[Federal Register Volume 85, Number 238 (Thursday, December 10, 2020)]
[Rules and Regulations]
[Pages 79408-79411]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2020-26915]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-0542; Project Identifier AD-2020-00582-E; 
Amendment 39-21351; AD 2020-25-09]
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 all 
Pratt & Whitney Division (PW) PW4164, PW4164-1D, PW4168, PW4168-1D, 
PW4168A, PW4168A-1D, and PW4170 model turbofan engines with a certain 
outer combustion chamber assembly and 3rd stage low-pressure turbine 
(LPT) duct segments installed. This AD was prompted by reports of 
damaged or failed 3rd stage LPT duct segments on PW engines with the 
Talon IIB outer combustion chamber assembly configuration installed. 
This AD requires removing and replacing certain 3rd stage LPT duct 
segments. The FAA is issuing this AD to address the unsafe condition on 
these products.

DATES: This AD is effective January 14, 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.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. It is 
also available at https://www.regulations.gov by searching for and 
locating Docket No. FAA-2020-0542.

Examining the AD Docket

    You may examine the AD docket at https://www.regulations.gov by 
searching for and locating Docket No. FAA-2020-0542; 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 all PW PW4164, PW4164-
1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model turbofan 
engines with a certain outer combustion chamber assembly and 3rd stage 
LPT duct segments installed. The NPRM published in the Federal Register 
on June 12, 2020 (85 FR 35812). The NPRM was prompted by multiple 
reports of damaged or failed 3rd stage LPT duct segments that resulted 
in engine surges, in-flight shutdowns, diversions, and air turnbacks. 
The reports were attributed to elevated gas path temperature at the 
outer diameter of the turbine flowpath and high-pressure turbine (HPT) 
2nd stage blade outer air seal spallation, which led to the distortion 
and liberation of 3rd stage LPT duct segments. In the NPRM, the FAA 
proposed to require removing and replacing certain 3rd stage LPT duct 
segments. The FAA is issuing this AD

[[Page 79409]]

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, International (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 Compliance or Definition

    Delta requested that the FAA revise paragraph (g) of this AD to 
require replacement of duct segments that have operated with more than 
2,500 cycles with a Talon IIB combustor. Alternatively, Delta requested 
the FAA revise paragraph (i) of this AD to define an ``engine shop 
visit'' as ``removal and disassembly of the HPT module.'' Delta noted 
several industry events have occurred related to the failure of 3rd 
stage LPT duct segments, also commonly called outer transition ducts 
(OTDs), on PW4000-100 engines with Talon IIB combustors. Prior 
information from the design approval holder indicates that industry 
failures have occurred only on parts that have operated more than 3,000 
flight cycles with a Talon IIB combustor.
    Delta further noted that paragraph (g) of the proposed rule would 
require that duct segments with certain part numbers be removed and 
replaced with new parts at every engine shop visit, defined in 
paragraph (i) as the ``induction of an engine into the shop for 
maintenance involving the separation of pairs of major mating 
flanges.'' Per this definition, engines with few cycles in service 
since prior OTD replacement would require installation of new hardware, 
even for minor repairs where maintenance of the LPT would not have 
otherwise been required.
    Additionally, Delta commented that OTD replacement requires 
significant teardown of the LPT module, which will result substantial 
fallout and repair costs for unrelated hardware. Delta reasoned that 
the proposed rule would require repetitive replacement of low-time duct 
segments at substantial financial burden to achieve minimal risk 
reduction. Since industry experience has demonstrated duct segment 
liberation to occur on hardware above 3,000 flight cycles, Delta 
concluded that sufficient data should exist to establish an allowable 
service life that maintains an acceptable level of safety.
    Delta also noted that while a cycle-based requirement would be 
preferable, defining an engine shop visit as ``removal and disassembly 
of the HPT module'' would maintain an acceptable level of safety. Delta 
commented that requiring replacement of low-time duct segments during 
minor repairs presents a substantial financial burden for minimal risk 
reduction.
    The FAA disagrees with revising paragraph (g) or (i) of this AD. 
Requiring removal of the 3rd stage LPT duct segments at the next HPT 
overhaul does not adequately address the unsafe condition. The FAA's 
risk assessment assumed that the 3rd stage LPT duct segments would be 
replaced at every shop visit, which provides an acceptable level of 
safety. Operators may propose to the FAA an alternative method of 
compliance in accordance with paragraph (j) of this AD. The FAA did not 
change this AD.

Request To Require Removed Duct Segments be Discarded, Scrapped, or 
Mutilated

    Delta requested that the FAA revise paragraph (g) of this AD to 
require that 3rd stage LPT duct segments that have been removed from 
service be discarded, scrapped, or mutilated. Delta reasoned that the 
rule would apply only to PW4000-100 engines with certain combustors, 
but the subject part numbers are certified for installation in other 
engine models. Delta expressed concern that without a requirement to 
discard or scrap the removed duct segments, they could potentially be 
installed in a PW4000-94 or non-Talon-IIB PW4000-100 engine or sold to 
an operator without knowledge of their prior operation with a Talon IIB 
combustor.
    The FAA disagrees with Delta's request. When parts are removed from 
service due to an AD, they are unserviceable unless the AD specifies 
otherwise. Unserviceable parts are not airworthy and should be disposed 
of in a manner that does not allow them to be returned to service. 
Operators must ensure only serviceable parts are installed on engines 
before approving the aircraft for return to service. The FAA did not 
change this AD.

Request To Include Available Fleet Data

    Delta requested that the FAA update the proposed rule to reflect 
the available fleet data, which shows that failure of 3rd stage LPT 
duct segments has only occurred after 3,000 cycles or greater in 
operation on engines with a Talon IIB combustor. Delta stated that the 
Discussion paragraph of the proposed rule does not provide prior 
service history of LPT duct segments that have failed in-service. Delta 
further noted that prior communications from the design approval holder 
indicate that industry failures occurred on parts that operated 3,000 
flight cycles or more under exposure to the higher-than-expected 
temperatures with a Talon IIB combustor installed.
    The FAA disagrees. The Discussion paragraph of the NPRM provides an 
adequate discussion of the failure in service of 3rd stage LPT duct 
segments. The FAA did not change this AD.

Request To Update Service Information

    Delta requested that the FAA add PW Service Bulletin (SB) PW4G-100-
72-220 to the Related Service Information paragraph of this AD. Delta 
noted that the accomplishment of SB PW4G-100-72-220 installs a Talon 
IIB combustor, and 3rd stage duct segments operated on a post-SB engine 
would be subject to the proposed rule as well.
    The FAA agrees and has added PW SB PW4G-100-72-220 to the Related 
Service Information paragraph of this AD.

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 PW SB No. PW4G-100-72-214, dated December 15, 
2011; PW SB No. PW4G-100-72-219, Revision 1, dated October 5, 2011; PW 
SB No. PW4G-100-72-253, dated November 24, 2014; and PW SB No. PW4G-
100-72-220, Revision 4, dated September 30, 2011. PW SB No. PW4G-100-
72-214 introduces the Talon IIB outer combustion chamber assembly that 
reduces the combustor exit temperature levels at the outer diameter of 
the combustor. PW SB No. PW4G-100-72-219 describes procedures for 
installing the Advantage70 engine upgrade kit to improve engine 
reliability and fuel consumption, and to reduce maintenance costs. PW 
SB No. PW4G-

[[Page 79410]]

100-72-253 describes procedures for replacing the outer combustion 
chamber assembly waspaloy nuts. PW SB PW4G-100-72-220 describes 
procedures for installing the Advantage70 engine upgrade kit to improve 
engine reliability and fuel consumption, reduce maintenance costs, and 
convert engine thrust rating.

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
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Remove and replace 3rd stage LPT duct   56 work-hours x $85 per          $85,000         $89,760      $8,886,240
 segments.                               hour = $4,760.
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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:

2020-25-09 Pratt & Whitney Division: Amendment 39-21351; Docket No. 
FAA-2020-0542; Project Identifier AD-2020-00582-E.

(a) Effective Date

    This airworthiness directive (AD) is effective January 14, 2021.

(b) Affected ADs

    None.

(c) Applicability

    This AD applies to all Pratt & Whitney Division (PW) PW4164, 
PW4164-1D, PW4168, PW4168-1D, PW4168A, PW4168A-1D, and PW4170 model 
turbofan engines that have 3rd stage low-pressure turbine (LPT) duct 
segments, part number (P/N) 50N434-01 or P/N 50N450-01 installed, 
and have the Talon IIB outer combustion chamber assembly, P/N 51J500 
or P/N 51J381, installed.

(d) Subject

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

(e) Unsafe Condition

    This AD was prompted by reports of damaged or failed 3rd stage 
LPT duct segments on PW engines with the Talon IIB outer combustion 
chamber assembly configuration installed. The FAA is issuing this AD 
to prevent failure of the 3rd stage LPT duct segments. The unsafe 
condition, if not addressed, could result in uncontained release of 
LPT blades and vanes, 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 Action

    At every engine shop visit after the effective date of this AD, 
remove from service the 3rd stage LPT duct segments, P/N 50N434-01 
and P/N 50N450-01, and replace them with parts with zero flight 
cycles.

(h) Terminating Action

    Removal of the 3rd stage LPT duct segments, P/N 50N434-01 and P/
N 50N450-01, and their replacement with parts having P/Ns other than 
P/N 50N434-01 and P/N 50N450-01, constitutes terminating action for 
the repetitive replacement required by paragraph (g) of this AD.

(i) Definition

    For the purpose of this AD, 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.

(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. 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.

(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].

[[Page 79411]]

(l) Material Incorporated by Reference

    None.

    Issued on December 2, 2020.
Lance T. Gant,
Director, Compliance & Airworthiness Division, Aircraft Certification 
Service.
[FR Doc. 2020-26915 Filed 12-9-20; 8:45 am]
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