[Federal Register Volume 86, Number 216 (Friday, November 12, 2021)]
[Rules and Regulations]
[Pages 62717-62719]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-24574]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0577; Project Identifier AD-2021-00470-E; 
Amendment 39-21787; AD 2021-22-14]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney Division Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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SUMMARY: The FAA is superseding Airworthiness Directive (AD) 2021-05-16 
for certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, 
PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines. AD 
2021-05-16 required initial and repetitive replacements of the low-
pressure turbine (LPT) 4th-stage air sealing ring segment assemblies 
with parts eligible for installation. AD 2021-05-16 also required 
initial and repetitive dimensional inspections of the LPT case for 
bulging and, depending on the results of the dimensional inspections, 
repair or replacement of the LPT case. This AD was prompted by 
notification to the FAA of an inadvertent omission in the LPT 4th-stage 
air sealing ring segment assembly part numbers. This AD requires 
initial and repetitive replacements of the LPT 4th-stage air sealing 
ring segment assemblies with parts eligible for installation. This AD 
also requires initial and repetitive dimensional inspections of the LPT 
case for bulging and, depending on the results of the dimensional 
inspections, repair or replacement of the LPT case. The FAA is issuing 
this AD to address the unsafe condition on these products.

DATES: This AD is effective December 17, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain other publication listed in this AD as of May 7, 
2021 (86 FR 17287, April 2, 2021).

ADDRESSES: For service information identified in this final rule, 
contact Pratt & Whitney Division, 400 Main Street, East Hartford, CT 
06118; phone: (800) 565-0140; email: [email protected]; website: 
https://fleetcare.prattwhitney.com. You may view this service 
information at the Airworthiness Products Section, Operational Safety 
Branch, FAA, 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-2021-0577.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2021-0577; 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: Carol Nguyen, Aviation Safety 
Engineer, ECO Branch, FAA, 1200 District Avenue, Burlington, MA 01803; 
phone: (781) 238-7655; fax: (781) 238-7199; email: 
[email protected].

SUPPLEMENTARY INFORMATION:

Background

    The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 
CFR part 39 to supersede AD 2021-05-16, Amendment 39-21459 (86 FR 
17287, April 2, 2021), (AD 2021-05-16). AD 2021-05-16 applied to 
certain PW PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, 
and PW4170 model turbofan engines with LPT 4th-stage air sealing ring 
segment assemblies, part number (P/N) 50N463-01 or P/N 50N526-01, 
installed. The NPRM published in the Federal Register on July 23, 2021 
(86 FR 38941). The NPRM was prompted by notification from a 
manufacturer of parts manufacturer approval (PMA) parts that AD 2021-
05-16 should include affected PMA part numbers because the unsafe 
condition also applies to those parts. AD 2021-05-16 resulted from six 
reports from the manufacturer concerning LPT 4th-stage vane cluster 
assemblies leaning back and notching into rotating LPT 4th-stage 
blades, causing some blades to fracture and release. These incidents 
resulted in an aborted takeoff, air turnbacks, engine surges, high 
vibrations, and unplanned engine removals. The incidents were 
attributed to the LPT 4th-stage air sealing ring segment assemblies 
moving into the LPT 4th-stage blades knife edge seals, resulting in 
damage to the ring segment assemblies. In the NPRM, the FAA proposed to 
require initial and repetitive replacements of the LPT 4th-stage air 
sealing ring segment assemblies with parts eligible for installation. 
In the

[[Page 62718]]

NPRM, the FAA also proposed to require initial and repetitive 
dimensional inspections of the LPT case for bulging and, depending on 
the results of the dimensional inspections, repair or replacement of 
the LPT case.

Discussion of Final Airworthiness Directive

Comments

    The FAA received comments from one commenter, the Air Line Pilots 
Association (ALPA). ALPA supported the NPRM without change.

Conclusion

    The FAA reviewed the relevant data, considered the comments 
received, and determined that air safety requires adopting the AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. This AD is adopted as proposed in the 
NPRM.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Pratt & Whitney Alert Service Bulletin No. PW4G-
100-A72-262, Revision No. 1, dated September 3, 2020 (the ASB). The ASB 
specifies procedures for replacing the LPT 4th-stage air sealing ring 
segment assemblies and inspecting the LPT case for bulging. The 
Director of the Federal Register approved the ASB for incorporation by 
reference as of May 7, 2021 (86 FR 17287, April 2, 2021). 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 99 engines installed on 
airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this AD:

                                                 Estimated Costs
----------------------------------------------------------------------------------------------------------------
                                                                                     Cost per      Cost on U.S.
               Action                         Labor cost            Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
Inspect the LPT case for bulging...  2 work-hours x $85 per hour              $0            $170         $16,830
                                      = $170.
Replace the LPT 4th-stage air        50 work-hours x $85 per              64,592          68,842       6,815,358
 sealing ring segment assemblies.     hour = $4,250.
----------------------------------------------------------------------------------------------------------------

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

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
Repair LPT case to restore dimensions.........  250 work-hours x $85 per hour =               $0         $21,250
                                                 $21,250.
Replace the LPT case..........................  0 work-hours x $85 per hour = $0       1,300,000       1,300,000
----------------------------------------------------------------------------------------------------------------

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 has determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will not have a 
substantial direct effect on the States, on the relationship between 
the national government and the States, or on the distribution of power 
and responsibilities among the various levels of government.
    For the reasons discussed above, I certify that this AD:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Will not affect intrastate aviation in Alaska, and
    (3) Will not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

The Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the FAA amends 14 CFR part 39 as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
1. The authority citation for part 39 continues to read as follows:

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


Sec.  39.13  [Amended]

0
2. The FAA amends Sec.  39.13 by:
0
a. Removing Airworthiness Directive 2021-05-16, Amendment 39-21459 (86 
FR 17287, April 2, 2021); and
0
b. Adding the following new airworthiness directive:

2021-22-14 Pratt & Whitney Division: Amendment 39-21787; Docket No. 
FAA-2021-0577; Project Identifier AD-2021-00470-E.

[[Page 62719]]

(a) Effective Date

    This airworthiness directive (AD) is effective December 17, 
2021.

(b) Affected ADs

    This AD replaces AD 2021-05-16, Amendment 39-21459 (86 FR 17287, 
April 2, 2021).

(c) Applicability

    This AD applies to Pratt & Whitney Division (PW) PW4164, PW4164-
1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model 
turbofan engines with low-pressure turbine (LPT) 4th-stage air 
sealing ring segment assemblies, part number (P/N) 50N463-01, P/N 
50N526-01, or FAA-approved equivalent part numbers, installed.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by several reports from the manufacturer 
concerning LPT 4th-stage vane cluster assemblies leaning back and 
notching into the rotating LPT 4th-stage blades, causing some blades 
to fracture and release. A manufacturer investigation into those 
reports determined that the leaning back of the LPT 4th-stage vane 
cluster assemblies was caused by damage to the LPT 4th-stage air 
sealing ring segment assemblies. The FAA is issuing this AD to 
prevent damage to the LPT 4th-stage air sealing ring segment 
assemblies, the LPT case, and the LPT 4th-stage blades. The unsafe 
condition, if not addressed, could result in uncontained release of 
the LPT 4th-stage blades, damage to the engine, and damage to the 
airplane.

(f) Compliance

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

(g) Required Actions

    (1) For affected engines that have either the Talon IIA outer 
combustion chamber assembly, P/N 51J100 or P/N 51J382, or the Talon 
IIB outer combustion chamber assembly, P/N 51J381 or P/N 51J500, 
installed, at the next engine shop visit after the effective date of 
this AD, remove from service the LPT 4th-stage air sealing ring 
segment assemblies, P/N 50N463-01, P/N 50N526-01, or FAA-approved 
equivalent part numbers, and replace with parts eligible for 
installation.
    (2) For affected engines not referenced in paragraph (g)(1) of 
this AD, at the next LPT overhaul after the effective date of this 
AD, remove from service the LPT 4th-stage air sealing ring segment 
assemblies, P/N 50N463-01, P/N 50N526-01, or FAA-approved equivalent 
part numbers, and replace with parts eligible for installation.
    (3) For all affected engines, at each LPT overhaul after 
compliance with the required actions in paragraph (g)(1) or (2) of 
this AD, remove from service the LPT 4th-stage air sealing ring 
segment assemblies, P/N 50N526-01 or FAA-approved equivalent part 
numbers, and replace with parts eligible for installation.
    (4) During each replacement of the LPT 4th-stage air sealing 
ring segment assemblies required by paragraphs (g)(1) through (3) of 
this AD, perform a dimensional inspection of the LPT case for 
bulging in accordance with the Accomplishment Instructions, 
paragraph 2, of PW Alert Service Bulletin No. PW4G-100-A72-262 
Revision No. 1, dated September 3, 2020 (the ASB).
    (5) If, during the dimensional inspection of the LPT case 
required by paragraph (g)(4) of this AD, any LPT case found to be 
outside the serviceable limits specified in Table 1: Serviceable 
Limits and Repairs of the ASB, repair or replace the LPT case before 
further flight.

(h) Definitions

    For the purpose of this AD:
    (1) An ``engine shop visit'' is the induction of an engine into 
the shop for maintenance involving the separation of pairs of major 
mating engine flanges H through P. The separation of engine flanges 
solely for the purpose of transportation without subsequent engine 
maintenance does not constitute an engine shop visit.
    (2) An ``LPT overhaul'' is when the LPT rotor is removed from 
the engine, all four disks are removed from the LPT rotor, and all 
blades are removed from the disks.
    (3) ``Parts eligible for installation'' are LPT 4th-stage air 
sealing ring segment assemblies, P/N 50N526-01, or FAA-approved 
equivalent part numbers, with zero flight cycles since new or with a 
P/N not mentioned in this AD.

(i) Credit for Previous Actions

    You may take credit for the dimensional inspection of the LPT 
case for bulging required by paragraph (g)(4) of this AD if the 
inspection was performed before the effective date of this AD using 
PW ASB PW4G-100-A72-262 Original Issue, dated October 22, 2019.

(j) Alternative Methods of Compliance (AMOCs)

    (1) The Manager, ECO Branch, FAA, has the authority to approve 
AMOCs for this AD, if requested using the procedures found in 14 CFR 
39.19. In accordance with 14 CFR 39.19, send your request to your 
principal inspector or local Flight Standards District Office, as 
appropriate. If sending information directly to the manager of the 
certification office, send it to the attention of the person 
identified in paragraph (k) of this AD. Information may be emailed 
to: [email protected].
    (2) Before using any approved AMOC, notify your appropriate 
principal inspector, or lacking a principal inspector, the manager 
of the local flight standards district office/certificate holding 
district office.

(k) Related Information

    For more information about this AD, contact Carol Nguyen, 
Aviation Safety Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA 01803; phone: (781) 238-7655; fax: (781) 238-7199; 
email: [email protected].

(l) Material Incorporated by Reference

    (1) The Director of the Federal Register approved the 
incorporation by reference (IBR) of the service information listed 
in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
    (2) You must use this service information as applicable to do 
the actions required by this AD, unless the AD specifies otherwise.
    (3) The following service information was approved for IBR on 
May 7, 2021 (86 FR 17287, April 2, 2021).
    (i) Pratt & Whitney Alert Service Bulletin No. PW4G-100-A72-262, 
Revision No. 1, dated September 3, 2020.
    (ii) [Reserved]
    (4) For Pratt & Whitney service information identified in this 
AD, contact Pratt & Whitney, 400 Main Street, East Hartford, CT 
06118; phone: (800) 565-0140; email: [email protected]; website: 
https://fleetcare.prattwhitney.com.
    (5) You may view this service information at FAA, Airworthiness 
Products Section, Operational Safety Branch, 1200 District Avenue, 
Burlington, MA 01803. For information on the availability of this 
material at the FAA, call (781) 238-7759.
    (6) You may view this service information that is incorporated 
by reference at the National Archives and Records Administration 
(NARA). For information on the availability of this material at 
NARA, email: [email protected], or go to: https://www.archives.gov/federal-register/cfr/ibr-locations.html.

    Issued on October 15, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-24574 Filed 11-10-21; 8:45 am]
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