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Federal Register / Vol. 86, No. 161 / Tuesday, August 24, 2021 / Proposed Rules while providing operators with certainty regarding the LOV applicable to their airplanes.
The FAA has received a report indicating that cracking is occurring in the frame splice doubler and may occur in the upper frame at the upper frame splice between stringer S13 and S14
on Boeing Model 737300, 400, and 500 airplanes at multiple frame locations. The doubler cracking and possible upper frame cracking at the frame splice between stringer S13 and S14 are the result of fatigue, caused by combined cyclic loading from fuselage pressurization and flight loads. The FAA is issuing this AD to address upper frame cracking common to the frame splice between stringer S13 and S14, which could interact with stringer S14
skin lap splice lower fastener row cracking in lower skin, and result in an uncontrolled decompression of the airplane and loss of structural integrity.
FAAs Determination The FAA is issuing this NPRM after determining that the unsafe condition
described previously is likely to exist or develop on other products of the same type design.
Related Service Information Under 1
CFR Part 51
The FAA reviewed Boeing Alert Requirements Bulletin 73753A1388
RB, dated October 27, 2020. This service information specifies procedures for a general visual inspection GVI of the fuselage frame splices between stringer S13 and S14 station STA 360 to STA
520 and STA 727A to STA 907 for existing repairs, repetitive inspections of the fuselage frame splices between stringer S13 and S14 from STA 360 to STA 520 and STA 727A to STA 907 for cracking, and applicable on-condition actions. On-condition actions include an open hole high frequency eddy current HFEC inspection for cracking at all fastener hole locations where a fastener was removed due to finding a cracked doubler, repair, or replacement.
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 ADDRESSES.
Proposed AD Requirements in This NPRM
This proposed AD would require accomplishing the actions specified in the service information already described except for any differences identified as exceptions in the regulatory text of this proposed AD. For information on the procedures and compliance times, see this service information at https
www.regulations.gov by searching for and locating Docket No. FAA2021
0609.
Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 66
airplanes of U.S. registry. The FAA
estimates the following costs to comply with this proposed AD:

ESTIMATED COSTS
Action
Labor cost
Repetitive Inspections

Up to 267 work-hours $85 per hour = Up to $22,695 inspection cycle.
2 work-hours $85 per hour = $170

GVI

The FAA has received no definitive data on which to base the cost estimates for the on-condition actions specified in this proposed AD.

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Authority for This Rulemaking Title 49 of the United States Code specifies the FAAs authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII:
Aviation Programs, describes in more detail the scope of the Agencys authority.
The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA
with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce.
This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

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Cost per product
Parts cost $0
0

Up to $22,695 per inspection cycle.
$170

Regulatory Findings The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national Government and the States, or on the distribution of power and responsibilities among the various levels of government.
For the reasons discussed above, I
certify this proposed regulation:
1 Is not a significant regulatory action under Executive Order 12866, 2 Would not affect intrastate aviation in Alaska, and 3 Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Cost on U.S.
operators Up to $1,497,870 per inspection cycle.
$11,220.

The Proposed Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
PART 39AIRWORTHINESS
DIRECTIVES
1. The authority citation for part 39
continues to read as follows:

Authority: 49 U.S.C. 106g, 40113, 44701.
39.13

Amended
2. The FAA amends 39.13 by adding the following new airworthiness directive:

The Boeing Company: Docket No. FAA
20210609; Project Identifier AD2021
00274T.
a Comments Due Date The FAA must receive comments on this airworthiness directive AD by October 8, 2021.

List of Subjects in 14 CFR Part 39

b Affected ADs None.

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

c Applicability This AD applies to The Boeing Company Model 737300, 400, and 500 series
PO 00000

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