Voglio sapere a riguardo di…

Federal Register / Vol. 86, No. 96 / Thursday, May 20, 2021 / Rules and Regulations to address the unsafe condition on these products.
Discussion of Final Airworthiness Directive Comments The FAA received comments from nine commenters. The commenters were Air Line Pilots Association, International ALPA; American Airlines AAL; Azur Aviation Azur;
The Boeing Company Boeing; CFM;
Delta Air Lines, Inc. Delta; United Airlines UAL; MTU Maintenance Canada MTU and Magnetic MRO. Four of the nine commenters requested changes that resulted in updates to this AD. Three commenters requested clarification on definitions. Two commenters requested updates to the service information. Two commenters expressed support for the AD. The following presents the comments received on the NPRM and the FAAs response to each comment.
Request To Clarify Parts That Can Be Returned to Service Azur requested that the FAA clarify the parts that can be returned to service after removal. Azur reasoned that paragraph g1 of this AD requires that an HPT inner stationary seal be removed from service and replaced with either a part that is not listed in the service information or a repaired part identified in paragraph h2, Definitions, of this AD. In contrast, paragraphs g3i and iii of this AD, respectively, indicate only to remove the rotating air HPT
front seal and No. 3 ball bearing from service and replace them with a part eligible for installation.
Azur suggested adding one of the following to this AD to remove the ambiguity: 1 Remove remove from service from paragraph g1 of this AD; 2 Identify rotating air HPT front seals and No. 3 ball bearings that are not eligible for installation; 3 Add an Installation Prohibition paragraph for the removed rotating air HPT front seal and No. 3 ball bearing; 4 Indicate what to do with the removed rotating air HPT
front seal and No. 3 ball bearing in paragraphs g3i and iii of this AD, such as discard these parts; or 5
Identify instruction for the removed rotating air HPT front seals and No. 3
ball bearings.
Use of remove from service in this AD indicates that the rotating air HPT
front seal and No. 3 ball bearing should no longer be installed on an engine.
Therefore, neither the removed rotating air HPT front seal nor the removed No.
3 ball bearing can be repaired and returned to service. The FAA, however,
VerDate Sep<11>2014

16:06 May 19, 2021

Jkt 253001

updated paragraph h, Definitions, of this AD, to clarify that a part eligible for installation for both a rotating air HPT
front seal and a No. 3 ball bearing refers to parts that were not removed from service based on the findings of honeycomb separation of the HPT inner stationary seal. The FAA also updated paragraph g1 of this AD to remove remove from service to clarify that the HPT inner stationary seal can be repaired and returned to service. The FAA also moved the definition of an HPT inner stationary seal that is eligible for installation from paragraph g1 to paragraph h1 of this AD.
Request To Update the Definition of Engine Shop Visit AAL, Delta, and UAL requested updates or clarification of the definition of an engine shop visit provided in paragraph h1 of this AD.
AAL requested that the FAA update the definition of an engine shop visit to clarify circumstances that are not an engine shop visit. AAL reasoned that CFM Service Bulletin SB CFM567B
S/B 720972 provides guidance on when AD mandated actions can be accomplished to avoid undue burden on operators, specifically in circumstances when engines are inducted to the shop for quick corrective action, such as repair for foreign object damage.
UAL requested that the FAA update the definition of an engine shop visit to specify which major mating engine case flanges need to be separated to be an engine shop visit as defined. UAL stated that the ambiguity of the major mating engine case flange may result in an inspection of the HPT inner stationary seal for honeycomb separation when the core is not exposed, such as during fan case replacement.
Delta recommended that the manufacturer define engine shop visit in its service information.
The FAA agrees that the definition of an engine shop visit in this AD does not include the separation of engine flanges solely for the purpose of transportation of the engine or replacing the fan or propulsor without subsequent maintenance. All other separations of major mating engine case flanges are an engine shop visit, as defined, and require removal, replacement, and inspection of the HPT inner stationary seal as required by paragraphs g1 and 2 of this AD. The FAA changed the definition of engine shop visit in paragraph h this AD to clarify the definition of an engine shop visit.
The FAA did not revise this AD in response to Deltas comment. The FAA
notes, however, that in CFM Service Bulletin SB CFM565B S/B 720952,
PO 00000

Frm 00005

Fmt 4700

Sfmt 4700

27265

Revision 01, and CFM SB CFM567B
S/B 721054, Revision 01, both dated January 15, 2020, the manufacturer updated the SBs to clarify that the quick turn shop visit type is not included in the SBs definition of shop visit.
Request To Change Inspection of HPT
Rotor Blade To Remove Debris AAL requested that the FAA change paragraph g3ii of this AD to Remove the HPT rotor blade from service and inspect per CFM567B
CFMITP.SM.10 Engine Shop Manual ESM 72520109 High Pressure Turbine Rotor BladesInspection 001
or replace with parts eligible for installation. AAL reasoned that the HPT rotor blade collects various types of debris over its service life, so attempting to determine if the debris is honeycomb material based upon a general visual inspection is subjective and open to interpretation. Therefore, AAL
suggested that removing the HPT rotor blades would ensure that the repair facility could remove the debris in the internal cavities and return the HPT
rotor blades to service.
Since the NPRM was published, the manufacturer revised the service information, removing the inspection of the HPT rotor blade internal cavities for honeycomb metal debris. As a result, the FAA changed paragraph g3ii of this AD to eliminate the requirement to inspect the HPT rotor blade internal cavities for honeycomb metal debris.
The FAA also removed the estimated cost associated with the inspection of the HPT rotor blade internal cavities for honeycomb metal debris from this AD.
Request To Clarify Reason To Replace No. 3 Ball Bearing Magnetic MRO requested clarification for the reason to replace the No. 3 ball bearing if metal debris is found in the HPT blade cavities.
In the NPRM, the FAA proposed to require replacement of the No. 3 ball bearing if honeycomb separation was found during the inspection required by paragraph g2 of this AD. The replacement of the No. 3 ball bearing is not linked to a finding of debris in the HPT rotor blade internal cavities but is required if honeycomb separation is found. Honeycomb separation results in increased secondary air flow impinging on the rotating air HPT front seal, which increases the axial load on the No. 3 ball bearing. This increased axial load impacts the durability of the No. 3 ball bearing. The FAA did not change this AD based on this comment.

E:FRFM20MYR1.SGM

20MYR1