Document ID: FAA-2021-0577-0001
Agency: faa
Document Type: Proposed Rule
Title: Airworthiness Directives: Pratt and Whitney Division Turbofan Engines
Posted Date: 2021-07-23T04:00Z

[Federal Register Volume 86, Number 139 (Friday, July 23, 2021)]
[Proposed Rules]
[Pages 38941-38943]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-15518]

 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 86, No. 139 / Friday, July 23, 2021 / 
Proposed Rules  

[[Page 38941]]

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0577; Project Identifier AD-2021-00470-E]
RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney Division Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 
2021-05-16, which applies to certain Pratt & Whitney Division (PW) 
PW4164, PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 
model turbofan engines. AD 2021-05-16 requires 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 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. Since 
the FAA issued AD 2021-05-16, the FAA was notified of an inadvertent 
omission in the LPT 4th-stage air sealing ring segment assembly part 
numbers. This proposed AD would correct this omission. The FAA is 
proposing this AD to address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by September 
7, 2021.

ADDRESSES: You may send comments, using the procedures found in 14 CFR 
11.43 and 11.45, by any of the following methods:
     Federal eRulemaking Portal: Go to https://www.regulations.gov. Follow the instructions for submitting comments.
     Fax: (202) 493-2251.
     Mail: U.S. Department of Transportation, Docket 
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New 
Jersey Avenue SE, Washington, DC 20590.
     Hand Delivery: Deliver to Mail address above between 9 
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
    For service information identified in this NPRM, contact Pratt & 
Whitney, 400 Main Street, East Hartford, CT 06118; phone: (800) 565-
0140; email: help24@prattwhitney.com; website: https://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.

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 NPRM, any comments 
received, and other information. The street address for Docket 
Operations is listed above.

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: 
carol.nguyen@faa.gov.

SUPPLEMENTARY INFORMATION:

Comments Invited

    The FAA invites you to send any written relevant data, views, or 
arguments about this proposal. Send your comments to an address listed 
under ADDRESSES. Include ``Docket No. FAA-2021-0577; Project Identifier 
AD-2021-00470-E'' at the beginning of your comments. The most helpful 
comments reference a specific portion of the proposal, explain the 
reason for any recommended change, and include supporting data. The FAA 
will consider all comments received by the closing date and may amend 
the proposal because of those comments.
    Except for Confidential Business Information (CBI) as described in 
the following paragraph, and other information as described in 14 CFR 
11.35, the FAA will post all comments received, without change, to 
https://www.regulations.gov, including any personal information you 
provide. The agency will also post a report summarizing each 
substantive verbal contact the FAA receives about this proposed AD.

Confidential Business Information

    CBI is commercial or financial information that is both customarily 
and actually treated as private by its owner. Under the Freedom of 
Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public 
disclosure. If your comments responsive to this NPRM contain commercial 
or financial information that is customarily treated as private, that 
you actually treat as private, and that is relevant or responsive to 
this NPRM, it is important that you clearly designate the submitted 
comments as CBI. Please mark each page of your submission containing 
CBI as ``PROPIN.'' The FAA will treat such marked submissions as 
confidential under the FOIA, and they will not be placed in the public 
docket of this NPRM. Submissions containing CBI should be sent to Carol 
Nguyen, Aviation Safety Engineer, ECO Branch, FAA, 1200 District 
Avenue, Burlington, MA 01803. Any commentary that the FAA receives 
which is not specifically designated as CBI will be placed in the 
public docket for this rulemaking.

Background

    The FAA issued AD 2021-05-16, Amendment 39-21459 (86 FR 17287, 
April 2, 2021), (AD 2021-05-16), for 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. AD 2021-05-16 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

[[Page 38942]]

segment assemblies. AD 2021-05-16 requires initial and repetitive 
replacements of the LPT 4th-stage air sealing ring segment assemblies 
with parts eligible for installation. AD 2021-05-16 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 agency issued AD 2021-05-16 
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.

Actions Since AD 2021-05-16 Was Issued

    Since the FAA issued AD 2021-05-16, the FAA was notified by a 
manufacturer of parts manufacturer approval (PMA) parts and that 
paragraphs (c), (g), and (h) of the AD should include affected PMA part 
numbers because the unsafe condition also applies to those parts. The 
FAA added FAA-approved equivalent part numbers to paragraphs (c), (g), 
and (h) of this AD to include PMA part numbers.

FAA's Determination

    The FAA is issuing this NPRM after determining that the unsafe 
condition described previously is likely to exist or develop on other 
products of the same type design.

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.

Proposed AD Requirements in This NPRM

    This proposed AD would retain all the requirements of AD 2021-05-
16. This proposed AD would add ``or FAA-approved equivalent part 
numbers'' to paragraph (c), Applicability; paragraph (g), Required 
Actions; and paragraph (h), Definitions, of this AD. This proposed AD 
would also add paragraph (i), Credit for Previous Actions, allowing 
operators to take credit for the required actions in paragraph (g)(4) 
of this AD if, prior to the effective date of this AD, operators 
performed dimensional inspections of the LPT case for bulging using 
Pratt & Whitney ASB No. PW4G-100-A72-262, Original Issue, dated October 
22, 2019.

Costs of Compliance

    The FAA estimates that this AD, if adopted as proposed, would 
affect 99 engines installed on airplanes of U.S. registry.
    The FAA estimates the following costs to comply with this proposed 
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 proposed 
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 determined that this proposed AD would not have federalism 
implications under Executive Order 13132. This proposed AD would not 
have a substantial direct effect on the States, on the relationship 
between the national Government and the States, or on the distribution 
of power and responsibilities among the various levels of government.
    For the reasons discussed above, I certify that the proposed 
regulation:
    (1) Is not a ``significant regulatory action'' under Executive 
Order 12866,
    (2) Would not affect intrastate aviation in Alaska, and
    (3) Would not have a significant economic impact, positive or 
negative, on a substantial number of small entities under the criteria 
of the Regulatory Flexibility Act.

[[Page 38943]]

List of Subjects in 14 CFR Part 39

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

The Proposed Amendment

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

PART 39--AIRWORTHINESS DIRECTIVES

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 AD 2021-05-16, Amendment 39-21459 
(86 FR 17287, April 2, 2021); and
0
b. Adding the following new airworthiness directive:

Pratt & Whitney Division: Docket No. FAA-2021-0577; Project 
Identifier AD-2021-00470-E.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) action by September 7, 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 paragraphs (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 No. 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 Related Information. Information may be emailed 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.

(k) Related Information

    (1) 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: carol.nguyen@faa.gov.
    (2) For service information identified in this AD, contact Pratt 
& Whitney, 400 Main Street, East Hartford, CT 06118; phone: (800) 
565-0140; email: help24@prattwhitney.com; website: https://prattwhitney.com. You may view this referenced 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 (781) 238-
7759.

    Issued on July 16, 2021.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2021-15518 Filed 7-22-21; 8:45 am]
BILLING CODE 4910-13-P