[Federal Register Volume 87, Number 78 (Friday, April 22, 2022)]
[Rules and Regulations]
[Pages 24025-24029]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-08562]



========================================================================
Rules and Regulations
                                                Federal Register
________________________________________________________________________

This section of the FEDERAL REGISTER contains regulatory documents 
having general applicability and legal effect, most of which are keyed 
to and codified in the Code of Federal Regulations, which is published 
under 50 titles pursuant to 44 U.S.C. 1510.

The Code of Federal Regulations is sold by the Superintendent of Documents. 

========================================================================


Federal Register / Vol. 87, No. 78 / Friday, April 22, 2022 / Rules 
and Regulations

[[Page 24025]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0692; Project Identifier MCAI-2019-00140-E; 
Amendment 39-22016; AD 2022-08-13]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney Canada Corp. Turboprop 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

-----------------------------------------------------------------------

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all 
Pratt & Whitney Canada Corp. (P&WC) PT6A-34, -34B, -34AG, -114, and -
114A model turboprop engines. This AD was prompted by several reports 
of low-time fractures of compressor turbine (CT) blades resulting in 
loss of power or in-flight shutdown (IFSD) of the engine. This AD 
requires replacement of certain CT vanes. This AD also requires removal 
from service of certain CT blades when these blades have been operated 
with certain CT vanes. The FAA is issuing this AD to address the unsafe 
condition on these products.

DATES: This AD is effective May 27, 2022.

ADDRESSES: 

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0692; 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, the 
mandatory continuing airworthiness information (MCAI), 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: Barbara Caufield, Aviation Safety 
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; 
phone: (781) 238-7146; fax: (781) 238-7199; email: 
<a href="/cdn-cgi/l/email-protection#9af8fbe8f8fbe8fbb4f9fbeffcf3fff6fedafcfbfbb4fdf5ec"><span class="__cf_email__" data-cfemail="a7c5c6d5c5c6d5c689c4c6d2c1cec2cbc3e7c1c6c689c0c8d1">[email protected]</span></a>.

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 P&WC PT6A-34, -34B, 
-34AG, -114, and -114A model turboprop engines. The NPRM published in 
the Federal Register on August 17, 2020 (85 FR 49981). The NPRM was 
prompted by several reports of low-time fractures of CT blades 
resulting in loss of power or IFSD of the engine. In the NPRM, the FAA 
proposed to require replacement of certain CT vanes. The NPRM also 
proposed to require the removal from service of certain CT blades when 
these blades have been operated with certain CT vanes. The FAA is 
issuing this AD to address the unsafe condition on these products.
    Transport Canada, which is the aviation authority for Canada, has 
issued Transport Canada AD CF 2019-30R1, dated December 17, 2019 
(referred to after this as ``the MCAI''), to address the unsafe 
condition on these products. The MCAI states:

    There have been several reported events of low time CT blade 
fractures resulting in power loss/In-flight shutdown (IFSD) on post 
P&WC Service Bulletin (SB) 1669 configured PT6A-114 engines, 
featuring new CMSX-6 CT blades. In addition, relatively low time 
failures of Non-P&WC CT blades have also been reported on PT6A-34 
and -114 series engines.
    In service data shows that these low time failures were reported 
on engines that had CT vanes installed that were repaired in 
accordance with repair specification number STI 72-50-254 held by 
Southwest Turbine Inc. (STI). Most of the affected engines are 
installed on single-engine powered aeroplanes and some events have 
resulted in the loss of the aeroplane and fatalities.
    Dimensional checks and operational testing of the subject STI 
repaired CT vane removed from an incident engine, revealed that it 
did not conform to the engine manufacturer's CT vane type design 
criteria. The noted variations and features in the STI repaired CT 
vane can cause airflow distortion and subsequent aerofoil excitation 
of the CT blades resulting in High Cycle Fatigue (HCF) failure of 
the CT blades. Test data indicates that the stress levels induced in 
CT blades by the adverse effect of subject airflow distortion 
exceeds the design requirements for CMSX-6 CT blades.
    An IFSD or loss of power on a single-engine powered aeroplane 
under certain conditions can lead to an unsafe condition as seen in 
some past events. [Transport Canada] AD CF-2019-30 was issued on 19 
August 2019 to address the potential hazard of power loss/IFSD as a 
result of CT blade failures on engines with CT vanes installed that 
were repaired in accordance with repair specification number STI 72-
50-254.
    This [Transport Canada] AD revision, CF-2019-30R1, is issued to 
update the background information and to clarify the affected P&WC 
CT blade Part Numbers (P/Ns).

    You may obtain further information by examining the MCAI in the AD 
docket at https://www.regulations.gov by searching for and locating 
Docket No. FAA-2020-0692.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from 13 commenters. The commenters were 
Southwest Turbine Inc. (STI), an individual commenter, and 11 anonymous 
commenters. The following presents the comments received on the NPRM 
and the FAA's response to each comment.

Request To Revise Required Actions

    STI requested that the FAA revise the reference in paragraph 
(g)(1)(i), Required Actions, of this AD from ``. . . non-STI-repaired 
CT vane'' to ``. . . non-STI 72-50-254 repaired CT vane. . .'' The 
commenter reasoned that this AD specifically addresses CT vanes 
repaired using STI Repair Specification STI 72-50-254 (STI 72-50-254). 
Therefore, operators should be allowed to install CT vanes not repaired 
using STI 72-50-254 and repaired within STI's current FAA rating. 
Additionally, STI reasoned that this change would mirror the language 
in the Corrective Actions, paragraph 1, of Transport Canada AD CF-2019-
30R1.
    The FAA agrees and updated paragraph (g)(1)(i) of this AD to refer 
to CT vanes not repaired using STI 72-50-254. This change places no 
additional burden on operators who are required to comply with this AD.

[[Page 24026]]

Request To Remove Engines From Applicability

    STI requested that the FAA remove P&WC PT6A-34, -34B, and -34AG 
model turboprop engines from paragraph (c), Applicability, of this AD. 
The commenter reasoned that of the 20 P&WC CMSX-6 CT blade failures, 
only six blade failures occurred with STI 72-50-254 repaired CT vanes 
installed. Those six blade failures occurred on engines with CT vanes 
repaired using STI 72-50-254, which were installed in P&WC PT6A-114A 
model turboprop engines.
    In addition, the commenter suggested that the only STI-repaired CT 
vane installed on engines that has experienced CT blade failures was CT 
vane part number (P/N) 3029051. The commenter continued that CT vane, 
P/N 3029051, is not eligible for installation in P&WC PT6A-34, -34B, 
and -34AG model turboprop engines, and therefore, these model engines 
should be removed from the applicability of this AD.
    STI cited Docket No. FAA-2013-0766 (AD 2014-17-08, 79 FR 52172, 
September 3, 2014), which was superseded by AD 2014-17-08R1, (80 FR 
24791, May 1, 2015), and the FAA's responses to public comments in the 
preamble of these ADs. While referencing these ADs, STI underlined 
specific portions of public comments involving the P&WC CMSX-6 CT blade 
being an unproven CT blade replacement that has experienced low-time 
failures and has been identified for removal in P&WC PT6A-34 model 
turboprop engines. STI indicated that the FAA acknowledged the failure 
mode in other P&WC engines, specifically including PT6A-34 turboprop 
engines, was well understood and stated there have been no failures of 
P&WC CMSX-6 CT blades in PT6A-34 turboprop engines with STI 72-50-254 
repaired CT vanes. STI commented that, for these reasons, the STI 72-
50-254 repaired CT vane rings cannot be the cause of PWC CMSX-6 CT 
blade failures in PT6A-34 series engines.
    The FAA disagrees. The FAA recognizes that STI-repaired CT vane P/N 
3029051 is not eligible for installation in P&WC PT6A-34, -34B, and -
34AG model turboprop engines. The FAA notes, however, that an 
additional affected part-numbered STI-repaired vane is eligible for 
installation in P&WC PT6A-34, -34B, and -34AG model turboprop engines. 
In addition, CT blade failures have occurred with STI-repaired CT vanes 
installed in P&WC PT6A-34, -34B, and -34AG model turboprop engines and 
are susceptible to the unsafe condition of this AD. Further, Table 2 of 
Southwest Turbine Repair, Inc., STI 72-50-254, Revision 08, dated April 
14, 2019, lists P&WC PT6A-34, -34B, -34AG model turboprop engines as 
eligible for this repair.
    The FAA issued AD 2014-17-08 (79 FR 52172, September 3, 2014) and 
AD 2014-17-08R1 (80 FR 24791, May 1, 2015) to require replacement of 
P&WC IN100 CT blades with P&WC CMSX-6 CT blades. Although there have 
been failures of the P&WC CMSX-6 CT blades with CT vanes not repaired 
by STI, the FAA has found the failure rate of CT blades with CT vanes 
not repaired by STI to be approximately one-tenth of those that were 
repaired by STI.

Request To Restrict Applicability to Certain CT Blades

    STI requested that the FAA revise paragraph (c), Applicability, of 
this AD to indicate removal of STI 72-50-254 repaired CT vanes should 
not apply to engines operating with pre-P&WC SB PT6A-72-1669 and pre-
P&WC SB PT6A-72-1690 IN100 CT blades. The commenter reasoned that the 
MCAI and the NPRM addressed the unsafe condition of failure of P&WC 
CMSX-6 CT blades. The commenter stated that the AD should not require 
STI 72-50-254 repaired CT vanes to be removed when operated with P&WC 
IN100 CT blades.
    The FAA disagrees with revising paragraph (c), Applicability, of 
this AD to limit the AD applicability to turboprop engines with certain 
CT blades installed. Although most CT blades failures have occurred 
with P&WC CMSX-6 CT blades installed, the FAA's data indicate that 
several P&WC IN100 CT blade failures occurred with STI-repaired CT 
vanes before incorporating procedures in P&WC SB PT6A-72-1669 and P&WC 
SB PT6A-72-1690. Consequently, this AD requires that any CT vane with 
P/N 3029051, 3032151, or 3123001 repaired in accordance with STI 72-50-
254 be removed from service.

Request To Restrict Applicability by CT Vane Part Number

    STI requested that the FAA update paragraph (c), Applicability, of 
this AD to indicate that only STI 72-50-254 repaired CT vanes P/N 
3029051 or P/N 3123001 are affected by this AD. STI reasoned that all 
the P&WC CMSX-6 CT blade failures that they are aware of occurred in 
PT6A-114A engines operating with STI 72-50-254 repaired CT vane P/N 
3029051. STI continued that there is no evidence that identifies 
discrepant conditions or CT blade failures with any other part numbered 
STI 72-50-254 repaired CT vanes.
    The FAA disagrees that only STI 72-50-254 repaired CT vanes P/N 
3029051 or 3123001 are affected by the unsafe condition addressed by 
this AD. The FAA has reviewed data that shows failures of another CT 
vane P/N in addition to the two P/Ns referenced by the commenter. In 
response to this comment, the FAA updated paragraph (g)(1)(i), Required 
Actions, of this AD to require the removal from service of any affected 
CT vane, P/N 3029051, 3032151, or 3123001, repaired in accordance with 
STI 72-50-254.

Request To Require Installation of Dampers/Dampeners

    STI, an individual commenter, and two anonymous commenters 
suggested that the FAA require operators install under platform seals 
(dampers or dampeners) introduced by P&WC SB PT6A-72-1769, dated 
December 21, 2015. One commenter reasoned that of the 20 CMSX-6 CT 
blade fatigue failures that have occurred, none had occurred when 
dampeners were installed. Based on a study and testing by P&WC, the 
commenter determined that the dampeners appeared to have solved the 
ongoing problem of P&WC CMSX-6 CT blade failures, regardless of which 
CT vane was installed. The commenter suggested that the FAA withdraw 
the NPRM and replace it with an AD requiring the installation of the 
dampeners.
    An anonymous commenter and an individual commenter referred to P&WC 
documentation in which P&WC indicated that failures of P&WC CMSX-6 CT 
blades in normal operation were caused by vibratory stress, and the 
previous generation of CT blades did not exhibit this problem. To 
reduce these vibratory stresses, P&WC introduced dampers. The two 
commenters suggested requiring dampers and CT vane clocking to reduce 
vibratory stresses.
    The FAA disagrees with the suggestion to require operators to 
install under platform seals to address the unsafe condition. Although 
data suggest dampeners and clocking reduce vibratory stresses, 
dampeners and clocking do not eliminate the unsafe condition caused by 
the installation of the STI-repaired CT vanes.

Comments on Root Cause of CT Blade Failure

    An individual commenter questioned whether Transport Canada CF-
2019-30R1, the MCAI on which the FAA's NPRM is based, tested a 
representative sample of affected CT blades and

[[Page 24027]]

whether the root cause of the unsafe condition was determined 
accurately. The commenter suggested that the MCAI is based on testing 
of a single STI-repaired CT vane from an engine that suffered 
catastrophic CT blade failure during an engine test run following an 
overhaul. The commenter stated that P&WC engineers documented that the 
root cause of the CT blade failure was undetermined and that the STI-
repaired CT vane was not a representative sample due to sustained 
damage.
    An anonymous commenter noted that of the 16 P&WC CMSX-6 blade 
failures, 11 had P&WC CT vanes installed. The commenter stated that 
this equates to an approximate 70% failure rate with the P&WC CT vanes. 
The commenter questioned how a CT vane made by an alternate supplier 
can be blamed as the cause of these failures.
    The FAA disagrees with these comments. The MCAI and this AD are not 
based exclusively on testing of a single STI-repaired CT vane. 
Transport Canada and the FAA reviewed data from 38 CT blade failure 
events prior to issuance of the MCAI and this AD. The relative rates of 
CT blade failure are not simply the ratio of the number of events, but 
also includes the number of engines with each part type installed. 
Although there have been failures of the P&WC CMSX-6 CT blades with 
non-STI repaired CT vanes installed, the FAA has found the failure rate 
of CT blades with non-STI repaired CT vanes to be approximately one-
tenth of the failure rate of those that were repaired by STI.

Comments That the P&WC CMSX-6 CT Blades Are the Cause of Failures

    Several anonymous commenters and an individual commenter cited the 
history of P&WC CMSX-6 CT blade failures and the resulting P&WC service 
bulletins involving procedures to inspect and replace the CT blades. 
The commenters stated these failures occurred with factory manufactured 
zero-time P&WC model engines and engines in operation with both P&WC CT 
vanes and STI-repaired CT vanes installed. According to an individual 
commenter, the evidence to condemn the STI-repaired CT vane would also 
apply to the P&WC CT vane. Considering that factory manufactured, zero-
time P&WC engines have experienced CT blade failures, the commenters 
concluded that unsafe condition with these blades cannot be the result 
of a repair process.
    Further, an anonymous commenter referenced a 2018 case in Dallas 
County, Texas involving P &WC. The commenter summarized the case to 
include blade development and problems encountered from coating cracks 
migrating into the base material, gap platform, vibratory stress near 
the operating rotational speed of the engine and other areas of concern 
with the CT blade development. The commenter recommended that the FAA 
review Analytical Summary D9297 (P&WC 008643-008680), and Analytical 
Summary E7739, dated September 24, 2013 (P&WC 008599-008617), which, 
the commenter states, both determined the problem to be the CT blade.
    An anonymous commenter suggested that the FAA demand all documents 
relating to the process and development of the P&WC CMSX-6 CT blade to 
include testing, emails, minutes of meetings, and any sworn testimony 
given, prior to deciding on the proposed AD. The commenter suggested 
that the CT blade is the root cause of the failures, the manufacturer 
is dictating the AD, and the manufacturer is going after a competitor.
    STI cited National Transportation Safety Board (NTSB) Report, No. 
WPR14FA024, dated October 14, 2015, which detailed an October 21, 2013 
failure involving an STI 72-50-254 repaired CT vane. STI commented that 
NTSB made no findings that indicated STI 72-50-254 repaired CT vane 
contributed to the event.
    An anonymous commenter stated they had a P&WC PT6A-114A model 
turboprop engine undergoing overhaul and 18 P&WC CMSX-6 CT blades 
failed the process compensated resonance testing per P&WC SB PT6A-72-
1762. The commenter suggested that these failures indicate that there 
is a design flaw or quality escape with P&WC CMSX-6 CT blades.
    The FAA does not agree with the commenters that there is an unsafe 
condition affecting the P&WC CT blades. The FAA has reviewed event 
reports, analyses, and test reports to make this determination.

Request To Consider Inaccuracy Tolerance

    STI requested that the FAA consider an inaccuracy tolerance of 30% 
when reviewing test data. STI cited P&WC report E8093 that indicates a 
30% variance in repeatability of non-intrusive stress measurement 
(NSMS) CT blade tip deflection of a P&WC CT vane. STI suggested that 
P&WC retest prior configurations to determine the cause of variation in 
repeatability.
    The FAA disagrees to consider inaccuracy tolerance. P&WC examined 
three STI-repaired CT vanes via dimensional inspection, one of which 
was also tested using Non-intrusive Stress Measurement System (NSMS), 
and determined the STI-repaired CT vanes did not meet P&WC's type 
design criteria. The STI-repaired CT vane that P&WC tested had 
scratches not exceeding a depth of 0.5 mils that did not alter the 
dimensional aspects of the CT vane casting and assembly when measured 
and did not preclude the engine from running during the NSMS testing.

Question About the Number of CT Blade Failures

    An anonymous commenter asked how many CT blade failures have 
occurred after incorporating P&WC SB PT6A-72-1768 and P&WC SB PT6A-72-
1769. Another anonymous commenter asked how many CT blade failures on 
turboprop engines, equipped with CT vane P/N 3079351-01, which is the 
third generation of single crystal blade used by P&WC in the affected 
engines, have occurred after incorporating P&WC SB PT6A-72-1749.
    The FAA notes that no known failures of CT blades have occurred 
after incorporating P&WC SB PT6A-72-1768, P&WC SB PT6A-72-1769, or P&WC 
SB PT6A-72-1749.

Comment About Repair Variation in P&WC CT Vanes

    STI commented that P&WC regularly returns to service overhauled CT 
vanes that exhibit greater variation in repair than that of STI-
repaired CT vanes. STI stated that P&WC's inspection requirements for 
new CT vanes are different than overhauled CT vanes, and deviating 
features found on P&WC's overhauled CT vanes are not inspected prior to 
release.
    The FAA cannot confirm STI's comment regarding P&WC's returned-to 
service part variation. Most engine new-part inspection specifications 
differ from those for used or overhauled parts. As stated in an earlier 
comment reply, the FAA reviewed data from 38 CT blade failure events to 
address the unsafe condition in this AD. Although there have been 
failures of CT blades with CT vanes not repaired by STI, the FAA has 
found the failure rate of CT blades with CT vanes not repaired by STI 
is approximately one-tenth of those that were repaired by STI.

Comment About Original Equipment Manufacturer (OEM) Regulating the 
Regulators

    Two anonymous commenters suggested that this AD is an example of 
the OEM regulating the regulators.
    The FAA disagrees. The data reviewed by the FAA shows that CT blade 
stresses are significantly higher in engines with STI-repaired CT 
vanes,

[[Page 24028]]

compared to those with P&WC CT vanes installed. In addition, event data 
reviewed by the FAA shows that CT blade failure events are 
approximately 10 times greater in engines equipped with STI-repaired CT 
vanes as opposed to P&WC CT vanes.

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

    The FAA reviewed Southwest Turbine Repair, Inc., STI 72-50-254, 
Revision 08, dated April 14, 2019. This service information describes 
procedures for repair of the compressor turbine vane ring assembly.

Costs of Compliance

    The FAA estimates that this AD affects 907 engines installed on 
airplanes of U.S. registry. The FAA estimates that 63 engines will need 
to replace the CT vanes and CT blades.
    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
----------------------------------------------------------------------------------------------------------------
Remove and replace CT vanes...........  16 work-hours x $85 per         $115,789        $117,149      $7,380,387
                                         hour = $1,360.
Remove and replace CMSX-6 CT blade set  16 work-hours x $85 per          $90,271         $91,631      $5,772,753
                                         hour = $1,360.
----------------------------------------------------------------------------------------------------------------

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 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:

2022-08-13 Pratt & Whitney Canada Corp.: Amendment 39-22016; Docket 
No. FAA-2020-0692; Project Identifier MCAI-2019-00140-E.

(a) Effective Date

    This airworthiness directive (AD) is effective May 27, 2022.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all Pratt & Whitney Canada Corp. PT6A-34, -
34B, -34AG, -114, and -114A model turboprop engines.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by several reports of low-time fractures of 
compressor turbine (CT) blades resulting in loss of power or in-
flight shutdown of the engine. The FAA is issuing this AD to prevent 
failure of the CT blade. The unsafe condition, if not addressed, 
could result in failure of the engine, in-flight shutdown, and loss 
of the airplane.

(f) Compliance

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

(g) Required Actions

    (1) Within 250 flight hours (FHs) or 270 days after the 
effective date of this AD, whichever occurs first:
    (i) Remove from service any CT vane, part number (P/N) 3029051, 
3032151, or 3123001, repaired in accordance with Southwest Turbine 
Inc. (STI) Repair Specification STI 72-50-254 (STI 72-50-254) and 
replace with a non-STI 72-50-254 repaired CT vane.
    (ii) Remove from service any CMSX-6 CT blade that has been 
operated on an affected engine with any CT vane repaired in 
accordance with STI 72-50-254.
    (2) [Reserved]

(h) Installation Prohibition

    After the effective date of this AD, do not install on any 
engine a CT vane, P/N 3029051, 3032151, or 3123001, that was 
repaired in accordance with STI 72-50-254.

(i) 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 
ECO Branch, send it to the attention of the person identified in 
paragraph (j)(1) of this AD. You may email your request to: <a href="/cdn-cgi/l/email-protection#3879767d15797c157975777b785e5959165f574e"><span class="__cf_email__" data-cfemail="50111e157d11147d111d1f13103631317e373f26">[email protected]</span></a>.
    (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.

[[Page 24029]]

(j) Related Information

    (1) For more information about this AD, contact Barbara 
Caufield, Aviation Safety Engineer, ECO Branch, FAA, 1200 District 
Avenue, Burlington, MA 01803; phone: (781) 238-7146; fax: (781) 238-
7199; email: <a href="/cdn-cgi/l/email-protection#c0a2a1b2a2a1b2a1eea3a1b5a6a9a5aca480a6a1a1eea7afb6"><span class="__cf_email__" data-cfemail="24464556464556450a474551424d414840644245450a434b52">[email protected]</span></a>.
    (2) Refer to Transport Canada AD CF 2019-30R1, dated December 
17, 2019, for more information. You may examine the Transport Canada 
AD in the AD docket at https://www.regulations.gov by searching for 
and locating Docket No. FAA-2020-0692.

(k) Material Incorporated by Reference

    None.

    Issued on April 7, 2022.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2022-08562 Filed 4-21-22; 8:45 am]
BILLING CODE 4910-13-P


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