[Federal Register Volume 85, Number 191 (Thursday, October 1, 2020)]
[Proposed Rules]
[Pages 61886-61889]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-21607]


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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]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney Division Turbofan 
Engines

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD) 
for certain Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, 
PW4168-1D, PW4168A, PW4168A-1D,

[[Page 61887]]

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. An investigation by the 
manufacturer 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. This proposed AD would 
require initial and repetitive replacements of the LPT 4th stage air 
sealing ring segment assemblies with parts eligible for installation. 
This proposed AD would also 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 proposing this AD to address the unsafe condition on these 
products.

DATES: The FAA must receive comments on this proposed AD by November 
16, 2020.

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 Division, 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 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.

Examining the AD Docket

    You may examine the AD docket on the internet 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 NPRM, any comments received, and other information. The street 
address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Carol Nguyen, Aerospace Engineer, ECO 
Branch, FAA, 1200 District Avenue, Burlington, MA 01803; phone: (781) 
238-7655; fax: (781) 238-7199; email: [email protected].

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 the ADDRESSES section. Include ``Docket No. FAA-2020-0901; 
Project Identifier AD-2020-00705-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 this proposal because of those comments.
    Except for Confidential Business Information 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 FAA will also post a report summarizing each substantive 
verbal contact received about this proposal.

Confidential Business Information

    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, Aerospace 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 received 6 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. As a result of this 
damage, gas-path air escapes and impinges on the LPT case. This can 
distort (create local bulging) the LPT case rail, causing the LPT 4th 
stage vanes to lean back and contact the LPT 4th stage blades. This 
condition, if not addressed, could result in uncontained release of LPT 
4th stage blades, damage to the engine, and damage to the airplane.

FAA's Determination

    The FAA is proposing this AD because the agency evaluated all the 
relevant information and determined the unsafe condition described 
previously is likely to exist or develop in other products of the same 
type design.

Service Information Incorporated by Reference Under 1 CFR Part 51

    The FAA reviewed PW Alert Service Bulletin (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 the ADDRESSES section.

Proposed AD Requirements

    This proposed AD would require initial and repetitive replacement 
of the LPT 4th stage air sealing ring segment assemblies with parts 
eligible for installation. This proposed AD would also 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.

Costs of Compliance

    The FAA estimates that this AD, 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:

[[Page 61888]]



                                                 Estimated Costs
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                                                                                     Cost per      Cost on U.S.
                Action                         Labor cost           Parts cost        product        operators
----------------------------------------------------------------------------------------------------------------
LPT case dimensional inspection.......  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.
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    The FAA estimates the following costs to perform necessary repair 
or replacement that would be required based on the results of the 
proposed dimensional inspection. The FAA has no way of determining how 
many engines will need to repair or replace the LPT case.

                                               On-Condition Costs
----------------------------------------------------------------------------------------------------------------
                                                                                                     Cost per
                    Action                                 Labor cost               Parts cost        product
----------------------------------------------------------------------------------------------------------------
LPT case repair 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

    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 this proposed 
regulation:
    (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 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 adding the following new airworthiness 
directive (AD):

Pratt & Whitney Division: Docket No. FAA-2020-0901; Project 
Identifier AD-2020-00705-E.

(a) Comments Due Date

    The FAA must receive comments on this airworthiness directive 
(AD) by November 16, 2020.

(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 
50N526-1, 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 (g)(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

[[Page 61889]]

required by paragraphs (g)(1), (g)(2), and (g)(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 is 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 (lettered flanges). 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.

(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 paragraph (j)(1) of this AD. 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

    (1) For more information about this AD, contact Carol Nguyen, 
Aerospace Engineer, ECO Branch, FAA, 1200 District Avenue, 
Burlington, MA, 01803; phone: (781) 238-7655; fax: (781) 238-7199; 
email: [email protected].
    (2) For service information identified in this AD, contact Pratt 
& Whitney Division, 400 Main Street, East Hartford, CT 06118; phone: 
(800) 565-0140; email: [email protected]; website: http://fleetcare.pw.utc.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 September 25, 2020.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2020-21607 Filed 9-30-20; 8:45 am]
BILLING CODE 4910-13-P