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Federal Register / Vol. 86, No. 142 / Wednesday, July 28, 2021 / Rules and Regulations
Discussion of Final Airworthiness Directive
Request To Clarify Before Further Flight
Comments
Delta requested that the FAA update paragraph g1iii 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 2ndstage air seal assembly and perform the inspections proposed by paragraph g2 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 2ndstage air seal assembly is removed from the engine.

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 FAAs 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 g1i of the NPRM be extended to account for the difference in predicted flight utilization versus actual utilization as a result of the COVID19
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 g1i of the NPRM. Delta noted that government restrictions and recommendations on travel and class size for in-person onsite training plus the lack of remote training opportunities represent obstacles to adequately training inspectors.

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Request To Update Repetitive BSI
Language Delta requested that the FAA update paragraph g1ii of the NPRM from . . . perform the BSI required by paragraph g1i of this AD within every 500 FCs since performance of the last BSI to . . . perform the BSI
required by paragraph g1i of this AD within every 500 FCs since performance of the last BSI that was done per paragraph g1i or g1ii of this AD. Delta reasoned that the phrase last BSI of paragraph g1ii of the NPRM could cause confusion since the last BSI is the initial BSI.

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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 g1 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 72773, dated March 11, 2020
PW SB PW2000 72773, 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 g1ii of this AD to . . . terminating action for the initial BSI requirement in paragraph g1i and the repetitive BSI
requirements in paragraph g1ii 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 g1i 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.

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Request To Clarify Revision of NDIP
1217
Delta requested clarification if this AD
allows for any revision level of NonDestructive Inspection Procedure, Technique Sheet for Detection of Cracking in the PW2000 HPT 2nd Stage Airseal by Borescope Inspection Method NDIP1217. Delta cited paragraph g1i of the NPRM that proposed to require PW SB PW2000 72773, which references NDIP1217.
Request To Clarify Reporting Delta requested clarification if paragraph g1i of the NPRM
proposed to require reporting of the inspection results to PW Materials &
Processes Engineering/Non-Destructive Evaluation Engineer. Delta noted that paragraph g1i of the NPRM
references paragraph 6 of PW SB
PW2000 72773, which references NDIP1217, 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 g1 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 g1 of the NPRM to be rotated by hand rather than by a motordriven 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 CAS83493C0M6W0 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.

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