AD 2017-25-12

This AD is effective January 22, 2018.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of January 22, 2018.

For service information identified in this final rule, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; internet https://www.myboeingfleet.com. You may view this referenced service information at the FAA, Transport Standards Branch, 1601 Lind Avenue SW, Renton, WA. For information on the availability of this material at the FAA, call 425-227-1221. It is also available on the internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2017-0807.

Galib Abumeri, Aerospace Engineer, Airframe Section, FAA, Los Angeles ACO Branch, 3960 Paramount Boulevard, Lakewood, CA 90712-4137; phone: 562-627-5324; fax: 562-627-5210; email: galib.abumeri@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 737-100, -200, -200C, -300, -400, and -500 series airplanes. The NPRM published in the Federal Register on August 30, 2017 (82 FR 41179). The NPRM was prompted by reports of cracking in the webs of the stub beams at certain fuselage stations. These cracks are a result of fatigue caused by cyclical loading from pressurization, wing loads, and landing loads. The NPRM proposed to require repetitive inspections for cracking of the webs of the stub beams at certain fuselage stations, and applicable on-condition actions.

We gave the public the opportunity to participate in developing this final rule. The following presents the comments received on the NPRM and the FAA's response to each comment.

Boeing concurred with the NPRM.

Aviation Partners Boeing stated that accomplishing Supplemental Type Certificate (STC) ST01219SE does not affect the ability to accomplish the actions specified in the NPRM.

We concur with the commenter's request. We have redesignated paragraph (c) of the proposed AD as paragraph (c)(1) and added paragraph (c)(2) to this AD to state that installation of STC ST01219SE does not affect the ability to accomplish the actions required by this AD. Therefore, for airplanes on which STC ST01219SE is installed, a “change in product” alternative methods of compliance (AMOC) approval request is not necessary to comply with the requirements of 14 CFR 39.17.

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this final rule with the changes described previously and minor editorial changes. We have determined that these minor changes:

• Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and

• Do not add any additional burden upon the public than was already proposed in the NPRM.

We also determined that these changes will not increase the economic burden on any operator or increase the scope of this final rule.

Since we issued the NPRM, Boeing received a report indicating that stub beam cracking occurred at station (STA) 685 outside of the inspection areas described in Boeing Alert Service Bulletin 737-53A1364, dated May 24, 2017. The cracking occurred at the upper chord inboard corner radius near the buttock line (BL) 45.5 longitudinal floor beam, and the lower chord outboard flange file radius. The cracks were approximately 1.1 and 4.3 inches long, and could be seen while performing the inspections specified in Boeing Alert Service Bulletin 737-53A1364, dated May 24, 2017. Concurrently with doing the inspections required by paragraphs (g) and (h) of this AD, operators are encouraged to inspect for cracking in the upper chord inboard radius near the BL 45.5 longitudinal floor bean, and the lower chord outboard flange file radius of the STA 685 stub beam. We are considering issuing a separate rulemaking action to address the stub beam cracking at STA 685 that occurred outside of the inspection areas specified in this AD.

We reviewed Boeing Alert Service Bulletin 737-53A1364, dated May 24, 2017. This service information describes procedures for high frequency eddy current and detailed inspections for cracking of the fuselage stub beam webs below the passenger floor at STA 685, STA 695, and STA 706, and applicable on-condition actions. 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.

We estimate that this AD affects 160 airplanes of U.S. registry. We estimate the following costs to comply with this AD:

We have received no definitive data that will enable us to provide cost estimates for the on-condition actions specified in this AD.

Title 49 of the United States Code specifies the FAA's 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 Agency's authority.

We are 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.

This AD is issued in accordance with authority delegated by the Executive Director, Aircraft Certification Service, as authorized by FAA Order 8000.51C. In accordance with that order, issuance of ADs is normally a function of the Compliance and Airworthiness Division, but during this transition period, the Executive Director has delegated the authority to issue ADs applicable to transport category airplanes to the Director of the System Oversight Division.

This AD will not have federalism implications under Executive Order 13132. This AD will 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 that this AD:

(1) Is not a “significant regulatory action” under Executive Order 12866,

(2) Is not a “significant rule” under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979),

(3) Will not affect intrastate aviation in Alaska, and

(4) Will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends 14 CFR part 39 as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by adding the following new airworthiness directive (AD):