Rule2021-15947
Airworthiness Directives; Pratt & Whitney Turbofan Engines
Primary source
Metadata and text below are from the Federal Register, a public-domain U.S. government work. Always verify the official published version before relying on it for any legal matter.
Published
July 28, 2021
Effective
September 1, 2021
Issuing agencies
Transportation DepartmentFederal Aviation Administration
Abstract
The FAA is adopting a new airworthiness directive (AD) for all Pratt & Whitney (PW) PW2037, PW2037M, PW2040, and F117-PW-100 model turbofan engines. This AD was prompted by a report of an uncontained engine failure resulting from cracks in the knife edge of the high- pressure turbine (HPT) 2nd-stage air seal assembly. This AD requires fluorescent penetrant inspections (FPIs) and visual inspections of the HPT 2nd-stage air seal assembly and, depending on the results of the inspections, replacement of the HPT 2nd-stage air seal assembly with a part eligible for installation. This AD also requires replacement of the affected HPT 2nd-stage air seal assembly, depending on the engine model, at either the next engine shop visit or the next piece-part opportunity. The FAA is issuing this AD to address the unsafe condition on these products.
Full Text
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<title>Federal Register, Volume 86 Issue 142 (Wednesday, July 28, 2021)</title>
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[Federal Register Volume 86, Number 142 (Wednesday, July 28, 2021)]
[Rules and Regulations]
[Pages 40299-40306]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2021-15947]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. FAA-2020-0442; Project Identifier AD-2020-00260-E;
Amendment 39-21640; AD 2021-14-13]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney 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 (PW) PW2037, PW2037M, PW2040, and F117-PW-100 model
turbofan engines. This AD was prompted by a report of an uncontained
engine failure resulting from cracks in the knife edge of the high-
pressure turbine (HPT) 2nd-stage air seal assembly. This AD requires
fluorescent penetrant inspections (FPIs) and visual inspections of the
HPT 2nd-stage air seal assembly and, depending on the results of the
inspections, replacement of the HPT 2nd-stage air seal assembly with a
part eligible for installation. This AD also requires replacement of
the affected HPT 2nd-stage air seal assembly, depending on the engine
model, at either the next engine shop visit or the next piece-part
opportunity. The FAA is issuing this AD to address the unsafe condition
on these products.
DATES: This AD is effective September 1, 2021.
ADDRESSES: For service information identified in this final rule,
contact Pratt & Whitney, 400 Main Street, East Hartford, CT 06118;
phone: (800) 565-0140; fax: (860) 565-5442; email: <a href="/cdn-cgi/l/email-protection#6e060b021e5c5a2e1e19401b1a0d400d0103"><span class="__cf_email__" data-cfemail="4a222f263a787e0a3a3d643f3e2964292527">[email protected]</span></a>;
website: <a href="https://fleetcare.pw.utc.com">https://fleetcare.pw.utc.com</a>. 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 <a href="https://www.regulations.gov">https://www.regulations.gov</a> by
searching for and locating Docket No. FAA-2020-0442.
Examining the AD Docket
You may examine the AD docket at <a href="https://www.regulations.gov">https://www.regulations.gov</a> by
searching for and locating Docket No. FAA-2020-0442; 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:
<a href="/cdn-cgi/l/email-protection#8feceefde0e3a1e1e8faf6eae1cfe9eeeea1e8e0f9"><span class="__cf_email__" data-cfemail="d2b1b3a0bdbefcbcb5a7abb7bc92b4b3b3fcb5bda4">[email protected]</span></a>.
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 PW2037, PW2037M,
PW2040, and F117-PW-100 model turbofan engines. The NPRM published in
the Federal Register on June 1, 2020 (85 FR 33043). The NPRM was
prompted by a report of an uncontained engine failure resulting from
cracks in the knife edge of the HPT 2nd-stage air seal assembly. After
further analysis, it was determined that the knife-edge crack was due
to seal rubbing that elevated the HPT 2nd-stage air seal assembly
temperature and induced fatigue. In the NPRM, the FAA proposed to
require initial and repetitive borescope inspections (BSIs), FPIs, and
visual inspections of the HPT 2nd-stage air seal assembly and,
depending on the results of the inspections, replacement of the HPT
2nd-stage air seal assembly with a part eligible for installation. The
NPRM also proposed to require replacement of the affected HPT 2nd-stage
air seal assembly, depending on the engine model, at either the next
engine shop visit or the next piece-part opportunity. The FAA is
issuing this AD to address the unsafe condition on these products.
[[Page 40300]]
Discussion of Final Airworthiness Directive
Comments
The FAA received comments from six commenters. The commenters were
the Air Line Pilots Association, International (ALPA); Delta Air Lines,
Inc. (Delta); FedEx Express (FedEx); MTU Maintenance Hannover GmbH
(MTU); The Boeing Company (Boeing); and United Airlines (UAL).
The following presents the comments received on the NPRM and the
FAA's response to each comment.
Requests To Revise Proposed BSI Requirement
Delta, MTU, and FedEx requested revisions to the BSI proposed in
the NPRM. The FAA details the comments to the BSI in the following
paragraphs but is not providing an individual response to each comment
given that the FAA removed the proposal for BSI from this AD.
Request To Increase the Compliance Time for Initial BSI To Allow
Sufficient Time To Complete Inspector Training
Delta requested that the compliance time of 500 FCs after the
effective date of this AD for the initial BSI proposed by paragraph
(g)(1)(i) of the NPRM be extended to account for the difference in
predicted flight utilization versus actual utilization as a result of
the COVID-19 pandemic. Delta cited concerns that the 500 FC compliance
time will not allow sufficient time for training inspectors to obtain
qualifications to perform the BSI proposed by paragraph (g)(1)(i) of
the NPRM. Delta noted that government restrictions and recommendations
on travel and class size for in-person on-site training plus the lack
of remote training opportunities represent obstacles to adequately
training inspectors.
Request To Update Repetitive BSI Language
Delta requested that the FAA update paragraph (g)(1)(ii) of the
NPRM from ``. . . perform the BSI required by paragraph (g)(1)(i) of
this AD within every 500 FCs since performance of the last BSI'' to ``.
. . perform the BSI required by paragraph (g)(1)(i) of this AD within
every 500 FCs since performance of the last BSI that was done per
paragraph (g)(1)(i) or (g)(1)(ii) of this AD.'' Delta reasoned that the
phrase ``last BSI'' of paragraph (g)(1)(ii) of the NPRM could cause
confusion since the ``last BSI'' is the ``initial BSI.''
Request To Clarify ``Before Further Flight''
Delta requested that the FAA update paragraph (g)(1)(iii) of the
NPRM to clarify the phrase ``before further flight.'' Delta asked
whether the action is to remove the engine before the flight of the
aircraft, or remove the HPT 2nd-stage air seal assembly and perform the
inspections proposed by paragraph (g)(2) of the NPRM before flight of
the engine. Delta stated there could be confusion that the aircraft is
prohibited from further flight until the HPT 2nd-stage air seal
assembly is removed from the engine.
Request To Include a Scenario When To Perform the BSI
Delta and MTU requested confirmation that the FAA included all the
non-modulated turbine cooling air (TCA) system engines population into
the proposed BSI requirement. MTU requested that the FAA update
paragraph (g)(1) of the NPRM to include engines that have deactivated/
mechanically disconnected the TCA system.
Request To Update the Costs of Compliance and Work Hours
FedEx requested that the hours to perform the BSI of the HPT 2nd-
stage air seal assembly be changed to 4.8 hours. FedEx cited PW Service
Bulletin (SB) PW2000 72-773, dated March 11, 2020 (PW SB PW2000 72-
773), that indicates that the on-wing inspection takes 4.8 hours and
not 2 work hours as indicated in the NPRM.
Request To Update the Terminating Action
FedEx requested that the FAA revise paragraph (h), Terminating
Action, of the NPRM from ``. . . terminating action for the repetitive
BSI requirements in paragraph (g)(1)(ii) of this AD'' to ``. . .
terminating action for the initial BSI requirement in paragraph
(g)(1)(i) and the repetitive BSI requirements in paragraph (g)(1)(ii)
of this AD.'' FedEx reasoned that an HPT 2nd-stage air seal assembly
could be removed for a reason unrelated to this AD and inducted for an
engine shop visit before the HPT 2nd-stage air seal assembly is subject
to the initial BSI proposed by paragraph (g)(1)(i) of the NPRM. As
written in the NPRM, FedEx suggested it could be interpreted that the
HPT 2nd-stage air seal assembly would still need an initial inspection
within 2,500 FCs after this unrelated engine shop visit.
Request To Clarify Revision of NDIP-1217
Delta requested clarification if this AD allows for any revision
level of Non-Destructive Inspection Procedure, Technique Sheet for
Detection of Cracking in the PW2000 HPT 2nd Stage Airseal by Borescope
Inspection Method (NDIP-1217). Delta cited paragraph (g)(1)(i) of the
NPRM that proposed to require PW SB PW2000 72-773, which references
NDIP-1217.
Request To Clarify Reporting
Delta requested clarification if paragraph (g)(1)(i) of the NPRM
proposed to require reporting of the inspection results to PW Materials
& Processes Engineering/Non-Destructive Evaluation Engineer. Delta
noted that paragraph (g)(1)(i) of the NPRM references paragraph 6 of PW
SB PW2000 72-773, which references NDIP-1217, which specifies reporting
of the inspection results.
Request To Approve Tooling Equivalent
Delta requested that their rotator be approved as a tooling
equivalent for performing the BSI proposed by paragraph (g)(1) of the
NPRM. Delta reasoned that they worked in conjunction with PW to approve
a tooling equivalent and requested confirmation that PW has the
authority to approve tooling equivalents and that an alternative method
of compliance request would not be required.
Delta also requested approval to deviate from paragraph 6.1.2 of
NDIP-1217 to remove the starter rather than the crank pad to use their
rotator.
Request To Allow HPT Rotating by Hand for BSI
Delta requested that the FAA allow the performance of the BSI of
the HPT 2nd-stage air seal assembly proposed by paragraph (g)(1) of the
NPRM to be rotated by hand rather than by a motor-driven unit per
paragraph 6 of NDIP-1217. Delta reasoned the motor-driven unit may not
be available at all stations and a second maintenance technician can
rotate the HPT rotor manually, which allows the inspector to use two
hands for the BSI.
Request To Confirm Affected Engine Serial Numbers
Delta commented that ``EagleNet case (CAS-83493-C0M6W0)'' was
submitted to P&W to confirm RTC engines cannot be converted to CET/pre-
CET engines or vice versa. Delta requested that the FAA confirm that
the list of affected engine serial numbers in the proposed AD is an
adequate method for controlling risk of affected population.
[[Page 40301]]
Comment on Operational and Economic Costs
FedEx commented that the proposed rule would impact approximately
half of its fleet of PW2000 model turbofan engines. The inspection
program itself will have a minor operational impact as it can be
incorporated into an existing hot section inspection program, but
unplanned engine changes will result in local operational impact. FedEx
noted that the cost of the on-wing inspection program [BSI] would be
minimal but the cost of engines that need to be removed immediately
will have a fairly significant impact. FedEx noted that these
operational and economic impacts are acceptable when weighed against
the impact of an in-service event.
FAA Response to Comments To Revise the BSI Inspection
The FAA determined the need to remove the proposed BSI requirement
from this AD based on comments regarding accessibility of inspector
training. The FAA may consider additional rulemaking and will consider
these comments in the development of any additional requirements.
Request That Individual Part Serviceability Not Depend on the
Inspection Results of Other Parts
Delta commented that individual part serviceability should not
depend on the inspection results of other parts. Delta also commented
that if inspections are not possible which would allow the mating HPT
1st-stage disk or the HPT 2nd-stage hub to be deemed serviceable,
independent from inspection status of the HPT 2nd-stage air seal
assembly, then the manufacturer should revise the engine manuals to
clarify that the mating HPT 1st-stage disk or HPT 2nd-stage hub cannot
be made serviceable unless an inspection of the HPT 2nd-stage air seal
assembly indicates it is free of cracks. Delta stated that this would
remove the possibility that the mating HPT 1st-stage disk or HPT 2nd-
stage hub would be made serviceable and then installed in an engine
before the HPT 2nd-stage air seal assembly is inspected.
The FAA did not revise this AD in response to this comment. A
crack, as identified in the shaded regions of Figure 1 to paragraph
(g)(1)(iii) of this AD (Figure 1), which extends towards the knife-edge
region of the HPT 2nd-stage air seal assembly, impacts the
serviceability of the mating HPT 1st-stage disk and the HPT 2nd-stage
hub. A crack identified in the shaded region of Figure 1 of this AD of
the HPT 2nd-stage air seal assembly results in the requirement to
remove the HPT 2nd-stage air seal assembly, mating HPT 1st-stage disk,
and HPT 2nd-stage hub.
Request To Remove Inspections for Parts Being Scrapped
Delta requested that the FAA update paragraph (g)(2)(i) of the NPRM
(paragraph (g)(1)(i) of this AD) to remove the visual inspection,
knife-edge coating strip, and FPI of the HPT 2nd-stage air seal
assembly if the HPT 2nd-stage air seal assembly, mating HPT 1st-stage
disk, and HPT 2nd-stage hub are being scrapped. Further, Delta
requested if the HPT 2nd-stage air seal assembly is planned to be
scrapped, then the mating HPT 1st-stage disk and HPT 2nd-stage hub be
allowed to be made serviceable without FPI of the HPT 2nd-stage air
seal assembly.
The FAA disagrees with the need to change the AD based on this
comment. If the HPT 2nd-stage air seal assembly, HPT 1st-stage disk,
and HPT 2nd-stage hub are removed from service, then the inspections
required by paragraph (g)(1)(i) of this AD are not applicable. The
inspections are required only if the operator returns the parts to
service.
FPI is the only way to ensure the HPT 2nd-stage air seal assembly
is free from cracks because an FPI will reveal cracks not detected by a
visual inspection. The serviceability of the both the HPT 1st-stage
disk and HPT 2nd-stage hub is directly dependent on the HPT 2nd-stage
air seal assembly. If an operator does not FPI the HPT 2nd-stage air
seal assembly, then neither the HPT 1st-stage disk nor HPT 2nd-stage
disk can be returned to service. The FAA did not change this AD.
Request To Reference Engine Manual for Inspection Instructions
FedEx requested that the FAA update paragraph (g)(2)(i) of the NPRM
(paragraph (g)(1)(i) of this AD) to reference Chapter 72-52-60,
Inspection/Check-01, of the PW2000 Series Engine Manual for
instructions to perform the visual inspection, knife-edge coating
removal, and FPI of the HPT 2nd-stage air seal assembly.
The FAA determined it is not necessary to require use of specific
service information as the visual inspection and FPI required by
paragraph (g)(1)(i) of this AD are routine inspections that may vary
between operators. The FAA, however, revised paragraph (g)(1)(i) of
this AD to refer to Chapter 72-52-60, Repair-01, of the PW2000 Series
Engine Manual for guidance on striping the knife edge coating from the
HPT 2nd-stage air seal assembly.
Request To Remove FPI
Delta requested that paragraph (g)(2)(ii) of the NPRM (paragraph
(g)(1)(ii) of this AD) remove the proposed requirement to perform an
FPI and require only visual inspections of the HPT 2nd-stage air seal
assembly. Delta reasoned that based on NDIP-1217, cracks are detectable
by visual inspection, thereby making FPI unnecessary. Delta concluded
that performing only the visual inspection enables the HPT 2nd-stage
air seal assembly to be inspected at initial disassembly while still in
the presence of the mating HPT 1st-stage disk and HPT 2nd-stage hub,
which simplifies determining if parts need to be scrapped if a crack is
found. Otherwise, Delta stated that paragraph (g)(1)(iii) of the NPRM
creates a logistical challenge for performing inspections as the HPT
2nd-stage air seal assembly, mating HPT 1st-stage disk, and HPT 2nd-
stage hub could be routed to different locations with different lead
times.
The FAA disagrees. While cracks may be detected by visual
inspection, an FPI will reveal cracks not detected by visual
inspection. Additionally, the FPI is required to confirm that the HPT
2nd-stage air seal assembly is free of cracks. The FAA did not change
this AD.
Request To Allow Repair of the HPT 2nd-Stage Air Seal Assembly
Delta and MTU requested that paragraph (g)(2)(ii) of the NPRM
(paragraph (g)(1)(ii) of this AD) be updated to allow repair of the HPT
2nd-stage air seal assembly if a crack is found. The commenters
reasoned that Chapter 72-52-60, Inspection/Check-01 and Repair-02, of
the PW2000 Series Engine Manual provides information for repairing a
cracked HPT 2nd-stage air seal assembly. The commenters concluded that
this AD should allow repair; otherwise, Chapter 72-52-60 of the PW2000
Series Engine Manual should be deleted or updated.
The FAA disagrees that the crack repairs identified in the engine
manual should be incorporated in this AD. If a crack is found during
the inspections required by this AD for the HPT 2nd-stage air seal
assembly, the part must be removed from service and cannot be repaired.
The FAA disagrees that Chapter 72-52-60 of the PW2000 Series Engine
Manual should be deleted or updated. This repair is specifically for
mechanical damage such as handling damage and foreign object damage in
the knife edge area. This repair is not applicable to cracks identified
by this AD. The damage addressed is unrelated and the repair does not
need to be
[[Page 40302]]
prohibited. The requirements contained in this AD take precedence over
any contrary provisions in the manufacturer's instructions for
continued airworthiness. The FAA did not update this AD.
Request To Clarify Removal From Service
Delta requested that the FAA clarify paragraph (g)(2)(ii) of the
NPRM (paragraph (g)(1)(ii) of this AD) that states the HPT 2nd-stage
air seal assembly must be removed from service if a crack is found.
Delta asked if the HPT 2nd-stage air seal assembly must be scrapped, or
if the HPT 2nd-stage air seal assembly can be repaired and returned to
service after re-identifying it with a new P/N. Delta added that the
engine manual provides a repair option of knife-edge cracks caused by
mechanical damage.
The FAA notes that ``remove from service'' in this AD indicates
that the HPT 2nd-stage air seal assembly should be permanently removed
from service if a crack is found. Any cracked HPT 2nd-stage air seal
assembly cannot be repaired and returned to service per the
requirements of this AD.
Request To Remove ``Before Further Flight''
FedEx requested that the FAA remove the phrase ``before further
flight'' from paragraphs (g)(2)(ii) and (iii) of the NPRM (paragraphs
(g)(1)(ii) and (iii) of this AD). FedEx reasoned that since the visual
inspection, knife edge coating removal, and FPI are performed at every
piece-part opportunity of the mating HPT 1st-stage disk, HPT 2nd-stage
disk, or the HPT 2nd-stage air seal assembly, ``before further flight''
is redundant. Additionally, FedEx stated that the overhaul facility
must comply with the engine manual inspection criteria and would have
no other option but to make the HPT 2nd-stage air seal assembly
permanently unserviceable.
The FAA agrees and removed ``before further flight'' from
paragraphs (g)(1)(ii) and (iii) of this AD.
Request To Clarify Part Replacement After Crack Is Found
MTU requested clarification regarding whether the mating HPT 1st-
stage disk or HPT 2nd-stage hub needs to be replaced if a crack is
found after performing the inspections proposed by paragraph
(g)(2)(iii) of the NPRM (paragraph (g)(1)(iii) of this AD), or if both
the mating HPT 1st-stage disk and HPT 2nd-stage hub need to be
replaced.
If a crack is found as identified in the shaded region of Figure 1
to paragraph (g)(1)(iii) of this AD (Figure 1) that extends toward the
knife-edge region of the HPT 2nd-stage air seal assembly, this AD
requires replacement of the HPT 2nd-stage air seal assembly, mating HPT
1st-stage disk, and HPT 2nd-stage hub.
Request To Clarify Terminating Action
UAL requested clarification if paragraph (h), Terminating Action,
of the NPRM applies to the visual inspection and FPI of the HPT 2nd-
stage air seal assembly proposed by paragraph (g)(2) of the NPRM
(paragraph (g)(1) of this AD).
The FAA notes that there is no terminating action to the visual
inspection and FPI of the HPT 2nd-stage air seal assembly required by
paragraph (g)(1) of this AD. The visual inspection and FPI required by
paragraph (g)(1) of this AD are required for all HPT 2nd-stage air seal
assemblies, including P/Ns others than 1A8209 or 1A8209-001. As stated
in an earlier response, with the removal of the BSI requirements from
this AD, the FAA removed the terminating action from this AD.
Request To Clarify Applicability for Visual Inspection and FPI
UAL requested clarification of whether paragraph (g)(1) of this AD
applies if an HPT 2nd-stage air seal assembly, with a P/N other than P/
N 1A8209 or 1A8209-001, is installed.
Delta requested that an applicability statement referencing P/Ns
for affected HPT 2nd-stage air seal assemblies be added to paragraph
(g)(2) of the NPRM. Paragraph (g)(2) of the NPRM proposed to require a
visual inspection of the HPT 2nd-stage air seal assembly, stripping the
knife edge coating from the HPT 2nd-stage air seal assembly, and then
performing an FPI of the HPT 2nd-stage air seal assembly. Delta noted
that if an HPT 2nd-stage air seal assembly has been modified and re-
identified with a new P/N using PW SB PW2000 72-754, Revision No. 2,
dated April 30, 2019, then it should not be subject to the same
inspections as HPT 2nd-stage air seal assembly, P/N 1A8209 or 1A8209-
001.
The FAA disagrees and notes that the visual inspection and the FPI
required by paragraph (g)(1)(i) of this AD are required for all HPT
2nd-stage air seal assemblies, regardless of the P/N. The FAA did not
update this AD.
Request To Allow Installation of Mating Parts Without Past HPT 2nd-
Stage Air Seal Assembly Inspection Verification
Delta requested that a mating HPT 1st-stage disk and HPT 2nd-stage
hub made serviceable before the effective date of this AD be eligible
for installation without verification that all past HPT 2nd-stage air
seal assemblies had visual inspections and FPI to verify no cracks were
found. Delta reasoned that the inspections were not previously required
and adequate records may not exist. Additionally, Delta stated it might
not be possible to re-inspect all previous HPT 2nd-stage air seal
assemblies for cracks as some may have been scrapped before the
inspection.
The FAA notes that an HPT 1st-stage disk and HPT 2nd-stage hub made
serviceable before the effective date of this AD are not subject to the
requirements of (g)(1)(iii) of the AD until their next piece part
exposure. The FAA did not update this AD.
Request To Clarify the Location of the Forward and Aft Edges
Delta and MTU requested that the FAA clarify the location of the
forward and aft edges of the HPT 2nd-stage air seal assembly. Delta
asked if the forward edge is the barrel section forward of the #1
knife-edge or any part that extends beyond the barrel section.
The FAA removed references to ``forward edge'' and ``aft edge'' of
the HPT 2nd-stage air seal assembly from this AD. In their place, the
FAA added Figure 1 to paragraph (g)(1)(iii) of this AD to specify the
locations of the HPT 2nd-stage air seal assembly that require
inspection for cracks.
Request To Clarify the Definition of Through-Crack
Delta and FedEx requested that the FAA clarify the definition of
``through-crack.'' Delta asked if a ``through-crack'' is a crack going
through the axial direction or radial direction of the HPT 2nd-stage
air seal assembly. Delta referenced Figure 5 of NDIP-1217 that appears
to show a through-crack in the axial direction. Delta inferred from
paragraph (i)(4) of the NPRM that a through-crack is in the radial
direction. Delta requested a diagram to help illustrate what
constitutes a through-crack.
FedEx stated that a lenticular seal is a two-piece component that
becomes an inseparable assembly during manufacturing. As a result, it
would be impossible to distinguish a through-crack from a surface crack
over a large area of the HPT 2nd-stage air seal assembly's exterior
since its interior surfaces are inaccessible. FedEx cited Chapter 72-
52-60, Inspection/Check-01, Figures 801 and 801A, of the PW2000 Series
Engine Manual, which highlights areas where through-thickness cracks
are critical. According to FedEx, however, these images fail to address
the ability to determine whether a surface crack is a ``through-
crack.'' Additionally, the PW2000 Series Engine
[[Page 40303]]
Manual does not provide dimensions that bound the areas making HPT disk
replacement subjective.
The FAA agrees that it is difficult to differentiate between a
surface crack and through-crack; therefore, the FAA removed references
to ``through-crack'' from this AD. The FAA notes that any crack, in any
direction, found in the HPT 2nd-stage air seal assembly, requires
removal of the HPT 2nd-stage air seal assembly from service. As stated
in an earlier response, the FAA added Figure 1 to show the locations of
the HPT 2nd-stage air seal assembly that require inspection for cracks.
However, the FAA is not providing dimensions that bind the areas. If
the inspections of the HPT 2nd-stage air seal assembly reveal a crack
in the shaded regions of Figure 1, which extends towards the knife-edge
region, the HPT 2nd-stage air seal assembly must be removed from
service.
Request To Clarify Engine Shop Visit
Delta requested that the FAA clarify the definition of ``engine
shop visit'' related to which engine flanges the FAA considers ``major
mating engine flanges.'' Delta requested that the FAA exclude the low-
pressure compressor (LPC) module flange as a major mating engine flange
because LPC module life limited parts (LLPs) can be swapped while the
engine is installed on the aircraft. Delta reasoned that the separation
of the LPC module flange should not require replacement of the HPT 2nd-
stage air seal assembly. These LPC swaps may extend time between engine
shop visits if the LLPs are located in the LPC.
The FAA determined the need to revise the definition of ``engine
shop visit'' by replacing separation of ``major mating engine flanges''
with separation of the ``N or M engine flange.'' If the LPC swap does
not involve separating the N or M engine flange, then the compliance
time for replacing the HPT 2nd-stage air seal assembly has not occurred
as required by this AD.
Request To Update the Definition of Piece-Part Opportunity
Delta requested that the FAA update the definition of ``piece-part
opportunity'' from ``when the part is completely disassembled'' to
``any time the seal is removed from the HPT module.'' Delta reasoned
that while the HPT 2nd-stage air seal assembly is referred to as an
``assembly,'' the HPT 2nd-stage air seal assembly cannot be dissembled.
The FAA partially agrees and updated the definition to clarify what
constitutes ``piece-part opportunity'' for the HPT 1st-stage disk, HPT
2nd-stage hub, and HPT 2nd-stage air seal assembly.
Request To Update the Definition of Part Eligible for Installation
Delta requested that the FAA update the definition of ``part
eligible for installation'' to remove paragraph (i)(3)(ii) and to refer
only to ``An HPT 2nd-stage air seal assembly that is not P/N 1A8209 or
1A8209-001.'' Delta reasoned that paragraph (i)(3)(ii) of the NPRM,
which states that an HPT 2nd-stage air seal assembly that has been
modified using the service information is eligible for installation, is
unnecessary because the HPT 2nd-stage air seal assembly receives a new
P/N, which is not P/N 1A8209 or 1A8209-001, after repair.
The FAA agrees and revised the definition of an HPT 2nd-stage air
seal assembly that is eligible for installation, now in paragraph
(h)(3) of this AD, to refer to an HPT 2nd-stage air seal assembly with
a P/N other than 1A8209 or 1A8209-001.
Request To Update Service Information Revision
MTU requested that the FAA reference PW SB PW2000 72-754, Revision
No. 3, dated August 14, 2019, in this AD instead of Revision No. 2,
dated April 30, 2019.
The FAA agrees. The FAA updated PW SB PW2000 72-754 to Revision No.
3, dated August 14, 2019, throughout this AD.
Request To Update the Service Information Description
MTU requested that the FAA update the service information
description in the Other Related Service Information paragraph of the
NPRM (Related Service Information of this AD) to include the
replacement and modification of the HPT 2nd-stage air seal assembly.
The FAA agrees. The FAA updated the service information description
in the Related Service Information paragraph in this AD.
Request To Update the Costs of Compliance
UAL requested that the Costs of Compliance include additional costs
such as delays in engine builds and modifications. UAL reasoned that
piece-part modification of the HPT 2nd-stage air seal assembly, mating
HPT 1st-stage disk, and HPT 2nd-stage hub are independent of each
other. Scraping all parts proposed by paragraph (g)(2)(iii) of the NPRM
(paragraph (g)(1)(iii) of this AD) will force engine centers to delay
routing the mating HPT 1st-stage disk and HPT 2nd-stage hub for
modification until the HPT 2nd-stage air seal assembly is inspected,
thus delaying an engine build or incurring costs while the mating HPT
1st-stage disk and HPT 2nd-stage hub are partially or fully scrapped.
The FAA disagrees with updating the costs of compliance. The cost
analysis in AD rulemaking actions typically includes only the costs
associated with complying with the AD and does not include secondary
costs. The FAA's cost estimate includes the work hours and parts costs
to perform the required actions.
No Comments on This AD
ALPA supported the AD and appreciated the opportunity to comment.
Boeing had no comments.
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 PW2000 72-754, Revision No. 3, dated August
14, 2019, and PW SB PWF117 72-402, Revision No. 2, dated May 3, 2019.
The SBs describe procedures for replacing or modifying the HPT 2nd-
stage air seal assembly.
Interim Action
The FAA considers this AD to be an interim action. The FAA may
consider additional rulemaking based on further investigation of the
unsafe condition.
Costs of Compliance
The FAA estimates that this AD affects 445 engines installed on
airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:
[[Page 40304]]
Estimated Costs
----------------------------------------------------------------------------------------------------------------
Cost per Cost on U.S.
Action Labor cost Parts cost product operators
----------------------------------------------------------------------------------------------------------------
Visually inspect, strip the knife edge 10 work-hours x $85 per $0 $850 $378,250
coating, and FPI the HPT 2nd-stage hour = $850.
air seal assembly.
----------------------------------------------------------------------------------------------------------------
The FAA estimates the following costs to do any necessary
replacements. The FAA has no way of determining how many replacements
of the HPT 2nd-stage air seal assembly will be done with a modified HPT
2nd-stage air seal assembly and how many will be done with a new HPT
2nd-stage air seal assembly. The FAA also has no way of determining the
number of engines that might need replacement of the HPT 2nd-stage air
seal assembly, HPT 1st-stage disk, and HPT 2nd-stage hub.
On-Condition Costs
----------------------------------------------------------------------------------------------------------------
Cost per
Action Labor cost Parts cost product
----------------------------------------------------------------------------------------------------------------
Replace the HPT 2nd-stage air seal assembly 10 work-hours x $85 per hour = $5,000 $5,850
with modified HPT 2nd-stage air seal assembly. $850.
Replace the HPT 2nd-stage air seal assembly 0.25 work-hours x $85 per hour = 355,000 355,021.25
with new seal assembly. $21.25.
Replace the HPT 2nd-stage air seal assembly, 0.25 work-hours x $85 per hour = 970,000 970,021.25
HPT 1st-stage disk, and HPT 2nd-stage hub $21.25.
(based on FPI results).
----------------------------------------------------------------------------------------------------------------
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:
2021-14-13 Pratt & Whitney: Amendment 39-21640; Docket No. FAA-2020-
0442; Project Identifier AD-2020-00260-E.
(a) Effective Date
This airworthiness directive (AD) is effective September 1,
2021.
(b) Affected ADs
None.
(c) Applicability
This AD applies to all Pratt & Whitney (PW) PW2037, PW2037M,
PW2040, and F117-PW-100 model turbofan engines.
(d) Subject
Joint Aircraft System Component (JASC) Code 7250, Turbine
Section.
(e) Unsafe Condition
This AD was prompted by a report of an uncontained engine
failure resulting from cracks originating in the knife edge of the
high-pressure turbine (HPT) 2nd-stage air seal assembly. The FAA is
issuing this AD to prevent failure of the HPT 2nd-stage air seal
assembly. The unsafe condition, if not addressed, could result in
uncontained HPT 2nd-stage air seal assembly release, 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) Visual Inspection and Fluorescent Penetrant Inspection (FPI) of
HPT 2nd-Stage Air Seal Assembly
After the effective date of this AD, at every piece-part
opportunity of the HPT 1st-stage disk, HPT 2nd-stage hub, or the HPT
2nd-stage air seal assembly:
(i) Perform a visual inspection of the HPT 2nd-stage air seal
assembly, strip the knife edge coating from the HPT 2nd-stage air
seal assembly, and then perform an FPI of the HPT 2nd-stage air seal
assembly.
Note 1 to paragraph (g)(1)(i): Guidance on striping the knife
edge coating from the HPT 2nd-stage air seal assembly required by
paragraph (g)(1)(i) of this AD can be found Chapter 72-52-60,
Repair-01, of the PW2000 Series Engine Manual.
(ii) If a crack is found in the HPT 2nd-stage air seal assembly
during the visual inspection or FPI required by paragraph (g)(1)(i)
of this AD, remove the HPT 2nd-stage air seal assembly from service
and replace it with a part eligible for installation.
[[Page 40305]]
(iii) During the visual inspection or FPI required by paragraph
(g)(1)(i) of this AD, if a crack is found in the shaded regions of
the HPT 2nd-stage air seal assembly identified in Figure 1 to
paragraph (g)(1)(iii) of this AD (Figure 1), which extends towards
the knife-edge region of the HPT 2nd-stage air seal assembly, remove
the HPT 2nd-stage air seal assembly, mating HPT 1st-stage disk, and
HPT 2nd-stage hub from service, and replace the parts with parts
eligible for installation. In order to return the mating HPT 1st-
stage disk and HPT 2nd-stage hub to service, the inspections of the
HPT 2nd-stage air seal assembly cannot reveal a crack identified in
the shaded regions of Figure 1, which extends towards the knife-edge
region.
[GRAPHIC] [TIFF OMITTED] TR28JY21.013
(2) Replacement of HPT 2nd-Stage Air Seal Assembly
(i) For PW PW2037, PW2037M, and PW2040 model turbofan engines,
at the next engine shop visit after the effective date of this AD,
remove the HPT 2nd-stage air seal assembly, part number (P/N) 1A8209
or 1A8209-001, and replace it with a part eligible for installation.
(ii) For PW F117-PW-100 model turbofan engines, at the next
piece part opportunity after the effective date of this AD, remove
the HPT 2nd-stage air seal assembly, P/N 1A8209 or 1A8209-001, and
replace it with a part eligible for installation.
(h) Definitions
(1) 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 the N or M engine flange. The separation of engine
flanges solely for the purposes of transportation of the engine
without subsequent engine maintenance does not constitute an engine
shop visit.
(2) For the purpose of this AD, a ``piece-part opportunity'' is:
(i) For the HPT 1st-stage disk, when the disk is removed from
the engine and all the blades are removed;
(ii) For the HPT 2nd-stage hub, when the hub is removed from the
engine and all the blades are removed; or
(iii) For the HPT 2nd-stage air seal assembly, when the assembly
is removed from either the HPT 1st-stage disk or the HPT 2nd-stage
hub.
(3) For the purpose of this AD, a ``part eligible for
installation'' is an HPT 2nd-stage air seal assembly with a P/N
other than 1A8209 or 1A8209-001.
(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:
<a href="/cdn-cgi/l/email-protection#7c3d3239513d38513d31333f3c1a1d1d521b130a"><span class="__cf_email__" data-cfemail="bcfdf2f991fdf891fdf1f3fffcdadddd92dbd3ca">[email protected]</span></a>.
(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.
[[Page 40306]]
(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: <a href="/cdn-cgi/l/email-protection#9cfffdeef3f0b2f2fbe9e5f9f2dcfafdfdb2fbf3ea"><span class="__cf_email__" data-cfemail="731012011c1f5d1d14060a161d331512125d141c05">[email protected]</span></a>.
(k) Material Incorporated by Reference
None.
Issued on June 30, 2021.
Ross Landes,
Deputy Director for Regulatory Operations, Compliance & Airworthiness
Division, Aircraft Certification Service.
[FR Doc. 2021-15947 Filed 7-27-21; 8:45 am]
BILLING CODE 4910-13-P
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