue, Des Plaines, IL 60018. For
information on the availability of this material at the FAA, call (817)
222-5110.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0511; 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 SNPRM, any
comments received, and other information. The street address for Docket
Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Kyle Bush, Aviation Safety Engineer,
Chicago ACO, FAA, 2300 East Devon Avenue, Des Plaines, IL 60018; phone:
(847) 294-7870; email: kyle.bush@faa.gov.

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-2021-0511; Project Identifier
AD-2020-01229-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 again revise 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 proposed AD.

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 SNPRM 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 SNPRM, 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 SNPRM. Submissions containing CBI should
be sent to Kyle Bush, Aviation Safety Engineer, Chicago ACO, FAA, 2300
East Devon Avenue, Des Plaines, IL 60018. 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 issued an NPRM to amend 14 CFR part 39 by adding an AD that
would apply to Williams FJ44-2A, FJ44-2C, FJ44-3A, and FJ44-3A-24 model
turbofan engines. The NPRM published in the Federal Register on June
25, 2021 (86 FR 33579). The NPRM was prompted by a report of cracks in
the high-pressure turbine (HPT) disk posts and failure of an HPT disk
post, resulting in the contained fracture of an HPT disk post and
blade. Williams initiated an investigation to understand the root cause
of the cracks and to determine the necessary corrective action.
Metallurgical evaluation showed cracking related to intergranular
oxidation related to HPT disk post metal temperatures.
As a result of this investigation, Williams determined the root
cause of this cracking was due to higher HPT disk post temperatures and
a difference in manufacturing processes. Williams determined that these
cracks have only occurred on HPT disks with part number (P/N) 67093
installed on FJ44-2A or FJ44-2C model turbofan engines. Williams
subsequently published service information specifying procedures to
remove the HPT disk, P/N 67093. In the NPRM, the FAA proposed to
require removing the HPT disk, P/N 67093, from service before reaching
its new life limit and replacing it with a part eligible for
installation.

Actions Since the NPRM Was Issued

Since the FAA issued the NPRM, Williams notified the FAA that
revised service information was available. The revised service
information, Williams International Service Bulletin (SB) WISB-72-1032,
Revision 2, dated June 4, 2020, adds additional serial-numbered FJ44-
2A, FJ44-2C, and FJ44-3A model turbofan engines to the effectivity and
updates the compliance time for replacing the HPT disk. The FAA
determined that the additional
serial-numbered FJ44-2A, FJ44-2C, and FJ44-3A model turbofan engines
are susceptible to the same unsafe condition. Therefore, the FAA
revised the applicability of this proposed AD to include FJ44-2A, FJ44-
2C, FJ44-3A, and FJ44-3A-24 model turbofan engines with an engine
serial number identified in paragraph 1.A., Effectivity, of Williams
International SB WISB-72-1032, Revision 2, dated June 4, 2020, with an
installed HPT disk, P/N 67093. In addition, the FAA revised the
estimated number of affected engines installed on airplanes of U.S.
registry from 213 engines to 242 engines, updated the compliance time
specified in Table 1 to Paragraph (g), and added an installation
prohibition paragraph to this proposed AD. Finally, the FAA revised all
references to the service information in this AD.

Comments

The FAA received a comment from one commenter on the NPRM,
Williams. The following presents the comment received on the NPRM and
the FAA's response to the comment.

Request That the NPRM Reflect Current Service Document Revisions

Williams requested that the NPRM be revised to reflect the
specified procedures of the current service document revisions,
Williams International SB WISB-72-1032, Revision 2, dated June 4, 2020,
and Williams International SB WISB-72-1034, Revision 3, dated July 2,
2021.
The FAA agrees. The FAA has revised this proposed AD to include
Williams International SB WISB-72-1032, Revision 2, dated June 4, 2020,
and Williams International SB WISB-72-1034, Revision 3, dated July 2,
2021.

Other Differences Between This SNPRM and the NPRM

In this SNPRM, the FAA has replaced the term ``life limit'' with
``defined life cycles,'' where appropriate. In this SNPRM, the FAA has
replaced all instances of ``resulting in the release of an HPT blade''
to ``resulting in the contained fracture of an HPT disk post and
blade.''

FAA's Determination

The FAA is proposing this AD after determining the unsafe condition
described previously is likely to exist or develop in other products of
the same type design. Certain changes described above expand the scope
of the NPRM. As a result, it is necessary to reopen the comment period
to provide additional opportunity for the public to comment on this
SNPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Williams International SB WISB-72-1032, Revision
2, dated June 4, 2020. This service information specifies procedures
for removing and replacing the HPT rotor assemblies that include HPT
disk, P/N 67093. The service information also provides instructions for
incorporating the latest HPT combustor/fuel slinger module on FJ44-2A
and FJ44-2C model turbofan engines. 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 Williams International SB WISB-72-1034, Revision
3, dated July 2, 2021. This service information describes procedures
for re-identifying the HPT rotor assembly and HPT disk.

Proposed AD Requirements in This SNPRM

This proposed AD would require removing the HPT disk, P/N 67093,
from service before reaching defined cycle limits and replacing it with
a part eligible for installation.

Differences Between This SNPRM and the Service Information

The Accomplishment Instructions, paragraph 2.D., of Williams
International SB WISB-72-1032, Revision 2, dated June 4, 2020,
specifies procedures for replacing or reworking the HPT combustor/fuel
slinger module on FJ44-2A and FJ44-2C model turbofan engines, while
this proposed AD would not mandate that action. The FAA has determined
that replacement or rework of the HPT combustor/fuel slinger module is
not necessary to resolve the unsafe condition in this proposed AD.
The Accomplishment Instructions, paragraphs 2.C. and E. and 3.C.
and D., of Williams International SB WISB-72-1032, Revision 2, dated
June 4, 2020, specify procedures for removing and replacing the HP
turbine rotor assembly containing HPT disk, P/N 67093, whereas this
proposed AD would mandate removing and replacing the HPT disk, P/N
67093. Although removing the HPT rotor assembly is a necessary step in
the replacement of the HPT disk, this proposed AD only requires
replacement of the HPT disk to resolve the unsafe condition addressed
by this proposed AD.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 242 engines installed on airplanes of U.S. registry.
The FAA estimates the following costs to comply with this proposed
AD:

Estimated Costs

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some of the costs of this
proposed AD may be covered under warranty, thereby reducing the cost
impact on affected operators.

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

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: