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.

Rules and Regulations Federal Register

24025 

Vol. 87, No. 78 

Friday, April 22, 2022 

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 inflight 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: barbara.caufield@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 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 singleengine 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. 


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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 lowtime 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 STIrepaired 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 


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whether the root cause of the unsafe 

condition was determined accurately. 

The commenter suggested that the 

MCAI is based on testing of a single STIrepaired 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 nonintrusive 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 newpart 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, 


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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

Action Labor cost Parts cost Cost per 

product 

Cost on U.S. 

operators 

Remove and replace CT vanes ...................... 16 work-hours × $85 per hour = $1,360 ........ $115,789 $117,149 $7,380,387 

Remove and replace CMSX–6 CT blade set 16 work-hours × $85 per hour = $1,360 ........ $90,271 $91,631 $5,772,753 

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 

■ 1. The authority citation for part 39 

continues to read as follows: 

Authority: 49 U.S.C. 106(g), 40113, 44701. 

§ 39.13 [Amended] 

■ 2. The FAA amends § 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 inflight 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: ANE-AD-AMOC@faa.gov. 

(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. 


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(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: 

barbara.caufield@faa.gov. 

(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 

DEPARTMENT OF TRANSPORTATION 

Federal Aviation Administration 

14 CFR Part 39 

[Docket No. FAA–2021–0032; Project 

Identifier AD–2020–01314–P; Amendment 

39–22013; AD 2022–08–10] 

RIN 2120–AA64 

Airworthiness Directives; Hamilton 

Sundstrand Corporation Propellers 

AGENCY: Federal Aviation 

Administration (FAA), DOT. 

ACTION: Final rule. 

SUMMARY: The FAA is superseding 

Airworthiness Directive (AD) 2020–12– 

07 for certain Hamilton Sundstrand 

Corporation (Hamilton Sundstrand) 54H 

model propellers. AD 2020–12–07 

required initial and repetitive eddy 

current inspections (ECI) of certain 

propeller blades and replacement of the 

propeller blades that fail the inspection. 

This AD was prompted by a report of 

the separation of a 54H60 model 

propeller blade installed on a United 

States Marine Corps Reserve (USMCR) 

KC–130T airplane during a flight in July 

2017. This AD requires initial and 

repetitive ECI of all propeller blades 

installed on Hamilton Sundstrand 

54H60 propeller hubs and replacement 

of any propeller blade that fails 

inspection. The FAA is issuing this AD 

to address the unsafe condition on these 

products. 

DATES: This AD is effective May 27, 

2022. 

The Director of the Federal Register 

approved the incorporation by reference 

of certain publications listed in this AD 

as of May 27, 2022. 

ADDRESSES: For service information 

identified in this final rule, contact 

Hamilton Sundstrand, 1 Hamilton Road, 

Windsor Locks, CT 06096–1010; phone: 

(877) 808–7575; email: CRC@

collins.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 (817) 222–5110. It is also

available at https://www.regulations.gov

by searching for and locating Docket No.

FAA–2021–0032.

Examining the AD Docket 

You may examine the AD docket at 

https://www.regulations.govby 

searching for and locating Docket No. 

FAA–2021–0032; 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: 

Michael Schwetz, Aviation Safety 

Engineer, Boston ACO Branch, FAA, 

1200 District Avenue, Burlington, MA 

01803; phone: (781) 238–7761; fax: (781) 

238–7199; email: 9-AVS-AIR-BACOCOS@faa.gov. 

SUPPLEMENTARY INFORMATION: 

Background 

The FAA issued a notice of proposed 

rulemaking (NPRM) to amend 14 CFR 

part 39 to supersede AD 2020–12–07, 

Amendment 39–21142 (85 FR 36145, 

June 15, 2020), (‘‘AD 2020–12–07’’). AD 

2020–12–07 applied to certain Hamilton 

Sundstrand 54H model propellers. Note 

that AD 2020–12–07 and the Hamilton 

Sundstrand service information 

reference 54H60 model propellers 

whereas this AD references 54H model 

propellers. Hamilton Sundstrand 54H60 

model propellers are 54H model 

propellers with a 54H60 model 

propeller hub. 

The NPRM published in the Federal 

Register on February 25, 2021 (86 FR 

11473). The NPRM was prompted by a 

report of the separation of a 54H60 

model propeller blade installed on a 

USMCR KC–130T airplane during a 

flight in July 2017. The USMCR 

investigation of this event revealed the 

Hamilton Sundstrand 54H60 model 

propeller blade separated due to 

corrosion pitting and a resultant 

intergranular radial crack that was not 

corrected at the last propeller overhaul. 

From this intergranular crack, a fatigue 

crack initiated and grew under service 

loading until the Hamilton Sundstrand 

54H60 model propeller blade could no 

longer sustain the applied loads and 

ultimately the blade separated. The 

separation of the blade resulted in the 

loss of the airplane and 17 fatalities. The 

investigation further revealed that 

54H60 model propeller blades 

manufactured before 1971 are 

susceptible to cracks of the propeller 

blade in the area of the internal taper 

bore. The applicability of AD 2020–12– 

07 was therefore limited to those 

Hamilton Sundstrand 54H60 model 

propellers blades with a blade serial 

number (S/N) below 813320, which are 

those propeller blades manufactured 

before 1971. 

Since the FAA issued AD 2020–12– 

07, the manufacturer determined that all 

propeller blades installed on Hamilton 

Sundstrand 54H model propellers with 

a 54H60 model propeller hub are 

susceptible to intergranular corrosion 

cracking in the blade taper bore. As a 

result, the manufacturer published 

Hamilton Sundstrand Alert Service 

Bulletin (ASB) 54H60–61–A154, 

Revision 1, dated May 29, 2020 (ASB 

54H60–61–A154), to expand the 

effectivity to include propeller blades 

with a blade S/N below 813320, all 

propeller blades if the propeller 

contains a propeller blade with a blade 

S/N below 813320, and all propeller 

blades that have not been overhauled 

within ten years. ASB 54H60–61–A154 

also provides instructions for 

concurrent compliance with Hamilton 

Sundstrand ASB 54H60–61–A155, 

dated May 29, 2020, to ECI an expanded 

and deeper taper bore area. In the 

NPRM, the FAA proposed to require 

initial and repetitive ECI of all propeller 

blades installed on Hamilton 

Sundstrand 54H60 propeller hubs and 

replacement of any propeller blade that 

fails inspection. The FAA is issuing this 

AD to address the unsafe condition on 

these products. 

Discussion of Final Airworthiness 

Directive 

The FAA received comments from 

one commenter, Lynden Air Cargo, LLC 

(LAC). The following presents the 

comments received on the NPRM and 

the FAA’s response to each comment. 

Request To Remove ‘‘All’’ From 

Proposed AD Requirements 

LAC noted that the proposed AD used 

the word ‘‘all’’ in reference to propeller 

blades in the preamble of the NPRM. 

LAC stated that this AD should not 

apply to newly manufactured (–2A) 


lotter on DSK11XQN23PROD with RULES1