[Federal Register Volume 86, Number 62 (Friday, April 2, 2021)]
[Rules and Regulations]
[Pages 17287-17290]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-06804]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0901; Project Identifier AD-2020-00705-E; 
Amendment 39-21459; AD 2021-05-16]
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 adopting a new airworthiness directive (AD) for 
certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, 
PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan engines. This 
AD was prompted by several reports of low-pressure turbine (LPT) 4th-
stage vane cluster assemblies leaning back and notching into the 
rotating LPT 4th-stage blades, causing some blades to fracture and 
release. 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 May 7, 2021.
    The Director of the Federal Register approved the incorporation by 
reference of a certain publication listed in this AD as of May 7, 2021.

ADDRESSES: For service information identified in this final rule, 
contact Pratt & Whitney, 400 Main Street, East Hartford, CT 06118; 
phone: (800) 565-0140; email: [email protected]; website: http://fleetcare.pw.utc.com. You may view this service information at the FAA, 
Airworthiness Products

[[Page 17288]]

Section, Operational Safety Branch, 1200 District Avenue, Burlington, 
MA 01803. For information on the availability of this material at the 
FAA, call (781) 238-7759. It is also available at https://www.regulations.gov by searching for and locating Docket No. FAA-2020-
0901.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0901; 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 by adding an AD that would apply to certain PW PW4164, 
PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model 
turbofan engines. The NPRM published in the Federal Register on October 
1, 2020 (85 FR 61886). The NPRM was prompted by 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. The FAA also proposed in the NPRM 
to require initial and repetitive dimensional inspections of the LPT 
case for bulging and, depending on the results of the dimensional 
inspection, repair or replacement of the LPT case. The FAA is issuing 
this AD to address the unsafe condition on these products.

Discussion of Final Airworthiness Directive Comments

    The FAA received comments from two commenters. The commenters were 
Air Line Pilots Association (ALPA) and Delta Air Lines, Inc. (Delta). 
ALPA supported the proposal without change. Delta supported the 
proposal but recommended certain changes. The following presents the 
comments received on the NPRM and the FAA's response to each comment.

Request to the Revise Required Actions

    Delta requested that the FAA revise paragraph (g)(5) of this AD to 
specify that any currently approved manual repairs are acceptable to 
return an LPT case to service. Delta stated that if Pratt & Whitney 
were to add additional repairs for Index 20 or Index 27 to the CIR 
Manual, it is unclear whether operators would be permitted to repair 
the LPT case per the latest manual revision or would be restricted to 
those manual revisions currently listed in Table 1 of Pratt & Whitney 
Alert Service Bulletin (ASB) PW4G-100-A72-262 Revision No. 1, dated 
September 3, 2020.
    The FAA disagrees with revising paragraph (g)(5) of this AD since 
this paragraph does not require use of a specific repair. Operators may 
use any approved repair to return the LPT case to a serviceable 
condition. The FAA did not change this AD.

Request to the Revise a Definition

    Delta requested that the FAA revise paragraph (h)(1) of this AD to 
restrict the definition of ``engine shop visit'' to only those visits 
in which flanges H through P are separated. Delta reasoned that while 
the ASB clarifies that flanges H through P, as identified in the PW4168 
Engine Manual, Chapter/Section 72-00-00 Engine General, Description/
Operation-01, Figure 6, constitute ``major mating engine flanges,'' the 
proposed rule would require teardown of the LPT module in instances 
when one of the flanges forward of flange H was separated to perform 
minor repairs on the cold section of the engine.
    The FAA agrees and has revised paragraph (h)(1) of this AD to 
define ``an engine shop visit'' as the induction of an engine into the 
shop for maintenance involving the separation of pairs of major mating 
engine flanges H through P.

Conclusion

    The FAA reviewed the relevant data, considered any comments 
received, and determined that air safety requires adopting this AD as 
proposed. Accordingly, the FAA is issuing this AD to address the unsafe 
condition on these products. Except for minor editorial changes, and 
any other changes described previously, this AD is adopted as proposed 
in the NPRM. None of the changes will increase the economic burden on 
any operator.

Related Service Information Under 1 CFR Part 51

    The FAA reviewed Pratt & Whitney ASB No. PW4G-100-A72-262, Revision 
No. 1, dated September 3, 2020. The ASB describes procedures for 
replacing the LPT 4th-stage air sealing ring segment assemblies and 
inspecting the LPT case for bulging. 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                $0            $170         $16,830
                                         hour = $170.
Replace the LPT 4th-stage air sealing   50 work-hours x $85 per           64,592          68,842       6,815,358
 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

[[Page 17289]]

the number of engines 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
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Authority for This Rulemaking

    Title 49 of the United States Code specifies the FAA's authority to 
issue rules on aviation safety. Subtitle I, section 106, describes the 
authority of the FAA Administrator. Subtitle VII: Aviation Programs, 
describes in more detail the scope of the Agency's authority.
    The FAA is issuing this rulemaking under the authority described in 
Subtitle VII, Part A, Subpart III, Section 44701: General requirements. 
Under that section, Congress charges the FAA with promoting safe flight 
of civil aircraft in air commerce by prescribing regulations for 
practices, methods, and procedures the Administrator finds necessary 
for safety in air commerce. This regulation is within the scope of that 
authority because it addresses an unsafe condition that is likely to 
exist or develop on products identified in this rulemaking action.

Regulatory Findings

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

List of Subjects in 14 CFR Part 39

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

The Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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:

2021-05-16 Pratt & Whitney Division: Amendment 39-21459; Docket No. 
FAA-2020-0901; Project Identifier AD-2020-00705-E.

(a) Effective Date

    This airworthiness directive (AD) is effective May 7, 2021.

(b) Affected ADs

    None.

(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 or P/N 
50N526-01, 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, part number (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 or P/N 50N526-01, 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 or P/N 50N526-01, and replace with parts 
eligible for installation.
    (3) For all affected engines, at each LPT overhaul after 
compliance with the required actions in paragraphs (g)(1) or (2) of 
this AD, remove from service the LPT 4th-stage air sealing ring 
segment assemblies, P/N 50N526-01, 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), (2), and (3) 
of this AD, perform a dimensional inspection of the LPT case for 
bulging in accordance with the Accomplishment Instructions, 
paragraph 2, of PW ASB 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, with zero flight 
cycles since new or with a P/N not mentioned in this AD.

[[Page 17290]]

(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 
certification office, send it to the attention of the person 
identified in Related Information. You may email your request 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.

(j) 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].

(k) 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.
    (i) Pratt & Whitney Alert Service Bulletin No. PW4G-100-A72-262, 
Revision No. 1, dated September 3, 2020.
    (ii) [Reserved].
    (3) 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: http://fleetcare.pw.utc.com.
    (4) 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.
    (5) 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 March 10, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-06804 Filed 4-1-21; 8:45 am]
BILLING CODE 4910-13-P