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Federal Register / Vol. 86, No. 33 / Monday, February 22, 2021 / Rules and Regulations
Request for Clarification of Compliance Time SWA asked for clarification of the reference in paragraph g of the proposed AD to the applicable times specified in the Compliance paragraph of Boeing Alert Requirements Bulletin 73752A1180 RB, dated January 24, 2020. SWA asked if once it is determined that a P/N 141A61043
fitting is installed on a door through records or survey, the fitting must be replaced before further flight or whether it can be replaced at a later date as long as the door is still within its required compliance time per the referenced service information.
Table 1: Forward Entry Door Number 7 Stop Fitting Assembly Inspection of Paragraph 3., Compliance of Boeing Service Bulletin 73752A1180, dated January 24, 2020, gives the compliance time for replacing the P/N 141A61043
fitting if found. The compliance time is before 10,000 total flight cycles on the forward entry door, or within 5,000
forward entry door flight cycles after the original issue date of Boeing Alert Requirements Bulletin 73752A1180
RB, dated January 24, 2020, whichever occurs later. However, under paragraph h of this AD, the date for determining compliance time is the effective date of this AD, and not the issue date of the bulletin. Therefore, the FAA clarifies that if the compliance time has not yet been reached, then the fitting does not need to be replaced before further flight.
The FAA has not changed this AD in this regard.

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Request To Change Parts Installation Prohibition Paragraph SWA asked that the FAA reword paragraph i of the proposed AD to require compliance with the service information before installation of the fitting instead of prohibiting installation of the fitting.
The intent of paragraph i of this AD
is to prohibit installation of an affected part on an airplane with a compliance time for this prohibition related to the airplane configuration and whether the actions specified in Boeing Alert Requirements Bulletin 73752A1180
RB, dated January 24, 2020, must be accomplished on that airplane. The FAA has not made the changes requested by the commenter. However,
the FAA has revised paragraph i of this AD to clarify that, for any airplane required to accomplish the actions required by paragraph g of this AD, the parts installation prohibition does not take effect until the applicable actions required by paragraph g of this AD
have been accomplished on that airplane. For airplanes having an original airworthiness certificate or original export certificate of airworthiness dated after the effective date of this AD, the parts installation prohibition continues to be applicable as of the effective date of this AD.
Request for Correction of Error in Service Information AIRDO requested the FAA correct an error in the service information incorporated by reference in paragraph g of the proposed AD. AIRDO noted that page 13 of Boeing Alert Requirements Bulletin 73752A1180
RB, dated January 24, 2020, refers to the procedures in SB 74752A1180 when the correct reference is SB 737
52A1180.
The FAA agrees with the commenters request. The FAA has added paragraph h3 of this AD to clarify the correct service information reference.
Request To Limit the Applicability American Airlines AA and AIRDO
requested the FAA limit the applicability of the proposed AD to the line numbers L/Ns identified in the effectivity of Boeing Alert Service Bulletin 73752A1180, dated January 24, 2020. AA stated that because the aircraft illustrated parts catalog IPC
does not allow for the unsafe part to be installed on aircraft beyond L/N 1075, or on the door assemblies allowed to be installed on aircraft beyond L/N 1075, including all Model 737600, 700, 700C, 800, 900, and 900ER series airplanes in the applicability of the proposed AD is unnecessarily redundant. AIRDO stated Boeing has not allowed operators to install P/Ns 141A61043, 141A61501, 141A6150
2, and 141A6100678 on airplanes other than those with L/N 11075 per the IPC
and related drawings. AIRDO also stated that if the fitting or the door assembly must be replaced, operators will check the IPC and drawing to confirm if the affected part number can be used on the
specific airplane. AIRDO stated that based on this general protocol, even though the fitting and door assembly are physically interchangeable, a suspected fitting and door assembly cannot be installed on airplanes having L/N 1076
and subsequent.
The FAA does not agree with the requests to limit the applicability. Both the stop fitting assemblies and the doors they are installed on are physically interchangeable among the airplane models listed in the applicability of this AD. The FAA has determined it is necessary to ensure these rotable parts will not be introduced on other airplanes by including these airplanes in the applicability of this AD.
Therefore, the FAA has not changed this AD in this regard.
Conclusion The FAA reviewed the relevant data, considered the 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 in these products. Except for the 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 Under 1
CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 73752A1180
RB, dated January 24, 2020. The service information specifies procedures for an inspection, a measurement, or a records check of the upper aft corner stop fitting assembly to determine the part number, and applicable on-condition actions.
The on-condition action is to replace the affected stop fitting assembly with a newly designed stop fitting assembly that has improved wall thickness and strength. 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.
Costs of Compliance The FAA estimates that this AD
affects 1,075 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:

ESTIMATED COSTS FOR REQUIRED ACTIONS
Action
Labor cost
Inspection and part replacement ..

Up to 4 work-hours $85 per hour = Up to $340

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Parts cost
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$4,640

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Cost per product
Cost on U.S.
operators
Up to $4,980

Up to $5,353,500.

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