Federal Register - November 8, 2021
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Source: Federal Register
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Federal Register / Vol. 86, No. 213 / Monday, November 8, 2021 / Rules and Regulations
Register on June 30, 2021 86 FR 34660.
The NPRM was prompted by cracking found in an inspection area on airplanes not identified in the applicability of AD
20050518. In the NPRM, the FAA
proposed to continue to require repetitive inspections for cracking of the webs of the aft pressure bulkhead at a certain body station, and corrective action if necessary. The NPRM also proposed to require revising the applicability to include additional airplanes, and adding an inspection for existing repairs on the newly added airplanes. The FAA is issuing this AD
to address fatigue cracks in the webs of the aft pressure bulkhead, which could result in rapid decompression of the airplane.
Discussion of Final Airworthiness Directive Comments The FAA received comments from United Airlines and Jack Kendrick, who supported the NPRM without change.
The FAA received additional comments from two commenters, including Boeing and Aviation Partners Boeing. The following presents the comments received on the NPRM and the FAAs response to each comment.
Effects of Winglets on Accomplishment of the Proposed Actions Aviation Partners Boeing 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 commenter that the installation of winglets per STC
ST00830SE does not affect the accomplishment of the manufacturers service instructions. Therefore, the installation of STC ST00830SE does not affect the ability to accomplish the actions required by this AD. 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 Clarify Service Information Description Boeing asked that the FAA clarify the language describing the inspection location and reporting requirements in the Related Service Information Under 1 CFR 51 paragraph in the preamble of the proposed AD. Boeing stated that the language should identify the center dome apex location, and also specify reporting of any cracks found.
The FAA agrees with the commenters request to clarify the inspection location in the Related Service Information section, due to the vast number of web fasteners located around the bulkhead.
The FAA has clarified that language accordingly.
The FAA does not agree with the commenters request to add reporting language to that section, because the manufacturer did not include a reporting requirement for this particular cracking condition in the service information. Therefore, the FAA has not changed this AD in this regard.
Request To Clarify Language in Actions Since AD 20050518 Was Issued Section Boeing requested that the FAA clarify the language in the Actions Since AD
20050518 Was Issued section of the proposed AD. Boeing suggested changing the sentence that begins During the assembly process on line numbers 1167 through 1755, the fasteners, as follows: Fasteners on line numbers 1167 through 1755 in the apex dome region are subjected to clamp-up stresses from the assembly process and fatigue cycles during
fuselage pressurization. Boeing stated that this change is to clarify the meaning of the language used in the proposed AD.
The FAA acknowledges the commenters request and agrees the proposed wording provides clarity.
However, that section is not carried over into this final rule. Therefore, the FAA
has not changed this AD in this regard.
Conclusion The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. 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 Under 1
CFR Part 51
The FAA reviewed Boeing Alert Service Bulletin 73753A1251, Revision 2, dated January 20, 2021. This service information specifies procedures for a general visual inspection for existing repairs, repetitive detailed and high frequency eddy current HFEC
inspections for cracks around the web center dome apex fasteners, repetitive low frequency eddy current LFEC
inspection for cracks around the hidden web lap splice fastener locations, and repair of cracks. 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 744 airplanes of U.S. registry.
The FAA estimates the following costs to comply with this AD:
ESTIMATED COSTS
Action
Labor cost
Detailed, HFEC, and LFEC inspections.
Up to 10 work-hours $85
per hour = Up to $850 per inspection cycle.
1 work-hour $85 per hour =
$85.
lotter on DSK11XQN23PROD with RULES1
General visual inspection 194
airplanes.
The FAA estimates the following costs to do any necessary repairs that
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Jkt 256001
Parts cost
Cost per product $0
0
Up to $850 per inspection cycle.
Up to $632,400 per inspection cycle.
$85
$16,490.
are required based on the results of the inspections. The FAA has no way of
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Cost on U.S. operators
determining the number of aircraft that might need these repairs:
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