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Federal Register / Vol. 86, No. 84 / Tuesday, May 4, 2021 / Rules and Regulations
Greg Rutar, Aerospace Engineer, Airframe Section, FAA, Seattle ACO Branch, 2200
South 216th St., Des Moines, WA 98198;
phone and fax: 2062313529; email:
Greg.Rutar@faa.gov.
SUPPLEMENTARY INFORMATION:
FOR FURTHER INFORMATION CONTACT:

Background The FAA issued a notice of proposed rulemaking NPRM to amend 14 CFR
part 39 to supersede AD 20192210, Amendment 3919789 84 FR 61533, November 13, 2019 AD 20192210.
AD 20192210 applied to all The Boeing Company Model 737600, 700, 700C, 800, 900, and 900ER series airplanes. The NPRM published in the Federal Register on September 8, 2020
85 FR 55391. The NPRM was prompted by an engineering analysis of the inspection reporting results and metallurgical evaluation of the submitted frame fitting assemblies, which indicated that the initial inspection threshold for Model 737
900ER series airplanes and the repetitive inspection interval for all affected airplanes are inadequate to address the cracking in a timely manner.
For certain airplanes, the NPRM
proposed to reduce the compliance time for the initial inspection, and for all airplanes the NPRM proposed to reduce the repetitive inspection interval.
Comments The FAA gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM and the FAAs response to each comment.

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Request To Extend the Compliance Time for the Reporting Requirement American Airlines AA asked that the compliance time for the reporting requirements in paragraphs h and k of the proposed AD be extended to 30
days after the date of inspection. AA
stated that the cracking of the station STA 663.75 fitting is now a known problem, and Boeing has been receiving reports for almost a year. AA added that extending the reporting requirement to 30 days would provide relief to the operators while not decreasing safety.
Hainan Airlines HNA recommended that the compliance time for the reporting requirement in paragraph k of the proposed AD be extended from 3
to 30 days after the inspection or after the effective date of the proposed AD, or an equivalent date, to alleviate the burden on operators. HNA believes that Boeing already received a large number of inspection reporting results for its root cause analysis over the past year.

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Southwest Airlines SWA asked that the compliance time for the reporting requirement be extended to 10 days.
SWA stated that the 3-day reporting requirement was developed for AD
20192002, Amendment 3919755 84
FR 52754, October 3, 2019. SWA added that the inspection program has matured within Boeing and the Model 737600, 700, 700C, 800, 900, and 900ER
operators, and the reporting requirement of initial inspections can be relaxed from 3 to 10 days to reduce the burden on airline operations for reporting noncrack findings. Additionally, SWA
noted that Boeings airworthiness limitation Document D626A001901
has a requirement to report any crack found during these inspections to Boeing within 10 days.
AIRDO Airlines asked that the reporting requirement be changed from 3 to 7 days, since the statistical data of the inspection results for most of the aging 737NG airplanes has been reported.
Boeing stated that it has been receiving inspection reports over the past year and has accumulated substantial data, and asked that the reporting requirement be extended to 10
days.
Because of the information available from the inspection findings that have already been reported to Boeing, the FAA agrees to extend the reporting requirements in paragraphs h and k of this AD to 10 days, which would reduce the reporting burden on operators and would provide an acceptable level of safety. However, Boeing and the FAA are still relying on those inspection results both to provide repair instructions when cracks are found and to better understand the nature, cause, and extent of the cracking and ultimately develop a terminating action. The FAA, therefore, does not agree to extend the reporting requirement to 30 days.
Request To Provide Credit for Previous Reporting Requirement Boeing and AIRDO Airlines asked that reporting as specified in paragraph k of the proposed AD not be required if an inspection report was previously submitted in accordance with AD 2019
2002 or AD 20192210.
The FAA partially agrees with the commenters request. Although reporting per AD 20192002 alone is not adequate for credit with the reporting requirement specified in paragraph k of this AD, reporting per AD 20192210 meets the reporting requirement specified in paragraph k of this AD. Therefore, the FAA has revised paragraph k of this AD to
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specify that a report submitted as required in paragraph h of this AD is acceptable for compliance with the requirements of paragraph k of this AD.
Request To Clarify Reporting Requirement One commenter asked that the reporting requirement in paragraph k of the proposed AD be clarified. The commenter stated that inspection report example specified in Boeing MultiOperator Message MOMMOM20
044301B R1, dated June 2, 2020, has columns for repetitive inspections. The commenter noted that reporting findings only for the initial inspection is required by the proposed AD, and would like conformation that reporting findings for repetitive inspections thereafter is not required if no cracks are found.
The FAA acknowledges the commenters concern and confirms that paragraph k of this AD requires reporting findings for only the initial inspection, and no reporting is required for any repetitive inspection regardless of the findings.
Effects of Winglets on Accomplishment of the Proposed Actions Aviation Partners Boeing, SWA, and HNA stated that the installation of blended or split scimitar winglets per Supplemental Type Certificate STC
ST00830SE does not affect compliance with the proposed actions.
The FAA agrees with the commenters that STC ST00830SE does not affect the accomplishment of the manufacturers service instructions. Operators of airplanes with these winglets do not need to request a change in product alternative method of compliance AMOC approval as specified in 14 CFR
39.17. The FAA has redesignated paragraph c of the proposed AD as paragraph c1 of this AD, and added paragraph c2 to this AD accordingly.
Request To Use Figures To Accomplish the Refined Inspection AA asked that it be allowed to use the figures for the refined inspection areas in FAA Letter 7821914004. AA stated that the global AMOC provided in FAA
Letter 7821914004 and Boeing MultiOperator Message MOMMOM19
053601B, dated September 30, 2019, is referenced in Boeing Multi-Operator Message MOMMOM20044301B
R1, dated June 2, 2020; however, it is not mentioned in the proposed AD.
The FAA partially agrees with the commenters request. Paragraph n5 of this AD states that AMOCs approved previously for AD 20192210, which
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